an introduction to machine drawing and design by david allan low (whitworth scholar), m. inst. m.e. head master of the people's palace technical schools, london author of 'a text-book on practical solid or descriptive geometry' 'an elementary text-book of applied mechanics' etc. [illustration] _fourth edition_ london longmans, green, and co. and new york: 15 east 16th street 1890 printed by spottiswoode and co., new-street square london preface. it is now generally recognised that the old-fashioned method of teaching machine drawing is very unsatisfactory. in teaching by this method an undimensioned scale drawing, often of a very elaborate description, is placed before the student, who is required to _copy_ it. very often the student succeeds in making a good copy of the drawing placed before him without learning very much about the object represented by it, and this state of matters is sometimes not much improved by the presence of the teacher, who is often simply an art master, knowing nothing about machine design. it is related of one school that a pupil, after making a copy of a particular drawing, had a discussion with his teacher as to whether the object represented was a sewing machine or an electrical machine. evidently the publisher of the drawing example in this case did not adopt the precaution which a backward student used at an examination in machine design: he put on a full title above his drawing, for the information of his examiner. now, if machine drawing is to be of practical use to any one, he must be able to understand the form and arrangement of the parts of a machine from an inspection of suitable drawings of them without seeing the parts themselves. also he ought to be able to make suitable drawings of a machine or parts of a machine from the machine or the parts themselves. in producing this work the author has aimed at placing before young engineers and others, who wish to acquire the skill and knowledge necessary for making the simpler _working drawings_ such as are produced in engineers' drawing offices, a number of good exercises in drawing, sufficient for one session's work, and at the same time a corresponding amount of information on the design of machine details generally. the exercises set are of various kinds. in the first and simplest certain views of some machine detail are given, generally drawn to a small scale, which the student is asked to reproduce _to dimensions marked on these views_, and he is expected to keep to these dimensions, and not to measure anything from the given illustrations. in the second kind of exercise the student is asked to reproduce certain views shown _to dimensions given in words or in tabular form_. in the third kind of exercise the student is required to make, in addition to certain views shown to given dimensions, others which he can only draw correctly if he thoroughly understands the design before him. in the fourth kind of exercise the student is asked to make the necessary working drawings for some part of a machine which has been previously described and illustrated, _the dimensions to be calculated by rules given in the text_. the illustrations for this work are all new, and have been specially prepared by the author from _working drawings_, and he believes that they will be found to represent the best modern practice. as exercises in drawing, those given in this book are not numbered exactly in their order of difficulty, but unless on the recommendation of a teacher, the student should take them up in the order given, omitting the following:--26, 27, 28, 35, 40, 42, 43, 45, 49, 50, 54, 60, 61, as he comes to them, until he has been right through the book; afterwards he should work out those which he omitted on first going over the book. in addition to the exercises given in this work the student should practise making freehand sketches of machine details from actual machines or good models of them. upon these sketches he should put the proper dimensions, got by direct measurement from the machine or model by himself. these sketches should be made in a note-book kept for the purpose, and no opportunity should be lost of inserting a sketch of any design which may be new to the student, always putting on the dimensions if possible. these sketches form excellent examples from which to make working drawings. the student should also note any rules which he may meet with for proportioning machines, taking care, however, in each case to state the source of such information for his future guidance and reference. as machine drawing is simply the application of the principles of descriptive geometry to the representation of machines, the student of the former subject, if he is not already acquainted with the latter, should commence to study it at once. d. a. l. glasgow: _march_ 1887. _preface to the third edition._ to this edition another chapter has been added, containing a number of miscellaneous exercises, which it is hoped will add to the usefulness of the work as a text-book in science classes. the latest examination paper in machine drawing by the science and art department has also been added to the appendix. d. a. l. london: _august_ 1888. contents. page i. introduction 1 ii. riveted joints 6 iii. screws, bolts, and nuts 14 iv. keys 22 v. shafting 24 vi. shaft couplings 25 vii. bearings for shafts 30 viii. pulleys 36 ix. toothed wheels 39 x. cranks and cranked shafts 43 xi. eccentrics 47 xii. connecting rods 49 xiii. cross-heads 56 xiv. pistons 57 xv. stuffing-boxes 63 xvi. valves 68 xvii. materials used in machine construction 76 xviii. miscellaneous exercises 81 appendix a 99 appendix b 102 index 113 an introduction to machine drawing and design. i. introduction. _drawing instruments._--for working the exercises in this book the student should be provided with the following:--a well-seasoned yellow pine _drawing-board_, 24 inches long, 17 inches wide, and 3/8 inch or 1/2 inch thick, provided with cross-bars on the back to give it strength and to prevent warping. a =t= _square_, with a blade 24 inches long attached permanently to the stock, _but not sunk into it_. one 45° and one 60° _set square_. the short edges of the former may be about 6 inches and the short edge of the latter about 5 inches long. a _pair of compasses_ with pen and pencil attachments, and having legs from 5 inches to 6 inches long. a _pair of dividers_, with screw adjustment if possible. a _pair of small steel spring pencil bows_ for drawing small circles, and a _pair of small steel spring pen bows_ for inking in the same. a _drawing pen_ for inking in straight lines. all compasses should have _round points_, and if possible _needle_ points. a piece of india-rubber will also be required, besides two pencils, one marked h or hh and one marked hb or f; the latter to be used for lining in a drawing which is not to be inked in, or for freehand work. pencils for mechanical drawing should be sharpened with a _chisel point_, and those for freehand work with a _round point_. _do not wet the pencil_, as the lines afterwards made with it are very difficult to rub out. drawing-paper for working drawings may be secured to the board by _drawing-pins_, but the paper for finished drawings or drawings upon which there is to be a large amount of colouring should be _stretched_ upon the board. the student should get the best instruments he can afford to buy, and he should rather have a few good instruments than a large box of inferior ones. _drawing-paper._--the names and sizes of the sheets of drawing paper are given in the following table:- inches demy 20 × 15 medium 22 × 17 royal 24 × 19 imperial 30 × 22 atlas 34 × 26 double elephant 40 × 27 antiquarian 52 × 31 the above sizes must not be taken as exact. in practice they will be found to vary in some cases as much as an inch. cartridge-paper is made in sheets of various sizes, and also in rolls. hand-made paper is the best, but it is expensive. good cartridge-paper is quite suitable for ordinary drawings. _centre lines._--drawings of most parts of machines will be found to be symmetrical about certain lines called _centre lines_. these lines should be drawn first with great care. on a pencil drawing centre lines should be thin continuous lines; in this book they are shown thus ----. after drawing the centre line of any part the dimensions of that part must be marked off from the centre line, so as to insure that it really is the centre line of that part: thus in making a drawing of a rivet, such as is shown at (_a_) fig. 1, after drawing the centre line, half the diameter of the rivet would be marked off on each side of that line, in order to determine the lines for the sides of the rivet. _inking._--for inking in drawings the best indian ink should be used, and not common writing ink. common ink does not dry quick enough, and rapidly corrodes the drawing pens. the pen should be filled by means of a brush or a narrow strip of paper, and not by dipping the pen into the ink. in cases where there are straight lines and arcs of circles touching one another _ink in the arcs first_, then the straight lines; in this way it is easier to hide the joints. _colouring._--camel's-hair or sable brushes should be used; the latter are the best, but are much more expensive than the former. the colour should be rubbed down in a dish, and the tint should be light. the mistake which a beginner invariably makes is in having the colour of too dark a tint. first go over the part to be coloured with the brush and _clean_ water for the purpose of damping it. next dry with clean blotting-paper to take off any superfluous water. then take another brush with the colour, and beginning at the top, work from left to right and downwards. if it is necessary to recolour any part let the first coating dry before beginning. engineers have adopted certain colours to represent particular materials; these are given in the following table:-_table showing colours used to represent different materials._ material colour cast iron payne's grey or neutral tint. wrought iron prussian blue. steel purple (mixture of prussian blue and crimson lake). brass gamboge with a little sienna or a very little red added. copper a mixture of crimson lake and gamboge, the former colour predominating. lead light indian ink with a very little indigo added. brickwork crimson lake and burnt sienna. firebrick yellow and vandyke brown. greystones light sepia or pale indian ink, with a little prussian blue added. brown freestone mixture of pale indian ink, burnt sienna, and carmine. soft woods for ground work, pale tint of sienna. hard woods for ground work, pale tint of sienna with a little red added. for graining woods use darker tint with a greater proportion of red. _printing._--a good drawing should have its title printed, a plain style of letter being used for this purpose, such as the following:- [illustration: abcdefghijklmnopqrst uvwxyz 1234567890] [illustration: abcdefghijklmnopqr stuvwxyz 1234567890] the following letters look well _if they are well made_, but they are much more difficult to draw. [illustration: abcdefghijklmnop qrstuvwxyz 1234567890] for remarks on a drawing the following style is most suitable:- [illustration: abcdefghijklmnopqrstuvwxyz] all printing should be done by freehand. _border lines_ are seldom put on engineering drawings. _working drawings._--a good working drawing should be prepared in the following manner. it must first be carefully outlined in pencil and then inked in. after this all parts cut by planes of section should be coloured, the colours used indicating the materials of which the parts are made. parts which are round may also be lightly shaded with the brush and colours to suit the materials. the centre lines are now inked in with _red_ or _blue ink_. the red ink may be prepared by rubbing down the cake of crimson lake, and the blue ink in like manner from the cake of prussian blue. next come the _distance_ or _dimension_ lines, which should be put in with _blue_ or _red ink_, depending on which colour was used for the centre lines. dimension lines and centre lines are best put in of different colour. the arrow-heads at the ends of the dimension lines are now put in with _black ink_, and so are the figures for the dimensions. the arrow-heads and the figures should be made with a common writing pen. the dimensions should be put on neatly. many a good drawing has its appearance spoiled through being slovenly dimensioned. we may here point out the importance of putting the dimensions on a working drawing. if the drawing is not dimensioned, the workman must get his sizes from the drawing by applying his rule or a suitable scale. now this operation takes time, and is very liable to result in error. time is therefore saved, and the chance of error reduced, by marking the sizes in figures. in practice it is not usual to send original drawings from the drawing office to the workshop, but copies only. the copies may be produced by various 'processes,' or they may be tracings drawn by hand. many engineers do not ink in their original drawings, but leave them in pencil; especially is this the case if the drawings are not likely to be much used. _scales._--the best scales are made of ivory, and are twelve inches long. boxwood scales are much cheaper, although not so durable as those made of ivory. if the student does not care to go to the expense of ivory or boxwood scales, he can get paper ones very cheap, which will be quite sufficient for his purpose. the divisions of the scale should be marked down to its edge, so that measurements may be made by applying the scale directly to the drawing. for working such exercises as are in this book the student should be provided with the following scales:- a scale of 1, or 12 inches to a foot. " 1/2 " 6 " " 1/3 " 4 " " 1/4 " 3 " " 1/6 " 2 " a scale of 1 is spoken of as 'full size,' and a scale of 1/2 as 'half size.' engineers in this country state dimensions of machines in feet, inches, and fractions of an inch, the latter being the 1/2, 1/4, 1/8, 1/16, &c. in making calculations it is generally more convenient to use decimal fractions, and then substitute for the results the equivalent fractions in eighths, sixteenths, &c. the following table will be found useful for this purpose:-_decimal equivalents of fractions of an inch._ +----------+--------------------+ | fraction | decimal equivalent | +----------+--------------------+ | 1/32 | .03125 | | 1/16 | .0625 | | 3/32 | .09375 | | 1/8 | .125 | | 5/32 | .15625 | | 3/16 | .1875 | | 7/32 | .21875 | | 1/4 | .25 | | 9/32 | .28125 | | 5/16 | .3125 | | 11/32 | .34375 | | 3/8 | .375 | | 13/32 | .40625 | | 7/16 | .4375 | | 15/32 | .46875 | | 1/2 | .5 | | 17/32 | .53125 | | 9/16 | .5625 | | 19/32 | .59375 | | 5/8 | .625 | | 21/32 | .65625 | | 11/16 | .6875 | | 23/32 | .71875 | | 3/4 | .75 | | 25/32 | .78125 | | 13/16 | .8125 | | 27/32 | .84375 | | 7/8 | .875 | | 29/32 | .90625 | | 15/16 | .9375 | | 31/32 | .96875 | | 1 | 1.0 | +----------+--------------------+ engineers use a single accent (') to denote _feet_, and a double accent (") to denote _inches_. thus 2' 9" reads two feet nine inches. ii. riveted joints. two plates or pieces to be riveted together have holes punched or drilled in them in such a manner that one may be made to overlap the other so that the holes in the one may be opposite the holes in the other. the rivets, which are round bars of iron, or steel, or other metal, are heated to redness and inserted in the holes; the head already formed on the rivet, and called the tail, is then held up, and the point is hammered or pressed so as to form another head. this process of forming the second head on the rivet is known as riveting, and may be done by hand-hammering or by a machine. _forms of rivet heads._--in fig. 1 are shown four different forms of rivet heads: (_a_) is a _snap head_, (_b_) a _conical head_ (_c_) a _pan head_, and (_d_) _a countersunk head_. _proportions of rivet heads._--the diameter of the snap head is about 1.7 times the diameter of the rivet, and its height about .6 of the diameter of the rivet. the conical head has a diameter twice and a height three quarters of the rivet diameter. the greatest diameter of the pan head is about 1.6, and its height .7 of the rivet diameter. the greatest diameter of the countersunk head may be one and a half, and its depth a half of the diameter of the rivet. [illustration: fig. 1.] in fig. 1 at (_a_) and (_b_) are shown geometrical constructions devised by the author for drawing the snap and conical head for any size of rivet, the proportions being nearly the same as those given above. _geometrical construction for proportioning snap heads._--with centre a, and radius equal to half diameter of rivet, describe a circle cutting the centre line of the rivet at b and c. with centre b and radius bc describe the arc cd. make be equal to ad. with centre e and radius ed describe the arc dfh. _construction for conical head._--with centre k, and radius equal to diameter of rivet, describe the semicircle lmn, cutting the side of the rivet at m. with centre m and radius mn describe the arc np to cut the centre line of rivet at p. join pl and pn. when a number of rivets of the same diameter have to be shown on the same drawing the above constructions need only be performed on one rivet. after the point e has been discovered the distance ae may be measured off on all the other rivets, and the arcs corresponding to dfh drawn with radii equal to ed. in like manner the height kp of the conical head may be marked off on all rivets of the same diameter with conical heads. _caulking._--in order to make riveted joints steamor water-tight the edges of the plates and the edges of the heads of the rivets are burred down by a blunt chisel or caulking tool as shown at q and r. [illustration: fig. 2.] [illustration: fig. 3.] exercise 1: _forms of rivets._--draw, full size, the rivets and rivet heads shown in fig. 1. the diameter of the rivet in each case to be 1-1/8 inches, and the thickness of the plates 7/8 inch. exercise 2: _single riveted lap joint._--draw, full size, the plan and sectional elevation of the _single riveted lap joint_ shown in fig. 2. _table showing the proportions of single riveted lap joints for various thicknesses of plates._ (_plates and rivets wrought iron._) +--------------+-------------+----------+--------------+ | thickness of | diameter of | pitch of | width of lap | | plates | rivets | rivets | | +--------------+-------------+----------+--------------+ | 1/4 | 9/16 | 1-5/8 | 1-3/4 | | 5/16 | 5/8 | 1-3/4 | 2 | | 3/8 | 11/16 | 1-7/8 | 2-1/4 | | 7/16 | 3/4 | 2 | 2-1/2 | | 1/2 | 13/16 | 2-1/8 | 2-3/4 | | 9/16 | 7/8 | 2-1/4 | 2-7/8 | | 5/8 | 15/16 | 2-5/16 | 3 | | 11/16 | 1 | 2-3/8 | 3-1/8 | | 3/4 | 1-1/16 | 2-1/2 | 3-1/4 | +------------------------------------------------------+ all the dimensions are in inches. [illustration: fig. 4.] exercise 3.--draw, half size, a plan and section of a single riveted lap joint for plates 3/4" thick to the dimensions given in the above table. exercise 4: _double riveted lap joint._--draw, full size, the two views of the _double riveted lap joint_ shown in fig. 3. _table showing the proportions of double riveted lap joints for various thicknesses of plates._ (_plates and rivets wrought iron._) +-----------+-------------+----------+------------------+----------+ | thickness | diameter of | pitch of | distance between | width of | | of plates | rivets | rivets | rows of rivets | lap | +-----------+-------------+----------+------------------+----------+ | 3/8 | 11/16 | 2-1/2 | 1-1/8 | 3-1/2 | | 7/16 | 3/4 | 2-5/8 | 1-1/4 | 3-3/4 | | 1/2 | 13/16 | 2-3/4 | 1-3/8 | 4 | | 9/16 | 7/8 | 2-7/8 | 1-7/16 | 4-1/4 | | 5/8 | 15/16 | 3 | 1-9/16 | 4-1/2 | | 11/16 | 1 | 3-1/8 | 1-3/4 | 4-3/4 | | 3/4 | 1-1/16 | 3-1/4 | 1-7/8 | 5 | | 13/16 | 1-1/16 | 3-3/8 | 1-7/8 | 5 | | 7/8 | 1-1/8 | 3-1/2 | 1-15/16 | 5-1/4 | | 15/16 | 1-1/8 | 3-5/8 | 1-15/16 | 5-1/4 | | 1 | 1-3/16 | 3-3/4 | 2 | 5-1/2 | +-----------+-------------+----------+------------------+----------+ [illustration: fig. 5.] exercise 5.--draw, half size, a plan and section of a double riveted lap joint for plates 7/8 inch thick to the dimensions given in the above table. exercise 6: _single riveted butt joints._--in fig. 4 are shown _single riveted butt joints_. one of the sectional views shows a butt joint with one _cover plate_ or _butt strap_; the other sectional view shows the same joint with two cover plates; the third view is a plan of both arrangements. draw all these views full size. exercise 7.--fig. 5 shows a plan and sectional elevation of the connection of three plates together, which are in the same plane, by means of single riveted butt joints and single cover plates. the butt straps where they overlap are forged so as to fit one another as shown, and thus form a close joint. draw these views to the scale of 6 inches to a foot. the plates are 1/2 inch thick and the butt straps 9/16 inch thick. all other dimensions must be deduced from the table for single riveted lap joints. exercise 8.--the connection of three plates by single riveted lap joints is shown in fig. 6. to make the joint close one plate has a portion of its edge thinned out, and the plate above it is set up at this part so as to lie close to the former. draw the three views shown in fig. 6 to the same scale as the last exercise. the plates are 7/16 inch thick. all other dimensions to be obtained from table for single riveted lap joints. exercise 9: _corner of wrought-iron tank._--this exercise is to illustrate the connection of plates which are at right angles to one another by means of _angle irons_. fig. 7 is a plan and elevation of the corner of a wrought-iron tank. the sides of the tank are riveted to a vertical angle iron, the cross section of which is clearly shown in the plan. another angle iron of the same dimensions is used in the same way to connect the sides with the bottom. the sides do not come quite up to the corner of the vertical angle iron, excepting at the bottom where the horizontal angle iron comes in. at this point the vertical plates meet one another, and the edge formed is rounded over to fit the interior of the bend of the horizontal angle iron so as to make the joint tight. draw half size. the dimensions are as follows: angle irons 2-1/2 inches × 2-1/2 inches × 3/8 inch; plates 3/8 inch thick; rivets 11/16 inch diameter and 2 inches pitch. exercise 10: _gusset stay._--in order that the flat ends of a steam boiler may not be bulged out by the pressure of the steam they are strengthened by means of stays. one form of boiler stay, called a 'gusset stay,' is shown in fig. 8. this stay consists of a strip of wrought-iron plate which passes in a diagonal direction from the flat end of the boiler to the cylindrical shell. one end of this plate is placed between and riveted to two angle irons which are riveted to the shell of the boiler. a similar arrangement connects the other end of the stay plate to the flat end of the boiler. in this example the stay or gusset plate is 3/4 of an inch thick; the angle irons are 4 inches broad and 1/2 inch thick. the rivets are 1 inch in diameter. the same figure also illustrates the most common method of connecting the ends of a boiler to the shell. the end plates are _flanged_ or bent over at right angles and riveted to the shell as shown. the radius of the inside curve at the angle of the flange is 1-1/4 inches. draw this example to a scale of 3 inches to 1 foot. [illustration: fig. 6.] [illustration: fig. 7.] [illustration: fig. 8.] iii. screws, bolts, and nuts. _screw threads._--the various forms of screw threads used in machine construction are shown in fig. 9. the _whitworth_ =v= thread is shown at (_a_). this is the standard form of triangular thread used in this country. the angle between the sides of the =v= is 55°, and one-sixth of the total depth is rounded off both at the top and bottom. at (_b_) is shown the _sellers_ =v= thread, which is the standard triangular thread used by engineers in america. in this form of thread the angle between the sides of the =v= is 60°, and one-eighth of the total depth is cut square off at the top and bottom. the _square_ thread is shown at (_c_). this form is principally used for transmitting motion. [illustration: fig. 9.] comparing the triangular and square threads, the former is the stronger of the two; but owing to the normal pressure on the =v= thread being inclined to the axis of the screw, that pressure must be greater than the pressure which is being transmitted by the screw; and therefore, seeing that the normal pressure on the square thread is parallel, and therefore equal to the pressure transmitted in the direction of the axis of the screw, the friction of the =v= thread must be greater than the friction of the square thread. in the case of the triangular thread there is also a tendency of the pressure to burst the nut. the _buttress_ thread shown at (_e_) is designed to combine the advantages of the =v= and square threads, but it only has these advantages when the pressure is transmitted in one direction; if the direction of the pressure be reversed, the friction and bursting action on the nut are even greater than with the =v= thread, because of the greater inclination of the slant side of the buttress thread. the angles of the square thread are frequently rounded to a greater or less extent to render them less easily damaged. if this rounding is carried to excess we get the _knuckle_ thread shown at (_d_). the rounding of the angles increases both the strength and the friction. exercise 11: _forms of screw threads._--draw to a scale of three times full size the sections of screw threads as shown in fig. 9. the pitch for the whitworth, sellers, and buttress threads to be 3/8 inch, and the pitch of the square and knuckle threads to be 1/2 inch. _dimensions of whitworth screws._ +-----------------------------------+ | diameter | number | diameter | | of screw | of threads | at bottom | | | per inch | of thread | +----------+------------+-----------+ | 1/8 | 40 | .093 | | 3/16 | 24 | .134 | | 1/4 | 20 | .186 | | 5/16 | 18 | .241 | | 3/8 | 16 | .295 | | 7/16 | 14 | .346 | | 1/2 | 12 | .393 | | 5/8 | 11 | .508 | | 3/4 | 10 | .622 | | 7/8 | 9 | .733 | | 1 | 8 | .840 | | 1-1/8 | 7 | .942 | | 1-1/4 | 7 | 1.067 | | 1-3/8 | 6 | 1.162 | | 1-1/2 | 6 | 1.286 | | 1-5/8 | 5 | 1.369 | | 1-3/4 | 5 | 1.494 | | 1-7/8 | 4-1/2 | 1.590 | | 2 | 4-1/2 | 1.715 | | 2-1/4 | 4 | 1.930 | | 2-1/2 | 4 | 2.180 | | 2-3/4 | 3-1/2 | 2.384 | | 3 | 3-1/2 | 2.634 | | 3-1/4 | 3-1/4 | 2.856 | | 3-1/2 | 3-1/4 | 3.106 | | 3-3/4 | 3 | 3.323 | | 4 | 3 | 3.573 | | 4-1/4 | 2-7/8 | 3.805 | | 4-1/2 | 2-7/8 | 4.055 | | 4-3/4 | 2-3/4 | 4.284 | | 5 | 2-3/4 | 4.534 | | 5-1/4 | 2-5/8 | 4.762 | | 5-1/2 | 2-5/8 | 5.012 | | 5-3/4 | 2-1/2 | 5.238 | | 6 | 2-1/2 | 5.488 | +-----------------------------------+ _gas threads_[1] (_whitworth standard_). [1] used for wrought-iron and brass tubes. +-------------------------------------------------------------+ | diameter of screw | 1/8 | 1/4 | 3/8 | 1/2 | 5/8 | 3/4 | 1 | +-------------------+-----+-----+-----+-----+-----+-----+----- | number of threads | | | | | | | | | per inch | 28 | 19 | 19 | 14 | 14 | 14 | 11 | +-------------------------------------------------------------+ +-------------------------------------------------+ | diameter of screw | 1-1/4 | 1-1/2 | 1-3/4 | 2 | +-------------------+-------+-------+-------+-----+ | number of threads | | | | | | per inch | 11 | 11 | 11 | 11 | +-------------------------------------------------+ _representation of screws._--the correct method of representing screw threads involves considerable trouble, and is seldom adopted by engineers for working drawings. for an explanation of the method see the author's text-book on practical solid geometry, part ii., problem 134. a method very often adopted on working drawings is shown in fig. 15; here the thin lines represent the points, and the thick lines the roots of the threads. at fig. 16 is shown a more complete method. the simplest method is illustrated by figs. 10, 11, 13, and 14. here dotted lines are drawn parallel to the axis of the screw as far as it extends, and at a distance from one another equal to the diameter of the screw at the bottom of the thread. [illustration: fig. 10.] [illustration: fig. 11.] _forms of nuts._--the most common form of nut is the hexagonal shown in figs. 10, 13, 14, 15, and 16; next to this comes the square nut shown in fig. 11. the method of drawing these nuts will be understood by reference to the figures; the small circles indicate the centres, and the inclined lines passing through them the radii of the curves which represent the chamfered or bevelled edge of the nut. in all the figures but the first the chamfer is just sufficient to touch the middle points of the sides, and in these cases the drawing of the nut is simpler. [illustration: fig. 12.] [illustration: fig. 13.] [illustration: fig. 14.] _forms of bolts._--at (_a_), fig. 12, is shown a bolt with a square head and a square neck. if this form of bolt is passed through a square hole the square neck prevents the bolt from turning when the nut is being screwed up. instead of a square neck a snug may be used for the same purpose, as shown on the cup-headed bolt at (_b_). the snug fits into a short groove cut in the side of the hole through which the bolt passes. at (_a_) the diagonal lines are used to distinguish the flat side of the neck from the round part of the bolt above it. at (_c_) is shown a tee-headed bolt, and at (_d_) an eye-bolt. fig. 13 represents a hook bolt. a bolt with a countersunk head is shown in fig. 11. if the countersunk head be lengthened so as to take up the whole of the unscrewed part of the bolt, we get the taper bolt shown in fig. 14, which is often used in the couplings of the screw shafts of steamships. the taper bolt has the advantage of having no projecting head, and it may also be made a tight fit in the hole with less trouble than a parallel bolt. bolts may also have hexagonal heads. [illustration: fig. 15] [illustration: fig. 16] _studs_, or _stud bolts_, are shown in figs. 15 and 16; that in fig. 15 is a _plain stud_, while that in fig. 16 has an intermediate collar forged upon it, and is therefore called a _collared stud_. _proportions of nuts and bolt-heads._--in the hexagonal nut the diameter d across the flats is 1-1/2_d_ + 1/8, where _d_ is the diameter of the bolt. the same rule gives the width of a square nut across the flats. a rule very commonly used in making drawings of hexagonal nuts is to make the diameter d, across the angles equal to 2_d_. h, the height of the nut, is equal to the diameter of the bolt. in square and hexagonal headed bolts the height of the head varies from _d_ to 2/3_d_; the other dimensions are the same as for the corresponding nuts. _washers_ are flat, circular, wrought-iron plates, having holes in their centres of the same diameter as the bolts on which they are used. the object of the washer is to give a smooth bearing surface for the nut to turn upon, and it is used when the surfaces of the pieces to be connected are rough, or when the bolt passes through a hole larger than itself, as shown in fig. 10. the diameter of the washer is a little more than the diameter of the nut across the angles, and its thickness about 1/8 of the diameter of the bolt. exercise 12.--draw, full size, the views shown in fig. 10 of an hexagonal nut and washer for a bolt 1-1/4 inches in diameter. the bolt passes through a hole 1-3/4 × 1-1/4. all the dimensions are to be calculated from the rules which have just been given. exercise 13.--draw, full size, the plan and elevation of the square nut and bolt with countersunk head shown in fig. 11, to the dimensions given. exercise 14.--draw, full size, the elevation of the hook bolt with hexagonal nut shown in fig. 13 to the dimensions given, and show also a plan. exercise 15.--draw, to a scale of 4 inches to a foot, the conical bolt for a marine shaft coupling shown in fig. 14. all the parts are of wrought iron. exercise 16.--fig. 15 is a section of the mouth of a small steam-engine cylinder, showing how the cover is attached; draw this full size. exercise 17.--fig. 16 shows the central portion of the india-rubber disc valve which is described on page 68. a is the central boss of the grating, into which is screwed the stud b, upon which is forged the collar c. the upper part of the stud is screwed, and carries the guard d and an hexagonal nut e. f is the india-rubber. the grating and guard are of brass. the stud and nut are of wrought iron. draw full size the view shown. _lock nuts._--in order that a nut may turn freely upon a bolt, there is always a very small clearance space between the threads of the nut and those of the bolt. this clearance is shown exaggerated at (_a_), fig. 17, where a is a portion of a bolt within a nut b. suppose that the bolt is stretched by a force w. when the nut b is screwed up, the upper surfaces of the projecting threads of the nut will press on the under surfaces of the threads of the bolt with a force p equal and opposite to w, as shown at (_b_), fig. 17. when in this condition the nut has no tendency to slacken back, because of the friction due to the pressure on the nut. now suppose that the tension w on the bolt is momentarily diminished, then the friction which opposes the turning of the nut may be so much diminished that a vibration may cause it to slacken back through a small angle. if this is repeated a great many times the nut may slacken back so far as to become useless. [illustration: fig. 17.] [illustration: fig. 18.] a very common arrangement for locking a nut is shown at (_a_), fig. 18. c is an ordinary nut, and b one having half the thickness of c. b is first screwed up tight so as to act on the bolt, as shown at (_b_), fig. 17. c is then screwed on top of b. when c is almost as tight as it can be made, it is held by one spanner, while b is turned back through a small angle with another. the action of the nuts upon the bolt and upon one another is now as shown at (_b_), fig. 18. it will be seen that the nuts are wedged tight on to the bolt, and that this action is independent of the tension w in the bolt. the nuts will, therefore, remain tight after the tension in the bolt is removed. it is evident that if the nuts are screwed up in the manner explained, the outer nut c will carry the whole load on the bolt; hence c should be the thicker of the two nuts. in practice, the thin nut, called the lock nut, is often placed on the outside, for the reason that ordinary spanners are too thick to act on the thin nut when placed under the other. another very common arrangement for locking a nut is shown in fig. 19. a is the bolt and b the nut, the lower part of which is turned circular. a groove c is also turned on the nut at this part. the circular part of the nut fits into a circular recess in one of the parts connected by the bolt. through this part passes a set screw d, the point of which can be made to press on the nut at the bottom of the groove c. d is turned back when the nut b is being moved, and when b is tightened up, the set screw is screwed up so as to press hard on the bottom of the groove c. the nut b is thus prevented from slackening back. the screw thread is turned off the set screw at the point where it enters the groove on the nut. [illustration: fig. 19] the use of the groove for receiving the point of the set screw is this: the point of the set screw indents the nut and raises a bur which would interfere with the free turning of the nut in the recess if the bur was not at the bottom of a groove. additional security is obtained by drilling a hole through the point of the bolt, and fitting it with a split pin e. locking arrangements for nuts are exceedingly numerous, and many of them are very ingenious, but want of space prevents us describing them. we may point out, however, that many very good locking arrangements have the defect of only locking the nut at certain points of a revolution, say at every 30°. it will be noticed that the two arrangements which we have described are not open to this objection. exercise 18.--draw, full size, a plan, front elevation, and side elevation of the arrangement of nuts shown in fig. 18, for a bolt 7/8 inch diameter. exercise 19.--draw the plan and elevation of the nut and locking arrangement shown in fig. 19. make also an elevation looking in the direction of the arrow. scale 6 inches to a foot. iv. keys. _keys_ are wedges, generally rectangular in section, but sometimes circular; they are made of wrought iron or steel, and are used for securing wheels, pulleys, cranks, &c., to shafts. [illustration: fig. 20.] various sections of keys are shown in fig. 20. at (_a_) is the _hollow_ or _saddle key_. with this form of key it is not necessary to cut the shaft in any way, but its holding power is small, and it is therefore only used for light work. at (_b_) is the _key on a flat_, sometimes called a _flat key_. the holding power of this key is much greater than that of the saddle key. at (_c_) is the _sunk key_, a very secure and very common form. the part of the shaft upon which a key rests is called the _key bed_ or _key way_, and the recess in the boss of the wheel or pulley into which the key fits is called the _key way_; both are also called _key seats_. with saddle, flat, and sunk keys the key bed is parallel to the axis of the shaft; but the key way is deeper at one end than the other to accommodate the taper of the key. the sides of the key are parallel. the _round key_ or taper pin shown at (_d_) is in general only used for wheels or cranks which have been previously shrunk on to their shafts or forced on by great pressure. after the wheel or crank has been shrunk on, a hole is drilled, half into the shaft and half into the wheel or crank, to receive the pin. when the point of a key is inaccessible the other end is provided with a _gib head_ as shown at (_e_), to enable the key to be withdrawn. a _sliding_ or _feather key_ secures a piece to a shaft so far as to prevent the one from rotating without the other, but allows of relative motion in the direction of the axis of the shaft. this form of key has no taper, and it is secured to the piece carried by the shaft, but is made a _sliding fit_ in the key way of the shaft. in one form of feather key the part within the piece carried by the shaft is dovetailed as shown at (_f_). in another form the key has a round projecting pin forged upon it, which enters a corresponding hole as shown at (_g_). the feather key may also be secured to the piece carried by the shaft by means of one or more screws as shown at (_h_). the key way in the shaft is made long enough to permit of the necessary sliding motion. _cone keys._--these are sometimes fitted to pulleys, and are shown in fig. 32, page 38. in this case the eye of the pulley is tapered and is larger than the shaft. the space between the shaft and the boss of the pulley is filled with three _saddle_ or _cone keys_. these keys are made of cast iron and are all cast together, and before being divided the casting is bored to fit the shaft and turned to fit the eye of the pulley. by this arrangement of keys the same pulley may be fixed on shafts of different diameters by using keys of different thicknesses; also the pulley may be bored out large enough to pass over any boss which may be forged on the shaft. _proportions of keys._--the following rules are taken from unwin's 'machine design,' pp. 142-43. diameter of eye of wheel, or boss of shaft = _d_. width of key = 3/4_d_ + 1/8. mean thickness of sunk key = 1/8_d_ + 1/8. " key on flat = 1/16_d_ + 1/16. the following table gives dimensions agreeing with average practice. _dimensions of keys._ d = diameter of shaft. b = breadth of key. t = thickness of sunk key. t_{1} = thickness of flat key, also = thickness of saddle key. taper of key 1/8 inch per foot of length, _i.e._ 1 in 96. +---------------------------------------------------------------+ | d | 3/4 | 1 | 1-1/4 | 1-1/2 | 1-3/4 | 2 | 2-1/4 | 2-1/2 | +-----+-----+-----+-------+-------+-------+-----+-------+-------+ | b | 5/16| 3/8 | 7/16 | 1/2 | 9/16 | 5/8 | 11/16 | 11/16 | | t | 1/4 | 1/4 | 1/4 | 5/16 | 5/16 | 5/16| 3/8 | 3/8 | |t_{1}| 3/16| 3/16| 3/16 | 3/16 | 1/4 | 1/4 | 1/4 | 5/16 | +---------------------------------------------------------------+ +-------------------------------------------------------------------+ | d | 2-3/4 | 3 | 3-1/2 | 4 | 4-1/2 | 5 | 5-1/2 | 6 | +-----+-------+-----+-------+-------+-------+-------+-------+-------+ | b | 3/4 | 7/8 | 1 | 1-1/8 | 1-1/4 | 1-3/8 | 1-1/2 | 1-5/8 | | t | 3/8 | 7/16| 1/2 | 1/2 | 9/16 | 5/8 | 11/16 | 3/4 | |t_{1}| 5/16 | 5/16| 3/8 | 7/16 | 1/2 | 1/2 | 9/16 | 5/8 | +-------------------------------------------------------------------+ +-------------------------------------------------------+ | d | 7 | 8 | 9 | 10 | 11 | 12 | +-----+-------+-------+-------+--------+--------+-------+ | b | 1-7/8 | 2-1/8 | 2-3/8 | 2-5/8 | 2-7/8 | 3-1/8 | | t | 13/16 | 15/16 | 1 | 1-1/16 | 1-3/16 | 1-1/4 | |t_{1}| 11/16 | 3/4 | 7/8 | 15/16 | 1-1/16 | 1-1/8 | +-------------------------------------------------------+ v. shafting. shafting is nearly always cylindrical and made of wrought iron or steel. cast iron is rarely used for shafting. _axles_ are shafts which are subjected to bending without twisting. the parts of a shaft or axle which rest upon the bearings or supports are called _journals_, _pivots_, or _collars_. in journals the supporting pressure is at right angles to the axis of the shaft, while in pivots and collars the pressure is parallel to that axis. shafts may be solid or hollow. hollow shafts are stronger than solid shafts for the same weight of material. thus a hollow shaft having an external diameter of 10-1/4 inches and an internal diameter of 7 inches would have about the same weight as a solid shaft of the same material 7-1/2 inches in diameter, but the former would have about double the strength of the latter. hollow shafts are also stiffer and yield less to bending action than solid shafts, which in some cases, as in propeller shafts, is an objection. vi. shaft couplings. for convenience of making and handling, shafts used for transmitting power are generally made in lengths not exceeding 30 feet. these lengths are connected by couplings, of which we give several examples. [illustration: figs. 21 and 22.] _solid_, _box_, or _muff couplings._--one form of box coupling is shown in fig. 21. here the ends of the shafts to be connected butt against one another, meeting at the centre of the box, which is made of cast iron. the shafts are made to rotate as one by being secured to the box by two wrought-iron or steel keys, both driven from the same end of the box. a clearance space is left between the head of the forward key and the point of the hind one, to facilitate the driving of them out, as then only one key needs to be started at a time. sometimes a single key the whole length of the box is used, in which case it is necessary that the key ways in the shafts be of exactly the same depth. the half-lap coupling, introduced by sir william fairbairn, is shown in fig. 22. in this form of box coupling the ends of the shafts overlap within the box. it is evident that one shaft cannot rotate without the other as long as the box remains over the lap. to keep the box in its place it is fitted with a saddle key. it will be noticed that the lap joint is sloped in such a way as to prevent the two lengths of shaft from being pulled asunder by forces acting in the direction of their length. half-lap couplings are not used for shafts above 5 inches in diameter. it may here be pointed out that the half-lap coupling is expensive to make, and is now not much used. as shafts are weakened by cutting key ways in them, very often the ends which carry couplings are enlarged in diameter, as shown in fig. 21, by an amount equal to the thickness of the key. an objection to this enlargement is that wheels and pulleys require either that their bosses be bored out large enough to pass over it, or that they be split into halves, which are bolted together after being placed on the shaft. _dimensions of box couplings._ d = diameter of shaft. t = thickness of metal in box. l = length of box for butt coupling. l_{1} = length of box for lap coupling. _l_ = length of lap. d_{1} = diameter of shaft at lap. +---------------------------------------------------------------+ | d | 1-1/2 | 2 | 2-1/2 | 3 | 3-1/2 | 4 | +-------+--------+--------+---------+-------+----------+--------+ | t | 1-1/8 | 1-5/16 | 1-1/2 | 1-3/4 | 1-15/16 | 2-1/8 | | l | 5-3/4 | 7 | 8-1/4 | 9-1/2 | 10-3/4 | 12 | | l_{1} | 4-1/8 | 5-1/4 | 6-3/8 | 7-1/2 | 8-5/8 | 9-3/4 | | _l_ | 1-7/16 | 1-7/8 | 2-5/16 | 2-3/4 | 3-3/16 | 3-5/8 | | d_{2} | 2-5/16 | 3 | 3-11/16 | 4-3/8 | 5-1/16 | 5-3/4 | +---------------------------------------------------------------+ +----------------------------------------------+ | d | 4-1/2 | 5 | 5-1/2 | 6 | +-------+---------+--------+--------+----------+ | t | 2-5/16 | 2-1/2 | 2-3/4 | 2-15/16 | | l | 13-1/4 | 14-1/2 | 15-3/4 | 17 | | l_{1} | 10-7/8 | 12 | - | - | | _l_ | 4-1/16 | 4-1/2 | - | - | | d_{2} | 6-7/16 | 7-1/8 | - | - | +----------------------------------------------+ slope of lap 1 in 12. exercise 20: _solid butt coupling._--from the above table of dimensions make a longitudinal and a transverse section of a solid butt coupling for a shaft 2-1/2 inches in diameter. scale 6 inches to a foot. exercise 21: _fairbairn's half-lap coupling._--make the same views as in the last exercise of a half-lap coupling for a 3-inch shaft to the dimensions in the above table. scale 6 inches to a foot. _flange couplings._--the form of coupling used for the shafts of marine engines is shown in fig. 23. the ends of the different lengths of shaft have flanges forged on them, which are turned along with the shaft. these flanges butt against one another, and are connected by bolts. these bolts may be parallel or tapered; generally they are tapered. a parallel bolt must have a head, but a tapered bolt will act without one. in fig. 23 the bolts are tapered, and also provided with heads. in fig. 14, page 17, is shown a tapered bolt without a head. the variation of diameter in tapered bolts is 3/8 of an inch per foot of length. [illustration: fig. 23.] sometimes a projection is formed on the centre of one flange which fits into a corresponding recess in the centre of the other, for the purpose of ensuring the shafts being in line. occasionally a cross-key is fitted in between the flanges, being sunk half into each, for the purpose of diminishing the shearing action on the bolts. exercise 22: _marine coupling._--draw the elevation and section of the coupling shown in fig. 23; also an elevation looking in the direction of the arrow. scale 3 inches to a foot. the following table gives the dimensions of a few marine couplings taken from actual practice. _examples of marine couplings._ +--------------------------------------------------------------------+ | diameter of shaft |2-3/8 | 9-3/4 | 12-7/8 |16-1/2 | 22-1/2 | 23 | +--------------------+------+-------+--------+-------+--------+------+ |diameter of flange | 6 | 19 | 24 | 32 | 35 | 38 | |thickness of flange | 1 | 2-3/4 | 3-1/8 | 4-1/4 | 6 | 5 | |diameter of bolts | 3/4 | 2-3/4 | 2-11/16| 3-1/2 | 4-1/4 | 4-1/4| |number of bolts | 3 | 6 | 6 | 8 | 9 | 8 | |diameter of bolt | | | | | | | | circle |4-1/8 | 14-1/8|18-13/16| 25 | 28-3/4 |30-3/8| +--------------------------------------------------------------------+ all the above dimensions are in inches. exercise 23.--select one of the couplings from the above table, and make the necessary working drawings for it to a suitable scale. the cast-iron flange coupling is shown in fig. 24. in this kind of coupling a cast-iron centre or boss provided with a flange is secured to the end of each shaft by a sunk key driven from the face of the flange. these flanges are then connected by bolts and nuts as in the marine coupling. to ensure the shafts being in line the end of one projects into the flange of the other. in order that the face of each flange may be exactly perpendicular to the axis of the shaft they should be 'faced' in the lathe, after being keyed on to the shaft. if the coupling is in an exposed position, where the nuts and bolt-heads would be liable to catch the clothes of workmen or an idle driving band which might come in the way, the flanges should be made thicker, and be provided with recesses for the nuts and bolt-heads. [illustration: fig. 24.] _dimensions of cast-iron flange couplings._ +--------------------------------------------------------------------+ | |diameter| | |depth | |diameter|diameter| |diameter| of |thickness|diameter| at |number| of | of bolt| |of shaft| flange |of flange| of boss| boss | of | bolts | circle | | d | f | t | b | l | bolts| d | c | +--------|--------|---------|--------|------|------|--------|--------+ | 1-1/2 | 7-1/4 | 7/8 | 3-1/2 |2-5/8 | 3 |5/8 | 5-1/2 | | 2 | 8-7/8 | 1-1/16 | 4-3/8 |3-3/16| 4 | 3/4| 6-3/4 | | 2-1/2 | 10-5/8 | 1-1/4 | 5-5/16 |3-3/4 | 4 |7/8 | 8-1/8 | | 3 | 12-3/8 | 1-7/16 | 6-1/4 |4-5/16| 4 | 1 | 9-1/2 | | 3-1/2 | 13-1/8 | 1-5/8 | 7-1/8 |4-7/8 | 4 | 1 |10-5/16 | | 4 | 14 | 1-3/4 | 8 |5-7/16| 6 | 1 |11-1/4 | | 4-1/2 | 15-5/8 | 2 | 8-7/8 |6 | 6 |1-1/8 |12-1/2 | | 5 | 17-3/8 | 2-1/8 | 9-13/16|6-5/8 | 6 | 1-1/4|13-13/16| | 5-1/2 | 18-1/4 | 2-5/16 |10-3/4 |7-1/4 | 6 |1-1/4 |14-3/4 | | 6 | 19-7/8 | 2-1/2 |11-5/8 |7-3/4 | 6 | 1-3/8| 16 | +--------------------------------------------------------------------+ the projection of the shaft _p_ varies from 1/4 inch in the small shafts to 1/2 inch in the large ones. exercise 24: _cast-iron flange coupling._--draw the views shown in fig. 24 of a cast-iron flange coupling, for a shaft 4-1/2 inches in diameter, to the dimensions given in the above table. scale 4 inches to a foot. vii. bearings for shafts. an example of a very simple form of bearing is shown in fig. 25, which represents a brake shaft carrier of a locomotive tender. the bearing in this example is made of cast iron and in one piece. through the oval-shaped flange two bolts pass for attaching the bearing to the wrought-iron framing of the tender. with this form of bearing there is no adjustment for wear, so that when it becomes worn it must be renewed. [illustration: fig. 25.] exercise 25: _brake shaft carrier._--draw the elevation and sectional plan of the bearing shown in fig. 25. draw also a vertical section through the axis. the latter view to be projected from the first elevation. scale 6 inches to a foot. _pillow block_, _plummer block_, or _pedestal_.--the ordinary form of plummer block is represented in fig. 26. a is the block proper, b the sole through which pass the holding-down bolts. c is the cap. between the block and the cap is the brass bush, which is in halves, called _brasses_ or _steps_. the bed for the steps in this example is cylindrical, and is prepared by the easy process of boring. the steps are not supported throughout their whole length, but at their ends only where fitting strips are provided as shown. as the wear on a step is generally greatest at the bottom, it is made thicker there than at the sides, except where the fitting strips come in. to prevent the steps turning within the block they are generally furnished with lugs, which enter corresponding recesses in the block and cover. [illustration: fig. 26] in the block illustrated the journal is lubricated by a _needle lubricator_; this consists of an inverted glass bottle fitted with a wood stopper, through a hole in which passes a piece of wire, which has one end in the oil within the bottle, and the other resting on the journal of the shaft. the wire or needle does not fill the hole in the stopper, but if the needle is kept from vibrating the oil does not escape owing to capillary attraction. when, however, the shaft rotates, the needle begins to vibrate, and the oil runs down slowly on to the journal; oil is therefore only used when the shaft is running. exercise 26: _pillow block for a four-inch shaft._--draw the views shown of this block in fig. 26. make also separate drawings, full size, of one of the steps. scale 6 inches to a foot. _proportions of pillow blocks._--the following rules may be used for proportioning pillow blocks for shafts up to 8 inches diameter. it should be remembered that the proportions used by different makers vary considerably, but the following rules represent average practice. diameter of journal = _d_. length of journal = _l_. height to centre = 1.05_d_ + .5. length of base = 3.6_d_ + 5. width of base = .8_l_. " block = .7_l_. thickness of base = .3_d_ + .3. " cap = .3_d_ + .4. diameter of bolts = .25_d_ + .25. distance between centres of cap bolts = 1.6_d_ + 1.5. " " base bolts = 2.7_d_ + 4.2. thickness of step at bottom = _t_ = .09_d_ + .15. " " sides = 3/4 _t_. the length of the journal varies very much in different cases, and depends upon the speed of the shaft, the load which it carries, the workmanship of the journal and bearing, and the method of lubrication. for ordinary shafting one rule is to make _l_ = _d_ + 1. some makers use the rule _l_ = 1.5_d_; others make _l_ = 2_d_. exercise 27: _design for pillow block._--make the necessary working drawings for a pillow block for a shaft 5 inches in diameter, and having a journal 7 inches long. [illustration: fig. 27.] _brackets._--when a pillow block has to be fixed to a wall or column a bracket such as that shown in figs. 27 and 28 may be used. the pillow block rests between the _joggles_ a a, and is bolted down to the bracket and secured in addition with keys at the ends of the base of the block, in the same manner as is shown, for the attachment of the bracket to the column. exercise 28: _pillar bracket._--fig. 27 shows a side elevation and part horizontal section, and fig. 28 shows an end elevation of a pillar bracket for carrying a pillow block for a 3-inch shaft. draw these views _properly projected from one another_, showing the pillow block, which is to be proportioned by the rules given on page 32. draw also a plan of the whole. scale 4 inches to a foot. [illustration: fig. 28.] _hangers._--when a shaft is suspended from a ceiling it is carried by hangers, one form of which is shown in fig. 29, and which will be readily understood. the cap of the bearing, it will be noticed, is secured by means of a bolt, and also by a square key. exercise 29: _shaft hanger._--draw the two elevations shown in fig. 29, and also a sectional plan. the section to be taken at a point 5 inches above the centre of the shaft. scale 6 inches to a foot. _wall boxes._--in passing from one part of a building to another a shaft may have to pass through a wall. in that case a neat appearance is given to the opening and a suitable support obtained for a pillow block by building into the wall a _wall box_, one form of which is shown in fig. 30. exercise 30: _wall box._--draw the views of the wall box shown in fig. 30, and also a sectional plan; the plane of section to pass through the box a little above the joggles for the pillow block. scale 3 inches to a foot. [illustration: fig. 29.] [illustration: fig. 30.] viii. pulleys. _velocity ratio in belt gearing._--let two pulleys a and b be connected by a belt, and let their diameters be d_{1} and d_{2}; and let their speeds, in revolutions per minute, be n_{1} and n_{2} respectively. if there is no slipping, the speeds of the rims of the pulleys will be the same as that of the belt, and will therefore be equal. now the speed of the rim of a is evidently = d_{1} × 3.1416 × n_{1}; while the speed of the rim of b is = d_{2} × 3.1416 × n_{2}. hence d_{1} × 3.1416 × n_{1} = d_{2} × 3.1416 × n_{2}, and therefore n_{1} d_{2} ----= -----. n_{2} d_{1} _pulleys for flat bands._--in cross section the rim of a pulley for carrying a flat band is generally curved as shown in figs. 31 and 32, but very often the cross section is straight. the curved cross section of the rim tends to keep the band from coming off as long as the pulley is rotating. sometimes the rim of the pulley is provided with flanges which keep the band from falling off. pulleys are generally made entirely of cast iron, but a great many pulleys are now made in which the centre or nave only is of cast iron, the arms being of wrought iron cast into the nave, while the rim is of wrought sheet iron. the arms of pulleys when made of wrought iron are invariably straight, but when made of cast iron they are very often curved. in fig. 31, which shows an arrangement of two cast-iron pulleys, the arms are straight; while in fig. 32, which shows another cast-iron pulley, the arms are curved. through unequal cooling, and therefore unequal contraction of a cast-iron, pulley in the mould, the arms are generally in a state of tension or compression; and if the arms are straight they are very unyielding, so that the result of this initial stress is often the breaking of an arm, or of the rim where it joins an arm. with the curved arm, however, its shape permits it to yield, and thus cause a diminution of the stress due to unequal contraction. the cross section of the arms of cast-iron pulleys is generally elliptical. [illustration: fig. 31.] exercise 31: _fast and loose pulleys_.--fig. 31 shows an arrangement of fast and loose pulleys. a is the fast pulley, secured to the shaft c by a sunk key; b is the loose pulley, which turns freely upon the shaft. the loose pulley is prevented from coming off by a collar d, which is secured to the shaft by a tapered pin as shown. the nave or boss of the loose pulley is here fitted with a brass liner, which may be renewed when it becomes too much worn. draw the elevations shown, completing the left-hand one. scale 6 inches to a foot. by the above arrangement of pulleys a machine may be stopped or set in motion at pleasure. when the driving band is on the loose pulley the machine is at rest, and when it is on the fast pulley the machine is in motion. the driving band is shifted from the one pulley to the other by pressing on that side of the band which is advancing towards the pulleys. [illustration: fig. 32.] exercise 32: _cast-iron pulley with curved arms and cone keys_.--draw a complete side elevation and a complete cross section of the pulley represented in fig. 32 to a scale of 3 inches to a foot. in drawing the side elevation of the arms first draw the centre lines as shown; next draw three circles for each arm, one at each end and one in the middle; the centres of these circles being on the centre line of the arm, and their diameters equal to the widths of the arm at the ends and at the middle respectively. arcs of circles are then drawn to touch these three circles. the centres and radii of these arcs may be found by trial. the cone keys for securing the pulley to the shaft were described on p. 23. _pulleys for ropes_.--ropes made of hemp are now extensively used for transmitting power. these ropes vary in diameter from 1 inch to 2 inches, and are run at a speed of about 4,500 feet per minute. the pulleys for these ropes are made of cast iron, and have their rims grooved as shown in fig. 33, which is a cross section of the rim of a pulley carrying three ropes. the angle of the v is usually 45°, and the rope rests on the sides of the groove, and not on the bottom, so that it is wedged in, and has therefore a good hold of the pulley. the diameter of the pulley should not be less than 30 times the diameter of the rope. two pulleys connected by ropes should not be less than thirty feet apart from centre to centre, but this distance may be as much as 100 feet. [illustration: fig. 33.] exercise 33: _section of rim of rope pulley._--draw, half size, the section of the rim of a rope pulley shown in fig. 33. ix. toothed wheels. _pitch surfaces of spur wheels._--let two smooth rollers be placed in contact with their axes parallel, and let one of them rotate about its axis; then if there is no slipping the other roller will rotate in the opposite direction with the same surface velocity; and if d_{1}, d_{2} be the diameters of the rollers, and n_{1}, n_{2} their speeds in revolutions per minute, it follows as in belt gearing that- n_{1} d_{2} ----= -----. n_{2} d_{1} if there be considerable resistance to the motion of the follower slipping may take place, and it may stop. to prevent this the rollers may be provided with teeth; then they become _spur wheels_; and if the teeth be so shaped that the ratio of the speeds of the toothed rollers at any instant is the same as that of the smooth rollers, the surfaces of the latter are called the _pitch surfaces_ of the former. _pitch circle._--a section of the pitch surface of a toothed wheel by a plane perpendicular to its axis is a circle, and is called a _pitch circle_. we may also say that the pitch circle is the edge of the pitch surface. the pitch circle is generally traced on the side of a toothed wheel, and is rather nearer the points of the teeth than the roots. _pitch of teeth._--the distance from the centre of one tooth to the centre of the next, or from the front of one to the front of the next, _measured at the pitch circle_, is called the _pitch of the teeth_. if d be the diameter of the pitch circle of a wheel, _n_ the number of teeth, and _p_ the pitch of the teeth, then d × 3.1416 = _n_ × _p_. [illustration: fig. 34.] by the diameter of a wheel is meant the diameter of its pitch circle. _form and proportions of teeth._--the ordinary form of wheel teeth is shown in fig. 34. the curves of the teeth should be cycloidal curves, although they are generally drawn in as arcs of circles. it does not fall within the scope of this work to discuss the correct forms of wheel teeth. the student will find the theory of the teeth of wheels clearly and fully explained in goodeve's 'elements of mechanism,' and in unwin's 'machine design.' the following proportions for the teeth of ordinary toothed wheels may be taken as representing average practice:- pitch of teeth = _p_ = arc _a b c_ (fig. 34). thickness of tooth = _b c_ = .48_p_. width of space = _a b_ = .52_p_. total height of tooth = _h_ = .7_p_. height of tooth above pitch line = _k_ = .3_p_. depth of tooth below pitch line = _l_ = .4_p_. width of tooth = 2_p_ to 3_p_. exercise 34: _spur wheel._--fig. 35 shows the elevation and sectional plan of a portion of a cast-iron spur wheel. the diameter of the pitch circle is 23-7/8 inches, and the pitch of the teeth is 1-1/2 inches, so that there will be 50 teeth in the wheel. the wheel has six arms. draw a complete elevation of the wheel and a half sectional plan, also a half-plan without any section. draw also a cross section of one arm. scale 4 inches to a foot. [illustration: fig. 35.] _mortise wheels._--when two wheels gearing together run at a high speed the teeth of one are made of wood. these teeth, or cogs, as they are generally called, have tenons formed on them, which fit into mortises in the rim of the wheel. this wheel with the wooden teeth is called a _mortise wheel_. an example of a mortise wheel is shown in fig. 36. [illustration: fig. 36.] _bevil wheels._--in bevil wheels the pitch surfaces are parts of cones. bevil wheels are used to connect shafts which are inclined to one another, whereas spur wheels are used to connect parallel shafts. in fig. 36 is shown a pair of bevil wheels in gear, one of them being a mortise wheel. at (_a_) is a separate drawing, to a smaller scale, of the pitch cones. the pitch cones are shown on the drawing of the complete wheels by dotted lines. the diameters of bevil wheels are the diameters of the bases of their pitch cones. exercise 35: _pair of bevil wheels._--draw the sectional elevation of the bevil wheels shown in gear in fig. 36. commence by drawing the centre lines of the shafts, which in this example are at right angles to one another; then draw the pitch cones shown by dotted lines. next put in the teeth which come into the plane of the section, then complete the sections of the wheels. the pinion or smaller wheel has 25 teeth, and the wheel has 50 teeth, which makes the pitch a little over 3 inches. each tooth of the mortise wheel is secured as shown by an iron pin 5/16 inch diameter. scale 3 inches to a foot. x. cranks and cranked shafts. the most important application of the crank is in the steam-engine, where the reciprocating rectilineal motion of the piston is converted into the rotary motion of the crank-shaft by means of the crank and connecting rod. at one time steam-engine cranks were largely made of cast iron, now they are always made of wrought iron or steel. the crank is either forged in one piece with the shaft, or it is made separately and then keyed to it. _overhung crank._--fig. 37 shows a wrought-iron overhung crank. a is the crank-shaft, b the crank arm, provided at one end with a boss c, which is bored out to fit the shaft; at the other end of the crank arm is a boss d, which is bored out to receive the crank-pin e, which works in one end of the connecting rod. the crank is secured to the shaft by the sunk key f. it is also good practice to _shrink_ the crank on to the shaft. the process of shrinking consists of boring out the crank a little smaller than the shaft, and then heating it, which causes it to expand sufficiently to go on to the shaft. as the crank cools, it shrinks and grips the shaft firmly. the crank may also be shrunk on to the crank-pin, the latter being then riveted over as shown in fig. 37. [illustration: fig. 37.] a good plan to adopt in preference to the shrinking process is to force the parts together by hydraulic pressure. this method is adopted for placing locomotive wheels on their axles, and for putting in crank-pins. as to the amount of pressure to be used, the practice is to allow a force of 10 tons for every inch of diameter of the pin, axle, or shaft. instead of being riveted in, the crank pin may be prolonged and screwed, and fitted with a nut. another plan is to put a cotter through the crank and the crank-pin. the distance from the centre of the crank-shaft to the centre of the crank-pin is called the radius of the crank. the _throw_ of the crank is twice the radius. in a direct-acting engine the throw of the crank is equal to the stroke of the piston. exercise 36: _wrought-iron overhung crank._--draw the two elevations shown in fig. 37, also a plan. scale 1-1/2 inches to a foot. _proportions of overhung cranks._ d = diameter of shaft. _d_ = " crank-pin. length of large boss = .9 d. diameter " = 1.8 d. length of small boss = 1.1 _d_. diameter " = 1.8 _d_. width of crank arm at centre of shaft = 1.3 d. " " crank-pin = 1.5 _d_. the thickness of the crank arm may be roughly taken as = .7 d. exercise 37.--design a wrought-iron crank for an engine having a stroke of 4 feet. the crank-shaft is 9 inches in diameter, and the crank-pin is 4-3/4 inches in diameter and 6-1/2 inches long. [illustration: fig. 38.] _locomotive cranked axle._--as an example of a cranked shaft we take the cranked axle for a locomotive with inside cylinders shown in fig. 38; here the crank and shaft or axle are forged in one piece. a is the wheel seat, b the journal, c the crank-pin, and d and e the crank arms. only one half of the axle is shown in fig. 38, but the other half is exactly the same. the cranks on the two halves are, however, at right angles to one another. the ends of the crank arms are turned in the lathe, the crank-pin ends being turned at the same time as the axle, and the other ends at the same time as the crank-pin. this consideration determines the centres for the arcs shown in the end view. exercise 38.--draw to a scale of 2 inches to a foot the side and end elevations of the locomotive cranked axle partly shown in fig. 38. the distance between the centre lines of the cylinders is 2 feet. [illustration: fig. 39.] _built-up cranks._--the form of cranked shaft shown in fig. 38 is largely used for marine engines, but for the very powerful engines now fitted in large ships this design of shaft is very unreliable, the built-up crank shown in fig. 39 being preferred, although it is much heavier than the other. it will be seen from the figure that the shaft, crank arms, and crank-pin are made separately. the arms are shrunk on to the pin and the shaft, and secured to the latter by sunk keys. these heavy shafts and cranks are generally made of steel. exercise 39.--keeping to the dimensions marked in fig. 39, draw the views there shown of a built-up crank-shaft for a marine engine. scale 3/4 inch to a foot. xi. eccentrics. the _eccentric_ is a particular form of crank, being a crank in which the crank-pin is large enough to embrace the crank-shaft. in the eccentric what corresponds to the crank-pin is called the sheave or pulley. the advantage which an eccentric possesses over a crank is that the shaft does not require to be divided at the point where the eccentric is put on. the crank, however, has this advantage over the eccentric, namely, that it can be used for converting circular into reciprocating motion, or _vice versâ_, while the eccentric can only be used for converting circular into reciprocating motion. this is owing to the great leverage at which the friction of the eccentric acts. the chief application of the eccentric is in the steam-engine, where it is used for working the valve gear. to permit of the sheave being placed on the shaft without going over the end (which could not be done at all in the case of a cranked axle, and would be a troublesome operation in most cases) it is generally made in two pieces, as shown in fig. 40, which represents one of the eccentrics of a locomotive. the two parts of the sheave are connected by two cotter bolts. the part which embraces the sheave is called the eccentric strap, and corresponds to, and is, in fact, a connecting rod end: the rod proceeding from this is called the eccentric rod. the distance from the centre of the sheave to the centre of the shaft is called the _radius_ or _eccentricity_ of the eccentric. the _throw_ is twice the eccentricity. the sheave is generally made of cast iron. the strap may be of brass, cast iron, or wrought iron; when the strap is made of wrought iron it is commonly lined with brass. [illustration: fig. 40.] exercise 40: _locomotive eccentric._--in fig. 40 d e is the sheave, f h the strap, and k the eccentric rod. the sheave and strap are made of cast iron, and the eccentric rod is made of wrought iron. (_a_) is a vertical cross section through the oil-box of the strap; (_b_) is a plan of the end of the eccentric rod and part of the strap. all the nuts are locked by means of cotters. draw first the elevation, partly in section as shown. next draw two end elevations, one looking each way. afterwards draw a horizontal section through the centre, and also a plan. scale 4 inches to a foot. xii. connecting rods. the most familiar example of the use of a connecting rod is in the steam-engine, where it is used to connect the rotating crank with the reciprocating piston. the rod itself is made of wrought iron or steel, and is generally circular or rectangular in section. the ends of the rod are fitted with steps, which are held together in a variety of ways. _strap end._--a form of connecting rod end, which is not so common as it used to be, is shown in fig. 41. at (_a_) is shown a longitudinal section with all the parts put together, while at (_b_), (_c_), _(d)_ and (_e_) the details are shown separately. a b is the end of the rod which butts against the brass bush c d, which is in two pieces. a _strap_ e passes round the bush and on to the end of the rod as shown. the arms of the strap have rectangular holes in them, which are not quite opposite a similar hole in the rod when the parts are put together. if a wedge or _cotter_ f be driven into these three holes they will tend to come into line, and the parts of the bush will be pressed together. to prevent the cotter opening out the strap, and to increase the sliding surface, a _gib_ h is introduced. the gib is provided with horns at its ends to keep it in its place. sometimes two gibs are used, one on each side of the cotter; this makes the sliding surface on both sides of the cotter the same. the cotter is secured by a set screw k. the unsectioned portion of fig. (_a_) to the right of the gib, or to the left of the cotter, is called the _clearance_ or _draught._ [illustration: fig. 41.] exercise 41: _connecting rod end._--make the following views of the connecting rod end illustrated by fig. 41. first, a vertical section, the same as shown at (_a_). second, a horizontal section. third, side elevation. fourth, a plan. or the first and third views may be combined in a half vertical section and half elevation; and the second and fourth views may be combined in a half horizontal section and half plan. all the dimensions are to be taken from the detail drawings (_b_), (_c_), (_d_), and (_e_), _but the details need not be drawn separately_. the brass bush is shown at (_d_) by half elevation, half vertical section, half plan, and half horizontal section. the draught or clearance is 7-16ths of an inch. _box end._--at (_a_), fig. 42, is shown what is known as a box end for a connecting rod. the part which corresponds to the loose strap in the last example is here forged in one piece with the connecting rod. in this form the brass bush is provided with a flange all round on one side, but on the opposite side the flange is omitted except at one end; this is to allow of the bush being placed within the end of the rod. the construction of the bush will be understood by reference to the sketch shown at (_b_). the bush is in two parts, which are pressed tightly together by means of a cotter. this cotter is prevented from slackening back by two set screws. each set screw is cut off square at the point, and presses on the flat bottom of a very shallow groove cut on the side of the cotter. the top, bottom, and ends of this box end are turned in the lathe at the same time as the rod itself; this accounts for the curved sections of these parts. it is clear from the construction of a box end that it is only suitable for an overhung crank. exercise 42: _locomotive connecting rod._--in fig. 42 is shown a connecting rod for an outside cylinder locomotive. (_a_) is the crank-pin end, and (_c_) the cross-head end. the end (_a_) has just been described under the head 'box end.' we may just add that in this particular example the brass bush is lined with white metal as shown, and that the construction of the oil-box is the same as that on the coupling rod end shown in fig. 44. the end (_c_) is forked, and through the prongs of the fork passes the cross-head pin, of which a separate dimensioned drawing is shown at (_d_). observe that the tapered parts a and b of this pin are parts of the same cone. the rotation of the pin is prevented by a small key as shown. the cross-head pin need not be drawn separately, and the isometric projection of the bush at (_b_) may be omitted, but all the other views shown are to be drawn to a scale of 6 inches to a foot. _marine connecting rod._--the form of connecting rod shown in fig. 43 is that used in marine engines, but it is also used extensively in land engines. a b is the crank-pin end, and c the cross-head end. the end a b is forged in one piece, and after it is turned, planed, and bored it is slotted across, so as to cut off the cap a. the parts a and b are held together by two bolts as shown. this end of the rod is fitted with brass steps, which are lined with white metal. the cross-head end is forked, and through the prongs of the fork passes a pin d, which also passes through the cross-head, which is forged on to the piston rod or attached to it in some other way. [illustration: fig. 42.] [illustration: fig. 43.] exercise 43: _marine connecting rod._--draw all the views shown in fig. 43 of one form of marine connecting rod. for detail drawings of the locking arrangement for the nuts see fig. 19, page 21. scale 4 inches to a foot. _coupling rods._--a rod used to transmit the motion of one crank to another is called a _coupling rod_. a familiar example of the use of coupling rods will be found in the locomotive. coupling rods are made of wrought iron or steel, and are generally of rectangular section. the ends are now generally made solid and lined with solid brass bushes, _without any adjustment for wear_. this form of coupling rod end is found to answer very well in locomotive practice where the workmanship and arrangements for lubrication are excellent. when the brass bush becomes worn it is replaced by a new one. fig. 44 shows an example of a locomotive coupling rod end for an outside cylinder engine. in this case it is desirable to have the crank-pin bearings for the coupling rods as short as possible, for a connecting rod and coupling rod in this kind of engine work side by side on the same crank-pin, which, being overhung, should be as short as convenient for the sake of strength. the requisite bearing surface is obtained by having a pin of large diameter. the brass bush is prevented from rotating by means of the square key shown. the oil-box is cut out of the solid, and has a wrought-iron cover slightly dovetailed at the edges. this cover fits into a check round the top inner edge of the box, which is originally parallel, but is made to close on the dovetailed edges of the cover by riveting. a hole in the centre of this cover, which gives access to the oil-box, is fitted with a screwed brass plug. the brass plug has a screwed hole in the centre, through which oil may be introduced to the box. dust is kept out of the oil-box by screwing into the hole in the brass plug a common cork. the oil is carried slowly but regularly from the oil-box over to the bearing by a piece of cotton wick. [illustration: fig. 44.] exercise 44: _coupling rod end._--draw first the side elevation and plan, each partly in section as shown in fig. 44. then instead of the view to the left, which is an end elevation partly in section, draw a complete end elevation looking to the right, and also a complete vertical cross section through the centre of the bearing. scale 6 inches to a foot. xiii. cross-heads. an example of a steam-engine cross-head is shown in fig. 45. a is the end of the piston rod which has forged upon it the cross-head b. the cross-head pin shown at (_d_), fig. 42, and to which the connecting rod is attached, works in the bearing c. projecting pieces d, forged on the top and bottom of the cross-head, carry the slide blocks e which work on the slide bars, and thus guide the motion of the piston rod. [illustration: fig. 45.] exercise 45: _locomotive cross-head._--in fig. 45 are shown side and end elevations, partly in section, of the cross-head and slide blocks for an outside cylinder locomotive. draw these views half size, showing also on the end elevation the cross-head pin and a vertical section of the connecting rod end from fig. 42. the bush in the cross-head which forms the bearing for the cross-head pin is of wrought iron, case-hardened, and is prevented from rotating by the key shown. the cross-head is of wrought iron, and the slide blocks are of cast iron, and are fitted with white metal strips as shown. a short brass tube leads oil from the upper slide block into a hole in the cross-head as shown, which carries it to a slot in the bush which distributes it over the cross-head pin. xiv. pistons. a _piston_ is generally a cylindrical piece which slides backwards and forwards inside a hollow cylinder. the piston may be moved by the action of fluid pressure upon it as in a steam-engine, or it may be used to give motion to a fluid as in a pump. a piston is usually attached to a rod, called a _piston rod_, which passes through the end of the cylinder inside which the piston works, and which serves to transmit the motion of the piston to some piece outside the cylinder, or _vice versâ_. [illustration: fig. 46.] a _plunger_ is a piston made in one piece with its piston rod, the piston and the rod being of the same diameter. a piston which is provided with one or more valves which allow the fluid to pass through it from one side to the other is called a _bucket_. _simple piston._--the simplest form of piston is a plain cylinder fitting accurately another, inside which it moves. such a piston works with very little friction, but as there is no adjustment for wear, such a piston is not suitable for a high fluid pressure if it has to work constantly. this simple form of piston is used in the steam-engine indicator, and also in pumps. fig. 46 shows the piston of the circulation pump of a marine engine. a is the cast-iron casing or barrel of the pump; b is a brass liner fitting tightly into the former at its ends, and secured by eight screwed muntz metal pins c, four at each end; d is the piston, which is made of brass, and is attached to a muntz metal piston rod e. the liner is bored out smooth and true from end to end, and the piston is turned so as to be a sliding fit to the liner. the wear in this form of piston is diminished by making the rubbing surface large. exercise 46: _piston for circulating pump._--draw the vertical sectional elevation of the piston, &c., shown in fig. 46, also a half plan and half horizontal section through the centre. scale 4 inches to a foot. _pump bucket._--the next form of piston which we illustrate is shown in fig. 47. this represents the air-pump bucket of a marine engine. the bucket is made of brass, and is provided with six india-rubber disc valves. the rod is in this case made of muntz metal. air-pump rods for marine engines are very often made of wrought iron cased with brass. it will be observed that there is a wide groove around the bucket, which is filled with hempen rope or gasket. this gasket forms an elastic packing which prevents leakage. this is an old-fashioned form of packing, and is now only used for pump buckets. [illustration: fig. 47.] exercise 47: _air-pump bucket._--draw the sectional elevation of the air-pump bucket shown in fig. 47. also draw a half plan looking downwards and a half plan looking upwards. scale 4 inches to a foot. _ramsbottom's packing._--the form of packing used in the air-pump bucket, fig. 47, is not suitable for steam pistons. for the latter the packing is now always metallic. the simplest form of metallic packing is that known as ramsbottom's. this form is very largely used for locomotive pistons, and for small pistons in many kinds of engines besides. a locomotive piston for an 18-inch cylinder with ramsbottom's packing is shown in fig. 48. the particular piston there illustrated is made of brass, and is secured to a wrought-iron piston rod by a brass nut. two circumferential grooves of rectangular section are turned out of the piston, and into these fit two corresponding rings, which may be of brass, cast iron, or steel. in this example the rings are of cast iron. these rings are first turned a little larger in diameter than the bore of the cylinder (in this example 1/2 inch), and then sprung over the piston into the groves prepared for them. their own elasticity causes the rings to press outwards on the cylinder. at the point where a ring is split a leakage of steam will take place, but with quick-running pistons this leakage is unimportant. the points where the rings are cut should be placed diametrically opposite, so as to diminish the leakage of steam. [illustration: fig. 48.] exercise 48: _locomotive piston._--a part elevation and part section of a locomotive piston, for a cylinder having a bore 18 inches in diameter, is shown in fig. 48. draw this, and also a view looking on the nut in the direction of the axis of the piston rod. scale 6 inches to a foot. _note._--the reason why the part of the piston rod within the piston has such a quick taper is that the piston has to be taken off the rod while it is in the cylinder. the cross-head being forged on the end of the piston rod prevents the piston and piston rod being withdrawn together. _large pistons._--pistons of large diameter are generally provided with two cast-iron packing rings placed within the same groove. these rings are pressed outwards against the cylinder, and also against the sides of the groove by one or more springs. one form of this packing (lancaster's) is shown in fig. 49. here one spring only is used, and it is first made a straight spiral spring, and then bent round and its ends united. the action of the spring will be clearly understood from the illustration. for the purpose of admitting the packing rings the piston is divided into two parts, one the piston proper, and the other the _junk ring_. in fig. 49, a is the junk ring, which is secured to the piston by means of bolts as shown. [illustration: fig. 49.] exercise 49: _marine engine piston._--the piston illustrated by fig. 49 is for the high-pressure cylinder of a marine engine. the piston, junk ring, and packing rings are of cast iron. the piston rod and nut are of wrought iron, so also are the junk ring bolts. the nuts for the latter are of brass. the spiral spring is made from steel wire 3/8 inch diameter. an enlarged section of one of the packing rings is shown at (_a_). a front elevation of the locking arrangement for the piston rod nut is shown at (_b_). a sectional plan of one of the nuts for the junk ring bolts is shown at (_c_). first draw the vertical section of this piston, next draw a plan, one-third of which is to show the piston complete, one-third to show the junk ring removed, and the remaining third to be a horizontal section through between the packing rings. the details (_a_) and (_c_) need not be drawn separately. scale 3 inches to a foot. _proportions of marine engine pistons._--mr. seaton, in his 'manual of marine engineering,' gives the following rules for designing marine engine pistons:- d = diameter of piston in inches. _p_ = effective pressure in lbs. per square inch. _x_ = d/50 × [sqrt (_p_)] + 1. thickness of front of piston near boss 0.2 × _x_. " " " rim 0.17 × _x_. " back of piston 0.18 × _x_. " boss around rod 0.3 × _x_. " flange inside packing ring 0.23 × _x_. " " at edge 0.25 × _x_. " junk ring at edge 0.23 × _x_. " " inside packing ring. 0.21 × _x_. " " at bolt-holes 0.35 × _x_. " metal around piston edge 0.25 × _x_. breadth of packing ring 0.63 × _x_. depth of piston at centre 1.4 × _x_. lap of junk ring on piston 0.45 × _x_. space between piston body and packing ring 0.3 × _x_. diameter of junk-ring bolts 0.1 × _x_ + .25 inch. pitch of junk-ring bolts 10 diameters. number of webs in piston (d + 20)/12. thickness " 0.18 × _x_. exercise 50: _design for marine engine piston._--calculate by seaton's rules the dimensions for a marine engine piston 40 inches in diameter, and subjected to an effective pressure of 36 lbs. per square inch. then make the necessary working drawings for this piston to a scale of, say, 3 inches to a foot. _note._--take the dimensions got by calculation to the nearest 1-16th of an inch. xv. stuffing-boxes. [illustration: fig. 50.] in fig. 50 is shown a gland and stuffing-box for the piston rod of a vertical engine. a b is the piston rod, c d a portion of the cylinder cover, and e f the _stuffing-box_. fitting into the bottom of the stuffing-box is a brass bush h. the space k around the rod a b is filled with _packing_, of which there is a variety of kinds, the simplest being greased hempen rope. the packing is compressed by screwing down the cast-iron gland l m, which is lined with a brass bush n. in this case the gland is screwed down by means of three stud-bolts p, which are screwed into a flange cast on the stuffing-box. surrounding the rod on the top of the gland there is a recess r for holding the lubricant. [illustration: fig. 51.] [illustration: fig. 52.] the object of the gland and stuffing-box is to allow the piston rod to move backwards and forwards freely without any leakage of steam. fig. 51 shows a gland and stuffing-box for a horizontal rod. the essential difference between this example and the last is in the mode of lubrication. the gland flange has cast within it an oil-box which is covered by a lid; this lid is kept shut or open by the action of a small spring as shown. a piece of cotton wick (not shown in the figure) has one end trailing in the oil in the oil-box, while the other is carried over and passed down the hole a b. the wick acts as a siphon, and drops the oil gradually on to the rod. in this example only two bolts are used for screwing in the gland; and the flanges of the gland and stuffing-box are not circular, but oval-shaped. in the case of small rods the gland is made entirely of brass, and no liner is then necessary. fig. 52 shows a form of gland and stuffing-box sometimes used for small rods. the stuffing-box is screwed externally, and carries a nut a b which moves the gland. exercise 51: _gland and stuffing-box for a vertical rod._--draw the views shown in fig. 50 to the dimensions given. scale 6 inches to a foot. exercise 52: _gland and stuffing-box for a horizontal rod._--fig. 51 shows a plan, half in section, and an elevation half of which is a section through the gland flange. draw these to a scale of 6 inches to a foot, using the dimensions marked in the figure. exercise 53: _screwed gland and stuffing-box._--draw, full size, the views shown in fig. 52 to the given dimensions. a more elaborate form of gland and stuffing-box is shown in fig. 53. this is for a large marine engine with inverted cylinders, such as is used on board large ocean steamers. the stuffing-box is cast separate from the cylinder cover to which it is afterwards bolted. the lubricant is first introduced to the oil-boxes marked a, from which it passes to the recess b, where it comes in contact with the piston rod. to prevent the lubricant from being wasted by running down the rod, the main gland is provided with a shallow gland and stuffing-box which is filled with soft cotton packing, which soaks up the lubricant. the main gland is screwed up by means of six bolts, and to prevent the gland from locking itself in the stuffing-box, it is necessary that the nuts should be turned together. this is done in a simple and ingenious manner. one-half of each nut is provided with teeth, and these gear with a toothed wheel which has a rim only; this rim is held up by a ring c. when one nut is turned, all the rest follow in the same direction. [illustration: fig. 53.] exercise 54: _gland and stuffing-box for piston rod of large inverted cylinder engine._--the lower view in fig. 53 is a half plan looking upwards, and a half section of the gland looking downwards. the upper view is a vertical section. complete all these views and add an elevation. scale 3 inches to a foot. _note._--the large nuts, the wheel, the supporting ring, and small gland are made of brass. _dimensions of stuffing-boxes and glands._ _d_ = diameter of rod. _t__{1} = thickness of _d__{1} = diameter of box (inside). stuffing-box flange. _l_ = length of stuffing-box _t__{2} = thickness of gland bush. flange. _l__{1} = length of packing space. _t__{3} = thickness of bushes in _l__{2} = length of gland. box and gland. _t_ = thickness of metal in _d__{2} = diameter of gland bolts. stuffing-box. _n_ = number of bolts. +----------------------------------------------------------+ | _d_ | _d__{1} | _l_ | _l__{1} | _l__{2} | _t_ | _t__{1} | +-----+---------+-----+---------+---------+------+---------+ |1 | 1-3/4 | 3/4| 2 | 1-1/2 | 7/16| 1/2 | |1-1/2| 2-1/2 |1-1/4| 2-5/8 | 2 | 9/16| 11/16 | |2 | 3-1/2 |1-3/4| 3-1/4 | 2-1/2 | 11/16| 7/8 | |2-1/2| 4-1/8 |2-1/4| 3-7/8 | 2-7/8 | 13/16| 1-1/16 | |3 | 4-3/4 |2-3/4| 4-1/2 | 3-1/4 | 15/16| 1-1/4 | |3-1/2| 5-1/4 | 3 | 5-1/8 | 3-5/8 |1 | 1-3/8 | |4 | 5-7/8 |3-1/4| 5-3/4 | 4 |1 | 1-3/8 | |4-1/2| 6-3/8 |3-1/2| 6-3/8 | 4-3/8 |1-1/16| 1-9/16 | |5 | 7 |3-3/4| 7 | 4-5/8 |1-1/16| 1-9/16 | |6 | 8 |4-1/4| 8-1/4 | 5 |1-1/8 | 1-11/16 | +----------------------------------------------------------+ +-------------------------------------------------+ | _d_ | _t__{2} | _t__{3} | _d__{2} | _n_ | +-----+-----------------+---------+---------+-----+ |1 | _t__{2}=_t_ | 3/16 | 7/16 | 2 | |1-1/2| when gland | 1/4 | 5/8 | 2 | |2 | flange is | 5/16 | 3/4 | 2 | |2-1/2| made of cast | 5/16 | 7/8 | 2 | |3 | iron and | 3/8 | 1 | 2 | |3-1/2| _t__{2}=_t__{1} | 3/8 | 1 | 2 | |4 | when gland | 7/16 | 1 | 2 | |4-1/2| flange is | 7/16 | 7/8 | 4 | |5 | made of | 7/16 | 1 | 4 | |6 | brass. | 1/2 | 1-1/4 | 4 | +-------------------------------------------------+ the proportions of glands and stuffing-boxes vary considerably but the above table represents average practice. exercise 55:--make the necessary working drawings for a gland and stuffing-box for a locomotive engine piston rod 2-1/2 inches in diameter, to the dimensions given in the table. xvi. valves. professor unwin divides valves, according to their construction into three classes as follows:--(1) flap valves, which bond or turn upon a hinge; (2) lift valves, which rise perpendicularly to the seat; (3) sliding valves, which move parallel to the seat. examples of flap valves are shown in figs. 54 and 55; two forms of lift valves are shown in figs. 56 and 57, and in figs. 58 and 59 are shown two forms of slide valve. the slide valve shown in fig. 58 moves in a straight line, while that shown in fig. 59 (called a cock) moves in circle. _india-rubber valves._--in india-rubber valves there is a grating covered by a piece of india-rubber, which may be rectangular, but is generally circular, and which is held down along one edge if rectangular, or at the centre if circular. water or other fluid can pass freely upwards through the grating, but when it attempts to return the elasticity of the india-rubber, and the pressure of the water upon it, cause it to lie close on the grating, and thus prevent the return of the water. the india-rubber is prevented from rising too high by a perforated guard. in fig. 54 is shown an example of an india-rubber disc valve. a is the grating, b the india-rubber, c the guard secured to the grating or seat by the stud d and nut e. the grating is held in position by bolts and nuts f. the grating and guard are generally of brass. india-rubber disc valves are also shown on the air-pump bucket, fig. 47. exercise 56: _india-rubber disc valve._--fig. 54 shows a vertical section and a plan of an india-rubber disc valve. in the plan one-half of the guard and india-rubber are supposed to be removed so as to show the grating or seat. draw these views, and also an elevation. a detail drawing of the central stud is shown in fig. 16, page 18. in fig. 54 the elevation of the guard is drawn as it is usually drawn in practice, but if the student has a sufficient knowledge of descriptive geometry he should draw the elevation completely showing the perforations. scale 6 inches to a foot. [illustration: fig. 54.] [illustration: fig. 55.] _kinghorn's metallic valve._--the action of this valve is the same as that of an india-rubber valve, but a thin sheet of metal (phosphor bronze) takes the place of the india-rubber. this valve is now largely used in the pumps of marine engines, and is shown in fig. 55 as applied to an air-pump bucket. three valves like the one shown are arranged round the bucket. exercise 57: _kinghorn's metallic valve._--fig. 55 shows an elevation and plan of one form of this valve. in the plan one-half of the guard and metal sheet are supposed to be removed, so as to show the grating, which in this case is part of an air-pump bucket. draw the views shown, and also a vertical section of the guard through the centres of the bolts. all the parts are of brass except the valve proper, which is of phosphor bronze. scale 6 inches to a foot. _conical disc valves._--a very common form of valve is that shown in figs. 56 and 57. this form of valve consists of a disc, the edge of which (called the face) is conical. the conical edge of this disc fits accurately on a corresponding seat. the angle which the valve face makes with its axis is generally 45°. if the disc is raised, either by the action of the fluid as in the india-rubber valve, or by other means, an opening is formed around the disc through which the fluid can pass. the valve is guided in rising and falling either by three feathers underneath it, as in fig. 56, or by a central spindle which moves freely through a hole in the centre of a bridge which stretches across the seat, as in fig. 57. the lift of the valve is limited by a stop above it, which forms part of the casing containing the valve. the lift should in no case exceed one-fourth of the diameter of the valve, and it is generally much less than this. the guiding feathers (fig. 56) are notched immediately under the disc for the purpose of making available the full circumferential opening of the valve for the passage of the fluid. these notches also prevent the feathers from interfering with the turning or scraping of the valve face. conical disc valves and their seats are nearly always made of brass. exercise 58: _conical disc valves._--draw, half size, the plans and elevations shown in figs. 56 and 57. in fig. 57 the valve is shown open in the elevation, and in the plan it is removed altogether in order to show the seat with its guide bridge. [illustration: plan of valve. fig. 56.] [illustration: plan of seat. fig. 57.] _simple slide valve._--the form of valve shown in fig. 58, often called the _locomotive slide valve_, is very largely used in all classes of steam-engines for distributing the steam in the steam cylinders. the valve is shown separately at (_d_), (_e_), and (_f_), while at (_a_), (_b_), and (_c_) is shown its connection with the steam cylinder. it will be observed that the valve itself is in the shape of a box with one side open, the edges of the open side being flanged. when the valve is in its middle position, as shown at (_a_), two of these flanged edges completely cover two rectangular openings s_{1} and s_{2}, called _steam ports_, while the hollow part of the valve is opposite to a third port e, called the _exhaust port_. as shown at (_a_) the piston p would be moving upwards and the valve downwards. by the time the piston has reached the top of its stroke the valve will have moved so far down as to partly uncover the steam port s_{1}, and admit steam from the valve casing c through s_{1} and the passage p_{1} to the top of the piston. the pressure of this steam on the top of the piston will force the latter down. while the above action has been going on, the port s_{2} will have become uncovered, and the hollow part of the valve will be opposite both the steam port s_{2} and the exhaust port e, so that the steam from the under side of the piston, and which forced the piston up, can now escape by the passage p_{2}, the steam port s_{2}, and the exhaust port e to the exhaust outlet o, and thence into the atmosphere, if it is a non-condensing engine, or into the condenser if it is a condensing engine, or into another cylinder if it is a compound engine. after the piston has performed, a certain part of its downward stroke, the valve, which has been moving downwards, will commence to move upwards, and when it has reached a certain point it will cover the port s_{1}, and shut off the supply of steam to the top of the piston. it is generally arranged that the steam shall be cut off before the piston reaches the end of the stroke. when the piston reaches the bottom of its stroke the valve has moved far enough up to uncover the port s_{2} and admit steam to the bottom of the piston, and to uncover the port s_{1} and allow the steam to escape from the top of the piston through the passage p_{1}, the port s_{1}, the port e, and outlet o. in this way the piston is moved up and down in the cylinder. the valve is attached to a valve spindle s by nuts as shown, the hole in the valve through which the spindle passes being oval-shaped to permit of the valve adjusting itself so as to always press on its seat. when the valve is in its middle position it generally more than covers the steam ports. the amount which the valve projects over the steam port on the outside, the valve being in its middle position, is called the _outside lap_ of the valve, and the amount which it projects on the inside is called the _inside lap_. when the term lap is used without any qualification, outside lap is to be understood. in fig. 58 it will be seen that the valve has no inside lap, and that the outside lap is three-eighths of an inch. the inside lap is generally small compared with the outside lap. [illustration: fig. 58.] when the piston is at the beginning of its stroke the steam port is generally open by a small amount called the _lead_ of the valve. the reciprocating motion of the slide valve is nearly always derived from an eccentric fixed on the crank-shaft of the engine. slide valves are generally made of brass, bronze, or cast iron. exercise 59: _simple slide valve._--at (_d_), fig. 58, is shown a sectional elevation of a simple slide valve for a steam-engine, the section being taken through the centre line of the valve spindle, while at (_e_) is shown a cross section and elevation, and at (_f_) a plan of the same. draw all these views full size, and also a sectional elevation at a b. the valve is made of brass, and the valve spindle and nuts of wrought iron. exercise 60: _slide valve casing, &c., for steam-engine._--draw, half size, the views shown at (_a_), (_b_), and (_c_), fig. 58; also a sectional plan at l m. (_b_) is an elevation of the valve casing with the cover and the valve removed. (_a_) is a sectional elevation, the section being taken through the axes of the steam cylinder and valve spindle. (_c_) is a sectional plan, the section being a horizontal one through the centre of the exhaust port. the inlet and outlet for the steam are clearly shown in the sectional plan: in the sectional elevation their positions are shown by dotted circles. the stroke of the piston is in this case 12 inches, so that from the dimensions given at (_a_) it must come within a quarter of an inch of each end of the cylinder; this is called the _cylinder clearance_. the piston has three ramsbottom rings, a quarter of an inch wide and a quarter of an inch apart. the steam cylinder and valve casing are made of cast iron. _cocks._--a cock consists of a slightly conical plug which fits into a corresponding casing cast on a pipe. through the plug is a hole which may be made by turning the plug to form a continuation of the hole in the pipe, and thus allow the fluid to pass, or it may be turned round so that the solid part of the plug lies across the hole in the pipe, and thus prevent the fluid from passing. as the student will be quite familiar with the common water cock or tap such as is used in dwelling-houses we need not illustrate it here. [illustration: fig. 59.] fig. 59 shows a cock of considerable size, which may be used for water or steam under high pressure. the plug in this example is hollow, and is prevented from coming out by a cover which is secured to the casing by four stud bolts. an annular ridge of rectangular section projecting from the under side of the cover, and fitting into a corresponding recess on the top of the casing, serves to ensure that the cover and plug are concentric, and prevents leakage. leakage at the neck of the plug is prevented by a gland and stuffing-box. the top end of the plug is made square to receive a handle for turning it. the size of a cock is taken from the bore of the pipe in which it is placed; thus fig. 59 shows a 2-1/4-inch cock. exercise 61: 2-1/4-_inch steam or water cock._--first draw the views of this cock shown in fig. 59, then draw a half end elevation and half cross section through the centre of the plug. scale 6 inches to a foot. instead of drawing the parts of the pipe on the two sides of the plug in the same straight line as in fig. 59, one may be shown proceeding from the bottom of the casing, so that the fluid will have to pass through the bottom of the plug and through one side. this is a common arrangement. all the parts of the valve and casing in this example are made of brass. xvii. materials used in machine construction. _cast iron._--the essential constituents of cast iron are iron and carbon, the latter forming from 2 to 5 per cent. of the total weight. cast iron, however, usually contains varying small amounts of silicon, sulphur, phosphorus, and manganese. in cast iron the carbon may exist partly in the free state and partly in chemical combination with the iron. in _white cast iron_ the whole of the carbon is in chemical combination with the iron, while in _grey cast iron_ the carbon is principally in the free state, that is, simply mixed mechanically with the iron. it is the free carbon which gives the grey iron its dark appearance. a mixture of the white and grey varieties of cast iron when melted produces _mottled cast iron_. the greater the amount of carbon chemically combined with the iron, the whiter, harder, and more brittle does it become. the white cast iron is stronger than the grey, but being more brittle it is not so suitable for resisting suddenly applied loads. white iron melts at a lower temperature than grey iron, but after melting it does not flow so well, or is not so liquid as the grey iron. white iron contracts while grey iron expands on solidifying. the grey iron, therefore, makes finer castings than the white. castings after solidifying contract in cooling about 1/8 of an inch per foot. castings possessing various degrees of strength and hardness are produced by melting mixtures of various proportions of white and grey cast irons. white cast iron has a higher specific gravity than grey cast iron. cast iron gives little or no warning before breaking. the thickness of the metal throughout a casting in cast iron should be as uniform as possible, so that it may cool and therefore contract uniformly throughout; otherwise some parts may be in a state of initial strain after the casting has cooled, and will therefore be easier to fracture. re-entrant angles should be avoided; such should be rounded out with fillets. the presence of phosphorus in cast iron makes it more fusible, and also more brittle. the presence of sulphur diminishes the strength considerably. the grey varieties of cast iron are called _foundry irons_ or _foundry pigs_, while the white varieties are called _forge irons_ or _forge pigs_, from the fact that they are used for conversion into wrought iron. amongst iron manufacturers the different varieties of cast iron are designated by the numbers 1, 2, 3, &c., the lowest number being applied to the greyest variety. _chilled castings._--when grey cast iron is melted a portion of the free carbon combines chemically with the iron; this, however, separates out again if the iron is allowed to cool slowly; but if it is suddenly cooled a greater amount of the carbon remains in chemical combination, and a whiter and harder iron is produced. advantage is taken of this in making _chilled castings_. in this process the whole or a part of the mould is lined with cast iron, which, being a comparatively good conductor of heat, chills a portion of the melted metal next to it, changing it into a hard white iron to a depth varying from 1/8 to 1/2 an inch. to protect the cast-iron lining of the mould from the molten metal it is painted with loam. _malleable cast iron._--this is prepared by imbedding a casting in powdered red hematite (an oxide of iron), and keeping it at a bright red heat for a length of time varying from several hours to several days according to the size of the casting. by this process a portion of the carbon in the casting is removed, and the strength and toughness of the latter become more like the strength and toughness of wrought or malleable iron. _wrought or malleable iron._--this is nearly pure iron, and is made from cast iron by the puddling process, which consists chiefly of raising the cast iron to a high temperature in a reverberatory furnace in the presence of air, which unites with the carbon and passes off as gas. in other words the carbon is burned out. the iron is removed from the puddling furnace in soft spongy masses called _blooms_, which are subjected to a process of squeezing or hammering called _shingling_. these shingled blooms still contain enough heat to enable them to be rolled into rough _puddled bars_. these puddled bars are of very inferior quality, having less than half the strength of good wrought iron. the puddled bars are cut into pieces which are piled together, reheated, and again rolled into bars, which are called _merchant bars_. this process of piling, reheating, and re-rolling may be repeated several times, depending on the quality of iron required. up to a certain point the quality of the iron is improved by reheating and rolling or hammering, but beyond that a repetition of the process diminishes the strength of the iron. the process of piling and rolling gives wrought iron a fibrous structure. when subjected to vibrations for a long time, the structure becomes crystalline and the iron brittle. the crystalline structure induced in this way may be removed by the process of _annealing_, which consists in heating the iron in a furnace, and then allowing it to cool slowly. _forging and welding._--the process of pressing or hammering wrought iron when at a red or white heat into any desired shape is called _forging_. if at a white heat two pieces of wrought iron be brought together, their surfaces being clean, they may be pressed or hammered together, so as to form one piece. this is called _welding_, and is a very valuable property of wrought iron. _steel._--this is a compound of iron with a small per-centage of carbon, and is made either by adding carbon to wrought iron, or by removing some of the carbon from cast iron. in the _cementation_ process, bars of wrought iron are imbedded in powdered charcoal in a fireclay trough, and kept at a high temperature in a furnace for several days. the iron combines with a portion of the carbon to form _blister steel_, so named because of the blisters which are found on the surface of the bars when they are removed from the furnace. the bars of blister steel are broken into pieces about 18 inches long, and tied together in bundles by strong steel wire. these bundles are raised to a welding heat in a furnace, and then hammered or rolled into bars of _shear steel_. to form _cast steel_ the bars of blister steel are broken into pieces and melted into crucibles. in the _siemens-martin_ process for making steel, cast and wrought iron are melted together on the hearth of a regenerative gas-furnace. _bessemer steel_ is made by pouring melted cast iron into a vessel called a converter, through which a blast of air is then urged. by this means the carbon is burned out, and comparatively pure iron remains. to this is added a certain quantity of 'spiegeleisen,' which is a compound of iron, carbon, and manganese. _hardening and tempering of steel._--steel, if heated to redness and cooled suddenly, as by immersion in water, is hardened. the degree of hardness produced varies with the rate of cooling; the more rapidly the heated steel is cooled, the harder does it become. hardened steel is softened by the process of _annealing_, which consists in heating the hardened steel to redness, and then allowing it to cool slowly. hardened steel is _tempered_, or has its degree of hardness lowered, by being heated to a temperature considerably below that of a red heat, and then cooling suddenly. the higher the temperature the hardened steel is raised to, the lower does its 'temper' become. _case-hardening._--this is the name given to the process by which the surfaces of articles made of wrought iron are converted into steel, and consists in heating the articles in contact with substances rich in carbon, such as bone-dust, horn shavings, or yellow prussiate of potash. this process is generally applied to the articles after they are completely finished by the machine tools or by hand. the coating of steel produced on the article by this process is hardened by cooling the article suddenly in water. _copper._--this metal has a reddish brown colour, and when pure is very malleable and ductile, either when cold or hot, so that it may be rolled or hammered into thin plates, or drawn into wire. slight traces of impurities cause brittleness, although from 2 to 4 per cent. of phosphorus increases its tenacity and fluidity. copper is a good conductor of heat and of electricity. copper is largely used for making alloys. _alloys._--_brass_ contains two parts by weight of copper to one of zinc. _muntz metal_ consists of three parts of copper to two of zinc. alloys consisting of copper and tin are called _bronze_ or _gun-metal_. bronze is harder the greater the proportion of tin which it contains; five parts of copper to one of tin produce a very hard bronze, and ten of copper to one of tin is the composition of a soft bronze. _phosphor bronze_ contains copper and tin with a little phosphorus; it has this advantage over ordinary bronze, that it may be remelted without deteriorating in quality. this alloy also has the advantage that it may be made to possess great strength accompanied with hardness, or less strength with a high degree of toughness. _wood._--in the early days of machines wood was largely used in their construction, but it is now used to a very limited extent in that direction. _beech_ and _hornbeam_ are used for the cogs of mortise wheels. _yellow pine_ is much used by pattern-makers. _box_, a heavy, hard, yellow-coloured wood, is used for the sheaves of pulley blocks, and sometimes for bearings in machines. _lignum-vitæ_ is a very hard dark-coloured wood, and remarkable for its high specific gravity, being 1-1/3 times the weight of the same volume of water. this wood is much used for bearings of machines which are under water. xviii. miscellaneous exercises. the illustrations in this chapter are in most cases not drawn to scale; they are also in some parts incomplete, and in others some of the lines are purposely drawn wrong. the student must keep to the dimensions marked on the drawings, and where no sizes are given he must use his own judgment in proportioning the parts. all errors must be corrected, and any details required, but not shown completely in the illustrations, must be filled in. exercise 62: _single riveted butt joint with tee-iron cover strap._--two views, one a side elevation and the other a sectional elevation, of a riveted joint are shown in fig. 60. draw these views, and also a plan projected from one of them. show the rivets completely in all the views. scale 4 inches to a foot. [illustration: fig. 60.] [illustration: fig. 61.] exercise 63: _girder stay for steam boiler._--the flat crown of the fire-box of locomotive and marine boilers is generally supported or stayed by means of girder stays, an example of which is shown in fig. 61. a b is the side elevation of a portion of one of these girders. each girder is supported at its ends by the plates forming the vertical sides of the fire-box. the flat crown is bolted to the girders as shown. observe that the girders are in contact with the crown only in the neighbourhood of the bolts. consider carefully this part of the design, and then answer the following questions: (1) what objections are there to supporting the girders at the ends only without the contact pieces at the bolts? (2) what objections are there to having the girders in contact with the crown plate of the fire-box throughout their whole length? draw the views shown in fig. 61, and from the right-hand one project a plan. scale 4 inches to a foot. [illustration: fig. 62.] exercise 64: _end of bar stay for steam boiler._--on page 12 one form of stay for supporting the flat end of a steam boiler is described. another form of stay for the same purpose is shown in fig. 62. a b is a portion of the end of a steam boiler. c d is one end of a bar which extends from one end of the boiler to the other. the ends of this bar are screwed, and when the bar is of wrought iron the screwed parts are generally larger in diameter than the rest of the bar. when made of steel the bar is generally of uniform diameter throughout. in the case of wrought-iron bar stays the enlarged ends are welded on to the smaller parts. welding is not so reliable with steel as with wrought iron. write out answers to the following questions: (1) what is the advantage of having the screwed part of the bar larger in diameter than the rest? (2) why are steel bar stays not generally enlarged at their screwed ends? draw the views shown in fig. 62, and project from one of them a third view. scale 4 inches to a foot. exercise 65: _knuckle joint._--draw the plan and elevation of this joint shown in fig. 63, and also draw an end elevation looking in the direction of the arrow. the parts at a and b are octagonal in cross section. scale 4 inches to a foot. [illustration: fig. 63.] exercise 66: _locomotive coupling rod ends._--a form of knuckle joint used on locomotive coupling rods is shown in fig. 64. in this case two rods meet and work on the same pin, as shown at (a) fig. 64. draw, in addition to the views shown in fig. 64, a plan and a vertical section through the axis of the pin. scale 6 inches to a foot. would it be practicable to replace the two rods a b and b c by a single rod working on the crank pins at a, b, and c? give reasons for your answer. [illustration: fig. 64.] exercise 67: _bell crank lever._--draw the plan and elevation of the lever shown in fig. 65. scale 6 inches to a foot. [illustration: fig. 65.] exercise 68: _back stay for lathe._--draw a plan and two elevations of the stay shown in fig. 66. make all necessary corrections and show all the details in each view. scale full size. [illustration: fig. 66.] [illustration: fig. 67.] exercise 69: _conical disc valve and casing._--draw, half size, the views shown in fig. 67 of the conical disc valve and casing, and also add an elevation looking in the direction of the arrow. exercise 70: _connecting rod end._--the student should carefully compare this connecting rod end (fig. 68) with those illustrated on pages 50 and 52. the lower part of fig. 68 is a half plan and half horizontal section, and the upper part is a half side elevation and half vertical section. draw these views and also an end elevation. scale 6 inches to a foot. [illustration: fig. 68.] [illustration: fig. 69.] [illustration: fig. 70.] [illustration: fig. 71.] [illustration: fig. 72.] [illustration: fig. 73.] [illustration: fig. 74.] exercise 71: _engine cross-head._--the cross-head shown in fig. 69 is for an inverted cylinder marine engine. a is the piston rod, and b b are pins, forged in one piece with c, to which the forked end of the connecting rod is attached. draw the upper view with the central part in section as shown. make the right-hand half of the lower view a plan without any section, and make the left-hand half a horizontal section through the axis of the pins b b. scale 4 inches to a foot. exercise 72: _ratchet lever._--the lever shown in fig. 70 is used for turning the horizontal screw of a traversing screw jack. draw the two views shown, and from one of them project a plan. scale full size. exercise 73: _steam whistle._--draw, full size, the elevation and section of the steam whistle shown in fig. 71. draw also horizontal sections at a b, c d, and e f. [illustration: fig. 75.] exercise 74: _screw coupling for railway carriages._--draw the three views of the screw coupling shown in fig. 72. scale 6 inches to a foot. if the link a is fixed, through what distance will the link b move for two turns of the lever? [illustration: fig. 76.] exercise 75: _loose headstock for a 6-inch lathe._--two views of this headstock are shown in fig. 73. on one of these views a few of the chief dimensions are marked. the details, fully dimensioned, are shown separately in figs. 74, 75, and 76. explain clearly how the centre is moved backwards and forwards, and also how the spindle containing it is locked when it is not required to move. draw, half-size, the views shown in fig. 73, and from the left-hand view project a plan. draw also the detail of the locking arrangement shown in fig. 74. appendix a. _science and art department, south kensington._ syllabus. subject ii.--machine construction and drawing. it is assumed that the student has already learnt to draw to scale, and that he can draw two or more views of the same object in simple or orthographic projection. to pass in machine construction and drawing, he must be able to apply this knowledge to the representation of machinery. he must be acquainted with the form and purpose of the simpler parts of which machines are built up and must have had some practice in drawing them. to test his knowledge, rough dimensioned sketches, more or less incomplete, of simple machine details will be given him, and he will be required to produce a complete drawing in pencil to a given scale. two or more views of at least one subject will be required, and these must be so drawn as to be properly projected one from the other, _in order to show that the student appreciates that he is producing a representation of a solid piece of machinery, and not merely copying a sketch. no credit will be given unless some knowledge of projection is shown._ the centre lines of the drawings should be shown, and parts cut by planes of section should be indicated by diagonal shading. bolts and other fastenings should be carefully shown where required. any indication that a candidate has merely copied the sketches given, without understanding the part represented, will invalidate his examination. first stage or elementary course. in the elementary stage, a knowledge is required of the simple parts only of _machines in common use_. _some_ of these are enumerated in the following list. the student should be practised in drawing them till he recognises their forms, and the object of the arrangement should be explained to him. he should also know the simple technical terms used in describing them. a few very simple questions relating to the arrangement, proportions, and strength of the simplest machine details will be set in the examination paper. in drawing the examples set to test a student's knowledge and skill in machine drawing, it must be remembered that only a limited time is available. it is only possible to set an example to be drawn in pencil, and the points which will receive attention are (1) accuracy of scale and projection; (2) power of reading a drawing, shown by the ability to transfer portions of the mechanism and dimensions from one view to another; (3) knowledge of machines, as shown by the ability to fill in small details, such as nuts, keys, etc., omitted in the sketches given. bearing in mind the limited time available, the student should try to make his outline clear and decisive and complete. but the diagonal lines necessary for sectional parts may be done rapidly, though neatly, by freehand if necessary. _riveted joints._--forms of rivets and arrangement of rivets in lap and butt joints with single and double riveting. junction of plates by angle and t-irons. _bolts, studs, and set screws._--forms of these fastenings. forms and proportions of nuts and bolt-heads. arrangement of flanges for bolting. _pins, keys, and cotters._--form of ordinary knuckle joint. use of split pins. connection of parts by a key. connection of parts by a cotter. gib and cotter. _pipes and cylinders._--forms of ordinary pipes and cylinders and their flanges and covers. _shafting._--forms of shafts and axles and of journals and pivots. use of collars and bosses. half-lap coupling. box coupling. flange coupling. _pedestals and plummer blocks._--simplest forms of pedestals and hangers for shafts. form and arrangement of brass steps. arrangements for fixing pedestals and for neutralising the effects of wear. _toothed gearing._--forms of ordinary spur and bevil wheels. meaning of the terms pitch, breadth of face, thickness of tooth, pitch line, rim, nave, arm. mode of drawing bevil wheels in section. _belt pulleys._--forms of belt pulleys for flat and round belts. stepped speed cones. drawing of pulleys with curved arms. _cranks and levers._--forms of ordinary cast-iron and wrought-iron cranks and levers. modes of fixing crank pin. modes of fixing crank shaft. double cranks. form of eccentrics. _links._--most simple forms of connecting rod ends, open or closed. use of steps in connecting rods. use of cotters to tighten the steps. _pistons._--simple forms of piston. use of piston packing. modes of attaching piston rod. _stuffing-boxes._--simple form of stuffing-box and gland. use of packing. mode of tightening gland. _valves._--simple conical of puppet valve. simple slide valve. cock or conical sliding valve. appendix b. _examination papers set by the science and art department._ subject ii.--machine construction and drawing. _examiners_, prof. t. a. hearson, m.inst.c.e., and j. harrison, esq., m.inst.m.e. general instructions. _if the rules are not attended to, the paper will be cancelled._ you may take the elementary, or the advanced, or the honours paper, but you must confine yourself to one of them. put the number of the question before your answer. you are expected to prove your knowledge of machinery as well as your power of drawing neatly to scale. you are therefore to supply details omitted in the sketches, to fill in parts left incomplete, and to indicate, by diagonal lines, parts cut by planes of section. no credit will be given unless some knowledge of projection is shown, so that at least two views of one of the examples will be required properly projected one from the other. the centre lines should be clearly drawn. the figured dimensions need not be inserted. your answers should be clearly and cleanly drawn in pencil. no extra marks will be allowed for inking in. all figures must be drawn on the single sheet of paper supplied, for no second sheet will be allowed. the value attached to each question is shown in brackets after the question. but a full and correct answer to an easy question will in all cases secure a larger number of marks than an incomplete or inexact answer to a more difficult one. your name is not given to the examiner, and you are forbidden to write to him about your answers. you are to confine your answers _strictly_ to the questions proposed. a single accent (') signifies _feet_; a double accent (") _inches_. _the examination in this subject lasts for four hours._ * * * * * first stage or elementary examination. 1885. instructions. read the general instructions above. answer briefly any three, but not more than three, of the following questions, and draw two, but not more than two, of the examples. _questions._ (_a._) show two methods by which a cotter may be prevented from slacking back. (6.) (_b._) sketch the brasses for a bearing, and show how they are prevented from turning in the pedestal. (6.) (_c._) explain the object of the construction of the connecting rod end shown in fig. 78. describe how the adjustment must be made and how it is locked. (10.) (_d._) show the form of the whitworth screw thread by drawing to scale a part section of two or three threads taking a pitch of 1-1/2 inches. figure the dimensions on the sketch. how many threads to the inch are used on an inch bolt? (10.) (_e._) make a sketch showing how the adjustment is made in the sliding parts of machine tools: as, for example, in the slide rest of a lathe. (10.) (_f._) describe with sketches two methods by which the joints are made in connecting lengths of cast-iron pipes. (6.) _examples to be drawn._ 1. jaw for four-screw dog chuck for 5" lathe. draw the two views as shown (fig. 77). scale full size. (note.--the other three jaws of the chuck are not to be drawn.) (35.) 2. connecting rod end. draw the two views as shown, partly in section (fig. 78). draw full size. (35.) 3. hooke's coupling. draw the three views shown (fig. 79), adding any omitted lines where the views are incomplete. draw to scale of 1/4 full size. (35.) [illustration: figs. 77 and 78.] [illustration: fig. 79.] * * * * * first stage or elementary examination. 1886. instructions. read the general instructions (page 102). answer briefly any three, but not more than three, of the following questions, and draw two, but not more than two, of the examples. _questions._ (_a._) give sketches showing how the cutting tool of a lathe or other machine is secured in place. (6.) (_b._) make a sketch of a stud, describe how it is screwed into place, and state some circumstances under which it is used in preference to a bolt. (6.) (_c._) give sketches showing one method of attaching the valve rod to an ordinary slide valve. (6.) (_d._) sketch a connecting rod end, with strap, gib, and cotter. explain the use of the gib. (10.) (_e._) explain the use of the quadrant for change wheels for a screw-cutting lathe shown in example 1, fig. 80, by making a sketch showing it in place on a lathe with wheels in gear. (10.) (_f._) sketch one form of hanger suitable for supporting mill-shafting. (10.) _examples to be drawn._ 1. quadrant for change wheels for screw-cutting lathe. draw the two views shown (fig. 80). scale half-size. (35.) 2. crank-shaft. draw the two views as shown, partly in section (fig 81). scale 1/8 full size. (35.) 3. ball bearing for tricycle. draw the two views as shown, partly in section (fig. 82). draw full size. (35.) [illustration: figs. 80 and 81.] [illustration: fig. 82.] * * * * * first stage or elementary examination. 1887. instructions. read the general instructions (page 102). answer briefly any three, but not more than three, of the following questions, and draw two, but not more than two, of the examples. _questions._ (_a._) explain how the piston rings in example 1, fig. 84, are made so that the piston may work steam-tight in the cylinder. how are these rings got into place? (8.) (_b._) give two views of a double riveted lap joint for boiler-plates. (8.) (_c._) show by sketches how a wheel is fixed on a shaft by means of a sunk key. explain how the key may be withdrawn when it cannot be driven from the point end. (8.) (_d._) give sketches showing the construction of a conical metal lift or puppet valve and seating. (10.) (_e._) with the aid of sketches explain how a piston rod is made to work steam-tight through the end of the cylinder. (10.) (_f._) explain how the slotting machine ram of example 8, fig. 85, may be made to move up and down when at work. how is the length of the stroke altered, and what is the object of the slotway in the upper part of the ram? (10.) _examples to be drawn._ 1. piston for steam-engine. draw and complete the two views shown (fig. 84), the top half of the left-hand view to be in section. scale 1/2 size. (30.) 2. plan and sectional elevation of a footstep bearing for an upright shaft (fig. 83). draw and complete these views. scale 1/4 size. (35.) 3. ram of slotting machine. draw and complete the two elevations shown (fig. 85). the tool-holders must be drawn in their proper positions in the ram, and not separate as in the diagram. scale 1/4 size. (35.) [illustration: figs. 83 and 84.] [illustration: fig. 85.] * * * * * first stage or elementary examination. 1888. instructions. read the general instructions on p. 102. answer briefly any three, but not more than three, of the following questions, and draw two, but not more than two, of the examples. _questions._ (_a._) give sketches showing how the separate lengths of a line of shafting may be connected together. (8.) (_b._) what is the object of using chipping or facing strips in fitting up machine parts? give one or two examples. (8.) (_c._) give sketches showing how you would grip and drive a round iron bar for the purpose of turning it between the centres of a lathe. (10.) (_d._) explain the action of the governor shown in example 1 (fig. 86). (10.) (_e._) describe in detail how the mud-hole door in example 2 (fig. 88) is removed for the purpose of cleaning the boiler and how it is replaced and the joint made steam-tight. (10.) (_f._) describe how the parts of the spur wheel in example 3 (fig. 87) are put together, and explain why the wheel is made in segments. (10.) _examples to be drawn._ 1. loaded governor for small gas engine. draw and complete the two views, partly in section as shown (fig. 86). scale full size. (35.) 2. mud-hole mouth-piece for lancashire boiler. draw and complete the two views shown (fig. 88). scale 3/8ths. (35.) 3. point for segments of large spur wheel. draw and complete the views shown (fig. 87). scale 3/16ths. _note._--as the radius of the wheel is too large for your instruments, the circumference at the joint may be set out straight, as in a rack. (35.) [illustration: figs. 86 and 87.] [illustration: fig. 88.] index air-pump bucket, 58 alloys, 80 angle irons, 12 annealing, 79, 80 axles, 24 back stay for lathe, 86 bar stay, 83 bearings for shafts, 30 beech-wood, 81 bell crank lever, 86 bessemer steel, 79 bevil wheels, 43 blister steel, 79 blooms, 78 bolt-heads, proportions of, 18 bolts, forms of, 17 border lines, 4 box couplings, 25 -end, connecting rod, 51 box-wood, 81 brackets, 33 brake shaft carrier, 30 brass, 80 brasses, 30 bucket, 58 built-up cranks, 46 bush, 30, 49, 51, 54, 56, 63 butt joints, 10, 11 -strap, 10 buttress screw thread, 15 case-hardening, 80 cast iron, 76 cast iron flange coupling, 28, 29 -steel, 79 caulking, 8 cementation process, 79 centre lines, 2, 4 chilled castings, 78 circulating pump piston, 58 clearance, cylinder, 74 -of cotter, 49 cocks, 74 cogs, 41 -wood for, 81 collared stud, 18 collars, 24 colouring, 3 colours for different materials, 3 compasses, 1 cone keys, 23, 38 conical disc valve, 70, 71, 89 -head, 7 connecting rod, locomotive, 51 --marine, 51 -rods, 49, 89 construction for rivet heads, 7 contraction of castings, 77 copper, 80 cotters, 48, 49 countersunk head, 7, 18 coupling rod ends, 55, 84 -rods, 54 -screw, 96 couplings, shaft, 25 cover plate, 10 cranked axle, 45 cranks, 43 -built-up, 46 cross-head pin, 51 cross-heads, 56, 89 cross-key, 28 cup-headed bolt, 17 decimal equivalents, 6 dimension lines, 5 dimensions, 5 -of box couplings, 26 -cast-iron flange couplings, 29 -keys, 24 -stuffing-boxes and glands, 67 -whitworth screws, 15 distance lines, 5 dividers, 1 draught of cotter, 49 drawing board, 1 -instruments, 1 -paper, 2 -pen, 1 -pins, 2 eccentrics, 47 exhaust port, 71 eye-bolt, 18 fairbairn's coupling, 26 fast and loose pulleys, 37 feather key, 23 flange couplings, 27 flap valves, 68 flat key, 22 forge irons, 77 forging, 79 form of wheel teeth, 40 forms of nuts, 16 -rivet heads, 7 -screw threads, 15 foundry irons, 77 gasket, 58 gas threads, 15 gib, 49 -head, 23 girder stay, 81 gland, 64 grey cast iron, 77 gun-metal, 80 gusset stay, 12 half-lap coupling, 26 hangers, 34 hardening of steel, 80 headstock lathe, 96 hexagonal nut, 16 hollow key, 22 hook bolt, 18 hornbeam, 81 india-rubber disc valves, 58, 68 inking drawings, 2 inside lap of valve, 72 joggles, 33 joint, knuckle, 84 journals, 24 -length of, 32 junk ring, 61 keys, 22 -proportions of, 23 kinghorn's metallic valve, 70 knuckle joint, 84 -screw thread, 15 lancaster's piston packing, 61 lap joints, 8, 9, 10, 12 -of slide valve, 72 lathe headstock, 96 lead of valve, 74 lever, bell crank, 86 -ratchet, 96 lignum-vitæ, 81 locking arrangements for nuts, 21, 62 lock nuts, 19 locomotive connecting rod, 51 -cranked axle, 45 -cross-head, 56 locomotive eccentric, 47 -piston, 60 lubricator, needle, 32 malleable cast iron, 78 -iron, 78 marine connecting rod, 51 -coupling, 28 -crank-shaft, 46 -piston, 61 merchant bars, 78 mortise wheels, 41 mottled cast iron, 77 muff couplings, 25 muntz metal, 80 needle lubricator, 32 nuts, forms of, 16 -lock, 19 -proportions of, 18 oil-box, 54, 65 outside lap of slide valve, 72 overhung crank, 43 -cranks, proportions of, 45 packing, 63 pan head, 7 pedestal, shaft, 30 pencils, drawing, 1 phosphor bronze, 80 pillar bracket, 34 pillow block, 30, 32 pin, cross-head, 51, 54 -split, 21 piston rod, 57 pistons, 57 pitch circle, 40 -of wheel teeth, 40 -surfaces of wheels, 39, 43 pivots, 24 plummer block, 30 plunger, 57 printing, 4 proportions of bolt-heads, 18 -keys, 23 proportions of lap joints, 9, 10 -marine engine pistons, 62 -nuts, 18 -overhung cranks, 45 -pillow blocks, 32 -rivet heads, 7 -wheel teeth, 40 puddled bars, 78 puddling process, 78 pulley, eccentric, 47 pulleys, 36 pump bucket, 58 ramsbottom's packing, 60 ratchet lever, 96 riveted joints, 8 rivet heads, forms of, 7, 8 --proportions of, 7 riveting, 7 rivets, 6 rope pulley, 39 round key, 23 saddle key, 22 scales, 5 screw coupling, 96 screwed gland and stuffing-box, 65 screw threads, 14, 15 screws, representation of, 16 sellers =v= screw thread, 14 set screw, 21, 49 -squares, 1 shaft couplings, 25 -hanger, 34 shafting, 24 shear steel, 79 sheave, eccentric, 47 shingling, 78 shrinking, process of, 44 siemens-martin steel, 79 slide blocks, 56 -valves, 68, 71 sliding key, 23 snap head, 7 snug, 17 spiegeleisen, 80 spring bows, 1 spur wheel, 41 square nut, 16 -screw thread, 14 stay, back, for lathe, 86 -bar, 83 -girder, 81 -gusset, 12 steam ports, 71 -whistle, 96 steel, 79 steps, 30 strap, 49 -eccentric, 47 -end of connecting rod, 49 stud bolts, 18 studs, 18 stuffing-boxes, 63 sunk key, 22 taper bolt, 18, 27 -pin, 23 tee-headed bolt, 18 tee-iron cover strap, 81 tee square, 1 teeth of wheels, form and proportions of, 40 teeth, pitch of, 40 tempering of steel, 80 throw of crank, 44 -eccentric, 47 toothed wheels, 39 valve kinghorn's metallic, 70 -slide, 68, 71 valves, 68 -conical disc, 70 -india-rubber, 58, 68 velocity ratio in belt gearing, 36 wall boxes, 34 washers, 19 welding, 79 whistle, steam, 96 white cast iron, 77 whitworth screws, dimensions of, 15 -=v= screw thread, 14 wood, 81 working drawings, 4 wrought iron, 78 yellow pine, 81 printed by spottiswoode and co., new-street square london * * * * * text-books of science photography. by captain w. de wiveleslie abney, c.b. f.r.s. late instructor in chemistry and photography at the school of military engineering, chatham. with 105 woodcuts. price 3_s._ 6_d._ the strength of materials and structures; the strength of materials as depending on their quality and as ascertained by testing apparatus; the strength of structures as depending on their form and arrangement, and on the materials of which they are composed. by sir j. anderson, c.e. &c. with 66 woodcuts. price 3_s._ 6_d._ introduction to the study of organic chemistry; the chemistry of carbon and its compounds. by henry e. armstrong ph.d. f.r.s. with 8 woodcuts. price 3_s._ 6_d._ elements of astronomy. by sir r. s. ball, ll.d. f.r.s. andrews professor of 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crown 8vo. 2_s._ 6_d._ steam. by william ripper, member of the institution of mechanical engineers. with 142 illustrations. crown 8vo. 2_s._ 6_d._ physics: alternative course. by mark r. wright. with 242 illustrations. crown 8vo. 2_s._ 6_d._ london: longmans, green, & co. transcriber's notes 1. passages in italics are surrounded by _underscores_. 2. mixed fractions are represented using hyphen and forward slash. for instance, five and a half is shown as 5-1/2. 3. obvious misprints in spelling and punctuation have been silently corrected. the voice of the machines an introduction to the twentieth century by gerald stanley lee the mount tom press northampton, massachusetts copyright, 1906 by the mount tom press to jennette lee ... "now and then my fancy caught a flying glimpse of a good life beyond- something of ships and sunlight, streets and singing, troy falling, and the ages coming back, and ages coming forward."... contents part i the men behind the machines i.--machines as seen from a meadow ii.--as seen through a hatchway iii.--the souls of machines iv.--poets v.--gentlemen vi.--prophets part ii the language of the machines i.--as good as ours ii.--on being busy and still iii.--on not showing off iv.--on making people proud of the world v.--a modest universe part iii the machines as poets i.--plato and the general electric works ii.--hewing away on the heavens and the earth iii.--the grudge against the infinite iv.--symbolism in modern art v.--the machines as artists vi.--the machines as philosophers part iv the ideas behind the machines i.--the idea of incarnation ii.--the idea of size iii.--the idea of liberty iv.--the idea of immortality v.--the idea of god vi.--the idea of the unseen and the intangible vii.--the idea of great men viii.--the idea of love and comradeship part one the men behind the machines i machines. as seen from a meadow it would be difficult to find anything in the encyclopedia that would justify the claim that we are about to make, or anything in the dictionary. even a poem--which is supposed to prove anything with a little of nothing--could hardly be found to prove it; but in this beginning hour of the twentieth century there are not a few of us--for the time at least allowed to exist upon the earth--who are obliged to say (with luther), "though every tile on the roundhouse be a devil, we cannot say otherwise--the locomotive is beautiful." as seen when one is looking at it as it is, and is not merely using it. as seen from a meadow. we had never thought to fall so low as this, or that the time would come when we would feel moved--all but compelled, in fact--to betray to a cold and discriminating world our poor, pitiful, one-adjective state. we do not know why a locomotive is beautiful. we are perfectly aware that it ought not to be. we have all but been ashamed of it for being beautiful--and of ourselves. we have attempted all possible words upon it--the most complimentary and worthy ones we know--words with the finer resonance in them, and the air of discrimination the soul loves. we cannot but say that several of these words from time to time have seemed almost satisfactory to our ears. they seem satisfactory also for general use in talking with people, and for introducing locomotives in conversation; but the next time we see a locomotive coming down the track, there is no help for us. we quail before the headlight of it. the thunder of its voice is as the voice of the hurrying people. our little row of adjectives is vanished. all adjectives are vanished. they are as one. unless the word "beautiful" is big enough to make room for a glorious, imperious, world-possessing, world-commanding beauty like this, we are no longer its disciples. it is become a play word. it lags behind truth. let it be shut in with its rim of hills--the word beautiful--its show of sunsets and its bouquets and its doilies and its songs of birds. we are seekers for a new word. it is the first hour of the twentieth century. if the hill be beautiful, so is the locomotive that conquers a hill. so is the telephone, piercing a thousand sunsets north to south, with the sound of a voice. the night is not more beautiful, hanging its shadow over the city, than the electric spark pushing the night one side, that the city may behold itself; and the hour is at hand--is even now upon us--when not the sun itself shall be more beautiful to men than the telegraph stopping the sun in the midst of its high heaven, and holding it there, while the will of a child to another child ticks round the earth. "time shall be folded up as a scroll," saith the voice of man, my brother. "the spaces between the hills, to me," saith the voice, "shall be as though they were not." the voice of man, my brother, is a new voice. it is the voice of the machines. ii as seen through a hatchway in its present importance as a factor in life and a modifier of its conditions, the machine is in every sense a new and unprecedented fact. the machine has no traditions. the only way to take a traditional stand with regard to life or the representation of life to-day, is to leave the machine out. it has always been left out. leaving it out has made little difference. only a small portion of the people of the world have had to be left out with it. not to see poetry in the machinery of this present age, is not to see poetry in the life of the age. it is not to believe in the age. the first fact a man encounters in this modern world, after his mother's face, is the machine. the moment be begins to think outwards, he thinks toward a machine. the bed he lies in was sawed and planed by a machine, or cast in a foundry. the windows he looks out of were built in mills. his knife and fork were made by steam. his food has come through rollers and wheels. the water he drinks is pumped to him by engines. the ice in it was frozen by a factory and the cloth of the clothes he wears was flashed together by looms. the machine does not end here. when he grows to years of discretion and looks about him to choose a place for himself in life, he finds that that place must come to him out of a machine. by the side of a machine of one sort or another, whether it be of steel rods and wheels or of human beings' souls, he must find his place in the great whirling system of the order of mortal lives, and somewhere in the system--that is, the machine--be the ratchet, drive-wheel, belt, or spindle under infinite space, ordained for him to be from the beginning of the world. the moment he begins to think, a human being finds himself facing a huge, silent, blue-and-gold something called the universe, the main fact of which must be to him that it seems to go without him very well, and that he must drop into the place that comes, whatever it may be, and hold on as he loves his soul, or forever be left behind. he learns before many years that this great machine shop of a globe, turning solemnly its days and nights, where he has wandered for a life, will hardly be inclined to stop--to wait perchance--to ask him what he wants to be, or how this life of his shall get itself said. he looks into the face of circumstance. (sometimes it is the fist of circumstance.) the face of circumstance is a silent face. it points to the machine. he looks into the faces of his fellow-men, hurrying past him night and day,--miles of streets of them. they, too, have looked into the face of circumstance. it pointed to the machine. they show it in their faces. some of them show it in their gait. the machine closes around him, with its vast insistent murmur, million-peopled and full of laughs and cries. he listens to it as to the roar of all being. he listens to the machine's prophet. "all men," says political economy, "may be roughly divided as attaching themselves to one or the other of three great classes of activity--production, consumption or distribution." the number of persons who are engaged in production outside of association with machinery, if they could be gathered together in one place, would be an exceedingly small and strange and uncanny band of human beings. they would be visited by all the world as curiosities. the number of persons who are engaged in distribution outside of association with machinery is equally insignificant. except for a few peddlers, distribution is hardly anything else but machinery. the number of persons who are engaged in consumption outside of association with machinery is equally insignificant. so far as consumption is concerned, any passing freight train, if it could be stopped and examined on its way to new york, would be found to be loaded with commodities, the most important part of which, from the coal up, have been produced by one set of machines to be consumed by another set of machines. so omnipresent and masterful and intimate with all existence have cogs and wheels and belts become, that not a civilized man could be found on the globe to-day, who, if all the machines that have helped him to live this single year of 1906 could be gathered or piled around him where he stands, would be able, for the machines piled high around his life, to see the sky--to be sure there was a sky. it is then his privilege, looking up at this horizon of steel and iron and running belts, to read in a paper book the literary definition of what this heaven is, that spreads itself above him, and above the world, walled in forever with its irrevocable roar of wheels. "no inspiring emotions," says the literary definition, "ideas or conceptions can possibly be connected with machinery--or ever will be." what is to become of a world roofed in with machines for the rest of its natural life, and of the people who will have to live under the roof of machines, the literary definition does not say. it is not the way of literary definitions. for a time at least we feel assured that we, who are the makers of definitions, are poetically and personally safe. can we not live behind the ramparts of our books? we take comfort with the medallions of poets and the shelves that sing around us. we sit by our library fires, the last nook of poetry. beside our gates the great crowding chimneys lift themselves. beneath our windows herds of human beings, flocking through the din, in the dark of the morning and the dark of the night, go marching to their fate. we have done what we could. have we not defined poetry? is it nothing to have laid the boundary line of beauty?... the huge, hurrying, helpless world in its belts and spindles--the people who are going to be obliged to live in it when the present tense has spoiled it a little more--all this--the great strenuous problem--the defense of beauty, the saving of its past, the forging of its future, the welding of it with life-all these?... pull down the blinds, jeems. shut out the noises of the street. a little longer ... the low singing to ourselves. then darkness. the wheels and the din above our graves shall be as the passing of silence. is it true that, in a few years more, if a man wants the society of his kind, he will have to look down through a hatchway? or that, if he wants to be happy, he will have to stand on it and look away? i do not know. i only know how it is now. they stay not in their hold these stokers, stooping to hell to feed a ship. below the ocean floors, before their awful doors bathed in flame, i hear their human lives drip--drip. through the lolling aisles of comrades in and out of sleep, troops of faces to and fro of happy feet, they haunt my eyes. their murky faces beckon me from the spaces of the coolness of the sea their fitful bodies away against the skies. iii souls of machines it does not make very much difference to the machines whether there is poetry in them or not. it is a mere abstract question to the machines. it is not an abstract question to the people who are under the machines. men who are under things want to know what the things are for, and they want to know what they are under them for. it is a very live, concrete, practical question whether there is, or can be, poetry in machinery or not. the fate of society turns upon it. there seems to be nothing that men can care for, whether in this world or the next, or that they can do, or have, or hope to have, which is not bound up, in our modern age, with machinery. with the fate of machinery it stands or falls. modern religion is a machine. if the characteristic vital power and spirit of the modern age is organization, and it cannot organize in its religion, there is little to be hoped for in religion. modern education is a machine. if the principle of machinery is a wrong and inherently uninspired principle--if because a machine is a machine no great meaning can be expressed by it, and no great result accomplished by it--there is little to be hoped for in modern education. modern government is a machine. the more modern a government is, the more the machine in it is emphasized. modern trade is a machine. it is made up of (1) corporations--huge machines employing machines, and (2) of trusts--huge machines that control machines that employ machines. modern charity is a machine for getting people to help each other. modern society is a machine for getting them to enjoy each other. modern literature is a machine for supplying ideas. modern journalism is a machine for distributing them; and modern art is a machine for supplying the few, very few, things that are left that other machines cannot supply. both in its best and worst features the characteristic, inevitable thing that looms up in modern life over us and around us, for better or worse, is the machine. we may whine poetry at it, or not. it makes little difference to the machine. we may not see what it is for. it has come to stay. it is going to stay until we do see what it is for. we cannot move it. we cannot go around it. we cannot destroy it. we are born in the machine. a man cannot move the place he is born in. we breathe the machine. a man cannot go around what he breathes, any more than he can go around himself. he cannot destroy what he breathes, even by destroying himself. if there cannot be poetry in machinery--that is if there is no beautiful and glorious interpretation of machinery for our modern life--there cannot be poetry in anything in modern life. either the machine is the door of the future, or it stands and mocks at us where the door ought to be. if we who have made machines cannot make our machines mean something, we ourselves are meaningless, the great blue-and-gold machine above our lives is meaningless, the winds that blow down upon us from it are empty winds, and the lights that lure us in it are pictures of darkness. there is one question that confronts and undergirds our whole modern civilization. all other questions are a part of it. can a machine age have a soul? if we can find a great hope and a great meaning for the machine-idea in its simplest form, for machinery itself--that is, the machines of steel and flame that minister to us--it will be possible to find a great hope for our other machines. if we cannot use the machines we have already mastered to hope with, the less we hope from our other machines--our spirit-machines, the machines we have not mastered--the better. in taking the stand that there is poetry in machinery, that inspiring ideas and emotions can be and will be connected with machinery, we are taking a stand for the continued existence of modern religion--(in all reverence) the god-machine; for modern education--the man-machine; for modern government--the crowd-machine; for modern art--the machine in which the crowd lives. if inspiring ideas cannot be connected with a machine simply because it is a machine, there is not going to be anything left in this modern world to connect inspiring ideas with. johnstown haunts me--the very memory of it. flame and vapor and shadow--like some huge, dim face of labor, it lifts itself dumbly and looks at me. i suppose, to some it is but a wraith of rusty vapor, a mist of old iron, sparks floating from a chimney, while a train sweeps past. but to me, with its spires of smoke and its towers of fire, it is as if a great door had been opened and i had watched a god, down in the wonder of real things--in the act of making an earth. i am filled with childhood--and a kind of strange, happy terror. i struggle to wonder my way out. thousands of railways--after this--bind johnstown to me; miles of high, narrow, steel-built streets--the whole world lifting itself mightily up, rolling itself along, turning itself over on a great steel pivot, down in pennsylvania--for its days and nights. i am whirled away from it as from a vision. i am as one who has seen men lifting their souls up in a great flame and laying down floors on a star. i have stood and watched, in the melting-down place, the making and the welding place of the bones of the world. it is the object of this present writing to search out a world--a world a man can live in. if he cannot live in this one, let him know it and make one. if he can, let him face it. if the word yes cannot be written across the world once more--written across this year of the world in the roar of its vast machines--we want to know it. we cannot quite see the word yes--sometimes, huddled behind our machines. but we hear it sometimes. we know we hear it. it is stammered to us by the machines themselves. iv poets when, standing in the midst of the huge machine-shop of our modern life, we are informed by the professor of poetics that machinery--the thing we do our living with--is inevitably connected with ideas practical and utilitarian--at best intellectual--that "it will always be practically impossible to make poetry out of it, to make it appeal to the imagination," we refer the question to the real world, to the real spirit we know exists in the real world. expectancy is the creed of the twentieth century. expectancy, which was the property of poets in the centuries that are now gone by, is the property to-day of all who are born upon the earth. the man who is not able to draw a distinction between the works of john milton and the plays of shakespeare, but who expects something of the age he lives in, comes nearer to being a true poet than any writer of verses can ever expect to be who does not expect anything of this same age he lives in--not even verses. expectancy is the practice of poetry. it is poetry caught in the act. though the whole world be lifting its voice, and saying in the same breath that poetry is dead, this same world is living in the presence of more poetry, and more kinds of poetry, than men have known on the earth before, even in the daring of their dreams. pessimism has always been either literary--the result of not being in the real world enough--or genuine and provincial--the result of not being in enough of the real world. if we look about in this present day for a suitable and worthy expectancy to make an age out of, or even a poem out of, where shall we look for it? in the literary definition? the historical argument? the minor poet? the poet of the new movement shall not be discovered talking with the doctors, or defining art in the schools, nor shall he be seen at first by peerers in books. the passer-by shall see him, perhaps, through the door of a foundry at night, a lurid figure there, bent with labor, and humbled with labor, but with the fire from the heart of the earth playing upon his face. his hands--innocent of the ink of poets, of the mere outsides of things--shall be beautiful with the grasp of the thing called life--with the grim, silent, patient creating of life. he shall be seen living with retorts around him, loomed over by machines--shadowed by weariness--to the men about him half comrade, half monk--going in and out among them silently, with some secret glory in his heart. if literary men--so called--knew the men who live with machines, who are putting their lives into them--inventors, engineers and brakemen--as well as they know shakespeare and milton and the club, there would be no difficulty about finding a great meaning--_i. e._, a great hope or great poetry--in machinery. the real problem that stands in the way of poetry in machinery is not literary, nor ã¦sthetic. it is sociological. it is in getting people to notice that an engineer is a gentleman and a poet. v gentlemen the truest definition of a gentleman is that he is a man who loves his work. this is also the truest definition of a poet. the man who loves his work is a poet because he expresses delight in that work. he is a gentleman because his delight in that work makes him his own employer. no matter how many men are over him, or how many men pay him, or fail to pay him, he stands under the wide heaven the one man who is master of the earth. he is the one infallibly overpaid man on it. the man who loves his work has the single thing the world affords that can make a man free, that can make him his own employer, that admits him to the ranks of gentlemen, that pays him, or is rich enough to pay him, what a gentleman's work is worth. the poets of the world are the men who pour their passions into it, the men who make the world over with their passions. everything that these men touch, as with some strange and immortal joy from out of them, has the thrill of beauty in it, and exultation and wonder. they cannot have it otherwise even if they would. a true man is the autobiography of some great delight mastering his heart for him, possessing his brain, making his hands beautiful. looking at the matter in this way, in proportion to the number employed there are more gentlemen running locomotives to-day than there are teaching in colleges. in proportion as we are more creative in creating machines at present than we are in creating anything else there are more poets in the mechanical arts than there are in the fine arts; and while many of the men who are engaged in the machine-shops can hardly be said to be gentlemen (that is, they would rather be preachers or lawyers), these can be more than offset by the much larger proportion of men in the fine arts, who, if they were gentlemen in the truest sense, would turn mechanics at once; that is, they would do the thing they were born to do, and they would respect that thing, and make every one else respect it. while the definition of a poet and a gentleman--that he is a man who loves his work--might appear to make a new division of society, it is a division that already exists in the actual life of the world, and constitutes the only literal aristocracy the world has ever had. it may be set down as a fundamental principle that, no matter how prosaic a man may be, or how proud he is of having been born upon this planet with poetry all left out of him, it is the very essence of the most hard and practical man that, as regards the one uppermost thing in his life, the thing that reveals the power in him, he is a poet in spite of himself, and whether he knows it or not. so long as the thing a man works with is a part of an inner ideal to him, so long as he makes the thing he works with express that ideal, the heat and the glow and the lustre and the beauty and the unconquerableness of that man, and of that man's delight, shall be upon all that he does. it shall sing to heaven. it shall sing to all on earth who overhear heaven. every man who loves his work, who gets his work and his ideal connected, who makes his work speak out the heart of him, is a poet. it makes little difference what he says about it. in proportion as he has power with a thing; in proportion as he makes the thing--be it a bit of color, or a fragment of flying sound, or a word, or a wheel, or a throttle--in proportion as he makes the thing fulfill or express what he wants it to fulfill or express, he is a poet. all heaven and earth cannot make him otherwise. that the inventor is in all essential respects a poet toward the machine that he has made, it would be hard to deny. that, with all the apparent prose that piles itself about his machine, the machine is in all essential respects a poem to him, who can question? who has ever known an inventor, a man with a passion in his hands, without feeling toward him as he feels toward a poet? is it nothing to us to know that men are living now under the same sky with us, hundreds of them (their faces haunt us on the street), who would all but die, who are all but dying now, this very moment, to make a machine live,--martyrs of valves and wheels and of rivets and retorts, sleepless, tireless, unconquerable men? to know an inventor the moment of his triumph,--the moment when, working his will before him, the machine at last, resistless, silent, massive pantomime of a life, offers itself to the gaze of men's souls and the needs of their bodies,--to know an inventor at all is to know that at a moment like this a chord is touched in him strange and deep, soft as from out of all eternity. the melody that homer knew, and that dante knew, is his also, with the grime upon his hands, standing and watching it there. it is the same song that from pride to pride and joy to joy has been singing through the hearts of the men who make, from the beginning of the world. the thing that was not, that now is, after all the praying with his hands ... iron and wood and rivet and cog and wheel--is it not more than these to him standing before it there? it is the face of matter--who does not know it?--answering the face of the man, whispering to him out of the dust of the earth. what is true of the men who make the machines is equally true of the men who live with them. the brakeman and the locomotive engineer and the mechanical engineer and the sailor all have the same spirit. their days are invested with the same dignity and aspiration, the same unwonted enthusiasm, and self-forgetfulness in the work itself. they begin their lives as boys dreaming of the track, or of cogs and wheels, or of great waters. as i stood by the track the other night, michael the switchman was holding the road for the nine o'clock freight, with his faded flag, and his grim brown pipe, and his wooden leg. as it rumbled by him, headlight, clatter, and smoke, and whirl, and halo of the steam, every brakeman backing to the wind, lying on the air, at the jolt of the switch, started, as at some greeting out of the dark, and turned and gave the sign to michael. all of the brakemen gave it. then we watched them, michael and i, out of the roar and the hiss of their splendid cloud, their flickering, swaying bodies against the sky, flying out to the night, until there was nothing but a dull red murmur and the falling of smoke. michael hobbled back to his mansion by the rails. he put up the foot that was left from the wreck, and puffed and puffed. he had been a brakeman himself. brakemen are prosaic men enough, no doubt, in the ordinary sense, but they love a railroad as shakespeare loved a sonnet. it is not given to brakemen, as it is to poets, to show to the world as it passes by that their ideals are beautiful. they give their lives for them,--hundreds of lives a year. these lives may be sordid lives looked at from the outside, but mystery, danger, surprise, dark cities, and glistening lights, roar, dust, and water, and death, and life,--these play their endless spell upon them. they love the shining of the track. it is wrought into the very fibre of their being. years pass and years, and still more years. who shall persuade the brakemen to leave the track? they never leave it. i shall always see them--on their flying footboards beneath the sky--swaying and rocking--still swaying and rocking--to eternity. they are men who live down through to the spirit and the poetry of their calling. it is the poetry of the calling that keeps them there. most of us in this mortal life are allowed but our one peephole in the universe, that we may see it withal; but if we love it enough and stand close to it enough, we breathe the secret and touch in our lives the secret that throbs through it all. for a man to have an ideal in this world, for a man to know what an ideal is, even though nothing but a wooden leg shall come of it, and a life in a switch-house, and the signal of comrades whirling by, this also is to have lived. the fact that the railroad has the same fascination for the railroad man that the sea has for the sailor is not a mere item of interest pertaining to human nature. it is a fact that pertains to the art of the present day, and to the future of its literature. it is as much a symbol of the art of a machine age as the man ulysses is a symbol of the art of an heroic age. that it is next to impossible to get a sailor, with all his hardships, to turn his back upon the sea is a fact a great many thousand years old. we find it accounted for not only in the observation and experience of men, but in their art. it was rather hard for them to do it at first (as with many other things), but even the minor poets have admitted the sea into poetry. the sea was allowed in poetry before mountains were allowed in it. it has long been an old story. when the sailor has grown too stiff to climb the masts he mends sails on the decks. everybody understands--even the commonest people and the minor poets understand--why it is that a sailor, when he is old and bent and obliged to be a landsman to die, does something that holds him close to the sea. if he has a garden, he hoes where he can see the sails. if he must tend flowers, he plants them in an old yawl, and when he selects a place for his grave, it is where surges shall be heard at night singing to his bones. every one appreciates a fact like this. there is not a passenger on the empire state express, this moment, being whirled to the west, who could not write a sonnet on it,--not a man of them who could not sit down in his seat, flying through space behind the set and splendid hundred-guarding eyes of the engineer, and write a poem on a dead sailor buried by the sea. a crowd on the street could write a poem on a dead sailor (that is, if they were sure he was dead), and now that sailors enough have died in the course of time to bring the feeling of the sea over into poetry, sailors who are still alive are allowed in it. it remains to be seen how many wrecks it is going to take, lists of killed and wounded, fatally injured, columns of engineers dying at their posts, to penetrate the spiritual safe where poets are keeping their souls to-day, untouched of the world, and bring home to them some sense of the adventure and quiet splendor and unparalleled expressiveness of the engineer's life. he is a man who would rather be without a life (so long as he has his nerve) than to have to live one without an engine, and when he climbs down from the old girl at last, to continue to live at all, to him, is to linger where she is. he watches the track as a sailor watches the sea. he spends his old age in the roundhouse. with the engines coming in and out, one always sees him sitting in the sun there until he dies, and talking with them. nothing can take him away. does any one know an engineer who has not all but a personal affection for his engine, who has not an ideal for his engine, who holding her breath with his will does not put his hand upon the throttle of that ideal and make that ideal say something? woe to the poet who shall seek to define down or to sing away that ideal. in its glory, in darkness or in day, we are hid from death. it is the protection of life. the engineer who is not expressing his whole soul in his engine, and in the aisles of souls behind him, is not worthy to place his hand upon an engine's throttle. indeed, who is he--this man--that this awful privilege should be allowed to him, that he should dare to touch the motor nerve of her, that her mighty forty-mile-an-hour muscles should be the slaves of the fingers of a man like this, climbing the hills for him, circling the globe for him? it is impossible to believe that an engineer--a man who with a single touch sends a thousand tons of steel across the earth as an empty wind can go, or as a pigeon swings her wings, or as a cloud sets sail in the west--does not mean something by it, does not love to do it because he means something by it. if ever there was a poet, the engineer is a poet. in his dumb and mighty, thousand-horizoned brotherhood, hastener of men from the ends of the earth that they may be as one, i always see him,--ceaseless--tireless--flying past sleep--out through the night--thundering down the edge of the world, into the dawn. who am i that it should be given to me to make a word on my lips to speak, or to make a thing that shall be beautiful with my hands--that i should stand by my brother's life and gaze on his trembling track--and not feel what the engine says as it plunges past, about the man in the cab? what matters it that he is a wordless man, that he wears not his heart in a book? are not the bell and the whistle and the cloud of steam, and the rush, and the peering in his eyes words enough? they are the signals of this man's life beckoning to my life. standing in his engine there, making every wheel of that engine thrill to his will, he is the priest of wonder to me, and of the terror of the splendor of the beauty of power. the train is the voice of his life. the sound of its coming is a psalm of strength. it is as the singing a man would sing who felt his hand on the throttle of things. the engine is a soul to me--soul of the quiet face thundering past--leading its troop of glories echoing along the hills, telling it to the flocks in the fields and the birds in the air, telling it to the trees and the buds and the little, trembling growing things, that the might of the spirit of man has passed that way. if an engine is to be looked at from the point of view of the man who makes it and who knows it best; if it is to be taken, as it has a right to be taken, in the nature of things, as being an expression of the human spirit, as being that man's way of expressing the human spirit, there shall be no escape for the children of this present world, from the wonder and beauty in it, and the strong delight in it that shall hem life in, and bound it round on every side. the idealism and passion and devotion and poetry in an engineer, in the feeling he has about his machine, the power with which that machine expresses that feeling, is one of the great typical living inspirations of this modern age, a fragment of the new apocalypse, vast and inarticulate and far and faint to us, but striving to reach us still, now from above, and now from below, and on every side of life. it is as though the very ground itself should speak,--speak to our poor, pitiful, unspiritual, matter-despising souls,--should command them to come forth, to live, to gaze into the heart of matter for the heart of god. it is so that the very dullest of us, standing among our machines, can hardly otherwise than guess the coming of some vast surprise,--the coming of the day when, in the very rumble of the world, our sons and daughters shall prophesy, and our young men shall see visions, and our old men shall dream dreams. it cannot be uttered. i do not dare to say it. what it means to our religion and to our life and to our art, this great athletic uplift of the world, i do not know. i only know that so long as the fine arts, in an age like this, look down on the mechanical arts there shall be no fine arts. i only know that so long as the church worships the laborer's god, but does not reverence labor, there shall be no religion in it for men to-day, and none for women and children to-morrow. i only know that so long as there is no poet amongst us, who can put himself into a word, as this man, my brother the engineer, is putting himself into his engine, the engine shall remove mountains, and the word of the poet shall not; it shall be buried beneath the mountains. i only know that so long as we have more preachers who can be hired to stop preaching or to go into life insurance than we have engineers who can be hired to leave their engines, inspiration shall be looked for more in engine cabs than in pulpits,--the vestibule trains shall say deeper things than sermons say. in the rhythm of the anthem of them singing along the rails, we shall find again the worship we have lost in church, the worship we fain would find in the simpered prayers and paid praises of a thousand choirs,--the worship of the creative spirit, the beholding of a fragment of creation morning, the watching of the delight of a man in the delight of god,--in the first and last delight of god. i have made a vow in my heart. i shall not enter a pulpit to speak, unless every word have the joy of god and of fathers and mothers in it. and so long as men are more creative and godlike in engines than they are in sermons, i listen to engines. would to god it were otherwise. but so it shall be with all of us. so it cannot but be. not until the day shall come when this wistful, blundering church of ours, loved with exceeding great and bitter love, with all her proud and solitary towers, shall turn to the voices of life sounding beneath her belfries in the street, shall she be worshipful; not until the love of all life and the love of all love is her love, not until all faces are her faces, not until the face of the engineer peering from his cab, sentry of a thousand souls, is beautiful to her, as an altar cloth is beautiful or a stained glass window is beautiful, shall the church be beautiful. that day is bound to come. if the church will not do it with herself, the great rough hand of the world shall do it with the church. that day of the new church shall be known by men because it will be a day in which all worship shall be gathered into her worship, in which her holy house shall be the comradeship of all delights and of all masteries under the sun, and all the masteries and all the delights shall be laid at her feet. vi prophets the world follows the creative spirit. where the spirit is creating, the strong and the beautiful flock. if the creative spirit is not in poetry, poetry will call itself something else. if it is not in the church, religion will call itself something else. it is the business of a living religion, not to wish that the age it lives in were some other age, but to tell what the age is for, and what every man born in it is for. a church that can see only what a few of the men born in an age are for, can help only a few. if a church does not believe in a particular man more than he believes in himself, the less it tries to do for him the better. if a church does not believe in a man's work as he believes in it, does not see some divine meaning and spirit in it and give him honor and standing and dignity for the divine meaning in it; if it is a church in which labor is secretly despised and in which it is openly patronized, in which a man has more honor for working feebly with his brain than for working passionately and perfectly with his hands, it is a church that stands outside of life. it is excommunicated by the will of heaven and the nature of things, from the only communion that is large enough for a man to belong to or for a god to bless. if there is one sign rather than another of religious possibility and spiritual worth in the men who do the world's work with machines to-day, it is that these men are never persuaded to attend a church that despises that work. symposiums on how to reach the masses are pitiless irony. there is no need for symposiums. it is an open secret. it cries upon the house-tops. it calls above the world in the sabbath bells. a church that believes less than the world believes shall lose its leadership in the world. "why should i pay pew rent," says the man who sings with his hands, "to men who do not believe in me, to worship, with men who do not believe in me, a god that does not believe in me?" if heaven itself (represented as a rich and idle place,--seats free in the evening) were opened to the true laboring man on the condition that he should despise his hands by holding palms in them, he would find some excuse for staying away. he feels in no wise different with regard to his present life. "unless your god," says the man who sings with his hands, to those who pity him and do him good,--"unless your god is a god i can worship in a factory, he is not a god i care to worship in a church." behold it is written: the church that does not delight in these men and in what these men are for, as much as the street delights in them, shall give way to the street. the street is more beautiful. if the street is not let into the church, it shall sweep over the church and sweep around it, shall pile the floors of its strength upon it, above it. from the roofs of labor--radiant and beautiful labor--shall men look down upon its towers. only a church that believes more than the world believes shall lead the world. it always leads the world. it cannot help leading it. the religion that lives in a machine age, and that cannot see and feel, and make others see and feel, the meaning of that machine age, is a religion which is not worthy of us. it is not worthy of our machines. one of the machines we have made could make a better religion than this. even now, almost everywhere in almost every town or city where one goes, if one will stop or look up or listen, one hears the chimneys teaching the steeples. it would be blind for more than a few years more to be discouraged about modern religion. the telephone, the wireless telegraph, the x-rays, and all the other great believers are singing up around it. the very railroads are surrounding it and taking care of it. a few years more and the steeples will stop hesitating and tottering in the sight of all the people. they will no longer stand in fear before what the crowds of chimneys and railways and the miles of smokestacks sweeping past are saying to the people. they will listen to what the smokestacks are saying to the people. they will say it better. in the meantime they are not listening. religion and art at the present moment, both blindfolded and both with their ears stopped, are being swept to the same irrevocable issue. by all poets and prophets the same danger signal shall be seen spreading before them both jogging along their old highways. it is the arm that reaches across the age. railroad crossing look out for the engine! part ii. the language of the machines i as good as ours one is always hearing it said that if a thing is to be called poetic it must have great ideas in it, and must successfully express them. the idea that there is poetry in machinery, has to meet the objection that, while a machine may have great ideas in it, "it does not look it." the average machine not only fails to express the idea that it stands for, but it generally expresses something else. the language of the average machine, when one considers what it is for, what it is actually doing, is not merely irrelevant or feeble. it is often absurd. it is a rare machine which, when one looks for poetry in it, does not make itself ridiculous. the only answer that can be made to this objection is that a steam-engine (when one thinks of it) really expresses itself as well as the rest of us. all language is irrelevant, feeble, and absurd. we live in an organically inexpressible world. the language of everything in it is absurd. judged merely by its outer signs, the universe over our heads--with its cunning little stars in it--is the height of absurdity, as a self-expression. the sky laughs at us. we know it when we look in a telescope. time and space are god's jokes. looked at strictly in its outer language, the whole visible world is a joke. to suppose that god has ever expressed himself to us in it, or to suppose that he could express himself in it, or that any one can express anything in it, is not to see the point of the joke. we cannot even express ourselves to one another. the language of everything we use or touch is absurd. nearly all of the tools we do our living with--even the things that human beings amuse themselves with--are inexpressive and foolish-looking. golf and tennis and football have all been accused in turn, by people who do not know them from the inside, of being meaningless. a golf-stick does not convey anything to the uninitiated, but the bare sight of a golf-stick lying on a seat is a feeling to the one to whom it belongs, a play of sense and spirit to him, a subtle thrill in his arms. the same is true of a new fiery-red baby, which, considering the fuss that is made about it, to a comparative outsider like a small boy, has always been from the beginning of the world a ridiculous and inadequate object. a man could not possibly conceive, even if he gave all his time to it, of a more futile, reckless, hapless expression of or pointer to an immortal soul than a week-old baby wailing at time and space. the idea of a baby may be all right, but in its outer form, at first, at least, a baby is a failure, and always has been. the same is true of our other musical instruments. a horn caricatures music. a flute is a man rubbing a black stick with his lips. a trombone player is a monster. we listen solemnly to the violin--the voice of an archangel with a board tucked under his chin--and to girardi's 'cello--a whole human race laughing and crying and singing to us between a boy's legs. the eye-language of the violin has to be interpreted, and only people who are cultivated enough to suppress whole parts of themselves (rather useful and important parts elsewhere) can enjoy a great opera--a huge conspiracy of symbolism, every visible thing in it standing for something that can not be seen, beckoning at something that cannot be heard. nothing could possibly be more grotesque, looked at from the outside or by a tourist from another planet or another religion, than the celebration of the lord's supper in a protestant church. all things have their outer senses, and these outer senses have to be learned one at a time by being flashed through with inner ones. except to people who have tried it, nothing could be more grotesque than kissing, as a form of human expression. a reception--a roomful of people shouting at each other three inches away--is comical enough. so is handshaking. looked at from the outside, what could be more unimpressive than the spectacle of the greatest dignitary of the united states put in a vise in his own house for three hours, having his hand squeezed by long rows of people? and, taken as a whole, scurrying about in its din, what could possibly be more grotesque than a great city--a city looked at from almost any adequate, respectable place for an immortal soul to look from--a star, for instance, or a beautiful life? whether he is looked at by ants or by angels, every outer token that pertains to man is absurd and unfinished until some inner thing is put with it. man himself is futile and comic-looking (to the other animals), rushing empty about space. new york is a spectacle for a squirrel to laugh at, and, from the point of view of a mouse, a man is a mere, stupid, sitting-down, skull-living, desk-infesting animal. all these things being true of expression--both the expression of men and of god--the fact that machines which have poetry in them do not express it very well does not trouble me much. i do not forget the look of the first ocean-engine i ever saw--four or five stories of it; nor do i forget the look of the ocean-engine's engineer as in its mighty heart-beat he stood with his strange, happy, helpless "twelve thousand horse-power, sir!" upon his lips. that first night with my first engineer still follows me. the time seems always coming back to me again when he brought me up from his whirl of wheels in the hold to the deck of stars, and left me--my new wonder all stumbling through me--alone with them and with my thoughts. the engines breathe. no sound but cinders on the sails and the ghostly heave, the voice the wind makes in the mast- and dainty gales and fluffs of mist and smoking stars floating past- from night-lit funnels. in the wild of the heart of god i stand. time and space wheel past my face. forever. everywhere. i alone. beyond the here and there now and then of men, winds from the unknown round me blow blow to the unknown again. out in its solitude i hear the prow beyond the silence-crowded decks laughing and shouting at night, lashing the heads and necks of the lifted seas, that in their flight urge onward and rise and sweep and leap and sink to the very brink of heaven. timber and steel and smoke and sleep thousand-souled a quiver, a deadened thunder, a vague and countless creep through the hold, the weird and dusky chariot lunges on through fate. from the lookout watch of my soul's eyes above the houses of the deep their shadowy haunches fall and rise --o'er the glimmer-gabled roofs the flying of their hoofs, through the wonder and the dark where skies and waters meet the shimmer of manes and knees dust of seas... the sound of breathing, urge, confusion and the beat, the starlight beat soft and far and stealthy-fleet of the dim unnumbered trampling of their feet. ii on being busy and still one of the hardest things about being an inventor is that the machines (excepting the poorer ones) never show off. the first time that the phonograph (whose talking had been rumored of many months) was allowed to talk in public, it talked to an audience in metuchen, new jersey, and, much to mr. edison's dismay, everybody laughed. instead of being impressed with the real idea of the phonograph--being impressed because it could talk at all--people were impressed because it talked through its nose. the more modern a machine is, when a man stands before it and seeks to know it,--the more it expects of the man, the more it appeals to his imagination and his soul,--the less it is willing to appeal to the outside of him. if he will not look with his whole being at a twin-screw steamer, he will not see it. its poetry is under water. this is one of the chief characteristics of the modern world, that its poetry is under water. the old sidewheel steamer floundering around in the big seas, pounding the air and water both with her huge, showy paddles, is not so poetic-looking as the sailboat, and the poetry in the sailboat is not so obvious, so plainly on top, as in a gondola. people who do not admit poetry in machinery in general admit that there is poetry in a dutch windmill, because the poetry is in sight. a dutch windmill flourishes. the american windmill, being improved so much that it does not flourish, is supposed not to have poetry in it at all. the same general principle holds good with every machine that has been invented. the more the poet--that is, the inventor--works on it, the less the poetry in it shows. progress in a modern machine, if one watches it in its various stages, always consists in making a machine stop posing and get down to work. the earlier locomotive, puffing helplessly along with a few cars on its crooked rails, was much more fire-breathing, dragon-like and picturesque than the present one, and the locomotive that came next, while very different, was more impressive than the present one. every one remembers it,--the important-looking, bell-headed, woodpile-eating locomotive of thirty years ago, with its noisy steam-blowing habits and its ceaseless water-drinking habits, with its grim, spreading cowcatcher and its huge plug-hat--who does not remember it--fussing up and down stations, ringing its bell forever and whistling at everything in sight? it was impossible to travel on a train at all thirty years ago without always thinking of the locomotive. it shoved itself at people. it was always doing things--now at one end of the train and now at the other, ringing its bell down the track, blowing in at the windows, it fumed and spread enough in hauling three cars from boston to concord to get to chicago and back. it was the poetic, old-fashioned way that engines were made. one takes a train from new york to san francisco now, and scarcely knows there is an engine on it. all he knows is that he is going, and sometimes the going is so good he hardly knows that. the modern engines, the short-necked, pin-headed, large-limbed, silent ones, plunging with smooth and splendid leaps down their aisles of space--engines without any faces, blind, grim, conquering, lifting the world--are more poetic to some of us than the old engines were, for the very reason that they are not so poetic-looking. they are less showy, more furtive, suggestive, modern and perfect. in proportion as a machine is modern it hides its face. it refuses to look as poetic as it is; and if it makes a sound, it is almost always a sound that is too small for it, or one that belongs to some one else. the trolley-wire, lifting a whole city home to supper, is a giant with a falsetto voice. the large-sounding, the poetic-sounding, is not characteristic of the modern spirit. in so far as it exists at all in the modern age, either in its machinery or its poetry, it exists because it is accidental or left over. there was a deep bass steamer on the mississippi once, with a very small head of steam, which any one would have admitted had poetry in it--old-fashioned poetry. every time it whistled it stopped. iii on not showing off it is not true to say that the modern man does not care for poetry. he does not care for poetry that bears on--or for eloquent poetry. he cares for poetry in a new sense. in the old sense he does not care for eloquence in anything. the lawyer on the floor of congress who seeks to win votes by a show of eloquence is turned down. votes are facts, and if the votes are to be won, facts must be arranged to do it. the doctor who stands best with the typical modern patient is not the most agreeable, sociable, jogging-about man a town contains, like the doctor of the days gone by. he talks less. he even prescribes less, and the reason that it is hard to be a modern minister (already cut down from two hours and a half to twenty or thirty minutes) is that one has to practise more than one can preach. to be modern is to be suggestive and symbolic, to stand for more than one says or looks--the little girl with her loom clothing twelve hundred people. people like it. they are used to it. all life around them is filled with it. the old-fashioned prayer-meeting is dying out in the modern church because it is a mere specialty in modern life. the prayer-meeting recognizes but one way of praying, and people who have a gift for praying that way go, but the majority of people--people who have discovered that there are a thousand other ways of praying, and who like them better--stay away. when the telegraph machine was first thought of, the words all showed on the outside. when it was improved it became inner and subtle. the messages were read by sound. everything we have which improves at all improves in the same way. the exterior conception of righteousness of a hundred years ago--namely, that a man must do right because it is his duty--is displaced by the modern one, the morally thorough one--namely, that a man must do right because he likes it--do it from the inside. the more improved righteousness is, the less it shows on the outside. the more modern righteousness is, the more it looks like selfishness, the better the modern world likes it, and the more it counts. on the whole, it is against a thing rather than in its favor, in the twentieth century, that it looks large. time was when if it had not been known as a matter of fact that galileo discovered heaven with a glass three feet long, men would have said that it would hardly do to discover heaven with anything less than six hundred feet long. to the ancients, galileo's instrument, even if it had been practical, would not have been poetic or fitting. to the moderns, however, the fact that galileo's star-tool was three feet long, that he carried a new heaven about with him in his hands, was half the poetry and wonder of it. yet it was not so poetic-looking as the six-hundred-foot telescope invented later, which never worked. nothing could be more impressive than the original substantial r---typewriter. one felt, every time he touched a letter, as if he must have said a sentence. it was like saying things with pile-drivers. the machine obtruded itself at every point. it flourished its means and ends. it was a gesticulating machine. one commenced every new line with his foot. the same general principle may be seen running alike through machinery and through life. the history of man is traced in water-wheels. the overshot wheel belonged to a period when everything else--religion, literature, and art--was overshot. when, as time passed on, common men began to think, began to think under a little, the reformation came in--and the undershot wheel, as a matter of course. there is no denying that the overshot wheel is more poetic-looking--it does its work with twelve quarts of water at a time and shows every quart--but it soon develops into the undershot wheel, which shows only the drippings of the water, and the undershot wheel develops into the turbine wheel, which keeps everything out of sight--except its work. the water in the six turbine wheels at niagara has sixty thousand horses in it, but it is not nearly as impressive and poetic-looking as six turbine wheels' worth of water would be--wasted and going over the falls. the main fact about the modern man as regards poetry is, that he prefers poetry that has this reserved turbine-wheel trait in it. it is because most of the poetry the modern man gets a chance to see to-day is merely going over the falls that poetry is not supposed to appeal to the modern man. he supposes so himself. he supposes that a dynamo (forty street-cars on forty streets, flying through the dark) is not poetic, but its whir holds him, sense and spirit, spellbound, more than any poetry that is being written. the things that are hidden--the things that are spiritual and wondering--are the ones that appeal to him. the idle, foolish look of a magnet fascinates him. he gropes in his own body silently, harmlessly with the x-ray, and watches with awe the beating of his heart. he glories in inner essences, both in his life and in his art. he is the disciple of the x-ray, the defier of appearances. why should a man who has seen the inside of matter care about appearances, either in little things or great? or why argue about the man, or argue about the man's god, or quibble with words? perhaps he is matter. perhaps he is spirit. if he is spirit, he is matter-loving spirit, and if he is matter, he is spirit-loving matter. every time he touches a spiritual thing, he makes it (as god makes mountains out of sunlight) a material thing. every time he touches a material thing, in proportion as he touches it mightily he brings out inner light in it. he spiritualizes it. he abandons the glistening brass knocker--pleasing symbol to the outer sense--for a tiny knob on his porch door and a far-away tinkle in his kitchen. the brass knocker does not appeal to the spirit enough for the modern man, nor to the imagination. he wants an inner world to draw on to ring a door-bell with. he loves to wake the unseen. he will not even ring a door-bell if he can help it. he likes it better, by touching a button, to have a door-bell rung for him by a couple of metals down in his cellar chewing each other. he likes to reach down twelve flights of stairs with a thrill on a wire and open his front door. he may be seen riding in three stories along his streets, but he takes his engines all off the tracks and crowds them into one engine and puts it out of sight. the more a thing is out of the sight of his eyes the more his soul sees it and glories in it. his fireplace is underground. hidden water spouts over his head and pours beneath his feet through his house. hidden light creeps through the dark in it. the more might, the more subtlety. he hauls the whole human race around the crust of the earth with a vapor made out of a solid. he stops solids--sixty miles an hour--with invisible air. he photographs the tone of his voice on a platinum plate. his voice reaches across death with the platinum plate. he is heard of the unborn. if he speaks in either one of his worlds he takes two worlds to speak with. he will not be shut in with one. if he lives in either he wraps the other about him. he makes men walk on air. he drills out rocks with a cloud and he breaks open mountains with gas. the more perfect he makes his machines the more spiritual they are, the more their power hides itself. the more the machines of the man loom in human life the more they reach down into silence, and into darkness. their foundations are infinity. the infinity which is the man's infinity is their infinity. the machines grasp all space for him. they lean out on ether. they are the man's machines. the man has made them and the man worships with them. from the first breath of flame, burning out the secret of the dust to the last shadow of the dust--the breathless, soundless shadow of the dust, which he calls electricity--the man worships the invisible, the intangible. electricity is his prophet. it sums him up. it sums up his modern world and the religion and the arts of his modern world. out of all the machines that he has made the electric machine is the most modern because it is the most spiritual. the empty and futile look of a trolley wire does not trouble the modern man. it is his instinctive expression of himself. all the habits of electricity are his habits. electricity has the modern man's temperament--the passion of being invisible and irresistible. the electric machine fills him with brotherhood and delight. it is the first of the machines that he can not help seeing is like himself. it is the symbol of the man's highest self. his own soul beckons to him out of it. and the more electricity grows the more like the man it grows, the more spirit-like it is. the telegraph wire around the globe is melted into the wireless telegraph. the words of his spirit break away from the dust. they envelop the earth like ether, and human speech, at last, unconquerable, immeasurable, subtle as the light of stars,--fights its way to god. the man no longer gropes in the dull helpless ground or through the froth of heaven for the spirit. having drawn to him the x-ray, which makes spirit out of dust, and the wireless telegraph, which makes earth out of air, he delves into the deepest sea as a cloud. he strides heaven. he has touched the hem of the garment at last of electricity--the archangel of matter. iv on making people proud of the world religion consists in being proud of the creator. poetry is largely the same feeling--a kind of personal joy one takes in the way the world is made and is being made every morning. the true lover of nature is touched with a kind of cosmic family pride every time he looks up from his work--sees the night and morning, still and splendid, hanging over him. probably if there were another universe than this one, to go and visit in, or if there were an extra creator we could go to--some of us--and boast about the one we have, it would afford infinite relief among many classes of people--especially poets. the most common sign that poetry, real poetry, exists in the modern human heart is the pride that people are taking in the world. the typical modern man, whatever may be said or not said of his religion, of his attitude toward the maker of the world, has regular and almost daily habits of being proud of the world. in the twentieth century the best way for a man to worship god is going to be to realize his own nature, to recognize what he is for, and be a god, too. we believe to-day that the best recognition of god consists in recognizing the fact that he is not a mere god who does divine things himself, but a god who can make others do them. looked at from the point of view of a mere god who does divine things himself, an earthquake, for instance, may be called a rather feeble affair, a slight jar to a ball going ---miles an hour--a creator could do little less, if he gave a bare thought to it--but when i waked a few mornings ago and felt myself swinging in my own house as if it were a hammock, and was told that some men down in hazardville, connecticut, had managed to shake the planet like that, with some gunpowder they had made, i felt a new respect for messrs. ---and co. i was proud of man, my brother. does he not shake loose the force of gravity--make the very hand of god to tremble? to his thoughts the very hills, with their hearts of stone, make soft responses--when he thinks them. the corliss engine of machinery hall in '76, under its sky of iron and glass, is remembered by many people the day they saw it first as one of the great experiences of life. like some vast, titanic spirit, soul of a thousand, thousand wheels, it stood to some of us, in its mighty silence there, and wrought miracles. to one twelve-year-old boy, at least, the thought of the hour he spent with that engine first is a thought he sings and prays with to this day. his lips trembled before it. he sought to hide himself in its presence. why had no one ever taught him anything before? as he looks back through his life there is one experience that stands out by itself in all those boyhood years--the choking in his throat--the strange grip upon him--upon his body and upon his soul--as of some awful unseen hand reaching down space to him, drawing him up to its might. he was like a dazed child being held up before it--held up to an infinite fact, that he might look at it again and again. the first conception of what the life of man was like, of what it might be like, came to at least one immortal soul not from lips that he loved, or from a face behind a pulpit, or a voice behind a desk, but from a machine. to this day that corliss engine is the engine of dreams, the appeal to destiny, to the imagination and to the soul. it rebuilds the universe. it is the opportunity of beauty throughout life, the symbol of freedom, the freedom of men, and of the unity of nations, and of the worship of god. in silence--like the soft far running of the sky--it wrought upon him there; like some heroic human spirit, its finger on a thousand wheels, through miles of aisles, and crowds of gazers, it wrought. the beat and rhythm of it was as the beat and rhythm of the heart of man mastering matter, of the clay conquering god. like some wonder-crowded chorus its voices surrounded me. it was the first hearing of the psalm of life. the hum and murmur of it was like the spell of ages upon me; and the vision that floated in it--nay, the vision that was builded in it--was the vision of the age to be: the vision of man, my brother, after the singsong and dance and drone of his sad four thousand years, lifting himself to the stature of his soul at last, lifting himself with the sun, and with the rain, and with the wind, and the heat and the light, into comradeship with creation morning, and into something (in our far-off, wistful fashion) of the might and gentleness of god. there seem to be two ways to worship him. one way is to gaze upon the great machine that he has made, to watch it running softly above us all, moonlight and starlight, and winter and summer, rain and snowflakes, and growing things. another way is to worship him not only because he has made the vast and still machine of creation, in the beating of whose days and nights we live our lives, but because he has made a machine that can make machines--because out of the dust of the earth he has made a machine that shall take more of the dust of the earth, and of the vapor of heaven, crowd it into steel and iron and say, "go ye now, depths of the earth--heights of heaven--serve ye me. i, too, am god. stones and mists, winds and waters and thunder--the spirit that is in thee is my spirit. i also--even i also--am god!" v a modest universe i have heard it objected that a machine does not take hold of a man with its great ideas while he stands and watches it. it does not make him feel its great ideas. and therefore it is denied that it is poetic. the impressiveness of the bare spiritual facts of machinery is not denied. what seems to be lacking in the machines from the artistic point of view at present is a mere knack of making the faces plain and literal-looking. grasshoppers would be more appreciated by more people if they were made with microscopes on,--either the grasshoppers or the people. if the mere machinery of a grasshopper's hop could be made plain and large enough, there is not a man living who would not be impressed by it. if grasshoppers were made (as they might quite as easily have been) 640 feet high, the huge beams of their legs above their bodies towering like cranes against the horizon, the sublimity of a grasshopper's machinery--the huge levers of it, his hops across valleys from mountain to mountain, shadowing fields and villages--would have been one of the impressive features of human life. everybody would be willing to admit of the mere machinery of a grasshopper, (if there were several acres of it) that there was creative sublimity in it. they would admit that the bare idea of having such a stately piece of machinery in a world at all, slipping softly around on it, was an idea with creative sublimity in it; and yet these same people because the sublimity, instead of being spread over several acres, is crowded into an inch and a quarter, are not impressed by it. but it is objected, it is not merely a matter of spiritual size. there is something more than plainness lacking in the symbolism of machinery. "the symbolism of machinery is lacking in fitness. it is not poetic." "a thing can only be said to be poetic in proportion as its form expresses its nature." mechanical inventions may stand for impressive facts, but such inventions, no matter how impressive the facts may be, cannot be called poetic unless their form expresses those facts. a horse plunging and champing his bits on the eve of battle, for instance, is impressive to a man, and a pill-box full of dynamite, with a spark creeping toward it, is not. that depends partly on the man and partly on the spark. a man may not be impressed by a pill-box full of dynamite and a spark creeping toward it, the first time he sees it, but the second time he sees it, if he has time, he is impressed enough. he does not stand and criticise the lack of expression in pill-boxes, nor wait to remember the day when he all but lost his life because a pill-box by the river's brim a simple pill-box was to him and nothing more. wordsworth in these memorable lines has summed up and brought to an issue the whole matter of poetry in machinery. everything has its language, and the power of feeling what a thing means, by the way it looks, is a matter of experience--of learning the language. the language is there. the fact that the language of the machine is a new language, and a strangely subtle one, does not prove that it is not a language, that its symbolism is not good, and that there is not poetry in machinery. the inventor need not be troubled because in making his machine it does not seem to express. it is written that neither you nor i, comrade nor god, nor any man, nor any man's machine, nor god's machine, in this world shall express or be expressed. if it is the meaning of life to us to be expressed in it, to be all-expressed, we are indeed sorry, dumb, plaintive creatures dotting a star awhile, creeping about on it, warmed by a heater ninety-five million miles away. the machine of the universe itself, does not express its inventor. it does not even express the men who are under it. the ninety-five millionth mile waits on us silently, at the doorways of our souls night and day, and we wait on it. is it not there? is it not here--this ninety-five millionth mile? it is ours. it runs in our veins. why should man--a being who can live forever in a day, who is born of a boundless birth, who takes for his fireside the immeasurable--express or expect to be expressed? what we would like to be--even what we are--who can say? our music is an apostrophe to dumbness. the pantomime above us rolls softly, resistlessly on, over the pantomime within us. we and our machines, both, hewing away on the infinite, beckon and are still. i am not troubled because the machines do not seem to express themselves. i do not know that they can express themselves. i know that when the day is over, and strength is spent, and my soul looks out upon the great plain--upon the soft, night-blooming cities, with their huge machines striving in sleep, might lifts itself out upon me. i rest. i know that when i stand before a foundry hammering out the floors of the world, clashing its awful cymbals against the night, i lift my soul to it, and in some way--i know not how--while it sings to me i grow strong and glad. part three the machines as poets i plato and the general electric works i have an old friend who lives just around the corner from one of the main lines of travel in new england, and whenever i am passing near by and the railroads let me, i drop in on him awhile and quarrel about art. it's a good old-fashioned comfortable, disorderly conversation we have generally, the kind people used to have more than they do now--sketchy and not too wise--the kind that makes one think of things one wishes one had said, afterward. we always drift a little at first, as if of course we could talk about other things if we wanted to, but we both know, and know every time, that in a few minutes we shall be deep in a discussion of the things that are beautiful and the things that are not. brim thinks that i have picked out more things to be beautiful than i have a right to, or than any man has, and he is trying to put a stop to it. he thinks that there are enough beautiful things in this world that have been beautiful a long while, without having people--well, people like me, for instance, poking blindly around among all these modern brand-new things hoping that in spite of appearances there is something one can do with them that will make them beautiful enough to go with the rest. i'm afraid brim gets a little personal in talking with me at times and i might as well say that, while disagreeing in a conversation with brim does not lead to calling names it does seem to lead logically to one's going away, and trying to find afterwards, some thing that is the matter with him. "the trouble with you, my dear brim, is," i say (on paper, afterwards, as the train speeds away), "that you have a false-classic or stucco-greek mind. the greeks, the real greeks, would have liked all these things--trolley cars, cables, locomotives,--seen the beautiful in them, if they had to do their living with them every day, the way we do. you would say you were more greek than i am, but when one thinks of it, you are just going around liking the things the greeks liked 3000 years ago, and i am around liking the things a greek would like now, that is, as well as i can. i don't flatter myself i begin to enjoy the wireless telegraph to-day the way plato would if he had the chance, and alcibiades in an automobile would get a great deal more out of it, i suspect, than anyone i have seen in one, so far; and i suspect that if socrates could take bliss carman and, say, william watson around with him on a tour of the general electric works in schenectady they wouldn't either of them write sonnets about anything else for the rest of their natural lives." i can only speak for one and i do not begin to see the poetry in the machines that a greek would see, as yet. but i have seen enough. i have seen engineers go by, pounding on this planet, making it small enough, welding the nations together before my eyes. i have seen inventors, still men by lamps at midnight with a whirl of visions, with a whirl of thoughts, putting in new drivewheels on the world. i have seen (in schenectady,) all those men--the five thousand of them--the grime on their faces and the great caldrons of melted railroad swinging above their heads. i have stood and watched them there with lightning and with flame hammering out the wills of cities, putting in the underpinnings of nations, and it seemed to me me that bliss carman and william watson would not be ashamed of them ... brother-artists every one ... in the glory ... in the dark ... vulcan-tennysons, blacksmiths to a planet, with dredges, skyscrapers, steam shovels and wireless telegraphs, hewing away on the heavens and the earth. ii hewing away on the heavens and the earth the poetry of machinery to-day is a mere matter of fact--a part of the daily wonder of life to countless silent people. the next thing the world wants to know about machinery is not that there is poetry in it, but that the poetry which the common people have already found there, has a right to be there. we have the fact. it is the theory to put with the fact which concerns us next and which really troubles us most. there are very few of us, on the whole, who can take any solid comfort in a fact--no matter what it is--until we have a theory to approve of it with. its merely being a fact does not seem to make very much difference. 1. machinery has poetry in it because it is an expression of the soul. 2. it expresses the soul (1) of the individual man who creates the machine--the inventor, and (2) the man who lives with the machine the engineer. 3. it expresses god, if only that he is a god who can make men who can thus express their souls. machinery is an act of worship in the least sense if not in the greatest. if a man who can make machines like this is not clever enough with all his powers to find a god, and to worship a god, he can worship himself. it is because the poetry of machinery is the kind of poetry that does immeasurable things instead of immeasurably singing about them that it has been quite generally taken for granted that it is not poetry at all. the world has learned more of the purely poetic idea of freedom from a few dumb, prosaic machines that have not been able to say anything beautiful about it than from the poets of twenty centuries. the machine frees a hundred thousand men and smokes. the poet writes a thousand lines on freedom and has his bust in westminster abbey. the blacks in america were freed by abraham lincoln and the cotton gin. the real argument for unity--the argument against secession--was the locomotive. no one can fight the locomotive very long. it makes the world over into one world whether it wants to be one world or not. china is being conquered by steamships. it cannot be said that the idea of unity is a new one. seers and poets have made poetry out of it for two thousand years. machinery is making the poetry mean something. every new invention in matter that comes to us is a spiritual masterpiece. it is crowded with ideas. the bessemer process has more political philosophy in it than was ever dreamed of in shelley's poetry, and it would not be hard to show that the invention of the sewing machine was one of the most literary and artistic as well as one of the most religious events of the nineteenth century. the loom is the most beautiful thought that any one has ever had about woman, and the printing press is more wonderful than anything that has ever been said on it. "this is all very true," interrupts the logical person, "about printing presses and looms and everything else--one could go on forever--but it does not prove anything. it may be true that the loom has made twenty readers for robert browning's poetry where browning would have made but one, but it does not follow that because the loom has freed women for beauty that the loom is beautiful, or that it is a fit theme for poetry." "besides"--breaks in the minor poet--"there is a difference between a thing's being full of big ideas and its being beautiful. a foundry is powerful and interesting, but is it beautiful the way an electric fountain is beautiful or a sonnet or a doily?" this brings to a point the whole question as to where the definition of beauty--the boundary line of beauty--shall be placed. a thing's being considered beautiful is largely a matter of size. the question "is a thing beautiful?" resolves itself into "how large has a beautiful thing a right to be?" a man's theory of beauty depends, in a universe like this, upon how much of the universe he will let into it. if he is afraid of the universe if he only lets his thoughts and passions live in a very little of it, he is apt to assume that if a beautiful thing rises into the sublime and immeasurable--suggests boundless ideas--the beauty is blurred out of it. it is something--there is no denying that it is something--but, whatever it is or is not, it is not beauty. nearly everything in our modern life is getting too big to be beautiful. our poets are dumb because they see more poetry than their theories have room for. the fundamental idea of the poetry of machinery is infinity. our theories of poetry were made--most of them--before infinity was discovered. infinity itself is old, and the idea that infinity exists--a kind of huge, empty rim around human life--is not a new idea to us, but the idea that this same infinity has or can have anything to do with us or with our arts, or our theories of art, or that we have anything to do with it, is an essentially modern discovery. the actual experience of infinity--that is, the experience of being infinite (comparatively speaking)--as in the use of machinery, is a still more modern discovery. there is no better way perhaps, of saying what modern machinery really is, than to say that it is a recent invention for being infinite. the machines of the world are all practically engaged in manufacturing the same thing. they are all time-and-space-machines. they knit time and space. hundreds of thousands of things may be put in machines this very day, for us, before night falls, but only eternity and infinity shall be turned out. sometimes it is called one and sometimes the other. if a man is going to be infinite or eternal it makes little difference which. it is merely a matter of form whether one is everywhere a few years, or anywhere forever. a sewing machine is as much a means of communication as a printing press or a locomotive. the locomotive takes a woman around the world. the sewing machine gives her a new world where she is. at every point where a machine touches the life of a human being, it serves him with a new measure of infinity. this would seem to be a poetic thing for a machine to do. traditional poetry does not see any poetry in it, because, according to our traditions poetry has fixed boundary lines, is an old, established institution in human life, and infinity is not. no one has wanted to be infinite before. poetry in the ancient world was largely engaged in protecting people from the infinite. they were afraid of it. they could not help feeling that the infinite was over them. worship consisted in propitiating it, poetry in helping people to forget it. with the exception of job, the hebrews almost invariably employed a poet--when they could get one--as a kind of transfigured policeman--to keep the sky off. it was what was expected of poets. the greeks did the same thing in a different way. the only difference was, that the greeks, instead of employing their poets to keep the sky off, employed them to make it as much like the earth as possible--a kind of raised platform which was less dreadful and more familiar and homelike and answered the same general purpose. in other words, the sky became beautiful to the greek when he had made it small enough. making it small enough was the only way a greek knew of making it beautiful. galileo knew another way. it is because galileo knew another way--because he knew that the way to make the sky beautiful, was to make it large enough--that men are living in a new world. a new religion beats down through space to us. a new poetry lifts away the ceilings of our dreams. the old sky, with its little tent of stars, its film of flame and darkness burning over us, has floated to the past. the twentieth century--the home of the infinite--arches over our human lives. the heaven is no longer, to the sons of men, a priests' wilderness, nor is it a poet's heaven--a paper, painted heaven, with little painted paper stars in it, to hide the wilderness. it is a new heaven. who, that has lived these latter years, that has seen it crashing and breaking through the old one, can deny that what is over us now is a new heaven? the infinite cave of it, scooped out at last over our little naked, foolish lives, our running-about philosophies, our religions, and our governments--it is the main fact about us. arts and literatures--ants under a stone, thousands of years, blind with light, hither and thither, racing about, hiding themselves. but not long for dreams. more than this. the new heaven is matched by a new earth. men who see a new heaven make a new earth. in its cloud of steam, in a kind of splendid, silent stammer of praise and love, the new earth lifts itself to the new heaven, lifts up days out of nights to it, digs wells for winds under it, lights darkness with falling water, makes ice out of vapor, and heat out of cold, draws down space with engines, makes years out of moments with machines. it is a new world and all the men that are born upon it are new widemoving, cloud and mountain-moving men. the habits of stars and waters, the huge habits of space and time, are the habits of the men. the infinite, at last, which in days gone by hung over us--the mere hiding place of death, the awful living-room of god--is the neighborhood of human life. machinery has poetry in it because in expressing the soul it expresses the greatest idea that the soul of man can have, namely, the idea that the soul of man is infinite, or capable of being infinite. machinery has poetry in it also not merely because it is the symbol of infinite power in human life, or because it makes man think he is infinite, but because it is making him as infinite as he thinks he is. the infinity of man is no longer a thing that the poet takes--that he makes an idea out of--machinery makes it a matter of fact. iii the grudge against the infinite the main thing the nineteenth century has done in literature has been the gradual sorting out of poets into two classes--those who like the infinite, who have a fellow-feeling for it, and those who have not. it seems reasonable to say that the poets who have habits of infinity, of space-conquering (like our vast machines), who seek the suggestive and immeasurable in the things they see about them--poets who like infinity, will be the poets to whom we will have to look to reveal to us the characteristic and real poetry of this modern world. the other poets, it is to be feared, are not even liking the modern world, to say nothing of singing in it. they do not feel at home in it. the classic-walled poet seems to feel exposed in our world. it is too savagely large, too various and unspeakable and unfinished. he looks at the sky of it--the vast, unkempt, unbounded sky of it, to which it sings and lifts itself--with a strange, cold, hidden dread down in his heart. to him it is a mere vast, dizzy, dreary, troubled formlessness. its literature--its art with its infinite life in it, is a blur of vagueness. he complains because mobs of images are allowed in it. it is full of huddled associations. when carlyle appeared, the stucco-greek mind grudgingly admitted that he was 'effective.' a man who could use words as other men used things, who could put a pen down on paper in such a way as to lift men out from the boundaries of their lives and make them live in other lives and in other ages, who could lend them his own soul, had to have something said about him; something very good and so it was said, but he was not an "artist." from the same point of view and to the same people browning was a mere great man (that is: a merely infinite man). he was a man who went about living and loving things, with a few blind words opening the eyes of the blind. it had to be admitted that robert browning could make men who had never looked at their brothers' faces dwell for days in their souls, but he was not a poet. richard wagner, too, seer, lover, singer, standing in the turmoil of his violins conquering a new heaven for us, had great conceptions and was a musical genius without the slightest doubt, but he was not an "artist." he never worked his conceptions out. his scores are gorged with mere suggestiveness. they are nothing if they are not played again and again. for twenty or thirty years richard wagner was outlawed because his music was infinitely unfinished (like the music of the spheres). people seemed to want him to write cosy, homelike music. iv symbolism in modern art "_so i drop downward from the wonderment of timelessness and space, in which were blent the wind, the sunshine and the wanderings of all the planets--to the little things that are my grass and flowers, and am content._" this prejudice against the infinite, or desire to avoid as much as possible all personal contact with it, betrays itself most commonly, perhaps, in people who have what might be called the domestic feeling, who consciously or unconsciously demand the domestic touch in a landscape before they are ready to call it beautiful. the typical american woman, unless she has unusual gifts or training, if she is left entirely to herself, prefers nice cuddlesome scenery. even if her imagination has been somewhat cultivated and deepened, so that she feels that a place must be wild, or at least partly wild, in order to be beautiful, she still chooses nooks and ravines, as a rule, to be happy in--places roofed in with gentle, quiet wonder, fenced in with beauty on every side. she is not without her due respect and admiration for a mountain, but she does not want it to be too large, or too near the stars, if she has to live with it day and night; and if the truth were told--even at its best she finds a mountain distant, impersonal, uncompanionable. unless she is born in it she does not see beauty in the wide plain. there is something in her being that makes her bashful before a whole sky; she wants a sunset she can snuggle up to. it is essentially the bird's taste in scenery. "give me a nest, o lord, under the wide heaven. cover me from thy glory." a bush or a tree with two or three other bushes or trees near by, and just enough sky to go with it--is it not enough? the average man is like the average woman in this regard except that he is less so. the fact seems to be that the average human being (like the average poet), at least for everyday purposes, does not want any more of the world around him than he can use, or than he can put somewhere. if there is so much more of the world than one can use, or than anyone else can use, what is the possible object of living where one cannot help being reminded of it? the same spiritual trait, a kind of gentle persistent grudge against the infinite, shows itself in the not uncommon prejudice against pine trees. there are a great many people who have a way of saying pleasant things about pine trees and who like to drive through them or look at them in the landscape or have them on other people's hills, but they would not plant a pine tree near their houses or live with pines singing over them and watching them, every day and night, for the world. the mood of the pine is such a vast, still, hypnotic, imperious mood that there are very few persons, no matter how dull or unsusceptible they may seem to be, who are not as much affected by a single pine, standing in a yard by a doorway, as they are by a whole skyful of weather. if they are down on the infinite--they do not want a whole treeful of it around on the premises. and the pine comes as near to being infinite as anything purely vegetable, in a world like this, could expect. it is the one tree of all others that profoundly suggests, every time the light falls upon it or the wind stirs through it, the things that man cannot touch. woven out of air and sunlight and its shred of dust, it always seems to stand the monument of the woods, to the intangible, and the invisible, to the spirituality of matter. who shall find a tree that looks down upon the spirit of the pine? and who, who has ever looked upon the pines--who has seen them climbing the hills in crowds, drinking at the sun--has not felt that however we may take to them personally they are the chosen people among the trees? to pass from the voice of them to the voice of the common leaves is to pass from the temple to the street. in the rest of the forest all the leaves seem to be full of one another's din--of rattle and chatter--heedless, happy chaos, but in the pines the voice of every pine-spill is as a chord in the voice of all the rest, and the whole solemn, measured chant of it floats to us as the voice of the sky itself. it is as if all the mystical, beautiful far-things that human spirits know had come from the paths of space, and from the presence of god, to sing in the tree-trunks over our heads. now it seems to me that the supremacy of the pine in the imagination is not that it is more beautiful in itself than other trees, but that the beauty of the pine seems more symbolic than other beauty, and symbolic of more and of greater things. it is full of the sturdiness and strength of the ground, but it is of all trees the tree to see the sky with, and its voice is the voice of the horizons, the voice of the marriage of the heavens and the earth; and not only is there more of the sky in it, and more of the kingdom of the air and of the place of sleep, but there is more of the fiber and odor from the solemn heart of the earth. no other tree can be mutilated like the pine by the hand of man and still keep a certain earthy, unearthly dignity and beauty about it and about all the place where it stands. a whole row of them, with their left arms cut off for passing wires, standing severe and stately, their bare trunks against heaven, cannot help being beautiful. the beauty is symbolic and infinite. it cannot be taken away. if the entire street-side of a row of common, ordinary middle-class trees were cut away there would be nothing to do with the maimed and helpless things but to cut them down--remove their misery from all men's sight. to lop away the half of a pine is only to see how beautiful the other half is. the other half has the infinite in it. however little of a pine is left it suggests everything there is. it points to the universe and beckons to the night and the day. the infinite still speaks in it. it is the optimist, the prophet of trees. in the sad lands it but grows more luxuriantly, and it is the spirit of the tropics in the snows. it is the touch of the infinite--of everywhere--wherever its shadow falls. i have heard the sound of a hammer in the street and it was the sound of a hammer. in the pine woods it was a hundred guns. as the cloud catches the great empty spaces of night out of heaven and makes them glorious the pine gathers all sound into itself--echoes it along the infinite. the pine may be said to be the symbol of the beauty in machinery, because it is beautiful the way an electric light is beautiful, or an electric-lighted heaven. it has the two kinds of beauty that belong to life: finite beauty, in that its beauty can be seen in itself, and infinite beauty in that it makes itself the symbol, the center, of the beauty that cannot be seen, the beauty that dwells around it. what is going to be called the typical power of the colossal art, myriad-nationed, undreamed of men before, now gathering in our modern life, is its symbolic power, its power of standing for more than itself. every great invention of modern mechanical art and modern fine art has held within it an extraordinary power of playing upon associations, of playing upon the spirits and essences of things until the outer senses are all gathered up, led on, and melted, as outer senses were meant to be melted, into inner ones. what is wrought before the eyes of a man at last by a great modern picture is not the picture that fronts him on the wall, but a picture behind the picture, painted with the flame of the heart on the eternal part of him. it is the business of a great modern work of art to bring a man face to face with the greatness from which it came. millet's angelus is a portrait of the infinite,--and a man and a woman. a picture with this feeling of the infinite painted in it--behind it--which produces this feeling of the infinite in other men by playing upon the infinite in their own lives, is a typical modern masterpiece. the days when the infinite is not in our own lives we do not see it. if the infinite is in our own lives, and we do not like it there, we do not like it in a picture, or in the face of a man, or in a corliss engine--a picture of the face of all-man, mastering the earth--silent--lifted to heaven. v the machines as artists it is not necessary, in order to connect a railway train with the infinite, to see it steaming along a low sky and plunging into a huge white hill of cloud, as i did the other day. it is quite as infinite flying through granite in hoosac mountain. most people who do not think there is poetry in a railway train are not satisfied with flying through granite as a trait of the infinite in a locomotive, and yet these same people, if a locomotive could be lifted bodily to where infinity is or is supposed to be (up in the sky somewhere)--if they could watch one night after night plowing through planets--would want a poem written about it at once. a man who has a theory he does not see poetry in a locomotive, does not see it because theoretically he does not connect it with infinite things: the things that poetry is usually about. the idea that the infinite is not cooped up in heaven, that it can be geared and run on a track (and be all the more infinite for not running off the track), does not occur to him. the first thing he does when he is told to look for the infinite in the world is to stop and think a moment, where he is, and then look for it somewhere else. it would seem to be the first idea of the infinite, in being infinite, not to be anywhere else. it could not be anywhere else if it tried; and if a locomotive is a real thing, a thing wrought in and out of the fiber of the earth and of the lives of men, the infinity and poetry in it are a matter of course. i like to think that it is merely a matter of seeing a locomotive as it is, of seeing it in enough of its actual relations as it is, to feel that it is beautiful; that the beauty, the order, the energy, and the restfulness of the whole universe are pulsing there through its wheels. the times when we do not feel poetry in a locomotive are the times when we are not matter-of-fact enough. we do not see it in enough of its actual relations. being matter-of-fact enough is all that makes anything poetic. everything in the universe, seen as it is, is seen as the symbol, the infinitely connected, infinitely crowded symbol of everything else in the universe--the summing up of everything else--another whisper of god's. have i not seen the great sun itself, from out of its huge heaven, packed in a seed and blown about on a wind? i have seen the leaves of the trees drink all night from the stars, and when i have listened with my soul--thousands of years--i have heard the night and the day creeping softly through mountains. people called it geology. it seems that if a man cannot be infinite by going to the infinite, he is going to be infinite where he is. he is carving it on the hills, tunneling it through the rocks of the earth, piling it up on the crust of it, with winds and waters and flame and steel he is writing it on all things--that he is infinite, that he will be infinite. the whole planet is his signature. if what the modern man is trying to say in his modern age is his own infinity, it naturally follows that the only way a modern artist can be a great artist in a modern age is to say in that age that man is infinite, better than any one else is saying it. the best way to express this infinity of man is to seek out the things in the life of the man which are the symbols of his infinity--which suggest his infinity the most--and then play on those symbols and let those symbols play on him. in other words the poet's program is something like this. the modern age means the infinity of man. modern art means symbolism of man's infinity. the best symbol of the man's infinity the poet can find, in this world the man has made, is the machine. at least it seems so to me. i was looking out of my study window down the long track in the meadow the other morning and saw a smoke-cloud floating its train out of sight. a high wind was driving, and in long wavering folds the cloud lay down around the train. it was like a great bird, close to the snow, forty miles an hour. for a moment it almost seemed that, instead of a train making a cloud, it was a cloud propelling a train--wing of a thousand tons. i have often before seen a broken fog towing a mountain, but never have i seen before, a train of cars with its engine, pulled by the steam escaping from its whistle. of course the train out in my meadow, with its pillar of fire by night and of cloud by day hovering over it, is nothing new; neither is the tower of steam when it stands still of a winter morning building pyramids, nor the long, low cloud creeping back on the car-tops and scudding away in the light; but this mad and splendid thing of whiteness and wind, riding out there in the morning, this ghost of a train--soul or look in the eyes of it, haunting it, gathering it all up, steel and thunder, into itself, catching it away into heaven--was one of the most magical and stirring sights i have seen for a long time. it came to me like a kind of zeit-geist or passing of the spirit of the age. when i looked again it was old 992 from the roundhouse escorting number eight to springfield. vi the machines as philosophers if we could go into history as we go into a theatre, take our seats quietly, ring up the vast curtain on any generation we liked, and then could watch it--all those far off queer happy people living before our eyes, two or three hours--living with their new inventions and their last wonders all about them, they would not seem to us, probably to know why they were happy. they would merely be living along with their new things from day to day, in a kind of secret clumsy gladness. perhaps it is the same with us. the theories for poems have to be arranged after we have had them. the fundamental appeal of machinery seems to be to every man's personal everyday instinct and experience. we have, most of the time, neither words nor theories for it. i do not think that our case must stand or fall with our theory. but there is something comfortable about a theory. a theory gives one permission to let ones self go--makes it seem more respectable to enjoy things. so i suggest something--the one i have used when i felt i had to have one. i have partitioned it off by itself and it can be skipped. 1. the substance of a beautiful thing is its idea. 2. a beautiful thing is beautiful in proportion as its form reveals the nature of its substance, that is, conveys its idea. 3. machinery is beautiful by reason of immeasurable ideas consummately expressed. 4. machinery has poetry in it because the three immeasurable ideas expressed by machinery are the three immeasurable ideas of poetry and of the imagination and the soul--infinity and the two forms of infinity, the liberty and the unity of man. 5. these immeasurable ideas are consummately expressed by machinery because machinery expresses them in the only way that immeasurable ideas can ever be expressed: (1) by literally doing the immeasurable things, (2) by suggesting that it is doing them. to the man who is in the mood of looking at it with his whole being, the machine is beautiful because it is the mightiest and silentest symbol the world contains of the infinity of his own life, and of the liberty and unity of all men's lives, which slowly, out of the passion of history is now being wrought out before our eyes upon the face of the earth. 6. it is only from the point of view of a nightingale or a sonnet that the ã¦sthetic form of a machine, if it is a good machine, can be criticised as unbeautiful. the less forms dealing with immeasurable ideas are finished forms the more symbolic and speechless they are; the more they invoke the imagination and make it build out on god, and upon the future, and upon silence, the more artistic and beautiful and satisfying they are. 7. the first great artist a modern or machine age can have, will be the man who brings out for it the ideas behind its machines. these ideas--the ones the machines are daily playing over and about the lives of all of us--might be stated roughly as follows: the idea of the incarnation--the god in the body of the man. the idea of liberty--the soul's rescue from others. the idea of unity--the soul's rescue from its mere self. the idea of the spirit--the unseen and intangible. the idea of immortality. the cosmic idea of god. the practical idea of invoking great men. the religious idea of love and comradeship. and nearly every other idea that makes of itself a song or a prayer in the human spirit. part four ideas behind the machines i the idea of incarnation "_i sought myself through earth and fire and seas, and found it not--but many things beside; behemoth old, leviathans that ride. and protoplasm, and jellies of the tide. then wandering upward through the solid earth with its dim sounds, potential rage and mirth, i faced the dim forefather of my birth, and thus addressed him: 'all of you that lie safe in the dust or ride along the sky- lo, these and these and these! but where am i?_'" the grasshopper may be called the poet of the insects. he has more hop for his size than any of the others. i am very fond of watching him--especially of watching those two enormous beams of his that loom up on either side of his body. they have always seemed to me one of the great marvels of mechanics. by knowing how to use them, he jumps forty times his own length. a man who could contrive to walk as well as any ordinary grasshopper does (and without half trying) could make two hundred and fifty feet at a step. there is no denying, of course, that the man does it, after his fashion, but he has to have a trolley to do it with. the man seems to prefer, as a rule, to use things outside to get what he wants inside. he has a way of making everything outside him serve him as if he had it on his own body--uses a whole universe every day without the trouble of always having to carry it around with him. he gets his will out of the ground and even out of the air. he lays hold of the universe and makes arms and legs out of it. if he wants at any time, for any reason, more body than he was made with, he has his soul reach out over or around the planet a little farther and draw it in for him. the grasshopper, so far as i know, does not differ from the man in that he has a soul and body both, but his soul and body seem to be perfectly matched. he has his soul and body all on. it is probably the best (and the worst) that can be said of a grasshopper's soul, if he has one, that it is in his legs--that he really has his wits about him. looked at superficially, or from the point of view of the next hop, it can hardly be denied that the body the human soul has been fitted out with is a rather inferior affair. from the point of view of any respectable or ordinarily well-equipped animal the human body--the one accorded to the average human being in the great show of creation--almost looks sometimes as if god really must have made it as a kind of practical joke, in the presence of the other animals, on the rest of us. it looks as if he had suddenly decided at the very moment he was in the middle of making a body for a man, that out of all the animals man should be immortal--and had let it go at that. with the exception of the giraffe and perhaps the goose or camel and an extra fold or so in the hippopotamus, we are easily the strangest, the most unexplained-looking shape on the face of the earth. it is exceedingly unlikely that we are beautiful or impressive, at first at least, to any one but ourselves. nearly all the things we do with our hands and feet, any animal on earth could tell us, are things we do not do as well as men did once, or as well as we ought to, or as well as we did when we were born. our very babies are our superiors. the only defence we are able to make when we are arraigned before the bar of creation, seems to be, that while some of the powers we have exhibited have been very obviously lost, we have gained some very fine new invisible ones. we are not so bad, we argue, after all,--our nerves, for instance,--the mentalized condition of our organs. and then, of course, there is the superior quality of our gray matter. when we find ourselves obliged to appeal in this pathetic way from the judgment of the brutes, or of those who, like them, insist on looking at us in the mere ordinary, observing, scientific, realistic fashion, we hint at our mysteriousness--a kind of mesh of mysticism there is in us. we tell them it cannot really be seen from the outside, how well our bodies work. we do not put it in so many words, but what we mean is, that we need to be cut up to be appreciated, or seen in the large, or in our more infinite relations. our matter may not be very well arranged on us, perhaps, but we flatter ourselves that there is a superior unseen spiritual quality in it. it takes seers or surgeons to appreciate us--more of the same sort, etc. in the meantime (no man can deny the way things look) here we all are, with our queer, pale, little stretched-out legs and arms and things, floundering about on this earth, without even our clothes on, covering ourselves as best we can. and what could really be funnier than a human body living before the great sun under its frame of wood and glass, all winter and all summer ... strange and bleached-looking, like celery, grown almost always under cloth, kept in the kind of cellar of cotton or wool it likes for itself, moving about or being moved about, the way it is, in thousands of queer, dependent, helpless-looking ways? the earth, we can well believe, as we go up and down in it is full of soft laughter at us. one cannot so much as go in swimming without feeling the fishes peeking around the rocks, getting their fun out of us in some still, underworld sort of way. we cannot help--a great many of us--feeling, in a subtle way, strange and embarrassed in the woods. most of us, it is true, manage to keep up a look of being fairly at home on the planet by huddling up and living in cities. by dint of staying carefully away from the other animals, keeping pretty much by ourselves, and whistling a good deal and making a great deal of noise, called civilization, we keep each other in countenance after a fashion, but we are really the guys of the animal world, and when we stop to think of it and face the facts and see ourselves as the others see us, we cannot help acknowledging it. i, for one, rather like to, and have it done with. it is getting to be one of my regular pleasures now, as i go up and down the world,--looking upon the man's body,--the little funny one that he thinks he has, and then stretching my soul and looking upon the one that he really has. when one considers what a man actually does, where he really lives, one sees very plainly that all that he has been allowed is a mere suggestion or hint of a body, a sort of central nerve or ganglion for his real self. a seed or spore of infinity, blown down on a star--held there by the grip, apparently, of nothing--a human body is pathetic enough, looked at in itself. there is something indescribably helpless and wistful and reaching out and incomplete about it--a body made to pray with, perhaps, one might say, but not for action. all that it really comes to or is for, apparently, is a kind of light there is in it. but the sea is its footpath. the light that is in it is the same light that reaches down to the central fires of the earth. it flames upon heaven. helpless and unfinished-looking as it is, when i look upon it, i have seen the animals slinking to their holes before it, and worshipping, or following the light that is in it. the great waters and the great lights flock to it--this beckoning and a prayer for a body, which the man has. i go into the printing room of a great newspaper. in a single flash of black and white the press flings down the world for him--birth, death, disgrace, honor and war and farce and love and death, sea and hills, and the days on the other side of the world. before the dawn the papers are carried forth. they hasten on glimmering trains out through the dark. soon the newsboys shrill in the streets--china and the philippines and australia, and east and west they cry--the voices of the nations of the earth, and in my soul i worship the body of the man. have i not seen two trains full of the will of the body of the man meet at full speed in the darkness of the night? i have watched them on the trembling ground--the flash of light, the crash of power, ninety miles an hour twenty inches apart, ... thundering aisles of souls ... on into blackness, and in my soul i worship the body of the man. and when i go forth at night, feel the earth walking silently across heaven beneath my feet, i know that the heart-beat and the will of the man is in it--in all of it. with thousands of trains under it, over it, around it, he thrills it through with his will. i no longer look, since i have known this, upon the sun alone, nor upon the countenance of the hills, nor feel the earth around me growing softly or resting in the light, lifting itself to live. all that is, all that reaches out around me, is the body of the man. one must look up to stars and beyond horizons to look in his face. who is there, i have said, that shall trace upon the earth the footsteps of this body, all wireless telegraph and steel, or know the sound of its going? now, when i see it, it is a terrible body, trembling the earth. like a low thunder it reaches around the crust of it, grasping it. and now it is a gentle body (oh, signor marconi!), swift as thought up over the hill of the sea, soft and stately as the walking of the clouds in the upper air. is there any one to-day so small as to know where he is? i am always coming suddenly upon my body, crying out with joy like a child in the dark, "and i am here, too!" has the twentieth century, i have wondered, a man in it who shall feel himself? and so it has come to pass, this vision i have seen with my own eyes--man, my brother, with his mean, absurd little unfinished body, going triumphant up and down the earth making limbs of time and space. who is there who has not seen it, if only through the peephole of a dream--the whole earth lying still and strange in the hollow of his hand, the sea waiting upon him? thousands of times i have seen it, the whole earth with a look, wrapped white and still in its ball of mist, the glint of the atlantic on it, and in the blue place the vision of the ships. between the seas and skies the shuttle flies seven sunsets long, tropic-deep, thousand-sailed, half in waking, half in sleep. glistening calms and shouting gales water-gold and green, and many a heavenly-minded blue it thrusts and shudders through, past my starlight, past the glow of suns i know, weaving fates, loves and hates in the sea- the stately shuttle to and fro, mast by mast, through the farthest bounds of moons and noons. flights of days and nights flies fast. it may be true, as the poets are telling us, that this fashion the modern man has, of reaching out with steel and vapor and smoke, and holding a star silently in his hand, has no poetry in it, and that machinery is not a fit subject for poets. perhaps. i am merely judging for myself. i have seen the few poets of this modern world crowded into their corner of it (in westminster abbey), and i have seen also a great foundry chiming its epic up to the night, freeing the bodies and the souls of men around the world, beating out the floors of cities, making the limbs of the great ships silently striding the sea, and rolling out the roads of continents. if this is not poetry, it is because it is too great a vision. and yet there are times i am inclined to think when it brushes against us--against all of us. we feel something there. more than once i have almost touched the edge of it. then i have looked to see the man wondering at it. but he puts up his hands to his eyes, or he is merely hammering on something. then i wish that some one would be born for him, and write a book for him, a book that should come upon the man and fold him in like a cloud, breathe into him where his wonder is. he ought to have a book that shall be to him like a whole age--the one he lives in, coming to him and leaning over him, whispering to him, "rise, my son and live. dost thou not behold thy hands and thy feet?" the trains like spirits flock to him. there are days when i can read a time-table. when i put it back in my pocket it sings. in the time-table i carry in my pocket i unfold the earth. i have come to despise poets and dreams. truths have made dreams pale and small. what is wanted now is some man who is literal enough to tell the truth. ii the idea of size sometimes i have a haunting feeling that the other readers of mount tom (besides me) may not be so tremendously interested after all in machinery and interpretations of machinery. perhaps they are merely being polite about the subject while up here with me on the mountain, not wanting to interrupt exactly and not talking back. it is really no place for talking back, perhaps they think, on a mountain. but the trouble is, i get more interested than other people before i know it. then suddenly it occurs to me to wonder if they are listening particularly and are not looking off at the scenery and the river and the hills and the meadow while i wander on about railroad trains and symbolism and the mount tom pulp mill and socialism and electricity and schopenhauer and the other things, tracking out relations. it gets worse than other people's genealogies. but all i ask is, that when they come, as they are coming now, just over the page to some more of these machine ideas, or interpretations as one might call them, or impressions, or orgies with engines, they will not drop the matter altogether. they may not feel as i do. it would be a great disappointment to all of us, perhaps, if i could be agreed with by everybody; but boring people is a serious matter--boring them all the time, i mean. it's no more than fair, of course, that the subscribers to a magazine should run some of the risk--as well as the editor--but i do like to think that in these next few pages there are--spots, and that people will keep hopeful. * * * * * some people are very fond of looking up at the sky, taking it for a regular exercise, and thinking how small they are. it relieves them. i do not wish to deny that there is a certain luxury in it. but i must say that for all practical purposes of a mind--of having a mind--i would be willing to throw over whole hours and days of feeling very small, any time, for a single minute of feeling big. the details are more interesting. feeling small, at best, is a kind of glittering generality. i do not think i am altogether unaware how i look from a star--at least i have spent days and nights practising with a star, looking down from it on the thing i have agreed for the time being (whatever it is) to call myself, and i have discovered that the real luxury for me does not consist in feeling very small or even in feeling very large. the luxury for me is in having a regular reliable feeling, every day of my life, that i have been made on purpose--and very conveniently made, to be infinitely small or infinitely large as i like. i arrange it any time. i find myself saying one minute, "are not the whole human race my house-servants? is not london my valet--always at my door to do my bidding? clouds do my errands for me. it takes a world to make room for my body. my soul is furnished with other worlds i cannot see." the next minute i find myself saying nothing. the whole star i am on is a bit of pale yellow down floating softly through space. what i really seem to enjoy is a kind of insured feeling. whether i am small or large all space cannot help waiting upon me--now that i have taken iron and vapor and light and made hands for my hands, millions of them, and reached out with them. a little one shall become a thousand. i have abolished all size--even my own size does not exist. if all the work that is being done by the hands of my hands had literally to be done by men, there would not be standing room for them on the globe--comfortable standing room. but even though, as it happens, much of the globe is not very good to stand on, and vast tracts of it, every year, are going to waste, it matters nothing to us. every thing we touch is near or far, or large or small, as we like. as long as a young woman can sit down by a loom which is as good as six hundred more just like her, and all in a few square feet--as long as we can do up the whole of one of napoleon's armies in a ball of dynamite, or stable twelve thousand horses in the boiler of an ocean steamer, it does not make very much difference what kind of a planet we are on, or how large or small it is. if suddenly it sometimes seems as if it were all used up and things look cramped again (which they do once in so often) we have but to think of something, invent something, and let it out a little. we move over into a new world in a minute. columbus was mere bagatelle. we get continents every few days. thousands of men are thinking of them--adding them on. mere size is getting to be old-fashioned--as a way of arranging things. it has never been a very big earth--at best--the way god made it first. he made a single spider that could weave a rope out of her own body around it. it can be ticked all through, and all around, with the thoughts of a man. the universe has been put into a little telescope and the oceans into a little compass. alice in wonderland's romantic and clever way with a pill is become the barest matter of fact. looking at the world a single moment with a soul instead of a theodolite, no one who has ever been on it--before--would know it. it's as if the world were a little wizened balloon that had been given us once and had been used so for thousands of years, and we had just lately discovered how to blow it. iii the idea of liberty some one told me one morning not so very long ago that the sun was getting a mile smaller across every ten years. it gave me a shut-in and helpless feeling. i found myself several times during that day looking at it anxiously. i almost held my hands up to it to warm them. i knew in a vague fashion that it would last long enough for me. and a mile in ten years was not much. it did not take much figuring to see that i had not the slightest reason to be anxious. but my feelings were hurt. i felt as if something had hit the universe. i could not get myself--and i have not been able to get myself since--to look at it impersonally. i suppose every man lives in some theory of the universe, unconsciously, every day, as much as he lives in the sunlight. and he does not want it disturbed. i have always felt safe before. and, what was a necessary part of safety with me, i have felt that history was safe--that there was going to be enough of it. i have been in the world a good pleasant while on the whole, tried it and got used to it--used to the weather on it and used to having my friends hate me and my enemies turn on me and love me, and the other uncertainties; but all the time, when i looked up at the sun and saw it, or thought of it down under the world, i counted on it. i discovered that my soul had been using it daily as a kind of fulcrum for all things. i helped god lift with it. it was obvious that it was going to be harder for both of us--a mere matter of time. i could not get myself used to the thought. every fresh look i took at the sun peeling off mile after mile up there, as fast as i lived, flustered me--made my sky less useful to me, less convenient to rest in. i found myself trying slowly to see how this universe would look--what it would be like, if i were the last man on it. somebody would have to be. it would be necessary to justify things for him. he would probably be too tired and cold to do it. so i tried. i had a good deal the same experience with mount pelã©e last summer. i resented being cooped up helplessly, on a planet that leaked. the fact that it leaked several thousand miles away, and had made a comparatively safe hole for it, out in the middle of the sea, only afforded momentary relief. the hurt i felt was deeper than that. it could not be remedied by a mere applying long distances to it. it was underneath down in my soul. time and space could not get at it. the feeling that i had been trapped in a planet somehow, and that i could not get off possibly, the feeling that i had been deliberately taken body and soul, without my knowing it and without my ever having been asked, and set down on a cooled-off cinder to live, whether i wanted to or not--the sudden new appalling sense i had, that the ground underneath my feet was not really good and solid, that i was living every day of my life just over a roar of great fire, that i was being asked (and everybody else) to make history and build stone houses, and found institutions and things on the bare outside--the destroyed and ruined part of a ball that had been tossed out in space to burn itself up--the sense, on top of all this, that this dried crust i live on, or bit of caked ashes, was liable to break through suddenly at any time and pour down the center of the earth on one's head, did not add to the dignity, it seemed to me, or the self-respect of human life. "you might as well front the facts, my dear youth, look mount pelã©e in the face," i tried to say coldly and calmly to myself. "here you are, set down helplessly among stars, on a great round blue and green something all fire and wind inside. and it is all liable--this superficial crust or geological ice you are on--perfectly liable, at any time or any place after this, to let through suddenly and dump all the nations and all ancient and modern history, and you and your book, into this awful ceaseless abyss--of boiled mountains and stewed up continents that is seething beneath your feet." it is hard enough, it seems to me, to be an optimist on the edge of this earth as it is, to keep on believing in people and things on it, without having to believe besides that the earth is a huge round swindle just of itself, going round and round through all heaven, with all of us on it, laughing at us. i felt chilled through for a long time after mount pelã©e broke out. i went wistfully about sitting in sunny and windless places trying to get warmed all summer. and it was not all in my soul. it was not all subjective. i noticed that the thermometer was caught the same way. it was a plain case enough--it seemed to me--the heater i lived on had let through, spilled out and wasted a lot of its fire, and the ground simply could not get warmed up after it. i sat in the sun and pictured the earth freezing itself up slowly and deliberately, on the outside. i had it all arranged in my mind. the end of the world was not coming as the ancients saw it, by a kind of overflow of fire, but by the fires going out. a mile off the sun every ten years (this for the loss of outside heat) and volcanoes and things (for the inside heat), and gradually between being frozen under us, and frozen over us, both, both sides at once, the human race would face the situation. we would have to learn to live together. any one could see that. the human race was going to be one long row, sometime--great nations of us and little ones all at last huddled up along the equator to keep warm. just outside of this a little way, it would be perfectly empty star, all in a swirl of snowdrifts. i do not claim that it was very scientific to feel in this way, but i have always had, ever since i can remember, a moderate or decent human interest in the universe as a universe, and i had always felt as if the earth had made, for all practical purposes, a sort of contract with the human race, and when it acted like this--cooled itself off all of a sudden, in the middle of a hot summer, and all to show off a comparatively unknown and unimportant mountain hid on an island far out at sea--i could not conceal from myself (in my present and usual capacity as a kind of agent or sponsor for humanity) that there was something distinctly jarring about it and disrespectful. i felt as if we had been trifled with. it was not a feeling i had very long--this injured feeling toward the universe in behalf of the man in it, but i could not help it at first. there grew an anger within me and then out of the anger a great delight. it seemed to me i saw my soul standing afar off down there, on its cold and emptied-looking earth. then slowly i saw it was the same soul i had always had. i was standing as i had always stood on an earth before, be it a bare or flowering one. i saw myself standing before all that was. then i defied the heaven over my head and the ground under my feet not to keep me strong and glad before god. i saw that it mattered not to me, of an earth, how bare it was, or could be, or could be made to be; if the soul of a man could be kept burning on it, victory and gladness would be alive upon it. i fell to thinking of the man. i took an inventory down in my being of all that the man was, of the might of the spirit that was in him. would it be anything new to the man to be maltreated, a little, neglected--almost outwitted by a universe? had he not already, thousands of times in the history of this planet, flung his spirit upon the cold, and upon empty space--and made homes out of it? he had snuggled in icebergs. he had entered the place of the mighty heat and made the coolness of shadow out of it. it was nothing new. the planet had always been a little queer. it was when it commenced. the only difference would seem to be that, instead of having the earth at first the way it is going to be by and by apparently--an earth with a little rim of humanity around it, great nations toeing the equator to live--everything was turned around. all the young nations might have been seen any day crowded around the ends or tips of the earth to keep from falling into the fire that was still at work on the middle of it, finishing it off and getting it ready to have things happen on it. boys might have been seen almost any afternoon, in those early days, going out to the north pole and playing duck on the rock to keep from being too warm. it is a mere matter of opinion or of taste--the way a planet acts at any given time. now it is one way and now another, and we do as we like. i do not pretend to say in so many words if the sun grew feeble, just what the man would do, down in his snowdrifts. but i know he would make some kind of summer out of them. one cannot help feeling that if the sun went out, it would be because he wanted it to--had arranged something, if nothing but a good bit of philosophy. it is not likely that the man has defied the heavens and the earth all these centuries for nothing. the things they have done against him have been the making of him. when he found this same sun we are talking about, in the earliest days of all, was a sun that kept running away from him and left him in a great darkness half of every day he lived, he knew what to do. every time that heaven has done anything to him, he has had his answer ready. the man who finds himself on a planet that is only lighted part of the time, is merely reminded that he must think of something. he digs light out of the ground and glows up the world with her own sap. when he finds himself living on an earth that can only be said to be properly heated a small fraction of the year, he makes the earth itself to burn itself and keep him warm. things like this are small to us. we put coal through a desire and take the breath out of its dark body, and put it in pipes, and cook our food with poisons. we take water and burn it into air and we telegraph boilers, and flash mills around the earth on poles. we move vast machines with a little throb, like light. we put a street on a wire. great crowds in the great cities--whole blocks of them--are handed along day and night like dots and dashes in telegrams. a man cannot be stopped by a breath. we save a man up in his own whisper hundreds of years when he is dead. a human voice that reaches only a few yards makes thousands of miles of copper talk. then we make the thousand miles talk without the copper wire. we stand on the shore and beat the air with a thought thousands of miles away--make it whisper for us to ships. one need not fear for a man like this--a man who has made all the earth a deed, an action of his own soul, who has thrown his soul at last upon the waste of heaven and made words out of it. one cannot but believe that a man like this is a free man. let what will happen to the sun that warms him or the star that seems just now his foothold in space. all shall be as his soul says when his soul determines what it shall say. fire and wind and cold--when his soul speaks--and invisibility itself and nothing are his servants. the vision of a little helpless human race huddled in the tropics saying its last prayers, holding up its face to a far-off neglected-looking universe, warming its hands at the stars--the vision of all the great peoples of the earth squeezed up into esquimaux, in furs up to their eyes, stamping their feet on the equator to keep warm, is merely the sort of vision that one set of scientists gloats on giving us. one needs but to look for what the other set is saying. it has not time to be saying much, but what it practically says is: "let the sun wizen up if it wants to. there will be something. somebody will think of something. possibly we are outgrowing suns. at all events to a real man any little accident or bruise to the planet he's on is a mere suggestion of how strong he is. some new beautiful impossibility--if the truth were known--is just what we are looking for." a human race which makes its car wheels and napkins out of paper, its street pavements out of glass, its railway ties out of old shoes, which draws food out of air, which winds up operas on spools, which has its way with oceans, and plays chess with the empty ether that is over the sea--which makes clouds speak with tongues, which lights railway trains with pin-wheels and which makes its cars go by stopping them, and heats its furnaces with smoke--it would be very strange if a race like this could not find some way at least of managing its own planet, and (heaped with snowdrifts though it be) some way of warming it, or of melting off a place to live on. a corporation was formed down in new jersey the other day to light a city by the tossing of the waves. we are always getting some new grasp--giving some new sudden almost humorous stretch to matter. we keep nature fairly smiling at herself. one can hardly tell, when one hears of half the new things nowadays--actual facts--whether to laugh or cry, or form a stock company or break out into singing. no one would dare to say that a thousand years from now we will not have found some other use for moonlight than for love affairs and to haul tides with. we will be manufacturing noon yet, out of compressed starlight, and heating houses with it. it will be peddled about the streets like milk, from door to door in cases and bottles. first and last, whatever else may be said of us, we do as we like with a planet. nothing it can do to us, nothing that can happen to it, outwits us--at least more than a few hundred years at a time. the idea that we cannot even keep warm on it is preposterous. nothing would be more likely--almost any time now--than for some one to decide that we ought to have our continents warmed more, winters. it would not be much, as things are going, to remodel the floors of a few of our continents--put in registers and things, have the heat piped up from the center of the earth. the best way to get a faint idea of what science is going to be like the next few thousand years, is to pick out something that could not possibly be so and believe it. we manufacture ice in july by boiling it, and if we cannot warm a planet as we want to--at least a few furnished continents--with hot things, we will do it with cold ones, or by rubbing icebergs together. if one wants a good simple working outfit for a prophet in science and mechanics, all one has to do is to think of things that are unexpected enough, and they will come to pass. a scientist out in the northwest has just finished his plans for getting hold of the other end of the force of gravity. the general idea is to build a sort of tower or flag-pole on the planet--something that reaches far enough out over the edge to get an underhold as it were--grip hold of the force of gravity where it works backwards. of course, as anyone can see at a glance, when it is once built out with steel, the first forty miles or so (workmen using compressed air and tubular trolleys, etc.), everything on the tower would pull the other way and the pressure would gradually be relieved until the thing balanced itself. when completed it could be used to draw down electricity from waste space (which has as much as everybody on this planet could ever want, and more). what a little earth like ours would develop into, with a connection like this--a sort of umbilical cord to the infinite--no one would care to try to say. it would at least be a kind of planet that would always be sure of anything it wanted. when we had used up all the raw material or live force in our own world we could draw on the others. at the very least we would have a sort of signal station to the planets in general that would be useful. they would know what we want, and if we could not get it from them they would tell us where we could. all this may be a little mixing perhaps. it is always difficult to tell the difference between the sublime and the ridiculous in talking of a being like man. it is what makes him sublime--that there is no telling about him--that he is a great, lusty, rollicking, easy-going son of god and throws off a world every now and then, or puts one on, with quips and jests. when the laugh dies away his jokes are prophecies. it behooves us therefore to walk softly, you and i, gentle reader, while we are here with him--while this dear gentle ground is still beneath our feet. there is no telling his reach. let us notice stars more. in the meantime it does seem to me that a comparatively simple affair like this one single planet, need not worry us much. i still keep seeing it--i cannot help it--i always keep seeing it--eternities at a time, warm, convenient, and comfortable, the same old green and white, with all its improvements on it, whatever the sun does. and above all i keep seeing the man on it, full of defiance and of love and worship, being born and buried--the little-great man, running about and strutting, flying through space on it, all his interests and his loves wound about it like clouds, but beckoning to worlds as he flies. and whatever the man does with the other worlds or with this one, i always keep seeing this one, the same old stand or deck in eternity, for praying and singing and living, it always was. long after i am dead, oh, dear little planet, least and furthest breath that is blown on thy face, my soul flocks to you, rises around you, and looks back upon you and watches you down there in your round white cloud, rowing faithfully through space! iv the idea of immortality if i had never thought of it before, and some one were to come around to my study tomorrow morning and tell me that i was immortal, i am not at all sure that i would be attracted by it. the first thing that i should do, probably, would be to argue a little--ask him what it was for. i might take some pains not to commit myself (one does not want to settle a million years in a few minutes), but i cannot help being conscious, on the inside of my own mind, at least, that the first thought on immortality that would come to me, would be that perhaps it might be overdoing things a little. i can speak only for myself. i am not unaware that a great many men and women are talking to-day about immortality and writing about it. i know many people too, who, in a faithful, worried way seem to be lugging about with them, while they live, what they call a faith in immortality. i would not mean to say a word against immortality, if i were asked suddenly and had never thought of it before. if by putting out my hand i could get some of it, for other people,--people that wanted it or thought they did--i would probably. they would be happier and easier to live with. i could watch them enjoying the idea of how long they were going to last. there would be a certain social pleasure in it. but, speaking strictly for myself, if i were asked suddenly and had never heard of it before, i would not have the slightest preference on the subject. it may be true, as some say, that a man is only half alive if he does not long to live forever, but while i have the best wishes and intentions with regard to my hope for immortality i cannot get interested. i feel as if i were living forever now, this very moment, right here on the premises--universe, earth, united states of america, hampshire county, northampton, massachusetts. i feel infinitely related every day and hour and minute of my life, to an infinite number of things. as for joggling god's elbow or praying to him or any such thing as that, under the circumstances, and begging him to let me live forever, it always seems to me (i have done it sometimes when i was very tired) as if it were a way of denying him to his face. how a man who is literally standing up to his soul's eyes, and to the tops of the stars in the infinite, who can feel the eternal throbbing through the very pores of his body, can so far lose his sense of humor in a prayer, or his reverence in it, as to put up a petition to god to live forever, i entirely fail to see. i always feel as if i had stopped living forever--to ask him. i have traveled in the blaze of a trolley car when all the world was asleep, and have been shot through still country fields in the great blackness. all things that were--it seemed to my soul, were snuffed out. it was as if all the earth had become a whir and a bit of light--had dwindled away to a long plunge, or roll and roar through nothing. slowly as i came to myself i said, "now i will try to realize motion. i will see if i can know. i spread my soul about me...." ties flying under my feet, black poles picked out with lights, flapping ghostlike past the windows.... voices of wheels over and under.... the long, dreary waver of the something that sounds when the car stops (and which feels like taking gas) ... the semi-confidential, semi-public talk of the passengers, the sudden collision with silence, they come to, when the car halts--all these. finally when i look up every one has slipped away. then i find my soul spreading further and further. the great night, silent and splendid, builds itself over me. the night is the crowded time to travel--car almost to one's self, nothing but a few whirls of light and a conductor for company--the long monotone of miles--miles--flying beside me and above and around and beneath--all this shadowed world to belong to, to dwell in, to pick out with one's soul from darkness. "here am i," i said as the roar tightened once more, and gripped on its awful wire and glowed through the blackness. "here i am in infinite space, i and my bit of glimmer.... worlds fall about me. the very one i am on, and stamp my feet on to know it is there, falls and plunges with me out through deserts of space, and stars i cannot see have their hand upon me and hold me." no one would deny that the idea of immortality is a well-meaning idea and pleasantly inclined and intended to be appreciative of a god, but it does seem to me that it is one of the most absent-minded ways of appreciating him that could be conceived. i am infinite at 88 high street. i have all the immortality i can use, without going through my own front gate. i have but to look out of a window. there is no denying that mount tom is convenient, and as a kind of soul-stepping-stone, or horse-block to the infinite, the immeasurable and immortal, a mountain may be an advantage, perhaps, and make some difference; but i must confess that it seems to me that in all times and in all places a man's immortality is absolutely in his own hands. his immortality consists in his being in an immortally related state of mind. his immortality is his sense of having infinite relations with all the time there is, and his infinity consists in his having infinite relations with all the space there is. wherever, as a matter of form, a man may say he is living or staying, the universe is his real address. i have been at sea--lain with a board over me out in the wide night and looked at the infinite through a port-hole. over the edge of the swash of a wave i have gathered in oceans and possessed them. under my board in the night i have lain still with the whole earth and mastered it in my heart, shared it until i could not sleep with the joy of it--the great ship with all its souls throbbing a planet through me and chanting it to me. i thought to my soul, "where art thou?" i looked down upon myself as if i were a god looking down on myself and upon the others, and upon the ship and upon the waters. a thousand breaths we lie shrouded limbs and faces horizontal packed in cases in our named and numbered places, catalogued for sleep, trembling through the godlight below, above, deep to deep. how a church-going man in a world like this can possibly contrive to have time to cry out or worry on it, or to be troubled about another--how he can demand another, the way he does sometimes, as if it were the only thing left a god could do to straighten matters out for having put him on this one, and how he can call this religion--is a problem that leaves my mind like an exhausted receiver. it is a grave question whether any immortality they are likely to get in another world would ever really pay some people for the time they have wasted in this one, worrying about it. does any science in the world suppose or dare to suppose that i am as unimportant in it as i look--or that i could be if i tried? that i am a parasite rolled up in a drop of dew, down under a shimmering mist of worlds that do not serve me nor care for me? i swear daily that i am not living and that i will not and cannot live underneath a universe ... with a little horizon or teacup of space set down over me. the whole sky is the tool of my daily life. it belongs to me and i to it. i have said to the heavens that they shall hourly minister to me--to the uses of my spirit and the needs of my body. when i, or my spirit, would move a little i swing out on stars. in the watches of the night they reach under my eyelids and serve my sleep and wait on me with dreams, i know i am immortal because i know i am infinite. a man is at least as long as he is wide. there is no need to quibble with words. i care little enough whether i am supposed to say it is forever across my soul or everywhere across it. whichever it is, i make it the other when i am ready. if a man is infinite and lives an infinitely related life, why should it matter whether he is eternal as he calls it or not,--takes his immortality sideways here, now, and in the terms of space or later with some kind of time-arrangement stretched out and petering along over a long, narrow row of years? thousands of things are happening that are mine--out, around, and through the great darkness--being born and killed and ticked and printed while i sleep. when i have stilled myself with sleep, do i not know that the lightning is waiting on me? when i see a cloud of steam i say, "there is my omnipresence." my being is busy out in the universe having its way somewhere. the days on the other side of the world are my days. i get what i want out of them without having to keep awake for them. in the middle of the night and without trying i lay my hand on the moon. it is my moon, wherever it may be, or whether i so much as look upon it, and when i do look upon it it is no roof for me, and the stars behind it flow in my veins. ii i have been reading lately a book on immortality, the leading idea of which seems to be a sort of astral body for people--people who are worthy of it. the author does not believe after the old-fashioned method that we are going to the stars. he intimates (for all practical purposes) that we do not need to. the stars are coming to us,--are already being woven in us. the author does not say it in so many words, but the general idea seems to be that the more spiritual or subtle body we are going to have, is already started in us--if we live as we should--growing like a kind of lining for this one. i can only speak for one, but i find that when i am willing to take the time from reading books on immortality to enjoy a few infinite experiences, i am not apt to be troubled very much about another world. it is daily obvious to me that i belong and that i am living in an infinite and eternal world, inconceivably better planned and managed than one of mine would be, and the only logical thing that i can do, is to take it for granted that the next one is even better than this. if the main feature of the next world consists in there not being one, then so much the better. i would not have thought so. it seems a little abrupt at this moment, perhaps, but it is a mere detail and why not leave it to god to work it out? he doesn't have to neglect anything to do it--which is what we do--and he is going to do it anyway. i have refused to take time from my infinity now for a theory of a theory about some new kind by and by. i have but to stand perfectly still. there is an infinite opening and shutting of doors for me, through all the heavens and the earth. i lie with my head in the deep grass. a square yard is forever across. i listen to a great city in the grass--millions of insects. microscopes have threaded it for me. i know their city--all its mighty little highways. i possess it. and when i walk away i rebuild their city softly in my heart. winds, tides, and vapors are for me everywhere, that my soul may possess them. i reach down to the silent metals under my feet that millions of ages have worked on, and fire and wonder and darkness. i feel the sun and the lives of nations flowing around to me, from under the sea. who can shut me out from anybody's sunrise? "oh, tenderly the haughty day fills his blue urn with fire; one morn is in the mighty heaven and one in my desire." i play with the seasons, with all the weathers on earth. i can telegraph for them. i go to the weather i want. the sky--to me--is no longer a great, serious, foreign-looking shore, conducting a big foolish cloud-business, sending down decrees of weather on helpless cities. with a whistle and a roar i defy it--move any strip of it out from over me--for any other strip. i order the time of year. it is my sky. i bend it a little--just a little. the sky no longer has a monopoly of wonder. with the hands of my hands, my brother and i have made an earth that can answer a sky back, that can commune with a sky. the soul at last guesses at its real self. it reaches out and dares. men go about singing with telescopes. i do not always need to lift my hands to a sky and pray to it now. i am related to it. with the hands of my hands i work with it. i say "i and the sky." i say "i and the earth." we are immortal because we are infinite. we have reached over with the hands of our hands. they are praying a stupendous prayer--a kind of god's prayer. god's hand has been grasped--vaguely--wonderfully out in the dark. no longer is the joy of the universe to a man, one of his great, solemn, solitary joys. the sublime itself is a neighborly thought. god's machine--up--there--and the machines of the man have signaled each other. v the idea of god my study (not the place where i get my knowledge but the place where i put it together) is a great meadow--ten square splendid level miles of it--as fenceless and as open as a sky--merely two mountains to stand guard. if h---the scientist who lives nearest to me (that is; nearest to my mind,) were to come down to me to-morrow morning, down in my meadow, with its huge triangle of trolleys and railways humming gently around the edges and tell me that he had found a god, i would not believe it. "where?" i would say, "in which bottle?" i have groped for one all these years. ever since i was a child i have been groping for a god. i thought one had to. i have turned over the pages of ancient books and hunted in morning papers and rummaged in the events of the great world and looked on the under sides of leaves and guessed on the other sides of the stars and all in vain. i never could make out to find a god in that way. i wonder if anyone can. i know it is not the right spirit to have, but i must confess that when the scientist (the smaller sort of scientist around the corner in my mind and everybody's mind) with all his retorts and things, pottering with his argument of design, comes down to me in my meadow and reminds me that he has been looking for a god and tells me cautiously and with all his kind, conscientious hems and haws that he has found him, i wonder if he has. the very necessity a man is under of seeking a god at all, in a world alive all over like this, of feeling obliged to go on a long journey to search one out makes one doubt if the kind of god he would find would be worth while. i have never caught a man yet who has found his god in this way, enjoying him or getting anyone else to. it does seem to me that the idea of a god is an absolutely plain, rudimentary, fundamental, universal human instinct, that the very essence of finding a god consists in his not having to be looked for, in giving one's self up to one's plain every-day infinite experiences. i suppose if it could be analyzed, the poet's real quarrel with the scientist is not that he is material, but that he is not material enough,--he does not conceive matter enough to find a god. i cannot believe for instance that any man on earth to whom the great spectacle of matter going on every day before his eyes is a scarcely noticed thing--any man who is willing to turn aside from this spectacle--this spectacle as a whole--and who looks for a god like a chemist in a bottle for instance--a bottle which he places absolutely by itself, would be able to find one if he tried. it seems to me that it is by letting one's self have one's infinite--one's infinitely related experiences, and not by cutting them off that one comes to know a god. to find a god who is everywhere one must at least spend a part of one's time in being everywhere one's self--in relating one's knowledge to all knowledge. there are various undergirding arguments and reasons, but the only way that i really know there is an infinite god is because i am infinite--in a small way--myself. even the matter that has come into the world connected with me, and that belongs to me, is infinite. if my soul, like some dim pale light left burning within me, were merely to creep to the boundaries of its own body, it would know there was a god. the very flesh i live with every day is infinite flesh. from the furthest rumors of men and women, the furthest edge of time and space my soul has gathered dust to itself. i carry a temple about with me. if i could do no better, and if there were need, i am my own cathedral. i worship when i breathe. i bow down before the tick of my pulse. i chant to the palm of my hand. the lines in the tips of my fingers could not be duplicated in a million years. shall any man ask me to prove there are miracles or to put my finger on god? or to go out into some great breath of emptiness or argument to be sure there is a god? i am infinite. therefore there is a god. i feel daily the god within me. has he not kindled the fire in my bones and out of the burning dust warmed me before the stars--made a hearth for my soul before them? i am at home with them. i sit daily before worlds as at my own fireside. i suppose there is something intolerant and impatient and a little heartless about an optimist--especially the kind of optimism that is based upon a simple everyday rudimentary joy in the structure of the world. there is such a thing, i suppose, with some of us, as having a kind of devilish pride in faith, as one would say to ordinary mortals and creepers and considerers and arguers "oh now just see me believe!" we are like boys taking turns jumping in the great vacant lot, seeing which can believe the furthest. we need to be reminded that a man cannot simply bring a little brag to god, about his world, and make a religion out of it. i do not doubt in the least, as a matter of theory, that i have the wrong spirit--sometimes--toward the scientific man who lives around the corner of my mind. it seems to me he is always suggesting important-looking unimportant things. i have days of sympathizing with him, of rolling his great useless heavy-empty pack up upon my shoulders and strapping it there. but before i know it i'm off. i throw it away or melt it down into a tablet or something--put it in my pocket. i walk jauntily before god. and the worst of it is, i think he intended me to. i think he intended me to know and to keep knowing daily what he has done for me and is doing now, out in the universe, and what he has made me to do. i also am a god. from the first time i saw the sun i have been one daily. i have performed daily all the homelier miracles and all the common functions of a god. i have breathed the invisible into my being. out of the air of heaven i have made flesh. i have taken earth from the earth and burned it within me and made it into prayers and into songs. i have said to my soul "to eat is to sing." i worship all over. i am my own sacrament. i lay before god nights of sleep, and the delight and wonder of the flesh i render back to him again, daily, as an offering in his sight. and what is true of my literal body--of the joy of my hands and my feet, is still more true of the hands of my hands. when i wake in the night and send forth my thought upon the darkness, track out my own infinity in it, feel my vast body of earth and sky reaching around me, all telegraphed through with thought, and floored with steel, i may have to grope for a god a little (i do sometimes), but i do it with loud cheers. i sing before the door of heaven if there is a heaven or needs to be a heaven. when i look upon the glory of the other worlds, has not science itself told me that they are a part of me and i a part of them? nothing is that would not be different without something else. my thoughts are ticking through the clouds, and the great sun itself is creeping through me daily down in my bones. the steam cloud hurries for me on a hundred seas. i turn over in my sleep at midnight and lay my hand on the noon. and when i have slept and walk forth in the morning, the stars flow in my veins. why should a man dare to whine? "whine not at me!" i have said to man my brother. if you cannot sing to me do not interrupt me. let him sing to me who sees the watching of the stars above the day, who hears the singing of the sunrise on its way through all the night. who outfaces skies, outsings the storms, whose soul has roamed infinite-homed through tents of space, his hand in the dim great hand that forms all wonder. let him sing to me who is the sky voice, the thunder lover who hears above the wind's fast-flying shrouds the drifted darkness, the heavenly strife, the singing on the sunny sides of all the clouds, of his own life. vi the idea of the unseen and intangible _an ode to the unseen_ poets of flowers, singers of nooks in space, petal-mongers, embroiderers of words in the music-haunted houses of the birds, singers with the thrushes and pewees in the glimmer-lighted roofs of the trees- unhand my soul! buds with singing in their hearts, birds with blooms upon their wings, all the wandering whispers of delight, the near familiar things; voice of pine trees, winds of daisies, sounds of going in the grain shall not bind me to thy singing when the sky with god is ringing for the joy of the rain. sea and star and hill and thunder, dawn and sunset, noon and night, all the vast processional of the wonder where the worlds are, where my soul is, where the shining tracks are for the spirit's flight- lift thine eyes to these from the haunts of dewdrops, hollows of the flowers, caves of bees that sing like thee, only in their bowers; from the stately growing cities of the little blowing leaves, to the infinite windless eaves of the stars; from the dainty music of the ground, the dim innumerable sound of the mighty sun creeping in the grass, softest stir of his feet (where they go far and slow on their immemorial beat of buds and seeds and all the gentle and holy needs of flowers), to the old eternal round of the going of his might, above the confines of the dark, odors and winds and showers, day and night, above the dream of death and birth flickering east and west, boundaries of a shadow of an earth- where he wheels and soars and plays in illimitable light, sends the singing stars upon their ways and on each and every world when the little shadow for its little sleep is furled- pours the days. * * * * * the first time i gazed in the great town upon a solid mile of electric cars--threaded with nothing--mesmerism hauling a whole city home to supper, it seemed to me as if the central power of all things, the thing that floats and breathes through the universe, must have been found by someone--gathered up from between stars, and turned on--poured down gently on the planet--falling on a thousand wheels, and run on the tops of cars--the secret thrill that softly and out in the darkness and through all ages had done all things. i felt as if i had seen the infinite in some near familiar, humdrum place. i walked on in a dazed fashion. i do not suppose i could really have been more surprised if i had met a star walking in the street. in my deepest dream i heard the song running in my sleep through the lowest caves of being down below where no sound is, sun is, hearing, seeing that men know. there was something about it, about that sense of the mile of cars moving, that made it all seem very old. _an ode to the lightning._ before the first new dust of dream god took for making man and hope and love and graves had kindled to its fate. before the floods had folded round the hills. before the rainbow born of cloud had taught the sky its tints, the lightning minstrel was. the cry of vague to vague. the chaos-voice that rolled and crept from out the pale bewildered wonder-stuff that wove the worlds, before the hand had stirred that touched them, while still, hinged on nothing, dim and shapeless things and clouds with groping sleep upon their wings floated and waited. before the winds had breathed the breath of life or blown from wastes of space to earth's creating place, the souls of seeds and ghosts of old dead stars, the lightning spirit willed their feet with wonder should be thrilled. --primal fire of all desire that leaps from men to men, brother of suns and all the glorious ones that circle skies, he flashed to these the night that brought the birth, the vision of the place and raised his awful face to all their glittering crowds, and cried from where it lay --a tiny ball of fire and clay in swaddling clothes of clouds, "behold the earth!" * * * * * * * * * * oh heavenly feet of the hot cloud! bringer of the garnered airs. herald of the shining rains! looser of the locked and lusty winds from their misty caves. opener of the thousand thousand-gloried doors twixt heaven and heaven and heaven's heaven. oh thou whose play men make to do their work (_why do their work?_) --and call from holidays of space, sojourns of suns and moons, and lock to earth (_why lock to earth?_) * * * * * that the dead face may flash across the seas the cry of the new-born babe be heard around a world. ah me! and the click of lust and the madness and the gladness and the ache of dust, dust! an ode to the telegraph wires. the song the world sang laying the atlantic cable the mortal wires of the heart of the earth i sing, melted and fused by men, that the immortal fires of their souls should fling to eaves of heaven and caves of sea, and god himself, and farthest hills and dimmest bounds of sense the flame of the creature's ken, the flame of the glow of the face of god upon the face of men. wind-singing wires along their thousand airy aisles, feet of birds and songs of leaves, glimmer of stars and dewy eves. sea-singing wires along their thousand slimy miles, shadowy deeps, unsunned steeps, beating in their awful caves to mouthing fish and bones and weeds unfurled deserts of waves the heart-beat of this upper world. infinite blue, infinite green, infinite glory of the ear ticking its passions through infinite fear, ooze of storm, sodden and slanting wrecks the forever untrodden decks of death, ever the seething wires on the floors of the world, below the last locked fast water-darkened doors of the sun, lighting the awful signal fires of our speechless vast desires on the mountains and the hills of the sea till the sandy-buried heights and the sullen sunken vales and fire-defying barrens of the deep the hearth of souls shall be beacons of thought, and from the lurk of the shark to the sunrise-lighted eerie of the lark and where the farthest cloud-sail fills shall be felt the throbbing and the sobbing and the hoping the might and mad delight, the hell-and-heaven groping of our little human wills. an ode to the wireless the prayer of man through all the years in which the sky-telegraph would not work roofed in with fears, beneath its little strip of sky that is blown about in and out across my wavering strip of years- who am i whose singing scarce doth reach the cloud-climbed hills, to take upon my lips the speech of those whose voices heaven fills with splendor? and yet- i cannot quite forget that in the underdawn of dreams i have felt the faint surmise shining through the starry deep of my sleep that i with god went singing once up and down with suns and storms through the phantom-pillared forms and stately-silent naves and thunder-dreaming caves of heaven. great spirit--thou who in my being's burning mesh hath wrought the shining of the mist through and through the flesh, who, through the double-wondered glory of the dust hast thrust habits of skies upon me, souls of days and nights, where are the deeds that needs must be, the dreams, the high delights, that i once more may hear my voice from cloudy door to door rejoice- may stretch the boundaries of love beyond the mumbling, mock horizons of my fears to the faint-remembered glory of those years- may lift my soul and reach this heaven of thine with mine? where are the gleams? thou shalt tell me, shalt compel me. the sometime glory shall return i know. the day shall be when by wondering i shall learn with vapor-fingers to discern the music-hidden keys of skies- shall touch like thee until they answer me the chords of the silent air and strike the wild and slumber-music out dreaming there. above the hills of singing that i know on the trackless, soundless path that wonder hath i shall go, beyond the street-cry of the poet, the hurdy-gurdy singing of the throngs, to the throne of silence, where the doors that guard the farthest faintest shores of day swing their bars, and shut the songs of heaven in from all our dreaming-doing din, behind the stars. there, at last, the climbing and the singing passed, and the cry, my hushed and listening soul shall lie at the feet of the place where the singer sings who hides his face. vii the idea of great men "_i had a vision under a green hedge a hedge of hips and haws--men yet shall hear archangels rolling over the high mountains old satan's empty skull._" as it looks from mount tom, casting a general glance around, the earth has about been put into shape, now, to do things. the earth has never been seen before looking so trim and convenient--so ready for action--as it is now. steamships and looms and printing presses and railways have been supplied, wireless telegraph furnishings have lately been arranged throughout, and we have put in speaking tubes on nearly all the continents, and it looks--as seen from mount tom, at least, as if the planet were just being finished up, now, for a great author. it is true that art and literature do not have, at first glance, a prosperous look in a machine age, but probably the real trouble the modern world is having with its authors is not because it is a world full of materialism and machinery, but because its authors are the wrong size. the modern world as it booms along recognizes this, in its practical way, and instead of stopping to speak to its little authors, to its poets crying beside it, and stooping to them and encouraging them, it is quietly and sensibly (as it seems to some of us) going on with its machines and things making preparations for bigger ones. i have thought the great authors in every age were made by the greatness of the listening to them. the greatest of all, i notice, have felt listened to by god. even the lesser ones (who have sometimes been called greatest) have felt listened to, most of them, one finds, by nothing less than nations. the man jesus gathers kingdoms about him in his talk, like an infant class. it was the way he felt. almost any one who could have felt himself listened to in this daring way that jesus did would have managed to say something. he could hardly have missed, one would think, letting fall one or two great ideas at least--ideas that nations would be born for. it ought not to be altogether without meaning to a modern man that the great prophets and interpreters have talked as a rule to whole nations and that they have talked to them generally, too, for the glory of the whole earth. they could not get their souls geared smaller than a whole earth. shakspeare feels the generations stretching away like galleries around him listening--when he makes love. it was no particular heroism or patience in the man columbus that made him sail across an ocean and discover a continent. he had the girth of an earth in him and had to do something with it. he could not have helped it. he discovered america because he felt crowded. one would think from the way some people have of talking or writing of immortality that it must be a kind of knack. as a matter of historic fact it has almost always been some mere great man's helplessness. when people have to be created and born on purpose, generation after generation of them, to listen to a man, two or three thousand years of them sometimes, on this planet, it is because the man himself when he spoke felt the need of them--and mentioned it. it is the man who is in the habit of addressing his remarks to a few continents and to several centuries who gets them. i would not dare to say just how or when our next great author on this earth is going to happen to us, but i shall begin to listen hard and look expectant the first time i hear of a man who gets up on his feet somewhere in it and who speaks as if the whole earth were listening to him. if ever there was an earth that is getting ready to listen, and to listen all over, it is this one. and the first great man who speaks in it is going to speak as if he knew it. it is a world which has been allowed about a million years now, to get to the point where it could be said to begin to be conscious of being a world at all. and i cannot believe that a world which for the first time in its history has at last the conveniences for listening all over, if it wants to, is not going to produce at the same time a man who shall have something to say to it--a man that shall be worthy of the first single full audience, sunset to sunset, that has ever been thought of. it would seem as if, to say the least, such an audience as this, gathering half in light and half in darkness around a star, would celebrate by having a man to match. it would not be necessary for him to fall back, either, one would think, upon anything that has ever been said or thought of before. already even in the sight and sounds of this present world has the verse of scripture about the next come true--"eye hath not seen nor ear heard." it is not conceivable that there shall not be something said unspeakably and incredibly great to the first full house the planet has afforded. i have gone to the place of books. i have seen before this all the peoples flocking past me under the earth with their little corner-saviors--each with his own little disc of worship all to himself on the planet--partitioned away from the rest for thousands of years. but now the whole face of the earth is changed. no longer can great men and great events be aimed at it and glanced off on it--into single nations. great men, when they come now, can generally have a world at their feet. it is not possible that we shall not have them. the whole earth is the wager that we are going to have them. the bids are out--great statesmen, great actors, great financiers, great authors--even millionaires will gradually grow great. it cannot be helped. and it will be strange if someone cannot think of something to say, with the first full house this planet has afforded. even as it is now, let any man with a great girth of love in him but speak once--but speak one single round-the-world delight and nations sit at his feet. when rudyard kipling is dying with pneumonia seven seas listen to his breathing. the nations are in galleries on the stage of the earth now, one listening above the other to the same play following around the sunrise. every one is affected by it--a kind of soul-suction--a great pulling from the world. people who do not want to write at all feel it--a kind of huge, soft, capillary attraction apparently--to a pen. the whole planet kindles every man's solitude. continents are bellows for the glow in him if there is any. the wireless telegraph beckons ideas around the world. "how does a planet applaud?" dreams the young author. "with a faint flush of light?" one would like to be liked by it--speak one's little piece to it. when one was through, one could hear the soft hurrah through space. i wonder sometimes that in this presence i ever could have thought or had times of thinking it was a little or a lonely world to write in--to flicker out thoughts in. when i think of what a world it was that came to men once and of the world that waits around me--around all of us now--i do like to mention it. when many years ago, as a small boy, i was allowed for the first time to open the little inside door in the paddle-box of a great side-wheel steamer and watched its splendid thrust on the sea, i did not know why it was that i could not be called away from it, or why i stood and watched hour after hour unconscious before it--the thunder and the foam piling up upon my being. i have guessed now. i watch the drive-wheel of an engine now as if i were tracking out at last the last secret of loneliness. i face time and space with it. i know i have but to do a true deed and i am crowded round--to help me do it. i know i have but to think a true thought, but to be true and deep enough with a book--feel a worldful for it, put a worldful in it--and the whole planet will look over my shoulder while i write. thousands of printing presses under a thousand skies i hear truth working softly, saying over and over, and around and around the earth, the word that was given to me to say. can any one believe that this strange new, deep, beautiful, clairvoyant feeling a man has nowadays every day, every hour, for the other side of a star, is not going to make arts and men and words and actions great in the world? silently, you and i, gentle reader, are watching the first great gathering-in of a world to listen and to live. the continents are unanimous. there has never been a quorum before. they are getting together at last for the first world-sized man, for the first world-sized word. they are listening him into life. it is really getting to be a planet now, a whole completed articulated, furnished, lived-through, loved-through star, from sun's end to sun's end. one sees the sign on it to let to any man who really wants it. viii the idea of love and comradeship "_ever there comes an onward phrase to me of some transcendent music i have heard; no piteous thing by soft hands dulcimered, no trumpet crash of blood-sick victory. but a glad strain of some still symphony that no proud mortal touch has ever stirred._" have you ever walked out over the hill in your city at night, gentle reader--your own city--felt the soul of it lying about you--lying there in its gentleness and splendor and lust? have you never felt as you stood there that you had some right to it, some right way down in your being--that all this haze of light and darkness, all the people in it, somehow really belonged to you? we do not exactly let our souls say it--at least out loud--but there are times when i have been out in the street with the others, when i have heard them--heard our souls, that is--all softly trooping through us, saying it to ourselves. "o to know--to be utterly known one moment; to have, if only for one second, twenty thousand souls for a home; to be gathered around by a city, to be sought out and haunted by some one great all-love, once, streets and silent houses of it!" i go up and down the pavements reaching out into the days and nights of the men and the women. perhaps you have seen me, gentle reader, in the great street, in the long, slow shuffle with the others? and i have said to you though i did not know it: "did you not call to me? did you hear anything? i think it was i calling to you." i have sat at the feet of cities. i have swept the land with my soul. i have gone about and looked upon the face of the earth. i have demanded of smoking villages sweeping past and of the mountains and of the plains and of the middle of the sea: "where are those that belong to me? will i ever travel near enough, far enough?" i have gone up and down the world--seen the countless men and women in it, standing on either side of their abyss of circumstance, beckoning and reaching out. i have seen men and women sleepless, or worn, or old, casting their bread upon the waters, grasping at sunsets or afterglows, putting their souls like letters in bottles. some of them seem to be flickering their lives out like marconi messages into a sort of infinite, swallowing human space. always this same wild aimless sea of living. there does not seem to be a geography for love. my soul answered me: "did you expect a world to be indexed? life is steered by a wind. blossoms and cyclones and sunshine and you and i--all blundering along together." "let every seed swell for itself," the universe has said, in its first fine careless rapture. god is merely having a good time. why should i go up and down a universe crying through it, "where are those that belong to me?" i have looked at the stars swung out at me and they have not answered, and now when i look at the men, i have seemed to see them, every man in a kind of dull might, rushing, his hands before him, hinged on emptiness. "you are alone," the heart hath said. "get up and be your own brother. the world is a great who cares?" but when, in the middle of deep, helpless sleep, tossed on the wide waters, i wake in a ship, feel it trembling all through out there with my brother's care for me, i know that this is not true. "around sunsets, out through the great dark," i find myself saying, "he has reached over and held me. out here on this high hill of water, under this low, touching sky, i sleep." sometimes i do not sleep. i lie awake silently, and feel gathered around. i wonder if i could be lonely if i tried. i touch the button by my pillow. i listen to great cities tending me. i have found all the earth paved, or carpeted, or hung, or thrilled through with my brother's thoughts for me. i cannot hide from love. he has hired oceans to do my errands. he has made the whole human race my house-servants. i lie in my berth for sheer joy, thinking of the strange peoples where the morning is, running to and fro for me, down under the dark. next me, the great quiet throb of the engine--between me and infinite space--beating comfortably. i cannot help answering to it--this soft and mighty reaching out where i lie. my thoughts follow along the great twin shafts my brother holds me with. i wonder about them. i wish to do and share with them. were i a spirit i would go where the murmuring axles of the screws along their whirling aisles break through the hold, where they lift the awful shining thews of thought, of trade, and strike the sea till the scar of london lies miles and miles upon its breast out in the west. as i lie and look out of my port-hole and watch the starlight stepping along the sea i let my soul go out and visit with it. the ship i am in--a little human beckoning between two deserts. out through my port-hole i seem to see other ships, ghosts of great cities--an ocean of them, creeping through their still huge picture of the night, with their low hoarse whistles meeting one another, whispering to one another under the stars. "and they are all mine," i say, "hastening gently." i lie awake thinking of it. i let my whole being float out upon the thought of it. the bare thought of it, to me, is like having lived a great life. it is as if i had been allowed to be a great man a minute. i feel rested down through to before i was born. the very stars, after it, seem rested over my head. i have gathered my universe about me. it is as if i had lain all still in my soul and some beautiful eternal sleep--a minute of it--had come to me and visited me. all men are my brothers. is not the world filled with hastening to me? what is there my brother has not done for me? from the uttermost parts of the morning, all things that are flow fresh and beautiful upon my flesh. he has laid my will on the heavens. his machines are like the tides that do not stop. they are a part of the vast antennã¦ of the earth. they have grown themselves upon it. like wind and vapor and dust, they are a part of the furnishing of the earth. if i am cold and seek furs alaska is as near as the next snowdrift. my brother has caused it to be so. everywhere is five cents away. i take tea in pekin with a spoon from australia and a saucer from dresden. with the handle of my knife from india and the blade from sheffield, i eat meat from kansas. thousands of miles bring me spoonfuls. the taste in my mouth, five or six continents have made for me. the isles of the sea are on the tip of my tongue. and this is the thing my brother means, the thing he has done for me, solitary. i keep saying it over to myself. i lie still and try to take it in--to feel the touch of the hands of his hands. does any one say this thing he is doing is done for money--that it is not done for comradeship or love? could money have thought of it or dared it or desired it? could all the money in the world ever pay him for it? this paper-ticket i give him--for this berth i lie in--does it pay him for it? do i think to pay my fare to the infinite?--i--a parasite of a great roar in a city? these seven nights in the hollow of his hand he has held me and let me look upon the heaped-up stillness in heaven--of clouds. i have visited with the middle of the sea. and now with a thought, have i furnished my hot plain and smoke forever. i have not time to dream. i spell out each night, before i sleep, some vast new far-off love, this new daily sense of mutual service, this whole round world to measure one's being against. crowds wait on me in silence. i tip nations with a nickel. who would believe it? i lie in my berth and laugh at the bigness of my heart. when i go out on the meadow at high noon and in the great sleepy sunny silence there i stand and watch that long imperious train go by putting together the white mountains and new york, it is no longer as it was at first, a mere train by itself to me,--a flash of parlor cars between a great city and a sky up on mt. washington. when it swings up between my two little mountains its huge banner of steam and smoke, it is the beckoning of the other trains, the whole starful, creeping through the alps (that moment), stealing up the andes, roaring through the sun or pounding through the dark on the under sides of the world. in the great silence on the meadow after the train rolls by, it would be hard to be lonely for a minute, not to stand still, not to share in spirit around the earth a few of the big, happy things--the far unseen peoples in the sun, the streets, the domes and towers, the statesmen, and poets, but always between and above and beneath the streets and the domes and the towers, and the statesmen and poets--always the engineers,--i keep seeing them--these men who dip up the world in their hands, who sweep up life ... long, narrow, little towns of souls, and bowl them through the days and nights. in this huge, bottomless, speechless, modern world--one would rather be running the poems than writing them. at night i turn in my sleep. i hear the midnight mail go by--that same still face before it, the great human headlight of it. i lie in my bed wondering. and when the thunder of the face has died away, i am still wondering. out there on the roof of the world, thundering alone, thundering past death, past glimmering bridges, past pale rivers, folding away villages behind him (the strange, soft, still little villages), pounding on the switch-lights, scooping up the stations, the fresh strips of earth and sky.... the cities swoon before him ... swoon past him. thundering past his own thunder, echoes dying away ... and now out in the great plain, out in the fields of silence, drinking up mad splendid, little black miles.... every now and then he thinks back over his shoulder, thinks back over his long roaring, yellow trail of souls. he laughs bitterly at sleep, at the men with tickets, at the way the men with tickets believe in him. he knows (he grips his hand on the lever) he is not infallible. once ... twice ... he might have ... he almost.... then suddenly there is a flash ahead ... he sets his teeth, he reaches out with his soul ... masters it, he strains himself up to his infallibility again ... all those people there ... fathers, mothers, children, ... sleeping on their arms full of dreams. he feels as the minister feels, i should think, when the bells have stopped on a sabbath morning, when he stands in his pulpit alone, alone before god ... alone before the great silence, and the people bow their heads. but i have found that it is not merely the machines that one can see at a glance are woven all through with men (like the great trains) which make the big companions. it is a mere matter of getting acquainted with the machines and there is not one that is not woven through with men, with dim faces of vanished lives--with inventors. i have seen great wheels, in steam and in smoke, like swinging spirits of the dead. i have been told that the inventors were no longer with us, that their little tired, old-fashioned bodies were tucked in cemeteries, in the crypts of churches, but i have seen them with mighty new ones in the night--in the broad day, in a nameless silence, walk the earth. inventors may not be put like engineers, in show windows in front of their machines, but they are all wrought into them. from the first bit of cold steel on the cowcatcher to the little last whiff of breath in the air-brake, they are wrought in--fibre of soul and fibre of body. as the sun and the wind are wrought in the trees and rivers in the mountains, they are there. there is not a machine anywhere, that has not its crowd of men in it, that is not full of laughter and hope and tears. the machines give one some idea, after a few years of listening, of what the inventors' lives were like. one hears them--the machines and the men, telling about each other. there are days when it has been given to me to see the machines as inventors and prophets see them. on these days i have seen inventors handling bits of wood and metal. i have seen them taking up empires in their hands and putting the future through their fingers. on these days i have heard the machines as the voices of great peoples singing in the streets. * * * * * and after all, the finest and most perfect use of machinery, i have come to think, is this one the soul has, this awful, beautiful daily joy in its presence. to have this communion with it speaking around one, on sea and land, and in the low boom of cities, to have all this vast reaching out, earnest machinery of human life--sights and sounds and symbols of it, beckoning to one's spirit day and night everywhere, playing upon one the love and glory of the world--to have--ah, well, when in the last great moment of life i lay my universe out in order around about me, and lie down to die, i shall remember i have lived. this great sorrowing civilization of ours, which i had seen before, always sorrowing at heart but with a kind of devilish convulsive energy in it, has come to me and lived with me, and let me see the look of the future in its face. and now i dare look up. for a moment--for a moment that shall live forever--i have seen once, i think--at least once, this great radiant gesturing of man around the edges of a world. i shall not die, now, solitary. and when my time shall come and i lie down to do it, oh, unknown faces that shall wait with me,--let it not be with drawn curtains nor with shy, quiet flowers of fields about me, and silence and darkness. do not shut out the great heartless-sounding, forgetting-looking roar of life. rather let the windows be opened. and then with the voice of mills and of the mighty street--all the din and wonder of it,--with the sound in my ears of my big brother outside living his great life around his little earth, i will fall asleep. bird's-eye view of this book part one i. the word beautiful in 1905 is no longer shut in with its ancient rim of hills, or with a show of sunsets, or with bouquets and doilies and songs of birds. it is a man's word, says the twentieth century. "if a hill is beautiful. so is the locomotive that conquers a hill." ii. the modern literary man--slow to be converted, is already driven to his task. living in an age in which nine-tenths of his fellows are getting their living out of machines, or putting their living into them, he is not content with a definition of beauty which shuts down under the floor of the world nine tenths of his fellowbeings, leaves him standing by himself with his lonely idea of beauty, where--except by shouting or by looking down through a hatchway he has no way of communing with his kind. iii. unless he can conquer the machines, interpret them for the soul or the manhood of the men about him he sees that after a little while--in the great desert of machines, there will not be any men. a little while after that there will not be any machines. he has come to feel that the whole problem of civilization turns on it--on what seems at first sight an abstract or literary theory--that there is poetry in machines. if we cannot find a great hope or a great meaning for the machine-idea in its simplest form, the machines of steel and flame that minister to us, if inspiring ideas cannot be connected with a machine simply because it is a machine, there is not going to be anything left in modern life with which to connect inspiring ideas. all our great spiritual values are being operated as machines. to take the stand that inspiring ideas and emotions can be and will be connected with machinery is to take a stand for the continued existence of modern religion (in all reverence) the god-machine, for modern education, the man-machine, for modern government, the crowd-machine, for modern art, the machine that expresses the crowd, and for modern society--the machine in which the crowd lives. iv. v. the poetry in machinery is a matter of fact. the literary men who know the men who know the machines, the men who live with them, the inventors, and engineers and brakemen have no doubts about the poetry in machinery. the real problem that stands in the way of interpreting and bringing out the poetry in machinery, instead of being a literary or ã¦sthetic problem is a social one. it is in getting people to notice that an engineer is a gentleman and a poet. vi. the inventor is working out the passions and the freedoms of the people, the tools of the nations. the people are already coming to look upon the inventor under our modern conditions as the new form of prophet. if what we call literature cannot interpret the tools that men are daily doing their living with, literature as a form of art, is doomed. so long as men are more creative and godlike in engines than they are in poems the world listens to engines. if what we call the church cannot interpret machines, the church as a form of religion loses its leadership until it does. a church that can only see what a few of the men born in an age, are for, can only help a few. a religion that lives in a machine-age and that does not see and feel the meaning of that age, is not worthy of us. it is not even worthy of our machines. one of the machines that we have made could make a better religion than this. part two the language of the machines i. i have heard it said that if a thing is to be called poetic it must have great ideas in it and must successfully express them; that the language of the machines, considered as an expression of the ideas that are in the machines, is irrelevant and absurd. but all language looked at in the outside way that men have looked at machines, is irrelevant and absurd. we listen solemnly to the violin, the voice of an archangel with a board tucked under his chin. except to people who have tried it, nothing could be more inadequate than kissing as a form of human expression, between two immortal infinite human beings. ii. the chief characteristic of the modern machine as well as of everything else that is strictly modern is that it refuses to show off. the man who is looking at a twin-screw steamer and who is not feeling as he looks at it the facts and the ideas that belong with it, is not seeing it. the poetry is under water. iii. i have heard it said that the modern man does not care for poetry. it would be truer to say that he does not care for old-fashioned poetry--the poetry that bears on. the poetry in a dutch windmill flourishes and is therefore going by, to the strictly modern man. the idle foolish look of a magnet appeals to him more. its language is more expressive and penetrating. he has learned that in proportion as a machine or anything else is expressive--in the modern language, it hides. the more perfect or poetic he makes his machines the more spiritual they become. his utmost machines are electric. electricity is the modern man's prophet. it sums up his world. it has the modern man's temperament--the passion of being invisible and irresistible. iv. poetry and religion consist--at bottom, in being proud of god. most men to-day are worshipping god--at least in secret, not merely because of this great machine that he has made, running softly above us--moonlight and starlight ... but because he has made a machine that can make machines, a machine that shall take more of the dust of the earth and of the vapor of heaven and crowd it into steel and iron and say "go ye now,--depths of the earth, heights of heaven--serve ye me! stones and mists, winds and waters and thunder--the spirit that is in thee is my spirit. i also, even i also am god!" v. everything has its language and the power of feeling what a thing means, by the way it looks, is a matter of noticing, of learning the language. the language of the machines is there. i cannot precisely know whether the machines are expressing their ideas or not. i only know that when i stand before a foundry hammering out the floors of the world, clashing its awful cymbals against the night, i lift my soul to it, and in some way--i know not how, while it sings to me, i grow strong and glad. part three the machines as poets i. ii. machinery has poetry in it because it expresses the soul of man--of a whole world of men. it has poetry in it because it expresses the individual soul of the individual man who creates the machine--the inventor, and the man who lives with the machine--the engineer. it has poetry in it because it expresses god. he is the kind of god who can make men who can make machines. iii. iv. machinery has poetry in it because in expressing the man's soul it expresses the greatest idea that the soul of man can have--the man's sense of being related to the infinite. it has poetry in it not merely because it makes the man think he is infinite but because it is making the man as infinite as he thinks he is. when i hear the machines, i hear man saying, "god and i." v. machinery has poetry in it because in expressing the infinity of man it expresses the two great immeasurable ideas of poetry and of the imagination and of the soul in all ages--the two forms of infinity--the liberty and the unity of man. the substance of a beautiful thing is its idea. a beautiful thing is beautiful in proportion as its form reveals the nature of its substance, that is, conveys its idea. machinery is beautiful by reason of immeasurable ideas consummately expressed. part four the ideas behind the machines the ideas of machinery in their several phases are sketched in chapters as follows: i. ii. the idea of the incarnation. the god in the body of the man. iii. the idea of liberty--the soul's rescue from environment. iv. the idea of immortality. v. the idea of god. vi. the idea of the spirit--of the unseen and intangible. vii. the practical idea of invoking great men. viii. the religious idea of love and comradeship. * * * * * note.--the present volume is the first of a series which had their beginnings in some articles in the _atlantic_ a few years ago, answering or trying to answer the question, "can a machine age have a soul?" perhaps it is only fair to the present conception, as it stands, to suggest that it is an overture, and that the various phases and implications of machinery--the general bearing of machinery in our modern life, upon democracy, and upon the humanities and the arts, are being considered in a series of three volumes called: i. the voice of the machines. ii. machines and millionaires. iii. machines and crowds. by the same author about an old new england church. _$1.00._ "i have read it twice and enjoyed it the second time even more than the first."--_oliver wendell holmes._ "i read the preface, and that one little bite out of the crust made me as hungry as a man on a railroad. what a bright evening full of laughter, touched every now and then with tenderness, it made for us i do not know how to tell. here is a book i am glad to indorse as i would a note--right across the face and present it for payment in any man's library."--_robert j. burdette._ the child and the book. _$.75._ (_g. p. putnam's sons._) "i must express with your connivance the joy i have had, the enthusiasm i have felt, in gloating over every page of what i believe is the most brilliant book of any season since carlyle's and emerson's pens were laid aside. it is full of humor, rich in style, and eccentric in form, and all suffused with the perfervid genius of a man who is not merely a thinker but a force. every sentence is tinglingly alive.... "i have been reading with wonder and laughter and with loud cheers. it is the word of all words that needed to be spoken just now. it makes me believe that after all we haven't a great kindergarten about us in authorship, but that there is virtue, race, sap in us yet. i can conceive that the date of the publication of this book may well be the date of the moral and intellectual renaissance for which we have long been scanning the horizon."--wm. sloane kennedy, in _boston transcript_. the lost art of reading. _$1.00._ (_g. p. putnam's sons._) "it is a real pleasure to chronicle an intellectual treat among the books of the day. some of us will shrug at this volume. others of us having read it will keep it near us."--_life_. "mr. lee is a writer of great courage, who ventures to say what some people are a little alarmed even to think."--_springfield republican_. "you get right in between the covers and live."--_denver post_. the shadow christ. _$1.25._ (_the century co._) "let me be one of the first to recognize in this book what every man who reads it thoughtfully will feel. heaps of the books that have been written about the bible are desiccated to the last grain of their dust. they are the desert which lies around palestine. now and then a man appears who makes his way straight into the promised land, by sea if necessary, and takes you with him. it is not meant to be a full, precise treatment of the subject. it is history seen in a vision. theology expressed in a lyric. criticism condensed into an epigram."--dr. henry van dyke, in _the book buyer_. "the author's name--gerald stanley lee--has been hitherto unknown to us in england, but the book he has here offered to the world indicates that he has that in him which will soon make it familiar."--_the christian world_ (london). mount tom. an all outdoors magazine, devoted to rest and worship, and to a little look-off on the world. edited by mr. lee. every other month. 12 copies, $1.00. the voice of the machines. _$1.25._ (_mt. tom press._) any of the above mailed postpaid ordered direct from the mount tom press, northampton, mass. transcriber's notes italic text is denoted by _underscores_. the oe ligature has been expanded to 'oe'. subscripts in chemical formulas are denoted by normal numbers; for example cac2. obvious typographical and punctuation errors have been corrected after careful comparison with other occurrences within the text and consultation of external sources. more detail can be found at the end of the book. [illustration: a primitive use of the animal machine that is still in vogue in many european countries. (from the painting by j. didier, in the _musée du luxembourg_, paris.)] every-day science by henry smith williams, m.d., l.l.d. assisted by edward h. williams, m.d. volume vi the conquest of nature illustrated new york and london the goodhue company publishers mdccccix copyright, 1910, by the goodhue co. _all rights reserved_ contents chapter i man and nature the conquest of nature, p. 4--man's use of nature's gifts, p. 6--man the "tool-making animal," p. 7--science and civilization, p. 8--clothing and artificially heated dwellings of primitive man, p. 10--early domestication of animals, p. 11--early development to the time of gunpowder, p. 12--the coming of steam and electricity, p. 15--mechanical aids to the agriculturist, p. 19--the development of scientific agriculture, p. 20--difficulties of the early manufacturer, p. 21--the development of modern manufacturing, p. 24--the relation of work to human development, p. 25--the decline of drudgery and the new era of labor-saving devices, p. 27. chapter ii how work is done primitive man's use of the lever, p. 29--the use of the lever as conceived by archimedes, p. 21--wheels and pulleys, p. 32--other means of transmitting power, p. 35--inclined planes and derricks, p. 37--the steam-scoop, p. 38--friction, p. 39--available sources of energy, p. 41. chapter iii the animal machine the oldest machine in existence, p. 43--the relation of muscle to machinery, p. 44--how muscular energy is applied, p. 44--the two types of muscles, p. 45--how the nerve-telegraph controls the muscles, p. 47--the nature of muscular action, p. 49--applications of muscular energy, p. 52--the development of the knife and saw, p. 53--the wheel and axle, p. 55--modified levers, p. 57--domesticated animals, p. 59--early application of horse-power, p. 60--the horse-power as the standard of the world's work, p. 61. chapter iv the work of air and water first use of sails for propelling boats, p. 62--the fire engine of ctesibius, p. 63--suction and pressure as studied by the ancients, p. 64--studies of air pressure, p. 65--the striking demonstration of von guericke, p. 66--the sailing chariot of servinus, 1600 a.d., p. 68--the development of the windmill, p. 69--the development of the water-wheel, p. 70--the invention of the turbine, p. 72--different types of turbines, p. 73--hydraulic power and its uses, p. 74--the hydraulic elevator, p. 76--recent water motors, p. 77. chapter v captive molecules: the story of the steam engine the development of the steam engine, p. 79--the manner in which energy is generated by steam, p. 80--action of cylinder and piston, p. 81--early attempts to utilize steam, p. 82--beginnings of modern discovery, p. 83--the "engine" of the marquis of worcester, p. 84--thomas savery's steam pump, p. 85--denis papin invents the piston engine, p. 88--newcomen's improved engine, p. 89--the use of these engines in collieries, p. 90--the wastefulness of such engines, p. 92--the coming of james watt, p. 93--early experiments of watt, p. 95--the final success of watt's experiments, p. 97--some of his early engines, p. 98--rotary motion, p. 99--watt's engine, "old bess," p. 101--final improvements and missed opportunities, p. 102--the personality of james watt, p. 107. chapter vi the master worker improvements on watt's engines, p. 110--engines dispensing with the walking beam, p. 111--the development of high-pressure engines, p. 112--advantages of the high-pressure engine, p. 114--how steam acts in the high-pressure engine, p. 116--compound engines, p. 117--rotary engines, p. 119--turbine engines, p. 124--the _turbinia_ and other turbine boats, p. 125--the action of steam in the turbine engine, p. 126--advantages of the turbine engine, p. 127. chapter vii gas and oil engines some early gas engines, p. 133--dr. stirling's hot-air engine, p. 133--ericsson's hot-air engines, p. 134--the first practical gas engine, p. 135--the otto gas engine, p. 136--otto's improvement by means of compressed gas, p. 138--the "otto cycle," p. 139--adaptation of gas engines to automobiles, p. 140--rapid increase in the use of gas engines, p. 141--defects of the older hot-air engines, p. 145--recent improvements and possibilities in the use of hot-air engines, p. 146. chapter viii the smallest workers the relative size of atoms and electrons, p. 148--what is electricity? p. 149--franklin's one-fluid theory, p. 150--modern views, p. 153--cathode rays and the x-ray, p. 156--how electricity is developed, p. 159--the work of the dynamical current, p. 162--theories of electrical action, p. 165--practical uses of electricity, p. 168. chapter ix man's newest co-laborer: the dynamo the mechanism of the dynamo, p. 173--the origin of the dynamo, p. 176--the work of ampère, henry, and faraday, p. 177--perfecting the dynamo, p. 178--a mysterious mechanism, p. 180--curious relation between magnetism and electricity as exemplified in the dynamo, p. 182. chapter x niagara in harness the volume of water at the falls, p. 184--the point at which the falls are "harnessed," p. 185--within the power-house, p. 186--penstocks and turbines, p. 188--a miraculous transformation of energy, p. 189--subterranean tail-races, p. 191--the effect on the falls, p. 192--the transmission of power, p. 194--"step-up" and "step-down" transformers, p. 198. chapter xi the banishment of night primitive torch and open lamp, p. 202--tallow candle and perfected lamp, p. 205--gas lighting, p. 207--the incandescent gas mantle, p. 208--early gas mantles, p. 209--how the incandescent gas mantle is made, p. 211--the introduction of acetylene gas, p. 212--chemistry of acetylene gas, p. 214--practical gas-making, p. 215--the triumph of electricity, p. 218--davy and the first electric light, p. 220--helpful discoveries in electricity, p. 222--the jablochkoff candle, p. 223--defects of the jablochkoff candle, p. 225--the improved arc light, p. 226--edison and the incandescent lamp, p. 228--difficulties encountered in finding the proper material for a practical filament, p. 230--"parchmentized thread" filament, p. 233--the tungsten lamp, p. 234--the mercury-vapor light of peter cooper hewitt, p. 236--advantages and peculiarities of this light, p. 240. chapter xii the mineral depths early mining methods, p. 242--prospecting and locating mines, p. 243--"booming," p. 246--conditions to be considered in mining, p. 248--dangerous gases in mines, p. 249--artificial lights and lighting, p. 251--ventilation and drainage, p. 252--electric machinery in mining, p. 253--electric drills, p. 254--traction in mining, p. 256--various types of electric motors, p. 257--"telphers," p. 261--electric mining pumps, p. 263--some remarkable demonstrations of durability of electric pumps, p. 265--electricity in coal mining, p. 266--electric lighting in mines, p. 269. chapter xiii the age of steel rapid growth of the iron industry in recent years, p. 271--the lake superior mines, p. 272--methods of mining, p. 273--"open-pit" mining, p. 274--mining with the steam shovel, p. 276--from mine to furnace, p. 278--methods of transportation, p. 279--vessels of special construction, p. 281--the conversion of iron ore into iron and steel, p. 283--blast furnaces, p. 284--poisonous gases and their effect upon the workmen, p. 286--from pig iron to steel, p. 287--modern methods of producing pig iron, p. 288--the bessemer converter, p. 289--sir henry bessemer, p. 291--the "bessemer-mushet" process, p. 293--open-hearth method, p. 294--alloy steels, p. 295. chapter xiv some recent triumphs of applied science the province of electro-chemistry, p. 298--linking the laboratory with the workshop, p. 299--soda manufactories at niagara falls, p. 300--producing aluminum by the electrolytic process, p. 300--old and new methods compared, p. 301--nitrogen from the air, p. 303--what this discovery means to the food industries of the world, p. 304--prof. birkeland's method, p. 307--another method of nitrogen fixation, p. 309--cost of production, p. 312--electrical energy, p. 313--production of high temperatures with the electric arc, p. 314--the production of artificial diamonds by the explosion of cordite, p. 315--industrial problems of to-day and to-morrow, p. 316. illustrations a primitive use of the animal machine that is still in vogue in many european countries _frontispiece_ horse and cattle power _facing p._ 32 cranes and derricks " 38 a belgian milk-wagon " 56 two apparatuses for the utilization of animal power " 60 windmills of ancient and modern types " 68 water wheels " 72 hydraulic press and hydraulic capstan " 76 thomas savery's steam engine " 86 diagrams of early attempts to utilize the power of steam " 88 a model of the newcomen engine " 92 watt's earliest type of pumping-engine " 96 watt's rotative engine " 100 james watt " 108 old ideas and new applied to boiler construction " 114 compound engines " 118 rotary engines " 122 the original parsons' turbine engine and the record-breaking ship for which it is responsible " 128 gas and oil engines " 136 an electric train and the dynamo that propels it " 174 wilde's separately excited dynamo " 178 the evolution of the dynamo " 180 view in one of the power houses at niagara " 186 electrical transformers " 198 thomas a. edison and the dynamo that generated the first commercial incandescent light " 228 a flint-and-steel outfit, and a miner's steel mill " 248 the locomotive "puffing billy" and a modern colliery trolley " 258 the conquest of nature in the earlier volumes we have been concerned with the growth of knowledge. for the most part the scientific delvers whose efforts have held our attention have been tacitly unmindful, or even explicitly contemptuous, of the influence upon practical life of the phenomena to the investigation of which they have devoted their lives. they were and are obviously seekers of truth for the mere love of truth. but the phenomena of nature are not dissociated in fact, however much we may attempt to localize and classify them. and so it chances that even the most visionary devotee of abstract science is forever being carried into fields of investigation trenching closely upon the practicalities of every-day life. a black investigating the laws of heat is preparing the way explicitly, however unconsciously, for a watt with his perfected mechanism of the steam engine. similarly a davy working at the royal institution with his newly invented batteries, and intent on the discovery of new elements and the elucidation of new principles, is the direct forerunner of jablochkoff, brush, and edison with their commercial revolution in the production of artificial light. again oersted and faraday, earnestly seeking out the fundamental facts as to the relations of electricity and magnetism, invent mechanisms which, though they seem but laboratory toys, are the direct forerunners of the modern dynamos that take so large a share in the world's work. in a word, all along the line there is the closest association between what are commonly called the theoretical sciences and what with only partial propriety are termed the applied sciences. the linkage of one with the other must never be forgotten by anyone who would truly apprehend the status of those practical sciences which have revolutionized the civilization of the nineteenth and twentieth centuries in its most manifest aspects. nevertheless there is, to casual inspection, a somewhat radical distinction between theoretical and practical aspects of science--just as there are obvious differences between two sides of a shield. and as the theoretical aspects of science have largely claimed our attention hitherto, so its practical aspects will be explicitly put forward in the pages that follow. in the present volume we are concerned with those primitive applications of force through which man early learned to add to his working efficiency, and with the elaborate mechanisms--turbine wheels, steam engines, dynamos--through which he has been enabled to multiply his powers until it is scarcely exaggeration to say that he has made all nature subservient to his will. it is this view which justifies the title of the volume, which might with equal propriety have been termed the story of the world's work. the conquest of nature i man and nature "young men," said a wise physician in addressing a class of graduates in medicine, "you are about to enter the battle of life. note that i say the 'battle' of life. not a playground, but a battlefield is before you. it is a hard contest--a battle royal. make no mistake as to that. your studies here have furnished your equipment; now you must go forth each to fight for himself." the same words might be said to every neophyte in whatever walk of life. the pursuit of every trade, every profession is a battle--a struggle for existence and for supremacy. partly it is a battle against fellow men; partly against the contending powers of nature. the physician meets rivalry from his brothers; but his chief battle is with disease. in the creative and manufacturing fields which will chiefly concern us in the following volumes, it is the powers of nature that furnish an ever-present antagonism. no stone can be lifted above another, to make the crudest wall or dwelling, but nature--represented by her power of gravitation--strives at once to pull it down again. no structure is completed before the elements are at work defacing it, preparing its slow but certain ruin. summer heat and winter cold expand and contract materials of every kind; rain and wind wear and warp and twist; the oxygen of the air gnaws into stone and iron alike;--in a word, all the elements are at work undoing what man has accomplished. the struggle for existence in the field of the agriculturist it is the same story. the earth which brings forth its crop of unwholesome weeds so bountifully, resists man's approaches when he strives to bring it under cultivation. only by the most careful attention can useful grains be made to grow where the wildlings swarmed in profusion. not only do wind and rain, blighting heat and withering cold menace the crops; but weeds invade the fields, the germs of fungoid pests lurk everywhere; and myriad insects attack orchard and meadow and grain field in devastating legions. similarly the beasts which were so rugged and resistant while in the wild state, become tender and susceptible to disease when made useful by domestication. aforetime they roamed at large, braving every temperature and thriving in all weathers. but now they must be housed and cared for so tenderly that they become, as thoreau said, the keepers of men, rather than kept by men, so much more independent are they than their alleged owners. tender of constitution, domesticated beasts must be housed, to protect them from the blasts in which of yore their forebears revelled; and man must slave day in and day out to prepare food to meet the requirements of their pampered appetites. he must struggle, too, to protect them from disease, and must care for them in time of illness as sedulously as he cares for his own kith and kin. truly the ox is keeper of the man, and the seeming conquest that man has wrought has cost him dear. but of course the story has another side. after all, nature is not so malevolent as at first glance she seems. she has opposed man at every stage of his attempted progress; yet at the same time she has supplied him all his weapons for waging war upon her. her great power of gravitation opposes every effort he makes; yet without that same power he could do nothing--he could not walk or stay upon the earth even; and no structure that he builds would hold in place for an instant. so, too, the wind that smites him and tears at his handiwork, may be made to serve the purposes of turning his windmills and supplying him with power. the water will serve a like purpose in turning his mills; and, changed to steam with the aid of nature's store of coal, will make his steam engines and dynamos possible. even the lightning he will harness and make subject to his will in the telegraphic currents and dynamos. and in the fields, the grains which man struggles so arduously to produce are after all no thing of his creating. they are only adopted products of nature, which he has striven to make serve his purpose by growing them under artificial conditions. so, too, the domesticated beasts are creatures that belong in the wilds and in distant lands. man has brought them, in defiance of nature, to uncongenial climes, and made them serve as workers and as food-suppliers where nature alone could not support them. turn loose the cow and the horse to forage for themselves here in the inhospitable north, and they would starve. they survive because man helps them to combat the adverse conditions imposed by nature, yet no one of them could live for an hour were not the vital capacities supplied by nature still in control. everywhere, then, it is the opposing of nature, up to certain limits, with the aid of nature's own tools, that constitutes man's work in the world. just in proportion as he bends the elements to meet his needs, transforms the plants and animals, defies and exceeds the limitations of primeval nature--just in proportion as he conquers nature, in a word, is he civilized. barbaric man is called a child of nature with full reason. he must accept what nature offers. but civilized man is the child grown to adult stature, and able in a manner to control, to dominate--if you please to conquer--the parent. if we were to seek the means by which developing man has gradually achieved this conquest, we should find it in the single word, tools; that is to say, machines for utilizing the powers of nature, and, as it were, multiplying them for man's benefit. so unique is the capacity that man exerts in this direction, that he has been described as "the tool-making animal." the description is absolutely accurate; it is inclusive and exclusive. no non-human animal makes any form of implement to aid it in performing its daily work; and contrariwise every human tribe, however low its stage of savagery, makes use of more or less crude forms of implements. there must have been a time, to be sure, when there existed a man so low in intelligence that he had not put into execution the idea of making even the simplest tool. but the period when such a man existed so vastly antedates all records that it need not here concern us. for the purpose of classifying all existing men, and all the tribes of men of which history and pre-historic archæology give us any record, the definition of man as the tool-making animal is accurate and sufficient. at first thought it might seem that an equally comprehensive definition might describe man as the working animal. but a moment's consideration shows the fallacy of such a suggestion. man is, to be sure, the animal that works effectively, thanks to the implements with which he has learned to provide himself; but he shares with all animate creatures the task of laboring for his daily necessities. this is indeed a work-a-day world, and no creature can live in it without taking its share in that perpetual conflict which bodily necessities make imperative. most lower animals confine their work to the mere securing of food, and to the construction of rude habitations. some, indeed, go a step farther and lay up stores of food, in chance burrows or hollow trees; a few even manufacture relatively artistic and highly effective receptacles, as illustrated by the honeycomb made by the bees and their allies. again, certain animals, of which the birds are the best representatives, construct temporary structures for the purpose of rearing their young that attain a relatively high degree of artistic perfection. the baltimore oriole weaves a cloth of vegetable fibre that is certainly a wonderful texture to be made with the aid of claws and bill alone. it may be doubted whether human hands, unaided by implements, could duplicate it. but it is crude enough compared with even the coarsest cloth which barbaric races manufacture with the aid of implements. so it is with any comparison of animal work with the work of man, in whatever field. the crudest human endeavor is superior to the best non-human efforts; and the explanation is found always in the fact that the ingenuity of man has enabled him to find artificial aids that add to his power of manipulation. so large a share have these artificial aids taken in man's evolution, that it has long been customary, in studying the development of civilization, to make the use of various types of implements a test of varying stages of human progress. science and civilization the student of primitive life assures us, basing his statements on the archæological records, that there was a time when the most advanced of mankind had no tools made of better material than chipped stone. by common consent that time is spoken of as the rough stone age. we are told that then in the course of immeasurable centuries man learned to polish his stone implements, doubtless by rubbing them against another stone, or perhaps with the aid of sand, thus producing a new type of implement which has given its name to the age of smooth or polished stone. then after other long centuries came a time when man had learned to smelt the softer metals, and the new civilization which now supplanted the old, and, thanks to the new implements, advanced upon it immeasurably, is called the age of bronze. at last man learned to accomplish the wonderful feat of smelting the intractable metal, iron, and in so doing produced implements harder, sharper, and cheaper than his implements of bronze; and when this crowning feat had been accomplished, the age of iron was ushered in. by common consent, students of the history of the evolution of society accept these successive ages, each designated by the type of implements with which the world's work was accomplished, as representing real and definite stages of human progress, and as needing no better definition than that supplied by the different types of implements. could the archæologist trace the stream of human progress still farther back toward its source, he would find doubtless that there were several great epochal inventions preceding the time of the rough stone age, each of which was in its way as definitive and as revolutionary in its effects upon society, as these later inventions which we have just named. to attempt to define them clearly is to enter the field of uncertainty, but two or three conjectures may be hazarded that cannot be very wide of the truth. it is clear, for example, that if we go back in imagination to the very remotest ancestors of man that can be called human, we must suppose a vast and revolutionary stage of progress to have been ushered in by the first race of men that learned to make habitual use of the simplest implement, such as a mere club. when man had learned to wield a club and to throw a stone, and to use a stone held in the hand to break the shell of a nut, he had attained a stage of culture which augured great things for the future. out of the idea of wielded club and hurled stone were to grow in time the ideas of hammer and axe and spear and arrow. then there came a time--no one dare guess how many thousands of years later--when man learned to cover his body with the skin of an animal, and thus to become in a measure freed from the thraldom of the weather. he completed his enfranchisement by learning to avail himself of the heat provided by an artificial fire. equipped with these two marvelous inventions he was able to extend the hitherto narrow bounds of his dwelling-place, passing northward to the regions which at an earlier stage of his development he dared not penetrate. under stress of more exhilarating climatic conditions, he developed new ideals and learned to overcome new difficulties; developing both a material civilization and the advanced mentality that is its counterpart, as he doubtless never would have done had he remained subject to the more pampering conditions of the tropics. the most important, perhaps, of the new things which he was taught by the seemingly adverse conditions of an inhospitable climate, was to provide for the needs of a wandering life and of varying seasons by domesticating animals that could afford him an ever-present food supply. in so doing he ceased to be a mere fisher and hunter, and became a herdsman. one other step, and he had conceived the idea of providing for himself a supply of vegetable foods, to take the place of that which nature had provided so bountifully in his old home in the tropics. when this idea was put into execution man became an agriculturist, and had entered upon the high road to civilization. all these stages of progress had been entered upon prior to the time of which the oldest known remains of the cave-dweller give us knowledge. it were idle to conjecture the precise sequence in which these earliest steps toward civilization were taken, and even more idle to conjecture the length of time which elapsed between one step and its successor. but all questions of precise sequence aside, it is clear that here were four or five great ages succeeding one to another, that marked the onward and upward progress of our primeval ancestor before he achieved the stage of development that enabled him to leave permanent records of his existence. and--what is particularly significant from our present standpoint--it is equally clear that each of the great ages thus vaguely outlined was dependent upon an achievement or an invention that facilitated the carrying out of that scheme of never-ending work which from first to last has been man's portion. how to labor more efficiently, more productively; how to produce more of the necessaries and of the luxuries that man's physical and mental being demands, with less expenditure of toil--that from first to last has been the ever-insistent problem. and the answer has been found always through the development of some new species of mechanism, some new labor-saving device, some ingenious manipulation of the powers of nature. if, turning from the hypothetical period of our primitive ancestor, we consider the sweep of secure and relatively recent history, we shall find that precisely the same thing holds. if we contrast the civilization of old egypt and babylonia--the oldest civilizations of which we have any secure record--with the civilization of to-day, we shall find that the differences between the one and the other are such as are due to new and improved methods of accomplishing the world's work. indeed, if we view the subject carefully, it will become more and more evident that the only real progress that the historic period has to show is such as has grown directly from the development of new mechanical inventions. the more we study the ancient civilizations the more we shall be struck with their marvelous resemblance, as regards mental life, to the civilization of to-day. in their moral and spiritual ideals, the ancient egyptians were as brothers to the modern europeans. in philosophy, in art, in literature, the age of pericles established standards that still remain unexcelled. in all the subtleties of thought, we feel that the greeks had reached intellectual bounds that we have not been able to extend. but when, on the other hand, we consider the material civilization of the two epochs, we find contrasts that are altogether startling. the little world of the greeks nestled about the mediterranean, bounded on every side at a distance of a few hundred leagues by a _terra incognita_. the philosophers who had reached the confines of the field of thought, had but the narrowest knowledge of the geography of our globe. they traversed at best a few petty miles of its surface on foot or in carts; and they navigated the mediterranean sea, or at most coasted out a little way beyond the pillars of hercules in boats chiefly propelled by oars. by dint of great industry they produced a really astonishing number of books, but the production of each one was a long and laborious task, and the aggregate number indited during the age of pericles in all the world was perhaps not greater than an afternoon's output of a modern printing press. in a word, these men of the classical period of antiquity, great as were their mental, artistic, and moral achievements, were as children in those matters of practical mechanics upon which the outward evidences of civilization depend. should we find a race of people to-day in some hitherto unexplored portion of the earth--did such unexplored portions still exist--living a life comparable to that of the age of pericles, we should marvel no doubt at their artistic achievements, while at the same time regarding them as scarcely better than barbarians. indeed this is more than unsupported hypothesis; for has it not been difficult for the western world to admit the truly civilized condition of the chinese, simply because that highly intellectual race of orientals has not kept abreast of the occidental changes in applied mechanics? say what we will, this is the standard which we of the western world apply as the test of civilization. if, sweeping over in retrospect the history of the world since the time when the egyptian and babylonian civilizations were at their height, we attempt some such classification of the stages of progress as that which we a moment ago applied to pre-historic times, we shall be led to some rather startling conclusions. in the broadest view, it will appear that the age which ushered in the historic period continued unbroken by the advance of any great revolutionary invention throughout the long centuries of pre-christian antiquity, and well into the so-called middle ages of our newer era. then came the invention of gunpowder, or at least its introduction to the western world--since the chinaman here lays claim to vague centuries of precedence. following hard upon the introduction of gunpowder, with its capacity to add to the destructive efficiency of man's most sinister form of labor, came a mechanism no less epoch-making in a far different field--the printing press. but even these inventions, great as was their influence upon the progress of civilization, can scarcely be considered, it seems to me, as taking rank with the great epochal discoveries that gave their names to the preceding ages. nor can any invention of the sixteenth or seventeenth century be hailed as really ushering in a new era. the invention for which that honor was reserved was a development of the eighteenth century; and did not come fully to its heritage until the early days of the nineteenth century. the invention was the application of steam to the purposes of mechanics. when this application was made, as wide a gap was crossed as that which separated the stone age from the age of metal; then the epoch in which the world was living when history begins was brought to a close, and a new era, the age of steam, was ushered in. scarcely had the world begun to adjust itself to the new conditions of the age of steam, when yet another power was made subservient to man's needs, and the age of steam was supplemented, not to say supplanted, by the age of electricity. of course the new progressive movements did not necessarily imply elimination of old conditions; they imply merely the subordination of old powers to newer and better ones. stone implements by no means ceased to have utility at once when metal implements came into vogue. bronze long held its own against iron, and still has its utility. and iron itself finds but an added sphere of usefulness in the age of steam and electricity. all great changes are relatively slow. it is only as we look back upon them and view them in perspective that they seem cataclysmic. gunpowder did not at once supplant the crossbow, and the cannon was long held to be inferior to the catapult. the printed book did not instantly make its way against the work of the scribe. neither did the steam engine immediately supplant water power and the direct application of human labor. but in each case the new invention virtually rang the death knell of the old method from the hour of its inauguration, and the end was no less sure because it was delayed. and it requires no great powers of divination to foretell that in the coming age, the electric dynamo driven by water power may take the place of the steam engine. the age of steam may pass, with only at most a few generations of domination. and it is within the possibilities that the age of electricity will scarcely come into its own before it may be displaced by an age of radio-activity. to press that point, however, would be to enter the field of prophecy, which is no part of my present purpose. all that i have wished to point out is that for some thousands of years after man learned to make implements of iron, the industrial world and the human civilization that depends upon it, pursued a relatively static course, like a broad, sluggish current, with no new revolutionary discovery to impel it into new channels; and that then one revolutionary discovery succeeded another with bewildering suddenness, so that we of the early days of the twentieth century are farther removed, in an industrial way, from our forerunners of two hundred years ago, than those children of the eighteenth century were from the earliest civilization that ever developed on our globe. indeed, this startling contrast would still hold true, were we to consider the newest era as compassing only the period of a single life. there are men living to-day who were born in that epoch when the steam engine was for the first time used to turn the wheels of factories. there are many men who can well remember the first practical application of steam to railway traffic. hosts of men can remember when the first commercial message was transmitted by electricity along a wire. even middle-aged men recall the first cable message that linked the old world with the new. and the application of the dynamo to the purposes of the world's work is an affair of but yesterday. the historian of the future, casting his eye back across the long perspective of history, will find civilized man pursuing an even and unbroken course across the ages from the time of the pyramids of egypt to about the time of the french revolution. there will be no dearth of incident to claim his attention in the way of wars and conquests, and changing creeds, and the rise and fall of nations, each pursuing virtually the same course of growth and decay as all the others. but when he comes to the close of the eighteenth century, it will not be the social paroxysm of a nation, or the meteoric career of a napoleon that will claim his attention so much as the introduction of that new method of utilizing the powers of nature which found its expression in the mechanism called the steam engine. if the name of any individual stands out as the great and memorable one of that epoch of transition, at which the static current of previous civilization changed suddenly to a niagara-current of progress, it will be the name of the great scientific inventor, rather than that of the great military conqueror--the name of james watt, rather than that of napoleon. the military conqueror had his day of surpassing glory and departed, to leave the world only a little worse than he found it. but the mechanical inventor left a heritage that was to add day by day to the wealth and happiness of humanity, supplying millions of artificial hands, and making possible such beneficent improvements as no previous age had dreamed of. tasks that human hands had performed slowly, laboriously, and inadequately, were now to be performed swiftly, with ease, and well by the artificial hands provided with the aid of the new power. where carts drawn by horses had toiled slowly across the land, and ships driven by the wind had drifted slowly through the waters, massive trains of cars were to hurtle to the four corners of the earth with inconceivable speed, and floating palaces were to course the waters with almost equal defiance to the limitations of time and space. and then there came that still weirder conquest of time and space, wrought by the electric current. the moment when man first spoke with man from continent to continent in defiance of the oceans, marked the dawning of that larger day when all mankind shall constitute one brotherhood and all peoples but a single nation. within a half century the sun of that new day has risen well above the horizon, and far sooner than even the optimist of to-day dare predict with certainty, it seems destined to reach its zenith. but here again we verge upon the dangerous field of prophecy. let us turn from it and cast an eye back across the most wonderful of centuries, contrasting the conditions of to-day in each of a half-dozen fields of the world's work, with the conditions that obtained at the close of the eighteenth century. such a brief survey will show us perhaps more vividly than we could otherwise be shown, how vast has been the progress, how marvelous the development of civilization, in the short decades that have elapsed since the coming of the age of steam. let us pay heed first to the world of the agriculturist. could we turn back to the days of our grandparents, we should find farming a very different employment from what it is to-day. for the most part the farmer operated but a few small fields; if he had thirty or forty acres of ploughed land, he found ample employment for his capacities. he ploughed his fields with the aid of either a yoke of oxen or a team of horses; he sowed his grain by hand; he cultivated his corn with a hoe; he reaped his oats and wheat with a cradle--a device but one step removed from a sickle; he threshed his grain with a flail; he ground such portion of it as he needed for his own use with the aid of water power at a neighboring mill; and such portion of it as he sold was transported to market, be it far or near, in wagons that compassed twenty or thirty miles a day at best. as regards live stock, each farmer raised a few cattle, sheep, and hogs, and butchered them to supply his own needs, selling the residue to a local dealer who supplied the non-agricultural portion of the neighborhood. any live stock intended for a distant market was driven on foot across the country to its destination. each town and city, therefore, drew almost exclusively for its supply from the immediately surrounding country. to-day the small farmer has become almost obsolete, and the farms of the eastern states that were the nation's chief source of supply a century ago are largely allowed to lie fallow, it being no longer possible to cultivate them profitably in competition with the rich farm lands of the middle west. in that new home of agriculture, the farm that does not comprise two or three hundred acres is considered small; and large farms are those that number their acres by thousands. the soil is turned by steam ploughs; the grain is sown with mechanical seeders and planters; the corn is cultivated with a horse-drawn machine, having blades that do the work of a dozen men; harvesters drawn by three or four horses sweep over the fields and leave the grain mechanically tied in bundles; the steam thresher places the grain in sacks by hundreds of bushels a day; and this grain is hurried off in steam cars to distant mills and yet more distant markets. meantime the raising of live stock has become a special department, with which the farmer who deals in cereals often has no concern. the cattle roam over vast pastures and are herded in the winter for fattening in great droves, and protected from the cold in barns that, when contrasted with the sheds of the old-time farmer, seem almost palatial. when in marketable condition, cattle are no longer slaughtered at the farm, but are transported in cars to one of the few great centres, chief of which are the stock yards of chicago and of kansas city. at these centres, slaughter houses and meat-packing houses of stupendous magnitude have been developed, capable of handling millions of animals in a year. from these centres the meat is transported in refrigerator cars to the seaboards, and in refrigerator ships to all parts of the world. beef that grew on the ranges of the far west may thus be offered for sale in the markets of new england villages, at a price that prohibits local competition. a more radical metamorphosis in agricultural conditions than all this implies could not well be conceived. and when we recall once more that the agricultural conditions that obtained at the beginning of the nineteenth century were closely similar to those that obtained in each successive age for a hundred preceding centuries, we shall gain a vivid idea of the revolutionizing effects of new methods of work in the most important of industries. it is little wonder that in this short time the world has not solved to the satisfaction of the economists all the new problems thus so suddenly developed. turn now to the manufacturing world. in the days of our great-grandparents almost every household was a miniature factory where cotton and wool were spun and the products were woven into cloth. it was not till toward the close of the eighteenth century--just at the time when watt was perfecting the steam engine--that arkwright developed the spinning-frame, and his successors elaborated the machinery that made possible the manufacture of cloth in wholesale quantities; and the nineteenth century was well under way before the household production of cloth had been entirely supplanted by factory production. it is nothing less than pitiful to contemplate in imagination our great-great-grandmothers--and all their forebears of the long centuries--drudging away day after day, year in and year out, at the ceaseless task of spinning and weaving--only to produce, as the output of a lifetime of labor, a quantity of cloth equivalent perhaps to what our perfected machine, driven by steam, and manipulated by a factory girl, produces each working hour of every day. similarly, carpets and quilts were of home manufacture; so were coats and dresses; and shoes were at most the product of the local shoemaker around the corner. in the kitchen, food was cooked over the coals of a great fireplace or in the brick oven connected with that fireplace. meat was supplied from a neighboring farm; eggs were the product of the housewife's own poultry yard; the son or daughter of the farmer milked the cow and drove her to and from the pasture; the milk was "set" in pans in the cellar--on a swinging shelf, preferably, to make it inaccessible to the rats; and twice a week the cream was made into butter in a primitive churn, the dasher of which was operated by the vigorous arm of the housewife herself, or by the unwilling arms of some one of her numerous progeny. to give variety to the dietary, fruits grown in the local garden or orchard were preserved, each in its season, by the industrious housewife, and stored away in the capacious cellar; where also might be found the supply of home-grown potatoes, turnips, carrots, parsnips, and cabbages to provide for the needs of the winter. fuel to supply the household needs, both for cooking and heating, was cut in the neighboring woodland, and carefully corded in the door-yard, where it provided most uncongenial employment for the youth of the family after school hours and of a saturday afternoon. the ashes produced when this wood was burned in the various fireplaces, were not wasted, but were carefully deposited in barrels, from which in due course lye was extracted by the simple process of pouring water over the contents of the barrel. meantime scraps of fat from the table were collected throughout the winter and preserved with equal care; and in due course on some leisure day in the springtime--heaven knows how a leisure day was ever found in such a scheme of domestic economy!--the lye drawn from the ash-barrels and the scraps of fat were put into a gigantic kettle, underneath which a fire was kindled; with the result that ultimately a supply of soft soap was provided the housewife, with which her entire establishment, progeny included, could be kept in a state of relative cleanness. the reader of these pages has but to cast his eye about him in the household in which he lives, and contrast the conditions just depicted with those of his every-day life, to realize what change has come over the aspects of household economy in the course of a short century. nor need he be told in each of the various departments of which the activities are here outlined, that the changes which he observes have been due to the application of machinery in all the essential lines of work in question. we need not pause to detail the multitudinous devices for the economy of household labor which owe their origin to the same agency. there still remains, to be sure, enough of drudgery in the task of the housewife; yet her most strenuous day seems a mere playtime in comparison with the average day of her maternal forebear of three or four generations ago. but we must not here pause for further outlines of a subject which it is the purpose of this and succeeding volumes to explicate in detail. all our succeeding chapters will but make it more clear how marvelous are the elaborations of method and of mechanism through which the world's work of to-day is accomplished. we shall consider first the mechanical principles that underlie work in general, passing on to some of the principal methods of application through which the powers of nature are made available. we shall then take up in succession the different fields of industry. we shall ask how the work of the agriculturist is done in the modern world; how the multitudinous lines of manufacture are carried out; how transportation is effected; we shall examine the _modus operandi_ of the transmission of ideas; we shall even consider that destructive form of labor which manifests itself in the production of mechanisms of warfare. as we follow out the stories of the all-essential industries we shall be led to realize more fully perhaps than we have done before, the meaning of work in its relations to human development; and in particular the meaning of modern work, as carried out with the aid of modern mechanical contrivances, in its relations to modern civilization. the full force of these relations may best be permitted to unfold itself as the story proceeds. there is, however, one fundamental principle which i would ask the reader to bear constantly in mind, as an aid to the full appreciation of the importance of our subject. it is that in considering the output of the worker we have constantly to do with one form or another of property, and that property is the very foundation-stone of civilization. "it is impossible," says morgan, in his work on ancient society, "to overestimate the influence of property in the civilization of mankind. it was the power that brought the aryan and semitic nations out of barbarism into civilization. the growth of the idea of property in the human mind commenced in feebleness and ended in becoming its master passion. governments and laws are instituted with primary reference to its creation, protection, and enjoyment. it introduced human slavery in its production; and, after the experience of several thousand years, it caused the abolition of slavery upon the discovery that the freeman was a better property-making machine." if, then, we recall that without labor there is no property, we shall be in an attitude of mind to appreciate the importance of our subject; we shall realize, somewhat beyond the bounds of its more tangible and sordid relations, the essential dignity, the fundamental importance--in a word, the true meaning--of work. undoubtedly there is a modern tendency to accept this view of the dignity of physical labor. at any rate, we differ from the savage in thinking it more fitting that man should toil than that his wife should labor to support him--though it cannot be denied that even now the number of physical toilers among women greatly exceeds the number of such toilers among men. but in whatever measure we admit this attitude of mind, there can be no question that it is exclusively a modern attitude. time out of mind, physical labor has been distasteful to mankind, and it is a later development of philosophy that appreciates the beneficence of the task so little relished. the barbarian forces his wife to do most of the work, and glories in his own freedom. early civilization kept conquered foes in thraldom, developing an hereditary body of slaves, whose function it was to do the physical work. the hebrew explained the necessity for labor as a curse imposed upon father adam and mother eve. plato and aristotle, voicing the spirit of the greeks, considered manual toil as degrading. to-day we hear much of the dignity of labor; but if we would avoid cant we must admit that now--scarcely less than in all the olden days--the physical toiler is such because he cannot help himself. few indeed are the manual laborers who know any other means of getting their daily bread than that which they employ. the most strenuous advocates of the strenuous life are not themselves tillers of the soil or workers in factories or machine shops. the farm youth of intelligence does not remain a farmer; he goes to the city, and we find him presently at the head of a railroad or a bank, or practising law or medicine. the more intelligent laborer becomes finally a foreman, and no longer handles the axe or sledge. we should think it grotesque were we to see a man of intellectual power obstinately following a pursuit that cost him habitual physical toil. when now and then a tolstoi offers an exception to this rule, we feel that he is at least eccentric; and we may be excused the doubt whether he would follow the manual task cheerfully if he did not know that he could at any moment abandon it. it is because he knows that the world understands him to be only a dilettante that he rejoices in his task. after all, then, judged by the modern practice, rather than by the philosopher's precept, the old hebrew and greek ideas were not so far wrong. using the poetical language which was so native to them, it might be said that the necessity for physical labor is a curse--a disgrace. a partial explanation of this may be found in the fact that the most uncongenial tasks are also the worst paid, while the congenial tasks command the high emoluments. generally speaking there is no distinction between one laborer and another in the same field--except where the eminently fair method of piece work can be employed. even the skilled laborer is usually paid by the day, and the amount he is to receive is commonly fixed by a union regardless of his efficiency as compared with other laborers of the same class. and there is no possibility of his receiving any such sums as the man who plans the work, but does nothing with his own hands. it has always been so. just as "those who think must govern those that toil," so the thinker must command the high reward. partly this is because man, considered as a mere toiler, is so relatively inefficient a worker. when he strives to work with his hands, his effort is but a pitiful one; he can by no possibility compete (as regards mere quantity of labor) with the ox and the horse. he is impatient of his own puerile efforts. it is only when he brings the products of ingenuity to his aid that he is able to show his superiority, and to justify his own egotism. so it is that in every age he has striven to find means of adding to his feeble powers of body through the use of his relatively gigantic powers of mind. and in proportion as he thus is able to "make his head work for his hands" as the saying goes, he verges toward the heights of civilization. to accomplish this more and more fully has ever been the task of science as applied to the industries. it will be our object in the ensuing chapters to inquire how far science has accomplished the protean task thus set for it. we shall see that much has been done; but that much still remains to be done. in proportion as the problems are unsolved, science is reproached for its shortcomings--and stimulated to new efforts. in proportion as labor has been minimized and production increased--in just that proportion has science justified itself; and in the same proportion has the conquest of nature been carried toward completion. ii how work is done the word energy implies capacity to do work. work, considered in the abstract, consists in the moving of particles of matter against some opposing force, or in aid of previously acting forces. in the last analysis, all energy manifests itself either as a push or as a pull. but there is a modification of push and pull which is familiar to everyone in practice under the name of prying. illustrations may be seen on every hand, as when a workman pries up a stone, or when a housewife pries up a tack with the aid of a hammer. the principle here involved is that of the lever--a principle which in its various practical modifications is everywhere utilized in mechanics. very seldom indeed is the direct push or pull utilized; since the modified push or pull, as represented by the lever in its various modifications of pulley, ratchet-wheel, and the like, has long been known to meet the needs of practical mechanics. the very earliest primitive man who came to use any implement whatever, though it were only a broken stick, must have discovered the essential principle of the lever, though it is hardly necessary to add that he did not know his discovery by any such high-sounding title. what he did know, from practical experience, was that with the aid of a stick he could pry up stones or logs that were much too heavy to be lifted without this aid. this practical knowledge no doubt sufficed for a vast number of generations of men who used the lever habitually, without making specific study of the relations between the force expended, the lengths of the two ends of the lever, and the weight raised. such specific experiments were made, however, more than two thousand years ago by the famous syracusan, archimedes. he discovered--or if some one else had discovered it before him, he at least recorded and so gains the credit of discovery--the specific laws of the lever, and he also pointed out that levers, all acting on the same principle, may be different as to their practical mechanism in three ways. first, the fulcrum may lie between the power and the weight, as in the case of the balance with which we were just experimenting. this is called a lever of the first class, and familiar illustrations of it are furnished by the poker, steelyard, or a pair of scissors. the so-called extensor muscles of the body--those for example, that cause the arm to extend--act on the bones in such a way as to make them levers of this first class. the second type of lever is that in which the weight lies between the force and the fulcrum, as illustrated by the wheelbarrow, or by an ordinary door. in the third class of levers the power is applied between weight and fulcrum, as illustrated by a pair of tongs, the treadle of a lathe, or by the flexor muscles of the arm, operating upon the bones of the forearm. but in each case, let it be repeated, precisely the same principles are involved, and the same simple law of the relations between positions of power, weight, and fulcrum are maintained. the practical result is always that a weight of indefinite size may be moved by a power indefinitely long. if one arm of the lever is ten times as long as the other, the power of one pound will lift or balance a ten-pound weight; if the one arm is a thousand times as long as the other the power of one pound will lift or balance a thousand pounds. if the long arm of the lever could be made some millions of miles in length, the power that a man could exert would balance the earth. how fully archimedes realized the possibilities of the lever is illustrated in the classical remark attributed to him, that, had he but a fulcrum on which to place his lever, he could move the world. as otherwise quoted, the remark of archimedes was that, had he a place on which to stand, he could move the world, a remark which even more than the other illustrates the full and acute appreciation of the laws of motion; since, as we have already pointed out, action and reaction being equal, the most infinitesimal push must be considered as disturbing even the largest body. tremendous as is the pull of gravity by which the earth is held in its orbit, yet the smallest push, steadily applied from the direction of the sun, would suffice ultimately to disturb the stability of our earth's motion, and to push it gradually through a spiral course farther and farther away from its present line of elliptical flight. or if, on the other hand, the persistent force were applied from the side opposite the sun, it would suffice ultimately to carry the earth in a spiral course until it plunged into the sun itself. indeed it has been questioned in modern times whether it may not be possible that precisely this latter effect is gradually being accomplished, through the action of meteorites, some millions of which fall out of space into the earth's atmosphere every day. if these meteorites were uniformly distributed through space and flying in every direction, the fact that the sun screens the earth from a certain number of them, would make the average number falling on the side away from the sun greater, and thus would in the course of ages produce the result just suggested. all that could save our earth from such a fate would be the operation of some counteracting force. such a counteracting force is perhaps found in solar radiation. it may be added that the distribution of meteorites in space is probably too irregular to make their influence on the earth predicable in the present state of science; but the principle involved is no less sure. wheels and pulleys returning from such theoretical applications of the principle of motion, to the practicalities of every-day mechanisms, we must note some of the applications through which the principle of the lever is made available. of these some of the most familiar are wheels, and the various modifications of wheels utilized in pulleys and in cogged and bevelled gearings. a moment's reflection will make it clear that the wheel is a lever of the first class, of which the axle constitutes the fulcrum. the spokes of the wheel being of equal length, weights and forces applied to opposite ends of any diameter are, of course, in equilibrium. it follows that when a wheel is adjusted so that a rope may be run about it, constituting a simple pulley, a mechanism is developed which gives no gain in power, but only enables the operator to change the direction of application of power. in other words, pound weights at either end of a rope passed about a simple pulley are in equilibrium and will balance each other, and move through equal distances in opposite directions. [illustration: horse and cattle power. the large picture shows a model of a familiar mechanism for utilizing horse power. the small picture shows a similar apparatus in actual operation, actuated by cattle, in contemporary brittany.] if, however, two or more pulley wheels are connected, to make the familiar apparatus of a compound pulley, we have accomplished by an interesting mechanism a virtual application of the principle of the long and short arm of the lever, and the relations between the weight at the loose end of the rope and the weight attached to the block which constitutes virtually the short end of the lever, may be varied indefinitely, according to the number of pulley-wheels that are used. a pound weight may be made to balance a thousand-pound weight; but, of course, our familiar principle still holding, the pound weight must move through a distance of a thousand feet in order to move a thousand-pound weight through a distance of one foot. familiar illustrations of the application of this principle may be seen on every hand; as when, for example, a piano or a safe is raised to the upper window of a building by the efforts of men whose power, if directly expended, would be altogether inefficient to stir the weight. the pulley was doubtless invented at a much later stage of human progress than the simple lever. it was, however, well known to the ancients. it was probably brought to its highest state of practical perfection by archimedes, whose experiments are famous through the narrative of plutarch. it will be recalled that archimedes amazed the syracusan general by constructing an apparatus that enabled him, sitting on shore, to drag a ponderous galley from the water. plutarch does not describe in detail the apparatus with which this was accomplished, but it is obvious from his description of what took place, that it must have been a system of pulleys. it will be observed that the pulley is a mechanism that enables the user to transmit power to a distance. but this indeed is true in a certain sense of every form of lever. numberless other contrivances are in use by which power is transmitted, through utilization of the same principle of the lever, either through a short or through a relatively long distance. a familiar illustration is the windlass, which consists of a cylinder rotating on an axis propelled by a long handle, a rope being wound about the cylinder. this is a lever of the second class, the axis acting as fulcrum, and the rope operating about the circumference of the cylinder typifying the weight, which may be actually at a considerable distance, as in the case of the old-fashioned well with its windlass and bucket, or of the simple form of derrick sometimes called a sheerlegs. other means of transmitting power power is transmitted directly from one part of a machine to another, in the case of a great variety of machines, with the aid of cogged gearing wheels of various sizes. the modifications of detail in the application of these wheels may be almost infinite, but the principle involved is always the same. the case of two wheels toothed about the circumference, the teeth of the two wheels fitting into one another, illustrates the principle involved. a consideration of the mechanism will show that here we have virtually a lever fixed at both ends, represented by the radii of the two wheels, the power being applied through the axle of one wheel, and the weight, for purposes of calculation, being represented by the pressure of the teeth of one wheel upon those of the other. so this becomes a lever of the second class, and the relations of power between the two wheels are easily calculated from the relative lengths of the radii. if, for example, one radius is twice as long as the other, the transmission of power will be, obviously, in the proportion of two to one, and meantime the distance traversed by the circumference of one wheel will be twice as great as that traversed by the other. a modification of the toothed wheel is furnished by wheels which may be separated by a considerable distance, and the circumferences of which are connected by a belt or by a chain. the principle of action here is precisely the same, the belt or chain serving merely as a means of lengthening out our lever. the relative sizes of the wheels, and not the length of the belt or chain, is the determining factor as regards the relative forces required to make the wheels revolve. it is obvious all along, of course, since action and reaction are equal, that all of the relations in question are reciprocal. when, for example, we speak of a pound weight on the long end of a lever balancing a ten-pound weight on the short end, it is equally appropriate to speak of the ten-pound weight as balancing the one-pound weight. similarly, when power is applied to the lever, it may be applied at either end. ordinarily, to be sure, the power is applied at the long end, since the object is to lift the heavy weight; but in complicated machinery it quite as often happens that these conditions are reversed, and then it becomes desirable to apply strong power to the short end of the lever, in order that the relatively small weight may be carried through the long distance. in the inter-relations of gearing wheels, such conditions very frequently obtain, practical ends being met by a series of wheels of different sizes. but the single rule, already so often outlined, everywhere holds--wherever there is gain of power there is loss of distance, and we can gain distance only by losing power. the words gain and loss in this application are in a sense misnomers, since, as we have already seen, gain and loss are only apparent, but their convenience of application is obvious. a familiar case in which there is first loss of speed and gain of power, and then gain of speed at the expense of power in the same mechanism, is furnished by the bicycle, where (1) the crank shaft turns the sprocket wheel that constitutes a lever of the second class with gain of power; where (2) power is further augmented through transmission from the relatively large sprocket wheel to the small sprocket of the axle; and where (3) there is great loss of power and corresponding gain of speed in transmitting the force from the small sprocket wheel at the axle to the rubber rim of the bicycle proper, this last transmission representing a lever of the third class. the net gain of speed is tangibly represented by the difference in distance traversed by the man's feet in revolving the pedals, and the actual distance covered by the bicycle. inclined planes and derricks a less obvious application of the principle of reciprocal equivalence of distance and weight is furnished by the inclined plane, a familiar mechanism with the aid of which a great gain of power is possible. the inclined plane, like the lever, has been known from remotest antiquity. its utility was probably discovered by almost the earliest builders. diodorus siculus tells us that the great pyramids of egypt were constructed with the aid of inclined planes, based on a foundation of earth piled about the pyramids. diodorus, living at a period removed by some thousands of years from the day of the building of the pyramids, may or may not have voiced and recorded an authentic tradition, but we may well believe that the principle of the inclined plane was largely drawn upon by the mechanics of old egypt, as by later peoples. the law of the inclined plane is that in order to establish equilibrium between two weights, the one must be to the other as the height of the inclined plane is to its length. the steeper the inclined plane, therefore, the less will be the gain in power; a mechanical principle which familiar experience or the simplest experiment will readily corroborate. in its elemental form the inclined plane is not used very largely in modern machinery, but its modified form of the wedge and the screw have more utility. the screw, indeed, which is obviously an inclined plane adjusted spirally about a cylinder or a cone, is familiar to everyone, and is constantly utilized in applying power. the crane or derrick furnishes a familiar but relatively elaborate illustration of a mechanism for the transmission of power, in which all the various devices hitherto referred to are combined, without the introduction of any new principle. derricks have been employed from a very early day. the battering-rams of the ancient egyptians and babylonians, for example, were virtually derricks; and no doubt the same people used the device in raising stones to build their temples and city walls, and in putting into position such massive sculptures as the obelisks of egypt and the monster graven bulls and lions of nineveh and babylon. [illustration: cranes and derricks. the upper figure shows a floating derrick, the lower right-hand figure a combined derrick and weighing machine, and the lower left-hand figure a so-called sheerlegs, which is a simple derrick and windlass operated by hand or by steam power with the aid of compound pulleys.] the modern derrick, made of steel, and operated by steam or electricity, capable of lifting tons, yet absolutely obedient to the hand of the engineer, is a really wonderful piece of mechanism. a steam-scoop, for example, excavating a gravel bank, seems almost a thing of intelligence; as it gores into the bank scooping up perhaps a half ton of earth, its upward sweeping head reminds one of an angry bull. then as it swings leisurely about and discharges its load at just the right spot into an awaiting car, its hinged bottom swings back and forth two or three times before closing, with curious resemblance to the jaw of a dog; the similarity being heightened by the square bull-dog-headed shape of the scoop itself. yet this remarkable contrivance, with all its massive steel beams and chains and cog wheels, employs no other principles than the simple ones of lever and pulley and inclined plane that we have just examined. the power that must be applied to produce a given effect may be calculated to a nicety. the capacities of the machine are fully predetermined in advance of its actual construction. but of course this is equally true of every other form of power-transmitter with which the modern mechanical engineer has to deal. friction in making such calculations, however, there is an additional element which the engineer must consider, but which we have hitherto disregarded. in all methods of transmission of power, and indeed in all cases of the contact of one substance with another, there is an element of loss through friction. this is due to the fact that no substance is smooth except in a relative sense. even the most highly polished glass or steel, when viewed under the microscope, presents a surface covered with indentations and rugosities. this granular surface of even seemingly smooth objects, is easily visualized through the analogy of numberless substances that are visibly rough. yet the vast practical importance of this roughness is seldom considered by the casual observer. in point of fact, were it not for the roughened surface of all materials with which we come in contact, it would be impossible for any animal or man to walk, nor could we hold anything in our hands. anyone who has attempted to handle a fish, particularly an eel, fresh from the water, will recall the difficulty with which its slippery surface was held; but it may not occur to everyone who has had this experience that all other objects would similarly slip from the hand, had their surfaces a similar smoothness. the slippery character of the eel is, of course, due in large part to the relatively smooth surface of its skin, but partly also to the lubricant with which it is covered. any substance may be rendered somewhat smoother by proper lubrication; it is necessary, however, that the lubricant should be something which is not absorbed by the substance. thus, wood is given increased friction by being moistened with oil, but, on the other hand, is made slippery if covered with graphite, soap, or any other fatty substances that it does not absorb. recalling the more or less roughened surface of all objects, the source of friction is readily understood. it depends upon the actual jutting of the roughened surfaces, one upon the other. it virtually constitutes a force acting in opposition to the motion of any two surfaces upon each other. as between any different materials, under given conditions, it varies with the pressure, in a definite and measurable rate, which is spoken of as the coefficient of friction for the particular substances. it is very much greater where the two substances slide over one another than where the one rolls upon the other, as in the case of the wheel. the latter illustrates what is called rolling friction, and in practical mechanics it is used constantly to decrease the loss--as, for example, in the wheels of wagons and cars. the use of lubricants to decrease friction is equally familiar. without them, as everyone knows, it would be impossible to run any wheel continuously upon an axle at high speed for more than a very brief period, owing to the great heat developed through friction. friction is indeed a perpetual antagonist of the mechanician, and we shall see endless illustrations of the methods he employs to minimize its influence. on the other hand, we must recall that were it rendered absolutely _nil_, his machinery would all be useless. the car wheel, for example, would revolve indefinitely without stirring the train, were there absolutely no friction between it and the rail. available sources of energy we have pointed out that every body whatever contains a certain store of energy, but it has equally been called to our attention that, in the main, these stores of energy are not available for practical use. there are, however, various great natural repositories of energy upon which man is able to draw. the chief of these are, first, the muscular energy of man himself and of animals; second, the energy of air in motion; third, the energy of water in motion or at an elevation; and fourth, the molecular and atomic energies stored in coal, wood, and other combustible materials. to these we should probably add the energy of radio-active substances--a form of energy only recently discovered and not as yet available on a large scale, but which may sometime become so, when new supplies of radio-active materials have been discovered. it will be the object of succeeding chapters to point out the practical ways in which these various stores of energy are drawn upon and made to do work for man's benefit. iii the animal machine the muscular system is not only the oldest machine in existence, but also the most complex. moreover, it is otherwise entitled to precedence, for even to-day, in this so-called age of steam and electricity, the muscular system remains by far the most important of all machines. in the united states alone there are some twenty million horses doing work for man; and of course no machine of any sort is ever put in motion or continues indefinitely in operation without aid supplied by human muscles. all in all, then, it is impossible to overestimate the importance of this muscular machine which is at once the oldest and the most lasting of all systems of utilizing energy. the physical laws that govern the animal machine are precisely similar to those that are applied to other mechanisms. all the laws that have been called to our attention must therefore be understood as applying fully to the muscular mechanism. but in addition to these the muscular system has certain laws or methods of action of its own, some of which are not very clearly understood. the prime mystery concerning the muscle is its wonderful property of contracting. for practical purposes we may say that it has no other property; the sole function of the muscle is to contract. it can, of course, relax, also, to make ready for another contraction, but this is the full extent of its activities. a microscopic examination of the muscle shows that it is composed of minute fibres, each of which on contraction swells up into a spindle shape. a mass of such fibres aggregated together constitutes a muscle, and every muscle is attached at either extremity, by means of a tendon, to a bone. both extremities of a muscle are never attached to the same bone--otherwise the muscle would be absolutely useless. usually there is only a single bone between the two ends of a muscle, but in exceptional cases there may be more. as a rule, the main body of a muscle lies along the bone to which one end of it is attached, the other end of the muscle being attached to the contiguous bone placed not far from the point. the first bone, then, serves as a fulcrum on which the second bone moves as a lever, and, as already pointed out, the familiar laws of the lever operate here as fully as in the inanimate world. but a moment's reflection will make it clear that the object effected by this mechanism is the increase of motion with relative loss of energy. in other words, the muscular force is applied to the short end of the lever, and a far greater expenditure of force is required when the muscle contracts than the power externally manifested would seem to indicate. a moment's consideration of the mechanism of the arm, having regard to the biceps muscle which flexes the elbow, will make this clear. if a weight is held in the hand it is perhaps twelve inches from the elbow. if, while holding the weight, you will grasp the elbow with the other hand, you will feel the point of attachment of the biceps, and discover that it does not seem to be, roughly speaking, more than about an inch from the joint. obviously, then, if you are lifting a pound weight, the actual equivalent of energy expended by the contracting biceps must be twelve pounds. but, in the meantime, when the pound weight in your hand moves through the space of one inch, the muscle has contracted by one-twelfth of an inch; and you may sweep the weight through a distance of two feet by utilizing the two-inch contraction, which represents about the capacity of the muscle. a similar consideration of the muscles of the legs will show how the muscular system which is susceptible of but trifling variation in size, gives to the animal great locomotive power. with the aid of a series of levers, represented by the bones of our thighs, legs, and feet, we are able to stride along, covering three or four feet at each step, while no set of the muscles that effect this propulsion varies in length by more than two or three inches. it appears, then, that the muscular system gives a marvelous illustration of capacity for storing energy in a compact form and utilizing it for the development of motion. the two types of muscles the muscles of animals and men alike are divided into two systems, one called voluntary, the other involuntary. the voluntary muscles, as their name implies, are subject to the influence of the will, and under ordinary conditions contract in response to the voluntary nervous impulses. certain sets of them, indeed, as those having to do with respiration, have developed a tendency to rhythmical action through long use, and ordinarily perform their functions without voluntary guidance. their function may, however, become voluntary when attention is directed toward it, and is then subject to the action of the will within certain bounds. should a voluntary attempt be made, however, to prevent their action indefinitely, the so-called reflex mechanism presently asserts itself. all of which may be easily attested by anyone who will attempt to stop breathing. all systems of voluntary muscles are subject to the influence of habit, and may assume activities that are only partially recognized by consciousness. as an illustration in point, the muscles involved in walking come, in the case of every adult, to perform their function without direct guidance of the will. such was not the case, however, in the early stage of their development, as the observation of any child learning to walk will amply demonstrate. in the case of animals, however, even those muscles are so under the impress of hereditary tendencies as to perform their functions spontaneously almost from the moment of birth. these, however, are physiological details that need not concern us here. it suffices to recall that the voluntary muscles may be directed by the will, and indeed are always under what may be termed subconscious direction, even when the conscious attention is not directed to them. the strictly involuntary muscles, however, are placed absolutely beyond control of the will. the most important of these muscles are those that constitute the heart and the diaphragm, and that enter into the substance of the walls of blood vessels, and of the abdominal organs. it is obvious that the functioning of these important organs could not advantageously be left to the direction of the will; and so, in the long course of evolution they have learned, as it were, to take care of themselves, and in so doing to take care of the organism, to the life of which they are so absolutely essential. as the physiologist views the matter, no organism could have developed which did not correspondingly develop such involuntary action of the vital organs. it will be seen that the involuntary muscles differ from the voluntary muscles in that they are not connected with bones. instead of being thus attached to solid levers, they are annular in structure, and in contracting virtually change the size of the ring which their substance constitutes. each fibre in contracting may be thought of as pulling against other fibres, instead of against a bony surface, and the joint action changes the size of the organ, as is obvious in the pulsing of the heart. though the rhythmical contractions of the involuntary muscles are independent of voluntary control, it must not be supposed that they are independent of the control of the central nervous mechanism. on the contrary, the nerve supply sent out from the brain to the heart and to the abdominal organs is as plentiful and as important as that sent to the voluntary muscles. there is a centre in the brain scarcely larger than the head of a pin, the destruction of which will cause the heart instantly to cease beating forever. from this centre, then, and from the other centres of the brain, impulses are constantly sent to the involuntary muscles, which determine the rate of activity. nor are these centres absolutely independent of the seat of consciousness, as anyone will admit who recalls the varied changes in the heart's action under stress of varying emotions. that the voluntary muscles are controlled by the central nervous mechanism needs no proof beyond the appeal to our personal experiences of every moment. you desire some object that lies on the table in front of you, and immediately your hand, thanks to the elaborate muscular mechanism, reaches out and grasps it. and this act is but typical of the thousand activities that make up our every-day life. everyone is aware that the channel of communication between the brain and the muscular system is found in a system of nerves, which it is natural now-a-days to liken to a system of telegraph wires. we speak of the impulse generated in the brain as being transmitted along the nerves to the muscle, causing that to contract. we are even able to measure the speed of transfer of such an impulse. it is found to move with relative slowness, compassing only about one hundred and twelve feet per second, being in this regard very unlike the electric current with which it is so often compared. but the precise nature of this impulse is unknown. its effect, however, is made tangible in the muscular contraction which it is its sole purpose to produce. the essential influence of the nerve impulse in the transaction is easily demonstrable; for if the nerve cord is severed, as often happens in accidents, the muscle supplied by that nerve immediately loses its power of voluntary contraction. it becomes paralyzed, as the saying is. the nature of muscular action paying heed, now, to the muscle itself, it must be freely admitted that, in the last analysis, the activities of the substance are as mysterious and as inexplicable as are those involved in the nervous mechanism. it is easy to demonstrate that what we have just spoken of as a muscle fibre consists in reality of a little tube of liquid protoplasm, and that the change in shape of this protoplasm constitutes the contraction of which we are all along speaking. but just what molecular and atomic changes are involved in this change of form of the protoplasm, we cannot say. we know that the power to contract is the one universal attribute of living protoplasm. this power is equally wonderful and equally inexplicable, whether manifested in the case of the muscle cell or in the case of such a formless single-celled creature as the amoeba. when we know more of molecular and atomic force, we may perhaps be able to form a mental picture of what goes on in the structure of protoplasm when it thus changes the shape of its mass. until then, we must be content to accept the fact as being the vital one upon which all the movements of animate creatures depend. but if, here as elsewhere, the ultimate activities of molecules and atoms lie beyond our ken, we may nevertheless gain an insight into the nature of the substances involved. we know, for example, that the chief constituents of all protoplasm are carbon, hydrogen, oxygen, and nitrogen; and that with these main elements there are traces of various other elements such as iron, sulphur, phosphorus, and sundry salts. we know that when the muscle contracts some of these constituents are disarranged through what is spoken of as chemical decomposition, and that there results a change in the substance of the protoplasm, accompanied by the excretion of a certain portion of its constituents, and by the liberation of heat. carbonic acid gas, for example, is generated and is swept away from the muscular tissues in the ever active bloodstreams, to be carried to the lungs and there expelled--it being a noxious poison, fatal to life if retained in large quantities. equally noxious are other substances such as uric acid and its compounds, which are also results of the breaking down of tissue that attends muscular action. in a word, there is an incessant formation of waste products, due to muscular activity, the removal of which requires the constant service of the purifying streams of blood and of the various excretory organs. but this constant outflow of waste products from the muscle necessitates, of course, in accordance with the laws of the conservation of matter and of energy, an equally constant supply of new matter to take the place of the old. this supply of what is virtually fuel to be consumed, enabling the muscle to perform its work, is brought to the muscle through the streams of blood which flow from the heart in the arterial channels, and in part also through the lymphatic system. the blood itself gains its supply from the digestive system and from the lungs. the digestive system supplies water, that all-essential diluent, and a great variety of compounds elaborated into the proper pabulum; while the vital function of the lungs is to supply oxygen, which must be incessantly present in order that the combustion which attends muscular activity may take place. what virtually happens is that fuel is sent from the digestive system to be burned in the muscular system, with the aid of oxygen brought from the lungs. in this view, the muscular apparatus is a species of heat engine. in point of fact, it is a curiously delicate one as regards the range of conditions within which it is able to act. the temperature of any given organism is almost invariable; the human body, for example, maintains an average temperature of 98-2/5 degrees, fahrenheit. the range of variation from this temperature in conditions of health is rarely more than a fraction of a degree; and even under stress of the most severe fever the temperature never rises more than about eight degrees without a fatal result. that an organism which is producing heat in such varying quantities through its varying muscular activities should maintain such an equilibrium of temperature, would seem one of the most marvelous of facts, were it not so familiar. the physical means by which the heat thus generated is rapidly given off, on occasion, to meet the varying conditions of muscular activity, is largely dependent upon the control of the blood supply, in which involuntary muscles, similar to those of the heart, are concerned. in times of great muscular activity, when the production of heat is relatively enormous, the arterioles that supply the surface of the body are rapidly dilated so that a preponderance of blood circulates at the surface of the body, where it may readily radiate its heat into space; the vast system of perspiratory ducts, with which the skin is everywhere supplied, aiding enormously in facilitating this result, through the secretion of a film of perspiration, which in evaporating takes up large quantities of heat. the flushed, perspiring face of a person who has violently exercised gives a familiar proof of these physiological changes; and the contrary condition, in which the peripheral circulation is restricted, and in which the pores are closed, is equally familiar. moreover, the same cutaneous mechanism is efficient in affording the organism protection from the changes of external temperature; though the human machine, thanks to the pampering influence of civilization, requires additional protection in the form of clothing. applications of muscular energy having thus outlined the conditions under which the muscular machine performs its work, we have now to consider briefly the external mechanisms with the aid of which muscular energy is utilized. of course, the simplest application of this power, and the one universally employed in the animal world is that in which a direct push or pull is given to the substance, the position of which it is desired to change. we have already pointed out that there is no essential difference between pushing and pulling. the fact receives another illustration in considering the muscular mechanism. we speak of pushing when we propel something away from a body, of pulling when we draw something toward it, yet, as we have just seen, each can be accomplished merely through the contraction of a set of muscles, acting on differently disposed levers. all the bodily activities are reducible to such muscular contractions, and the diversified movements in which the organism constantly indulges are merely due to the large number and elaborate arrangement of the bony levers upon which these muscles are operated. we may well suppose that the primitive man continued for a long period of time to perform all such labors as he undertook without the aid of any artificial mechanism; that is to say, without having learned to gain any power beyond that which the natural levers of his body provided. a brief observation of the actions of a man performing any piece of manual labor will, however, quickly demonstrate how ingeniously the bodily levers are employed, and how by shifting positions the worker unconsciously makes the most of a given expenditure of energy. by bending the arms and bringing them close to the body, he is able to shorten his levers so that he can lift a much greater weight than he could possibly raise with the arms extended. on the other hand, with the extended arm he can strike a much more powerful blow than with the shorter lever of the flexed arm. but however ingenious the manipulation of the natural levers, a full utilization of muscular energy is possible only when they are supplemented with artificial aids, which constitute primitive pieces of machinery. these aids are chiefly of three types, namely, inclined planes, friction reducers, and levers. the use of the inclined plane was very early discovered and put into practise in chipped implements, which took the form of the wedge, in such modifications as axes, knives, and spears of metal. all of these implements, it will be observed, consist essentially of inclined planes, adapted for piercing relatively soft tissues of wood or flesh, and hence serving purposes of the greatest practical utility. the knife-blade is an extremely thin wedge, to be utilized by force of pushing, without any great aid from acquired momentum. the hatchet, on the other hand--and its modification the axe--has its blunter blade fastened to a handle; that the principle of the wedge may be utilized at the long end of a lever and with the momentum of a swinging blow. ages before anyone could have explained the principle involved in such obscuring terms as that, the implement itself was in use for the same purpose to which it is still applied. indeed, there is probably no other implement that has played a larger part in the history of human industry. even in the rough stone age it was in full favor, and the earliest metallurgists produced it in bronze and then in iron. the blade of to-day is made of the best tempered steel, and the handle or helve of hickory is given a slight curve that is an improvement on the straight handle formerly employed; but on the whole it may be said that the axe is a surviving primitive implement that has held its own and demonstrated its utility in every generation since the dawn, not of history only, but of barbarism, perhaps even of savagery. the saw, consisting essentially of a thin elongated blade, one ragged or toothed edge, is a scarcely less primitive and an equally useful and familiar application of the principle of the inclined plane--though it requires a moment's reflection to see the manner of application. each tooth, however minute, is an inclined plane, calculated to slide over the tissue of wood or stone or iron even, yet to tear at the tissue with its point, and, with the power of numbers, ultimately wear it away. the wheel and axle the primitive friction reducer, which continues in use to the present day unmodified in principle, is the wheel revolving on an axle. doubtless man had reached a very high state of barbarism before he invented such a wheel. the american indian, for example, knew no better method than to carry his heavy burdens on his shoulders, or drag them along the ground, with at most a pair of parallel poles or runners to modify the friction; every move representing a very wasteful expenditure of energy. but the pre-historic man of the old world had made the wonderful discovery that a wheel revolving on an axle vastly reduces the friction between a weight and the earth, and thus enables a man or a woman to convey a load that would be far beyond his or her unaided powers. it is well to use both genders in this illustration, since among primitive peoples it is usually the woman who is the bearer of burdens. and indeed to this day one may see the women of italy and germany bearing large burdens on their backs and heads, and dragging carts about the streets, quite after the primitive method. the more one considers the mechanism, the more one must marvel at the ingenuity of the pre-historic man who invented the wheel and axle. its utility is sufficiently obvious once the thing has been done. in point of fact, it so enormously reduces the friction that a man may convey ten times the burden with its aid that he can without it. but how was the primitive man, with his small knowledge of mechanics, to predict such a result? in point of fact, of course, he made no such prediction. doubtless his attention was first called to the utility of rolling bodies by a chance observation of dragging a burden along a pebbly beach, or over rolling stones. the observation of logs or round stones rolling down a hill might also have stimulated the imagination of some inventive genius. [illustration: a belgian milk-wagon. in many of the countries of europe the dog plays an important part as a beast of burden. stringent laws are enforced in these countries to prevent possible abuse or neglect of the animals.] probably logs placed beneath heavy weights, such as are still employed sometimes in moving houses, were utilized now and again for many generations before the idea of a narrow section of a log adjusted on an axis was evolved. but be that as it may, this idea was put into practise before the historic period begins, and we find the earliest civilized races of which we have record--those, namely, of old egypt and of old babylonia--in full possession of the principle of the wheel as applied to vehicles. modern mechanics have, of course, improved the mechanism as regards details, but the wheels depicted in old egyptian and babylonian inscriptions are curiously similar to the most modern types. indeed, the wheel is a striking illustration of a mechanism which continued century after century to serve the purposes of the practical worker, with seemingly no prospect of displacement. modified levers for the rest, the mechanisms which primitive man learned early to use in adding to his working efficiency, and which are still used by the hand laborer, are virtually all modifications of our familiar type-implement, the lever. a moment's reflection will show that the diversified purposes of the crowbar, hoe, shovel, hammer, drill, chisel, are all accomplished with the aid of the same principles. the crowbar, for example, enables man to regain the power which he lost when his members were adapted to locomotion. his hands, left to themselves, as we have already pointed out, give but inadequate expression to the power of his muscles. but by grasping the long end of such a lever as the crowbar, he is enabled to utilize his entire weight in addition to his muscular strength, and, with the aid of this lever, to lift many times his weight. the hoe, on the other hand, becomes virtually a lengthened arm, enabling a very slight muscular motion to be transformed into the long sweep of the implement, so that with small expenditure of energy the desired work is accomplished. similarly, the sledge and the axe lengthen out the lever of the arms, so that great momentum is readily acquired, and with the aid of inertia a relatively enormous force can be applied. it will be observed that a laborer in raising a heavy sledge brings the head of the implement near his body, thus shortening the leverage and gaining power at the expense of speed; but extends his arms to their full length as the sledge falls, having now the aid of gravitation, to gain the full advantage of the long arm of the lever in acquiring momentum. even such elaborately modified implements as the treadmill and the rowboat are operated on the principle of the lever. these also are mechanisms that have come down to us from a high antiquity. their utility, however, has been greatly decreased in modern times, by the substitution of more elaborate and economical mechanisms for accomplishing their respective purposes. the treadmill, indeed--which might be likened to an overshot waterwheel in which the human foot supplied the place of the falling water in giving power--has become obsolete, though a modification of it, to be driven by animal power, is still sometimes used, as we shall see in a moment. all these are illustrations of mechanisms with the aid of which human labor is made effective. they show the devices by which primitive man used his ingenuity in making his muscular system a more effective machine for the performance of work. but perhaps the most ingenious feat of all which our primitive ancestor accomplished was in learning to utilize the muscular energy of other animals. of course the example was always before him in the observed activity of the animals on every side. nevertheless, it was doubtless long before the idea suggested itself, and probably longer still before it was put into practise, of utilizing this almost inexhaustible natural supply of working energy. domesticated animals the first animal domesticated is believed to have been the dog, and this animal is still used, as everyone knows, as a beast of burden in the far north, and in some european cities, particularly in those of germany. subsequently the ox was domesticated, but it is probable that for a vast period of time it was used for food purposes, rather than as a beast of burden. and lastly the horse, the worker _par excellence_, was made captive by some asiatic tribes having the genius of invention, and in due course this fleetest of carriers and most efficient of draught animals was introduced into all civilized nations. doubtless for a long time the energy of the horse was utilized in an uneconomical way, through binding the burden on its back, or causing it to drag the burden along the ground. but this is inferential, since, as we have seen, the wheel was invented in pre-historic times, and at the dawn of history we find the babylonians driving harnessed horses attached to wheeled vehicles. from that day to this the method of using horse-power has not greatly changed. the vast majority of the many millions of horses that are employed every day in helping on the world's work, use their strength without gain or loss through leverage, and with only the aid of rolling friction to increase their capacity as beasts of burden. to a certain extent horse-power is still used with the aid of the modified treadmill just referred to--consisting essentially of an inclined plane of flexible mechanism made into an endless platform, which the horse causes to revolve as he goes through the movements of walking upon it. in agricultural districts this form of power is still sometimes used to run threshing machines, cider mills, wood-saws, and the like. another application of horse-power to the same ends is accomplished through harnessing a horse to a long lever like the spoke of a wheel, fastened to an axis, which is made to revolve as the horse walks about it. several horses are sometimes hitched to such a mechanism, which becomes then a wheel of several spokes. but this mechanism, which was common enough in agricultural districts two or three decades ago, has been practically superseded in recent years by the perambulatory steam engine. [illustration: two apparatuses for the utilization of animal power. the upper figure shows the type of portable horse-power machine used for threshing grain in 1851. the lower figure is an inclined-plane horse-gear. the horse stands on the sloping platform tied to the bar in front, so that it is compelled to walk as the platform recedes.] it is obvious that the amount of work which a horse can accomplish must vary greatly with the size and quality of the horse, and with the particular method by which its energy is applied. for the purposes of comparison, however, an arbitrary amount of work has been fixed upon as constituting what is called a horse-power. this amount is the equivalent of raising thirty-three thousand pounds of weight to the height of one foot in one minute. it would be hard to say just why this particular standard was fixed upon, since it certainly represents more than the average capacity of a horse. it is, however, a standard which long usage (it was first suggested by watt, of steam-engine fame) has rendered convenient, and one which the machinist refers to constantly in speaking of the efficiency of the various types of artificial machines. all questions of the exact legitimacy of this particular standard aside, it was highly appropriate that the labor of the horse, which has made up so large a share of the labor of the past, and which is still so extensively utilized, should continue to be taken as the measuring standard of the world's work. iv the work of air and water the store of energy contained in the atmosphere and in the waters of the globe is inexhaustible. its amount is beyond all calculation; or if it were vaguely calculated the figures would be quite incomprehensible from their very magnitude. it is not, however, an altogether simple matter to make this energy available for the purposes of useful work. we find that throughout antiquity comparatively little use was made of either wind or water in their application to machinery. doubtless the earliest use of air as a motive power was through the application of sails to boats. we know that the phoenicians used a simple form of sail, and no doubt their example was followed by all the maritime peoples of subsequent periods. but the use of the sail even by the phoenicians was as a comparatively unimportant accessory to the galaxies of oars, which formed the chief motive power. the elaboration of sails of various types, adequate in extent to propel large ships, and capable of being adjusted so as to take advantage of winds blowing from almost any quarter, was a development of the middle ages. the possibilities of work with the aid of running water were also but little understood by the ancients. in the days of slave labor it was scarcely worth while to tax man's ingenuity to invent machines, since so efficient a one was provided by nature. yet the properties of both air and water were studied by various mechanical philosophers, at the head of whom were archimedes, whose work has already been referred to, and the famous alexandrian, ctesibius, whose investigations became familiar through the publications of his pupil, hero. perhaps the most remarkable device invented by ctesibius was a fire-engine, consisting of an arrangement of valves constituting a pump, and operating on the principle which is still in vogue. it is known, however, that the egyptians of a much earlier period used buckets having valves in their bottoms, and these perhaps furnished the foundation for the idea of ctesibius. it is unnecessary to give details of this fire-engine. it may be noted, however, that the principle of the lever is the one employed in its operation to gain power. a valve consists essentially of any simple hinged substance, arranged so that it may rise or fall, alternately opening and closing an aperture. a mere flap of leather, nailed on one edge, serves as a tolerably effective valve. at least one of the valves used by ctesibius was a hinged piece of smooth metal. a piston fitted in a cylinder supplies suction when the lever is raised, and pressure when it is compressed, alternately opening the valve and closing the valve through which the water enters the tube. meantime a second valve alternating with the first permits the water to enter the chamber containing air, which through its elasticity and pressure equalizes the force of the stream that is ejected from the chamber through the hose. suction and pressure in the construction of this and various other apparatus, ctesibius and hero were led to make careful studies of the phenomena of suction. but in this they were not alone, since numerous of their predecessors had studied the subject, and such an apparatus as the surgeon's cupping glass was familiarly known several centuries before the christian era. the cupping glass, as perhaps should be explained to the reader of the present day--since the apparatus went out of vogue in ordinary medical practise two or three generations ago--consists of a glass cup in which the air is exhausted, so as to suck blood from any part of the surface of a body to which it is applied. hero describes a method of exhausting air by which such suction may be facilitated. but neither he nor any other philosopher of his period at all understood the real nature of this suction, notwithstanding their perfect familiarity with numerous of its phenomena. it was known, for example, that when a tube closed at one end is filled with water and inverted with the open end beneath the surface of the water, the water remains in the tube, although one might naturally expect that it would obey the impulses of gravitation and run out, leaving the tube empty. a familiar explanation of this and allied phenomena throughout antiquity was found in the saying that "nature abhors a vacuum." this explanation, which of course amounts to no explanation at all, is fairly illustrative of the method of metaphysical word-juggling that served so largely among the earlier philosophers in explanation of the mysteries of physical science. the real explanation of the phenomena of suction was not arrived at until the revival of learning in the seventeenth century. then torricelli, the pupil of galileo, demonstrated that the word suction, as commonly applied, had no proper application; and that the phenomena hitherto ascribed to it were really due to the pressure of the atmosphere. a vacuum is merely an enclosed space deprived of air, and the "abhorrence" that nature shows to such a space is due to the fact that air has weight and presses in every direction, and hence tends to invade every space to which it can gain access. it was presently discovered that if the inverted tube in which the water stands was made high enough, the water will no longer fill it, but will sink to a certain level. the height at which it will stand is about thirty feet; above that height a vacuum will be formed, which, for some reason, nature seems not to abhor. the reason is that the weight of any given column of water about thirty feet in height is just balanced by the weight of a corresponding column of atmosphere. the experiments that gave the proof of this were made by the famous englishman, boyle. he showed that if the heavy liquid, mercury, is used in place of water, then the suspended column will be only about thirty inches in height. the weight or pressure of the atmosphere at sea level, as measured by these experiments, is about fifteen pounds to the square inch. boyle's further experiments with the air and with other gases developed the fact that the pressure exerted by any given quantity of gas is proportional to the external pressure to which it is subjected, which, after all, is only a special application of the law that action and reaction are equal. the further fact was developed that under pressure a gas decreases at a fixed rate in bulk. a general law, expressing these facts in the phrase that density and elasticity vary inversely with the pressure in a precise ratio, was developed by boyle and the frenchman, mariotte, independently, and bears the name of both of its discoverers. no immediate application of the law to the practical purposes of the worker was made, however, and it is only in recent years that compressed air has been extensively employed as a motive power. even now it has not proved a great commercial success, because other more economical methods of power production are available. in particular cases, however, it has a certain utility, as a relatively large available source of energy may be condensed into a very small receptacle. a very striking experiment illustrating the pressure of the air was made by a famous contemporary of boyle and mariotte, by the name of otto von guericke. he connected an air pump with a large brass sphere, composed of two hemispheres, the edges of which fitted smoothly, but were not connected by any mechanism. under ordinary conditions the hemispheres would fall apart readily, but von guericke proved, by a famous public demonstration, that when the air was exhausted in the sphere, teams of horses pulling in opposite directions on the hemispheres could not separate them. this is famous as the experiment of the magdeburg spheres, and it is often repeated on a smaller scale in the modern physical laboratory, to the astonishment of the tyro in physical experiments. the first question that usually comes to the mind of anyone who has personally witnessed such an experiment, is the question as to how the human body can withstand the tremendous force to which it is subjected by an atmosphere exerting a pressure of fifteen pounds on every square inch of its surface. the explanation is found in the uniform distribution of the pressure, the influence of which is thus counteracted, and by the fact that the tissues themselves contain everywhere a certain amount of air at the same pressure. the familiar experiment of holding the hand over an exhausted glass cylinder--which experiment is indeed but a modification of the use of the cupping glass above referred to--illustrates very forcibly the insupportable difficulties which the human body would encounter were not its entire surface uniformly subjected to the atmospheric pressure. air in motion at about the time when the scientific experiments with the pressure of gases were being made, practical studies of the effects of masses of air in motion were undertaken by the dutch philosopher, servinus. the use of the windmill in holland as a means of generating power doubtless suggested to servinus the possibility of attaching a sail to a land vehicle. he made the experiment, and in the year 1600 constructed a sailing car which, propelled by the wind, traversed the land to a considerable distance, on one occasion conveying a company of which prince maurice of orange was a member. but his experiments have seldom been repeated, and indeed their lack of practical feasibility scarcely needs demonstration. the utility of the wind, however, in generating the power in a stationary mechanism is familiar to everyone. windmills were constructed at a comparatively early period, and notwithstanding all the recent progress in the development of steam and electrical power, this relatively primitive so-called prime mover still holds its own in agricultural districts, particularly in its application to pumps. a windmill consists of a series of inclined planes, each of which forms one of the radii of a circle, or spokes of a wheel, to the axle of which a gearing is adjusted by which the power generated is utilized. the wheel is made to face the wind by the wind itself blowing against a sort of rudder which projects from the axis. the wind blowing against the inclined surfaces or vanes of the wheel causes each vane to move in accordance with the law of component forces, thus revolving the wheel as a whole. [illustration: windmills of ancient and modern types. the smaller figures show dutch windmills of the present day, many of which are identical in structure with the windmills of the middle ages. it will be seen that the sails can be furled when desired to put the mill out of operation. in the mill of modern type (large figure) the same effect is produced by slanting the slats of the wheel.] it has been affirmed that the romans had windmills, but "the silence of vitruvius, seneca, and chrysostom, who have spoken of the advantages of the wind, makes this opinion questionable." it has been supposed by other writers that windmills were used in france in the sixth century, while still others have maintained that this mechanism was unknown in europe until the time of the crusades. all that is tolerably certain is that in the twelfth century windmills were in use in france and england. it is recorded that when they began to be somewhat common pope celestine iii. determined that the tithes of them belonged to the clergy. inherent defects of the windmill the mediæval european windmill was supplied with great sails of cloth, and its picturesque appearance has been made familiar to everyone through the famous tale of _don quixote_. the modern windmill, acting on precisely the same principle, is a comparatively small affair, comprising many vanes of metal, and constituting a far more practical machine. the great defect of all windmills, however, is found in the fact that of necessity they furnish such variable power, since the force of the wind is incessantly changing. worst of all, there may be protracted periods of atmospheric calm, during which, of course, the windmill ceases to have any utility whatever. this ineradicable defect relegates the windmill to a subordinate place among prime movers, yet on the other hand, its cheapness insures its employment for a long time to come, and the industry of manufacturing windmills continues to be an important one, particularly in the united states. running water the aggregate amount of work accomplished with the aid of the wind is but trifling, compared with that which is accomplished with the aid of water. the supply of water is practically inexhaustible, and this fluid being much more manageable than air, can be made a far more dependable aid to the worker. every stream, whatever its rate of flow, represents an enormous store of potential energy. a cubic foot of water weighs about sixty-two and a half pounds. the working capacity of any mass of water is represented by one-half its weight into the square of its velocity; or, stated otherwise, by its weight into the distance of its fall. now, since the interiors of the continents, where rivers find their sources, are often elevated by some hundreds or even thousands of feet, it follows that the working energy expended--and for the most part wasted--by the aggregate water current of the world is beyond all calculation. meantime, however, a portion of the energy which in the aggregate represents an enormous working power is utilized with the aid of various types of water wheels. watermills appear to have been introduced in the time of mithridates, julius cæsar, and cicero. strabo informs us that there was a watermill near the residence of mithridates; and we learn from pomponius sabinus, that the first mill seen at rome was erected on the tiber, a little before the time of augustus. that they existed in the time of augustus is obvious from the description given of them by vitruvius, and the epigram of antipater, who is supposed to have lived in the time of cicero. but though mills driven by water were introduced at this early period, yet public mills did not appear till the time of honorius and arcadius. they were erected on three canals, which conveyed water to the city, and the greater number of them lay under mount janiculum. when the goths besieged rome in 536, and stopped the large aqueduct and consequently the mills, belisarius appears to have constructed, for the first time, floating mills upon the tiber. mills driven by the tide existed at venice in the year 1046, or at least in 1078. the older types of water wheel are exceedingly simple in construction, consisting merely of vertical wheels revolving on horizontal axes, and so placed as to receive the weight or pressure of the water on paddles or buckets at their circumference. the water might be allowed to rush under the wheel, thus constituting an under-shot wheel; or more commonly it flows from above, constituting an over-shot wheel. where the natural fall is not available, dams are employed to supply an artificial fall. this primitive type of water wheel has been practically abandoned within the last generation, its place having been taken by the much more efficient type of wheel known as the turbine. this consists of a wheel, usually adjusted on a vertical axis, and acting on what is virtually the principle of a windmill. to gain a mental picture of the turbine in its simplest form, one might imagine the propelling screw of a steamship, placed horizontally in a tube, so that the water could rush against its blades. the tiny windmills which children often make by twisting pieces of paper illustrate the same principle. of course, in its developed form the turbine is somewhat elaborated, in the aim to utilize as large a proportion of the energy of the falling water as is possible; but the principle remains the same. the turbine wheel was invented by a frenchman named fourneyron, about three-quarters of a century ago (1827), but its great popularity, in america in particular, is a matter of the last twenty or thirty years. to-day it has virtually supplanted every other type of water wheel. to use any other is indeed a wasteful extravagance, as the perfected turbine makes available more than eighty per cent. of the kinetic energy of any mass of falling water. a turbine wheel two feet in diameter is able to do the work of an enormous wheel of the old type. turbine wheels are of several types, one operating in a closed tube to which air has no access, and another in an open space in the presence of air. the water may also be made to enter the turbine at the side or from below, thus serving to support the weight of the mechanism--a consideration of great importance in the case of such gigantic turbines as those that are employed at niagara falls, which we shall have occasion to examine in detail in a later chapter. [illustration: water wheels. fig. 1 shows a model of the so-called breast wheel, a familiar type of water wheel that has been in use since the time of the romans. figs. 2 and 3 show similar wheels as used to-day in belgium. fig. 4 shows a model of fourneyron's turbine. this wheel was made in 1837, but the original turbine was introduced by fourneyron in 1827. the turbine wheel has now almost supplanted the other forms of water wheel except in rural districts.] the power generated by a revolution of the turbine wheel may, of course, be utilized directly by belts or gearings attached to its axle, or it may be transferred to a distance, with the aid of a dynamo generating electricity. the latter possibility, which has only recently been developed, and which we shall have occasion to examine in detail in connection with our studies of the power at niagara, gives a new field of usefulness to the turbine wheel, and makes it probable that this form of power will be vastly more used in the future than it has been in the past. indeed, it would not be surprising were it ultimately to become the prime source of working energy as utilized in every department of the world's work. mr. edward h. sanborn, in an article on motive power appliances in the twelfth census report of the united states, comments upon the recent advances in the use of water wheels as follows: "one notable advance in turbine construction has been the production of a type of wheel especially designed for operating under much higher heads of water than were formerly considered feasible for wheels of this type. turbines are now built for heads ranging from 100 to 1,200 feet, and quite a number of wheels are in operation under heads of from 100 to 200 feet. this is an encroachment upon the field occupied almost exclusively by wheels variously known as the 'impulse,' 'impact,' 'tangential,' or 'jet' type, the principle of which is the impact of a powerful jet of water from a small nozzle upon a series of buckets mounted upon the periphery of a small wheel." "the impact water wheel," mr. sanborn continues, "has come largely into use during the last ten years, principally in the far west, where higher heads of water are available than can be found in other parts of the country. with wheels of this type, exceedingly simple in construction and of comparatively small cost, a large amount of power is developed with great economy under the great heads that are available. with the tremendous water pressure developed by heads of 1,000 feet and upward, which in many cases are used for this purpose, wheels of small diameter develop an extraordinary amount of power. to the original type of impact wheel which first led the field have been added several styles embodying practically the same principle. considerable study has been given to the designing of buckets with a view to securing free discharge and the avoidance of any disturbing eddies, and important improvements have resulted from the thorough investigation of the action of the water during, and subsequent to, its impact on the buckets. the impact wheel has been adapted to a wide range of service with great variation as to the conditions under which it operates, wheels having been made in california from 30 inches to 30 feet in diameter, and to work under heads ranging from 35 to 2,100 feet, and at speeds ranging from 65 to 1,100 revolutions per minute. a number of wheels of this type have been built with capacities of not less than 1,000 horse-power each." hydraulic power a few words should be said about the familiar method of transmitting power with the aid of water, as illustrated by the hydrostatic press. this does not indeed utilize the energy of the water itself, but it enables the worker to transmit energy supplied from without, and to gain an indefinite power to move weights through a short distance, with the expenditure of very little working energy. the principle on which the hydrostatic press is based is the one which was familiar to the ancient philosophers under the name of the hydrostatic paradox. it was observed that if a tube is connected with a closed receptacle, such as a strong cask, and cask and tube are filled with water, the cask will presently be burst by the pressure of the water, provided the tube is raised to a height, even though the actual weight of water in the tube be comparatively slight. a powerful cask, for example, may be burst by the water poured into a slender pipe. the result seems indeed paradoxical, and for a long time no explanation of it was forthcoming. it remained for servinus, whose horseless wagon is elsewhere noticed, to discover that the water at any given level presses equally in all directions, and that its pressure is proportionate to its depth, quite regardless of its bulk. then, supposing the tube in our experiment to have a cross-section of one square inch, a pressure equal to that in the tube would be transmitted to each square inch of the surface of the cask; and the pressure might thus become enormous. if, instead of a tube lifted to a height, the same tube is connected with a force pump operated with a lever--an apparatus similar to the fire-engine of ctesibius--it is obvious that precisely the same effect may be produced; whatever pressure is developed in the piston of the force pump, similar pressure will be transferred to a corresponding area in the surface of the cask or receptacle with which the force pump connects. in practise this principle is utilized, where great pressure is desired, by making a receptacle with an enormous piston connecting with the force pump just described. an indefinite power may thus be developed, the apparatus constituting virtually a gigantic lever. but the principle of the equivalence of weight and distance still holds, precisely as in an actual lever, and while the pressure that may be exerted with slight expenditure of energy is enormous, the distance through which this pressure acts is correspondingly small. if, for example, the piston of the force pump has an area of one square inch, while the piston of the press has an area of several square feet, the pressure exerted will be measured in tons, but the distance through which it is exerted will be almost infinitesimal. the range of utility of the hydrostatic press is, therefore, limited, but within its sphere, it is an incomparable transmitter of energy. [illustration: hydraulic press and hydraulic capstan. the upper figure shows bramah's original hydraulic pump and press, now preserved in the south kensington museum, london. the machine was constructed in 1796 by joseph bramah to demonstrate the principle of his hydraulic press. the discrepancy in size between the small lever worked by hand and the enormous lever carrying a heavy weight gives a vivid impression of the gain in power through the use of the apparatus. the lower figure shows the hydraulic capstan used on many modern ships, in which the same principle is utilized.] moreover, it is possible to reverse the action of the hydraulic apparatus so as to gain motion at the expense of power. a familiar type of elevator is a case in point. the essential feature of the hydraulic elevator consists of a ram attached to the bottom of the elevator and extending down into a cylinder, slightly longer than the height to which the elevator is to rise. the ram is fitting into a cylinder with water-tight packing, or a cut leather valve. water under high pressure is admitted to the cylinder through the valve at the bottom, and the pressure thus supplied pushes up the ram, carrying the elevator with it, of course. another valve allows the water to escape, so that ram and elevator may descend, too rapid descent being prevented by the partial balancing of ram and elevator with weights acting over pulleys. the ram, to the end of which pressure is thus applied, need be but a few inches in diameter. water pressure is secured by bringing water from an elevation. such an elevator acts slowly, but is a very safe and in many ways satisfactory mechanism. such elevators are still used extensively in europe, but have been almost altogether displaced in america by the electric elevator. the hydraulic elevator just described is virtually a water engine, the ram acting as piston. a veritable engine, of small size, to perform any species of mechanical work, may be constructed on precisely the same principle, the piston in this case acting in a cylinder similar to that of the ordinary steam engine. such an engine operates slowly but with great power. it has special utility where it is desirable to apply power intermittently, as in various parts of a dockyard, or in handling guns and ammunition on shipboard. in the former case in particular, it is often inconvenient to use steam power, as steam sent from a central boiler condenses in a way to interfere with its operation. in such a case any number of small water-pressure engines may be operated from a single tank where water is at a high elevation, or where the requisite pressure is secured artificially. in the latter case, the water is kept under pressure by a large piston or ram heavily weighted, the entire receptacle being, of course, of water-tight construction and adapted to withstand pressure. the pump that supplies the tank is ordinarily made to work automatically, ceasing operation as soon as the ram rises to the top of the receptacle, and beginning again whenever, through use of water, the ram begins to descend. such an apparatus is called an accumulator. such water engines have come into vogue only in comparatively recent times, being suggested by the steam engine. as already pointed out, their utility is restricted, yet the total number of them in actual use to-day is large, and their share in the world's work is not altogether inconsiderable. v captive molecules: the story of the steam engine we come now to that all-important transformer of power, the steam engine. everybody knows that steam is a state of water in which, under the influence of heat, the molecules have broken away from the mutual attraction of cohesion, and are flying about at inconceivable speed, rebounding from one another after collision, in virtue of their elasticity, exerting in the aggregate an enormous pressure in every direction. it is this consideration of the intimate character of steam that justifies the title of the present chapter; a title that has further utility as drawing a contrast between the manner of working with which we are now to be concerned, and the various types of workers that we have previously considered. in speaking of the animal machine and of work accomplished by the air and the water, we have been concerned primarily with masses of matter, possessing and transmitting energy. of course molecules--since they make up the substance of all matter--could not be altogether ignored, but in the main we have had to do with molar rather than with molecular motion. now, however, we are concerned with a mechanism in which the molecular activities are directly concerned in performing work. even in the aggregate the molecules make up a mere intangible gas, which requires to be closely confined in order that its energy may be made available. once the molecules have performed their work, they are so changed in their activities that they sink back, as it were, exhausted, into a relatively quiescent state, which enables their latent cohesive forces to reduce them again to the state of a liquid. in a word, we are concerned with the manifestation of energy which depends upon molecular activities in a way quite different from what has been the case with any of the previously considered mechanisms. the tangible manifestation of energy which we term heat is not merely a condition of action and a by-product, as it was in the case of the animal machine; it is the essential factor upon which all the efficiency of the mechanism depends. it should perhaps be stated that this explanation of the action of the steam engine is a comparatively modern scientific interpretation. the earlier experimenters brought the steam engine to a high state of efficiency, without having any such conception as this of the nature of steam itself. for practical purposes it suffices to note that water when heated takes the form of steam; that this steam has the property of powerful and indefinite expansion; and thirdly, that when allowed to escape from a state of pressure, sudden expansion of the steam cools it sufficiently to cause the recondensation of part of its substance, thus creating a vacuum. stated in few words, the entire action of the steam depends upon these simple mechanical principles. the principles are practically applied by permitting the steam to enter the cylinder where it can act on a piston, to which it gives the thrust that is transmitted to an external mechanism by means of a rod attached to the piston. when the piston has been driven to the end of the desired thrust, the valve is opened automatically, permitting the steam to escape, thus producing a vacuum, and insuring the return thrust of the piston, which is further facilitated, ordinarily, by the admission of steam to the other side of the piston. practical operation of this mechanism is familiar to everyone, though the marvel of its power and efficiency seems none the less because of its familiarity. it is not too much to say that this relatively simple device, in its first general application, marked one of the most important turning points in the history of civilization. to its influence, more than to any other single cause, must be ascribed the revolutionary change that came over the character of practical life in the nineteenth century. from prehistoric times till well toward the close of the eighteenth century, there was scarcely any important change in carrying out the world's work. and in the few generations that have since elapsed, the entire aspect of the mechanical world has been changed, the working efficiency of the individual has been largely increased; mechanical tasks have become easy which hitherto were scarcely within the range of human capacity. before we go on to the detailed study of the machine which has produced these remarkable results, it is desirable to make inquiry as to the historical development of so important an invention. the practical steam engine in its modern form dates, as just mentioned, from the latter part of the eighteenth century, and was perfected by james watt, who is commonly thought of as being its inventor. in point of fact, however, the history of most inventions is duplicated here, as on examination it appears that various forerunners of watt had been on the track of the steam engine, and some of them, indeed, had produced a workable machine of no small degree of efficiency. the very earliest experiments were made away back in the alexandrian days in the second century before the christian era, the experimenter being the famous hero, whose work in an allied field was referred to in the preceding chapter. hero produced--or at least described and so is credited with producing, though the actual inventor may have been ctesibius--a little toy mechanism, in which a hollow ball was made to revolve on an axis through the agency of steam, which escaped from two bent tubes placed on opposite sides of the ball, their orifices pointing in opposite directions. the apparatus had no practical utility, but it sufficed to establish the principle that heat, acting through the agency of steam, could be made to do mechanical work. had not the age of hero been a time of mental stasis, it is highly probable that the principle he had thus demonstrated would have been applied to some more practical mechanism in succeeding generations. as it was, however, nothing practical came of his experiment, and the steam turbine engine was remembered only as a scientific toy. no other worker continued the experiments, so far as is known, until the time of the great italian, leonardo da vinci, who, late in the fifteenth century, gave a new impulse to mechanical invention. leonardo experimented with steam, and succeeded in producing what was virtually an explosion engine, by the agency of which a ball was propelled along the earth. but this experiment also failed to have practical result. beginnings of modern discovery such sporadic experiments as these have no sequential connection with the story of the evolution of the steam engine. the experiments which led directly on to practical achievements were not begun until the seventeenth century. in the very first year of that century, an italian named giovanni battista della porta published a treatise on pneumatics, in which the idea of utilizing steam for the practical purpose of raising water was expressly stated. the idea of this inventor was put into effect in 1624 by a french engineer and mathematician, solomon de caus. he invented two different machines, the first of which required a spherical boiler having an internal tube reaching nearly to the bottom; a fire beneath the boiler produced steam which would force the water in the boiler to a height proportional to the pressure obtained. in the other machine, steam is led from the boiler into the upper part of a closed cistern containing water to be elevated. to the lower portion of the cistern a delivery pipe was attached so that water was discharged under a considerable pressure. this arrangement was precisely similar to the apparatus employed by hero of alexandria in various of his fountains, as regards the principle of expanding gas to propel water. an important difference, however, consists in the fact that the scheme of della porta and of de caus embodied the idea of generating pressure with the aid of steam, whereas hero had depended merely on the expansive property of air compressed by the water itself. while these mechanisms contained the germ of an idea of vast importance, the mechanisms themselves were of trivial utility. it is not even clear whether their projectors had an idea of the properties of the condensation of vapor, upon which the working of the practical steam engine so largely depends. this idea, however, was probably grasped about half a century later by an englishman, edward somerset, the celebrated marquis of worcester, who in 1663 described in his _century of inventions_ an apparatus for raising water by the expansive force of steam. his own account of his invention is as follows: "an admirable and most forcible way to drive up water by fire; not by drawing or sucking it upwards, for that must be as the philosopher calleth it, _intra sphæram activitatis_, which is but at such a distance. but this way hath no bounder, if the vessel be strong enough: for i have taken a piece of whole cannon, whereof the end was burst, and filled it three-quarters full of water, stopping and screwing up the broken end, as also the touch-hole; and making a constant fire under it, within twenty-four hours it burst and made a great crack; so that having a way to make my vessels so that they are strengthened by the force within them, and the one to fill after the other, i have seen the water run like a constant stream, forty feet high: one vessel of water, rarefied by fire, driveth up forty of cold water; and the man that tends the work is but to turn two cocks, that one vessel of water being consumed, another begins to force and refill with cold water, and so successively; the fire being tended and kept constant, which the self-same person may likewise abundantly perform in the interim, between the necessity of turning the said cocks." it is unfortunate that the marquis did not give a more elaborate description of this remarkable contrivance. the fact that he treats it so casually is sufficient evidence that he had no conception of the possibilities of the mechanism; but, on the other hand, his description suffices to prove that he had gained a clear notion of, and had experimentally demonstrated, the tremendous power of expansion that resides in steam. no example of his steam pump has been preserved, and historians of the subject have been left in doubt as to some details of its construction, and in particular as to whether it utilized the principle of a vacuum created through condensation of the steam. thomas savery's steam pump this principle was clearly grasped, however, by another englishman, thomas savery, a cornish mine captain, who in 1698 secured a patent for a steam engine to be applied to the raising of water, etc. a working model of this machine was produced before the royal society in 1699. the transactions of the society contain the following: "june 14th, 1699, mr. savery entertained the royal society with showing a small model of his engine for raising water by help of fire, which he set to work before them: the experiment succeeded according to expectation, and to their satisfaction." the following very clear description of savery's engine is given in the introduction to beckmann's _history of inventions_: "this engine, which was used for some time to a considerable extent for raising water from mines, consisted of a strong iron vessel shaped like an egg, with a tube or pipe at the bottom, which descended to the place from which the water was to be drawn, and another at the top, which ascended to the place to which it was to be elevated. this oval vessel was filled with steam supplied from a boiler, by which the atmospheric air was first blown out of it. when the air was thus expelled and nothing but pure steam left in the vessel, the communication with the boiler was cut off, and cold water poured on the external surface. the steam within was thus condensed and a vacuum produced, and the water drawn up from below in the usual way by suction. the oval vessel was thus filled with water; a cock placed at the bottom of the lower pipe was then closed, and steam was introduced from the boiler into the oval vessel above the surface of the water. this steam being of high pressure, forced the water up the ascending tube, from the top of which it was discharged, and the oval vessel being thus refilled with steam, the vacuum was again produced by condensation, and the same process was repeated. by using two oval steam vessels, which would act alternately--one drawing water from below, while the other was forcing it upwards, an uninterrupted discharge of water was produced. owing to the danger of explosion, from the high pressure of the steam which was used, and from the enormous waste of heat by unnecessary condensation, these engines soon fell into disuse." [illustration: thomas savery's steam engine. the principle involved is that of the expansion of steam exerting a propulsive force and its subsequent condensation to produce a vacuum. these are the principles employed in the modern steam engine, but the only use to which they were put in savery's engine was the elevation of water by suction.] this description makes it obvious that savery had the clearest conception of the production of a vacuum by the condensation of steam, and of the utilization of the suction thus established (which suction, as we know, is really due to the pressure of outside air) to accomplish useful work. savery also arranged this apparatus in duplicate, so that one vessel was filling with water while the other was forcing water to the delivery pipe. this is credited with being the first useful apparatus for raising water by the combustion of fuel. there was a great waste of steam, through imparting heat to the water, but the feasibility of the all-important principle of accomplishing mechanical labor with the aid of heat was at last demonstrated. as yet, however, the experimenters were not on the track of the method by which power could be advantageously transferred to outside machinery. an effort in quite another direction to accomplish this had been made as early as 1629 by giovanni branca, an italian mathematician, who had proposed to obtain rotary motion by allowing a jet of steam to blow against the vanes of a fan wheel, capable of turning on an axis. in other words, he endeavored to utilize the principle of the windmill, the steam taking the place of moving air. the idea is of course perfectly feasible, being indeed virtually that which is employed in the modern steam turbine; but to put the idea into practise requires special detailed arrangements of steam jet and vanes, which it is not strange the early inventor failed to discover. his experiments appear not to have been followed up by any immediate successor, and nothing practical came of them, nor was the principle which he had attempted to utilize made available until long after a form of steam engine utilizing another principle for the transmission of power had been perfected. denis papin invents the piston engine the principle in question was that of causing expanding steam to press against a piston working tightly in a cylinder, a principle, in short, with which everyone is familiar nowadays through its utilization in the ordinary steam engine. the idea of making use of such a piston appears to have originated with a frenchman, denis papin, a scientific worker, who, being banished from his own country, was established as professor of mathematics at the university of marburg. he conceived the important idea of transmitting power by means of a piston as early as 1688, and about two years later added the idea of producing a vacuum in a cylinder, by cooling the cylinder,--the latter idea being, as we have just seen, the one which savery put into effect. [illustration: diagrams of early attempts to utilize the power of steam. giovanni branca 1629 guillaume amontons 1699 two attempts to give rotation to a mechanical apparatus through the action of heated air or steam. nothing practical came of either effort, but the mechanisms depicted are of historical interest.] it will be noted that papin's invention antedated that of savery; to the frenchman, therefore, must be given the credit of hitting upon two important principles which made feasible the modern steam engine. papin constructed a model consisting of a small cylinder in which a solid piston worked. in the cylinder beneath the piston was placed a small quantity of water, which, when the cylinder was heated, was turned into steam, the elastic force of which raised the piston. the cylinder was then cooled by removing the fire, when the steam condensed, thus creating a vacuum in the cylinder, into which the piston was forced by the pressure of the atmosphere. such an apparatus seems crude enough, yet it incorporates the essential principles, and required but the use of ingenuity in elaborating details of the mechanism, to make a really efficient steam engine. it would appear, however, that papin was chiefly interested in the theoretical, rather than in the really practical side of the question, and there is no evidence of his having produced a working machine of practical power, until after such machines worked by steam had been constructed elsewhere. thomas newcomen's improved engine as has happened so often in other fields, englishmen were the first to make practical use of the new ideas. in 1705 thomas newcomen, a blacksmith or ironmonger, and john cawley, a plumber and glazier, patented their atmospheric engine, and five years later, in the year 1710, namely, newcomen had on the market an engine which is described in the _report of the department of science and arts of the south kensington museum_, as "the first real pumping engine ever made." the same report describes the engine as "a vertical steam cylinder provided with a piston connected at one end of the beam, having a pivot or bearing in the middle of its length, and at the other end of the beam pump rods for working the pump. the cylinder was surrounded by a second cylinder or jacket, open at the top, and cold water could be supplied to this outer cylinder at pleasure. the single or working cylinder could be supplied with steam when desired from a boiler below it. there was a drain pipe from the bottom of the working cylinder, and one from the outer cylinder. for the working of the engine steam was admitted to the working cylinder, so as to fill it and expel all the air, the piston then being at the top, owing to the weight of the pump rods being sufficient to lift it; then the steam was shut off and the drain cocks closed and cold water admitted to the outer cylinder, so that the steam in the working cylinder condensed, and, leaving a partial vacuum of pressure of the atmosphere, forced the piston down and drew up the pump rods, thus making a stroke of the pump. then the water was drawn off from the outer cylinder and steam admitted to the working cylinder before allowing the piston to return to the top of its stroke, ready for the next down stroke." it will be observed that this machine adopts the principle, with only a change of mechanical details, of the papin engine just described. a later improvement made by newcomen did away with the outer cylinder for condensing the steam, employing instead an injection of cold water into the working cylinder itself, thus enabling the engine to work more quickly. it is said that the superiority of the internal condensing arrangement was accidentally discovered through the improved working of an engine that chanced to have an exceptionally leaky piston or cylinder. many engines were made on this plan and put into practical use. another important improvement was made by a connection from the beam to the cocks or valves, so that the engine worked automatically, whereas in the first place it had been necessary to have a boy or man operate the valves,--a most awkward arrangement, in the light of modern improvements. as the story is told, the duty of opening and closing the regulating and condensing valves was intrusted to boys called cock boys. it is said that one of these boys named humphrey potter "wishing to join his comrades at play without exposing himself to the consequences of suspending the performance of the engine, contrived, by attaching strings of proper length to the levers which governed the two cocks, to connect them with the beam, so that it should open and close the cocks as it moved up and down with the most perfect regularity." this story has passed current for almost two centuries, and it has been used to point many a useful moral. it seems almost a pity to disturb so interesting a tradition, yet it must have occurred to more than one iconoclast that the tale is almost too good to be true. and somewhat recently it has been more than hinted that desaguliers, with whom the story originated, drew upon his imagination for it. a print is in existence, made so long ago as 1719, representing an engine erected by newcomen at dudley castle, staffordshire, in 1712, in which an automatic valve gear is clearly shown, proving that the newcomen engine was worked automatically at this early period. that the admirable story of the inventive youth, whose wits gave him leisure for play, may not be altogether discredited, however, it should be added that unquestionably some of the early engines had a hand-moved gear, and that at least one such was still working in england after the middle of the nineteenth century. it seems probable, then, that the very first engines were without the automatic valve gear, and there is no inherent reason why a quick-witted youth may not have been the first to discover and remedy the defect. according to the report of the department of science and arts of the south kensington museum: "the adoption of newcomen's engine was rapid, for, commencing in 1711 with the engine at wolverhampton, of twenty-three inch diameter and six foot stroke, they were in common use in english collieries in 1725; and smeaton found in 1767 that, in the neighborhood of newcastle alone there were fifty-seven at work, ranging in size from twenty-eight inch to seventy-five inch cylinder diameter, and giving collectively about twelve hundred horse-power. as newcomen obtained an evaporation of nearly eight pounds of water per pound of coal, the increase of boiler efficiency since his time has necessarily been but slight, although in other requisites of the steam generator great improvements are noticeable." [illustration: a model of the newcomen engine. this engine has particular interest not only because it was a practical pumping engine, but also because it was while repairing an engine of this type that watt was led to the experiments that resulted in his epoch-making discovery.] the coming of james watt the newcomen engine had low working efficiency as compared with the modern engine; nevertheless, some of these engines are still used in a few collieries where waste coal is available, the pressure enabling the steam to be generated in boilers unsafe for other purposes. the great importance of the newcomen engine, however, is historical; for it was while engaged in repairing a model of one of these engines that james watt was led to invent his plan of condensing the steam, not in the working cylinder itself, but in a separate vessel,--the principle upon which such vast improvements in the steam engine were to depend. it is impossible to overestimate the importance of the work which watt accomplished in developing the steam engine. fully to appreciate it, we must understand that up to this time the steam engine had a very limited sphere of usefulness. the newcomen engine represented the most developed form, as we have seen; and this, like the others that it had so largely superseded, was employed solely for the pumping of water. in the main, its use was confined to mines, which were often rendered unworkable because of flooding. we have already seen that a considerable number of engines were in use, yet their power in the aggregate added but a trifle to man's working efficiency, and the work that they did accomplish was done in a most uneconomical manner. indeed the amount of fuel required was so great as to prohibit their use in many mines, which would have been valuable could a cheaper means have been found of freeing them from water. watt's inventions, as we shall see, accomplished this end, as well as various others that were not anticipated. it was through consideration of the wasteful manner of action of the steam engine that watt was led to give attention to the subject. the great inventor was a young man at the university of glasgow. he had previously served an apprenticeship of one year with a maker of philosophical instruments in london, but ill health had prevented him from finishing his apprenticeship, and he had therefore been prohibited from practising his would-be profession in glasgow. finally, however, he had been permitted to work under the auspices of the university; and in due course, as a part of his official duties, he was engaged in repairing a model of the newcomen engine. this incident is usually mentioned as having determined the line of watt's future activity. it should be recalled, however, that watt had become a personal friend of the celebrated professor black, the discoverer of latent heat, and the foremost authority in the world, in this period, on the study of pneumatics. just what share black had in developing watt's idea, or in directing his studies toward the expansive properties of steam, it would perhaps be difficult to say. it is known, however, that the subject was often under discussion; and the interest evinced in it by black is shown by the fact that he subsequently wrote a history of watt's inventions. it is never possible, perhaps, for even the inventor himself to re-live the history of the growth of an idea in his own mind. much less is it possible for him to say precisely what share of his progress has been due to chance suggestions of others. but it is interesting, at least, to recall this association of watt with the greatest experimenter of his age in a closely allied field. questions of suggestion aside, it illustrates the technical quality of watt's mind, making it obvious that he was no mere ingenious mechanic, who stumbled upon his invention. he was, in point of fact, a carefully trained scientific experimenter, fully equipped with all the special knowledge of his time in its application to the particular branch of pneumatics to which he gave attention. the first and most obvious defect in the newcomen engine was, as watt discovered, that the alternating cooling and heating of the cylinder resulted in an unavoidable waste of energy. the apparatus worked, it will be recalled, by the introduction of steam into a vertical cylinder beneath the piston, the cylinder being open above the piston to admit the air. the piston rod connected with a beam suspended in the middle, which operated the pump, and which was weighted at one end in order to facilitate the raising of the piston. the steam, introduced under low pressure, scarcely more than counteracted the pressure of the air, the raising of the piston being largely accomplished by the weight in question. of course the introduction of the steam heated the cylinder. in order to condense the steam and produce a vacuum, water was injected, the cylinder being thereby cooled. a vacuum being thus produced beneath the cylinder, the pressure of the air from above thrust the cylinder down, this being the actual working agent. it was for this reason that the newcomen engine was called, with much propriety, a pneumatic engine. the action of the engine was very slow, and it was necessary to employ a very large piston in order to gain a considerable power. the first idea that occurred to watt in connection with the probable improvement of this mechanism did not look to the alteration of any of the general features of the structure, as regards size or arrangement of cylinder, piston, or beam, or the essential principle upon which the engine worked. his entire attention was fixed on the discovery of a method by which the loss of heat through periodical cooling of the cylinder could be avoided. we are told that he contemplated the subject long, and experimented much, before he reached a satisfactory solution. naturally enough his attention was first directed toward the cylinder itself. he queried whether the cylinder might not be made of wood, which, through its poor conduction of heat, might better equalize the temperature. experiments in this direction, however, produced no satisfactory result. [illustration: watt's earliest type of pumping engine. the lower figure shows the ruins of watt's famous engine "old bess." the upper figure shows a reconstructed model of the "old bess" engine. it will be noted that the walking beam is precisely of the newcomen type. in fact, the entire engine is obviously only a modification of the newcomen engine. it had, however, certain highly important improvements, as described in the text.] then at last an inspiration came to him. why not connect the cylinder with another receptacle, in which the condensation of the steam could be effected? the idea was a brilliant one, but neither its originator nor any other man of the period could possibly have realized its vast and all-comprehending importance. for in that idea was contained the germ of all the future of steam as a motive power. indeed, it scarcely suffices to speak of it as the germ merely; the thing itself was there, requiring only the elaboration of details to bring it to perfection. watt immediately set to work to put his brilliant conception of the separate condenser to the test of experiment. he connected the cylinder of a newcomen engine with a receptacle into which the steam could be discharged after doing its work on the piston. the receptacle was kept constantly cooled by a jet of water, this water and the water of condensation, together with any air or uncondensed steam that might remain in the receptacle, being constantly removed with the aid of an air pump. the apparatus at once demonstrated its practical efficiency,--and the modern steam engine had come into existence. it was in the year 1765, when watt was twenty-nine years old, that he made his first revolutionary experiment, but his first patents were not taken out until 1769, by which time his engine had attained a relatively high degree of perfection. in furthering his idea of keeping the cylinder at an even temperature, he had provided a covering for it, which might consist of wood or other poorly conducting material, or a so-called jacket of steam--that is to say, a portion of steam admitted into the closed chamber surrounding the cylinder. moreover, the cylinder had been closed at the top, and a portion of steam admitted above the piston, to take the place of the atmosphere in producing the down stroke. this steam above the piston, it should be explained, did not connect with the condensing receptacle, so the engine was still single-acting; that is to say it performed work only during one stroke of the piston. a description of the mechanism at this stage of its development may best be given in the words of the inventor himself, as contained in his specifications in the application for patent on his improvements in 1769. "my method of lessening the consumption of steam, and consequently fuel, in fire-engines, consists of the following principles: "first, that vessel in which the powers of steam are to be employed to work the engine, which is called the cylinder in common fire-engines, and which i call the steam vessel, must, during the whole time the engine is at work, be kept as hot as the steam that enters it; first by enclosing it in a case of wood, or any other materials that transmit heat slowly; secondly, by surrounding it with steam or other heated bodies; and, thirdly, by suffering neither water nor any other substance colder than the steam to enter or touch it during that time. "secondly, in engines that are to be worked wholly or partially by condensation of steam, the steam is to be condensed in vessels distinct from the steam vessels or cylinders, although occasionally communicating with them; these vessels i call condensers; and, whilst the engines are working, these condensers ought at least to be kept as cold as the air in the neighborhood of the engines, by application of water or other cold bodies. "thirdly, whatever air or other elastic vapor is not condensed by the cold of the condenser, and may impede the working of the engine, is to be drawn out of the steam vessels or condensers by means of pumps, wrought by the engines themselves, or otherwise. "fourthly, i intend in many cases to employ the expansive force of steam to press on the pistons, or whatever may be used instead of them, in the same manner in which the pressure of the atmosphere is now employed in common fire-engines. in cases where cold water can not be had in plenty, the engines may be wrought by this force of steam only, by discharging the steam into the air after it has done its office. "sixthly, i intend in some cases to apply a degree of cold not capable of reducing the steam to water, but of contracting it considerably, so that the engines shall be worked by the alternate expansion and contraction of the steam. "lastly, instead of using water to render the pistons and other parts of the engine air-and steam-tight, i employ oils, wax, resinous bodies, fat of animals, quicksilver and other metals in their fluid state." rotary motion it must be understood that watt's engine was at first used exclusively as an apparatus for pumping. for some time there was no practical attempt to apply the mechanism to any other purpose. that it might be so applied, however, was soon manifest, in consideration of the relative speed with which the piston now acted. it was not until 1781, however, that watt's second patent was taken out, in which devices are described calculated to convert the reciprocating motion of the piston into motion of rotation, in order that the engine might drive ordinary machinery. it seems to be conceded that watt was himself the originator of the idea of making the application through the medium of a crank and fly-wheel such as are now universally employed. but the year before watt took out his second patent, another inventor named james picard had patented this device of crank and connecting rod, having, it is alleged, obtained the idea from a workman in watt's employ. whatever be the truth as to this point, picard's patent made it necessary for watt to find some alternative device, and after experimenting, he hit upon the so-called sun and planet gearing, and henceforth this was used on his rotary engines until the time for the expiration of picard's patent, after which the simpler and more satisfactory crank and fly-wheel were adopted. in the meantime, watt had associated himself with a business partner named boulton, under the firm name of boulton and watt. in 1776 a special act of legislation extending the term of watt's original patent for a period of twenty-five years had been secured. all infringements were vigorously prosecuted, and the inventor, it is gratifying to reflect, shared fully in the monetary proceeds that accrued from his invention. [illustration: watt's rotative engine. the lower figure shows the earliest type of mechanism through which watt applied his engine to other uses than that of pumping. the so-called sun-and-planet gearing, through which rotary motion was attained, is seen at the lower right-hand corner of the figure. the upper figure shows a later and much improved type of the watt engine, in which the sun-and-planet gearing has been supplanted by a simple crank.] notwithstanding the early recognition of the possibility of securing rotary motion with watt's perfected newcomen engine, it was long before the full possibilities of the application of this principle were realized, even by the most practical of machinists. watt himself apparently appreciated the possibilities no more fully than the others, as the use of his famous engines "beelzebub" and "old bess" in the establishment of boulton and watt amply testifies. it appears that boulton had been an extensive manufacturer of ornamental metal articles. to drive his machinery at soho he employed two large water wheels, twenty-four feet in diameter and six feet wide. these sufficed for his purpose under ordinary conditions, but in dry weather from six to ten horses were required to aid in driving the machinery. when watt's perfected engine was available, however, this was utilized to pump water from the tail race back to the head race, that it might be used over and over. "old bess" had a cylinder thirty-three inches in diameter with seven-foot stroke, operating a pump twenty-four inches in diameter; it therefore had remarkable efficiency as a pumping apparatus. but of course it utilized, at best, only a portion of the working energy contained in the steam; and the water wheels in turn could utilize not more than fifty per cent. of the store of energy which the pump transferred to the water in raising it. therefore, such use of the steam engine involved a most wasteful expenditure of energy. it was long, however, before the practical machinists could be made to believe that the securing of direct rotary power from the piston could be satisfactorily accomplished. it was only after the introduction of higher speed and heavier fly-wheels, together with improved governors, that the speed of rotation was so equalized as to meet satisfactorily the requirements of the practical engineer, and ultimately to displace the wasteful method of securing rotary motion indirectly through the aid of pump and water wheel. it may be added, that the centrifugal governor, with which modern engines are provided to regulate their speed, was the invention of watt himself. final improvements and missed opportunities in the year 1782 watt took out patents which contained specifications for the two additional improvements that constituted his final contribution to the production of the steam engine. the first of these provided for the connection of the cylinder chamber on each side of the piston with the condenser, so that the engine became double acting. the second introduced the very important principle,--from the standpoint of economy in the use of steam--of shutting off the supply of steam from the cylinder while the piston has only partially traversed its thrust, and allowing the remainder of the thrust to be accomplished through the expansion of the steam. the application of the first of these principles obviously adds greatly to the efficiency of the engine, and in practise it was found that the application of the second principle produces a very great saving in steam, and thus adds materially to the economical working of the engine. all of watt's engines continued to make use of the walking beam attached to the piston for the transmission of power; and engineers were very slow indeed to recognize the fact that in many--in fact in most--cases this contrivance may advantageously be done away with. the recognition of this fact constitutes one of the three really important advances that have been made in the steam engine since the time of watt. the other two advances consist of the utilization of steam under high pressure, and of the introduction of the principle of the compound engine. neither of these ideas was unknown to watt, since the utilization of steam under high pressure was advocated by his contemporary, trevithick, while the compound engine was invented by another contemporary named hornblower. perhaps the very fact that these rival inventors put forward the ideas in question may have influenced watt to antagonize them; in particular since his firm came into legal conflict with each of the other inventors. at any rate, watt continued to the end of his life to be an ardent advocate of low pressure for the steam engine, and his firm even attempted to have laws passed making it illegal--on the ground of danger to human life--to utilize high-pressure steam, such as employed by trevithick. possibly the conservatism of increasing age may also have had its share in rendering watt antagonistic to the new ideas; for he was similarly antagonistic to the idea of applying steam to the purposes of locomotion. trevithick, among others, had, as we shall see in due course, made such application with astonishing success, producing a steam automobile which traversed the highway successfully. in his earlier years watt had conceived the same idea, and had openly expressed his opinion that the steam engine might be used for this purpose. but late in life he was so antipathetic to the idea that he is said to have put a clause in the lease of his house, providing that no steam carriage should under any pretext be allowed to approach it. these incidents have importance as showing--as we shall see illustrated again and again in other fields--the disastrous influence in retarding progress that may be exercised by even the greatest of scientific discoverers, when authority well earned in earlier years is exercised in an unfortunate direction later in life. but such incidents as these are inconsequential in determining the position among the world's workers of the man who was almost solely responsible for the transformation of the steam engine from an expensive and relatively ineffective pumping apparatus, to the great central power that has ever since moved the major part of the world's machinery. the supreme importance of watt it is speaking well within bounds to say that no other invention within historical times has had so important an influence upon the production of property--which, as we have seen, is the gauge of the world's work--as this invention of the steam engine. we have followed the history of that invention in some detail, because of its supreme importance. to the reader who was not previously familiar with that history, it may seem surprising that after a lapse of a little over a century one name and one alone should be popularly remembered in connection with the invention; whereas in point of fact various workers had a share in the achievement, and the man whose name is remembered was among the last to enter the field. we have seen that the steam engine existed as a practical working machine several decades before watt made his first invention; and that what watt really accomplished was merely the perfecting of an apparatus which already had attained a considerable measure of efficiency. there would seem, then, to be a certain lack of justice in ascribing supreme importance to watt in connection with the steam engine. yet this measure of injustice we shall find, as we examine the history of various inventions, to be meted always by posterity in determining the status of the men whom it is pleased to honor. one practical rule, and one only, has always determined to whom the chief share of glory shall be ascribed in connection with any useful invention. the question is never asked as to who was the originator of the idea, or who made the first tentative efforts towards its utilization,--or, if asked by the historical searcher, it is ignored by the generality of mankind. so far as the public verdict, which in the last resort determines fame, is concerned, the one question is, who perfected the apparatus so that it came to have general practical utility? it may be, and indeed it usually is the case, that the man who first accomplished the final elaboration of the idea, made but a comparatively slight advance upon his predecessors; the early workers produced a machine that was _almost_ a success; only some little flaw remained in their plans. then came the perfecter, who hit upon a device that would correct this last defect,--and at last the mechanism, which hitherto had been only a curiosity, became a practical working machine. in the case of the steam engine, it might be said that even a smaller feat than this remained to be accomplished when watt came upon the scene; since the newcomen engine was actually a practical working apparatus. but the all-essential thing to remember is that this newcomen engine was used for a single purpose. it supplied power for pumping water, and for nothing else. neither did it have possibilities much beyond this, until the all-essential modification was suggested by watt, of exhausting its steam into exterior space. this modification is in one sense a mere detail, yet it illustrates once more the force of michelangelo's famous declaration that trifles make perfect; for when once it was tested, the whole practical character of the steam engine was changed. from a wasteful consumer of fuel, capable of running a pump at great expense, it became at once a relatively economical user of energy, capable of performing almost any manner of work. needless to say, its possibilities in this direction were not immediately realized, in theory or in practise; yet the conquest that it made of almost the entire field of labor resulted in the most rapid transformation of industrial conditions that the world has ever experienced. after all, then, there is but little injustice in that public verdict which remembers james watt as the inventor, rather than as the mere perfecter, of the steam engine. the personality of james watt the man who occupies this all-important position in the industrial world demands a few more words as to his personality. his work we have sufficiently considered, but before we pass on to the work of his successors, it will be worth our while to learn something more of the estimate placed upon the man himself. let us quote, then, from some records written by men who were of the same generation. "independently of his great attainments in mechanics, mr. watt was an extraordinary and in many respects a wonderful man. perhaps no individual in his age possessed so much, or remembered what he had read so accurately and well. he had infinite quickness of apprehension, a prodigious memory, and a certain rectifying and methodizing power of understanding which extracted something precious out of all that was presented to it. his stores of miscellaneous knowledge were immense, and yet less astonishing than the command he had at all times over them. it seemed as if every subject that was casually started in conversation had been that which he had been last occupied in studying and exhausting; such was the copiousness, the precision, and the admirable clearness of the information which he poured out upon it without effort or hesitation. nor was this promptitude and compass of knowledge confined, in any degree, to the studies connected with his ordinary pursuits. "that he should have been minutely and extensively skilled in chemistry, and the arts, and in most of the branches of physical science, might, perhaps, have been conjectured; but it could not have been inferred from his usual occupations, and probably is not generally known, that he was curiously learned in many branches of antiquity, metaphysics, medicine, and etymology, and perfectly at home in all the details of architecture, music, and law. he was well acquainted, too, with most of the modern languages, and familiar with their most recent literature. nor was it at all extraordinary to hear the great mechanician and engineer detailing and expounding, for hours together, the metaphysical theories of the german logicians, or criticizing the measures or the matter of the german poetry. "it is needless to say, that with those vast resources, his conversation was at all times rich and instructive in no ordinary degree. but it was, if possible, still more pleasing than wise, and had all the charms of familiarity, with all the substantial treasures of knowledge. no man could be more social in his spirit, less assuming or fastidious in his manners, or more kind and indulgent towards all who approached him. his talk, too, though overflowing with information, had no resemblance to lecturing, or solemn discoursing; but, on the contrary, was full of colloquial spirit and pleasantry. he had a certain quiet and grave humor, which ran through most of his conversation, and a vein of temperate jocularity, which gave infinite zest and effect to the condensed and inexhaustible information which formed its main staple and characteristic. there was a little air of affected testiness, and a tone of pretended rebuke and contradiction, which he used towards his younger friends, that was always felt by them as an endearing mark of his kindness and familiarity, and prized accordingly, far beyond all the solemn compliments that proceeded from the lips of authority. his voice was deep and powerful; though he commonly spoke in a low and somewhat monotonous tone, which harmonized admirably with the weight and brevity of his observations, and set off to the greatest advantage the pleasant anecdotes which he delivered with the same grave tone, and the same calm smile playing soberly on his lips. [illustration: james watt.] "there was nothing of effort, indeed, or of impatience, any more than of pride or levity, in his demeanor; and there was a finer expression of reposing strength, and mild self-possession in his manner, than we ever recollect to have met with in any other person. he had in his character the utmost abhorrence for all sorts of forwardness, parade, and pretension; and indeed never failed to put all such impostors out of countenance, by the manly plainness and honest intrepidity of his language and deportment. "he was twice married, but has left no issue but one son, associated with him in his business and studies, and two grandchildren by a daughter who predeceased him. he was fellow of the royal societies both of london and edinburgh, and one of the few englishmen who were elected members of the national institute of france. all men of learning and of science were his cordial friends; and such was the influence of his mild character, and perfect fairness and liberality, even upon the pretender to these accomplishments, that he lived to disarm even envy itself, and died, we verily believe, without a single enemy." vi the master worker we have already pointed out at some length that, in the hands of watt, the steam engine came at once to be a relatively perfect apparatus, and that only three really important modifications have been applied to it since the day of its great perfecter. these modifications, as already named, are the doing away with the walking beam, the utilization of high pressure steam, and the development of the compound engine. each of these developments requires a few words of explanation. the retention of the heavy walking beam for so long a time after the steam engine of watt had been applied to the various purposes of machinery, illustrates the power of a pre-conceived idea. with the newcomen engine this beam was an essential, since it was necessary to have a weight to assist in raising the piston. but with the introduction of steam rather than air as the actual power to push the piston, and in particular with the elaboration of the double-chamber cylinder, with steam acting equally on either side of the piston, the necessity for retaining this cumbersome contrivance no longer existed. yet we find all the engines made by watt himself, and nearly all those of his contemporaries, continuing to utilize this means of transmitting the power of the piston. even the road locomotive, as illustrated by that first wonderful one of trevithick's and such colliery locomotives as "puffing billy" and "locomotion," utilized the same plan. it was not until almost a generation later that it became clear to the mechanics that in many cases, indeed in most cases, this awkward means of transmitting power was really a needlessly wasteful one, and that with the aid of fly-wheel and crank-shaft the thrust of the piston might be directly applied to the wheel it was destined to turn, quite as well as through the intermediary channel of the additional lever. the utility of the beam has, indeed, still commended it for certain purposes, notably for the propulsion of side-wheel steamers, such as the familiar american ferryboat. but aside from such exceptional uses, the beam has practically passed out of existence. there was no new principle involved in effecting this change. it was merely another illustration of the familiar fact that it is difficult to do things simply. as a rule, inventors fumble for a long time with roundabout and complex ways of doing things, before a direct and simple method occurs to them. in other words, the highest development often passes from the complex to the simple, illustrating, as it were, an oscillation in the great law of evolution. so in this case, even so great an inventor as watt failed to see the utility of doing away with the cumbersome structure which his own invention had made no longer a necessity, but rather a hindrance to the application of the steam engine. however, a new generation, no longer under the thraldom of the ideas of the great inventor, was enabled to make the change, gradually, but in the end effectively. high-pressure steam as regards the use of steam under high pressure, somewhat the same remarks apply, so far as concerns the conservatism of mankind, and the influence which a great mind exerts upon its generation. just why watt should have conceived an antagonism to the idea of high-pressure steam is not altogether clear. it has been suggested, indeed, that this might have been due to the fact that a predecessor of watt had invented a high-pressure engine which did not use the principle of condensation, but exhausted the steam into open space. as early as 1725, indeed, leupold in his _theatrum machinarum_, had described such a non-condensing engine, which, had it been made practically useful, would have required a high pressure of steam. partly through the influence of this work, perhaps, there came to be an association between the words high pressure and non-condensing, so that these terms are considered to be virtually synonymous; and since watt's great contribution consisted of an application of the idea of condensation, he was perhaps rendered antagonistic to the idea of high pressure, through this psychological suggestion. in any event, the antagonism unquestionably existed in his mind; though it has often enough been pointed out that this seems the more curious since high-pressure steam would so much better have facilitated the application of that other famous idea of watt, the use of the expansive property of steam. curiously enough, however, the influence of watt led to experiments in high-pressure steam through an indirect channel. the contemporary inventor, trevithick, in connection with his partner, bull, had made direct-acting pumping engines with an inverted cylinder, fixed in line with the pump rod, and actually dispensing with the beam. but as these engines used a jet of cold water in the exhaust pipe to condense the steam, boulton and watt brought suit successfully for infringement of their patent, and thus prevented trevithick from experimenting further in that direction. he was obliged, therefore, to turn his attention to a different method, and probably, in part at least, in this way was led to introduce the non-condensing, relatively high-pressure engine. this was used about the year 1800. at the same time somewhat similar experiments were made by oliver evans in america. both trevithick and evans applied their engines to the propulsion of road vehicles; and trevithick is credited with being the first man who ran a steam locomotive on a track,--a feat which he accomplished as early as the year 1804. we are not here concerned with the details of this accomplishment, which will demand our attention in a later chapter, when we come to discuss the entire subject of locomotive transportation. but it is interesting to recall that the possibilities of the steam engine were thus early realized, even though another generation elapsed before they were finally demonstrated to the satisfaction of the public. it is particularly interesting to note that in his first locomotive engine, trevithick allowed the steam exhaust to escape into the funnel of the engine to increase the draught,--an expedient which was so largely responsible for stephenson's success with his locomotive twenty years later, and which retains its utility in the case of the most highly developed modern locomotive. trevithick was, however, entirely subordinated by the great influence of watt, and the use of high pressure was in consequence discountenanced by the leading mechanical engineers of england for some decades. meantime, in america, the initiative of evans led to a much earlier general use of high-pressure steam. in due course, however, the advantages of steam under high pressure became evident to engineers everywhere, and its conquest was finally complete. the essential feature of super-heated steam is that it contains, as the name implies, an excess of heat beyond the quantity necessary to produce mere vaporization, and that the amount of water represented in this vapor is not the maximum possible under given conditions. in other words, the vapor is not saturated. it has been already explained that the amount of vapor that can be taken up in a given space under a given pressure varies with the temperature of the space. under normal conditions, when a closed space exists above a liquid, evaporation occurs from the surface of the liquid until the space is saturated, and no further evaporation can occur so long as the temperature and pressure are unchanged. if now the same space is heated to a higher degree, more vapor will be taken up until again the point of saturation is attained. but, obviously, if the space were disconnected with the liquid, and then heated, it would acquire a capacity to take up more vapor, and so long as this capacity was latent, the vapor present would exist in a super-heated condition. [illustration: old ideas and new applied to boiler construction. the lower figure shows robert trevithick's famous boiler, used in operating his locomotive about the year 1804. the original is preserved in the south kensington museum, london. the upper figure shows a modern tubular boiler, by way of contrast.] it will be understood from what has been said before, that with all accessions of heat, the expansive power of the vapor is increased,--its molecules becoming increasingly active; hence one of the very obvious advantages of super-heated steam for the purpose of pushing a piston. there are other advantages, however, which are not at first sight so apparent, having to do with the properties of condensation. to understand these, we must pay heed for a few moments to the changes that take place in steam itself in the course of its passage through the cylinder, where it performs its work upon the piston. many of these changes were not fully understood by the earlier experimenters, including watt. indeed the theory of the steam engine, or rather the general theory of the heat engine, was not worked out until the year 1824, when the frenchman carnot took the subject in hand, and performed a series of classical experiments, which led to a nearly complete theoretical exposition of the subject. it remained, however, for the students of thermo-dynamics, about the middle of the nineteenth century, with clausius and rankine at their head, to perfect the theory of the steam engine, and the general subject of the mutual relations of heat and mechanical work. we are not here concerned with any elaboration of details, but merely with a few of the essential principles which enter practically into the operation of the steam engine. it appears, then, that when steam enters the cylinder and begins to thrust back the piston of the steam engine, a portion of the steam is immediately condensed on the walls of the cylinder, owing to the fact that previous condensation of steam has cooled these walls to a certain extent. we have already pointed out that watt endeavored in his earlier experiments to overcome this difficulty, by equalizing the temperature of the cylinder walls to the greatest practicable extent. notwithstanding his efforts, however, and those of numberless later experimenters, it still remains true that under ordinary conditions, particularly if steam enters the cylinder at the saturation point, a very considerable condensation occurs. indeed this may amount to from thirty to fifty per cent. of the entire bulk of water contained in the quantity of steam that enters the cylinder. this condensation obviously militates against the expansive or working power of the steam. but now as the steam expands, pushing forward the cylinder, it becomes correspondingly rarefied, and immediately a portion of the condensed steam becomes again vaporized, and in so doing it takes up a certain amount of heat and renders it latent. this disadvantageous cycle of molecular transformations is very much modified in the case of super-heated steam, for the obvious reason that such steam may be very much below the saturation point, and hence requires a very much greater lowering of temperature in order to produce condensation of any portion of its mass. without elaborating details, it suffices to note that in all highly efficient modern engines, steam is employed at a relatively high pressure, and that sometimes this pressure becomes enormous. compound engines as to the compound engine, that also, as has been pointed out, was invented by a contemporary of watt, jonathan hornblower by name, whose patent bears date of 1781. in hornblower's engine, steam was first admitted to a small cylinder, and then, after performing its work on the piston, was allowed to escape, not into a condensing receptacle, but into a larger cylinder where it performed further work upon another piston. this was obviously an instance of the use of steam expansively, and it has been pointed out that, in consequence, hornblower was the first to make use of this idea in practise, although it is said that watt's experiments had even at that time covered this field. the application of the idea to the movement of the second cylinder, however, appears to have been original with hornblower. certainly it owed nothing to watt, who refused to accept the idea, and continued throughout his life to frown upon the compound engine. nevertheless, the device had great utility, as subsequent experiments were very fully to demonstrate. the compound engine was revived by woolf in 1804, and his name rather than hornblower's is commonly associated with it. the latter experimenter demonstrated that the compound engine has two important merits as against the simple engine. one of these is that the sum of the two forces exerted by the joint action results in a more even and continuous pressure throughout the cycle than could be accomplished by the action of a single cylinder. to understand this it must be recalled that when using the expansive property of steam, the piston thrust could not possibly be uniform, since the greatest pressure exerted by the steam would be exerted at the moment before it was shut off from the boiler, and its pressure must then decrease progressively, as it exerts more and more work upon the piston and becomes more expanded, thus obviously retaining less elastic energy. the operation of the fly-wheel largely compensates this difference of pressure in practise, but it would be obviously advantageous could the pressure be equalized; and, as just stated, the compound engine tends to produce this result. the second, and perhaps the more important merit of the compound engine is, that it is found in practise to keep the cylinders at a more uniform temperature. a moment's reflection makes it clear why this should be the case, since in a single-cylinder engine the exhaust connects with the cool condenser, whereas in the compound engine the exhaust from the first cylinder connects with the second cylinder at only slightly lower temperature. in many modern engines a third cylinder and sometimes even a fourth is added, constituting what are called respectively triple-expansion and quadruple-expansion engines. the triple-expansion system is very generally employed, especially where it is peculiarly desirable to economize fuel, as, for example, in the case of ships. [illustration: compound engines. the lower figure illustrates the use of a modern compound engine, directly operating the propeller shaft of a steamship. the middle figure shows a similarly direct application of power to the axes of paddle wheels. the upper figure shows the application of power through a walking beam similar in principle to that of the original newcomen and watt engines.] rotary engines all these improvements, it will be observed, have to do with details that do not greatly modify the steam engine from the original type. the cylinder with its closely fitting piston, as introduced in the newcomen engine, is retained and constitutes the essential mechanism through which the energy of steam is transferred into mechanical energy. but from a comparatively remote period the idea has prevailed that it might be possible to utilize a different principle; that, in short, if the steam instead of being made to press against a piston were allowed to rush against fan-like blades, adjusted to an axle, it might cause blades and axle to revolve, precisely as a windmill is made to revolve by the pressure of the wind, or the turbine wheel by the pressure of water. in a word, it has been believed that a turbine engine might be constructed, which would utilize the energy of the steam as advantageously as it is utilized in the piston engine, and at the same time would communicate its power as a direct rotation, instead of as a straight thrust that must be translated into a rotary motion by means of a crank or other mechanism. in point of fact, james watt himself invented such an engine, and patented it in 1782, though there is no evidence that he ever constructed even a working model. his patent specifications show "a piston in the form of a closely-fitting radial arm, projecting from an axial shaft in a cylinder. an abutment, arranged as a flap is hinged near a recess in the side of the cylinder, and swings while remaining in contact with the piston. steam is admitted to the chamber on one side of the flap, and so causes an unbalanced pressure upon the radial arm." this arrangement has been re-invented several times. essentially the same principle is utilized by joshua routledge, whose name is well known in connection with the engineer's slide-rule. a model of this engine is preserved in the south kensington museum, and the apparatus is described in the catalogue of the museum as follows: "the piston revolves on a shaft passing through the centre of the cylinder casing. the flap or valve hinged to the casing, with its free end resting upon the piston, acts like the bottom of an ordinary engine cylinder. the steam inlet port is on one side of the hinge, and the exhaust port on the other. the admission of steam is controlled by a side valve, actuated by an eccentric on the fly-wheel shaft, so that the engine could work expansively, and the steam pressure resisting the lifting of the flap would also be greatly reduced, so diminishing the knock at this point, which, however, would always be a serious cause of trouble. the exhaust steam passes down to a jet condenser, provided with a supply of water from a containing tank, from which the injection is admitted through a regulating valve. the air pump, which draws the air and water from the condenser and discharges them through a pipe passing out at the end of the tank, is a rotary machine constructed like the engine and driven by spur gearing from the fly-wheel shaft. some efforts have been made to prevent leakage by forming grooves in the sides of the revolving piston and filling them with soft packing." sundry other rotary engines, some of them actual working models, are to be seen at the south kensington museum. there is, for example, one invented by the rev. patrick bell, a gentleman otherwise known to fame as one of the earliest inventors of a practical reaping machine. in this apparatus, "a metal disc is secured to a horizontal axis carried in bearings, and the lower half of the disc is enclosed by a chamber of circular section having its axis a semi-circle. one end of this chamber is closed and provided with a pipe through which steam enters, the exhaust taking place through the open end. the disc is provided with three holes, each fitted with a circular plate turning on an axis radial to the disc, and these plates when set at right angles to the disc become pistons in the lower enclosing chamber. toothed gearing is arranged to rotate these pistons into the plane of the disc on leaving the cylinder and back again immediately after entering, locking levers retaining them in position during the intervals. the steam pressure upon these pistons forces the disc round, but the engine is non-expansive, and although some provision for packing has been made, the leakage must have been considerable and the wear and tear excessive." it is stated that almost the same arrangement was proposed by lord armstrong in 1838 as a water motor, and that a model subsequently constructed gave over five horse-power at thirty revolutions per minute, with an efficiency of ninety-five per cent. another working model of a rotary engine shown at the museum is one loaned by messrs. fielding and platt in 1888. "the action of this engine depends upon the oscillating motion which the cross of a universal joint has relative to the containing jaws when the system is rotated. "two shafts are set at an angle of 165 deg. to each other and connected by a hooke's joint; one serves as a pivot, the power being taken from the other. four curved pistons are arranged on the cross-piece, two pointing towards one shaft and two towards the other, and on each shaft or jaw are formed two curved steam cylinders in which the curved pistons work. the steam enters and leaves the base of each cylinder through ports in the shaft, which forms a cylindrical valve working in the bearing as a seating. "on the revolution of the shafts the pistons reciprocate in their cylinders in much the same way as in an ordinary engine, and the valve arrangement is such that while each piston is receding from its cylinder the steam pressure is driving it, and during the in-stroke of each, its cylinder is in communication with the exhaust. there are thus four single-acting cylinders making each a double stroke for one revolution of the driving-shaft. the engine has no dead centres, and has been at 1,000 revolutions per minute." [illustration: rotary engines. the three types of rotary engines here shown are similar in principle, and none of them is of great practical value, though the upper figure shows an engine that has met with a certain measure of commercial success.] it is not necessary to describe other of the rotary engines that have been made along more or less similar lines by numerous inventors, models of which are for the most part, as in the case of those just described, to be seen more commonly in museums than in practical workshops. reference may be made, however, to a rotary engine which was invented by a mr. hoffman, of buffalo, new york, about the beginning of the twentieth century, an example of which was put into actual operation in running the machinery of a shop in buffalo, in 1905. this engine consists of a solid elliptical shaft of steel, fastened to an axle at one side of its centre, which axis is also the shaft of the cylinder, which revolves about the central ellipse in such a way that at one part of the revolution the cylinder surface fits tightly against the ellipse, while the opposite side of the cylinder supplies a free chamber between the ellipse and the cylinder walls. running the length of the cylinder are two curved pieces of steel, like longitudinal sections of a tube. these flanges are adjusted at opposite sides of the cylinder and so arranged that their sides at all times press against the ellipse, alternately retreating into the substance of the cylinder, and coming out into the free chamber. steam is admitted to the free chamber through one end of the shaft of ellipse and cylinder and exhausted through the other end. the pressure of the steam against first one end and then the other of the flanges supplies the motive power. this pressure acts always in one direction, and the entire apparatus revolves, the cylinder, however, revolving more rapidly than the central ellipse. for this engine the extravagant claim is made that there is no limit to its speed of revolution, within the limit of resistance of steel to centrifugal force. it has been estimated that a locomotive might be made to run two hundred or three hundred miles an hour without difficulty, with the hoffman engine. such estimates, however, are theoretical, and it remains to be seen what the engine can do in practise when applied to a variety of tasks, and what are its limitations. certainly the apparatus is at once ingenious and simple in principle, and there is no obvious theoretical reason why it should not have an important future. turbine engines whatever the future may hold, however, it remains true that the first practical solution of the problem of securing direct rotary motion from the action of steam, on a really commercial scale, was solved with an apparatus very different from any of those just described, the inventor being an englishman, mr. c. a. parsons, and the apparatus the steam turbine, the first model of which he constructed in 1884, and which began to attract general attention in the course of the ensuing decade. public interest was fully aroused in 1897, when mr. parson's boat, the _turbinia_, equipped with engines of this type, showed a trial speed of 32-3/4 knots per hour, a speed never hitherto attained by any other species of water craft. more recently, a torpedo boat, the _viper_, equipped with engines developing about ten thousand horse-power, attained a speed of 35-1/2 knots. the success of these small boats led to the equipment of large vessels with the turbine, and on april first, 1905, the first transatlantic liner propelled by this form of engine steamed into the harbor of halifax, nova scotia. this first ocean liner equipped with the turbine engine is called the _victorian_. she is a ship five hundred and forty feet long and sixty feet wide, carrying fifteen hundred passengers. the _victorian_ had shown a speed of 19-1/2 knots an hour on her trial trip, and it had been hoped that she would break the transatlantic record. on her first trip, however, she encountered adverse winds and seas, and did not attain great speed. her performance was, however, considered entirely satisfactory and creditable. in the ensuing half-decade several large ships were equipped with engines of the same type, the most famous of these being the cunard liners, _carmania_, _lusitania_, and _mauretania_. the two last-named ships are sister craft, and they are the largest boats of any kind hitherto constructed. the _lusitania_ was first launched and she entered immediately upon a record-breaking career, only to be surpassed within a few months by the _mauretania_, which soon acquired all records for speed and endurance. fuller details as to the performance of these vessels will be found in another place. here we are of course concerned with the parsons turbine engine itself rather than with its applications. this turbine engine constitutes the first really important departure from the old-type steam engine, thus realizing the dream of the seventeenth-century italian, branca, to which reference was made above. mr. parsons' elaboration of the idea developed a good deal of complexity as regards the number of parts involved, yet his engine is of the utmost simplicity in principle. it consists of a large number of series of small blades, each series arranged about a drum which revolves. between the rings of revolving blades are adjusted corresponding rings of fixed blades, which project from the casing to the cylinder, and by means of which the steam is regulated in direction, so that it strikes at the proper angle against the revolving blades of the turbine. in practise, three series of cylindrical drums are used, each containing a large number of rings of blades of uniform size; but each successive drum having longer blades, to accommodate the greater volume of the expanding steam. the steam is fed against the first series of blades in gusts, which may be varied in frequency and length to meet the requirements of speed. after impinging on the first circle of blades, the steam passes to the next under slightly reduced pressure, and the pressure is thus successively stepped down from one set of blades to another until it is ultimately reduced from say two hundred pounds to the square inch, to one pound to the square inch before it passes to the condenser and ceases to act. there is thus a fuller utilization of the kinetic energy of the gas, through carrying it from high to low pressure, than is possible with the old type of cylinder-and-piston engine. on the other hand, there is a constant loss due to the fact that the blades of the turbine can not fit with absolute tightness against the cylinder walls. the net result is that the compound turbine, as at present developed, appears to have about the same efficiency as the best engine of the old type. one capital advantage of the turbine is that it keeps the cylinder walls at a more uniform temperature than is possible even with a compound engine of the old type. another advantage is that the power of the turbine is applied directly to cause rotation of the shaft, whereas no satisfactory means has ever been discovered hitherto of making the action of the steam engine rotary, except with the somewhat disadvantageous crank-shaft. this fact of adjustment of the turbine blades to the revolving shaft seems to make this form of engine particularly adapted to use in steamships. it is also highly adapted to revolving the shaft of a dynamo, and has been largely applied to this use. needless to say, however, it may be applied to any other form of machinery. it would be difficult at the present stage of its development to predict the extent to which the turbine will ultimately supersede the old type of engine. its progress has already been extraordinary, however, as an engineer pointed out in the london _times_ of august 14, 1907, in the following words: "when the steam turbine was introduced by mr. parsons some 25 years ago, in the form of a little model, which is now in the south kensington museum, and the rotor of which may easily be held stationary by the hand against the full blast of the steam, who would have been rash enough to predict, except perhaps the far-seeing inventor himself, that a vessel 760 feet long, loaded to 37,000 tons displacement, drawing 32 ft. 9 in. of water, and providing accommodation for 2,500 people, could be propelled at a speed of 24.5 knots per hour, which it is hoped she may maintain over the 3,000 miles of the atlantic voyage? "from this small model, which will in time become as historic as the _rocket_ of stephenson, and which is only some few inches in diameter, the turbine has been developed gradually in size. the cylindrical casings which take the place of the complicated machinery of the piston engine in the engine room of the _lusitania_ contain drums, which in the high-pressure turbines are 8 feet in diameter and in the low-pressure 11 ft. 8 in., and from which thousands of curved blades project, the longest of which are 22 inches, and against which the steam impinges in its course from the boiler to the condenser. "not only has the steam turbine justified the confidence of those who have labored so successfully in its development, but no other great invention has proceeded from the laboratory stage to such an important position in the engineering world in such a short space of time. this would not have happened if some inherent drawback, such as lack of economy in steam consumption, existed, and as the turbine has been proved to be, for land purposes, very economical, there seems to be no reason to doubt that marine turbines, working as they do at full load almost continually, will show likewise that the coal bill is not increased, but perhaps diminished by their use. "the records of the vibrations of the hull which were taken during the trials by schlick's instruments showed that the vertical vibration was 60 per minute on the run, which was due to the propellers, and which may be further modified. the horizontal vibration was almost unnoticeable, while the behavior of the ship in the heavy seas she encountered in her long-distance runs was good, the roll from side to side having a period of 18 seconds. the great length of this ship and the gyrostatic action of the heavy rotating masses of the machinery ought to render her almost insensible to the heaviest atlantic rollers; certainly as far as pitching is concerned." [illustration: the original parson's turbine engine and the record-breaking ship for which it is responsible. this small turbine engine, with which mr. parson's early experiments were made in 1884, is preserved in the south kensington museum, london. at the time when it was made it seemed scarcely more than a toy, and engineers in general doubted that the principle it employed could ever be made commercially available. yet within the lifetime of its inventor engines built on this model have come to be the most powerful of force transmuters. the "mauretania," the largest, and thanks to her turbine engines the speediest, of ships, is here presented on the same page with the little original turbine model, as illustrating vividly the practical development of a seemingly visionary idea.] a more general comment upon the turbine engine, with particular reference to its use in america, is made by mr. edward h. sanborn in an article on _motive power appliances_, in the twelfth census report of the united states, vol. x. part iv. "apart from its demonstrated economy," says mr. sanborn, "other important advantages are claimed for the steam turbine, some of which are worthy of brief mention. "there is an obvious advantage in economy of space as compared with the reciprocating engine. the largest steam turbine constructed in the united states is one of 3,000 horse-power, which is installed in the power house of the hartford electric light company, hartford, conn. the total weight of this motor is 28,000 pounds, its length over all is 19 feet 8 inches, and its greatest diameter six feet. with the generator to which it is directly connected, it occupies a floor space of 33 feet 3 inches long by 8 feet 9 inches wide. "friction is reduced to a minimum in the steam turbine, owing to the absence of sliding parts and the small number of bearings. the absence of internal lubrication is also an important consideration, especially when it is desired to use condensers. "as there are no reciprocating parts in a steam turbine, and as a perfect balance of its rotating parts is absolutely essential to its successful operation, vibration is reduced to such a small element that the simplest foundations will suffice, and it is safe to locate steam turbines on upper floors of a factory if this be desirable or necessary. "the perfect balance of the moving parts and the extreme simplicity of construction tend to minimize the wear and increase the life of a turbine, and at the same time to reduce the chance of interruption in its operation through derangement of, or damage to, any of its essential parts. "although hardly beyond the stage of its first advent in the motive-power field, the steam turbine has met with much favor, and there is promise of its wide use for the purposes to which it is particularly adapted. at present, however, its uses are restricted to service that is continuous and regular, its particular adaptability being for the driving of electrical generators, pumps, ventilating fans, and similar work, especially where starting under load is not essential. "steam turbines are now being built in the united states in all sizes up to 3,000 horse-power. their use abroad covers a longer period and has become more general. the largest turbines thus far attempted are those of the metropolitan district electric traction company, of london, embracing four units of 10,000 horse-power each. several turbines of large size have been operated successfully in germany." it should be added that the compound turbine wheel of parsons is not the only turbine wheel that has proved commercially valuable. there is a turbine consisting of a single ring of revolving blades, the invention of dr. gustav de laval, which has proved itself capable of competing with the old type of engine. to make this form of single turbine operate satisfactorily, it is necessary to have steam under high pressure, and to generate a very high speed of revolution. in practice, the de laval machines sometimes attain a speed of thirty thousand revolutions per minute. this is a much higher rate of speed than can advantageously be utilized directly in ordinary machinery, and consequently the shaft of this machine is geared to another shaft in such a way as to cause the second shaft to revolve much more slowly. vii gas and oil engines just at the time when the type of piston-and-cylinder engine has thus been challenged, it has chanced that a new motive power has been applied to the old type of engine, through the medium of heated gas. the idea of such utilization of a gas other than water vapor is by no means new, but there have been practical difficulties in the way of the construction of a commercial engine to make use of the expansive power of ordinary gases. the principle involved is based on the familiar fact that a gas expands on being heated and contracts when cool. theoretically, then, all that is necessary is to heat a portion of air confined in a cylinder, to secure the advantage of its expansion, precisely as the expansion of steam is utilized, by thrusting forward a piston. such an apparatus constitutes a so-called "caloric" or hot-air engine. as long ago as the year 1807 sir g. cayley in england produced a motor of this type, in which the heated air passed directly from the furnace to the cylinder, where it did work while expanding until its pressure was not greater than that of the atmosphere, when it was discharged. the chief mechanical difficulty encountered resulted from the necessity for the employment of very high temperatures; and for a long time the engine had no great commercial utility. the idea was revived, however, about three-quarters of a century later and an engine operated on cayley's principle was commercially introduced in england by mr. buckett. this engine has a cold-air cylinder above the crank-shaft and a large hot-air cylinder below, while the furnace is on one side enclosed in an air-tight chamber. the fuel is supplied as required through a valve and distributing cone arranged above the furnace and provided with an air lock in which the fuel is stored. at about the time when this hot-air engine was introduced, however, gas and oil engines of another and more important type were developed, as we shall see in a moment. meantime, an interesting effort to utilize the expansive property of heated air was made by dr. stirling in 1826; his engine being one in which heat was distributed by means of a displacer which moved the mass of air to and fro between the hot and cold portions of the apparatus. he also compressed the air before heating it, thus making a distinct advance in the economy and compactness of the engine. from an engineering standpoint his design has further interest in that it was a practical attempt to construct an engine working on the principle of the theoretically perfect heat engine, in which the cycle of operations is closed, the same mass of air being used throughout. in the theoretically perfect heat engine, it may be added, the cycle of operations may be reversed, there being no loss of energy involved; but in practice, of course, an engine cannot be constructed to meet this ideal condition, as there is necessarily some loss through dissipation of heat. dr. stirling's practical engine had its uses, but could not compete with the steam engine in the general field of mechanical operations to which that apparatus is applied. another important practical experimenter in the construction of hot-air engines was john ericsson, who in 1824 constructed an engine somewhat resembling the early one of cayley, and in 1852 built caloric engines on such a scale as to be adapted to the propulsion of ships. notwithstanding the genius of ericsson, however, engines of this type did not prove commercially successful on a large scale, and in subsequent decades the hot-air motors constructed for practical purposes seldom exceeded one horse-power. such small engines as these are comparatively efficient and absolutely safe, and they are thoroughly adapted for such domestic purposes as light pumping. the great difficulty with all these engines operated with heated air has been, as already suggested, that their efficiency of action is limited by the difficulties incident to applying high temperatures to large masses of the gas. there is, however, no objection to the super-heating of small quantities of gas, and it was early suggested that this might be accomplished by exploding a gaseous mixture within a cylinder. it was observed by the experimenters of the seventeenth century that an ordinary gun constitutes virtually an internal-combustion engine; and such experimenters as the dutchman huyghens, and the frenchmen hautefeuille and papin, attempted to make practical use of the power set free by the explosion of gunpowder, their experiments being conducted about the years 1678 to 1689. their results, however, were not such as to give them other than an historical interest. about a century later, in 1794, the englishman robert street suggested the use of inflammable gases as explosives, and ever since that time there have been occasional experimenters along that line. in 1823 samuel brown introduced a vacuum gas engine for raising water by atmospheric pressure. the first fairly practical gas engine, however, was that introduced by j. j. e. lenoir, who in 1850 proposed an engine working with a cycle resembling that of a steam engine. his engine patented in 1860 proved to be a fairly successful apparatus. this engine of lenoir prepared the way for gas engines that have since become so enormously important. its method of action is this: "to start the engine, the fly-wheel is pulled round, thus moving the piston, which draws into the cylinder a mixture of gas and air through about half its stroke; the mixture is then exploded by an electric spark, and propels the piston to the end of its stroke, the pressure meanwhile falling, by cooling and expansion, to that of the atmosphere when exhaust takes place. in the return stroke the process is repeated, the action of the engine resembling that of the double-acting steam engine, and having a one-stroke cycle. the cylinder and covers are cooled by circulating water. the firing electricity was supplied by two bunsen batteries and an induction coil, the circuit being completed at the right intervals by contact pieces on an insulating disc on the crank-shaft; the ignition spark leaped across the space between two wires carried about one-sixth of an inch apart in a porcelain holder." in 1865 mons. p. hugon patented an engine similar to that of lenoir, except that ignition was accomplished by an external flame instead of by electricity. the ignition flame was carried to and fro in a cavity inside a slide valve, moved by a cam so as to get a rapid cut-off, and permanent lights were maintained at the ends of the valve to re-light the flame-ports after each explosion. the gas was supplied to the cylinder by rubber bellows, worked by an eccentric on the crank-shaft. this engine could be operated satisfactorily, except as to cost, but the heavy gas consumption made it uneconomical. an important improvement in this regard was introduced by the germans, herrn. e. langen and n. a. otto, who under patents bearing date of 1866 introduced a so-called "free" piston arrangement--that is to say an arrangement by which the piston depends for its action partly upon the momentum of a fly-wheel. this principle had been proposed for a gas engine as early as 1857, but the first machine to demonstrate its feasibility was that of langen and otto. their engine greatly decreased the gas consumption and hence came to be regarded as the first commercially successful gas engine. it was, however, noisy and limited to small sizes. the cycle of operations of an engine of this type is described as follows: [illustration: gas and oil engines. lower right-hand figure, a very early type of commercially successful gas engine. it has a "free" piston, an arrangement that was first proposed for a gas engine in 1857, but only brought into practical form by langen & otto under their patent of 1866. upper figure, the gas engine patented by lenoir in 1860, one of the very first practically successful engines. lower left-hand figure, a sectional view of a modern gas engine of the type used as the motor of the automobile.] "(a) the piston is lifted about one-tenth of its travel by the momentum of the fly-wheel, thus drawing in a charge of gas and air. "(b) the charge is ignited by flame carried in by a slide valve. "(c) under the impulse of the explosion, the piston shoots upward nearly to the top of the cylinder, the pressure in which falls by expansion to about 4 lbs. absolute, while absorbing the energy of the piston. "(d) the piston descends by its own weight and the atmospheric pressure, and in doing so causes a roller-clutch on a spur-wheel gearing with a rack on the piston-rod to engage, so that the fly-wheel shaft shall be driven by the piston; during this down-stroke the pressure increases from 4 lbs. absolute to that of the atmosphere, and averages 7 lbs. per square inch effective throughout the stroke. "(e) when the piston is near the bottom of the cylinder, the pressure rises above atmospheric, and the stroke is completed by the weight of the piston and rack, and the products of combustion are expelled. "(f) the fly-wheel now continues running freely till its speed, as determined by a centrifugal governor, falls below a certain limit when a trip gear causes the piston to be lifted the short distance required to recommence the cycle. "ignition is performed by an external gas jet, near a pocket in the slide valve by which the charge is admitted; this pocket carries flame to the charge, thus igniting it without allowing any escape. the valve also connects the interior of the cylinder with the exhaust pipe, and a valve in the latter controlled by the governor throttles the discharge, and so defers the next stroke until the speed has fallen below normal. to run the engine empty about four explosions per minute are necessary, and at full power 30 to 35 are made, so that about 28 explosions per minute are available for useful work under the control of the governor." the definitive improvement in this gas engine was introduced in 1876 by dr. n. a. otto, when he compressed the explosive mixture in the working cylinder before igniting it. this expedient--so all-important in its results--had been suggested by william barnett in 1838, but at that time gas engines were not sufficiently developed to make use of the idea. now, however, dr. otto demonstrated that by compressing the gas before exploding it a much more diluted mixture can be fired, and that this gives a quieter explosion, and a more sustained pressure during the working stroke, while as the engine runs at a high speed the fly-wheel action is generally sufficient to correct the fluctuations arising from there being but one explosion for four strokes of the piston. in this perfected engine, then, the method of operation is as follows: the piston is pulled forward with the application of some outside force, which in practice is supplied by the inertia of the fly-wheel, or in starting the engine by the action of a crank with which every user of an automobile is familiar. in being pulled forward, the piston draws gas into the cylinder; as the piston returns, this gas is compressed; the compressed gas, constituting an explosive mixture, is then ignited by a piece of incandescent metal or by an electric spark; the exploding gas expands, pushing the piston forward, this being the only thrust during which work is done; the returning piston expels the expanded gas, completing the cycle. thus there are three ineffective piston thrusts to one effective thrust. nevertheless, the engine has proved a useful one for many purposes. this so-called otto cycle has been adopted in almost all gas and oil engines, the later improvements being in the direction of still higher compression, and in the substitution of lift for slide valves. there has been a steady increase in the size and power of such engines, the large ones usually introducing two or more working cylinders so as to secure uniform driving. cheap forms of gas have been employed such as those made by decomposing water by incandescent fuel, and it has been proved possible thus to operate gas-power plants on a commercial scale in competition with the most economical steam installations. a practical modification of vast importance was introduced when it was suggested that a volatile oil be employed to supply the gas for operation in an internal combustion engine. there was no new principle involved in this idea, and the otto cycle was still employed as before; but the use of the volatile oil--either a petroleum product or alcohol--made possible the compact portable engine with which everyone is nowadays familiar through its use in automobiles and motor boats. the oil commonly used is gasoline which is supplied to the cylinder through a so-called carburettor in which the vapors of gasoline are combined with ordinary air to make an explosive mixture. the introduction of this now familiar type of motor is to a large extent due to herr g. daimler, who in 1884 brought out a light and compact high-speed oil engine. about ten years later messrs. panhard and levassor devised the form of motor which has since been generally adopted. few other forms of mechanisms are better known to the general public than the oil engine with its two, four, six, or even eight cylinders, as used in the modern automobile. as everyone is aware, it furnishes the favorite type of motor, combining extraordinary power with relative lightness, and making it feasible to carry fuel for a long journey in a receptacle of small compass. with the gas engines a complication arises precisely opposite to that which is met with in the case of the cylinder of the steam engine--the tendency, namely, to overheating of the cylinder. to obviate this it is customary to have the cylinder surrounded by a water jacket, though air cooling is used in certain types of machines. about fifty per cent. of the total heat otherwise available is lost through this unavoidable expedient. the rapid introduction of the gas engine in recent years suggests that this type of engine may have a most important future. it has even been predicted that within a few years most trans-atlantic steamers will be equipped with this type of engine, producing their own gas in transit. it is possible, then, that through this medium the old piston-and-cylinder engine may retain its supremacy, as against the turbine. for the moment, at any rate, the gas engine is gaining popularity, not merely in its application to the automobile, but for numerous types of small stationary engines as well. in this connection it will be interesting to quote the report of the special agent of the twelfth census of the united states, as showing the status of gas engines and steam engines in the year 1902. "the decade between 1890 and 1900," he says, "was a period of marked development in the use of gas engines, using that term to denote all forms of internal combustible engines, in which the propelling force is the explosion of gaseous or vaporous fuel in direct contact with a piston within a closed cylinder. this group embraces those engines using ordinary illuminating gas, natural gas, and gas made in special producers installed as a part of the power plant, and also vaporised gasoline or kerosene. this form of power for the first time is an item of consequence in the returns of the present census, and the very large increase in the horse-power in 1900 as compared with 1890 indicates the growing popularity of this class of motive power. "in 1890 the number of gas engines in use in manufacturing plants was not reported, but their total power amounted to only 8,930 horse-power, or one-tenth of one per cent of the total power utilized in manufacturing operations. in 1900, however, 14,884 gas engines were reported, with a total of 143,850 horse-power, or 1.3 per cent of the total power used for manufacturing purposes. this increase from 8,930 horse-power to 143,850 horse-power, a gain of 134,920 horse-power, is proportionately the largest increase in any form of primary power shown by a comparison of the figures of the eleventh and twelfth censuses, amounting to 1,510.9 per cent. "within the past decade, and more particularly during the past five years, there has been a marked increase in the use of this power in industrial establishments for driving machinery, for generating electricity, and for other kindred uses. at the same time, internal-combustion engines have increased in popularity for uses apart from manufacturing, and the amount of this kind of power in use for all purposes in 1900 was, doubtless, very much larger than indicated by the figures relating to manufacturing plants alone. "the average horse-power per gas engine in 1900 was 9.7 horse-power. there are no available statistics upon which to base a comparison of this average with the average for 1890, but it is doubtful if there has been any very material change in ten years; for while gas engines are built in much larger sizes than ever before, there has been also a great increase in the number of small engines for various purposes. "the large increase in the use of internal-combustion engines has been due to the rapid improvements that have been made in them, their increased efficiency and economy, their decreased cost, and the wider range of adaptability that has been made practicable. "steam still continues to be preeminently the power of greatest importance, and the census returns indicate that the proportion of steam to the total of all powers has increased very largely in the past thirty years. in 1870 steam furnished 1,215,711 horse-power, or 51.8 per cent of a total of 2,346,142; in 1880 the amount of steam power used was 2,185,458 horse-power out of a total of 3,410,837, or 64.1 per cent; in 1890 out of an aggregate of 5,954,655 horse-power, 4,581,595, or 76.9 per cent was steam; while in 1900 steam figured to the extent of 8,742,416 horse-power, or 77.4 per cent, in a total of 11,300,081. this increase in thirty years, from 51.8 per cent to 77.4 per cent of the total power, shows how much more rapidly the use of steam power has increased than other primary sources of power. "the tendency toward larger units in the use of steam power is shown inadequately by the increase in the average horse-power per engine from 39 horse-power in 1880, to 51 horse-power in 1890, and 56 horse-power in 1900. "the tendency toward great operations which has been such a conspicuous feature of industrial progress during the past ten years, has shown itself strikingly in the use of units of larger capacity in nearly every form of machinery, and nowhere has this tendency been more marked than in the motive power by which the machinery is driven. at the same time there has been an increase in the use of small units, which tends to destroy the true tendency in steam engineering in these statistics. for example, a steam plant consisting of one or more units of several thousand horse-power may also embrace a number of small engines of only a few horse-power each, the use of which is necessitated by the magnitude of the plant, for the operation of mechanical stokers, the driving of draft fans, coal and ash conveyors, and other work requiring power in small units. on this account the average horse-power of steam engines in use at different census periods fails to afford a true basis for measuring progress toward larger units during the past ten years. "developments of the past few years in the distribution of power by the use of electric motors have served to accelerate the tendency toward larger steam units and the elimination of small engines in large plants and to change completely the conditions just described. for example: in one of the largest power plants in the world, which is now being installed, all the stokers, blowers, conveyors, and other auxiliary machinery are to be driven by electric motors. such rapidly changing conditions tend to invalidate any comparisons of statistical averages deduced from figures for periods even but a few years apart. "comparison of two important industries will illustrate the foregoing. the average horse-power of the steam engine used in the cotton mills of the united states in 1890 was 198, and in 1900 it was 300. "in the iron and steel industry the average horse-power per engine in 1890 was 171, and in 1900 it was 235. in the cotton mills the use of single large units of motive power, with few auxiliary engines of small capacity, gives the largest horse-power per engine of any industry; while in the iron and steel industry the average of the motive power proper, although probably larger than in the manufacture of cotton goods, is reduced by the large number of small engines which are used for auxiliary purposes in every iron and steel plant." it will be understood that the object of exploding the mixed gases in the oil engine is to produce sudden heating of the entire gas. there is no reason whatever for introducing the gasoline beyond this. could a better method of heating air be devised, the oil might be entirely dispensed with, and the safety of the apparatus enhanced, as well as the economy of operation. efforts have been made for fifty years to construct a hot-air engine that would compete with steam successfully. in the early fifties, as already noted, ericsson showed the feasibility of substituting hot air for steam, but although he constructed large engines, their power was so slight that he was obliged to give up the idea of competing with steam, and to use his engines for pumping where very small power was required. the great difficulty was that it was not found practicable to heat the air rapidly. all subsequent experimenters have met with the same difficulty until somewhat recently. it is now claimed, however, that a means has been found of rapidly heating the air, and it is even predicted that the hot-air engine will in due course entirely supersede the steam engine. mr. g. emil hesse, in an article in _the american inventor_, for april 15, 1905, describes a svea caloric engine as having successfully solved the problem of rapidly heating air. the methods consist in breaking up the air into thin layers and passing it over hot plates, where it rapidly absorbs heat. it passes from the heater to the power cylinder which resembles the cylinder of a steam engine; thence after expanding and doing its work it is exhausted into the atmosphere. large engines may use the same air over and over again under pressure of one hundred pounds per square inch, alternately heating and cooling it. a six horse-power engine of this type is said to have a cylinder four and one-half inches in diameter and a stroke of four and seven-eighth inches, and makes four hundred and fifty revolutions per minute. the heater is twenty inches in diameter, sixteen inches long, and has a heating surface of sixty square feet. the total weight of heater and engine complete is four hundred pounds for a half horse-power ericsson engine. "the svea heater," says mr. hesse, "absorbs the heat as perfectly as an ordinary steam boiler, and the heat-radiating surface of both heater and engine is not larger than that of a steam plant of the same power, thereby placing the two motors on the same basis, as far as the utilization of the heat in the fuel itself is concerned. "the advantage which every hot-air engine has over the steam engine is the amount of heat saved in the vaporization of the water. it is now well known that one gas is as efficient as another for the conversion of heat into power. air and steam at 100° c. are consequently on the same footing and ready to be superheated. the amount of heat required to bring the two gases to this temperature is, however, very different. "with an initial temperature of 10° c. for both air and water, we find that one kilogram of steam requires 90 + 537 = 627 thermal units, and one kilogram of air 0.24 × 90 = 21.6 thermal units. some heat is recovered if the feed water is heated and the steam condensed, but the difference is still so great as to altogether exclude steam as a competitor, provided air can be as readily handled. "having now the means to rapidly heat the air, the outlook for the external-combustion engine is certainly very promising. "the saving of more than half the coal now used by the steam engine will be of tremendous importance to the whole world." to what extent this optimistic prediction will be verified is a problem for the future to decide. viii the smallest workers in our studies of the steam engine and gas engine we have been concerned with workers of infinitesimal size. yet, if we are to believe the reports of the modern investigator, the molecules of steam or of ignited gas are small only in a relative sense, and there is a legion of workers compared with which the molecules are really gigantic in size. these workers are the atoms, and the yet more minute particles of which, according to the most recent theories, they are themselves composed. these smallest conceivable particles, the constituents of the atoms, are called electrons. they are a discovery of the physicists of the most recent generation. according to the newest theories they account for most--perhaps for all--of the inter-molecular and inter-atomic forces; they are indeed the ultimate repositories of those stores of energy which are known to be contained in all matter. the theories are not quite as fully developed as could be wished, but it would appear that these minutest particles, the electrons, are the essential constituents of the familiar yet wonderful carrier of energy which we term electricity. in considering the share of electricity in the world's work, therefore, we shall do well at the outset to put ourselves in touch with recent views as to the nature of this most remarkable of workers. on every side in this modern world we are confronted by this strange agent, electricity. the word stares us in the face on every printed page. the thing itself is manifest in all departments of our every-day life. you go to your business in an electric car; ascend to your office in an electric elevator; utilize electric call-bells; receive and transmit messages about the world and beneath the sea by electric telegraph. your doctor treats you with an electric battery. your dentist employs electric drills and electric furnaces. you ride in electric cabs; eat food cooked on electric stoves; and read with the aid of electric light. in a word, the manifestations of electricity are so obvious on every side that there can be no challenge to the phrasing which has christened this the age of electricity. but what, then, is this strange power that has produced all these multifarious results? it would be hard to propound a scientific query that has been more variously answered. ever since the first primitive man observed the strange effect produced by rubbing a piece of amber, thoughtful minds must have striven to explain that effect. ever since the eighteenth-century scientist began his more elaborate studies of electricity, theories in abundance have been propounded. and yet we are not quite sure that even the science of to-day can give a correct answer as to the nature of electricity. at the very least, however, it is able to give some interesting suggestions which seem to show that we are in a fair way to solve this world-old mystery. and, curiously enough, the very newest explanations are not so very far away from some eighteenth-century theories which for a long time were looked at askance if not altogether discarded. in particular, the theory of benjamin franklin, which considered electricity as an immaterial fluid bearing certain curious relations to tangible matter, is found to serve singularly well as an aid to the interpretation of the very newest experiments. franklin's one-fluid theory such being the case, we must consider this theory of franklin's somewhat in detail. perhaps we cannot do better than state the theory in the words of the celebrated physicist, dr. thomas young, as given in his work on natural philosophy, published in 1807. by quoting from this old work we shall make sure that we are not reading any modern interpretations into the theory. "it is supposed," says young, "that a peculiar ethereal fluid pervades the pores, if not the actual substance of the earth and of all other material bodies, passing through them with more or less facility, according to their different powers of conducting it; that particles of this fluid repel each other, and are attracted by particles of common matter; that particles of common matter also repel each other; and that these attractions and repulsions are equal among themselves, and vary inversely as to squares of the distances of the particles. the effects of this fluid are distinguished from those of all other substances by an attractive or repulsive quality, which it appears to communicate to different bodies, and which differs in general from other attractions and repulsions by its immediate diminution or cessation when the bodies, acting on each other, come into contact, or are touched by other bodies.... in general, a body is said to be electrified when it contains, either as a whole or in any of its parts, more or less of the electric fluid than is natural to it.... in this common neutral state of all bodies, the electrical fluid, which is everywhere present, is so distributed that the various forces hold each other exactly in equilibrium and the separate results are destroyed, unless we choose to consider gravitation itself as arising from a comparatively slight inequality between the electrical attractions and repulsions." the salient and striking feature of this theory, it will be observed, is that the electrical fluid, under normal conditions, is supposed to be incorporated everywhere with the substance of every material in the world. it will be observed that nothing whatever is postulated as to the nature or properties of this fluid beyond the fact that its particles repel each other and are attracted by the particles of common matter; it being also postulated that the particles of common matter likewise repel each other under normal conditions. at the time when franklin propounded his theory, there was a rival theory before the world, which has continued more or less popular ever since, and which is known as the two-fluid theory of electricity. according to this theory, there are two uncreated and indestructible fluids which produce electrical effects. one fluid may be called positive, the other negative. the particles of the positive fluid are mutually repellent, as also are the particles of the negative fluid, but, on the other hand, positive particles attract and are attracted by negative particles. we need not further elaborate the details of this two-fluid theory, because the best modern opinion considers it less satisfactory than franklin's one-fluid theory. meantime, it will be observed that the two theories have much in common; in particular they agree in the essential feature of postulating an invisible something which is not matter, and which has strange properties of attraction and repulsion. these properties of attraction and repulsion constituted in the early day the only known manifestations of electricity; and the same properties continue to hold an important place in modern studies of the subject. electricity is so named simply because amber--the latin _electrum_--was the substance which, in the experience of the ancients, showed most conspicuously the strange property of attracting small bodies after being rubbed. modern methods of developing electricity are extremely diversified, and most of them are quite unsuggestive of the rubbing of amber; yet nearly all the varied manifestations of electricity are reducible, in the last analysis, to attractions and repulsions among the particles of matter. as to the alleged immaterial fluids which, according to the theories just mentioned, make up the real substance of electricity, it was perfectly natural that they should be invented by the physicists of the elder day. all the conceptions of the human mind are developed through contact with the material world; and it is extremely difficult to get away, even in theory, from tangible realities. when the rubbed amber acquires the property of drawing the pith ball to it, we naturally assume that some change has taken place in the condition of the amber; and since the visible particles of amber appear to be unchanged--since its color, weight, and friability are unmodified--it seems as if some immaterial quality must have been added to, or taken from it. and it was natural for the eighteenth-century physicist to think of this immaterial something as a fluid, because he was accustomed to think of light, heat, and magnetism as being also immaterial fluids. he did not know, as we now do, that what we call heat is merely the manifestation of varying "modes" of motion among the particles of matter, and that what we call light is not a thing _sui generis_, but is merely our recognition of waves of certain length in the all-pervading ether. the wave theory of light had, indeed, been propounded here and there by a philosopher, but the theory which regarded light as a corpuscular emanation had the support of no less an authority than sir isaac newton, and he was a bold theorist that dared challenge it. when franklin propounded his theory of electricity, therefore, his assumption of the immaterial fluid was thoroughly in accord with the physical doctrines of the time. modern views but about the beginning of the nineteenth century the doctrine of imponderable fluids as applied to light and heat was actively challenged by young and fresnel and by count rumford and humphry davy and their followers, and in due course the new doctrines of light and heat were thoroughly established. in the light of the new knowledge, the theory of the electric fluid or fluids seemed, therefore, much less plausible. whereas the earlier physicists had merely disputed as to whether we must assume the existence of two electrical fluids or of only one, it now began to be questioned whether we need assume the existence of any electrical fluid whatever. the physicists of about the middle of the nineteenth century developed the wonderful doctrine of conservation of energy, according to which one form of force may be transformed into another, but without the possibility of adding to, or subtracting from, the original sum total of energy in the universe. it became evident that electrical force must conform to this law. finally, clerk-maxwell developed his wonderful electromagnetic theory, according to which waves of light are of electrical origin. the work of maxwell was followed up by the german hertz, whose experiments produced those electromagnetic waves which, differing in no respect except in their length from the waves of light, have become familiar to everyone through their use in wireless telegraphy. all these experiments showed a close relation between electrical phenomena, and the phenomena of light and of radiant heat, and a long step seemed to be taken toward the explanation of the nature of electricity. the new studies associated electricity with the ether, rather than with the material substance of the electrified body. many experiments seemed to show that electricity in motion traverses chiefly the surface of the conductor, and it came to be believed that the essential feature of the "current" consists of a condition of strain or stress in the ether surrounding a conductor, rather than of any change in the conductor itself. this idea, which is still considered valid, has the merit of doing away with the thought of action at a distance--the idea that was so repugnant to the mind of faraday. so far so good. but what determines the ether strain? there is surely _something_ that is not matter and is not ether. what is this something? the efforts of many of the most distinguished experimenters have in recent years been directed toward the solution of that question; and these efforts, thanks to the new methods and new discoveries, have met with a considerable measure of success. i must not attempt here to follow out the channels of discovery, but must content myself with stating briefly the results. we shall have occasion to consider some further details as to the methods in a later chapter. briefly, then, it is now generally accepted, at least as a working hypothesis, that every atom of matter--be it oxygen, hydrogen, gold, iron, or what not--carries a charge of electricity, which is probably responsible for all the phenomena that the atom manifests. this charge of electricity may be positive or negative, or it may be neutral, by which is meant that the positive and negative charges may just balance. if the positive charge has definite carriers, these are unknown except in association with the atom itself; but the negative charge, on the other hand, is carried by minute particles to which the name electron (or corpuscle) has been given, each of which is about one thousand times smaller than a hydrogen atom, and each of which carries uniformly a unit charge of negative electricity. electrons are combined, in what may be called planetary systems, in the substance of the atom; indeed, it is not certain that the atom consists of anything else but such combinations of electrons, held together by the inscrutable force of positive electricity. some, at least, of the electrons within the atom are violently active--perhaps whirling in planetary orbits,--and from time to time one or more electrons may escape from the atomic system. in thus escaping an electron takes away its charge of negative electricity, and the previously neutral atom becomes positively electrified. meanwhile the free electron may hurtle about with its charge of negative electricity, or may combine with some neutral atom and thus give to that neutral atom a negative charge. under certain conditions myriads of these electrons, escaped thus from their atomic systems, may exist in the free state. for example, the so-called _beta_ (ß) rays of radium and its allies consist of such electrons, which are being hurtled off into space with approximately the speed of light. the cathode rays, of which we have heard so much in recent years, also consist of free electrons. but, for that matter, all currents of electricity whatever, according to this newest theory, consist simply of aggregations of free electrons. according to theory, if the electrons are in uniform motion they produce the phenomena of constant currents of electricity; if they move non-uniformly they produce electromagnetic phenomena (for example, the waves used in wireless telegraphy); if they move with periodic motion they produce the waves of light. meanwhile stationary aggregations of electrons produce the so-called electrostatic phenomena. all the various ether waves are thus believed to be produced by changes in the motions of the electrons. a very sudden stoppage, such as is produced when the cathode ray meets an impassable barrier, produces the x-ray. with these explanations in mind, it will be obvious how closely this newest interpretation of electricity corresponds in its general features with the old one-fluid theory of franklin. the efforts of the present-day physicist have resulted essentially in an analysis of franklin's fluid, which gives to this fluid an atomic structure. the new theory takes a step beyond the old in suggesting the idea that the same particles which make up the electric fluid enter also into the composition--perhaps are the sole physical constituents--of every material substance as well. but while the new theory thus extends the bounds of our vision, we must not claim that it fully solves the mystery. we can visualize the ultimate constituent of electricity as an electron one thousand times smaller than the hydrogen atom, which has mass and inertia, and which possesses powers of attraction and repulsion. but as to the actual nature of this ultimate particle we are still in the dark. there are, however, some interesting theories as to its character, which should claim at least incidental attention. we have all along spoken of the electron as an exceedingly minute particle, stating indeed, that in actual size it is believed to be about one thousand times smaller than the hydrogen atom, which hitherto had been considered the smallest thing known to science. but we have now to offer a seemingly paradoxical modification of this statement. it is true that in _mass_ or weight the electron is a thousand times smaller than the hydrogen atom, yet at the same time it may be conceived that the limits of space which the electron occupies are indefinitely large. in a word, it is conceived (by professor j. j. thomson, who is the chief path-breaker in this field) that the electron is in reality a sort of infinitesimal magnet, having two poles joined by lines or tubes of magnetic force (the so-called faraday tube), which lines or tubes are of indefinite number and extent; precisely as, on a large scale, our terrestrial globe is such a magnet supplied with such an indefinite magnetic field. that the mass of the electron is so infinitesimally small is explained on the assumption that this mass is due to a certain amount of universal ether which is bound up with the tubes where they are thickest; close to the point in space from which they radiate, which point in space constitutes the focus of the tangible electron. it will require some close thinking on the part of the reader to gain a clear mental picture of this conception of the electron; but the result is worth the effort. when you can clearly conceive all matter as composed of electrons, each one of which cobwebs space with its system of magnetic tubes, you will at least have a tangible picture in mind of a possible explanation of the forces of cohesion and gravitation--in fact, of all the observed cases of seeming action at a distance. if at first blush the conception of space as filled with an interminable meshwork of lines of force seems to involve us in a hopeless mental tangle, it should be recalled that the existence of an infinity of such magnetic lines joining the poles of the earth may be demonstrated at any time by the observation of a compass, yet that these do not in any way interfere with the play of other familiar forces. there is nothing unthinkable, then, in the supposition that there are myriads of minor magnetic centres exerting lesser degrees of force throughout the same space. all that can be suggested as to the actual nature of the faraday tubes is that they perhaps represent a condition of the ether. this, obviously, is heaping hypothesis upon hypothesis. yet it should be understood that the hypothesis of the magnetic electron as the basis of matter, has received an amount of experimental support that has raised it at least to the level of a working theory. should that theory be demonstrated to be true, we shall apparently be forced to conclude not merely that electricity is present everywhere in nature, but that, in the last analysis, there is absolutely no tangible thing other than electricity in all the universe. how electricity is developed turning from this very startling theoretical conclusion to the practicalities, let us inquire how electricity--which apparently exists, as it were, in embryo everywhere--can be made manifest. in so doing we shall discover that there are varying types of electricity, yet that these have a singular uniformity as to their essential properties. as usually divided--and the classification answers particularly well from the standpoint of the worker--electricity is spoken of as either statical or dynamical. the words themselves are suggestive of the essential difference between the two types. statical electricity produces very striking manifestations. we have already spoken of it as theoretically due to the conditions of the electrons at rest. it must be understood, however, that the statical electricity will, if given opportunity, seek to escape from any given location to another location, under certain conditions, somewhat as water which is stored up in a reservoir will, when opportunity offers, flow down to a lower level. the pent-up static electricity has, like the water in the reservoir, a store of potential energy. the physicist speaks of it as having high tension. in passing to a condition of lower tension, the statical electricity may give up a large portion of its energy. if, for example, on a winter day in a cold climate, you walk briskly along a wool carpet, the friction of your feet with the carpet generates a store of statical electricity, which immediately passes over the entire surface of your body. if now you touch another person or a metal conductor, such as a steam radiator or a gas pipe, a brilliant spark jumps from your finger, and you experience what is spoken of as an electrical shock. if the day is very cold, and the air consequently very dry, and if you will take pains to rub your feet vigorously or slide along the carpet, you may light a gas jet with the spark which will spring from your finger to the tip of the jet, provided the latter is of metal or other conducting substance; and even if you attempt to avoid the friction between your feet and the carpet as much as possible, you may be constantly annoyed by receiving a shock whenever you touch any conductor, since, in spite of your efforts, the necessary amount of friction sufficed to generate a store of statical electricity. an illustration of the development of this same form of electricity, on a large scale, is supplied by the familiar statical machine, which consists of a large circle of glass, so adjusted that it may be revolved rapidly against a suitable friction producer. with such a machine a powerful statical current is produced, capable of generating a spark that may be many inches or even several feet in length,--a veritable flash of lightning. it is with such a supply of electricity conducted through a vacuum tube that the cathode ray and the roentgen ray are produced. such effects as this suggest considerable capacity for doing work. yet in reality, notwithstanding the very sporadical character of the result, the quantity of electricity involved in such a statical current may be very slight indeed. even a lightning flash is held to represent a comparatively small amount of electricity. faraday calculated that the amount of electricity that could be generated from a single drop of water, through chemical manipulation, would suffice to supply the lightning for a fair-sized thunder-storm. nevertheless the destructive work that may be done by a flash of lightning may be considerable, as everyone is aware. but, on the other hand, while the visible effect of a stroke of lightning on a tree trunk, for example, makes it seem a powerful agency, yet the actual capacity to do work--the power to move considerable masses of matter--is extremely limited. the effect on a tree trunk, it will be recalled, usually consists of nothing more than the stripping off of a channel of bark. in other words, the working energy contained in a seemingly powerful supply of statical electricity commonly plays but an insignificant part. the working agent, and therefore the form of electricity which concerns us in the present connection, is the dynamical current. this may be generated in various ways, but in practice these are chiefly reducible to two. one of these depends upon chemical action, the other upon the inter-relations of mechanical motion and magnetic lines of force. a common illustration of the former is supplied by the familiar voltaic or galvanic battery. the electromagnetic form has been rendered even more familiar in recent times by the dynamo. this newest and most powerful of workers will claim our attention in detail in the succeeding chapter. our present consideration will be directed to the older method of generating the electric current as represented by the voltaic cell. the work of the dynamical current let us draw our illustration from a familiar source. even should your household otherwise lack electrical appliances, you are sure to have an electric call-bell. the generator of the electric current, which is stored away in some out-of-the-way corner, is probably a small so-called "dry-cell" which you could readily carry around in your pocket; or it may consist of a receptacle holding a pint or two of liquid in which some metal plates are immersed. such an apparatus seems scarcely more than a toy when we contrast it with the gigantic dynamos of the power-house; yet, within the limits of its capacities, one is as surely a generator of electricity as the other. if we are to accept the latest theory, the electrical current which flows from this tiny cell is precisely the same in kind as that which flows from the five-thousand-horse-power dynamo. the difference is only one of quantity. to understand the operation of this common household appliance we must bear in mind two or three familiar experimental facts in reference to the action of the voltaic cell. briefly, such a cell consists of two plates of metal--for example, one of copper and the other of zinc--with a connecting medium, which is usually a liquid, but which may be a piece of moistened cloth or blotting-paper. so long as the two plates of metal are not otherwise connected there is no electricity in evidence, but when the two are joined by any metal conductor, as, for example, a piece of wire--thus, in common parlance, "completing the circuit"--a current of electricity flows about this circuit, passing from the first metal plate to the second, through the liquid and back from the second plate to the first through the piece of wire. the wire may be of any length. in the case of your call-bell, for example, the wire circuit extends to your door, and is there broken, shutting off the current. when you press the button you connect the broken ends of the wire, thus closing the circuit, as the saying is, and the re-established current, acting through a little electromagnet, rings the bell. in another case, the wire may be hundreds of miles in length, to serve the purposes of the telegrapher, who transmits his message by opening and closing the circuit, precisely as you operate your door-bell. for long-distance telegraphy, of course, large cells are required, and numbers of them are linked together to give a cumulative effect, making a strong current; but there is no new principle involved. the simplest study of this interesting mechanism makes it clear that the cell is the apparatus primarily involved in generating the electric current; yet it is equally obvious that the connecting wire plays an important part, since, as we have seen, when the wire is broken there is no current in evidence. now, according to the electron theory, as previously outlined, the electric current consists of an actual flow along the wire of carriers of electricity which are unable to make their way except where a course is provided for them by what is called a conductor. dry air, for example, is, under ordinary circumstances, quite impervious to them. this means, then, that the electrons flow freely along the wire when it is continuous, but that they are powerless to proceed when the wire is cut. when you push the button of your call-bell, therefore, you are virtually closing the switch which enables the electrons to proceed on their interrupted journey. theories of electrical action but all this, of course, leaves quite untouched the question of the origin of the electrons themselves. that these go hurtling from one plate or pole of the battery to the other, along the wire, we can understand at least as a working theory; that, furthermore, the electrons have their origin either in the metal plates or in the liquid that connects them, seems equally obvious; but how shall we account for their development? it is here that the chemist with his atomic theory of matter comes to our aid. he assures us that all matter consists in the last analysis of excessively minute particles, and that these particles are perpetually in motion. they unite with one another to form so-called molecules, but they are perpetually breaking away from such unions, even though they re-establish them again. such activities of the atoms take place even in solids, but they are greatly enhanced when any substance passes from the solid into the liquid state. when, for example, a lump of salt is dissolved in water, the atoms of sodium and of chlorine which joined together make up the molecules of salt are held in much looser bondage than they were while the salt was in a dry or crystalline form. could we magnify the infinitesimal particles sufficiently to make them visible we should probably see large numbers of the molecules being dissociated, the liberated atoms moving about freely for an instant and then reuniting with other atoms. thus at any given instant our solution of salt would contain numerous free _atoms_ of sodium and of chlorine, although we are justified in thinking of this substance as a whole as composed of sodium-chlorine _molecules_. it is only by thus visualizing the activity of the atoms in a solution that we are able to provide even a thinkable hypothesis as to the development of electricity in the voltaic cell. what puts us on the track of the explanation we are seeking is the fact that the diverse atoms are known to have different electrical properties. in our voltaic cell, for example, sodium atoms would collect at one pole and chlorine atoms at the other. humphry davy discovered this fact in the early days of electro-chemistry, just about a century ago. he spoke of the sodium atom as electro-positive, and of the chlorine atom as electro-negative, and he attempted to explain all chemical affinity as merely due to the mutual attraction between positively and negatively electrified atoms. the modern theorist goes one step farther, and explains the negative properties of the chlorine atom by assuming the presence of one negative electron or electricity in excess of the neutralizing charge. the assumption is, that the sodium atom has lost this negative electron and thus has become positively electrified. the chlorine atom, harboring the fugitive electron, becomes negatively electrified. hence the two atoms are attracted toward opposite poles of the cell. this disunion of atoms, be it understood, must be supposed to take place in the case of any solution of common salt, whether it rests in an ordinary cup or forms a part of the ocean. here we have, then, material for the generation of the electrical current, if some means could be found to induce the chlorine atom to give up the surplus electron which from time to time it carries. and this means is provided when two pieces of metal of different kinds, united with a metal conductor, are immersed in the liquid. then it comes to pass that the electrons associated with the chlorine atoms that chance to lie in contact with one of these plates of metal, find in this metal an avenue of escape. they rush off eagerly along the metal and the connecting wire, and in so doing establish a current which acts--if we may venture a graphic analogy from an allied field of physics--as a sort of suction, attracting other chlorine atoms from the body of the liquid against the metal plate that they also may discharge their electrons. in other words, the electrical current passes through the liquid as well as through the outside wire, thus completing the circuit. according to this theory, then, the electrical energy in evidence in the current from the voltaic cell, is drawn from a store of potential energy in the atoms of matter composing the liquid in the cell. in practice, as is well known, the liquid used is one that affects one of the metal poles more actively than the other, insuring vigorous chemical activity. but the principle of atomic and electrical dissociation just outlined is the one involved, according to theory, in every voltaic cell, whatever the particular combination of metals and liquids of which it is composed. it should be added, however, that while we are thus supplied with a thinkable explanation of the origin of this manifestation of electrical energy, no explanation is forthcoming, here any more than in the case of the dynamo, as to why the electrons rush off in a particular direction and thus establish an electrical current. perhaps we should recall that the very existence of this current has at times been doubted. quite recently, indeed, it has been held that the seeming current consists merely of a condition of strain or displacement of the ether. but we are here chiefly concerned with the electron theory, according to which, as we have all along noted, the seeming current is an actual current; the ether strain, if such exists, being due to the passage of the electrons. practical uses of electricity various effects of the current of electrons have been hinted at above. considered in detail, the possible ways in which these currents may be utilized are multifarious. yet, they may be all roughly classified into three divisions as follows: first, cases in which the current of electricity is used to transmit energy from one place to another, and reproduce it in the form of molar motion. the dynamo, in its endless applications, illustrates one phase of such transportation of energy; and the call-bell, the telegraph, and the telephone represent another phase. in one case a relatively large quantity of electricity is necessary, in the other case a small quantity; but the principle involved--that of electric and magnetic induction--is the same in each. the second method is that in which the current, generated by either a dynamo or a battery of voltaic cells, is made to encounter a relatively resistant medium in the course of its flow along the conducting circuit. such resistance leads to the production of active vibrations among the particles of the resisting medium, producing the phenomena of heat and, if the activity is sufficient, the phenomena of light also. it will thus appear that in this class of cases, as in the other, there is an actual re-transformation of electrical energy into the energy of motion, only in this case the motion is that of molecules and not of larger bodies. the principle is utilized in the electrical heater, with which our electric street-cars are commonly provided, and which is making its way in the household for purposes of general heating and of cooking. it is utilized also in various factories, where the very high degree of heat attainable with the electrical furnace is employed to produce chemical dissociation and facilitate chemical combinations. by this means, for example, a compound of carbon and silicon, which is said to be the hardest known substance, except the diamond, is produced in commercial quantities. a familiar household illustration of the use of this principle is furnished by the electric light. the carbon filament in the electric bulb furnishes such resistance to the electric current that its particles are set violently aquiver. under ordinary conditions the oxygen of the air would immediately unite with the carbon particles, volatilizing them, and thus instantly destroying the filament; but the vacuum bulb excludes the air, and thus gives relative permanency to the fragile thread. the third class of cases in which the electric current is commercially utilized is that in which the transformations it effects are produced in solutions comparable to those of the voltaic cell, the principles involved being those pointed out in the earlier part of the present chapter. by this means a metal may be deposited in a pure state upon the surface of another metal made to act as a pole to the battery; as, for example, when forks, spoons, and other utensils of cheap metals are placed in a solution of a silver compound, and thus electroplated with silver. to produce the powerful effects necessary in the various commercial applications of this principle, the poles of the voltaic cell--which cell may become in practice a large tank--are connected with the current supplied by a dynamo. various chemical plants at niagara utilize portions of the currents from the great generators there in this way. another familiar illustration of the principle is furnished by the copper electroplates from which most modern books are printed. it appears, then, that all the multifarious uses of electricity in modern life are reducible to a few simple principles of action, just as electricity itself is reduced, according to the analysis of the modern physicist, to the activities of the elementary electron. there is nothing anomalous in this, however, for in the last analysis the mechanical principles involved in doing all the world's work are few and relatively simple, however ingenious and relatively complex may be the appliances through which these principles are made available. ix man's newest co-laborer: the dynamo as you stand waiting for your train at elevated or subway station you must have noticed the third rail. to outward appearance it is not different from the other rails. it seems a mere inert piece of steel. yet you are well aware that a strange power abides there unseen--a power that pulls the train, and that lurks in hiding to strike a death-blow to any chance unfortunate whose foot or hand comes in contact with the rail. as the heavy train dashes up, dragged by this unseen power, probably you, in common with the rest of the world, have been led to remark, "is it not marvelous?" marvelous it surely seems. yet the cause of our astonishment is to be sought in the relative newness of the phenomena rather than in the nature of the phenomena themselves. at first glance it may seem that the intangible character of the electrical power gives it a unique claim on our wonderment. but a moment's reflection dispels this illusion. after all, electricity is no more intangible than heat. neither the one nor the other can be seen or heard, but each alike may be felt. yet we observe without astonishment a locomotive propelled by the power of heat--simply because the locomotive has become an old story. again, electricity is far less intangible than gravitation. not merely may electricity be felt, but it may be generated through transformation of other forms of energy; it may be stored away and measured; may be conducted at will through tortuous channels, or obstructed in its flight by the intervention of non-conductors. but gravitation submits to no such restrictions. it eludes all of our senses, and it absolutely disregards all barriers. to its catholic taste all substances are alike. it holds in bondage every particle of matter in the universe, and can enforce its influence over every kind of atom with an impartiality that is as astounding as it is inexorable. moreover, this weird force, gravitation, has thus far evaded all man's efforts to classify or label it. no man has the slightest inkling as to what gravitation really is. if, as you glance at these lines, you should chance to release your hold and allow the volume to drop to the floor, you will have performed a miracle which no scientist in the world can even vaguely explain. as regards our electric train, then, the fact that it stands there firmly, held fast to the rails by gravitation, is in reality as great and as inexplicable a marvel as the fact that the electric current gives it propulsion. not only so, but the fact that the train goes forward of its own inertia, as we say, for a time after the current is shut off, presents to us yet another inexplicable marvel. it is a fundamental property of matter, we say, when once in motion to continue in motion until stopped by some counter-force; but that phrasing, expressive though it be of a fact upon which so many physical phenomena depend, is in no proper sense of the word an explanation. once for all, then, there is nothing unique, nothing preternaturally marvelous, about the phenomena of electricity. and indeed, it is interesting to note how quickly we become accustomed to these phenomena, and how little wonder they excite so soon as they cease to be novel. even imaginative people have long since ceased to give thought to the trolley car; and within a week of the opening of new york's subway the average man came to regard it as much as a matter of course as if he had been accustomed to it from boyhood. and yet, in another sense of the word, the electric motor is a wonderful contrivance. as an example of what man's ingenuity can accomplish toward transforming the powers of nature and adapting them to his own use, it is fully entitled to be called a marvel. moreover, in the last analysis, we are as helpless to explain the nature of electricity as we are to explain the nature of gravitation. it is only the proximal phenomena of the electric current that can be explained. these phenomena, however, are full of interest. let us examine them somewhat in detail, allowing them to lead us back from electric train to power-house and dynamo, and from dynamo as far toward the mystery of electric energy as present-day science can guide us. the mechanism of the dynamo if we could look into the interior of a mechanism in connection with the trucks beneath the car, we should find an apparatus consisting essentially of coils of wire adjusted compactly about an axis, and closely fitted between the poles of a powerful electromagnet. these coils of wire constitute what is called an armature. when the current is switched on it passes through this armature, as well as through the electromagnet, and the mutual attractions and repulsions between the magnetic poles and the electric current in the coils of wire, cause the armature to revolve with such tremendous energy as to move the train--the motion of its axis being transmitted to the axle of the car-wheels by a simple gearing. all this is simple enough if we regard only the _how_ and not the _why_ of the phenomena. ignoring the _why_ for the moment, let us seek the origin of the current which, by being conducted through the armature, has produced the striking effect we have just witnessed. this current reaches the car through an overhead or underground wire. all that is essential is that some conducting medium, such as an iron rail, or a copper wire, shall form an unbroken connection between the motor apparatus and the central dynamo where the power is generated--the return circuit being made either by another wire or by the ordinary rails. the central dynamo in question will be found, if we visit the power-house, to be a ponderous affair, suggestive to the untechnical mind of impenetrable mysteries. yet in reality it is a device essentially the same in construction as the motor which drives the train. that is to say, its unit of construction consists of a wire-wound armature revolving on an axis and fitted between the poles of an electromagnet. here, however, the sequence of phenomena is reversed, for the armature, instead of receiving a current of electricity, is made to revolve by a belt adjusted to its axis and driven by a steam engine. the wire coils of the armature thus made to revolve cut across the so-called lines of magnetic force which connect the two poles of the magnet, and in so doing generate a current of induced electricity, which flows away to reach in due course the third rail or the trolley-wire, and ultimately to propel the motor. [illustration: lower figure copyrighted by n. y. edison co. an electric train and the dynamo that propels it. the lower figure gives an interior view of a power house of the manhattan elevated railway company. the upper figure shows one of the electric engines operating on the new york central lines just outside of new york. the power is conveyed to the engine by a third rail clearly shown in the picture.] it is hardly necessary to state that in actual practice this generating dynamo is a complex structure. the armature is a complex series of coils of wire; the electromagnets surrounding the armature are several or many; and there is an elaborate system of so-called commutators through which the currents of electricity--which would otherwise oscillate as the revolving coil cuts the lines of magnetic force in opposite directions--are made to flow in one direction. but details aside, the foundation facts upon which everything depends are (1) that a coil of wire when forced to move so that it cuts across the lines of force in any magnetic field develops a so-called induced current of electricity; and (2) that such an induced current possesses power of magnetic attraction and repulsion. these facts were discovered more than sixty years ago, and carefully studied by michael faraday, joseph henry, and others. faraday found that such an induced current could be produced not merely with the aid of an iron magnet, but even by causing a wire to cut the lines of force that everywhere connect the north and south poles of the earth,--the earth being indeed, as william gilbert long ago demonstrated, veritably a gigantic magnet. moreover, these relations are reciprocal; so that if a wire through which a current of electricity is passing is placed across a magnetic field, the wire is impelled to move in a plane at right angles to the direction of the lines of force. it is forcibly thrust aside. this side-thrust acting on coils of wire is what produces the revolution of the armature of the electric motor. the origin of the dynamo the very first studies that had to do with the mutual relations of electricity and magnetism were made by hans christian oersted, the dane, as early as 1815. he discovered that a magnetic needle is influenced by the passage near it of a current of electricity, demonstrating, therefore, that the electric current in some way invades the medium surrounding any conductor along which it is passing. oersted's experiments were repeated, and some new phenomena observed by the frenchman andré marie ampère and dominique françois arago. arago constructed an interesting device, in which a metal disk was made to revolve in the presence of a current of electricity; but neither he nor anyone else at the time was able to explain the phenomenon. in 1824 an advance was made through the construction of the first electric magnet by sturgeon. hitherto it had not been known that a magnet could be made artificially, except by contact with a previously existing magnet. sturgeon showed that any core of iron may be rendered magnetic if wound with a conducting wire, through which a current of electricity is passed. the experiments thus inaugurated were followed up in america by joseph henry of albany who made enormous electromagnets, capable of sustaining great weights. one of his magnets, operated by a single cell, was able to lift six hundred and fifty pounds of metal. it was this apparatus which was subsequently to make possible the utilization of electricity as a working force, but as yet no one suspected its possibilities in this direction. it remained for michael faraday, in 1831, to make the final experiment which laid the secure foundation for the new science of electrodynamics. faraday constructed a tiny apparatus, consisting of a magnet between the poles of which a metal disk was placed in such a way that it could revolve on an axis, the disk being connected with a wire conveying an electric current. the details as to this most ingenious mechanism need not be given here. suffice it that faraday demonstrated the interrelations of magnetism and electricity and the possibility of causing a metal disk to revolve through this mutual interaction. in so doing he constructed the first dynamo-electric machine. in his hands it was a mere laboratory toy, but the principles involved were fully elaborated by the original experimenter, and stated in precise language which modern investigators have not been able to improve upon. several decades elapsed after faraday's initial experiment before the phenomena of magneto-electricity were proved to have any considerable commercial significance. a vast amount of ingenuity was required to devise a mechanism which could advantageously utilize the principle in question for commercial purposes. indeed the early experimenters did not at once get upon the right track, as their efforts were influenced disadvantageously by an attempt to follow the principle of the steam engine. some interesting mechanisms were devised whereby the motion of an armature in being drawn toward an electromagnet could be translated into rotary motion through the use of crank-shafts and even of beams, precisely comparable to those employed in the steam engine. such devices worked with a comparatively low degree of efficiency and were totally abandoned so soon as the idea of getting rotary motion directly from the magnet or armature was made feasible. the names of saxton, clarke, woolrich, wheatstone, and werner siemens are intimately connected with the early efforts at utilization of magneto-electric power. the shuttle-wound armature of siemens, invented in 1854, marked an important progressive step. perfecting the dynamo the first separately excited dynamos were constructed by dr. henry wilde, f.r.s., between 1863 and 1865, and this invention paved the way for rapid progress. in 1866-7 varley, siemens, wheatstone, and ladd constructed machines with several iron electromagnets, self-excited, which were described as dynamo-electric machines, a term afterward contracted to dynamos. in 1867 dr. wilde improved the armature by introducing several coils arranged around a cylinder; the current from a few of the coils was rectified and used to excite the field magnet, while the main current as given off by the rest of the coils was taken off by ring-contacts, the machine being a self-exciting, alternating-current dynamo. [illustration: wilde's separately excited dynamo. dr. wilde invented and patented (1863-5) the first separately excited dynamo, with which he demonstrated that the feeble current from a small magneto-electric machine would, by the expenditure of mechanical power, produce currents of great strength from a large dynamo.] the italian, picnotti, in 1864 invented a ring armature which, although provided with teeth was wound with coils in such a way as to obtain a very uniform current; but the practical introduction of the continuous-current machines dates from 1870, when gramme re-invented the ring and gave it the form which is still in vogue. von alteneck in 1873 converted the siemens shuttle armature along the same lines and so introduced the drum arrangement which has since been very extensively adopted. thus through the efforts of a great number of workers the idea of utilizing electromagnetic energy for the purposes of the practical worker came to be a reality. numberless machines have been made differing only as to details that need not detain us here. everyone is familiar with sundry applications of the dynamo to the purposes of to-day's applied science. it must be understood, of course, that the amount of electricity generated in any dynamo is precisely measurable, and that by no possibility could the energy thus developed exceed the energy required to move the coils of wire. were it otherwise the great law of the conservation of energy would be overthrown. in actual practice, of course, there is loss of energy in the transaction. the current of electricity that flows from the very best dynamo represents considerably less working power than is expended by the steam engine in forcibly revolving the armature. in the early days of experiments the loss was so great as to be commercially prohibitive. with the perfected modern dynamo the loss is not greater than fifteen per cent; but even this, it will be noted, makes electricity a relatively expensive power as compared with steam,--except, indeed, where some natural power, like the falls of niagara, can be utilized to drive the armature. a mysterious mechanism the efficiency of the modern dynamo is due largely to the fact that when the poles of the magnet are made to face each other, the lines of magnetic force passing between these poles are concentrated into a narrow compass. with the ordinary bar magnet, as everyone is aware, these lines of force circle out in every direction from the poles in an almost infinite number of loops, all converging at the poles, and becoming relatively separated at the equator in a manner which may be graphically illustrated by the lines of longitude drawn on an ordinary globe. it is obvious that with a magnet of such construction only a small proportion of the lines of magnetic force could be utilized in generating electricity. but, as already mentioned, when the magnet is so curved that its poles face each other, the lines of force, instead of widely diverging, pass from pole to pole almost in a direct stream. the strength of this magnetic stream may be increased almost indefinitely by winding the iron core of the magnet with the coil of wire through which the electric current is passed, thus constituting the electromagnet which has replaced the old permanent magnet in all modern commercial dynamos. [illustration: the evolution of the dynamo. fig. 1.--a small example of the original commercial form of the drum armature machine, patented in 1873 by dr. werner siemens and f. von hefner alteneck. the armature is a development of the siemens shuttle form of 1856, and gives a nearly continuous current. fig. 2.--an early experimental dynamo. fig. 3.--ferranti's original dynamo, patented in 1882-1883. the field magnets are stationary and consist of two sets of electro-magnets each with 16 projecting pull pieces, between which the armature revolves. fig. 4.--the gigantic rotary converters of the manhattan elevated railway.] an electromagnet may be sufficiently powerful to lift tons of iron. the force it exerts, therefore, is very tangible in its results. yet it seems mysterious, because so many substances are unaffected by it. you may place your head, for example, between the poles of the most powerful magnet without experiencing any sensation or being in any obvious way affected. you may wave your hand across the lines of force as freely as you may wave it anywhere else in space. apparently nothing is there. but were you to attempt to pass a dumb-bell or a bar of iron across the same space, the unseen magnetic force would wrench it from your grasp with a power so irresistible as to be awe-inspiring. similarly, the armature, when its coils of wire are adjusted between the poles of the magnet, is held in a vise-like grip by the invisible but potent lines of magnetic force which tend to make it revolve. it requires a tremendous expenditure of energy--supplied by the steam-engine or by water power--to enable the coiled wires of the generating armature to stem the current of magnetic force, which is virtually what is done when the armature revolves in such a way as to produce electrical energy. part of the mechanical energy thus expended is transformed into heat and dissipated into space; but the main portion is carried off, as we have seen, through the coiled wires of the armature in the form of what we term the current of electricity, to be re-transformed in due course into the mechanical energy that moves the car. it appears, then, that the phenomena of the electric dynamo depend upon the curious relations that exist between magnetism and electricity. granted the essential facts of magneto-electric induction, all the phenomena of the dynamo are explicable. but how explain these facts themselves? why is an electric current generated in a coil of wire moving in a magnetic field? and why is a wire carrying a current of electricity, when placed across a magnetic field, impelled to move at right angles to the lines of magnetic force? no thoughtful person can consider the subject without asking these questions. but as yet no definitive answer is forthcoming. some suggestive half-explanations, based on an assumed condition of torsion or strain in the ether, have been attempted, but they can hardly be called more than scientific guesses. meanwhile, it may be understood that the mutual relations of the magnetic and electrical forces just referred to are not at all dependent upon the manner in which the electric current is generated. the magneto-electric motor may be operated as well with a chemical battery as with such a mechanical generating dynamo as has just been described. the storage-batteries which have been employed in some street railways and those which propel the electric cabs about our city streets furnish cases in point. the only reason these are not more generally employed is that the storage battery has not yet been perfected so that it can produce a large supply of electricity in proportion to its weight, and produce it economically. x niagara in harness "harnessing niagara"--the phrase has been a commonplace for a generation; but until very recently indeed it was nothing more than a phrase. almost since the time when the falls were first viewed by a white man the idea of utilizing their powers has been dreamed of. but until our own day--until the last decade--science had not shown a way in which the great current could be economically shackled. a few puny mill-wheels have indeed revolved for thirty years or so, but these were of no greater significance than the thousands of others driven by mountain streams or by the currents of ordinary rivers. but about a decade ago the engineering skill of the world was placed in commission, and to-day niagara is fairly in harness. if you have ever seen niagara--and who has not seen it?-you must have been struck with the metamorphosis that comes over the stream about half a mile above the falls. above this point the river flows with a smooth sluggish current. only fifteen feet have the waters sunk in their placid flowing since they left lake erie. but now in the course of half a mile they are pitched down more than two hundred feet. if you follow the stream toward this decline you shall see it undergo a marvelous change. of a sudden the placid waters seem to feel the beckoning of a new impulse. caught with the witchery of a new motion, they go swirling ahead with unwonted lilt and plunge, calling out with ribald voices that come to the ear in an inchoate chorus of strident, high-pitched murmurings. each wavelet seems eager to hurry on to the full fruition of the cataract. it lashes with angry foam each chance obstruction, and gurgles its disapproval in ever-changing measures. even to the most thoughtless observer the mighty current thus unchained attests the sublimity of almost irresistible power. could a mighty mill-wheel be adjusted in that dizzy current, what labors might it not perform? five million tons of water rush down this decline each hour, we are told; and the force that thus goes to waste is as if three million unbridled horses exhausted their strength in ceaseless plunging. this estimate may be only a guess, but it matters not whether it be high or low; all estimates are futile, all comparisons inadequate to convey even a vague conception of the majesty of power with which the mighty waters rush on to their final plunge into the abysm. it is here, you might well suppose, where the appalling force of the current is made so tangible, that man would place the fetters of his harness, making the madcap current subject to his will. you will perhaps more than half expect to see gigantic mechanisms of man's construction built out over the rapids or across the face of the cataract--so much has been said of æstheticism versus commercialism in connection with the attempt to utilize niagara's power. but whatever your fears in this regard, they will not be realized. inspect the rapids and the falls as you may, you will see no evidence that man has tampered with their pristine freedom. subtler means have been employed to tame the wild steed. the mad waves that go dashing down the rapids are as free and untrammeled to-day as they were when the wild indian was the only witness of their tempestuous activity. such portions of the current as reach the rapids have full license to pass on untrammeled, paying no toll to man. the water which is made to pay tribute is drawn from the stream up there above the rapids, where it lies placid and as yet unstirred by the beckoning incline. to see niagara in harness, then, you must leave the cataract and the rapids and pass a full mile up the stream where the great river looks as calm as the hudson or the mississippi, and where, under ordinary conditions, not even the sound of the falls comes to your ear. prosaic enough it seems to observe here nothing more startling than a broad _cul de sac_ of stagnant water, like the beginning of a broad canal, extending in for a few hundred yards only from the main stream; its waters silent, currentless, seemingly impotent. this stagnant pool, then, not the whirling current below, is to furnish the water whose reserve force of energy of position is drawn upon to serve man's greedy purpose. coming from the rapids and cataract to this stagnant canal, you seem to step from the realm of poetic beauty to the sordid realities of the work-a-day world. of a truth it would seem that "harnessing niagara" is but a far-fetched metaphor. within the power-house and yet if you will turn aside from the canal and enter one of the long, low buildings that flank it on either side, you will soon be made to feel that the metaphor was amply justified. little as there was exteriorly to suggest it, you are entering a fairyland of applied science, and within these plain walls you shall witness evidences of the ingenuity of man that should appeal scarcely less to your imagination than the sight of the cataract itself in all its sublimity of power. for within these walls, by a miracle of modern science, the potential energy which resides in the water of the canal is transformed into an electrical current which is sent out over a network of wires to distant cities to perform a thousand necromantic tasks,--propelling a street car in one place, effecting chemical decompositions in another; turning the wheels of a factory here and lighting the streets of a city there; in short, subserving the practical needs of man in devious and wonderful ways. even as you gazed disdainfully at the stagnant canal, its waters, miraculously transformed, were propelling the trolley cars along the brink of the cliff over there on the canadian shore, and at the same time were turning the wheels in many a factory in the distant city of buffalo. after all, then, the quiet pool of water was not so prosaic as it seemed. as you stand in the building where this wonderful transformation of power is effected, the noble simplicity of the vista heightens the mystery. the most significant thing that strikes the eye is a row of great mushroom-like affairs, for all the world like giant tops, that stand spinning--and spinning. these great tops are about a dozen feet in diameter. they are whirling, so we are told, at a rate of two hundred and fifty revolutions per minute. hour after hour they spin on, never varying in speed, never faltering; day and night are alike to them, and one day is like another. they are as ceaselessly active, as unwearying as niagara itself, whose power they symbolize; and, like the great falls, they murmur exultingly as they work. [illustration: view in one of the power houses at niagara. each of the top-like dynamos generates 5000 horse-power.] the giant tops which thus seem to bid defiance to the laws of motion are in reality electric dynamos, no different in principle from the electric generators with which some visit to a street-car power-house has doubtless made you familiar. the anomalous feature of these dynamos--in addition to their size--is found in the fact that they revolve on a vertical shaft which extends down into a hole in the earth for more than a hundred feet, and at the other end of which is adjusted a gigantic turbine water-wheel. water from the canal is supplied this great turbine wheel through a steel tube or penstock, seven feet in diameter. as the turbine revolves under stress of this mighty column of water, the long shaft revolves with it, thus turning the electric generator at the other end of the shaft--the generator at which we are looking, and which we have likened to a giant top--without the interposition of any form of gearing whatever. to gain a vivid mental picture of the apparatus, we must take an elevator and descend to the lower regions where the turbine wheel is in operation. as we pass down and down, our eyes all the time fixed on the vertical revolving shaft, which is visible through a network of bars and gratings, it becomes increasingly obvious that to speak of this shaft as standing in "a hole in the ground" is to do the situation very scant justice. a much truer picture will be conceived if we think of the entire power-house as a monster building, about two hundred feet high, all but the top story being underground. what corresponds to the ground floor of the ordinary building is located one hundred and fifty feet below the earth's surface; and it is the top story which we entered from the street level, thus precisely reversing the ordinary conditions. penstocks and turbines as we descend now and reach at last the lowest floor of the building, we step out into a long narrow room, the main surface of which is taken up with a series of gigantic turnip-shaped mechanisms, each one having a revolving shaft at its axis; while from its side projects outward and then upward a seven-foot steel tube, for all the world like the funnel of a steamship. this seeming funnel--technically termed a penstock--is in reality the great tube through which the massive column of water finds access to the turbine wheel, which of course is incased within the turnip-shaped mechanism at its base. as you stand there beside this great steel mechanism a sense of wonderment and of utter helplessness takes possession of you. as you glance down the hall at this series of great water conduits, and strain your eyes upward in the endeavor to follow the great funnel to its very end, an oppressive sense of the irresistible weight of the great column of water it supports comes to you, and you can scarcely avoid a feeling of apprehension. suppose one of the great tubes were to burst?--we should all be drowned like rats in a hole. there is small danger, to be sure, of such a contingency; but it is well worth while to have stood thus away down here at the heart of the great power-house to have gained an awed sense of what man can accomplish toward rivaling the wonders of nature. to have stood an hour ago on the ice bridge at the foot of the most tremendous cataract in the world, where nature exhausts her powers amidst the mad rush and roar of seething waters; and now to stand beneath this other column of water which effects a no less wonderful transformation of energy, serenely, silently,--is to have run such a gamut of emotions as few other hours in all your life can have in store for you. a miraculous transformation of energy there are eleven of these great turbine mechanisms, each with a supplying funnel of water and a revolving shaft extending upward to its companion dynamo, in the room in which we stand. energy representing fifty-five thousand horse-power is incessantly transformed and made available for man's use in the subterranean building in which we stand. and there is not a pound of coal, not a lick of flame, not an atom of steam involved in the transformation. there are no dust-grimed laborers; there is no glare of furnace, no glow of heat, no stifling odor of burning fuel;--there is only the restful hum of the machinery that responds to the ceaseless flow of the silent and invisible waters. day and night the mighty river here pulls away at its turbine harness; and man, having once adjusted that harness, may take his ease and enjoy the fruits of his ingenuity. as we return now to the top of the building, we shall view the spinning dynamos with renewed interest, and a few facts regarding their output of energy may well claim our attention. in their principle of action, as we have seen, all dynamos are alike,--depending upon the mutual relations between the wire-wound armature and a magnetic field. in the present case the magnets are made to revolve and the armatures are stationary, but this is a mere detail. there is one feature of these dynamos, however, which is of greater importance,--the fact namely that they operate without commutators, and therefore produce alternating currents. this fact has an important bearing upon the distribution of the current. each of the dynamos before us generates the equivalent of five thousand horse-power of energy. there are eleven such dynamos here before us; there are ten more in the power-house on the other side of the canal, giving a total of one hundred and five thousand horse-power for this single plant; and there are five such plants now in existence or in course of construction to utilize the waters of niagara, three being on the canadian shore. when in full operation the aggregate output of these plants will be six or seven hundred thousand horse-power. subterranean tail-races as we step from the door of the power-house and stand again beside the canal whose waters produce the wonderful effects we have witnessed in imagination, one question remains to be answered: what becomes of the water after it has passed through the turbine wheels down there in the depths? the answer is simple: all the water from the various turbines flows away into a great subterranean canal which passes down beneath the city of niagara falls, and discharges finally at the level of the rapids a few hundred yards below the falls. the construction of this subterranean canal would in itself have been considered a great engineering feat a few decades ago; but of late years mountain tunnels, such subterranean railways as the london "tube system" and tunnels beneath rivers have robbed such structures of their mystery. it may be added that another such subterranean canal, to serve as a tail-race for one of the new canadian plants, extends beneath the cataract itself, discharging not far from the centre of the horseshoe falls. another of the power companies utilizes the water of the old surface canal which extends to the brink of the gorge some distance below the falls. yet another company on the canadian side conveys water from far above the rapids in a gigantic closed tube to the brink of the gorge just below the canadian falls, above the point where their power-house is located. but the principle involved is everywhere the same. the idea is merely to utilize the weight of falling water. the water of niagara river is of course no different from any other body of water of equal size. it is merely that its unique position gives the engineer an easy opportunity to utilize the potential energy that resides in any body of water--or, for that matter, in any other physical substance--lying at a high level. in due course, doubtless, other bodies of water, such as mountain lakes and mountain streams will be similarly put into electrical harness. the electrical feature is of course the one that most appeals to the imagination. but it may be well to recall that the ultimate source of all the power in question is gravitation. people fond of philosophical gymnastics may reflect with interest that, according to the newest theory, gravitation itself is, in the last analysis, an electrical phenomenon--a reflection which, it will be noted, leads the mind through a very curious cycle. the effect on the falls much solicitude has been expressed as to the possible effect, upon the falls themselves, of this withdrawal of water. for the present, it is admitted, there is no visible effect; and to the casual observer it may seem that almost any quantity of water the power-houses are likely to need might be withdrawn without seriously marring the wonderful cataract. but the statistics supplied by the power companies, taken in connection with estimates as to the bulk of water that passes over the falls, do not support this optimistic view. taking what seems to be a reasonable estimate for a basis of computation it would appear that when the power-houses now rapidly approaching completion are in full operation, the total withdrawal of water from the stream will represent a very appreciable fraction of its entire bulk--one-twenty-fifth at the very least, perhaps as much as one-tenth. such a diminution as this will by no means ruin the falls, yet it would seem as if it must sensibly affect them, particularly at some places near goat island, where the water flows at present in a very shallow stream. be that as it may, however, the power-houses are there, and it is probable that their number will be added to as years go on. whether commercialism or æstheticism will win in the end, it remains for the legislators of the future to decide. meanwhile, it is gratifying to reflect that for the present the falls retain their pristine beauty, even though part of the water that is their normal due is turned aside and made to do service for man in another way. there is only one reason why the falls have escaped desecration so long as they have; that reason being the very practical one that until quite recently man has not known how to utilize their powers to advantage. the effort was indeed made, a full generation ago, through the construction of the canal leading from the upper river to the bluffs overlooking the gorge below the cataract. here a few mill-wheels were set whirling, and a tiny fraction of the potential energy of the water was utilized. there was no mechanical difficulty involved in the utilization of this power. mill-wheels are a familiar old-time device, and even the turbine wheel is modern only in a relative sense of the word. and it must be understood that the turbine water-wheel utilizes the greatest proportion of the power of falling water of any contrivance as yet known to mechanics. it was possible, then, to utilize the water of niagara with full effectiveness fifty years ago, so far as the direct action of the water-wheel upon machinery near at hand was concerned. the sole difficulty lay in the fact that only a small amount of machinery can be placed in any one location. the real problem was not how to produce the power, but how to transmit it to a distance. the transmission of power for fifty years mechanical engineers have looked enviously upon unshackled niagara, and have striven to solve the problem of transmitting its power. it were easy enough to harness the great fall, but futile to do so, so long as the power generated must be used in the immediate vicinity. so, many schemes for transmitting power were tried one after another, and as often laid aside. there was one objection to even the best of them--the cost. at one time it was thought that compressed air might solve the problem. but repeated experiments did not justify the hope. then it was believed that the storage battery might be made available. the storage battery, it might be explained, does not really store electricity in the sense in which the leyden jar, for example, stores it. rather is it to be likened to an ordinary voltaic cell, the chemical ingredients of which have been rendered active by the passage of the electric current. the active ingredients of the storage battery are usually lead compounds, which through action of the electric currents have been decomposed and placed in a state of chemical instability. the dissociated molecule of the lead compound, when permitted to reunite with the atoms with which it was formerly associated, will give up electrical energy. such a storage battery might readily be charged with electricity generated at niagara falls. it might then be conveyed to any part of the world, and, its poles being connected, the charge of electricity would be made available. such storage batteries are in common use in connection with electric automobiles, as we have seen. but the great difficulty is that they are enormously heavy in proportion to the amount of electricity that they can generate; therefore, their transportation is difficult and expensive. in practice it is cheaper to produce electricity through the operation of a steam engine in a distant city than to transmit the electricity with the aid of a storage battery from niagara. so the storage battery served as little as compressed air to solve the engineer's problem. when the electric dynamo became a commercial success for such purposes as the operation of trolley lines it seemed as if the niagara problem was on the verge of solution. and so, in point of fact, it really was, though more time was required for it than at first seemed needed. the power generated by the dynamo could, indeed, be transmitted along a wire, but not without great loss. sir william siemens, in 1877, had pointed out in connection with this very subject of the wasted power of niagara, that a thousand horse-power might be transmitted a distance of, say, thirty miles over a copper rod three inches in diameter. but a copper rod three inches in diameter is enormously expensive, and when siemens further stated that sixty per cent of the power involved would be lost in transmission, it was obvious that the method was far too wasteful to be commercially practicable. for a time the experimenters with the transmission of electricity along a wire were on the wrong track. they were experimenting with a continuous current which, as we have seen, is produced from an ordinary dynamo with the aid of a commutator. but hosts of experiments finally made it clear that this form of current, no matter how powerful it might be, is unable to traverse considerable distance without great loss, being frittered away in the form of heat. but the very term "continuous current" implies the existence of a current that is not continuous. in point of fact, we have already seen that a dynamo, if not supplied with a commutator, will produce what is called an alternating current, and such a current has long been known to possess properties peculiar to itself. it is, in effect, an interrupted current, and it is sometimes spoken of as if it really consisted of an alternation of currents which move first in one direction and then in another. such a conception is not really justifiable. the more plausible explanation is that the alternating current is one in which the electrons are not evenly distributed and move with irregular motion. perhaps we may think of the individual electrons of such a current as oscillating in their flight, and, as it were, boring their way into the resisting medium. in any event, experience shows that such a current, under proper conditions, may be able to traverse a conducting wire for a long distance with relatively small loss. it must be understood, however, that the mere fact that a current alternates is not in itself sufficient to make feasible its transmission to a remote distance. to meet all the requirements a current must be of very high voltage. this means, in so far as we can represent the conditions of one form of energy in the terms of another, that it shall be under high pressure. fortunately a relatively simple apparatus enables the electrician to transform a current from low to high voltage without difficulty. and so at last the problem of transmitting power to a distance of many miles has been solved. electrical currents representing thousands of horse-power are to-day transmitted from niagara falls to the city of buffalo over ordinary wires, with a loss that is relatively insignificant. a plant is in process of construction that will similarly transmit the power to toronto; and it is predicted that in the near future the powers of niagara will be drawn upon by the factories of cities even as far distant as new york and chicago. practical difficulties still stand in the way of such very distant transmission, to be sure, but these are matters of detail, and are almost certain to be overcome in the near future. all this being explained, it will be understood that the sole reason why the new power-houses at niagara generate electricity is that electricity is the one readily transportable carrier of energy. we have already explained that there is loss of energy when the steam engine operates the dynamo. at niagara, of course, no steam is involved; it is the energy of falling water that is transformed into the energy of the electrical current. moreover, the revolving dynamo is attached to the same shaft with the turbine water-wheel, so that there is no loss through the interposition of gearing. yet even so, the electric current that flows from the dynamo represents somewhat less of energy than the water current that flows into the turbine. this loss, however, is compensated a thousandfold by the fact that the energy of the electric current may now be distributed in obedience to man's will. "step up" and "step down" transformers the dynamos in operation at niagara do not differ in principle from those in the street-car power-house, except in the fact that they are not supplied with commutators. we have seen that these dynamos are of enormous size. those already in operation generate five thousand horse-power; others in process of construction will develop ten thousand. the generator which produces this enormous current is about eleven feet in diameter, and it makes two hundred and fifty revolutions per minute. the armatures are so wound that the result is an alternating current of electricity of twenty-two hundred volts. this current represents, it has been said, raw material which is to be variously transformed as it is supplied to different uses. to factories near at hand, indeed, the current of twenty-two hundred volts is supplied unchanged; but for more distant consumption it is raised to ten thousand volts; and that portion which is sent away to the factories of buffalo and other equally distant places is raised to twenty-two thousand volts. [illustration: electrical transformers. the upper figure shows ferranti's experimental transformer built in 1888. it has a closed iron circuit, built up of thin strips filling the interior of the coil and having their ends bent over and overlapping outside. the lower figure shows a simple transformer known as sturgeon's induction coil. the middle figure gives a view of the series of converters in the power house of the manhattan elevated railway.] the transformation from a relatively low voltage to the high one is effected by means of what is called a step-up transformer. this is an apparatus which brings into play a principle of electric induction not very different from that which was responsible for the generation of the current of electricity in the dynamo. the principle is that evidenced in the familiar laboratory apparatus known as the ruhmkorff coil. the transformer consists essentially of a primary coil of relatively large wire, surrounded by, but insulated from, a secondary coil of relatively fine wire. when the interrupted current is sent through the primary coil of such an apparatus, an induced counter-current is generated in the secondary coil. of course there is no gain in the actual quantity of electricity, but the voltage of the current generated in the finer wire is greatly increased. for example, as we have seen, the current that came from the dynamo at twenty-two hundred volts is raised to ten thousand or twenty-two thousand volts. these proportions may be varied indefinitely by varying the relative sizes and lengths of the primary and secondary coils. how shall we picture to ourselves the actual change in the current represented by this difference in voltage? we might prove, readily enough, that the difference is a real one, since a wire carrying a current of low voltage may be handled with impunity, while a similar wire carrying a current of high voltage may not safely be touched. but when we attempt to visualize the difference in the two currents we are all at sea. we may suppose, of course, that electrons spread out over a long stretch of the secondary coil must be more widely scattered. one can conceive that the electrons, thus relatively unimpeded, may acquire a momentum, and hence a penetrative power, which they retain after they are crowded together in a straight conductor. but this suggestion at best merely hazards a guess. arrived at the other end of its journey, the current which travels under this high voltage is retransformed into a low-voltage current by means of an apparatus which simply reverses the conditions of the step-up transformer, and which, therefore, is called a step-down transformer. the electricity which came to buffalo as a twenty-two-thousand-volt current is thus reduced by any desired amount before it is applied to the practical purposes for which it is designed. it may, for example, be "stepped-down" to two thousand volts to supply the main wires of an electric-lighting plant; and then again "stepped-down" to two hundred volts to supply the electric lamps of an individual house. who that reads by the light of one of these electric lamps, let us say in buffalo, and realizes that he is reading by the transformed energy of niagara river, dare affirm that in our day there is nothing new under the sun? xi the banishment of night one great fundamental advantage that man has won over the other animals is that although by nature a diurnal animal he has made night almost equally subject to his dominion through the use of artificial light. he thus establishes an average day of sixteen or eighteen hours in place of the twelve-hour day within which his activities would otherwise be restricted. of course this conquest of the night began at an early stage of the human development, since a certain familiarity with the uses of fire was attained long before man came out of the ages of savagery. but when the transition had been made from the primitive torch to the simplest type of lamp, there was for many centuries a cessation of progress in this direction, and it remained for comparatively recent generations to provide more efficient methods of lighting. indeed, the culminating achievements are matters which make the most recent history. it is the purpose of the ensuing pages to narrate the story of the successive practical achievements through which man has been enabled virtually to turn night into day. primitive torch and open lamp to moderns, in an age when even the time-honored gas jets and kerosene lamps are regarded as obsolescent, that ancient form of illuminant, the candle, seems about the most primitive form of light-producing apparatus. in point of fact, however, the candle holds no such place in the chronological order of lighting-device discovery, being a relatively late innovation. indeed, lamps of various kinds, even those burning petroleum, were used thousands of years before the relatively clean and effective candle was invented. the camp fires of primitive man must have suggested the use of a fire-brand for lighting purposes almost as soon as the discovery of fire itself; but the development of any means of lighting his caves or rude huts, even in the form of torches, was probably a slow process. for our earliest ancestors were not the nocturnal creatures their descendants became early in the history of civilization. to them the period of darkness was the time for sleeping, and their waking hours were those between dawn and dusk. it was only when man had reached a relatively high plane above the other members of the animal kingdom, therefore, that he would wish to prolong the daylight, and then the use of the torch made of some resinous wood would naturally suggest itself. just when the ancient lamp was invented in the form of a vessel filled with oil into which some kind of wick was dipped, cannot be ascertained, but its invention certainly antedated the christian era by several centuries. and it is equally certain that once this smoky, foul-smelling lamp had been discovered, it remained in use, practically without change or improvement, until the end of the twelfth century, the date of the invention of the candle. such lamps were used by the greeks and romans, great quantities of them being still preserved. they were simply shallow, saucer-like vessels for holding the oil, into which the wick was laid, so arranged that the upper end rested against the edge of the vessel. here the oil burned and smoked, capillarity supplying oil to the burning end of the wick, which was pulled up from time to time as it became shortened by burning, either with pincers made for the purpose, or perhaps more frequently by the ever useful hairpin of the matron. as the thick wick did not allow the air to penetrate to burn the carbon of the oil completely, a nauseous smoke was given off constantly which was stifling when a draught of air prevented its escape through the hole in the roof--the only chimney used by the greeks. and since this was the only kind of lamp known at the time, the palace of the roman emperor and hut of the roman peasant were necessarily alike in their methods of lighting if in little else. the emperor's lamps might be modeled of gold and set with precious stones, while those of the peasant were of rudely modeled clay; but each must have evoked, along with its dim light, an unwholesome modicum of smoke and malodor. it was this form of lamp, practically unaltered except occasionally in design, that remained in common use during the middle ages; and when, at the close of the twelfth century, the "tallow candle" was invented, that now despised device must have been almost as revolutionary in its effect as the incandescent burner and the electric bulb were destined to be in a more recent generation. it burned with dazzling brilliancy in comparison with the oil lamp; it gave off no smoke and little smell; it needed no care, and it occupied little space. then for the first time in the history of the world reasonably good house illumination became possible. several additional centuries elapsed, however, before the idea was developed of placing a candle in a covered glass-sided receptacle, to form a lantern or a street lamp. for generations the candle held supreme place, though its cost made it something of a luxury; doubly so if wax was substituted for tallow in its composition. but toward the close of the eighteenth century, when the action of combustion had begun to be better understood, attempts were made to improve the wicks and burners of oil lamps. in 1783, an inventor named leger, of paris, produced a burner using a broad, flat, ribbonlike wick in which practically every part of the oil supply was brought into contact with the air, producing, therefore, a steady flame relatively free from smoke. the flame, while broad, was extremely thin, and its light was consequently radiated very unevenly. portions of a room lying in the direction of the long axis of the flame were but poorly lighted. to overcome this difficulty, a curved form of burner was adopted; and this led eventually to the invention of the circular argand burner, the prototype of the best modern lamp-burners. tallow candle and perfected oil lamp stated in scientific terms, the problem of the ideal lamp-wick resolves itself into a question of how to supply oxygen to every portion of the flame in sufficient quantities to bring all the carbon particles to a temperature at which they are luminous. it occurred to argand that this could be done by giving the wick a circular form like a cylindrical tube, giving the air free access to the centre of the tube as well as to its outer surface. in his lamp the reservoir of oil was placed at a little distance from, and slightly above, the tube holding the burner, connected with it by a small tube much as the tank of the modern "student lamp" connects with the burner. in this manner a fairly good lamp was produced,--a decided improvement over any made heretofore,--and when, in 1765, quinquet added a glass chimney to this lamp a new epoch of artificial lighting was inaugurated. "this date is of as much importance in artificial lighting as is 1789 in politics," says one writer. "between the ancient lamps and the lamps of quinquet there is as much difference as between the chimney-place of our parlors and the fireplaces of our original aryan ancestors, formed by a hole dug in the ground in the centre of their cabins." a little later carcel still further improved the quinquet lamp by adapting a clock movement that forced the oil to rise to the wick, so that it was no longer necessary to have the burner and the reservoir separated by a tube. this was still further improved upon by substituting a spring for the clockwork, the result being a lamp of great simplicity, yet one which gave such results that it replaced the candle as a unit for measuring the illuminating power of different sources of light. these various burners should not be confused with the modern burners of the ordinary kerosene lamps. mineral oils had not as yet come into use for illuminating purposes, except as torches or in simple lamps like those of the romans, as refining processes had not been perfected, and the smoke and odors from crude petroleum were absolutely intolerable in closed rooms. many other substances were tried in place of the heavy oils, such as the volatile hydrocarbons and alcohols, but with no great success. early in the nineteenth century a lamp burning turpentine, under the name of "camphine," was invented that gave a good light and was smokeless; but like most others of its type, it was dangerous owing to its liability to explode. and it was not until methods of refining petroleum had been improved that "mineral-oil lamps"--the predecessors of the modern type of lamps--came into use. the invention of this type of lamp was a relatively easy task--a simple transition and adaptation as processes of refining the oil were perfected. the principle of combustion was, of course, the same as in the argand type of lamps burning animal and vegetable oils; but mineral oils are of such consistency that capillarity causes an abundant supply of oil to rise in the wick, so that clockwork and spring devices, such as were used in the carcel lamps, could be dispensed with. gas lighting while the rivalry between the candle and the new forms of lamps was at its height, and just as the lamp was gaining complete supremacy, a new method of artificial illumination was discovered that was destined to eclipse all others for half a century, and then finally to succumb to a still better form. as early as the beginning of the eighteenth century the rev. joseph clayton, in england, had made experiments in the distillation of coal, producing a gas that was inflammable. a little later dr. stephen hales published his work on _vegetable staticks_, in which he described the process of distilling coal in which a definite amount of gas could be obtained from a given quantity of coal. no practical use was made of this discovery, however, until over half a century later. but just at the close of the century a scot, william murdoch, became interested in the possibilities of gases as illuminants, and finally demonstrated that coal gas could be put to practical use. in 1798, being employed in the workshops of boulton and watt in birmingham, he fitted up an apparatus in which he manufactured gas, lighting the workshops by means of jets connected by tubes with this primitive plant. shortly after this, a frenchman, m. lebon, lighted his house in paris with gas distilled from wood, and the parisians soon became interested in the new illuminant. england seems to have been the first country to use it extensively in public buildings, however, the london lyceum theatre being lighted with gas in 1803. by 1810 the great gas-light and coke company was formed, and within the next five years gas street-lamps had become familiar objects in the streets of london, and house illumination by this means a common thing among the wealthier classes. in the early days of gas-lighting the results were frequently disappointing, because no suitable and efficient type of burner had been devised; but in 1820 neilson of glasgow discovered the principle of the now familiar flat burner, of which more examples still remain in use the world over than of all other kinds combined. indeed, this simple, but as we now regard it, inefficient burner, would probably have remained the best-known type for many years longer than it did had not the possibilities of lighting by electricity aroused persons interested in the great gas-plants to the fact that the new illuminant was jeopardizing their enormous investments; making it clear that they must bestir themselves and improve their flat burners if they would arrest disaster. to be sure, several modifications of the round argand burner had been introduced from time to time, some of them being a distinct improvement over the flat burner, but these did not by any means seriously compete with electric light. and it was not until the incandescent mantle was perfected that gas as a brilliant illuminant was able to make a stand against its new competitor. the incandescent gas mantle it has been known almost since the beginnings of civilization that all solids can be made to emit light when heated to certain temperatures. some substances were known to be peculiarly adapted to this purpose, such as lumps of lime, and for many years the calcium light or "lime-light" as it is popularly called, had been in use for special purposes, and was the most intense light known. this light is made by heating a block of lime to the highest practicable temperature by means of a blast of oxygen and coal gas; but such lights were too complicated and expensive for general purposes. it had been determined even as early as the beginning of the nineteenth century, however, that the high temperature necessary for producing this light was due in part at least to the fact that such a large amount of material had to be raised to incandescence. it was evident, therefore, that if a small amount of some such substance as lime and magnesia could be spread out so as to present a large surface in a small space, such as is represented by basket-work, sufficient heat for making it incandescent might be obtained from an ordinary gas-and-air blowpipe. here then was the germ of the "mantle" idea; and such an apparatus, known as the clamond mantle, which was made of threads of calcined magnesia, was shown at the crystal palace exhibition, in london, in 1882. curiously enough, this mantle and burner worked in an inverted position, the mantle being suspended bottom upwards below the burner through which the blast of gas was forced. the light given by this mantle was most brilliant--little short of the older calcium light, in fact--but the device itself was too complicated to be of service for ordinary lighting purposes. the principle was correct, but the construction of the mantle was defective. meanwhile a german scientist, dr. auer von welsbach, who had become famous in the scientific world for his researches on rare metals, was experimenting with certain oxides of different metals, and developing a method of handling them that finally resulted in the perfected incandescent burner in use at present. his process, which in theory at least was not entirely original with him, was to dip an open fabric of cotton into a solution of the nitrates of the metals to be used, drying it, and converting the nitrates into oxides by burning; the cotton fabric disappearing but leaving the skeleton of the oxide, which retained its original shape. at the same time corresponding improvements were made in the type of burner, which is quite as essential to success as the mantle itself. it had been found that it was absolutely essential for such a burner to give a practically non-luminous flame, as otherwise the deposit of carbon particles will ruin the mantle. two ways of obtaining this are possible; one by mixing a certain quantity of air with the gas before combustion, the other to burn the gas in so thin a flame that the air permeates it freely. several burners of both types were used at first, but gradually the burners in which the air is mixed with the gas became the more popular, and most of the incandescent burners now on the market are of this type. in the construction of mantles at the present time, while the principle of their use remains the same as that of the lime-light, lime itself is not used, the oxides of certain other metals having proved better adapted for the purpose. thus the welsbach patent of 1886 covered the use of thoria, either alone or mixed with other substances such as zirconia, alumina, magnesia, etc.; thoria being considered as having a very high power of light emission. later it was discovered that pure thoria emits very little light by itself, although it possesses a refractory nature that gives a stability to the mantle unequalled by any other material as yet discovered. when combined with a small trace of the oxides of certain rare metals, however, such as uranium, terbium, or cerium, thoria mantles have a very high power of light emission, most modern mantles being composed of about ninety-nine per cent. thoria with one per cent. cerium. in the ordinary method of manufacturing such mantles, a cotton-net cylinder about eight inches long, more or less according to the size of mantle required, is made, one end being contracted by an asbestos thread. a loop of the same material, or in some cases a platinum wire, is fastened across the opening, to be used for suspending the mantle when in use. the cotton-thread cylinder is soaked in a solution of the nitrates of the metals thorium and cerium, and is then wrung out to remove the excess, stretched on a conical mold, and dried. the flame of an atmospheric burner being applied to the upper part at the constricted position, the burning extends downward, converting the nitrates into oxides, and removing the organic matter. considerable skill is required in this part of the process, as the regular shape of the mantle is largely dependent upon the regularity of the burning. as a finishing process a flame is applied to the inside of the mantle after it has cooled, to remove all traces of carbon that may remain. the mantle is now ready for use, but is so fragile that it can scarcely be touched without breaking, and such handling as would be necessary for shipment would be out of the question. it is therefore strengthened temporarily by being dipped into a mixture of collodion and castor oil, which, when dry, forms a firm but elastic jacket surrounding all parts. it is this collodion jacket that is burned away when the new mantle is placed on the burner before the gas is turned on. quite recently the method of manufacturing mantles used by clamond has been revived. in this method the cotton thread is dispensed with, the thread used being made from a paste containing the mantle material itself. the paste is placed in a proper receptacle the bottom of which is perforated with minute openings, and subjected to pressure, squeezing out the material in long filaments. when dry these are wound on bobbins, and, after being treated by certain chemical processes, are ready for weaving into mantles. it is claimed for mantles made on this principle that they last much longer and retain their light-emitting power more uniformly than mantles made by the older process. the introduction of acetylene gas when the incandescent mantle had been perfected so as to be an economical as well an as efficient light-giver, the position of coal gas as an illuminant seemed again secured against the encroachments of its rivals, the arc and incandescent electric lights. but just at this time another rival appeared in the field that not only menaced the mantle lamp but the arc and incandescent light as well. curiously enough, this new rival, acetylene gas, had been brought into existence commercially by the electric arc itself. for although it had been known as a possible illuminant for many years, the calcium carbide for producing it could not be manufactured economically until the advent of the electric furnace, itself the outcome of davy's arc light. even as early as 1836 an english chemist had made the discovery that one of the by-products of the manufacture of metallic potassium would decompose water and evolve a gas containing acetylene; and this was later observed independently from time to time by several chemists in different countries. no importance was attached to these discoveries, however, and nothing was done with acetylene as an illuminant until the last decade of the nineteenth century. by this time electric furnaces had come into general use, and it was while working with one of these furnaces in 1892 that mr. thomas f. wilson, in preparing metallic calcium from a mixture of lime and coal, produced a peculiar mass of dark-colored material, calcium carbide, which, when thrown into water, evolved a gas with an extremely disagreeable odor. when lighted, this gas burned with astonishing brilliancy, and, as its cost of production was extremely small, the idea of utilizing it for illuminating was at once conceived and put into practice. the secret of the cheap manufacture of the carbide lies in the fact that the extremely high temperature required--about 4500° fahrenheit--can be obtained economically in the electric furnace, but not otherwise. thus electricity created its own greatest rival as an illuminant. it followed naturally that the ideal place for manufacturing the carbide would be at the source of the cheapest supply of electricity, and as the "harnessed" niagara falls represented the cheapest source of electric supply, this place soon became the centre of the carbide industry. here the process of manufacture is carried out on an enormous scale. in practice, lime and ground coke are thoroughly mixed in the proportion of about fifty-six parts of lime to thirty-six parts of coke. when this mixture has been subjected to the heat of the electric furnace for a short time an ingot of pure calcium carbide is formed, surrounded by a crust of less pure material. the ingot and crust together represent sixty-four parts of the original ninety-two parts of lime and coke, the remaining twenty-eight parts being liberated as carbon-monoxide gas. calcium carbide as produced by this process is a dark-brown crystalline substance which may be heated to redness without danger or change. it will not burn except when heated in oxygen, and will keep indefinitely if sealed from the air. chemically it consists of one atom of lime combined with two atoms of carbon (cac2); and to produce acetylene gas, which is a combination of carbon and hydrogen (c2h2) it is only necessary to bring it into contact with water, acetylene gas and slaked lime being formed. one pound of pure carbide will produce five and one half cubic feet of gas of greater illuminating power than any other known gas. the flame is absolutely white and of blinding brilliancy, giving a spectrum closely approximating that of sunlight. the light is so strongly actinic that it is excellent for photography. here was a gas that could be made in any desired quantities simply by adding water to a substance costing only about three cents a pound; its cost of production, therefore, representing only about one sixth of the dollar-per-thousand-feet rate usually charged for illuminating gas in our cities. it could be used in lamps and lanterns made with special burners and with the simple mechanism of a small water tank which allowed water to drip into a receptacle holding the carbide; or--reversing the process--an apparatus that dropped pieces of carbide into the water tanks. it was, in short, the cheapest illuminant known, generated by an apparatus that was simplicity itself. there were, however, two defects in this gas: its odor was intolerable--the "smell of decayed garlic," it has been aptly called--and when mixed with air it was highly explosive. the first of these defects could be overcome easily; when the burner consumed all the gas there was no odor. the second, the explosive quality, presented greater difficulties. these were emphasized and magnified by the number of defective lamps that soon flooded the market, many of these being so badly constructed that explosions were inevitable. as a result a strong prejudice quickly arose against the gas, some countries passing laws prohibiting its use. but further inquiry into the cause of the frequent disasters revealed the fact that when the burner of a lamp was constructed so that the air for combustion was supplied after the gas issued from the jet, there was no danger of explosion. and as lamps carefully constructed on this principle replaced the early ones of faulty construction, confidence in acetylene was restored. methods were devised for supplying the gas for house-illumination like ordinary gas, and the occupants of country houses were afforded a means of lighting their houses on a scale of brilliancy hitherto unapproached, yet with economy and relative safety. it was found also that the brilliancy of the acetylene flame was of such intensity that it could be used, like the electric arc light, as a search-light. it thus furnished a simple means of supplying small boats and vehicles with such lights, which they could not otherwise have had. it also supplied army signal-corps with an apparatus for flashing messages--an apparatus that was ideal on account of its simplicity and small size. at the pan-american exhibition at buffalo the various illuminating exhibits were among the most conspicuous and attractive features. but even amid the dazzling electrical displays the acetylene building was a noteworthy object. "it was the most brilliantly and beautifully lighted building in the grounds," declared one observer. "it sparkled like a diamond, and was the admiration of all visitors. in it were generators of all types--most of them supplying the gas for their own exhibits--several being the latest exponents of the art, so simple that they can be safely managed by unskilled labor; in fact, 'the brains are in the machines,' and when the attendant has charged them with carbide and filled them with water--given them food and drink--they will work steadily until they need another meal." indeed, these exhibits at the pan-american exhibition demonstrated conclusively that acetylene gas occupies a field by itself as a practical illuminant. at the same exposition a standard was established for good stationary acetylene generators for house-lighting, and the fact that a large number of generators fulfilled the requirements of the set of rules laid down showed how thoroughly the problem of handling this gas has been solved. some of these rules used as tests are instructive to anyone interested in the subject, and a few of them are given here. they specified, for example, that-"the carbide should be dropped into the water," the reverse process of letting the water drip on the carbide, as was done in most of the early generators, being condemned. "there must be no possibility of mixing air with the acetylene gas. construction must be such that an addition to the charge of carbide can be made at any time without affecting the lights. generators must be entirely automatic in their action--that is to say: after a generator has been charged, it must need no further attention until the carbide has been entirely exhausted. the various operations of discharging the refuse, filling with fresh water, charging with carbide, and starting the generator must be so simple that the generator can be tended by an unskilled workman without danger of accident. when the lights are out, the generation of gas should cease. the carbide should be fed automatically into the water in proportion to the gas consumed." perhaps the most significant thing, showing the stage of progress that has been made in overcoming the danger of explosions from acetylene gas, is that the use of generators meeting some such requirements as the above is not prohibited by fire underwriters. this in itself is very convincing evidence of their safety. the triumph of electricity throughout the ages primitive man had had constantly before him two sources of light other than that of the sun, moon, and stars. one of these, the fire of ordinary combustion, he could understand and utilize; the other, more powerful and more terrible, which flashed across the heavens at times, he could not even vaguely understand, and, naturally, did not attempt to utilize. but early in the seventeenth century some scientific discoveries were made which, although their destination was not even imagined at the time, pointed the way that eventually led to man's imitating in the most striking manner nature's electrical illumination. about this time otto von guericke, the burgomaster-philosopher of magdeburg, in the course of his numerous experiments, had discovered some of the properties of electricity, by rubbing a sulphur ball, and among other things had noticed that when the ball was rubbed in a darkened room, a faint glow of light was produced. he was aware, also, that in some way this was connected with the generation of electricity, but in what manner he had no conception. in the opening years of the following century francis hauksbee obtained somewhat similar results with glass globes and tubes, and made several important discoveries as to the properties of electricity that stimulated an interest in the subject among the philosophers of the time. gray in england, and dufay in france, who became enthusiastic workers in the field, soon established important facts regarding conduction and insulation, and by the middle of the eighteenth century the production of an electric spark had become a commonplace demonstration. but until this time it had not been demonstrated that this electric spark was actual fire, although there was no disputing the fact that it produced light. in 1744, however, this point was settled definitely by the german, christian friedrich ludolff, who projected a spark from a rubbed glass rod upon the surface of a bowl of ether, causing the liquid to burst into flame. a few years later benjamin franklin demonstrated with his kite and key that lightning is a manifestation of electricity. but neither the galvanic cell nor the dynamo had been invented at that time, and there was no possibility of producing anything like a sustained artificial light with the static electrical machines then in use. it was not until the classic discovery of galvani and the resulting invention of the voltaic, or galvanic, cell shortly after, that the electric light, in the sense of a sustained light, became possible. and even then, as we shall see in a moment, such a light was too expensive to be of any use commercially. davy and the first electric light as soon as volta's great invention was made known a new wave of enthusiasm in the field of electricity swept over the world, for the constant and relatively tractable current of the galvanic battery suggested possibilities not conceivable with the older friction machines. batteries containing large numbers of cells were devised; one having two thousand such elements being constructed for sir humphry davy at the royal institution, of london. by bringing two points of carbon, representing the two poles of the battery, close together, davy caused a jet of flame to play between them--not a momentary spark, but a continuous light--a true voltaic arc, like that seen in the modern street-light to-day. "when pieces of charcoal about an inch long and one-sixth of an inch in diameter were brought near each other (within the thirtieth or fortieth of an inch)," wrote davy in describing this experiment, "a bright spark was produced, and more than half the volume of charcoal became ignited to whiteness; and, by withdrawing the points from each other, a constant discharge took place through the heated air, in a space equal to at least four inches, producing a most brilliant ascending arch of light, broad and conical in form in the middle. when any substance was introduced into this arch, it instantly became ignited; platina melted in it as readily as wax in a common candle; quartz, the sapphire, magnesia, lime, all entered into fusion; fragments of diamond and points of charcoal and plumbago seemed to evaporate in it, even when the connection was made in the receiver of an air-pump; but there was no evidence of their having previously undergone fusion. when the communication between the points positively and negatively electrified was made in the air rarefied in the receiver of the air-pump, the distance at which the discharge took place increased as the exhaustion was made; and when the atmosphere in the vessel supported only one-fourth of an inch of mercury in the barometrical gauge, the sparks passed through a space of nearly half an inch; and, by withdrawing the points from each other, the discharge was made through six or seven inches, producing a most brilliant coruscation of purple light; the charcoal became intensely ignited, and some platina wire attached to it fused with brilliant scintillations and fell in large globules upon the plate of the pump. all the phenomena of chemical decomposition were produced with intense rapidity by this combination." it will be seen from this that as far as the actual lighting-part of davy's apparatus was concerned, it was completely successful. but the source of the current--the most essential part of the apparatus--was such that even the wealthy could hardly afford to indulge in it as a luxury. the initial cost of two thousand cells was only a small item of expense compared with the cost of maintaining them in working order, and paying skilled operators to care for them. so that for the moment no practical results came from this demonstration, conclusive though it was, and the introduction of a commercial electric light was of necessity deferred until a cheaper method of generating electricity should be discovered. this discovery was not made for another generation, but then, as seems entirely fitting, it was made by davy's successor and former assistant at the royal institution, sir michael faraday. his discovery of electromagnetic induction in 1831 for the first time made possible the electric dynamo, although still another generation passed before this invention took practical form. in the meantime, however, the magneto-electric machine of nollet was used for generating an electric current for illuminating purposes as early as 1863; and when finally the dynamo-electric machine was produced by gramme in 1870, engineers and inventors had at their disposal everything necessary for producing a practical electric illuminant. it must not be supposed, however, that inventors stood by patiently with folded hands waiting for the coming of a machine that would furnish them with an adequate current without attempting to produce electric lamps. on the contrary, they were constantly wrestling with the problem, in some instances being fairly successful, even before the invention of the magneto-electric machine. great advances had been made in batteries and cell construction over the primitive cells of the time of davy, and for exhibition purposes, and even for lighting factories and large buildings, fairly good electric lights had been used before 1863. the first practical application of electric lighting seems to have been made in france in 1849. during the production of the opera "the prophet" the sun was to appear, and for this purpose an electric arc light was used. the success of this effort--an artificial sun being produced that seemed almost as dazzling to the astonished audience as old sol himself--stimulated further efforts in the same direction. the previous year w. e. staite in england made experiments along similar lines in the large hall of the hotel of sunderland. he generated a light "resembling the sun, or the light of day, and making candles appear as obscure as they do by daylight," according to the _times_ of the following morning. the electric light was therefore proved to be a practical illuminator, although it was not until the introduction of the gramme dynamo-electric machine that its great economic utility was demonstrated. the jablochkoff candle in sir humphry davy's experiments with his arc light he was led to believe that the light between the two points of carbon would be produced even in an absolute vacuum, if it were possible to create one. several scientists at the time disputed this contention, and m. masson, professor of physics in the _école centrale des arts et manufactures_ in paris was particularly active in combatting the idea, maintaining that the arc had the same cause as the electric spark--the transport by electricity of the incandescent particles of the electrodes through the atmosphere. it was certain, at any rate, that no light was produced when the opposing carbons were brought into contact with each other, or were, on the other hand, separated too widely; and since there was a constant wearing away and shortening of the points, and thus a constantly increasing space between them, the great difficulty in making a practical lamp lay in regulating this distance automatically. it was finally accomplished, however, by the invention of a russian officer, m. jablochkoff, in 1876. the "jablochkoff candle," as his lamp was called, marked an epoch in the history of electric lighting. one great merit of this invention was its simplicity, and while it has long since gone out of use, having been superseded by still simpler and better devices, it must always be recalled as an important stepping-stone in the progress of artificial illumination. the name "candle" for jablochkoff's lamp was suggested by the fact that the two carbons were placed side by side, instead of point to point, the light at the top thus suggesting a candle. between these two carbons, and extending their whole length except at the very tips, was an insulating material that the arc could not pierce, but which burned away at a rate commensurate with the shortening of the carbons. in this manner the points were kept constantly at the proper distance without regulating-machinery of any kind. this ingenious apparatus had the additional advantage that it could be placed on any kind of a bracket or chandelier that was properly wired, thus dispensing with the cumbersome frames and machines of the point-to-point carbon arc lights then being introduced. one difficulty at first encountered in using the jablochkoff candle was the starting of the voltaic arc. in doing this it was necessary that contact be made between two carbon points, whether they lie parallel or point to point, and the necessary slight separation for producing the light effected later. to accomplish this jablochkoff joined the tips of the carbons of his candle with a thin strip of carbon, which quickly burned away when the current was turned on, leaving the necessary space between the points for the arc. there was one difficulty with the "candle" that seemed insurmountable for a time--the wasting of the two carbons was unequal, as in any arc light, the points thus gradually drawing apart until the passage of the current was no longer possible. to overcome this the rapidly wasting positive carbon was made double the thickness of its mate; but while this answered fairly well the thinner negative carbon gradually became heated by the increased resistance, and burned up too rapidly. the difficulty was finally overcome by the simple expedient of alternating the flow of the current, so that each carbon was alternately a positive and a negative pole. as the magneto-electric machines then in use produced alternating currents it was only necessary to use such machines for generating the current to produce an equal destruction of both carbons. the simplicity and excellence of the light of these "candles" brought them at once into general popularity, not only in the large cities of europe, but in many out-of-the-way places. greece, portugal, and other obscure european countries adopted them, and even brazil, la plata, and mexico installed many plants. but stranger still, they were soon used for illuminating the palaces of the shah of persia and the king of cambodia, and a little later were introduced into the residence of the savage king of burma. in short, their use became universal almost immediately. the improved arc light about the time that jablochkoff's candles were making such a sensation in europe, charles f. brush, of cleveland, ohio, invented an arc light in which the carbons were set point to point, the distance being maintained and the necessary feed produced automatically in much the same manner as in the lamps used at present. other inventions soon followed, some of the lamps being regulated by clockwork, some by electricity and magnetism. the advantage of this type of arc lamp over the candle type--an advantage that led to its general adoption--was largely that of efficiency, a far greater amount of light being obtainable from the same expenditure of power by the point-to-point type of lamp. in this lamp it is necessary that the points of carbon shall come in contact when the current is off, but be drawn apart a moment after the current is turned on, and remain at this fixed distance. to accomplish this, the lower carbon is usually made stationary, the feeding being regulated by the position of the upper carbon. in the usual type of modern lamp the passage of the current causes the points to separate the required distance through the action of an electromagnet the coils of which are traversed by the current. a clutch holds the carbon in place, the position of this being also determined by an electromagnet. the action is regulated by the difference in the resistance to the passage of the current caused by the increase in the separation of the points. in the older type of arc lamp it was necessary to "trim" the lights by replacing the carbons every day; but recently lamps have been perfected in which the carbons last from one hundred to one hundred and twenty hours. in these the arc is enclosed in a glass globe which is made as nearly air-tight as possible with the necessary feed devices. this closed chamber is fitted with a valve opening outward, which allows the air to be forced out by the heat of the lamp, but does not admit a return current. in this manner a rarefied chamber is produced in which the carbons are oxidized very slowly; yet there is no diminution in the brilliancy of the light. early in the history of electric lighting it became apparent that the proper construction of the carbon electrodes was a highly important item in the manufacture of a lighting apparatus. the value of carbons depends largely upon their purity and freedom from ash in burning, and it required a countless number of experiments to develop the highly efficient carbons now in general use. davy made use of pieces of wood charcoal in his experiments, but these were too fragile to be of practical value, even if their other qualities had been ideal. later experimenters tried various compounds, and in 1876 carré in france produced excellent carbons made of coke, lampblack, and syrup. from these were developed the present carbons, usually made by mixing some finely divided form of carbon, such as soot or lampblack made from burning paraffin or tar, with gum or syrup to form a paste. rods of proper size and shape are made by forcing this paste through dies by hydraulic pressure, subsequently baking them at a high temperature. sometimes they are given a coating of copper, a thin layer of the metal being deposited upon them by electrolysis. edison and the incandescent lamp the familiar incandescent electric-light bulb seems such a simple apparatus to-day, being nothing apparently but a small wire enclosed in an ordinary glass bulb, that it is almost impossible to realize what an enormous amount of money, energy, and that particular quality of mentality which we call "genius" has been required to produce it. first and foremost among the names of the men of genius who finally evolved this lamp is that of thomas a. edison; and only second to this foremost name are those of swan, lane-fox, and hiram maxim. but edison's name must stand preeminent; and there are probably very few, even among europeans, who would attempt or wish to deny him the enviable place as the actual perfecter of the incandescent-light bulb. [illustration: thomas a. edison and the dynamo that generated the first commercial electric light.] it is said that edison first conceived the idea of an incandescent electric light while on a trip to the rocky mountains in company with draper, in 1878. be this as it may, he certainly set to work immediately after completing this journey, and never relaxed or ceased his efforts until a practical incandescent lamp had been produced. his idea was to perfect a lamp that would do everything that gas could do, and more; a lamp that would give a clear, steady light, without odor, or excessive heat such as was given by the arc lights--in short, a household lamp. early in his experiments he abandoned the voltaic arc, deciding that a successful lamp must be one in which incandescence is produced by a strong current in a conductor, the heat caused by the resistance to the current producing the glow and light. but when search was made for a suitable substance possessing the necessary properties to be the incandescent material, the inventor was confronted by a vast array of difficulties. it was of course essential that the substance must remain incandescent without burning, and at the same time offer a resistance to the passage of the current precisely such as would bring about the heating that produced incandescence. it should be infusible even under this high degree of heat, or otherwise it would soon disappear; and it must not be readily oxidizable, or it would be destroyed as by ordinary combustion. it should also be of material reducible to a filament as fine as hair, but capable of preserving a rigid form. these, among others, were the qualities to be considered in selecting this apparently simple filament for the incandescent lamp. it was not a task for the tyro, therefore, that edison undertook when he began his experiments for producing an "ideal lamp." the substance in nature that seemed to possess most of the necessary qualities just enumerated was the metal platinum, and edison began at once experimenting with this. he made a small spiral of very fine platinum wire, which he enclosed in a glass globe about the size of an ordinary baseball. the two ends of the wires connected with outside conducting wires, which were sealed into the base of the bulb. the air in the bulb had to be exhausted and a vacuum maintained to diminish the loss of heat and of electricity and to prevent the oxidation of the platinum. but when the current was passed through the spiral wire in this vacuum a peculiar change took place in the platinum itself. the gases retained in the pores of the metal at once escaped, and the wire took on such peculiar physical properties that it was supposed for a time by some physicists that a new metal had been produced. the metal acquired a very high degree of elasticity and became susceptible of a high polish like silver, at the same time becoming almost as hard as steel. it also acquired a greater calorific capacity so that it could be made much more luminous without fusing. to diminish the loss of heat the wire was coated with some metallic oxide, and the slope of the spiral also aided in this as each turn of the spiral radiated heat upon its neighbor, thus utilizing a certain amount that would otherwise have been lost. but despite all this, edison found, after tedious experimenting, that platinum did not fulfil the requirements of a practical filament for his lamp; it either melted or disintegrated in a short time and became useless; and the other experimenters had met with the same obstacles to its use, and were forced to the same conclusion. some other substance must be found. the use of carbon for arc lights and edison's own experiments with carbon in his work on the telephone naturally suggested this substance as a possibility. it is said that this idea was brought forcibly to the inventor's attention by noticing the delicate spiral of vegetable carbon left in his hand after using a twisted bit of paper, one day, for lighting a cigar. this spiral of carbon was, of course, too fragile to be of use in its ordinary form. but it occurred to edison that if a means of consolidating it could be found, there was reason to hope that it would answer the purpose. experiments were begun at once, therefore, not only with processes of consolidation but also with various kinds of paper, and neither effort nor expense was spared to test every known variety of paper. moreover, many new varieties of paper were manufactured at great expense from substances having peculiar fibres. one of these, made from a delicate cotton grown on some little islands off south carolina, gave a carbon free from ash, and seemed to promise good results; but later it was found that the current of electricity did not circulate through this substance with sufficient regularity to get protracted and uniform effects. nevertheless, since many things pointed to this fibre carbon as the ideal substance, edison set about determining the cause of the irregularity in the circulation of the current in the filament, and a number of other experimenters soon became interested in the problem. it was soon determined that the arrangement of the fibres themselves were directly responsible for the difficulty. in ordinary paper the fibres are pressed together without any special arrangement, like wool fibres in felting. in passing through such a substance, therefore, the current cannot travel along a continuous fibre, but must jump from fibre to fibre, "like a man crossing a brook on stepping-stones." each piece of fibre constitutes a lamp or miniature voltaic arc, so that the current is no longer a continuous one; and the little interior sparks thus generated quickly destroy the filament. this discovery made it apparent that such an artificial, feltlike substance as paper could not be made to answer the purpose, and edison set about searching for some natural substance having fibres sufficiently long to give the necessary homogeneity for the passage of the current. for this purpose specimens of all the woods and fibre-substances of all countries were examined. special agents were sent to india, china, japan, south america, in quest of peculiar fibrous substances. the various woods thus secured were despatched to the edison plant at menlo park and there carefully examined and tested. without dwelling on the endless details of this tedious task, it may be said at once that only three substances out of all the mass withstood the tests reasonably well. of these, a species of japanese bamboo was found to answer the purpose best. thus the practical incandescent lamp, which had cost so much time, ingenuity, and money, came into existence, fulfilling the expectation of the most sanguine dream of its inventor. in using these bamboo carbon filaments the original spiral form of filament was abandoned, the now familiar elongated horseshoe being adopted, as the carbon could not be bent into the tortuous shapes possible with platinum. later various modifications in the shape of the filament were made, usually as adaptations to changes in the shape of the bulbs. at the same time that edison was succeeding with his bamboo carbon filaments, j. w. swan had been almost as successful with a filament formed by treating cotton thread with sulphuric acid, thus producing a "parchmentized thread," which was afterwards carbonized. a modification of this process eventually supplanted the edison bamboo filament; and the filament now in common use--the successor of the "parchmentized thread"--is made of a form of soluble cellulose prepared by dissolving purified cotton wool in a solution of zinc chloride, and then pressing the material out into long threads by pressing it through a die. the long thread so obtained is a semi-transparent substance, resembling catgut, which when carbonized at a high temperature forms a very elastic form of carbon filament. to prepare the filament the cellulose threads are cut into the proper lengths, bent into horseshoe shape, double loops, or any desired form, and then folded round carbon formers and immersed in plumbago crucibles. on heating these crucibles to a high temperature the organic matter of the filaments is destroyed, the carbon filaments remaining. these filaments are then ready for attachment to the platinum leading-in wires, which is accomplished either by means of a carbon cement or by a carbon-depositing process. they are then placed in the glass bulbs and the wires hermetically sealed, after which the bulbs are exhausted, tested, fitted with the familiar brass collars, and are ready for use. the combined discoveries of all experimenters had made it evident that certain conditions were necessary to success, regardless of the structure of the carbon filament. it was essential that the vessel containing the filament should be entirely of glass; that the current should be conveyed in and out this by means of platinum wires hermetically sealed through the glass; and that the glass globe must be as thoroughly exhausted as possible. this last requirement proved a difficult one for a time, but by improved methods it finally became possible to produce almost a perfect vacuum in the bulbs, with a corresponding increase in the efficiency of the lamps. the tungsten lamp for twenty years the carbon-filament lamp stood without a rival. but meanwhile the science of chemistry was making rapid strides and putting at the disposal of practical inventors many substances hitherto unknown, or not available in commercial quantities. among these were three metals, osmium, tantalum, and tungsten, and these metals soon menaced the apparently secure position of the highly satisfactory, although expensive, edison lamp. it will be recalled that the early experimenters had used two metals, platinum and iridium, for lamp filaments; and that these two, although unsatisfactory, were the only ones that had given even a promise of success. but in 1898 dr. auer von welsbach took out patents, and in 1903 produced a lamp using an osmium filament. its advent marked the beginning of the return to metal-filament lamps, although the lamp itself did not prove to be very satisfactory and was quickly displaced by a lamp invented by messrs. siemens and halske, having a tantalum filament. on account of its ease to manufacture, its brilliant light, and relatively low consumption of power, this lamp gained great popularity at once, and for a single year was practically without a rival. then, in 1904, patents were taken out by just and hanaman, kuzel, and welsbach, for lamps using filaments of tungsten, and the superiority of these lamps over the tantalum lamps gave them an immediate popularity never attained by either of the other metal-filament lamps. needless to say there is good ground for this popularity, which may be explained by the simple statement that the tungsten lamp gives more light with much less consumption of power per candle power than any of its predecessors. unlike the carbon filament, which projects in the familiar elongated horse-shoe loop, or double loop, into the exhausted bulb, the tungsten filament is wound on a frame, so that several filaments (usually eight or more) are used for producing the light in each bulb. the chief defect of this lamp is the fragility of the filament, which breaks easily when subjected to mechanical vibration. on the other hand, tungsten lamps can be used in places at a long distance from the central generating plant, where the electric current is too weak for carbon-filament lamps. the mercury-vapor light of peter cooper hewitt "on an evening in january, 1902, a great crowd was attracted to the entrance of the engineers' club in new york city. over the doorway a narrow glass tube gleamed with a strange blue-green light of such intensity that print was easily readable across the street, and yet so softly radiant that one could look directly at it without the sensation of blinding discomfort which accompanies nearly all brilliant artificial lights. the hall within, where mr. hewitt was making the first public announcement of his great discovery, was also illuminated by the wonderful new tubes. the light was different from anything ever seen before, grateful to the eyes, much like daylight, only giving the face a curious, pale-green, unearthly appearance. the cause of this phenomenon was soon evident; the tubes were seen to give forth all the rays except red,--orange, yellow, green, blue, violet,--so that under its illumination the room and the street without, the faces of the spectators, the clothing of the women, lost all their shades of red; indeed, changing the face of the world to a pale green-blue. "the extraordinary appearance of this lamp and its profound significance as a scientific discovery at once awakened a wide public interest, especially among electricians who best understood its importance. here was an entirely new sort of electric light. the familiar incandescent lamp, though the best of all methods of illumination, is also the most expensive. mr. hewitt's lamp, though not yet adapted to all the purposes served by the edison lamp, on account of its peculiar color, produces eight times as much light with the same amount of power. it is also practically indestructible, there being no filament to burn out; and it requires no special wiring. by means of this invention electricity, instead of being the most costly means of illumination becomes the cheapest--cheaper even than kerosene. no further explanation than this is necessary to show the enormous importance of this invention." as just stated, the defect of the edison incandescent lamp is its cost, due to its utilizing only a small fraction of the power used in producing the incandescence, and, of much less importance, the relatively short life of the filament itself. only about three per cent. of the actual power is utilized by the light, the remaining ninety-seven per cent. being absolutely wasted; and it was this enormous waste of energy that first attracted the attention of mr. hewitt, and led him to direct his energies to finding a substitute that would be more economical. a large part of the waste in the edison bulb is known to be due to the conversion of the energy into useless heat, instead of light, as shown by the heated glass. mr. hewitt attempted to produce a light that would use up the power in light alone--to produce a cool light, in short. instead of directing his efforts to the solids, mr. hewitt turned his attention to gaseous bodies, believing that an incandescent gas would prove the more nearly ideal substance for a cool light. the field of the passage of electricity through gases was by no means a virgin one, but was nevertheless relatively unexplored: and mr. hewitt was, therefore, for the most part obliged to depend upon his own researches and experiments. in these experiments hundreds of gases were examined, some of them giving encouraging results, but most of them presenting insurmountable difficulties. finally mercury vapor was tried, with the result that the light just referred to was produced. the possibilities of mercury-vapor gas had long been vaguely suspected--suspected, in fact, since the early days of electrical investigation, two centuries before. the english philosopher, francis hauksbee, as early as 1705 had shown that light could be produced by passing air through mercury in an exhausted receiver. he had discovered that when a blast of air was driven up against the sides of the glass receiver, it appeared "all round like a body of fire, consisting of an abundance of glowing globules," and continuing until the receiver was about half full of air. hauksbee called this his "mercurial fountain," and although he was unable to account for the production of this peculiar light, which he remarked "resembled lightning," he attributed it to the action of electricity. between hauksbee's "mercurial fountain" and hewitt's mercury-vapor light, however, there is a wide gap, and, as it happened, this gap is practically unbridged by intermediate experiments, for mr. hewitt had never chanced to hear anything of hauksbee's early experiments, or of any of the tentative ones of later scientists. but this, on the whole, may have been rather advantageous than otherwise, as, being ignorant, he was perhaps in a more receptive state of mind than if hampered by false or prejudicial conceptions. be this as it may, he began experimenting with mercury confined in a glass tube from which the air had been exhausted, the mercury being vaporized either by heating, or by a current of electricity. no results of any importance came of his numerous experiments for a time, but at last he made the all-important discovery that once the high resistance of the cold mercury was overcome, a comparatively weak current would then be conducted, producing a brilliant light from the glow of the mercury vapor. here, then, was the secret of the use of mercury vapor for lighting--a powerful current of electricity for a fraction of a second passed through the vapor to overcome the initial resistance, and then the passage of an ordinary current to produce the light. in practice this apparent difficulty in overcoming the initial resistance with a strong current is easily overcome by the use of a "boosting coil," which supplies the strong current for an instant, and is then shut off automatically, the ordinary current continuing for producing the light. the mechanism is hardly more complex than that of the ordinary incandescent light, but the current of ordinary strength produces an illumination about eight times as intense as the ordinary incandescent bulb of equal candle-power. the form of lamp used is that of a long, horizontal tube suspended overhead in the room, a brilliant light being diffused, which, lacking the red rays of ordinary lights, gives a bluish-green tone to objects, and a particularly ghastly and unpleasant appearance to faces and hands, as referred to a moment ago. in many ways this feature of the light is really a peculiarity rather than a defect, and for practical purposes in work requiring continued eye-strain the absence of the red rays is frequently advantageous. in such close work as that of pen-drawing, for example, some artists find it advantageous to use globes filled with water tinted a faint green color, placed between the lamps and their paper, the effect produced being somewhat the same as that of the mercury-vapor light. for such work the absence of the red rays of the hewitt light would not be considered a defect; and in workshops and offices where mr. hewitt's lamps are used the workmen have become enthusiastic over them. on the other hand, the fact that the color-values of objects are so completely changed makes this light objectionable for ordinary use; so much so, in fact, that the inventor was led to take up the problem of introducing red rays in some manner so as to produce a pure white light. he has partly accomplished this by means of pink cloth colored with rhodium thrown around the glass; but this causes a distinct loss of brilliancy. the most natural method of introducing the red rays, it would seem, would be to use globes of red glass; but a moment's reflection will show that this would not solve the difficulty. red glass does not change light waves, but simply suppresses all but the red rays; and since there are no red rays in the mercury-vapor light the result of the red globe would be to suppress all the light. obviously, therefore, this apparently simple method does not solve the difficulty; but those familiar with mr. hewitt's work will not be surprised any day to hear that he has finally overcome all obstacles, and produced a perfectly white light. in the meantime the relatively expensive arc light and the incandescent bulb with its filament of carbon or metal hold unchallenged supremacy in the commercial field. xii the mineral depths ages before the dawn of civilization, primitive man had learned to extract certain ores and metals from the earth by subterranean mining. such nations as the egyptians, for example, understood mining in most of its phases, and worked their mines in practically the same manner as all succeeding nations before the time of the introduction of the steam engine. the early britons were good miners and the products of their mines were carried to the orient by the phoenicians many centuries before the christian era. the romans were, of course, great miners, and remains of the roman mines are still in existence, particularly good examples being found in spain. even the aborigines of north america possessed some knowledge of mining, as attested by the ancient copper mines in the lake superior region, although by the time of the discovery of america, and probably many centuries before, the interloping races of indians who had driven out or exterminated the lake superior copper mines had forgotten the art of mining, if indeed they had ever learned it. but the fact that their predecessors had worked the copper mines is shown by the number of stone mining implements found in the ancient excavations about lake superior, these implements being found literally by cart loads in some places. the great progress in mining methods, however, as in the case of most other mechanical arts, began with the introduction of steam as a means of utilizing energy; and another revolution is in rapid progress owing to the perfection of electrical apparatus for furnishing power, heat, and light. methods of mining a hundred years ago were undoubtedly somewhat in advance of the methods used by the ancients; but the gap was not a wide one, and the progress made by decades after the introduction of steam has been infinitely greater than the progress made by centuries previous to that time. this progress, of course, applies to all kinds of mines and all phases of mining; but steam and electricity are not alone responsible for the great nineteenth-century progress. geology, an unknown science a century ago, has played a most active and important part; and chemistry, whose birth as a science dates from the opening years of the nineteenth century, is responsible for many of the great advances. obviously a very important feature of any mine must be its location, and the determination of this must always constitute the principal hazard in practical mining. prospecting, or exploring for suitable mining sites, has been an important occupation for many years, and has in fact become a scientific one recently. formerly mines were frequently stumbled upon by accident, but such accidental discoveries are becoming less and less frequent. the prospector now draws largely upon the knowledge of the scientist to aid him in his search. geology, for example, assists him in determining the region in which his mines may be found, if it cannot actually point out the location for sinking his shaft; and at least a rough knowledge of botany and chemistry is an invaluable aid to him. it is obvious that it would be useless to prospect for coal in a region where no strata of rocks formed during the carboniferous or coal-forming age are to be found within a workable distance below the surface of the earth. the prospector must, therefore, direct his efforts within "geological confines" if he would hope to be successful, and in this he is now greatly aided by the geological surveys which have been made of almost every region in the united states and europe. an example of what science has done in this direction was shown a few years ago in a western american town during one of the "oil booms" that excited so many communities at that time. in the neighborhood of this town evidences of oil had been found from time to time--some of them under peculiar and suspicious circumstances, to be sure--and the members of the community were in an intense state of excitement over the possibility of oil being found on their lands. prices of land jumped to fabulous figures, and the few land-owners that could be induced to part with their farms became opulent by the transactions. an "oil expert" appeared upon the scene about this time--just "happening to drop in"--who declared, after an examination, that the entire region abounded in oil. he backed up his assertion by offering to stake his experience against the capital of a company which was formed at his suggestion. before any wells were actually started, however, a prudent member of the company consulted the state geologist on the subject, receiving the assurance that no oil would be found in the neighborhood. strangely enough the word of the man of science triumphed over that of the "oil expert," and although some tentative borings were made on a minor scale, no great amount of money was sunk. it developed afterwards that the evidences of oil found from time to time had been the secret work of the "expert." in general, prospecting for oil differs pretty radically from prospecting for most other minerals. a very common way of locating an ore-mine is by the nature of the out-crop,--that is, the broken edges of strata of rocks protruding from hillsides, or tilted at an angle on level areas. if the ore-bearing vein is harder than the surrounding strata it will be found as a jutting edge, protruding beyond the surface of the other layers of rocks which, being softer, are more easily worn away. on the other hand, if this stratum is soft or decomposable it will show as a depression, or "sag" as it is called. of course such protrusions and depressions may only be seen and examined where the rocks themselves are exposed; vegetation, drift, and snow preventing such observations. but the vegetation may in itself serve as a guide to the experienced prospector in determining the location of a mine, peculiar mineral conditions being conducive to the growth of certain forms of vegetation, or to the arrangement of such growth. alterations in the color of the rocks on a hillside are also important guides, as such discolorations frequently indicate that oxidizable minerals are located above. in hilly or mountainous regions, where the underlying rocks are covered with earth, portions of these surfaces are sometimes uncovered by the method known as "booming." in using this method the prospector selects a convenient depression near the top of a hill and builds a temporary dam across the point corresponding to the lowest outlet. when snow and rain have turned the basin so formed into a lake, the dam is burst and the water rushing down the hillside cuts away the overlying dirt, exposing the rocks beneath. this method is effective and inexpensive. the beds of streams, particularly those in hilly and mountainous regions, are fertile fields for prospecting, particularly for precious metals. stones and pebbles found in the bed are likely to reveal the ore-foundations along the course of the stream, and the shape of these pebbles helps in determining the approximate location of such foundations. an ore-bearing pebble, well worn and rounded, has probably traveled some little distance from its original source, being rounded and worn in its passage down the stream. on the other hand, if it is still angular it has come a much shorter distance, and the prospector will be guided accordingly in his search for the ore-vein. but prospecting is not limited to these simple surface methods. in enterprises undertaken on a large scale, borings are frequently made in regions where there are perhaps no specific surface indications. in such regions a shaft may be sunk or a tunnel may be dug, and the condition of the underlying strata thus definitely determined. this last is, of course, a most expensive method, the simpler and more usual way being that of making borings to certain depths. the difficulty with such borings is that rich veins may be passed by the borer without detection; or, on the other hand, a small vein happening to lie in the same plane as the drill may give a wrong impression as to the extent of the vein. one of the most satisfactory ways of making borings is by means of the diamond drill. this drill is made in the form of a long metal tube, the lower edge of which is made into a cutting implement by black diamonds fixed in the edge of the metal. by rotating this tube a ring is cut through the layers of rock, the solid cylinder or core of rock remaining in the hollow centre of the drill. this can be removed from time to time, the nature and thickness of the geological formation through which the drill is passing being thus definitely determined. conditions to be considered in mining three great problems always confront the mine operator--light, power, and ventilation. of these ventilation is the most important from the workman's standpoint, although the problem of light is scarcely less so. obviously a cavity of the earth where hundreds of men are constantly consuming the atmosphere and vitiating it, and where thousands of lights are burning, would become like the black hole of calcutta in a few minutes if some means were not adopted to relieve this condition. but besides this vitiation of the atmosphere caused by the respiration of the men and the burning of lamps there are likely to be accumulations of poisonous gases in mines, that are even more dangerous. of the two classes of dangerous gases--those that asphyxiate and those that explode or burn--it may be said in a general way that the suffocating or poisonous gases, such as carbonic acid, which is known as black damp, or choke damp, are more likely to occur in ore mines, while the explosive gases are found more frequently in coal mines. choke damp, which is a gas considerably heavier than the atmosphere, is usually found near the bottom of mines, running along declines and falling into holes in much the same manner as a liquid. it kills by suffocation, and, as it will not support combustion, it may be detected by lowering a lighted candle into a suspected cavity, the light being extinguished at once if the gas is present. to rid the cavity of it, forced ventilation is used where possible, the gas being scattered by draughts of fresh air. if this is impracticable, and the cavity small, the choke damp may be dipped out with buckets. but the problem of the mining engineer is not so much to rid cavities of gas as to prevent its accumulation. in modern mining, with proper ventilation and drainage, there is comparatively little danger of extensive accumulation of this gas. [illustration: a flint-and-steel outfit, and a miner's steel mill. the upper picture shows a flint-and-steel outfit, the implements for lighting a fire before the days of matches. the lower picture shows a miner's steel mill, which was used for giving light in mines before the day of the safety-lamp. it consists of a steel disk which is rotated rapidly against a piece of flint, producing a stream of sparks. it was thought that such sparks would not ignite fire-damp--a belief which is now known to be erroneous.] the danger from this choke damp, therefore, is one that concerns the individual workman rather than large bodies of men or the structure of the mine itself. with fire damp, however, the case is different, as an explosion of this gas may destroy the mine itself and all the workmen in it. it is, therefore, the most dreaded factor in mining, and is the one to which more attention has been directed than to almost any other problem. this fire damp is a mixture of carbonic oxide and marsh gas which, being lighter than air, tends to rise to the upper part of the mines. for this reason explosions are more likely to occur near the openings of the mine, frequently entombing the workmen in a remote part of the mine even when not actually killing them by the explosion. as this gas is poisonous as well as explosive the miners who survive the explosion may succumb eventually to suffocation. previous to the year 1816 no means had been devised for averting the explosions of fire damp except the uncertain one of watching the flame of the candle with which the miner was working. on coming in contact with air mildly contaminated with fire damp the candle flame takes on a blue tint and assumes a peculiarly elongated shape which may be instantly detected by a watchful workman. but miners were, and still are, a proverbially careless class of men even where a matter of life and death is concerned, and too frequently gave no heed to the warning flame. but in 1816 sir humphrey davy invented his safety lamp, a device that has been the means of saving thousands of lives, and which has not as yet been entirely supplanted by any modern invention. in making his numerous experiments, davy had observed that iron-wire gauze is such a good conductor of heat that a flame enclosed in such gauze could not pass readily through meshes to ignite a gas on the outside. he found by experiment that a considerable quantity of explosive gas might be brought into contact with the gauze surrounding a flame, and no explosion occur. at the same time this gas would give warning of its presence by changing the color of the flame. when a lamp was made with a surrounding gauze having seven hundred and eighty meshes to the square inch, it was found to give sufficient light and at the same time to be practically non-explosive in the presence of ordinary quantities of gas. one would suppose that such a life-saving invention would have been eagerly adopted by the men whose lives it protected; but, as a matter of fact, owing to certain inconveniences of davy's lamps, many miners refused to use them until forced to do so by the mine-owners. one of these disadvantages was that this safety lamp gave a poor light overhead. this is particularly annoying to the miner, who wishes always to watch the condition of the ceiling under which he is working. when not under constant observation, therefore, a miner would frequently remove the gauze of the lamp and work by the open flame, regardless of consequences. or again, he would sometimes forgetfully use the flame for lighting his pipe. to overcome the possibility of such forgetfulness or wilful disobedience, it was found necessary to equip safety lamps with locking devices, so that the miner had no means of access to the open flame of his lamp once it had been lighted. since the time of the first davy safety lamp there have been numerous improvements in mechanical details, although the general principle remains unchanged. one of these improvements is a device whereby the lamp, when accidentally extinguished, may be relighted without opening it, and without the use of matches. this is done by means of little strips of paper containing patches of a fulminating substance which is ignited by friction, working on the same principle as the paper percussion caps used on toy pistols. but even the improved safety lamp seems likely to disappear from mines within the next few years, now that electricity has come into such general use. as yet, however, no satisfactory portable electric lamp or lantern has been perfected, such lamps being as a rule too heavy, expensive, and unreliable. even if these defects were remedied, the advantage would still lie with the davy lamp, since the electric lamp, being enclosed, cannot be used for the detection of fire damp. but this advantage of the safety lamp is becoming less important, since well-regulated mines are now more thoroughly ventilated, and the danger from fire damp correspondingly lessened. in some continental mines the experiment has been tried of constantly consuming the fire damp, before it has had time to accumulate in explosive quantities, by means of numerous open lights kept constantly burning. this method is effective, but since the numerous lights consume the precious oxygen of the air as well as the damp, the method has never become popular. obviously, then, the question of mine ventilation is closely associated with that of lighting. probably the simplest method of properly ventilating a mine is that of having two openings at the surface, one on a much higher level than the other if the mine is on a hillside, the lower one corresponding to the lowest portion of the mine where possible. by such an arrangement natural currents will be established, and may be controlled and distributed through the mine by doors or permanent partitions, or aided by fans. but of course only a comparatively small number of mines are so situated that this system can be used. it is possible, of course, to ventilate a mine from a single shaft or opening by use of double sets of pipes, one for admitting air and the other for expelling it; but this system is obviously not an ideal one, and is prohibited by law in most mining districts. such laws usually stipulate that there must be at least two openings situated at some distance from each other. the older method of creating air currents was by means of furnaces, but this method, while very effective, is expensive and dangerous. in using this system a furnace is built near the outlet of the air shaft, the combustion of the fuel creating the necessary draught. but in the nature of things this furnace is a constant menace to the mine, besides being an extremely wasteful expenditure of energy. the modern method of ventilating is by means of rotary fans, the electric fan having practically solved the problem. the air currents established by such fans are controlled either by the doors in the passages, or by means of auxiliary fans. in addition, jets of compressed air are sometimes used, and have become very popular. another important problem that constantly confronts the mining engineer is that of drainage. mines are, of course, great reservoirs for the accumulation of water, which must be drained or pumped out continually; and as the shafts are sunk deeper and deeper it becomes increasingly difficult to raise the water to the surface. special means and machinery are employed for this purpose which will be considered more in detail in a moment. electric machinery in mining electricity is, of course, the great revolutionary factor in modern mining. there is scarcely a department of mining in which electric power has not wrought revolutionary changes in recent years; and the subject has become so important and so thoroughly specialized as to "create a literature and a technology of its own." from the electric drill, working hundreds of feet below the surface of the earth, to the delicate testing-instruments in the laboratory of the assaying offices, the effect of this electrical revolution is being felt progressively more and more every year. moreover, electricity, on account of its transmutability, has made accessible many important mining sites hitherto unworkable. rich mines are now in operation on an economical basis which, thirty years ago, were worthless on account of their isolation. when such mines were situated in mountainous regions where there was no coal supply at hand for creating steam power, and where the only available water power was perhaps several miles away, operations on a paying basis were out of the question before the era of electric power. at present, however, the question of distance of the seat of power has been practically eliminated by the possibilities of electric conduction. a stream, situated miles away, when harnessed to a turbine and electric motors may afford a source of power more economical than could be furnished a few years ago by a power plant supplied with fuel at the very door of the mine. we need not enter into the details of this transmission of power, however, since the subject has been discussed in a general way in another place. our subject here is rather to deal with the application of electricity to certain mining implements of special importance. one of the most useful acquisitions to the equipment of the modern miner is a portable mechanical drill, which makes it possible for him to dispense with the time-honored pick, hammer, and hand-drill. but it is only recently that inventors have been able to produce this implement. the great difficulty has lain in the fact that a reciprocating motion, which is essential for certain kinds of drilling, is not readily secured with electric power. the use of steam or compressed air for operating such reciprocating drills presents no mechanical difficulties, and the fact that power of this kind can be transmitted long distances by the use of flexible tubes made such drills popular for several years. but the cost of operating such drills is so much greater than that of the new electric drills that they are rapidly being replaced in mining work. the first attempts to produce an electric drill with a reciprocating motion were so unsuccessful that inventors turned their attention to perfecting some rotary device. this proved more successful, and rotary drills, operating long augers and acting like ordinary wood-boring machines, are now used extensively for certain kinds of drilling. the more recent forms perform the same amount of work as the air drill, with a consumption of about one-tenth the power. moreover, none of the energy is lost at high altitudes as in the case of air drills, and they are not affected by low temperatures which sometimes render the air drill inoperable. on the other hand, the air drill is a hardy implement, capable of withstanding very rough usage, whereas the electric drill is probably the more economical, as well as the more convenient drill of the two. in certain kinds of mining, such as in the potash mines of europe and the coal mines of america, these electric drills operating their long augers have been found particularly useful. the ordinary type of drill is so arranged that it can be operated at any angle, vertically or horizontally. the lighter forms are mounted on upright stands, with screws at the ends for fastening to the floor and roof, although the heavier types are sometimes mounted on trucks. the motor, which is not much larger or heavier than an ordinary fan motor, is fastened to the upright and is from four to six horse-power. this connects with a flexible wire which transmits the power from the generating station, frequently several miles away. the auger, which is about the largest part of the machine and entirely out of proportion to the little motor that drives it, is simply a long bar of steel, twisted spirally at the cutting-end like an ordinary wood auger. from the workman's standpoint these rotary drills are infinitely superior to reciprocating or percussion drills, where the constant jarring of the machine, besides being extremely tiresome, sometimes produces the serious disease known as neuritis. various means have been attempted to prevent this, such as by overcoming the jar in a measure by flexible levers which do not transmit the vibrations to the hands and arms; but such attempts are only partially successful, and a certain amount of jarring cannot be avoided. in the rotary electric drills there is none of this, the workmen simply controlling the drill and the motor with levers, and receiving at most only a slight jar from the vibrations of the auger. traction in mining in recent years electric traction engines for use in mines have been rapidly replacing horse-and mule-power, and have become important economic factors in mining operations. the pioneer of this type of locomotive seems to have been one built by mr. w. m. schlessinger for one of the collieries of the pennsylvania railroad about 1882, and which has remained in active use ever since. the total weight of this locomotive was five tons and it was equipped with thirty-two horse-power electric motors. the current was supplied through a trolley pole which took the current from a t-shaped rail placed above and at one side of the track. the train hauled by this locomotive consisted of fifteen cars, carrying from two to three tons of coal each. following this first mining-locomotive a great number were quickly produced. in pennsylvania alone something like four hundred are now in use, and in illinois two million tons of coal were hauled in this manner in twelve mines in 1901. it was estimated at the beginning of the present century that some 3,000 electric locomotives specially built for mining were in use in the united states alone. the earlier types of mining-locomotives were much higher and bulkier than those of more recent construction, the motors being mounted above the trucks and geared downward. very soon, however, the "turtle-back" or "terrapin-back" type was developed, with the motors brought close to the ground, so that even quite a heavy locomotive might not be much higher than the diameter of its driving-wheels. when these queer-looking machines were boxed in so that even the wheels were covered, they lost all resemblance to locomotives or vehicles of any kind, appearing like low, rectangular metal boxes placed upon the car tracks, that glided along the rails in some mysterious manner. the presence of the trolley pole helped to dispel this illusion, but in some instances this is wanting, the power being taken from a third rail. with these locomotives, some of them not more than two and a half feet high, it was possible to haul trains even in very low and narrow passages--much lower, in fact, than could be entered by the little mules used in former years. this in itself was revolutionary in its effects, as many thin veins were thus made workable. this type of low locomotive is the one that has come into general use throughout the world. such locomotives range in size from two to twenty tons, with wheel gauges from a foot and a half wide to the standard railway gauge of four feet, eight and a half inches. locomotives weighing more than twenty tons are not in general use on account of the small size of the mine entrances. in the ordinary types the motorman sits in front, controlling the locomotive with levers and mechanical brakes placed within easy reach, but sunk as low as possible. as a rule, the motors are geared to the truck axles, either inside or outside the locomotive frame. an overhead copper wire supplies the current by contact with a grooved trolley wheel mounted on the end of the regulation trolley pole. an electric headlight is used, and the ordinary speed attained by the compact motors is from six to ten miles an hour. the amount of work that can be performed by one of these little, flat, box-like locomotives is entirely out of proportion to its size. a 10-ton locomotive in a pennsylvania mine hauled about 150,000 tons of coal in a year at a cost of less than one-tenth of a cent per ton for repairs. the usual train was made up of thirty-five cars, each loaded with about 3,700 pounds of coal, which was hauled up a three-per-cent grade. the cost of such haulage was only about 2.76 cents per ton, as against 7.15 cents when hauled by mule-power. these figures may be considered representative, as other mines show similar results. [illustration: the locomotive "puffing billy" and a modern colliery trolley. this locomotive was constructed in 1813 at wylam colliery, england, by william hedley. it was entirely successful, and was in operation for almost half a century, up to the time of its removal in 1862 to the south kensington museum. the vertical cylinders and arrangement of walking beams for transmitting power are particularly interesting. the power was transmitted through cogged wheels to the rear axle, as is done with modern automobiles.] a particular advantage has been gained by the use of electric locomotives over older methods in the process of "gathering" the cars. in many coal mines, even when the main hauling is done by electricity, the gathering or collecting of cars from the working faces of the rooms was formerly done either by mule-power or by hand. in some low-veined mines, hand power alone was used, on account of the low roof. in such places, low, compressed-air locomotives were sometimes used; but these were very expensive. these have now been very generally replaced by "turtle-back" electric locomotives, operated at a distance from the main trolley wire by means of long, flexible cables, so geared that they can be paid out or coiled as desired. on the main line these locomotives take the current from the trolley wire by means of the trolley pole, but when the place for gathering is reached, the connection is made by means of the flexible cable, and the trolley pole fastened down so as not to be in the way. this allows the locomotive to push the little cars into the rooms far removed from the main line, with passages too low and narrow to allow the use of the trolley pole. by the time the last cars have been delivered the first cars of the train have been filled, and the process of gathering may be begun at once, and the loaded train made up for the return trip. with such a locomotive two men can distribute and gather up from one hundred to one hundred and twenty cars in an ordinary eight-hour working-day, hauling from three hundred to three hundred and fifty tons of coal. in certain regions, a system of third-rail current-supply is used, this rail being also a tooth rail with which a cog on the locomotive works frictionally. for climbing steep grades this system of cogged rails has many advantages over other systems. another type of electric locomotive used in some mines is a self-propelling or automobile one equipped with storage batteries. such locomotives do away with the inconvenience and dangers of contact rails or trolley wires, but are heavy and expensive. a compromise locomotive, particularly useful for gathering, is one equipped with both trolley pole and storage batteries. this locomotive is so made that the storage batteries are charged while it is running with the trolley connection, so that no time is lost in the charging process. such locomotives have been found very satisfactory for many purposes, and but for the imperfections common to all storage batteries would be ideal in many ways. they can be worked over any improvised track, regardless of distance, which is an advantage over the flexible-cable system where distances are limited by the length of cable; and the first cost of the battery is no more than the outlay on trolley wires and supports. it is also claimed that the cost of maintenance is relatively low, but it is doubtful if it equals the trolley or third-rail systems in this respect. closely allied to the systems of traction by electric locomotives, is the modern electric telpherage system. until quite recently the haulage of ores and other raw materials used in mining, when done aerially, has been by means of travelling rope or cable. when distances to be travelled in this manner are short, such as across streams or valleys, where no supports are used, the term "cableway" is generally applied; but where the distance is so long that supports are necessary, the term "tramway cable" is used. it is to these longer systems that electric telpherage is particularly applicable. the advantage of such an electric system over the older method is the same as the advantages of the trolley road over the cable, all ropes and cables being stationary, the electric motor, or "telpher," travelling along on one cable and taking its current by means of a trolley pole from a wire above. for heavier work metal rails supported between posts are employed in place of a flexible cable, and over such systems loads of several tons can be hauled. such an electric telpher system is used in one of the cuban limestone quarries, the telpher and cars travelling a long distance upon cables, except at some of the curves, where solid rails are substituted, hauling a load of a thousand pounds at a speed of from twelve to fifteen miles an hour. the current comes from a distant source, and the telpher is so arranged that it travels automatically when the current is turned on, stopping when the current is cut off. this is quite a common arrangement for smaller telphers, but in the larger ones a man travels with the telpher and load, controlling the train just as in the case of the ordinary trolley system. the various processes of hoisting in mines by electricity is closely akin to that of traction, since, after all, "an elevator is virtually a railway with a 100-per-cent grade." as such work is done spasmodically, long periods of rest intervening between actual periods of work, a great deal of energy is wasted by steam hoisting engines, where a certain pressure of steam in the boiler must be maintained at all times. for this reason electrical energy for hoisting has come rapidly into popularity in recent years. "the throttling of steam to control speed," said mr. f. o. blackwell in addressing the american institute of mining engineers, "the necessity for reversing the engine, the variation in steam pressure, the absence of condensing apparatus, the cooling and large clearance of cylinders, and the condensation and leakage of steam pipes when doing no work, are all against the steam hoisting engine. one of the largest hoisting engines in the world was recently tested and found to take sixty pounds of steam per indicated horse-power per hour. the electric motor, on the other hand, is ideal for intermittent work. it wastes absolutely no energy when at rest, there being no leakage or condensation. its efficiency is high, from one-quarter load to twice full load." there seems to be practically no difference as far as the element of danger is concerned between steam and electric hoists. the difference is largely one of economy. the importance of this is shown by the recent comparisons in a gold mine which has replaced its steam apparatus by electricity. in this mine the hoist moves through the shaft at a rate of over twelve hundred feet per minute, elevating five hundred tons of ore daily on double-decked cages. it is estimated that this system shows an efficiency of 75 per cent, taking into account losses of all kinds, with a resulting reduction of cost of from seven to twenty dollars per horse-power per month. results comparing very favorably with these have been obtained also in some of the mines in germany and bohemia, where electricity has been introduced extensively in mining. in one of these mines the daily hoisting capacity is twenty-seven hundred tons from a depth of over sixteen hundred feet, at a speed of over fifty-two feet per second. in the comstock mine, at virginia city, nev., electric hoists are used which obtain their power from a plant situated on the truchee river thirty-two miles away. electric mining pumps in pumping, which is always one of the important items in mining, the use of electric power has been found quite as advantageous as in the other fields of its application. no special features are embodied in most of the types of mining pumps over the rotary and reciprocating types used for ordinary purposes, except perhaps a type of pump known as the sinking pump. this is a movable pump that can be easily lowered from one place to another, and has proved to be a great time-saver over steam or air pumps used for similar purposes. for some time the question of the durability of electric pumps was in dispute, but developments in quite recent years seem to prove that, in some instances at least, such pumps are practically indestructible. "the question of what would happen to an electric motor in a mine if pumps and motors get flooded has often come up. from tests made recently at the university of liège, belgium, it appears that a suitably designed polyphase alternating-current motor of a type largely used on the continent of europe was completely submerged in water. it was run for a quarter of an hour; it was then stopped and allowed to remain submerged, under official seal, for twenty-four hours, at the end of which time it was again run for a few minutes. it was next removed from the water, again put under seal, and left to dry for twenty-four hours. the insulation was then tested, and the motor was found to be in perfect order. it would be hard to imagine a test more severe than this. "as bearing upon this question it is interesting to note that among the pumps in use around johannesburg, south africa, at the beginning of the anglo-boer war, there were twelve of a well-known american make, each of which was operated by a 50-horse-power induction motor of american construction with three 15-kilowatt transformers. when the mines were shut down, upon the breaking out of the war, the water rose so rapidly that it was impossible to remove the pumps, motors, transformers, etc., and consequently they remained under 500 to 1,000 feet of water. two and a half years later, when peace was declared in south africa, the water in the shaft was pumped out and the electrical apparatus was removed to the surface. three of the motors were stripped and completely rewound, but to the general surprise of the experts the condition of the insulation indicated that the rewinding might not be absolutely necessary. accordingly the other nine motors were thoroughly dried in an oven and then soaked in oil. after this treatment they were rigidly tested, proved to be all right, and were at once restored to regular service in the mine. the transformers were treated in the same manner as the motors, with equally gratifying results. "an interesting illustration of the flexibility and adaptability of electric motors for pumping purposes is furnished by the gneisenau mine, near dortmund, germany, where a very large electric mining plant was installed in 1903. in this instance the pump is located more than 1,200 feet below the surface, and the difficulties of installing the apparatus were so great, on account of the small cross section of the shaft, that it was necessary to build up the motor in the pumping chamber, the material being transported through the wet shaft and the winding of the coils being performed _in situ_. "an interesting use of the electric pump associated with the telephone in connection with mining is noted by mr. w. b. clarke. in one coal mine, where an electric pump is located in a worked-out portion of the mine, the circuits are so arranged that the pump is started from the power house, some distance away. near the pump is placed a telephone transmitter connected to a receiver in the power house. to start the motors, or to ascertain whether the pumps are working properly, the engineer merely listens at the telephone receiver, without leaving his post." electricity in coal mining in coal mining the effect of the use of electrical machinery has been revolutionary in recent years, particularly in the development of electric coal cutters. the old method of picking out coal by hand, where the miner labored with the heavy pick, working in all manner of cramped and dangerous positions, was supplanted a few years ago by the "puncher" machine, worked by steam or compressed air. with these machines the coal was picked out just as in the case of the hand method, except that the energy was derived from some power other than muscular. so that while these machines worked more rapidly than the hand picks, they utilized the same general principle in applying their energy. within recent years, however, various coal-cutting machines have been devised, with which the coal was actually cut, or sawed out, these machines being peculiarly well adapted to using the electric current. the most practical and popular form of machine is one in which the sawing is done by an endless chain, the links of which are provided with a cutting blade. these have been very generally replacing the compressed-air or pick type of machine, and their popularity accounts largely for the enormous increase in the use of coal-mining machinery during the past decade. thus in 1898 there were 2,622 coal-mining machines in use in the united states. four years later this number had more than doubled, the increase being due largely to the adoption of chain machines. like electric locomotives, and for similar reasons, the coal-cutting machines are low, broad, flat machines, from eighteen to twenty-eight inches high. they rest upon a flat shoeboard that can be moved easily along the face of the coal. an ordinary machine weighs in the neighborhood of a ton, and requires two men to operate. the apparatus is described briefly as follows: "on an outside frame, consisting of two steel channel bars and two angle irons riveted to steel cross ties, rests a sliding frame consisting of a heavy channel or centre rail, to which is bolted the cutter head. the cutter head is made entirely of two milled steel plates, which bolt together, forming the front guide for the cutter chain. this chain, which is made of solid cast steel links connected by drop forge straps, is carried around idlers or sprockets placed at each end of the cutter head and along the chain guides at the side to the rear of the machine, where it engages with and receives its power from a third sprocket, under the motor. the electric motor, which is of ironclad multipolar type, rests upon a steel carriage, which forms the bearing for the main shaft.... a reversing switch is provided, so that the truck can travel in either direction, and when the machine has reached its stopping point, either forward or backward, it is checked by an automatic cut-off. the return travel is made in about one-fourth of the time required to make the cut." in veins of coal of a thickness from twenty-eight to thirty inches, such a machine will cut about one hundred tons of coal in a day. the cost of production with such machines has been estimated at about sixty-three cents a ton, as against ninety cents as the cost of pick mining in rooms,--a saving of about twenty-seven cents a ton. since it is estimated that for a cost of $10,000 an electrical equipment can be installed capable of working four such machines besides affording power for lighting, pumping, ventilation of the mine, etc., thus saving something like $100 a day for the operator, the great popularity of these machines is readily understood. after such a machine has been placed in position, a cut some four feet wide, four or five inches high, and six feet deep can be made in five minutes, with the expenditure of very little energy on the part of the workmen. one of the largest cuttings ever recorded by one of these machines is 1,700 square feet in nine and one-half hours, although this may have been exceeded and not recorded. among the several advantages claimed for the chain machine over the older pick machines is the small amount of slack coal produced, and the absence of the racking vibrations that exhaust the workmen, and, like the air drills, sometimes cause serious diseases. on the other hand the advocates of the pick machines point out that they can be used in mines too narrow for the introduction of chain machines. they show also that there is a constant element of danger from motor-driven machines in mines where the quantity of gas present makes it necessary to use safety lamps, on account of the sparking of the machines which may produce explosions. both these claims are valid, but apply only to special cases, or to certain mines, and do not affect the general popularity of the chain machines. there are several different types of chain cutting machines, such as "long-wall machines," and "shearing machines," but these need not be considered in detail here. the general principle upon which they work is the same as the ordinary chain machine, the difference being in the method of applying it for use in special situations. electric lighting of mines for many obvious reasons the ideal light for mining purposes is one in which the danger from the open flame is avoided, particularly in well-ventilated mines, or mines under careful supervision, where the danger from inflammable gases is slight. the incandescent electric light, therefore, has become practically indispensable in modern mining operations. for certain purposes and in certain locations where an intense light is desirable and where there is no danger from combustible gases, arc lights are used to a limited extent. but there is constant danger from the open flame in using such lights, and also from the connecting wires leading to them. furthermore, such intense light is not usually necessary in the narrow passages of the mine. to be sure, there is a certain element of danger even with incandescent lights on account of the possibility of breakage of the globes, and of short-circuiting where improper wiring has been done. to overcome as much as possible the dangers from these sources, special precautions are taken in wiring mines, and special bulbs are used. in general the incandescent lamps as used in mining are made of stout round bulbs of thick glass which are not likely to crack from the effects of water dripping upon them while heated. as a further protection it is customary to enclose the bulbs in wire cages. it is also customary to use low-current lamps with a rather high voltage, although this must be limited, as excessive voltage may in itself become a source of danger. xiii the age of steel the iron industry has of late years become more and more merged into the steel industry, as steel has been gradually replacing the parent metal in nearly every field of its former usefulness. steel is so much superior to iron for almost every purpose and the process of making it has been so simplified by bessemer's discovery that it may justly be said that civilization has emerged from the iron age, and entered the age of steel. while iron is mined more extensively now than at any time in the history of the world, the ultimate object of most of this mining is to produce material for manufacturing steel. we still speak of boiler iron, railroad iron, iron ships, etc., but these names are reminiscent, for in the construction of modern boilers and modern ships, steel is used exclusively. in the past decade it is probable that no railroad rails even for the smallest and cheapest of tracks have been made of anything but steel. the last half of the nineteenth century has been one of triumph of steel manufacture and production in america, and at the present time the united states stands head and shoulders above any other nation in this industry. in the middle of the century both germany and england were greater producers than america; but by the close of the century the annual output in the united states was above fifteen million tons as against england's ten and germany's seven; and since 1900 this lead has been greatly increased. the steel industry has become so great, in fact, that it is "a sort of barometer of trade and national progress." the great advances in the quantity of steel produced have been made possible by corresponding advances in methods of winning the iron ore from the earth. mining machinery has been revolutionized at least twice during the last half century, first by improved machines driven by steam, and again by electricity and compressed air. ore is still mined to a limited extent by men with picks and shovels, but these implements now play so insignificant a part in the process that they cannot be considered as important factors. steam shovels, automatic loaders and unloaders, dynamite and blasting powder, have taken the place of brawn and muscle, which is now mostly expended in directing and guiding mining machinery rather than in actually handling the ore. the lake superior mines at the present time the greatest iron-ore fields lie in the lake superior region, and it is in this region that the greatest progress in mining methods has been made in recent years. there are, of course, extensive mines in other sections of the united states, but at least three-quarters of all the iron produced in america comes from the lake superior mines, and the systems of mining pursued there may be considered as representative of the most advanced modern methods. where the iron ore of these mines is found near the surface of the earth, the great system of "open-pit" mining is practised; but as only a relatively small portion of the ore is so situated, modifications of older mining methods are still employed. of these the three most important are known as "overhead scooping," "caving," and "milling." in the overhead method a shaft is sunk into the earth to a depth of several hundred feet, according to the depth of the ore, this shaft being lined with timbers for support. from this shaft horizontal tunnels are made in all directions in the ore deposits, and through these tunnels the ore is conveyed to the shaft and thence to the surface. as the ore is removed and the earth thus honeycombed in all directions, supports of various kinds must be made to prevent caving. for this purpose columns of the ore itself may be left, or supports of masonry or wood or steel may be introduced. under certain circumstances, however, these supports are not employed, the earth being allowed gradually to cave in at the surface as the ore is removed, this being the method of mining known as "caving." where the ore deposit occurs in a favorable hillside the "milling" system is frequently employed. in working this system a large horizontal tunnel, twenty or more feet in diameter, is dug into the hillside. perpendicular shafts are then sunk from the top of the hill, connected with openings leading directly into the top of the main horizontal shaft. by this arrangement the ore, when loosened in these perpendicular shafts, falls directly into the bins placed for its reception about the openings, or into the rows of cars in waiting to receive it. in this method dynamite and powder take the place of hand labor, the main mass of ore being dislodged and thrown into the shaft by blasting, instead of by hand labor. but all these methods are overshadowed in magnitude by the great "open pit" systems, where the ore is taken from the surface and handled entirely by machinery, the only part played by the miner's pick being that of assisting in loosing certain fragments so that they may be more easily seized by the machines. indeed, this system of mining partakes of the nature of quarrying rather than that of mining in the ordinary sense, the ore being scooped from the surface of the ground. one naturally thinks of a mine as being subterranean; but in the great open-pit mines in the lake superior region, which are the largest mines in the world, all the mining is done at the surface of the earth. it should not be understood, however, that in such mines nature has left the red iron ore exposed at the surface in any great quantities. on the contrary, it is usually covered by a layer of earth ranging from a yard to ten or more yards in depth, and this, of course, must be removed before open-pit methods can be practised. prospecting for such deposits is therefore just as necessary as in cases where the deposit is situated much deeper in the earth; and the business of prospecting by "test pit" men is as important an industry as ever. when an available open-pit mine of sufficient extent has been located the gigantic task of "stripping" or removing the overlying layer of earth begins. immense areas of land have been thus stripped in some of these undertakings, no difficulties being considered insurmountable. if a small river-bed lies in an unfavorable position, the course of the river is changed regardless of expense. farms and farm houses are purchased and literally carted away, neither land nor houses representing values worth considering when compared with the stratum of ore beneath them. the single contract for stripping one area in the lake superior region was let for a sum amounting to half a million dollars. as soon as a sufficiently large area has been stripped, railroads are constructed into the pit, steam shovels are run into place, and the actual work of mining begins. five shovels full make a car-load, and under ordinary circumstances the five loads may be delivered in as many minutes. the number of men required to manipulate one of these steam shovels is from ten to twelve. the ore itself is frequently so hard that the scoop of the shovel could not penetrate it until loosened and broken up, and it is the business of the gang of workmen to do this and slide the ore down within easy working distance of the shovel. this is mostly done by blasting with dynamite and powder, little of the actual labor being performed by hand. in blasting, a deep hole is first drilled into the ore near the top of the embankment, and into this hole a stick of dynamite is dropped and exploded. this enlarges the cavity sufficiently so that a quantity of blasting powder may be poured in and set off, tumbling the ore down within reach of the shovel. this ore is frequently almost as hard as iron itself, many of the pieces thus dislodged being too large for convenient handling, either by the steam shovel or in the chutes at the wharves, and must be still further broken up. this is sometimes done by the men with picks; but in mining on a large scale, where the deposit is all of a very hard nature, crushing machines are used. in this manner the steam shovel is kept constantly supplied with ore for the waiting train of cars. these trains are arranged on a track running parallel with the track from which the steam shovel operates, and at such a distance that the centre of the car will be directly under the opening in the bottom of the shovel when it is swung around on its crane. the engineer in charge of the locomotive drawing the train stops it in a position so that the first shovelful of ore will be dumped into the forward end of the first car. as each successive shovelful is deposited, representing about one-fifth of a car-load, the train is pulled or backed along the track about one-fifth of a car-length. in this manner it is only necessary for the steam shovel to be swung into the same position and dumped at the same point each time to insure the proper loading of the cars. from what has been said it will be seen that in this open-pit mining the steam engine and steam locomotive still play a conspicuous part; but in the other forms of iron mining, electric or compressed-air motors are used, as much better adapted for underground work. in the lake superior region, where everything is done by the most modern methods, the use of horses and mules for hauling purposes is practically unknown. the cars used for hauling the ore are of peculiar construction. the latest types are built of steel with a carrying capacity of fifty tons of ore, and are so made that by simply knocking loose a few pins their bottoms open and discharge the ore into the receiving bins on the wharves, or into the chutes leading to the waiting boats. a perennial problem in iron mining, whether surface or subterranean, just as in all other kinds of mining, is the removal of accumulations of water, some of these mines filling at the rate of from twenty-five to thirty thousand gallons an hour. but an equally important problem is that of removing moisture from the ore itself. obviously every additional pound of moisture adds to the cost and difficulty in handling, and inasmuch as this ore must be transported a distance of something like a thousand miles, necessitating three or four handlings in the process, the aggregate amount of wasted energy caused by each ton of water is enormous. it has been found that at least ten per cent of the moisture may be dried out of the ore before shipping, and that the ore does not tend to absorb moisture again under ordinary circumstances once it has been dried. this is of course of great advantage where it is found necessary to store it in heaps some little time before shipping. from mine to furnace in most industries, particularly where the percentage of waste products is large, it is found advantageous and economical to establish factories as near the source of supply of raw material as possible. but the iron ore mined in the lake superior region is transported something like a thousand miles before being delivered to the factories. the question naturally arises, why is not the ore turned into pig iron or steel ingots at once as near the mouths of the mines as possible, and sent in this condensed form to the factories, thus saving more than half the cost of transportation? the answer is simple: the coal mines and steel factories lie in the east, one established by nature, the other by man many years before iron ore was found in the lake region. and it is found just as cheap and easy to transport the iron to the coal regions as it would be to transport the coal to the ore regions. furthermore, the factories in the neighborhood of pittsburg and along the southern shores of lake erie and lake ontario are near the great centres of civilization, and are accessible the year round; while the lake superior region is "frozen in" for at least three months in the year. and so, in place of a great traffic of coal westward to the lake superior regions, there is a great eastward traffic of ore, by rail and water, passing from the mines to furnaces and factories a thousand miles away. indeed, this is probably the greatest and most remarkable system of transportation in the world. specially constructed trains, wharves, boats, and machinery, used for this single purpose, and not duplicated either in design or extent, make this stupendous enterprise a unique, as well as a purely american one. the transportation begins with the train loads of ore that run from the mines to the lake shore and out upon the wharves built to receive them. these wharves are enormous structures, sometimes half a mile in length, built up to about the height of the masts of ore boats. on the sides and in the centres of these towering structures are huge bins for holding the ore, these bins communicating directly with the holds of the ore steamers tied up alongside. four tracks are frequently laid on the top of the wharves, and are so arranged that trains four abreast can dump the ore into the bins, or waiting ships, at the same time. if the bins are empty and boats waiting to receive a cargo, the ore is discharged by long chutes into the holds from the cars. otherwise the bins are filled, the trains returning to the mines as quickly as possible for fresh loads. the boats for receiving this cargo are of special design, many of them differing very greatly in appearance from ordinary ocean liners of corresponding size. this is particularly true of the "whale-backs" which have little in common in appearance with ordinary steamers except in the matter of funnels; and even these are misplaced sternwards to a distance quite out of drawing with the length of the hull. their shape is that of the ordinary type of submarine boat--that is, cigar-shaped--this effect being obtained by a curved deck completely covering the place ordinarily occupied by a flat deck. a wheel-house, like a battle-ship's conning-tower, is placed well forward, supported on steel beams some distance above the curved deck for observation purposes; and engines, boilers, and coal bunkers occupy a small space in the stern. the boat, therefore, is mostly hold. but the "whale-backs" form only a small portion of the ore-fleet. the ordinary type of boat conforms more nearly to the shape of ocean boats, except that the bridge, wheel-house, and engines are located as in the whale-backs. the bows of these boats are blunt, the desideratum in such craft being hull-capacity rather than speed. for sea-worthiness they are equal to any ocean boats, as the battering waves of lake superior are quite as powerful and even more treacherous than those of the atlantic or pacific. some of these boats are five hundred feet long, equal to all but the largest ocean vessels. their coal-carrying capacity is relatively small, since coaling stations are numerous at various points on the journey, and every available inch of space is utilized for the precious iron ore. in order to facilitate loading, the decks are literally honey-combed with hatches, some boats having fifteen or sixteen openings extending the width of the deck. by this arrangement the time of loading is reduced to a matter of a few hours, as a dozen chutes, each discharging several tons of ore per minute, soon fill the yawning compartments with the necessary six, eight, or nine thousand tons, that make up the cargo. quite recently lake-navigators have learned, what rivermen have long known, that cheap transportation may be effected on a large scale by barges and towing. before the outbreak of the civil war forty years ago, the mississippi river swarmed with great cargo-carrying steamers, employing armies of men and consuming enormous quantities of fuel. but after the war the experiment was tried of hauling the cargoes on barges towed by tug boats, and this proved to be so much cheaper that the fleet of great river boats soon disappeared. in somewhat the same way the barge has come into use of late years in the ore-traffic, and the great ore-steamers now tow behind them one or two barges equal in carrying capacity to themselves. in this way three ships' cargoes of ore are transported a thousand miles by a score of men, a dozen on the steamer and three or four on each of the barges. the barges themselves are rigged as ships, and if necessary can shift for themselves by means of sails attached to their stubby masts. but these are used only on special and unusual occasions, as in case of accidental parting of the hawsers during a storm. the problem of loading the ships at the ore wharves is a simple one as compared with the equally important one of transferring the ore from the hold to trains of cars in waiting at the eastern end of the water route. for four handlings of the ore are necessary before it is finally deposited in the furnaces in the east. the first of these is from the mine to cars; the second from the cars to the boats; the third from the boats to cars; and the fourth from the cars to the blast furnaces. for many years about the only hand work done in any of these processes was that of transferring from the boats to the ore-trains, and even here "automatic unloaders" are now rapidly supplanting the tedious hand method. by the older methods a travelling crane, or swinging derrick, dropped a bucket into the hold of the ore-vessel, where workmen shovelled it full of the red ore. it was then lifted out by machinery and the contents dumped into cars in much the same manner as that of the steam shovel in the mines. recently, however, a machine has been perfected which scoops up the ore from the ship's hold and transfers it to the cars without the aid of shovellers. the only human aid given this gigantic machine is to guide it by means of controlling levers--to furnish brains for it, in short--the "muscle" being furnished by steam power. the great arm of this automatic unloader, resembling the sweep of the old-fashioned well in principle, moves up and down, burying the jaws of the shovel into the ore in the hold, and pulling them out again filled with ore, with monotonous regularity, quickly emptying the vessel under the guidance of half a dozen men, and performing the labor of hundreds. thus the last field of activity for the laborer and his shovel, in the iron-ore industry, has been usurped by mechanical devices. from the time the ore is taken from the mine until it appears as molten metal from the furnaces, it is not touched except by mechanisms driven by steam, compressed air, or electricity. and yet, so rapid is the growth of the iron and steel industry that there is almost always a demand for more workmen. for this reason, and perhaps because of the "american spirit" among workmen, innovations in the way of labor-saving machinery are not resisted among the mine laborers. the american workman seldom resists or attacks machinery on the ground that it "throws him out of a job," as does his english cousin. it would be unjust to attribute this attitude to superior acumen on the part of the american workman, and it is probably a difference in conditions and surroundings that accounts for the diametrically opposite views held by laborers on the two sides of the atlantic. but after all, results must speak for themselves, and the advantage all lies in favor of the progressive attitude of the western laborer, if we may judge by the relative social status and financial standing of european and american workmen. the conversion of iron ore into iron and steel since steel is a compound substance composed essentially of two elementary substances in varying proportions, it appears that the name "steel," like wood, refers to a class of which there are several varieties. this, of course, is the case, but for the moment we may consider steel as a single substance composed chiefly of iron and containing a certain percentage of carbon. in this respect it resembles cast iron, steel having a smaller amount of carbon. wrought iron, on the other hand, contains no carbon at all, or at least only a trace of it. but whatever the ultimate destiny of iron ore--whether it is to become aristocratic manganese steel, or plebeian cast iron--it must first pass through certain processes before being "converted." to extract the pure iron from the iron ore it is necessary to heat the ore in a furnace containing a certain quantity of coal, coke, or charcoal, and limestone. the furnaces used in this process are known as blast-furnaces, and in these about one ton of iron is extracted for every two tons of lake superior ore, one and a quarter tons of coke, and half a ton of limestone used. these quantities are by no means constant, of course, but they may be taken as representing roughly the relative amounts of material that must be fed into the furnaces. like everything else in the world of iron and steel, these blast-furnaces have undergone revolutionary improvements during the past quarter of a century. from being most dangerous and destructive structures causing frightful loss of life and producing only about one ton of iron a day for every man working about them, as formerly, they have now become relatively harmless monsters, capable of turning out six times that quantity of ore for each man employed. the older blast-furnace was a huge, chimney-like structure, perhaps a hundred feet high, into which the ore, coal, and limestone were poured. most of the work about these furnaces was done by manual labor, or at least manual labor was an active assistant to the machinery used in manipulating the furnaces. the top of the furnace was closed in by a great movable lid, or "bell," and the material for charging it was hauled up the sides by elevators and dumped in at the top. about the top of the furnace was constructed a staging upon which the workmen stood, an elevator shaft connecting the staging with the ground. the ore and other materials were brought to the foot of the shaft on cars from which it was shovelled into peculiarly designed wheelbarrows, trundled to the elevator, and hauled to the top. in order to dump the wheelbarrow loads into the furnaces it was necessary to raise the bell. this was always dangerous, and frequently resulted in the suffocation or injury of the workmen on the staging. for when the bell was raised there was an escape of poisonous gases, which might flare out in a sheet of flame, with the possibility of burning or suffocating the workmen. the fumes from these gases, if inhaled in small quantities, might simply cause coughing, hiccoughing, or dizziness; but when inhaled in large quantities they struck down a man like the fumes of chloroform, suffocating him in a few seconds if he was not removed at once into a purer atmosphere. indeed, the likelihood of this was so great that at many of these furnaces a special workman was detailed to take the position on the staging, well out of range of the gas, his sole duty being to rescue any of the men who might be overcome, and hurry them as quickly as possible down the elevator shaft into the pure atmosphere below. it was not an uncommon thing in the neighborhood of these older furnaces to see stretched about on the ground at the base several workmen in various stages of suffocation. fortunately, by use of precautionary measures, fatal accidents were rather unusual, the men being overcome only temporarily, and usually recovering quickly and returning to work. but the poisonous gas coming from the top of the furnace was not the only, nor the worst, danger constantly menacing the men on the staging. their greatest dread was the possibility of explosions occurring in the furnace, which might hurl the bell into the air and deluge the upper structure with molten metal. against this possibility there was no safeguard in the older furnaces, explosions occurring without warning and frequently with terrible effects. but fortunately these older types of furnaces are being rapidly replaced by the newer forms in which the danger to life, at least from gas and explosions, is minimized. and even in the older furnaces, improvements in the structure of the bell and in methods of filling have greatly lessened the dangers. in the modern type of blast-furnace the work at the top formerly performed by men on the staging is accomplished entirely by machinery. the general appearance of these furnaces is that of huge iron pipes or kettles mounted on several iron legs. the outer structure, or shaft, is constructed of plate iron, but this is lined with fire brick of considerable thickness, and may have a water jacket interposed between these bricks and the shaft. about this large kettle are smaller kettles of somewhat similar shape having pipes leading from their tops to the larger structure. these smaller kettles are the "stoves" used in producing the hot air for the furnace. the working capacity of some of these furnaces is in the neighborhood of a thousand tons of iron a day, although the average furnace produces only about half that quantity. the powerful machinery used for charging these monster caldrons hauls the ore and other charging materials to the top and dumps it in car-load lots. in the older methods of manufacturing steel, the contents of the blast-furnaces were first drawn off into molds and allowed to cool into what is known as pig-iron. it was then necessary to re-heat this iron and treat it by the various methods for producing the kind of steel desired. by the newer methods, however, time and money are saved by converting the liquid iron from the blast-furnace directly into steel without going through the transitional stage of cooling it into pigs. pigs of iron are still made in enormous quantities, to be sure, but mostly for shipment to distant places or for stores as stock material. for statistical purposes, however, the entire product of the blast-furnace, whether liquid or solid, is known as "pig iron." the older method of removing the iron from the blast furnaces was by tapping at the opening near the bottom, the stream of liquid iron being allowed to flow into a connected series of sand molds, each mold being about three feet long by three or four inches wide. the bottom of these molds was flat but as the metal cooled in them the upper surface became round in shape, assuming a fanciful resemblance to a pig's back. in this molding a great amount of time was wasted in the slow process of cooling, and a large expenditure of energy wasted in this handling and re-handling of the metal. in modern smelting works, however, pigs are no longer cast in sand molds, the molten metal from the furnace being discharged directly into iron molds attached to an endless chain. these molds are long, narrow, and shallow, having the general shape of sand molds. each mold as it passes beneath the opening in the furnace remains just long enough to receive the requisite amount of metal to fill it, and then moves on to a point where it is either sprayed with water, or cooled by actually passing through a tank of water, emerging from this bath with the metal sufficiently solidified so that it may be dropped into a waiting car at the turning point of the endless chain. in this manner the charge from the blast-furnace may be drawn, cooled, and converted into pigs, loaded into cars, and hauled away without extra handlings or loss of time, the whole process occupying practically no more time than the initial step of tapping by the older method. where the contents of the blast-furnace are to be converted into steel at once, the molten metal is run off into movable tanks which carry it directly to the steel furnaces. these tanks, holding perhaps twenty tons of metal, are made of thick iron lined with fire brick, and arranged on low, flat cars designed specially for the purpose. these tanks are run under the spout of the furnace, filled with molten metal, and drawn to the steel works, possibly five miles away. as a rule, the distance is much less, but as far as the condition of the metal is concerned distance seems to make little difference, as even at the extreme distance there is no apparent cooling of the seething mass. the intense heat given off by these trains necessitates specially constructed cars, tracks, bridges, and crossings. the destination of this train load of iron pots is the "mixer"--a great 200-ton kettle in which the products from the various furnaces are mixed and rendered uniform in quality. on the arrival of the train at the mixer, titanic machinery seizes the twenty-ton pots and dumps their contents bodily into the glowing pool in the great crucible. like the filling process, this operation occupies only a few minutes. from the mixer the metal is poured out into ladles and transferred immediately to the "converter"--the important development of sir henry bessemer's discovery that has made possible the modern steel industry. this converter resembles in shape some of the old mortars used in the american civil war--barrel-shaped structures suspended vertically by trunnions at the middle and having an opening at the top. into this opening at the top the metal from the mixer is poured and when the converter has been sufficiently charged a blast of cooled air is blown in at the bottom through the molten metal. this blast emerges at the top as a long roaring flame, of a red color at first but gradually changing into white, and then faint blue. these changes in color are indicative of the changes that are taking place in the metal, and the appearance of a certain shade of color indicates that the conversion into steel is complete, and that it is time for shutting off the blast of air. any mistake in this matter--even the variation of thirty seconds' time--means a loss of thousands of dollars in the quality of steel produced. the man whose duty it is to determine this important point, therefore, holds an exceptionally delicate and responsible position, and receives pay accordingly. in deciding the exact moment when the blast shall be turned off, this workman is guided entirely by the sense of sight. mounted on a platform commanding the best possible view of the mouth of the converter and wearing green glass goggles of special construction, this man watches the change of color in the flame until a certain shade is reached--a shade that to the ordinary untrained observer does not differ in appearance from that of a moment before--when he gives the signal to shut off the blast. when this signal is given the contents of the converter is no longer common-place cast iron, but steel, ready to be molded into rails, boilers, or a thousand and one other useful things. the contents of the converter may now be drawn off as liquid steel into molds of any desired shape and size, and when cooled will be ready for shipment. but in the great steel factories the metal is not ordinarily allowed to cool completely before being sent to the rolling mills, being drawn off into molds placed along the surface of small, flat cars. these molds are rectangular, ordinarily four or five feet high by less than two feet in diameter. the metal is poured into openings in the top of each mold, and allowed to cool, solidify, and to contract enough to permit the outer casings of the molds to be pulled off by machinery, leaving the glowing "ingots" of steel ready for molding by machinery in the mills. the process just described is the one by which "bessemer steel" is made. there is another important process in use, the "open hearth" method, which differs considerably from this; but before considering this process something more should be said of the man whose discoveries made possible the modern steel industry. sir henry bessemer in the history of the progress of science and invention some one great name is usually pre-eminently associated with epoch-marking advances, although there may be a cluster of important but minor associates. this is true in the history of the modern steel industry, and the central name here is that of sir henry bessemer. bessemer was born at charlton, england, on jan. 19, 1813. always of an inventive turn of mind, his attention was first directed to improving the methods then in use for the manufacture of steel, while experimenting with the manufacture of guns. after several years of experimenting in his little iron works near london, he reached some definite results which he announced to the british association in 1856. in this paper he described a process of converting cast iron into steel by removing the excess of carbon in the molten metal by a blast of air driven through it. this paper, in short, described the general principles still employed in the bessemer process of manufacturing steel. and although the first simple process described by bessemer has been modified and supplemented in recent years, it was in this paper that the process which placed steel upon the market as a comparatively cheap, and infinitely superior, substitute for ordinary iron, was first disclosed. this famous paper before the british association aroused great interest among the english ironmasters, and applications for licenses to use the new process were made at once by several firms. but the success attained by these firms was anything but satisfactory, although bessemer himself was soon able to manufacture an entirely satisfactory product. the disappointed ironmasters, therefore, returned to the earlier processes, the inventor himself being about the only practical ironmaster who persisted in using it. recognizing the defects in his process, bessemer set about overcoming them, and at the end of two years he had so succeeded in perfecting his methods that his product, equal in every respect to that of the older process, could be manufactured at a great saving of time and money. but the ironmasters were now skeptical, and refused to be again inveigled into applying for licenses. bessemer, therefore, with the aid of friends, erected extensive steel works of his own at sheffield, and began manufacturing steel in open competition with the other steel operators. the price at which he was able to sell his product and realize a profit was so much below the actual cost of manufacture by the older process, that there was soon consternation in the ranks of his rivals. for when it became known that the firm of henry bessemer & co. was selling steel at a price something like one hundred dollars a ton less than the ordinary market price, there was but one thing left for the ironmasters to do--surrender, and apply for licenses to be allowed to use the new process. by this means, and through the profits of his own establishment, bessemer eventually amassed a well-earned fortune. moreover, he was honored in due course by a fellowship in the royal society, and knighted by his government. one other name is usually associated with that of bessemer in the practical development of the inventor's original idea. that is the name of robert mushet, and the "bessemer-mushet" process is still in use. mushet's improvement over bessemer's original process was that of adding a certain quantity of _spiegeleisen_, or iron containing manganese, which, for some reason not well understood, simplifies the process of steel making. mushet, therefore, must be considered as the discoverer of a useful, though not an absolutely essential, accessory to the bessemer process. open-hearth method in the open-hearth method the metal from the blast-furnaces is not sent to the converter, but is poured into oven-like structures built of fire brick, and in these heated to a terrific temperature. this heat has the same effect upon the metal as the blast of air in the bessemer converter, and this open-hearth process has become very popular for manufacturing certain kinds of steel. while in the method of application this process differs greatly from that of bessemer, it differs largely in the fact that the oxygen necessary to burn off the carbonic oxide, silicon, etc., is made to play over the molten mass instead of passing through it. it has been noted that the old type of blast-furnace gave off great quantities of combustible gases which became waste products. even gases containing something like 20 or 25 per cent. of carbonic acid may be highly inflammable, and thus an enormous quantity of valuable fuel was constantly wasted. in some furnaces, to be sure, they were put to practical use for heating the blast, but as the quantities given off were greatly in excess of the amount necessary for this purpose, there was a constant loss even with such furnaces. quite recently it has been found that the gases can be used directly in gas engines, developing three or four times as much energy in this way as if they were used as fuel under ordinary steam boilers. these engines are now used for operating the rolling-mill machinery, and the machinery of shops adjoining the furnaces, which, however, must not be situated at any very great distances from the furnaces. this accounts partly for the grouping together of blast-furnaces, rolling mills, and machine shops, the economical feature of this arrangement being so great that segregated establishments find it next to impossible to compete in the open market with such "communities" under the conditions prevailing in the steel industry. alloy steels the introduction of krupp steel, or nickel, for armor plates, a few years ago, called attention in a popular way to the fact that for certain purposes pure steel--that is, iron plus a certain quantity of carbon--was not as useful as an alloy of steel with some other metal. an alloy was a great improvement over ordinary steel or iron plates used in warfare; but in the more peaceful pursuits, as well as in warfare, certain alloyed steels, such as chrome steel, tungsten steel, and manganese steel play a very important part. chrome steel, for example, in the form of projectiles, is the most dreaded enemy of nickel-steel armor plates, because of the hardness and elasticity of armor-piercing projectiles made of it. such a steel contains about two per cent. of chromium with about one or two per cent. of carbon, which when suddenly cooled is extremely hard and tough. this kind of steel and manganese steel are the best guards against the burglar and safe-blower, as they resist even very highly tempered and hardened drills. as this steel is relatively cheap to manufacture, it is frequently used in the construction of safes and burglar-proof gratings. for this purpose, however, it is sometimes combined in alternate layers with soft wrought iron, the steel resisting the point of the drill, while the iron furnishes the necessary elasticity to resist the blows of the sledge. the bars used in modern jails and prisons are often made in a similar manner of alternate sheaths of iron and chrome steel. against the time-honored "hack-saw," the bugbear of prison officials for generations, such bars an inch and a quarter in diameter offer an almost insurmountable obstacle; and they are equally effective against a heavy sledge hammer. at least one case is recorded in which the use of these "composite" bars resulted in a disastrous fire in a prison. a small blaze having started in the basement of this prison, attempts to reach it with a stream of water were defeated by the bars of the steel gratings at the windows, which would not admit the nozzle of the hose. a corps of men armed with hack-saws, crow-bars, and sledges attacked this grating, which, if made of ordinary steel, could have been readily broken. but against these composite bars they produced no appreciable effect. meanwhile the fire gained rapidly, threatening the building and its eight hundred inmates, and was only checked after holes had been made through fire-proof floors and ceilings for admitting the nozzle. manganese steel is peculiar in becoming ductile by sudden cooling, and brittle on cooling slowly--precisely the reverse of ordinary steel. it contains about 1.50 per cent. of carbon, and about 12 per cent. of manganese. if a small quantity of manganese, that is, 1 or 2 per cent., is used the steel is very brittle, and becomes more so as greater quantities of the manganese are used, up to about 5 per cent. from that point, however, it becomes more ductile as the quantity of manganese is increased, until at about 12 per cent. it reaches an ideal state. when used for safes and money vaults this steel has one great advantage over chrome steel--it is not affected by heat. by using a blow-pipe and heating a limited area of steel, the burglar is able to "draw the temper" of ordinary steel to a sufficient depth so that he can drill a hole to admit a charge of dynamite; but manganese steel retains its temper under the blow-pipe no matter how long it may be applied. against attacks of the sledge, however, it is probably inferior to chrome steel. like manganese steel, tungsten steel retains its temper even when heated to high temperatures. for this reason it is used frequently in making tools for metal-lathe work where thick slices of iron are to be cut, as even at red heat such a tool continues to cut off metal chips as readily as when kept at a lower temperature. this steel contains from 6 to 10 per cent. of tungsten, a metallic element with which we have previously made acquaintance in our studies of the incandescent lamp. xiv some recent triumphs of applied science not long ago a little company of men met in a lecture hall of columbia university to discuss certain questions in applied science. it was a small gathering, and its proceedings were so unspectacular as to be esteemed worth only a few lines of newspaper space. the very name--"society of electro-chemistry"--seemed to mark it as having to do with things that are caviar to the general. the name seems to smack of fumes of the laboratory, far removed from the interests of the man in the street. yet professor chandler said in his address of welcome to the members of the society, that though theirs was the very youngest of scientific organizations, he could confidently predict for it a future position outranking that of all its sister societies; and his prediction was based on the belief that electro-chemistry is destined to revolutionize vast and important departments of modern industry. a majority of the heat-using methods of mechanics will owe their future development to the new science. in a word, then, despite its repellent name, the society in question has to do with affairs that are of the utmost importance to the man in the street. though its members may sometimes deal in occult formulas and abstruse calculations, yet the final goal of their studies has to do not with abstractions but with practicalities,--with the saving of fuel, the smelting of metals, the manufacture of commodities. but theory in the main must precede practice--the child creeps before it walks. "the later developments of industrial chemistry," says sir william ramsey, "owe their success entirely to the growth of chemical theory; and it is obvious," he adds significantly, "that that nation which possesses the most competent chemists, theoretical and practical, is destined to succeed in the competition with other nations for commercial supremacy and all its concomitant advantages." fortunately this interdependence of science and industry is not a mere matter of prophecy--for the future tense is never quite so satisfying as the present. vastly important changes have already been accomplished; old industries have been revolutionized, and new industries created. the commercial world of to-day owes vast debts to the new science. professor chandler outlined the character of one or two of these in the address just referred to. he cited in some detail, for example, the difference between old methods and new in such an industry as the manufacture of caustic soda. he painted a vivid word picture of the distressing conditions under which soda was produced in the old-time factories. salt and sulphuric acid were combined to produce sulphate of soda, which was mixed with lime and coal and heated in a reverberatory furnace. each phase of the process was laborious. the workmen operating the furnaces sweltered all day long in an almost unbearable atmosphere--stripped to the waist, dripping with perspiration, sometimes overcome with heat. their task was one of the most trying to which a man could be subjected. but to-day, in such establishments as the soda manufactories at niagara falls, all this is changed. a salt solution circulates continuously in retorts where it can be acted upon by electricity supplied from dynamos operated by the waters of the niagara river. the workmen, comfortably dressed and moving about in a normal temperature, have really nothing to do but refill the retorts now and then and remove the finished product. "it almost seems," professor chandler added with a smile, "as if workmen ought to be glad to pay for the privilege of participating in so pleasant an occupation. at all events it is, in all seriousness, a pleasure for the visitor who knows nothing of old practices to witness this triumph of a modern scientific method." even more interesting, said professor chandler, are the processes employed in the modern method of producing the metal aluminum by the electrolytic process. the process is based on the discovery made by mr. charles m. hall while he was a student working in a college laboratory, that the mineral cryolite will absorb alumina to the extent of twenty-five per cent. of its bulk, as a sponge absorbs water. the solution of this compound is then acted on by electricity, and the aluminum is deposited as pure metal. a curiously interesting practical detail of the process is based on the fact that pulverized coke remains perfectly dry and rises to the surface when stirred into a crucible containing the hot alumina solution: moreover, it rises to the surface and remains there as a shield to protect the workmen against the heat of the solution. it serves yet another purpose, as the powdered alumina may be sifted upon it and left there to dry before being stirred into the crucible. a most ingenious yet simple device tells the workman when any particular crucible is in need of replenishing. a small, ordinary, incandescent electric-light bulb is placed in circuit between the poles that convey the electric current through the alumina solution. so long as the crucible contains alumina, the bulb does not glow, because twenty volts of electricity are required to make it incandescent, whereas seven volts pass through the solution. but so soon as the alumina becomes exhausted, resistance to the current rises in the cryolite solution and, as it were, dams back the electric current until it overflows into the wire at sufficient pressure to start the signal lamp. then it is necessary merely for a workman to stir into the solution the dry alumina resting on the surface, along with the coke that supports it. this, of course, reestablishes the electrolytic process; the lamp goes out and the coke, unaffected by its bath, rises to the surface to support a fresh supply of alumina. such a process as this, contrasted with the usual methods of smelting metals in fiercely heated furnaces, seems altogether wonderful. here a pure metal is extracted from the clayey earth of which it formed a part, without being melted or subjected to any of the familiar processes of the picturesque, but costly, laborious, and even dangerous, blast-furnaces. there is no glare and roar of fires; there are no showers of sparks; there is no gush of fiery streams of molten metal. a silent and invisible electric current, generated by the fall of distant waters, does the work more expeditiously, more efficiently, and more cheaply than it could be done by any other method as yet discovered. fully to appreciate the importance of the method just outlined, we must reflect that aluminum is a metal combining in some measure the properties of silver, copper, and iron. it rivals copper as a conductor of electricity; like silver it is white in color and little subject to tarnishing; like iron it has great hardness and tensile strength. true, it does not fully compete with the more familiar metals in their respective fields; but it combines many valuable qualities in fair degree; and it has an added property of extreme lightness that is all its own. add to this the fact that aluminum is extremely abundant everywhere in nature--it is a constituent of nearly all soils and is computed to form about the twelfth part of the entire crust of the earth--whereas the other valuable metals are relatively rare, and it will appear that aluminum must be destined to play an important part in the mechanics of the future. there is every indication that the iron beds will begin to give out at no immeasurably distant day; but the supply of aluminum is absolutely inexhaustible. until now there has been no means known of extracting it cheaply from the clay of which it forms so important a constituent. but at last electro-chemistry has solved the problem; and aluminum is sure to take an important place among the industrial metals, even should it fall short of the preeminent position as "the metal of the future" that was once prematurely predicted for it. nitrogen from the air there is a curious suggestiveness about this finding of aluminum at our very door, so to speak, some scores of centuries after the relatively rare and inaccessible metals had been known and utilized by man. but there is another yet more striking instance of an abundant element which man needed, but knew not how to obtain until the science of our own day solved the problem of making it available. this is the case of the nitrogen of the air. as every one knows, this gas forms more than three-fourths of the bulk of the atmosphere. but, unlike the other chief constituent, oxygen, it is not directly available for the use of plants and animals. yet nitrogen is an absolutely essential constituent of the tissues of every living organism, vegetable and animal. any living thing from which it is withheld must die of starvation, though every other constituent of food be supplied without stint; and the fact that the starving organism is bathed perpetually in an inexhaustible sea of atmosphere chiefly composed of nitrogen would not abate by one jot the certainty of its doom. to be made available as food for plants (and thus indirectly as food for animals) nitrogen must be combined with some other element, to form a soluble salt. but unfortunately the atoms of nitrogen are very little prone to enter into such combinations; under all ordinary conditions they prefer a celibate existence. in every thunder-storm, however, a certain quantity of nitrogen is, through the agency of lightning, made to combine with the hydrogen of dissociated water-vapor, to form ammonia; and this ammonia, washed to the earth dissolved in rain drops, will in due course combine with constituents of the soil and become available as plant food. once made captive in this manner, the nitrogen atom may pass through many changes and vicissitudes before it is again freed and returned to the atmosphere. it may, for example, pass from the tissues of a plant to the tissues of a herbivorous animal and thence to help make up the substance of a carnivorous animal. as animal excreta or as residue of decaying flesh it may return to the soil, to form the chief constituent of a guano bed, or of a nitrate bed,--in which latter case it has combined with lime or sodium to form a rocky stratum of the earth's crust that may not be disturbed for untold ages. a moment's reflection on the conditions that govern vegetable and animal life in a state of nature will make it clear that a soil once supplied with soluble nitrates is likely to be replenished almost perpetually through the decay of vegetation. but it is equally clear that when the same soil is tilled by man, the balance of nature is likely to be at once disturbed. every pound of grain or of meat shipped to a distant market removes a portion of nitrogen; and unless the deficit is artificially supplied, the soil becomes presently impoverished. but an artificial supply of nitrogen is not easily secured--though something like twenty-five million tons of pure nitrogen are weighing down impartially upon every square mile of the earth's surface. in the midst of this tantalizing sea of plenty, the farmer has been obliged to take his choice between seeing his land become yearly more and more sterile and sending to far-off nitrate beds for material to take the place of that removed by his successive crops. the most important of the nitrate beds are situated in chili, and have been in operation since the year 1830. the draft upon these beds has increased enormously in recent years, with the increasing needs of the world's population. in the year 1870, for example, only 150,000 tons of nitrate were shipped from the chili beds; but in 1890 the annual output had grown to 800,000 tons; and it now exceeds a million and a half. conservative estimates predict that at the present rate of increased output the entire supply will be exhausted in less than twenty years. and for some years back scientists and economists have been asking themselves, what then? but now electro-chemistry has found an answer--even while the alarmists were predicting dire disaster. means have been found to extract the nitrogen from the atmosphere, in a form available as plant food, and at a cost that enables the new synthetic product to compete in the market with the chili nitrate. so all danger of a nitrogen famine is now at an end,--and applied science has placed to its credit another triumph, second to none, perhaps, among all its conquests. the author of this truly remarkable feat is a swedish scientist, christian birkeland by name, professor of physics in the university of christiania. his experiments were begun only about the year 1903, and the practical machinery for commercializing the results--in which enterprise professor birkeland has had the co-operation of a practical engineer, mr. s. eyde--is still in a sense in the experimental stage,--albeit a large factory was put in successful operation in 1905 at notodden, norway. professor birkeland has thus accomplished what many investigators in various parts of the world have been striving after for years. the significance of his accomplishment consists in the fact that he has demonstrated the possibility of making nitrogen combine with oxygen in large quantities and at a relatively low expense. the mere fact of the combination, as a laboratory possibility, had been demonstrated in an elder generation by cavendish, and more recently by such workers as sir william crookes, and lord rayleigh in england and professors w. mutjmaan and h. hofer in germany. moreover, the experiments of messrs. bradley and lovejoy, conducted on a commercial scale at niagara falls, had seemed to give promise of a complete solution of the problem; had, indeed, produced a nitrogen compound from the air in commercial quantity, but not, unfortunately, at a cost that made competition with the chili nitrate possible. equally unsuccessful in solving this important part of the problem had been the experiments, conducted on a large scale, of professors kowalski and moscicki, at freiburg. all these experimenters had adopted the same agent as the means of, so to say, forcing the transformation--namely, electricity. the american investigators employed a current of ten thousand volts; the german workers carried the current to fifty thousand volts. the flame of the electric arc thus produced ignited the nitrogen with which it came in contact readily enough; but the difficulty was that it came in contact with so little. despite ingenious arrangements of multiple poles, the burning-surface of the multiple arc remained so small in proportion to the expenditure of energy that the cost of the operation far exceeded the commercial value of the product. such, at least, must be the inference from the fact that the establishments in question did not attain commercial success. the peculiarity of professor birkeland's method is based upon the curious fact that when the electric arc is made to pass through a magnetic field, its line of flame spreads out into a large disk--"like a flaming sun." the sheet of flame thus produced represents no greater expenditure of energy than the lightning flash of light that the same current would produce outside the magnetic field; but it obviously adds enormously to the arc-light surface that comes in contact with the air, and hence in like proportion to the amount of nitrogen that will be ignited. in point of fact, this burning of nitrogen takes place so rapidly in laboratory experiments as to vitiate the air of the room very quickly. in the commercial operation, with powerful electro-magnets and a current of five thousand volts, operating, of course, in closed chambers, the ratio between energy expended and result achieved is highly satisfactory from a business standpoint, and will doubtless become still more so as the apparatus is further perfected. to the casual reader, unaccustomed to chemical methods, there may seem a puzzle in the explanation just outlined. he may be disposed to say, "you speak of the nitrogen as being ignited and burned; but if it is burned and thus consumed, how can it be of service?" such a thought is natural enough to one who thinks of burning as applied to ordinary fuel, which seems to disappear when it is burned. but, of course, even the tyro in chemistry knows that the fuel has not really disappeared except in a very crude visual sense; it has merely changed its form. in the main its solid substance has become gaseous, but every atom of it is still just as real, if not quite so tangible, as before; and the chemist could, under proper conditions, collect and weigh and measure the transformed gases, and even retransform them into solids. in the case of the atmospheric nitrogen, as in the case of ordinary fuel, a burning "consists essentially in the union of nitrogen atoms with atoms of oxygen." the province of the electric current is to produce the high temperature at which alone such union will take place. the portion of nitrogen that has been thus "burned" is still gaseous, but is no longer in the state of pure nitrogen; its atoms are united with oxygen atoms to form nitrous oxide gas. this gas, mixed with the atmosphere in which it has been generated, may now be passed through a reservoir of water, and the new gas combines with a portion of water to form nitric acid, each molecule of which is a compound of one atom of hydrogen, one atom of nitrogen, and three atoms of oxygen; and nitric acid, as everyone knows, is a very active substance, as marked in its eagerness to unite with other substances as pure nitrogen is in its aloofness. in the commercial nitrogen-plant at notodden, the transformed nitrogen compound is brought into contact with a solution of milk of lime, with the resulting formation of nitrate of lime (calcium nitrate), a substance identical in composition--except that it is of greater purity--with the product of the nitrate beds of chili. stored in closed cans as a milky fluid, the transformed atmosphere is now ready for the market. a certain amount of it will be used in other manufactories for the production of various nitrogenous chemicals; but the bulk of it will be shipped to agricultural districts to be spread over the soil as fertilizer, and in due course to be absorbed into the tissues of plants to form the food of animals and man. another method of nitrogen fixation just at the time when the scandinavian experimenters were solving the problem of securing nitrogen from the air, other experimenters in italy, operating along totally different lines, reached the same important result. the process employed by these investigators is known as the frank and caro process, and it bids fair to rival the norwegian method as a commercial enterprise. the process is described as follows by an engineering correspondent of the london _times_ in the engineering supplement of that periodical for january 22, 1908: "this process is based upon the absorption of nitrogen by calcium carbide, when this gas, in the pure form, is passed over the carbide heated to a temperature of 1,100 degrees centigrade in retorts of special form and design. the calcium carbide required as raw material for the cyanamide manufacture is produced in the usual manner by heating lime and coke to a temperature of 2,500 degrees centigrade in electric furnaces of the resistance type. "the european patent rights of the frank and caro process have been purchased by the societa generale per la cianamide of rome, and the various subsidiary companies promoting the manufacture in italy, france, switzerland, norway, and elsewhere, are working under arrangement with the parent company as regards sharing of profits. "the first large installation of a plant for carrying out this process was erected at piano d'orta, in central italy, and was put into operation in december, 1905. the power for this factory is developed by an independent company, and is obtained by taking water from the river pescara and leading it to a point above the generating station at tramonti. a head of 90 feet, equivalent to 8,400 horse-power, is here made available for the industries of the district. the power of the cyanamide factory is transmitted a distance of 6-1/4 miles at 6,000 volts. an aluminum and chemical works are also dependent upon the same power station. "the piano d'orta works contains six furnaces for the manufacture of cyanamide, each furnace containing five retorts for absorption of the nitrogen by the carbide. a retort is capable of working off three charges of 100 kilograms (220 pounds) of carbide per day of 24 hours, the weight of the charge increasing to 125 kilograms by the nitrogen absorbed. the present carbide consumption of the piano d'orta factory is, therefore, at the rate of about 3,000 tons per annum, and the output of calcium cyanamide is about 3,750 tons per annum. the company controlling the manufacture at piano d'orta is named the _societa italiana per la fabbricazione di prodotti azotati_. extensions of the factory at this place to a capacity of 10,000 tons per annum are already in progress. another company is also planning the erection of similar works at fiume and at sebenico, on the eastern borders of the adriatic sea. the additional electric power required will be obtained by carrying out the second portion of the power development scheme on the river pescara. a fall of 235 feet, equivalent to 22,000 horse-power, is available at the new power station, which is being erected at piano d'orta." after stating that companies to operate the frank and caro process have been organized in france, in switzerland, in germany, in england, and in america,--the last-named plant being at muscle shoals, tennessee river, in northern alabama--the writer continues: "these facts prove that the manufacture of the new nitrogenous manure will soon be carried on in all the more important countries on both sides of the atlantic. if the financial results come up to the promoter's expectations the industry in five years' time will have become one of considerable magnitude. "a modification of the original process of some importance has been suggested by polzeniusz. this chemist has found that the addition of fluorspar (caf2) to the carbide reduces the temperature required for the absorption process by 400 degrees centigrade, while it also produces a less deliquescent finished material. "as regards cost of manufacture, no very reliable figures are yet available, but the companies promoting the new manufacture are regulating their sale prices by those of the two rival artificial manures--ammonium sulphate and nitrate of soda. calcium cyanamide is now being sold in germany at 1s. to 1s. 6d. (25 to 37 cents) per unit of combined nitrogen cheaper than ammonium sulphate, and 3s. to 3s. 6d. (75 to 87 cents) per unit cheaper than nitrate of soda. whether the manufacture will prove remunerative at this price of about £10 10s. ($102.50) per ton remains to be seen. it is evident that, as the raw material of the cyanamide manufacture (calcium carbide) costs at least £8 ($40) per ton to produce under the most favorable conditions, the margin of profit will not be large, and that very efficient management will be required to earn fair dividends on the capital sunk in the new industry. "it must be noted, however, that the processes are new and are doubtless capable of improvement as experience is gained in working them; while, on the other hand, the competition of the two rival artificial manures is likely to diminish as the years pass on. "the new industry is, therefore, likely to be a permanent addition to the list of electro-metallurgical processes. but for the present its success can only be expected in centres of very cheap water-power, as, for instance, in those localities where the electric horse-power year can be generated and transmitted to the cyanamide works at an inclusive cost of £2 ($10) or under." electrical energy and high temperatures it will be observed that the active instrumentality by which the industrial feats thus far outlined have been accomplished, is that weird conveyer of energy known as electricity. in the case of the aluminum manufacture, electricity operated according to the strange process of electrolysis, in virtue of which certain atoms of matter move to one pole of a battery while other atoms move to the opposite pole, thus effecting a separation--the result being, in the case in question, the deposit of pure aluminum at the negative pole. in the case of the nitrogen factories, however, the manner of operation of the electric current is quite different. electricity, as such, is not really concerned in the matter; the efficiency of the current depends solely upon the production of heat. for example, any other agency that brought the atmosphere to a corresponding temperature would be equally efficacious in igniting the nitrogen. but in actual practice, for this particular purpose, no other known means of producing high temperatures could at all compete with the electric arc. there are numerous other operations involving the employment of high temperatures in which electricity is equally preeminent. it is feasible with the electric arc to attain a temperature of about 3,600 degrees centigrade--and even this might be exceeded were it not that carbon, of which the electrodes are composed, volatilizes at that temperature. meantime, the highest attainable temperature with ordinary fuels in the blast furnace is only about 1,800 degrees; and the oxy-hydrogen flame is only about two hundred degrees higher. a mixture of oxygen and acetylene, however, burns at a temperature almost equaling that of the electric arc; and this flame, manipulated with the aid of a blowpipe, offers a useful means of applying a high temperature locally, for such processes as the welding of metals. the very highest temperatures yet reached in laboratory or workshop, however, are due to the use of explosive mixtures. thus a mixture of the metal aluminum granulated, and oxide of iron, when ignited by a fulminating powder, readjusts its atoms to form oxide of aluminum and pure iron, and does this with such fervor that a temperature of about three thousand degrees is reached, the resulting iron being not merely melted but brought almost to the boiling point. practical advantage is taken of this reaction for the repair of broken implements of iron or steel, the making of continuous rails for trolleys, and the like. this reaction of aluminum and iron does not, to be sure, give a higher temperature than the electric arc; but this culminating feat has been achieved, in laboratory experiments, through the explosion of cordite in closed steel chambers; the experimenters being the englishmen sir andrew noble and sir f. abel. it is difficult to estimate accurately the degree of heat and pressure attained in these experiments; but it is believed that the temperature approximated 5,000 degrees centigrade, while the pressure represented the almost inconceivable push of ninety tons to the square inch. it may be of interest to explain that cordite is a form of smokeless powder composed of gun cotton, nitroglycerine, and mineral jelly. no doubt the extreme heat produced by its explosion is associated with the suddenness of the reaction; corresponding to the efficiency as a propellant that has led to the adoption of this powder for use in the small arms of the british army. no commercial use has yet been made of cordite as a mere producer of heat; but there is an interesting suggestion of possible future uses in the fact that crystals of diamond have been found in the residue of the explosion chamber--microscopic in size, to be sure, but veritable diamonds in miniature. sir william crookes has suggested that, could the reaction be prolonged sufficiently, "there is little doubt that the artificial formation of diamonds would soon pass from the microscopic stage to a scale more likely to satisfy the requirements of science, if not those of personal adornment." other industrial problems of to-day and to-morrow in attempting to suggest the importance of science in its relation to modern industries, i have thought it better to cite three or four illustrative cases in some detail rather than to attempt a comprehensive summary of the almost numberless lines of commercial activity that have a similar origin and dependence. to attempt a full list of these would be virtually to give a catalogue of mechanical industries. it may be well, however, to point out a few familiar instances, in order to emphasize the economic importance of the subject; and to suggest a few of the lines along which present-day investigators are seeking further conquests. very briefly, then, consider how the application of scientific knowledge has changed the aspect of the productive industries. thanks to science, farming is no longer a haphazard trade. the up-to-date farmer knows the chemical constitution of the soil; understands what constituents are needed by particular crops and what fertilizing methods to employ to keep his land from deteriorating. he knows how to select good seed according to the teaching of heredity; how to combat fungoid and insect pests by chemical means; how to meet the encroachments of the army of weeds. in the orchard, he can tell by the appearance of leaf and bark whether the soil needs more of nitrogen, of potash, or of humus; he uses sprays as a surgeon uses antiseptics; he introduces friendly insects to prey on insect pests; he irrigates or surface-tills or grows cover crops in accordance with a good understanding of the laws of capillarity as applied to water in the earth's crust. in barnyard and dairy he applies a knowledge of the chemistry of foods in his treatment of flock and herd; he ventilates his stables that the stock may have an adequate supply of oxygen; he milks his cows with a mechanical apparatus, extracts the cream with a centrifugal "separator," and churns by steam or by electric power. in the affairs of manufacturer and transporter of commodities, methods are no less revolutionary. steam power and electric dynamo everywhere hold sway; trolley and electric light and telephone have found their way to the most distant hamlet; electricians and experimental chemists are searching for new methods in the factories; artificial stone is competing with the product of the quarries; artificial dyes have sounded the doom of the madder and indigo industries. and yet it requires no great gift of prophecy to see that what has been accomplished is only an earnest of what is to come in the not distant future. in every direction eager experimenters are on the track of new discoveries. any day a chance observation may open new and important fields of exploration, just as hall's observation about the power of cryolite to absorb aluminum pointed the way to the new aluminum industry; and as birkeland's chance observation of the electric arc in a magnetic field unlocked the secret of the unresponsive nitrogen. it will probably not be long, for example, before a way will be found to produce electric light without heat--in imitation of the wonderful lamp of the glow-worm. then in due course we must learn to use fuel without the appalling waste that at present seems unavoidable. a modern steam-engine makes available only five to ten per cent. of the energy that the burning fuel gives out as heat--the rest is dissipated without serving man the slightest useful purpose. moreover, the new studies in radio-activity have taught us that every molecule of matter locks up among its whirling atoms and corpuscles a store of energy compared with which the energy of heat is but a bagatelle. it is estimated that a little pea-sized fragment of radium has energy enough in store--could we but learn to use it--to drive the largest steamship across the ocean--taking the place of hundreds of tons of coal as now employed. the mechanics of the future must learn how to unlock this treasury of the molecule; how to get at these atomic and corpuscular forces, the very existence of which was unknown to science until yesterday. the generation that has learned that secret will look back upon the fuel problems of our day somewhat as we regard the flint and steel and the open fire of the barbarian. if problems of energy offer such alluring possibilities as this, problems of matter are even more inspiring. the new synthetic chemistry sets no bounds to its ambitions. it has succeeded in manufacturing madder, indigo, and a multitude of minor compounds. it hopes some day to manufacture rubber, starch, sugar--even albumen itself, the very basis of life. rubber is a relatively simple compound of hydrogen and carbon; starch and sugar are composed of hydrogen, carbon, and oxygen; albumen has the same constituents, plus nitrogen. the raw materials for building up these substances lie everywhere about us in abundance. a lump of coal, a glass of water, and a whiff of atmosphere contain all the nutritive elements, could we properly mix them, of a loaf of bread or a beefsteak. and science will never rest content until it has learned how to make the combination. it is a long road to travel, even from the relatively advanced standpoint of to-day; but sooner or later science will surely travel it. and then--who can imagine, who dare predict, the social and economic revolution that must follow? our social and business life to-day differs more widely from that of our grandfathers than theirs differed from the life of the egyptian and babylonian of three thousand years ago; but this gap is as ditch to cañon compared with the gap that separates us from the life of that generation of our descendants which shall have learned the secret of making food-stuffs from inorganic matter in the laboratory and factory. it is a long road to travel, i repeat; but modern science travels swiftly and with many short-cuts, and it may reach this goal more quickly than any conservative dreamer of to-day would dare to predict. all speed to the ambitious voyager! appendix reference list and notes chapter i man and nature for a general discussion of primitive conditions of labor and prehistoric man's civilization, it will be of interest in connection with this chapter to consult volume i., chapter i., which deals with prehistoric science. the appendix notes on that chapter (vol. i., pp. 302, 303) refer to some books which may be consulted for fuller information along the same lines. chapter ii how work is done (p. 31). for study of archimedes, giving a detailed account of his discoveries, see vol. i., p. 196 _seq._ it will be of interest also to review, in connection with this chapter, the story of the growth of knowledge of mechanics in the time of galileo, descartes, and newton as told in the chapters entitled "galileo and the new physics," vol. ii. (p. 93 _seq._), and "the success of galileo in physical science," vol. ii., p. 204 _seq._ chapter iii the animal machine for further insight into the activities of the animal machine, the reader may refer to various chapters on the progress of physiology and anatomy in earlier volumes. the following references will guide to the accounts of the successive advances from the earliest time: vol. i., pp. 194, 195 describe briefly the earlier anatomical studies of the alexandrian physicians, herophilus and erasistratus; and pp. 282, 283, outline the studies of the famous physician, galen. vol. ii., "from paracelsus to harvey," in particular, p. 163 _seq._; and chapters iv. (p. 173 _seq._) and v. (p. 202 _seq._) dealing with the progress of anatomy and physiology in the eighteenth and nineteenth centuries respectively. the chapter on "experimental psychology" (p. 245 _seq._) may also be consulted. vol. v., chapter v., dealing with the marine biological laboratory at naples (p. 113 _seq._) and chapter vi., "ernst haeckel and the new zoology" (p. 144 _seq._) present other aspects of physiological problems. chapter iv the work of air and water on page 63 reference is made to the work of the old greeks, archimedes and ctesibius. an account of archimedes' discovery of the laws of buoyancy of solids and liquids will be found in vol. i., p. 208. (p. 64). the machines of ctesibius and hero. see vol. i., p. 242 _seq._, for a full account of these mechanisms. (p. 65). toricelli, the pupil of galileo, and his discovery of atmospheric pressure. for a fuller account of his discovery and what came of it see vol. ii., p. 120 _seq._ (p. 66). boyle's experiments on atmospheric pressure. see vol. ii., p. 204 _seq._ (p. 66). mariotte and von guericke. see vol. ii., p. 210 _seq._ (p. 71). roman mills. a scholarly discussion of the subject of roman mills, based on a comprehensive study of the references in classical literature, is given in beckmann's _history of inventions_, london, 1846. (p. 73). recent advances in water wheels. as stated in the text, the quotation is from an article on _motive power appliances_, by mr. edward h. sanborn, in the _twelfth census report_ of the united states. chapter v captive molecules; the story of the steam-engine (p. 82). the experiments of hero of alexandria. for a full account of the experiments see vol. i., pp. 249, 250. (p. 84). the marquis of worcester's steam engine. the original account appeared, as stated, in the marquis of worcester's _century of inventions_, published in 1663. (p. 92). newcomen's engine. as stated in the text, the account of newcomen's engine is quoted from the report of the department of science and arts of the south kensington museum, now officially known as the victoria and albert museum. (pp. 107-109). james watt. the characterization of watt here given is taken from an article in an early edition of the edinburgh encyclopædia published about the year 1815. chapter vi the master worker (p. 112). high-pressure steam. the work referred to is leupold's _theatrum machinarum_, 1725. (p. 122). rotary engines. the quotation is from the report of the victoria and albert museum above cited. (pp. 127, 128). turbine engines. the quotation is from an anonymous article in the london _times_, august 14, 1907. (pp. 129, 130). turbine engines. the quotation is from an article on _motive power appliances_ in the _twelfth census report_ of the united states, vol. x., part iv., by mr. edward h. sanborn. chapter vii gas and oil engines (pp. 135, 136, 137). gas engines. quoted from the report of the victoria and albert museum above cited. (pp. 141-144). gas engines and steam engines in the united states. quoted from the report of the special agents of the _twelfth census_ of the united states, 1902. (pp. 146, 147). the svea heater. from an article by mr. g. emil hesse in _the american inventor_ for april 15, 1905. chapter viii the smallest workers in connection with this chapter the reader will do well to review various earlier portions of the work outlining the general history of the growth of knowledge of electricity and magnetism. for example: vol. ii., p. 111 _seq._, for an account of william gilbert's study of magnetism; pp. 213, 215 describing first electrical machine; and chapter xiv., "the progress of electricity from gilbert and von guericke to franklin," p. 259 _seq._ vol. iii., chapter vii., "the modern development of electricity and magnetism," p. 229 _seq._ vol. v., p. 92 _seq._, the section on prof. j. j. thompson and the nature of electricity. other chapters that may be advantageously reviewed in connection with the present one are the following: vol. iii., chapter vi., "modern theories of heat and light," p. 206 _seq._; chapter viii., "the conservation of energy," p. 253 _seq._; and chapter ix., "the ether and ponderable matter," p. 283 _seq._ chapter ix man's newest co-laborer: the dynamo the references just given for chapter viii. apply equally here. the experiments of oersted and faraday are detailed in vol. iii., p. 236 _seq._ chapter x niagara in harness same references as for chapters viii. and ix. chapter xi the banishment of night (p. 221). davy and the electric light. the quotation here given is reproduced from vol. iii., pp. 234, 235. the very great importance and general interest of the subject seem to justify the repetition, descriptive of this first electric light. davy's original paper was given at the royal institution in 1810. (p. 237). "peter cooper hewitt--inventor," by ray stannard baker, in _mcclure's magazine_, june, 1903, p. 172. in connection with the problem of color of the light emitted by mr. hewitt's mercury-vapor tube, the chapter on "newton and the composition of light" (vol. ii., p. 225 _seq._) may be consulted. also "modern theories of heat and light," vol. iii., p. 206 _seq._ chapter xii the mineral depths the chapter on "the origin and development of modern geology," vol. iii., p. 116 _seq._, may be read in connection with the allied subjects here treated. in preparing the section on the use of electricity in mining, the article by thomas commerford martin, entitled _electricity in mining_, in the united states _census report_ of 1905, has been freely drawn upon. the quotations on pp. 262, 266, 268, and 270 are from that source. chapter xiii the age of steel see note under chapter xii. chapter xiv some recent triumphs of applied science in connection with various portions of this chapter the reader will find much that is of interest in the story of chemical development in general as detailed in volume iii., pp. 3-72 inclusive. also various chapters on electricity as outlined under chapter vii. above. (p. 310). nitrogen from the air. the quotation is from the _engineering supplement_ of the london _times_, january 22, 1908. transcriber's notes italic text is denoted by _underscores_. the oe ligature has been expanded to 'oe'. subscripts in chemical formulas are denoted by normal numbers; for example cac2. obvious typographical and punctuation errors have been corrected after careful comparison with other occurrences within the text and consultation of external sources. except for those changes noted below, inconsistent or archaic spelling of a word or word-pair within the text has been retained. for example: horseshoe horse-shoe; superheated super-heated; intrusted; incased. p iii. 'friction, p. 35' changed to 'friction, p. 39'. p iii. 'muscular action, p. 45' changed to '... action, p. 49'. p iv. 'wind-mill' changed to 'windmill'. p iv. 'ctesibus' changed to 'ctesibius'. p 93. 'was done is' changed to 'was done in'. p 114 (illustration caption). 'trevethick' changed to 'trevithick'. p 122. 'drlving' changed to 'driving'. p 180 (illustration caption). 'pull pieces' left unchanged (probably meant to be 'pole pieces'). p 191. 'horsehoe' changed to 'horseshoe'. p 264. 'liége' changed to 'liège'. p 299. 'repellant' changed to 'repellent'. transcriber's note: in text, italic is denoted by _underscores_ around the word/phrase. the italic markup for single italicised letters (such as pounds and pence symbols and in numbered lists) are deleted for easier reading. small capitals in the printed works have been transcribed as all capitals. in chemical equations, underscores before bracketed numbers denote a subscript, e.g. co_{2} (carbon dioxide). more transcriber's notes may be found at the end of this text. the romance of modern mechanism [illustration: a mechanical sculptor the lower illustration shows the wenzel sculpturing machine at work on two blocks of stone ranged one on each side of a model. this machine can make four copies simultaneously from one original. the upper illustration shows the quality of work done by the automatic sculptor.] the romance of modern mechanism with interesting descriptions in non-technical language of wonderful machinery and mechanical devices and marvellously delicate scientific instruments, &c., &c. by archibald williams, b.a., oxon., f.r.g.s. author of "the romance of modern invention," "the romance of modern mining," "the romance of modern engineering," "the romance of modern exploration," &c. &c. with thirty illustrations london seeley and co. limited 38 great russell street 1910 _uniform with this volume_ the library of romance _extra crown 8vo. with many illustrations. 5s. each_ "splendid volumes."--_the outlook._ "this series has now won a considerable and well deserved reputation."--_the guardian._ "each volume treats its allotted theme with accuracy, but at the same time with a charm that will commend itself to readers of all ages. the root idea is excellent, and it is excellently carried out, with full illustrations and very prettily designed covers."--_the daily telegraph._ by prof. g. f. scott elliot, m.a., b.sc. the romance of savage life the romance of plant life the romance of early british life by edward gilliat, m.a. the romance of modern sieges by john lea, m.a. the romance of bird life by john lea, m.a., & h. coupin, d.sc. the romance of animal arts and crafts by sidney wright the romance of the world's fisheries by the rev. j. c. lambert, m.a., d.d. the romance of missionary heroism by g. firth scott the romance of polar exploration by archibald williams, b.a. (oxon.), f.r.g.s. the romance of early exploration the romance of modern exploration the romance of modern mechanism the romance of modern invention the romance of modern engineering the romance of modern locomotion the romance of modern mining by charles r. gibson, a.i.e.e. the romance of modern photography the romance of modern electricity the romance of modern manufacture by edmund selous the romance of the animal world the romance of insect life by agnes giberne the romance of the mighty deep by e. s. grew, m.a. the romance of modern geology by j. c. philip, d.sc., ph.d. the romance of modern chemistry seeley & co., limited introduction in the beginning a man depended for his subsistence entirely upon his own efforts, or upon those of his immediate relations and friends. life was very simple in those days: luxury being unknown, and necessity the factor which guided man's actions at every turn. with infinite labour he ground a flint till it assumed the shape of a rough arrow-head, to be attached to a reed and shot into the heart of some wild beast as soon as he had approached close enough to be certain of his quarry. the meat thus obtained he seasoned with such roots and herbs as nature provided--a poor and scanty choice. presently he discovered that certain grains supported life much better than roots, and he became an agriculturist. but the grain must be ground; so he invented a simple mill--a small stone worked by hand over a large one; and when this method proved too tedious he so shaped the stones' surfaces that they touched at all points, and added handles by which the upper stone could be revolved. with the discovery of bronze, and, many centuries later, of iron, his workshop equipment rapidly improved. he became an expert boatand house-builder, and multiplied weapons of offence and defence. gradually separate crafts arose. one man no longer depended on his individual efforts, but was content to barter his own work for the products of another man's labour, because it became evident that specialisation promoted excellence of manufacture. a second great step in advance was the employment of machinery, which, when once fashioned by hand, saved an enormous amount of time and trouble--the pump, the blowing bellows, the spinning-wheel, the loom. but all had to be operated by human effort, sometimes replaced by animal power. with the advent of the steam-engine all industry bounded forward again. first harnessed by watt, giant steam has become a commercial and political power. everywhere, in mill and factory, locomotive, ship, it has increased the products which lend ease and comfort to modern life; it is the great ally of invention, and the ultimate agent for transporting men and material from one point on the earth's surface to another. try as we may, we cannot escape from our environment of mechanism, unless we are content to revert to the loincloth and spear of the savage. society has become so complicated that the utmost efforts of an individual are, after all, confined to a very narrow groove. the days of the jack-of-all-trades are over. success in life, even bare subsistence, depends on the concentration of one's faculties upon a very limited daily routine. "let the cobbler stick to his last" is a maxim which carries an ever-increasing force. the better to realise how dependent we are on the mechanisms controlled by the thousand and one classes of workmen, let us consider the surroundings, possessions, and movements of the average, well-to-do business man. at seven o'clock he wakes, and instinctively feels beneath his pillow for his watch, a most marvellous assemblage of delicate parts shaped by wonderful machinery. before stepping into his bath he must turn a tap, itself a triumph of mechanical skill. the razor he shaves with, the mirror which helps him in the operation, the very brush and soap, all are machine-made. with his clothes he adds to the burden of his indebtedness to mechanism. the power-loom span the linen for his shirts, the cloth for his outer garments. shirts and collars are glossy from the treatment of the steam laundry, where machinery is rampant. his boots, kept shapely by machine-made lasts, should remind him that mechanical devices have played a large part in their manufacture, very possibly the human hand has scarcely had a single duty to perform. he goes downstairs, and presses an electric button. mechanism again. while waiting for his breakfast his eye roves carelessly over the knives, spoons, forks, table, tablecloth, wall-paper, engravings, carpet, cruet-stand--all machine-made in a larger or less degree. the very coals blazing in the grate were won by machinery; the marble of the mantelpiece was shaped and polished by machinery; also the fire-irons, the chairs, the hissing kettle. machinery stares at him from the loaf on its machine-made board. machines prepared the land, sowed, harvested, threshed, ground, and probably otherwise prepared the grain for baking. machines ground his salt, his coffee. machinery aided the capture of the tempting sole; helped to cure the rasher of bacon; shaped the dishes, the plates, the coffee-pot. whirr-r-r! the motor-car is at the door, throbbing with the impulses of its concealed machinery. our friend therefore puts on his machine-made gloves and hat and sallies forth. that wonderful motor, the product of the most up-to-date, scientific, and mechanical appliances, bears him swiftly over roads paved with machine-crushed stone and flattened out by a steam-roller. a book might be reserved to the motor alone; but we must refrain, for a few minutes' travel has brought the horseless carriage to the railway station. mr. smith, being the holder of a season ticket, does not trouble the clerk who is stamping pasteboards with a most ingenious contrivance for automatically impressing dates and numbers on them. he strolls out on the platform and buys the morning paper, which, a few hours before, was being battered about by one of the most wonderful machines that ever was devised by the brain of man. mr. smith doesn't bother his head with thoughts of the printing-press. its products are all round him, in timetables and advertisements. nor does he ponder upon the giant machinery which crushed steel ingots into the gleaming rails that stretch into the far distance; nor upon the marvellous interlocking mechanism of the signal-box at the platform-end; nor upon the electric wires thrumming overhead. no! he had seen all these things a thousand times before, and probably feels little of the romance which lies so thickly upon them. a whistle blows. the "local" is approaching, with its majestic locomotive--a very orgy of mechanism--its automatic brakes, its thousand parts all shaped by mechanical devices,--steam saws, planes, lathes, drills, hammers, presses. in obedience to a little lever the huge mass comes quickly to rest; the steam pump on the engine commences to gasp; a minute later another lever moves, and mr. smith is fairly on his way to business. arrived at the metropolis, he presses electricity into his service, either on an electric tram or on a subterranean train. in the latter case he uses an electric lift, which lowers him into the bowels of the earth, to pass him on to the current-propelled cars, driven by power generated in far-away stations. his office is stamped all over with the seal of mechanism. in the lobby are girls hammering on marvellous typewriters; on his desk rests a telephone, connected through wires and most elaborately equipped exchanges with all parts of the country. to get at his private and valuable papers mr. smith must have recourse to his bunch of keys, which, with their corresponding locks, represent ingenuity of a high degree. all day long he is in the grasp of mechanism; not even at lunch time can he escape it, for the food set before him at the restaurant has been cooked by the aid of special kitchen machinery. and when the evening draws on mr. smith touches a switch to turn his darkness into light, wrung through many wonderful processes from the stored illumination of coal. were we to trace the daily round of the clerk, artisan, scientist, engineer, or manufacturer, we should be brought into contact with a thousand other mechanical appliances. space forbids such a tour of inspection; but in the following pages we may rove here and there through the workshops of the world, gleaning what seems to be of special interest to the general public, and weaving round it, with a machine-made pen, some of the romance which is apt to be lost sight of by the most marvellous of all creations--man. author's note the author desires to express his indebtedness to the following gentlemen for the kind help they have afforded him in connection with the gathering of materials for the letterpress and illustration of this book:-the proprietors of _cassier's magazine_, _the magazine of commence_, _the world's work_, _the motor boat_; the rexer automatic machine gun co.; the diesel oil engine co.; the cambridge scientific instrument co.; the marconi wireless telegraphy co.; the temperley transporter co.; messrs. de dion, bouton and co.; messrs. merryweather and sons; mr. a. crosby lockwood; mr. dan albone; mr. j. b. diplock; mr. w. h. oatway; the national cash register co.; the wenzel sculpturing machine co.; mr. e. w. gaz; sir w. g. armstrong, whitworth and co.; the international harvester co. and messrs. gwynne and co. table of contents page introduction v author's note xi chapter i delicate instruments--watches and chronometers--the microtome--the dividing engine--measuring machines 17 chapter ii calculating machines 42 chapter iii workshop machinery--the lathe--planing machines--the steam hammer--hydraulic tools--electrical tools in the shipyard 59 chapter iv portable tools 90 chapter v the pedrail: a walking steam-engine 97 chapter vi internal combustion engines--oil engines--engines worked with producer gas--blast furnace gas engines 112 chapter vii motor-cars--the motor omnibus--railway motor-cars 130 chapter viii the motor afloat--pleasure boats--motor lifeboats--motor fishing boats--a motor fire float--the mechanism of the motor boat--the two-stroke motor--motor boats for the navy 150 chapter ix the motor cycle 175 chapter x fire engines 185 chapter xi fire-alarms and automatic fire extinguishers 191 chapter xii the machinery of a ship--the reversing engine--marine engine speed governors--the steering engine--blowing and ventilating apparatus--pumps--feed heaters--feed-water filters--distillers--refrigerators--the search-light--wireless telegraphy instruments--safety devices--the transmission of power on a ship 203 chapter xiii "the nurse of the navy" 236 chapter xiv the mechanism of diving 240 chapter xv apparatus for raising sunken ships and treasure 248 chapter xvi the handling of grain--the elevator--the suction pneumatic grain-lifter--the pneumatic blast grain-lifter--the combined system 252 chapter xvii mechanical transporters and conveyers--ropeways--cableways--telpherage--coaling warships at sea 258 chapter xviii automatic weighers 274 chapter xix transporter bridges 277 chapter xx boatand ship-raising lifts 283 chapter xxi a self-moving staircase 295 chapter xxii pneumatic mail tubes 301 chapter xxiii an electric postal system 315 chapter xxiv agricultural machinery--ploughs--drills and seeders--reaping machines--threshing machines--petrol-driven field machinery--electrical farming machinery 318 chapter xxv dairy machinery--milking machines--cream separators--a machine for drying milk 330 chapter xxvi sculpturing machines 335 chapter xxvii an automatic rifle--a ball-bearing rifle 345 list of illustrations page a carving machine _frontispiece_ measuring machines 34 a cash register 45 lathe turning a big gun 59 lathe for boring 16-inch gun 65 a steam hammer 72 a huge hydraulic press 82 a pedrail traction engine 108 great gas engine for blast furnaces 128 motor-car and motor-boat 151 a motogodille 156 a motor lawn mower 182 up-to-date fire brigade engines 186 hoisting a heavy gun on board man-of-war 204 fixing a ram to a battleship 228 a tripod crane 237 modern diving apparatus 245 coaling at sea 271 a transporter bridge at bizerta 278 a canal lift 289 an american cutter and binder 322 a motor plough 327 girl carving by machinery 343 the rexer gun 352 the romance of modern mechanism chapter i delicate instruments watches and chronometers--the microtome--the dividing engine--measuring machines owing to the universal use of watches, resulting from their cheapness, the possessor of a pocket timepiece soon ceases to take a pride in the delicate mechanism which at first added an inch or two to his stature. at night it is wound up mechanically, and thrust under the pillow, to be safe from imaginary burglars and handy when the morning comes. the awakened sleeper feels small gratitude to his faithful little servant, which all night long has been beating out the seconds so that its master may know just where he is with regard to "the enemy" on the morrow. at last a hand is slipped under the feather-bag, and the watch is dragged from its snug hiding-place. "bother it," says the sleepy owner, "half-past eight; ought to have been up an hour ago!" and out he tumbles. dressing concluded, the watch passes to its day quarters in a darksome waistcoat pocket, to be hauled out many times for its opinion to be taken. the real usefulness of a watch is best learnt by being without one for a day or two. there are plenty of clocks about, but not always in sight; and one gradually experiences a mild irritation at having to step round the corner to find out what the hands are doing. a truly wonderful piece of machinery is a watch--even a cheap one. an expensive, high-class article is worthy of our admiration and respect. here is one that has been in constant use for fifty years. twice a second its little balance-wheel revolves on its jewelled bearings. allowing a few days for repairs, we find by calculation that the watch has made no less than three thousand million movements in the half-century! and still it goes ticking on, ready to do another fifty years' work. how beautifully tempered must be the springs and the steel faces which are constantly rubbing against jewel or metal! how perfectly cut the teeth which have engaged one another times innumerable without showing appreciable wear! the chief value of a good watch lies in its accuracy as a time-keeper. it is, of course, easy to correct it by standard clocks in the railway stations or public buildings; but one may forget to do this, and in a week or two a loss of a few minutes may lead to one missing a train, or being late for an important engagement. happy, therefore, is the man who, having set his watch to "london time," can rely on its not varying from accuracy a minute in a week--a feat achieved by many watches. the old-fashioned watch was a bulky affair, protected by an outer case of ample proportions. from year to year the size has gradually diminished, until we can now purchase a reliable article no thicker than a five-shilling piece, which will not offend the most fastidious dandy by disarranging the fit of his clothes. into the space of a small fraction of an inch is crowded all the usual mechanism, reduced to the utmost fineness. watches have even been constructed small enough to form part of a ring or earring, without losing their time-keeping properties. for practical purposes, however, it is advantageous to have a timepiece of as large a size as may be convenient, since the difficulties of adjustment and repair increase with decreasing proportions. the ship's chronometer, therefore, though of watch construction, is a big affair as compared with the pocket timepiece; for above all things it must be accurate. the need for this arises from the fact that nautical reckonings made by the observation of the heavenly bodies include an element of _time_. we will suppose a vessel to be at sea out of sight of land. the captain, by referring to the dial of the "mechanical log," towed astern, can reckon pretty accurately how _far_ the vessel has travelled since it left port; but owing to winds and currents he is not certain of the position on the globe's surface at which his ship has arrived. to locate this exactly he must learn (a) his longitude, _i.e._ distance e. or w. of greenwich, (b) his latitude, _i.e._ distance n. or s. of the equator. therefore, when noon approaches, his chronometers and sextant are got out, and at the moment when the sun crosses the meridian the time is taken. if this moment happens to coincide with four o'clock on the chronometers he is as far west of greenwich as is represented by four twenty-fourths of the 360â° into which the earth's circumference is divided; that is, he is in longitude 60â° w. the sextant gives him the angle made by a line drawn to the sun with another drawn to the horizon, and from that he calculates his latitude. then he adjourns to the chart-room, where, by finding the point at which the lines of longitude and latitude intersect, he establishes his exact position also. when the ship leaves england the chronometer is set by greenwich time, and is never touched afterwards except to be wound once a day. in order that any error may be reduced to a minimum a merchant ship carries at least two chronometers, a man-of-war at least three, and a surveying vessel as many as a dozen. the average reading of the chronometers is taken to work by. taking the case of a single chronometer, it has often to be relied on for months at a time, and during that period has probably to encounter many changes of temperature. if it gains or loses from day to day, and that _consistently_, it may still be accounted reliable, as the amount of error will be allowed for in all calculations. but should it gain one day and lose another, the accumulated errors would, on a voyage of several months, become so considerable as to imperil seriously the safety of the vessel if navigating dangerous waters. as long ago as 1714 the english government recognised the importance of a really reliable chronometer, and in that year passed an act offering rewards of â£10,000, â£15,000, and â£20,000 to anybody who should produce a chronometer that would fix longitude within sixty, forty, and thirty miles respectively of accuracy. john harrison, the son of a yorkshire carpenter, who had already invented the ingenious "gridiron pendulum" for compensating clocks, took up the challenge. by 1761 he had made a chronometer of so perfect a nature that during a voyage to jamaica that year, and back the next, it lost only 1 min. 54-1/2 sec. as this would enable a captain to find his longitude within eighteen miles in the latitude of greenwich, harrison claimed, and ultimately received, the maximum reward. it was not till nearly a century later that thomas earnshaw produced the "compensation balance," now generally used on chronometers and high-class watches. in cheap watches the balance is usually a little three-spoked wheel, which at every tick revolves part of a turn and then flies back again. this will not suffice for very accurate work, because the "moment of inertia" varies at different temperatures. to explain this term let us suppose that a man has a pound of metal to make into a wheel. if the wheel be of small diameter, you will be able to turn it first one way and then the other on its axle quite easily. but should it be melted down and remade into a wheel of four times the diameter, with the same amount of metal as before in the rim, the difficulty of suddenly reversing its motion will be much increased. the weight is the same, but the speed of the rim, and consequently its momentum, is greater. it is evident from this that, if a wheel of certain size be driven by a spring of constant strength, its oscillations will be equal in time; but if a rise of temperature should lengthen the spokes the speed would fall, because the spring would have more work to do; and, conversely, with a fall of temperature the speed would rise. earnshaw's problem was to construct a balance wheel that should be able to keep its "moment of inertia" constant under all circumstances. he therefore used only two spokes to his wheel, and to the outer extremity of each attached an almost complete semicircle of rim, one end being attached to the spoke, the other all but meeting the other spoke. the rim-pieces were built up of an outer strip of brass, and an inner strip of steel welded together. brass expands more rapidly than steel, with the result that a bar compounded of these two metals would, when heated, bend towards the hollow side. to the rim-pieces were attached sliding weights, adjustable to the position found by experiment to give the best results. we can now follow the action of the balance wheel. it runs perfectly correctly at, say, a temperature of 60â°. hold it over a candle. the spokes lengthen, and carry the rim-pieces _outwards_ at their fixed ends; but, as the pieces themselves bend inwards at their free ends, the balance is restored. if the balance were placed in a refrigerating machine, the spokes would shorten, but the rim-pieces would bend outwards. as a matter of fact, the "moment of inertia" cannot be kept quite constant by this method, because the variation of expansion is more rapid in cold than in heat; so that, though a balance might be quite reliable between 60â° and 100â°, it would fail between 30â° and 60â°. so the makers fit their balances with what is called a _secondary_ compensation, the effect of which is to act more quickly in high than in low temperatures. this could not well be explained without diagrams, so a mere mention must suffice. another detail of chronometer making which requires very careful treatment is the method of transmitting power from the main spring to the works. as the spring uncoils, its power must decrease, and this loss must be counterbalanced somehow. this is managed by using the "drum and fusee" action, which may be seen in some clocks and in many old watches. the drum is cylindrical, and contains the spring. the fusee is a tapering shaft, in which a spiral groove has been cut from end to end. a very fine chain connects the two parts. the key is applied to the fusee, and the chain is wound off the drum on to the larger end of the fusee first. by the time that the spring has been fully wound, the chain has reached the fusee's smaller extremity. if the fusee has been turned to the correct taper, the driving power of the spring will remain constant as it unwinds, for it gets least leverage over the fusee when it is strongest, and most when it is weakest, the intermediate stages being properly proportioned. to test this, a weighted lever is attached to the key spindle, with the weight so adjusted that the fully wound spring has just sufficient power to lift it over the topmost point of a revolution. it is then allowed a second turn, but if the weight now proves excessive something must be wrong, and the fusee needs its diameter reducing at that point. so the test goes on from turn to turn, and alterations are made until every revolution is managed with exactly the same ease. the complete chronometer is sent to greenwich observatory to be tested against the standard clock, which, at 10 a.m., flashes the hour to other clocks all over great britain. in a special room set apart for the purpose are hundreds of instruments, some hanging up, others lying flat. assistants make their rounds, noting the errors on each. the temperature test is then applied in special ovens, and finally the article goes back to the maker with a certificate setting forth its performances under different conditions. if the error has been consistent the instrument is sold, the buyer being informed exactly what to allow for each day's error. at the end of the voyage he brings his chronometer to be tested again, and, if necessary, put right. here are the actual variations of a chronometer during a nineteen-day test, before being used:- gain in _tenths_ day. of seconds. 1st 1/2 2nd 3 3rd 4 4th 4 5th 1/2 6th 3 7th 0 8th 0 9th 4-1/2 10th 3 11th 4 12th 3 13th 3 14th 4 15th 5 16th 2 17th 3 18th 5 19th 1 an average gain of just over one quarter of a second per diem! quite extraordinary feats of time-keeping have been recorded of chronometers on long voyages. thus a chronometer which had been to australia _viã¢_ the cape and back _viã¢_ the red sea was only fifteen seconds "out"; and the _encyclopã¦dia britannica_ quotes the performance of the three instruments of s.s. _orellana_, which between them accumulated an error of but 2â·3 seconds during a sixty-three-day trip. an instrument which will cut a blood corpuscle into several parts--that's the microtome, the "small-cutter," as the name implies. for the examination of animal tissues it is necessary that they should be sliced very fine before they are subjected to the microscope. perhaps a tiny muscle is being investigated and cross sections of it are needed. well, one cannot pick up the muscle and cut slices off it as you would off a german sausage. to begin with, it is difficult even to pick the object up; and even if pieces one-hundredth of an inch long were detached they would still be far too large for examination. so, as is usually the case when our unaided powers prove unequal to a task, we have recourse to a machine. there are several types of microtomes, each preferable for certain purposes. but as in ordinary laboratory work the cambridge rocking microtome is used, let us give our special attention to this particular instrument. it is mounted on a strong cast-iron bed, a foot or so in length and four to five inches wide. towards one end rise a couple of supports terminating in knife-edges, which carry a cross-bar, itself provided with knife-edges top and bottom, those on the top supporting a second transverse bar. both bars have a long leg at right angles, giving them the appearance of two large t's superimposed one on the other; but the top t is converted into a cross by a fourth member--a sliding tube which projects forward towards a frame in which is clamped a razor, edge upwards. the tail of the lower t terminates in a circular disc, pierced with a hole to accommodate the end of a vertical screw, which has a large circular head with milled edges. the upper t is rocked up and down by a cord and spring, the handle actuating the cord also shifting on the milled screw-head a very small distance every time it is rocked backwards and forwards. as the screw turns, it gradually raises the tail of the lower member, and by giving its cross-bar a tilt brings the tube of the upper member appreciably nearer the razor. the amount of twist given to the screw at each stroke can be easily regulated by a small catch. when the microscopist wishes to cut sections he first mounts his object in a lump of hard paraffin wax, coated with softer wax. the whole is stuck on to the face of the tube, so as to be just clear of the razor. the operator then seizes the handle and works it rapidly until the first slice is detached by the razor. successive slices are stuck together by their soft edges so as to form a continuous ribbon of wax, which can be picked up easily and laid on a glass slide. the slide is then warmed to melt the paraffin, which is dissolved away by alcohol, leaving the atoms of tissue untouched. these, after being stained with some suitable medium, are ready for the microscope. a skilful user can, under favourable conditions, cut slices _one twenty-five thousandth_ of an inch thick. to gather some idea of what this means we will imagine that a cucumber one foot long and one and a-half inches in diameter is passed through this wonderful guillotine. it would require no less than 700 dinner-plates nine inches across to spread the pieces on! if the slices were one-eighth of an inch thick, the cucumber, to keep a proportionate total size, would be 260 feet long. after considering these figures we shall lose some of the respect we hitherto felt for the men who cut the ham to put inside luncheon-bar sandwiches. in the preceding pages frequent reference has been made to index screws, exactly graduated to a convenient number of divisions. when such screws have to be manufactured in quantities it would be far too expensive a matter to measure each one separately. therefore machinery, itself very carefully graduated, is used to enable a workman to transfer measurements to a disc of metal. if the index-circle of an astronomical telescope--to take an instance--has to be divided, it is centred on a large horizontal disc, the circumference of which has been indented with a large number of teeth. a worm-screw engages these teeth tangentially (_i.e._ at right angles to a line drawn from the centre of the plate to the point of engagement). on the shaft of the screw is a ratchet pinion, in principle the same as the bicycle free-wheel, which, when turned one way, also twists the screw, but has no effect on it when turned the other way. stops are put on the screw, so that it shall rotate the large disc only the distance required between any two graduations. the divisions are scribed on the index-circle by a knife attached to a carriage over and parallel to the disc. the dividing engine used for the graduation of certain astronomical instruments probably constitutes the most perfect machine ever made. in an address to the institution of mechanical engineers,[1] the president, mr. william henry maw, used the following words: "the most recently constructed machine of the kind of which i am aware--namely, one made by messrs. warner and swasey, of cleveland, u.s.a.--is capable of automatically cutting the graduations of a circle with an error in position not exceeding one second of arc. (a second of an arc is approximately the angle subtended by a halfpenny at a distance of three miles.) this means that on a 20-inch circle the error in position of any one graduation shall not exceed 1/20,000 inch. now, the finest line which would be of any service for reading purposes on such a circle would probably have a width equal to quite ten seconds of arc; and it follows that the minute v-shaped cut forming this line must be so absolutely symmetrical with its centre line throughout its length, that the position of this centre may be determined within the limit of error just stated by observations of its edges, made by aid of the reading micrometer and microscope. i may say that after the machine just mentioned had been made, it took _over a year's hard work_ to reduce the maximum error in its graduations from one and a-half to one second of arc." the same address contains a reference to the great yerkes telescope, which though irrelevant to our present chapter, affords so interesting an example of modern mechanical perfection that it deserves parenthetic mention. the diameter of a star of the seventh magnitude as it appears in the focus of this huge telescope is 1/2,500 inch. the spiders' webs stretched across the object glass are about 1/6,000 inch in diameter. "the problem thus is," says mr. maw, "to move this twenty-two ton mass (the telescope) with such steadiness in opposition to the motion of the earth, that a star disc 1/2,500 inch in diameter can be kept threaded, as it were, upon a spider's web 1/6,000 inch in diameter, carried at a radius of thirty-two feet from the centre of motion. i think that you will agree that this is a problem in mechanical engineering demanding no slight skill to solve; but it has been solved, and with the most satisfactory results." the motions are controlled electrically; and respecting them professor barnard, one of the chief observers with this telescope, some time ago wrote as follows: "it is astonishing to see with what perfect instantaneousness the clock takes up the tube. the electric slow motions are controlled from the eye end. so exact are they that a star can be brought from the edge of the field and stopped instantaneously behind the micrometer wire." dividing engines are used for ruling parallel lines on glass and metal, to aid in the measurements of microscopical objects or the wave-lengths of light. a _diffraction grating_, used for measuring the latter, has the lines so close together that they would be visible only under a powerful microscope. glass being too brittle, a special alloy of so-called _speculum_ metal is fashioned into a highly polished plate, and this is placed in the machine. a delicate screw arrangement gradually feeds the plate forwards under the diamond point, which is automatically drawn across the plate between every two movements. professor h. a. rowlands has constructed a parallel dividing engine which has ruled as many as 120,000 lines to the inch. to get a conception of these figures we must once again resort to comparison. let us therefore take a furrow as a line, and imagine a ploughman going up and down a field 120,000 times. if each furrow be eight inches wide, the field would require a breadth of nearly _fourteen miles_ to accommodate all the furrows! again, supposing that a plate six inches square were being ruled, the lines placed end to end would extend for seventy miles! professor rowlands' machine does the finest work of this kind. another very perfect instrument has been built by lord blythswood, and as some particulars of it have been kindly supplied, they may fitly be appended. if a first-class draughtsman were asked how many parallel straight lines he would rule within the space of one inch, it is doubtful whether he would undertake more than 150 to 200 lines. lord blythswood's machine can rule fourteen parallel lines on a space equivalent to the _edge_ of the finest tissue paper. so delicate are the movements of the machine that it must be protected from variations of temperature, which would contract or expand its parts; so the room in which it stands is kept at an even heat by automatic apparatus, and to make things doubly sure the engine is further sheltered in a large case having double walls inter-packed with cotton wool. in constructing the machine it was found impossible, with the most scientific tools, to cut a toothed wheel sufficiently accurate to drive the mechanism, but the errors discovered by microscopes were made good by the invention of a small electro-plating brush, which added the thinnest imaginable layer of metal to any tooth found deficient. during the process of ruling a grating of only a few square inches area, the machine must be left severely alone in its closed case. the slightest jar would cause unparallelism of a few lines, and the ruin of the whole grating. so for several days the diamond point has its own way, moving backwards and forwards unceasingly over the hard metal, in which it chases tiny grooves. at the end the plate has the appearance of mother-of-pearl, which is, in fact, one of nature's diffraction gratings, breaking up white light into the colours of the spectrum. you will be able to understand that these mechanical gratings are expensive articles. sometimes the diamond point breaks half-way through the ruling, and a week's work is spoilt. also the creation of a reliable machine is a very tedious business. ten pounds per square inch of grating is a low price to pay. the greatest difficulty met with in the manufacture of the dividing engine is that of obtaining a mathematically correct screw. turning on a lathe produces a very rough spiral, judged scientifically. some threads will be deeper than others, and differently spaced. the screw must, therefore, be ground with emery and oil introduced between it and a long nut which is made in four segments, and provided with collars for tightening it up against the screw. perhaps a fortnight may be expended over the grinding. then the screw must undergo rigid tests, a nut must be made for it, and it has to be mounted in proper bearings. the explanation of the method of eliminating errors being very technical, it is omitted; but an idea of the care required may be gleaned from professor rowlands' statement that an uncorrected error of 1/300,000 of an inch is quite sufficient to ruin a grating! in the houses of parliament there is kept at an even temperature a bronze rod, thirty-eight inches long and an inch square in section. near the ends are two wells, rather more than half an inch deep, and at the bottom of the wells are gold studs, each engraved with a delicate cross line on their polished surfaces. the distance between the lines is the imperial yard of thirty-six inches. the bar was made in 1844 to replace the standard destroyed in 1834, when both houses of parliament were burned. the original standard was the work of bird, who produced it in 1760. in june, 1824, an act had been passed legalising this standard. it says:-"the same straight line or distance between the centers of the said two points in the said gold studs in the said brass rod, the brass being at the temperature of sixty-two degrees by fahrenheit's thermometer, shall be and is hereby denominated the 'imperial standard yard.'" to provide for accidents to the bar, the act continues: "and whereas it is expedient that the said standard yard, if lost, destroyed, defaced, or otherwise injured, should be restored to the same length by reference to some invariable natural standard: and whereas it has been ascertained by the commissioners appointed by his majesty to inquire into the subject of weights and measures, that the yard hereby declared to be the imperial standard yard, when compared with a pendulum vibrating seconds of mean time in the latitude of london in a vacuum at the level of the sea, is in the proportion of thirty-six inches to thirty-nine inches and one thousand three hundred and ninety-three ten-thousandth parts of an inch." the new bar was made, however, not by this method, but by comparing several copies of the original and striking their average length. four accurate duplicates of the new standard were secured, one of which is kept in the mint, one in the charge of the royal society, one at westminster palace, and the fourth at the royal observatory, greenwich. in addition, forty copies were distributed among the various foreign governments, all of the same metal as the original. the french metre has also been standardised, being equal to one ten-millionth part of a quadrant of the earth's meridian (_i.e._ of the distance from the equator to either of the poles), that is, to 39â·370788 inches. professor a. a. michelson has shown that any standard of length may be restored by reference to the measurement of wave lengths of light, with an error not exceeding one ten-millionth part of the whole. it might be asked "why should standards of such great accuracy be required?" in rough work, such as carpentry, it does not, indeed, matter if measurements are the hundredth of an inch or so out. but when we have to deal with scientific instruments, telescopes, measuring machines, engines for dividing distances on a scale, or even with metal turning, the utmost accuracy becomes needful; and a number of instruments will be much more alike in all dimensions if compared individually with a common standard than if they were only compared with one another. supposing, for instance, a bar of exact diameter is copied; the copy itself copied; and so on a dozen times; the last will probably vary considerably from the correct measurements. hence it became necessary to standardise the foot and the inch by accurate subdivisions of the yard. this was accomplished by sir joseph whitworth, who in 1834 obtained two standard yards in the form of measure bars, and by the aid of microscopes transferred the distance between the engraved lines to a rectangular _end_-measure bar, _i.e._ one of which the end faces are exactly a yard apart. he next constructed his famous machine which is capable of detecting length differences of _one millionth_ of an inch. two bars are advanced towards each other by screw gearing: one by a screw having twenty threads to the inch, and carrying a graduated hand-wheel with 250 divisions on its rim; the other by a similar screw, itself driven by a worm-screw, working on the rim, which carries 200 teeth. the worm-screw has a hand-wheel with a micrometer graduation into 250 divisions of its circumference. so that, if this be turned one division, the second screw is turned only 1/250 ã� 1/200 of a division, and the bar it drives advances only 1/20 ã� 1/200 ã� 1/250 = 1/1,000,000 of an inch. the screw at the other end of the machine (which in appearance somewhat resembles a metal lathe) is used for rapid adjustment only. [illustration: delicate measuring machines the upper illustration shows a pratt-whitney measuring machine in operation to decide the thickness of a cigarette paper, which is one-thousandth of an inch thick. this machine will measure variations of length or thickness as minute as one hundredth-thousandth of an inch. the lower illustration shows a whitworth measuring machine which is sensitive to variations of one-millionth of an inch.] "he (sir j. whitworth) obtained the subdivision of the yard by making three foot pieces as nearly alike as was possible, and working these foot pieces down until each was equal to the others, and placing them end to end in his millionth measuring machine; the total length of the three foot pieces was then compared with a standard end-measure yard. these three foot pieces were ground until they were exactly equal to each other, and the three added together are equal to the standard yard. the subdivision of the foot into inch pieces was made in the same way."[2] a doubt may have arisen in the reader's mind as to the possibility of determining whether the measuring machine is screwed up to the exact _tightness_. would the measuring bars not compress a body a little before it appeared tight? workmen, when measuring a bar with callipers, often judge by the sense of touch whether the jaws of the callipers pass the bar with the proper amount of resistance; but when one has to deal with millionths of an inch, such a method would not suffice. so sir joseph whitworth introduced a _feeling-piece_, or _gravity-piece_. mr. t. m. goodeve thus describes it in _the elements of mechanism_: the gravity-piece consists of a small plate of steel with parallel plane sides, and having slender arms, one for its partial support, and the other for resting on the finger of the observer. one arm of the piece rests on a part of the bed of the machine, and the other arm is tilted up by the forefinger of the operator. the plane surfaces are then brought together, one on each side of the feeling-piece, until the pressure of contact is sufficient to hold it supported just as it remained when one end rested on the finger. this degree of tightness is perfectly definite, and depends on the weight of the gravity-piece, but not on the estimation of the observer. in this way the expansion due to heat when a 36-inch bar has been touched for an instant with the finger-nail may be detected. one of the most beautiful measuring machines commercially used comes from the factories of the pratt-whitney co., hartford, connecticut, the well-known makers of machine tools and gauges of all kinds. it is made in different sizes, the largest admitting an 80-inch bar. variations of 1/100,000 of an inch are readily determined by the use of this machine. it therefore serves for originating gauge sizes, or for duplicating existing standards. the adjusting screw has fifty threads to the inch, and its index-wheel is graduated to 400 divisions, giving an advance of 1/20,000 inch for each division: while by estimation this may be further subdivided to indicate one-half or even one-quarter of this small amount. delicacy of contact between the measuring faces is obtained by the use of auxiliary jaws holding a small cylindrical gauge by the pressure of a light helical spring which operates the sliding spindle to which one of these auxiliary jaws is attached. on one side of the "head" of the machine is a vertical microscope directed downwards on to a bar on the bed-plate, in which are a number of polished steel plugs graved with very fine central cross lines, each exactly an inch distant from either of its neighbours. a cross wire in the microscope tells when it is accurately abreast of the line below it. supposing, then, that a standard bar three inches in diameter has to be tested. the "head" is slid along until the microscope is exactly over the "zero" plug line, and the divided index-wheel is turned until the two jaws press each other with the minimum force that will hold up the feeling-piece. then the head is moved back and centred on the 3-inch line, and the bar to be tested is passed between the jaws. if the feeling-piece drops out it is too large, and the wheel is turned back until the jaws have been opened enough to let the bar through without making the feeling-piece fall. an examination of the index-wheel shows in hundred-thousandths of an inch what the excess diameter is. on the other hand, if the bar were too small, the jaws would need to be closed a trifle: this amount being similarly reckoned. we have now got into a region of very "practical politics," namely, the subject of _gauges_. all large engineering works which turn out machinery with interchangeable parts, _e.g._ screws and nuts, must keep their dimensions very constant if purchasers are not to be disgusted and disappointed. the small motor machinery so much in evidence to-day demands that errors should be kept within the ten-thousandth of an inch. an engineer therefore possesses a set of standard gauges to test the diameter and pitch of his screw threads and nuts; the size of tubes, wires; the circumference of wheels, etc. great inconvenience having been experienced by american railroad-car builders on account of the varying sizes of the screws and bolts which were used on the different tracks--though all were supposed to be of standard dimensions--the masters determined to put things right; and accordingly professors roger and bond and the pratt-whitney co. were engaged to work in collaboration in connection with the manufacture of tools for minute measurements, viz. to 1/50,000 inch. "to give an idea of what is implied by this, let it be supposed that a person should take a pair of dividing compasses and lay off 50,000 prick-marks 1/8 inch apart in a straight line. to do this the line would require to be over 520 feet, or nearly a tenth of a mile long. imagine that many prick-marks compressed into the space of an inch, and you have an imperfect idea of the minuteness of the measurements which can now be made by the pratt and whitney co."[3] the standard taps and dies were supplied to tool-makers and engineers, who could thus determine whether articles supplied to them were of the proper dimensions. nothing more was then heard of nuts being a "trifle small" or bolts "a leetle large." and so beautifully tempered were the dies made from the standards that one manufacturer claimed to have cut 18,800 cold-pressed nuts without any difference being perceptible in their sizes. to appreciate what the difference of a thousandth of an inch makes in a true fit, you should handle a set of plug and ring gauges; the ring a true half-inch internally, the plugs half-inch, half an inch less one ten-thousandth of an inch, and half an inch less one-thousandth, in diameter. the true half-inch plug needs to be forcibly driven into the ring on account of the friction between the surfaces. the next, if oiled, will slide in quite easily, but if left stationary a moment will "seize," and have to be driven out. the third will wobble very perceptibly, and would be at once discarded by a good workman as a bad fit. for extremely accurate measurements of rods, calliper gauges, shaped somewhat like the letter y, are used, the horns terminating in polished parallel jaws. such a gauge will detect a difference of 1/20,000 inch quite easily. so accurately can plug gauges be made by reference to a measuring machine, that a gold leaf 1/30,000 inch thick would be three times too thick to insert between the gauge and the jaws of the machine! you must remember that in high-class workmanship these gauges are constantly being used. as time goes on, the "limit of error" allowed in many classes of machine parts is gradually lessened, which shows the simultaneous improvement of all machinery used in the handling of metal. james watt was terribly hampered, when developing his steam-engine, by the difficulty of procuring a true cylinder for his pistons to work in with any approach to steam-tightness. his first cylinder was made by a smith of hammered iron soldered together. the next was cast and bored, but stuffing it with paper, cork, putty, pasteboard, and "old hat" proved useless to stem the leakage of steam. no wonder, considering that the finished cylinder was one-eighth of an inch larger in diameter at one end than at the other. watt was in advance of his time. neither machinery nor workmanship had progressed sufficiently to meet the requirements of the steam-engine. to-day an engineer would confidently undertake to bore a cylinder five feet in diameter with a variation from truth of not more than one five-hundredth of an inch. before passing from the subject of measuring machines, which play so important a part in modern mechanism, we may just glance at the electrical method of dr. p. e. shaw. he discovered recently that two clean metal surfaces can, by means of an electric current, feel one another on touching with a delicacy that far transcends that of the purely mechanical machine. the mechanism he employs is thus devised: a finely cut vertical screw having fifty threads to the inch has a disc graduated into 500 parts. the screw can be turned by means of a pulley string from a distance, and it is thus possible to give the top end of the screw a movement of 1/25,000 inch, when a movement corresponding to one graduation is made. this small movement is reduced by a train of six levers, the long arm of each bearing on the short arm of the one before it. the movement of the last lever of the train is thus reduced to 1/4,000 of that of the screw point, so a movement of 1/4,000 ã� 1/25,000 inch = 1/100,000,000 inch is obtained! how can such a movement be judged? a telephone and voltaic cell are joined to the last lever of the train and to the object whose movement is under examination. if they touch, the telephone sounds. an observer listens in the telephone, and if the object moves for any reason he can find out how much it moves by turning the screw until contact is made again. out of the many applications of this apparatus three may be given. (1) a short bar of iron when magnetised elongates about 1/1,000,000 of its length. if further magnetised it contracts. these changes can readily be measured with the instrument. (2) the smallest sound audible in the telephone is due to a movement of the diaphragm of the telephone by about 1/50,000,000 of an inch. this has been actually measured by dr. shaw and is by far the smallest distance ever directly recorded. it is about twice the diameter of the molecules of matter. (3) dispensing with levers, the screw alone is used for rougher work. dr. shaw has shown that one hundred-thousandth of an inch is the smallest dimension visible under a microscope. by fitting an electric measuring apparatus to the microscope carriage it becomes quite easy to measure minute distances. the microscope contains a cross wire which, when the object has been laid on the microscope stage, is centred on one side of the object. the electric contact screw is then advanced till it makes contact with the stage and a sound arises in the telephone. a reading of the screw disc having been taken, the screw is drawn in and the microscope stage is traversed sufficiently to bring the wire in line with the other side of the object. once more the operator makes electrical contact and gets a second reading, the difference between the two being the diameter of the object. in this manner the bacillus of tuberculosis has been proved to have an average diameter of 31/250,000 of an inch. the same method is employed to gauge the distance between the lines on a diffraction grating. footnotes: [1] april 19th, 1901. [2] g. m. bond in a lecture delivered before the franklin institute, february 29th, 1884. [3] _report on standard screw threads_, philadelphia, 1884. chapter ii calculating machines the simplest form of calculating machine was the abacus, on which the schoolboys of ancient greece did their sums. it consisted of a smooth board with a narrow rim, on which were arranged rows of pebbles, bits of bone or ivory, or silver coins. by replacing these little counters by sand, strewn evenly all over its surface, the abacus was transformed into a slate for writing or geometrical lessons. the romans took the abacus, along with many other spoils of conquest, from the greeks and improved it, dividing it by means of cross-lines, and assigning a multiple value to each line with regard to its neighbours. from their method of using the calculi, or pebbles, we derive our english verb, to _calculate_. during the middle ages the abacus still flourished, and it has left a further mark on our language by giving its name to the court of exchequer, in which was a table divided into chequered squares like this simple school appliance. step by step further improvements were made, most important among them being those of napier of merchiston, whose logarithms vex the heads of our youth, and save many an hour's calculation to people who understand how to handle them. sir samuel morland, gunter, and lamb invented other contrivances suitable for trigonometrical problems. gersten and pascal harnessed trains of wheels to their "ready-reckoners," somewhat similar to the well-known cyclometer. all these devices faded into insignificance when mr. charles babbage came on the scene with his famous calculator, which is probably the most ingenious piece of mechanism ever devised by the human brain. to describe the "difference engine," as it is called, would be impossible, so complicated is its character. dr. lardner, who had a wonderful command of language, and could explain details in a manner so lucid that his words could almost always be understood in the absence of diagrams, occupied twenty-five pages of the _edinburgh review_ in the endeavour to describe its working, but gave several features up as a bad job. another clever writer, dr. samuel smiles, frankly shuns the task, and satisfies himself with the following brief description:-"some parts of the apparatus and modes of action are indeed extraordinary--and, perhaps, none more so than that for ensuring accuracy in the calculated results--the machine actually correcting itself, and rubbing itself back into accuracy, by the friction of the adjacent machinery! when an error is made the wheels become locked and refuse to proceed; thus the machine must go rightly or not at all--an arrangement as nearly resembling volition as anything that brass and steel are likely to accomplish."[4] mr. babbage, in 1822, entered upon the task of superintending the construction of a machine for calculating and printing mathematical and astronomical tables. he began by building a model, which produced forty-four figures per minute. the next year the royal society reported upon the invention, which appeared so promising that the lords of the treasury voted mr. babbage â£1,500 to help him perfect his apparatus. he looked about for a first-rate mechanician of high intelligence as well as of extreme manual skill. the man he wanted appeared in mr. joseph clement, who had already made his name as the inventor of a drawing instrument, a self-acting lathe, a self-centring chuck, and fluted taps and dies. mr. clement soon produced special tools for shaping the various parts of the machine. so elaborate was the latter, that, according to dr. smiles, "the drawings for the calculating machinery alone--not to mention the printing machinery, which was almost equally elaborate--covered not less than four hundred square feet of surface!" you will easily imagine, especially if you have ever had a special piece of apparatus made for you by a mechanic, that the bills mounted up at an alarming rate; so fast, indeed, that the government began to ask, why this great expense, and so little visible result? after seven years' work the engineers' account had reached â£7,200, and mr. babbage had disbursed an additional â£7,000 out of his own pocket. mr. clement quarrelled with his employer--possibly because he harboured suspicions that they were both off on a wild-goose chase--and withdrew, taking all his valuable tools with him. the government soon followed his example, and poor babbage was left with his half-finished invention, "a beautiful fragment of a great work." it had been designed to calculate as far as twenty figures, but was completed only sufficiently to go to five figures. in 1862 it occupied a prominent place among the mechanical exhibits at the great exhibition. [illustration: a mechanical cashier the printing apparatus of a national cash register. it impresses on a paper strip the amount and nature of every money transaction; and also prints a date, number, advertisement, money value, and nature of business done on a ticket for the customer.] we learn, with some satisfaction, that all this effort was not fated to be fruitless. two scientists of stockholm--scheutz by name--were so impressed by dr. lardner's account of this calculating machine that they carried babbage's scheme through, and after twenty years of hard work completed a machine which seemed to be almost capable of thinking. the english government spent â£1,200 on a copy, which at somerset house entered upon the routine duty of working out annuity and other tables for the registrar-general. from babbage's wonderfully and fearfully made machine we pass to a calculator which to-day may be seen at work in hundreds of thousands of shops and offices. it is the most modern substitute for the open till; and, by the aid of marvellous interior works, acts as account-keeper and general detective to the money transactions of the establishment in which it is employed. there are very many types of cash register, and as it would be impossible to enumerate them all, we will pass at once to the most perfect type of all, known to the makers and vendors as "number 95." this register has at the top an oblong window. dotted about the surface confronting the operator are, in the particular machine under notice, fifty-seven keys; six bearing the letters a, b, d, e, h, k; three the words "paid out," "charge," "received on account"; and the others money values ranging from â£9 to 1/4d. these are arranged in vertical rows. at the left end of the instrument is a printing apparatus, kept locked by the proprietor; at the right end a handle and a small lever. below the register are six drawers, each labelled with an initial. a customer enters the shop, and buys goods to the value of 6s. 11d. an assistant, to whom belongs the letter h, receives a sovereign in payment. he goes to the register, and after making sure that his drawer is pushed in till it is locked, first presses down the key h, and then the keys labelled "6s." and "11d." suddenly, like two jacks-in-the-box, up fly into the window two tablets, with "6s. 11d." on both their faces, so that customer and assistant can see the figures. simultaneously a bell of a certain tone rings, drawer h flies open (so that he may place the money in it and give change, if necessary), and a rotating arm in the window shows the word "cash." the assistant now revolves the handle and presses the little lever. from a slot on the left side out flies a ticket, on the front of which is printed the date, a consecutive number, the assistant's letter, and the amount of the sale. the back has also been covered with an advertisement of some kind. the ticket and change are handed over to the customer, the drawer is shut, and the transaction is at an end, except for an entry in the shop's books of the article sold. a carrier next comes in with a parcel on which five-pence must be paid for transport. mr. a. receives the goods, goes to the register, presses his letter, the key with the words "paid out" on it, and the key carrying "5d.," takes out the amount wanted, and gives it to the carrier. again, a gentleman enters, and asks for change for half a sovereign. mr. b. obliges him, pressing down his letter, but no figures. fourthly, a debtor to the shop pays five shillings to meet an account that has been against him for some time. mr. k. receives the money and plays with the keys k, "received on account," and "5s.," giving a ticket receipt. lastly, a customer buys a pair of boots on credit. mr. d. attends to him, and though no cash is handled, uses the register, pressing the letter "charge," and, say, "16s. 6d." now what has been going on inside the machine all this time? let us lift up the cover, take off the case of the printing apparatus, and see. a strip of paper fed through the printing mechanism has on it five rows of figures, letters, etc., thus- s. d. h 6 11 pd. a 0 5 b 0 0 rc. k 5 0 ch. d 16 6 the proprietor is, therefore, enabled to see at a glance (1) who served or attended to a customer, (2) what kind of business he did with him, (3) the monetary value of the transaction. at the end of the day each assistant sends in his separate account, which should tally exactly with the record of the machine. simultaneously with the strip printing, special counting apparatus has been (a) adding up the total of all money taken for goods, (b) recording the number of times the drawer has been opened for each purpose. here, again, is a check upon the records. this ingenious machine not only protects the proprietor against carelessness or dishonesty on the part of his employã©s, but also protects the latter against one another. if only one drawer and letter were used in common, it would be impossible to trace an error to the guilty party. the lettering system also serves to show which assistant does the most business. where a cash register of this type is employed every transaction must pass through its hands--or rather mechanism. it would be risky for an assistant not to use the machine, as eyes may be watching him. he cannot open his drawers without making a record; nor can he make a record without first closing the drawers; so that he must _give a reason_ for each use of the register. if he used somebody else's letter, the ear of the rightful owner would at once be attracted by the note of his particular gong. when going away for lunch, or on business, a letter can be locked by means of a special key, which fits none of the other five locks. the printing mechanism is particularly ingenious. every morning the date is set by means of index-screws: and a consecutive numbering train is put back to zero. a third division accommodates a circular "electro" block for printing the advertisements, and a fourth division the figure wheels. the turn given to the handle passes a length of the ticket strip through, a slot--prints the date, the number of the ticket, an advertisement on the back, the assistant's letter, the nature of the business done, and feeds the paper on to the figures which give the finishing touch. a knife cuts off the ticket, and a special lever shoots it out of the slot. the national cash register company, for prudential reasons, do not wish the details of the internal machinery to be described; nor would it be an easy task even were the permission granted. so we must imagine the extreme intricacy of the levers and wheels which perform all the tasks enumerated, and turn aside to consider the origin and manufacture of the register, which are both of interest. the origin of the cash register is rather nebulous, because twenty-five years ago several men were working on the same idea. it first appeared as a practical machine in the offices of john and james ritty, who owned stores and coalmines at dayton, ohio. james ritty helped and largely paid for the first experiments. he needed a mechanical cashier for his own business, and says that, while on an ocean steamer _en route_ to london the revolving machinery gave him the suggestion worked out, on his return to dayton, in the first dial-machine. this gave way to the key-machine with its display tablet, or indicator, held up by a supporting bar moved back by knuckles on the vertical tablet rod. [illustration: fig. 1] the cut (fig. 1) shows the right side of this key register, the action of which is thus described by the national cash register company. the key a, when pressed with the finger at its ordinary position--marked 1--went down to the point marked 2. being a lever and pivoted to its centre, pressing down a key elevated its extreme point b. this pushed up the tablet-rod c, having on its upper part the knuckle d. this knuckle d, pushed up, took the position at e; that is, the knuckle pushed back the supporting-bar f, and was pushed past it and held above it. if the same operation were performed on another key, the knuckle on its vertical rod, going up, would again push the supporting bar back, which would release the first knuckled rod, and leave the last one in its place. this knuckled rod had on its upper end the display tablet, or indicator g. james and john ritty claimed and proved that they invented this, but the attorney for the dayton company (formed by them) in the supreme court was compelled to admit that this mechanism was old. yet if machines built like this were exhibited elsewhere, they were at most only experimental models, and none of them had ever gone into practical or commercial use. in fact, at this time nothing had been really contributed which was useful to the public or used by the public. the trouble was that the knuckles, being necessarily oiled, held dust and dirt which interfered with their free movement. and again, a "five-cent" or "ten-cent" key would be used more than others, and hence would become more worn. as a practical result the tablets did not drop when wanted, and the whole operation was thrown into confusion. when one tablet went up the other tablet stayed up, leaving a false indication. the most valuable modification now made by these dayton inventors was to cease to rely on the knuckle to move back the supporting bar, and to supply the place of this function by what became known as "connecting mechanism," especially designed for this purpose. this was placed at the other, or say the left, side of the machine as you faced it. cut no. 2 shows this new connecting mechanism. the keys, when pressed, performed the functions as before, on the right side of the machine, viz. to ring an alarm-bell, etc.; but on the other, or left, side the key, when pressed, operated the connecting mechanism marked m, n, o, p, and q. the key pressed down by its leverage pushed back a little lever (q), the further end of which pressed back the supporting bar f, and released the previously exposed indicator g, without relying on the knuckle to perform this function. the supreme court of the united states said that the suggestion or idea to correct the old trouble and to drop the display tablet with certainty, and to accomplish this _by dividing the force used_, and applying a portion of it to the new connecting mechanism on the left side of the machine, "was fine invention," and that "the results are so important, and the ingenuity displayed to bring them about is such that we are not disposed to deny the patentees the merit of invention. the combination described in the first claim was clearly new." to revert for a moment to the origin of the invention. mr. john ritty gives an account differing from that of his brother; but the two can probably be reconciled by supposing that the first ideas occurred simultaneously and were worked out in common. late one summer night, before dispersing home, a group of men were in his store. one of them said to the proprietor, "if you had a machine there to register the cash received, you would get more of it," and to the statement both owner and his clerks assented. this raised a laugh. but ritty who, in spite of a large business, which ranged over everything from a needle to a haystack, did not make much profit by his sales, took the suggestion seriously, and put on his thinking-cap, with the result that the first machine was patented, and profits became very greatly increased. [illustration: fig. 2] before his machine had been perfected a rival was in the field. mr. thomas carney, a man who had seen much life as a lumber merchant, captain during the civil war, explorer, and railroad promoter, settled down in 1884, at chicago, to the manufacture of coin-changers. "when in various businesses," he says, "we used gold and silver only, and it seemed to be a sheer necessity to have something of a money-changer to assist us in handling it and making change. the custom then was to throw the different coins into a special receptacle marked for each. i invented, and in my own shop built this coin-changer, the keys of which, when touched, would, through the tube, drop the coin into the hand as wanted. at chicago we made five or six hundred of these coin-changers, but by mistake placed the price too low, and after some conference i became assured that there was not enough money in it. a rich chicago manufacturer had become familiar with the urgent need of a cash register, and the losses which followed in business without one. the national, at dayton, had then been invented, but had not then been perfected as it has been since. parties at chicago agreed to put up the money if i would invent what would answer the purpose of a cash register and make a marketable machine. i went home and gave the matter some hard thinking, and talking with my son about the matter one night, i looked up at the clock and said, 'why, harry, there is the right thing. sixty minutes make an hour; one hundred cents make a dollar. all i have got to do is to change the wheels a little, put some keys into it, and there will be a thing which will register cents, dimes, and dollars, just as that clock will register time in minutes and hours.' in clocks the minute wheel, when it has revolved to its sixty point, throws its added result of sixty minutes over on to another wheel, which takes up the story, with one hour in place of the old sixty minutes. the first wheel then begins again and goes its round. a second complete revolution of the minute wheel throws another sixty minutes on to the hour, and gives one more hour registered, making two hours, and so on. i took some wheels, and with pasteboard made hands and a machine. it was very rough, but i took it to my friends and explained it to them. we went on, but encountering difficulties and obstacles, we merged our whole enterprise in the national. i followed it, and have since invented, worked, and helped along in the national cash register service. i developed the no. 35 machine which the company began on and uses yet. it is now in use in every civilised country, for it can be made to register english money and any decimal currency." in 1883 dayton contained five families. the following year colonel robert patterson bought a large property in the neighbourhood, and helped to develop a small town, which has since grown into a thriving manufacturing centre. his two sons, john h. patterson and frank j. patterson, bought out all the original proprietors of the national cash register, greatly improved the machine's mechanism, and built the huge factory which employs about 4,000 men, women, and girls, and is one of the best-equipped establishments in the world to promote both an economical output and the comfort of the employã©s. the company's buildings at dayton cover 892,144 square feet of floor-space, and utilise 140 acres of ground. in convenience and attractiveness, and for light, heat, and ventilation, and all sanitary things, these structures are designed to be models of any used for factory purposes. a machine is made and sold every 2-1/2 minutes in the dayton, berlin, and toronto factories collectively. according to its destination, it records dollars, shillings, marks, kronen, korona, francs, kroner, guildens, pesetas, pesos, milreis, rupees, or roubles. registers are also made to meet the needs of the celestials and the japanese. so necessary is it for these machines to be ever improving, that the company, with a wisdom that prevails more largely, perhaps, in the united states than elsewhere, offer substantial rewards to the employã© who records in a book kept specially for the purpose any suggestion which the committee, after due examination, consider likely to improve some detail of mechanism or manufacture. five departments are entirely devoted to experiments carried out by a corps of inventors working with a special body of skilled mechanics. new patents accrue so fast as a result of this organised research that the national company now owns 537 letters patent in the united states and 394 in foreign countries. many ideas come from outside. if they appear profitable they are bought and turned over to the patents department, which hands them on to the experimenters. these build an experimental model, which differs in many respects from the types hitherto manufactured. a cash register must be above all things strong, so that it can bear a heavy blow without getting out of order, and must retain its accuracy under all conditions. the model finished, it goes before the inspectors, who thump it, hammer it, almost turn it inside out, and send it back to the factory committee with reports on any defects that may have come to light. if the inspectors can only knock the machine out of time they consider that they have done their duty; for they argue that, if weaknesses thus developed are put right, no purchaser will ever be able to dislocate the machinery if he stops short of an actual "brutal assault with violence." next comes the building of the commercial type, which will be sold by the thousand. the machine goes down to the tool-makers, a select board of seventy-five members, who list all the parts, and say how many drill-jigs, mills, fixtures, gauges, etc., are necessary to make every part. then they draw out an approximate estimate of the cost of producing the tools, and after they have listed the parts, they turn them over to the various departments, such as the drafting-room, blacksmiths' shop, pattern shop, foundry, etc., after which the various parts are machined up. then the tool-maker assembles together the various tools, and makes a number of the parts that each tool is designed for; so that when all the tools have done their preliminary work, the makers possess about fifty machines "in bits." these are assembled, to prove whether the tools do their business efficiently. if any part shows an inclination "to jam," or otherwise misbehave itself, the tool responsible is altered till its products are satisfactory. then, and only then--a period of perhaps two years may have elapsed since the model was first put in hand--the company begins to entertain a prospect of getting back some of the money--any sum up to â£50,000--spent in preparations. but they know that if people will only buy, they won't have much fault to find with their purchase. "preparations brings success" is the motto of the n.c.r. so the company spares no money, and is content to have â£25,000 locked up in its automatic screw-making machines alone! human as well as inanimate machinery is well tended under the roof of the n.c.r. the committee believe that a healthy, comfortable employã© means good--and therefore profitable--work; and that to work well, employã©s must eat and play well. they therefore provide their boys with gardens, 10 feet wide by 170 feet in length; and pay an experienced gardener to direct their efforts. to encourage a start, bulbs, seeds, slips, etc., are supplied free; while prizes of considerable value help to stimulate competition. one day, ten years or more ago, mr. patterson saw a factory girl trying to warm her tin bucket of cold coffee at the steam heater in the workshop. he is a humane man, and acting on the unintentional hint he built a lunch-room which contains, besides accommodation for 455 people, a piano and sewing-machine which the women can use during their noon recess of eighty minutes. a cooking school, dancing classes, and literary club are all available to members. the company encourages its workers to own the houses they inhabit, and to make them as beautiful as their leisure will permit. mr. mosely, who took over to america an industrial commission of experts in 1902, and an educational commission in the following year, paid visits on both occasions to the national cash register works. in a speech to the committee he said: "i do not know of any institution in the world which offers so beautiful an illustration of the proper working conditions as the national cash register company. your president has asked me to criticise. i cannot find anything to criticise in this factory. i have never seen such conditions in any other factory in the world, nor have i ever seen so many bright and intelligent faces as we have seen at luncheon in both the men's and women's dining rooms. i believe this factory is as nearly perfect as social conditions will permit." note.--the author desires to express his thanks to the national cash register company for the kind help given him in the shape of materials for writing and illustrating this chapter. [illustration: _by permission of the sphere._ the jacket of a 12-inch gun being turned in a monster lathe at messrs. vickers maxim's works. notice the long spiral strip coming off the edge of the cutting tool.] footnote: [4] _industrial biographies_, chap. xiii. chapter iii workshop machinery the lathe--planing machines--the steam hammer--hydraulic tools--electrical tools in the shipyard "when i first entered this city," said mr. william fairbairn, in an inaugural address to the british association at manchester in 1861, "the whole of the machinery was executed by hand. there were neither planing, slotting, nor shaping machines, and with the exception of very imperfect lathes and a few drills, the preparatory operations of construction were effected entirely by the hands of the workmen. now, everything is done by machine tools, with a degree of accuracy which the unaided hand could never accomplish. the automaton, or self-acting, machine tool has within itself an almost creative power; in fact, so great are its powers of adaptation, that there is no operation of the human hand that it does not imitate." if such things could be said with justice forty-five years ago, what would mr. fairbairn think could he see the wonderful machinery with which the present-day workshop is equipped--machinery as relatively superior to the devices he speaks of as they were superior to the unaided efforts of the human hand? invention never stands still. the wonder of one year is on the scrap-heap of abandoned machines almost before another twelve months have passed. some important detail has been improved, to secure ease or economy in working, and a more efficient successor steps into its place. in his curious and original _erewhon_, mr. samuel butler depicts a community which, from the fear that machinery should become _too_ ingenious, and eventually drain away man's capacity for muscular and mental action, has risen in revolt against the automaton, broken up all machines which had been in use for less than 270 years--with the exception of specimens reserved for the national museums--and reverted to hand labour. his treatment of the dangers attending the increased employment of lifeless mechanisms as a substitute for physical effort does not, however, show sympathy with the erewhonians; since their abandonment of invention had obviously placed them at the mercy of any other race retaining the devices so laboriously perfected during the ages. and we, on our part, should be extremely sorry to part with the inanimate helpers which in every path of life render the act of living more comfortable and less toilsome. so dependent are we on machinery, that we owe a double debt to the machines which create machines. a big factory houses the parents which send out their children to careers of usefulness throughout the world. we often forget, in our admiration of the offspring, the source from which they originated. our bicycles, so admirably adapted to easy locomotion, owe their existence to a hundred delicate machines. the express engine, hurrying forward over the iron way, is but an assemblage of parts which have been beaten, cut, twisted, planed, and otherwise handled by mighty machines, each as wonderful as the locomotive itself. but then, we don't see these. this and following chapters will therefore be devoted to a few peeps at the great tools employed in the world's workshops. if you consider a moment, you will soon build up a formidable list of objects in which circularity is a necessary or desirable feature--wheels, shafts, plates, legs of tables, walking-sticks, pillars, parts of instruments, wire, and so on. the hindu turner, whose assistant revolves with a string a wooden block centred between two short spiked posts let into the ground, while he himself applies the tool, is at one end of the scale of lathe users; at the other, we have the workman who tends the giant machine slowly shaping the exterior of a 12-inch gun, a propeller shaft, or a marble column. all aim at the same object--perfect rotundity of surface. the artisans of the middle ages have left us, in beautiful balusters and cathedral screens, ample proofs that they were skilled workmen with the turning-lathe. at the time of the huguenot persecutions large numbers of french artificers crossed the channel to england, bringing with them lathes which could cut intricate figures by means of wheels, eccentrics and other devices of a comparatively complicated kind. the french had undoubtedly got far ahead of the english in this branch of the mechanical arts, owing, no doubt, to the fact that the french _noblesse_ had condescended to include turnery among their aristocratic hobbies. with the larger employment of metal in all industries the need for handling it easily is increased. much greater accuracy generally distinguishes metal as compared with woodwork. "in turning a piece of work on the old-fashioned lathe, the workman applied and guided his tool by means of muscular strength. the work was made to revolve, and the turner, holding the cutting tool firmly upon the long, straight, guiding edge of the rest, along which he carried it, and pressing its point firmly against the article to be turned, was thus enabled to reduce its surface to the required size and shape. some dexterous turners were able, with practice and carefulness, to execute very clever pieces of work by this simple means. but when the article to be turned was of considerable size, and especially when it was of metal, the expenditure of muscular strength was so great that the workman soon became exhausted. the slightest variation in the pressure of the tool led to an irregularity of surface; and with the utmost care on the workman's part, he could not avoid occasionally cutting a little too deep, in consequence of which he must necessarily go over the surface again to reduce the whole to the level of that accidentally cut too deep, and thus possibly the job would be altogether spoiled by the diameter of the article under operation being made too small for its intended purpose."[5] any modern worker is spared this labour and worry by the device known as the slide-rest. its name implies that it at once affords a rigid support for the tool, and also the means of traversing the tool in a straight line parallel to the metal face on which work is being done. the introduction of the slide-rest is due to the ingenuity of mr. henry maudslay, who, at the commencement of the nineteenth century, was a foreman in the workshop of mr. joseph bramah, inventor of the famous hydraulic press and locks which bear his name. his rest could be moved along the bed of the lathe by a screw, and clamped in any position desired. fellow-workmen at first spoke derisively of "maudslay's go-cart"; but men competent to judge its real value had more kindly words to say concerning it, when it had been adapted to machines of various types for planing as well as turning. mr. james nasmyth went so far as to state that "its influence in improving and extending the use of machinery has been as great as that produced by the improvement of the steam-engine in respect to perfecting manufactures and extending commerce, inasmuch as without the aid of the vast accession to our power of producing perfect mechanism which it at once supplied, we could never have worked out into practical and profitable forms the conceptions of those master minds who, during the last half century, have so successfully pioneered the way for mankind. the steam-engine itself, which supplies us with such unbounded power, owes its present perfection to this most admirable means of giving to metallic objects the most precise and perfect geometrical forms. how could we, for instance, have good steam-engines if we had not the means of boring out a true cylinder, or turning a true piston-rod, or planing a valve face? it is this alone which has furnished us with the means of carrying into practice the accumulated results of scientific investigation on mechanical subjects." the screw-cutting lathe is so arranged that the slide-rest is moved along with its tool at a uniform speed by gear wheels actuated by the mechanism rotating the object to be turned. by changing the wheels the rate of "feed" may be varied, so that at every revolution the tool travels from 1/64 of an inch upwards along the surface of its work. this regularity of action adds greatly to the value of the slide-rest; and the screw device also enables the workman to chase a thread of absolutely constant "pitch" on a metal bar; so that a screw-cutting lathe is not only a shaping machine but also the equivalent of a whole armoury of stocks and dies. some lathes have rests which carry several tools held at different distances from its axis, the cuts following one another deeper and deeper into the metal in a manner exactly similar to the harvesting of a field of corn by a succession of reaping machines. the recent improvements in tool-steel render it possible to get a much deeper cut than formerly, without fear of injury to the tool from overheating. this results in a huge saving of time. for the boring of large cylinders an upright lathe is generally used, as the weight of the metal might cause a dangerous "sag" were the cylinder attached horizontally by one end to a facing-plate. huge wheels can also be turned in this type of machine up to 20 feet or more in diameter; and where the cross-bar carrying the tools is fitted with several tool-boxes, two or more operations may be conducted simultaneously, such as the turning of the flange, the boring of the axle hole, and the facing of the rim sides. [illustration: a gun lathe. 154 feet long between centres, for boring and turning guns which, with their mountings, weigh 165 tons when complete. the makers are the niles-bement-pond co. of new york.] perhaps the most imposing of all lathes are those which handle large cannon and propeller shafts, such as may be seen in the works of sir w. g. armstrong, whitworth, and company; of messrs. vickers, sons and maxim; and of other armament and shipbuilding firms. the midvale steel company have in their shops at hamilton, ohio, a monster boring lathe which will take in a shaft 60 feet long, 30 inches in diameter, and bore a hole from one end to the other 14 inches in diameter. to do this, the lathe must attack the shaft at both ends simultaneously, as a single boring bar of 60 feet would not be stiff enough to keep the hole cylindrical. the shaft is placed in a revolving chuck in the central portion of the lathe--which has a total length of over 170 feet--and supported further by two revolving ring rests on each side towards the extremities. with work so heavy, the feeding up of the tool to its surface cannot be done conveniently by hand control, and the boring bars are therefore advanced by hydraulic pressure, a very ingenious arrangement ensuring that the pressure shall never become excessive. perhaps the type of lathe most interesting to the layman is the _turret_ lathe, generally used for the manufacture of articles turned out in great numbers. the headstock--_i.e._ the revolving part which grips the object to be turned--is hollow, so that a rod may be passed right through it into the vicinity of the tools, which are held in a hexagon "turret," one tool projecting from each of its sides. when one tool has been finished with, the workman does not have the trouble of taking it out of the rest and putting another in its place; he merely turns the turret round, and brings another instrument opposite the work. if the object--say a water-cock--requires five operations performing on it in the lathe, the corresponding tools are arranged in their proper order round the turret. stops are arranged so that as soon as any tool has advanced as far as is necessary a trip-action checks the motion of the turret, which is pulled back and given a turn to make it ready for the next attack. one of the advantages of the turret lathe, particularly of the automatic form which shifts round the tool-box without human intervention, is its power of relieving the operator of the purely mechanical part of his work. those who are familiar with the inside of some of our large workshops will have noticed men and boys who make the same thing all day and every day, and are themselves not far removed from machines. the articles they make are generally small and very rapidly produced, and the endless repetition of the same movements on the part of the operator is very tedious to watch, and must be infinitely more so to perform. such an occupation is not elevating, and those engaged in it cannot take much interest in their work, or become fitted for a better position. when this work is done by an automatic lathe the machine performs the necessary operations, and the man supplies the intelligence, and, by exercising his thinking powers, becomes more valuable to his employers and himself. the introduction of new machines and methods generally has a stimulating effect on the whole shop, whatever the erewhonians might say. the hubs and spindles of bicycles are cut from the solid bar by these automata; the tender has merely to feed them with metal, and they go on smoothing, shaping, and cutting off until the material is all used up. the existence of such lathes largely accounts for the low price of our useful metal steeds at the present time. a great amount of shaping is now done by milling cutters in preference to firmly-fixed edged tools. the cutter is a rod or disc which has its sides, end, or circumference serrated with deep teeth, shaped to the section of the cut needed. revolving at a tremendous speed, it quickly bites its way into anything it meets just so far as a stop allows it to go. one of the most ingenious machines to which the milling tool has been fitted is the well-known blanchard lathe, which copies, generally in wood, repetitive work, such as the stocks for guns and rifles. the lathe has two sets of centres--one for the copy, the other for the model--parallel on the same bed, and turned at equal speeds and in the same direction by a train of gear wheels. the milling cutter is attached to a frame, from which a disc projects, and is pressed by a spring against the model. as the latter revolves, its irregular shape causes the disc, frame, and cutter to move towards or away from its centre, and therefore towards or away from the centre of the copy, which has all superfluities whisked off by the cutter. the frame is gradually moved along the model, reproducing in the rough block a section similar to the part of the model which it has reached. the self-centring chuck is an accessory which has proved invaluable for saving time. it may most easily be described as a circular plate which screws on to the inner end of the mandrel (the spindle imparting motion to the object being machined) and has in its face three slots radiating from the centre at angles of 120â°. in each slot slides a stepped jaw, the under side of which is scored with concentric grooves engaging with a helical scroll turned by a key and worm gear acting on its circumference. the jaws approach or recede from the centre symmetrically, so that if a circular object is gripped, its centre will be in line with the axis of the lathe. whether for gripping a tiny drill or a large wheel, the self-centring chuck is indispensable. planing-machines not less important in engineering than the truly curved surface is the true plane, in which, as euclid would say, any two points being taken, the straight line between them lies wholly in that superficies. the lathe depends for its efficiency on the perfect flatness of all areas which should be flat--the guides, the surface plates, the bottom and sides of the headstock, and, above all, of the slide rest. for making plane metal superficies, a machine must first be constructed which itself is above suspicion; but when once built it creates machines like itself, capable of reproducing others _ad infinitum_. many amateur carpenters pride themselves on the beautiful smoothness of the boards over which they have run their jack planes. yet, as compared with the bed of a lathe, their best work will appear very inaccurate. the engineer's planing-machine in no way resembles its wooden relative. in the place of a blade projecting just a little way through a surface which prevents it from cutting too deep into the substance over which it is moving, we have a steel chisel very similar to the cutting tools of a lathe attached to a frame passing up and down over a bed to which the member holding the chisel is perfectly parallel. the article to be planed is rigidly attached to the bed and travels with it. between every two strokes the tool is automatically moved sideways, so that no two cuts shall be in the same line. after the whole surface has been "roughed," a finishing cutter is brought in action, and the process is repeated with the business edge of the tool rather nearer to the bed. joseph clement, a contemporary of babbage, maudslay, and nasmyth, is usually regarded as the inventor of the planing-machine. by 1825 he had finished a planer, in which the tool was stationary and the work moving under it on a rolling bed. two cutters were attached to the overhead cross rail, so that travel in either direction might be utilised. the bed of the machine, on which the work was laid, passed under the cutters on perfectly true rollers or wheels, lodged and held in their bearings as accurately as the best mandrel could be, and having set screws acting against their ends, totally preventing all end-motion. the machine was bedded on a massive and solid foundation of masonry in heavy blocks, the support at all points being so complete as effectually to destroy all tendency to vibration, with the object of securing full, round, and quiet cuts. the rollers on which the planing-machine travelled were so true, that clement himself used to say of them, "if you were to put a paper shaving under one of the rollers it would at once stop the rest." nor was this an exaggeration--the entire mechanism, notwithstanding its great size, being as true and accurate as a watch.[6] mr. clement next made a revolving attachment for the bed, in which bodies could be revolved under the cutter, on an axis parallel to the direction of travel. according to the wish of the operator, the object was converted into a cylinder, cone, or prism by its movements under the planing-tool. so efficient was the machine that it earned its maker upwards of ten pounds a day, at the rate of about eighteen shillings a square foot, until rivals appeared in the field and finally reduced the cost of planing to a few pence for the same area. there are two main patterns of planes now in general use. the first follows the original design of clement; the second has a fixed bed but a moving tool. where the work is very heavy, as in the case of armour-plates for battleships, the power required to suddenly reverse the motion of a vast mass of metal is enormous, many times greater than the energy expended on the actual planing. for this reason the moving-bed machines have had to be greatly improved; and in some cases replaced by fixed-bed planers. it is an impressive sight to watch one of these huge mechanisms reducing a rough plate, weighing twenty tons or more, to a smoothness which would shame the best billiard table. the machine, which towers thirty feet into the air and completely dwarfs the attendant, who has it as thoroughly under control as if it were a small file, bites great shining strips forty feet long, maybe, off the surface of the passive metal, and leaves a series of grooves as truly parallel as the art of man can make them. there is no fuss, no sticking, no stop, no noise; the force of electricity or steam, transmitted through wonderfully cut and arranged gear-wheels, is irresistible. the tool, so hard that a journey through many miles of steel has no appreciable effect on its edge, shears its way remorselessly over the surface which presently may be tempered to a toughness resembling its own. if you want to resharpen the tool, it will be no good to attack it with any known metal. but somewhere in the works there is a machine whose buzzing emery-wheels are more than a match for it, and rapidly grind the blunted edge into its former shape, so that it is ready to flay another plate, one skin at a time. planing-machines are of many shapes. some have an upright on each side of the bed limiting the width of the work they can take; others are open-sided, one support of extra strength replacing the two, enabling the introduction of a plate twice as broad as the bed. others, again, are built on the verge of a pit, so that they may cut the edges of an up-ended plate, and make it fit against its fellows so truly that you could not slip a sheet of paper edgeways between them. thus has man, so frail and delicate in himself, shaped metal till it can torture its kind to suit his will, which he makes known to it by opening this valve or pulling on that lever. not only does he flay it, but pierces it through and through; twists it into all manner of shapes; hacks masses off as easily as he would cut slices from a loaf; squeezes it in terrible presses to a fraction of its original thickness; and otherwise so treats it that we are glad that our scientific observations have as yet discovered no sentience in the substances reduced to our service. the steam hammer the scandinavian god thor was a marvellous blacksmith. thursday should remind us weekly of odin's son, from whose hammer flashed the lightning; and, through him, of vulcan, toiling at his smithy in the crater of vesuvius. in spite of the pictures drawn for us by pagan mythologists of their god-smiths, we are left with the doubt whether these beings, if materialised, might not themselves be somewhat alarmed by the steam hammer which mere mortals wield so easily. the forge is without dispute the "show-place" of a big factory, where huge blocks of metal feel the heavy hand of steam. as children we watched the blacksmith at his anvil, attracted and yet half-terrified by the spark-showers flying from a white-hot horseshoe. and even the adult, long used to startling sights, might well be fascinated and dismayed by the terrific blows dealt on glowing ingots by the mechanical sledge. [illustration: a steam hammer at work in woolwich arsenal, forging a steel ingot for the inner tube of a big gun. it delivers a blow equivalent to the momentum of a falling mass weighing 4000 tons. as speech is inaudible, the foreman gives hand signals to direct his men, who wear large canvas fingerless gloves to protect their hands from the intense heat.] james nasmyth, the inventor of this useful machine, was the son of a landscape painter, who from his earliest youth had taken great interest in scientific and mechanical subjects of all kinds. at fifteen he made a steam-engine to grind his father's paints, and five years later a steam carriage "that ran many a mile with eight persons on it. after keeping it in action two months," he says in an account of his early life, "to the satisfaction of all who were interested in it, my friends allowed me to dispose of it, and i sold it--a great bargain--after which the engine was used in driving a small factory. i may mention that in that engine i employed the waste steam to cause an increased draught by its discharge up the chimney. this important use of waste steam had been introduced by george stephenson some years before, though entirely unknown to me." this interesting peep at the infancy of the motor carriage reveals mechanical capabilities of no mean order in young james. he soon entered the service of mr. joshua field, henry maudslay's partner, and in 1834 set up a business on his own account at manchester. at this date the nearest approach to the modern steam hammer was the "tilt" hammer, operated by horse-, water-, or steam-power. it resembled an ordinary hand hammer on a very large scale, but as it could be raised only a small distance above its anvil, it became less effective as the size of the work increased, owing to the fall being "gagged." in 1837 mr. nasmyth interviewed the directors of the great western steamship company with regard to the manufacture of some unusually powerful tools which they needed for forging the paddle-shaft of the _great britain_. as the invention of the steam-engine had demanded the improvement of turning methods, so now the increase in the size of steamboats showed the insufficiency of forging machinery. mr. nasmyth put on his thinking-cap. evidently the thing needed was a method for raising a very heavy mass of metal easily to a good height, so that its great weight might fall with crushing force on the object between it and the anvil. how to raise it? brilliant idea! steam! in a moment nasmyth had mentally pictured an inverted steam cylinder rested on a solid upright overhanging the anvil and a block of iron attached to its piston-rod. all that would then be necessary was to admit steam to the under side of the piston until the block had risen to its full height, and to suddenly open a valve which would cut off the steam supply and allow the vapour already in the cylinder to escape. by the next post he sent a sketch to the company, who approved his design heartily, but were unable to use it, since the need for the paddle-shaft had already been nullified by the substitution of a screw as the motive power of their ship. poor nasmyth knew that he had discovered a "good thing," but british forge-masters, with a want of originality that amounted to sheer blind stupidity, refused to look at the innovation. "we have not orders enough to keep in work the forge-hammers we have," they wrote, "and we don't want any new ones, however improved they may be." his invention, therefore, appeared doomed to failure. help, however, came from france in the person of mr. schneider, founder of the famous creusot iron works, notorious afterwards as the birthplace of the boer "long toms." mr. nasmyth happened to be away when mr. schneider and a friend called at the manchester works, but his partner, mr. gaskell, showed the french visitors round the works, and also told them of the proposed steam hammer. the designs were brought out, so that its details might be clearly explained. years afterwards nasmyth returned the visit, and saw in the creusot works a crank-shaft so large that he asked how it had been forged. "by means of your steam hammer," came the reply. you may imagine nasmyth's surprise on finding the very machine at work in france which his own countrymen had so despised, and his delight over its obvious success. on returning home he at once raised money enough to secure a patent, protected his invention, and began to manufacture what has been described as "one of the most perfect of artificial machines and noblest triumphs of mind over matter that modern english engineers have developed." a few weeks saw the first--a 30-cwt.--hammer at work. people flocked to watch its precision, its beauty of action, and the completeness of control which could arrest it at any point of its descent so instantaneously as to crack without smashing a nut laid on the anvil. "its advantages were so obvious that its adoption soon became general, and in the course of a few years nasmyth steam hammers were to be found in every well-appointed workshop both at home and abroad."[7] nasmyth's invention was improved upon in 1853 by mr. robert wilson, his partner and successor. he added an automatic arrangement which raised the "tup," or head, automatically from the metal it struck, so that time was saved and loss of heat to the ingot was also avoided. the beauty of the "balance valve," as it was called, will be more clearly understood if we remember that the travel of the hammer is constantly increasing as the piece on the anvil becomes thinner under successive blows. under the influence of this very ingenious valve every variety of blow could be dealt. by simply altering the position of a tappet lever by means of two screws, a blow of the exact force required could be repeated an indefinite number of times. "it became a favourite amusement to place a wine-glass containing an egg upon the anvil, and let the block descend upon it with its quick motion; and so nice was its adjustment, and so delicate its mechanism, that the great block, weighing perhaps several tons, could be heard playing tap, tap upon the egg without even cracking the shell, when, at a signal given to the man in charge, down would come the great mass, and the egg and glass would be apparently, as walter savage landor has it, 'blasted into space.'"[8] later on mr. wilson added an equally important feature in the shape of a double-action hand-gear, which caused the steam to act on the top as well as the bottom of the piston, thus more than doubling the effect of the hammer. the largest hammer ever made was that erected by the bethlehem iron company of pennsylvania. the "tup" weighed 125 tons. after being in use for three years the owners consigned it to the scrap-heap, as inferior to the hydraulic press for the manufacture of armour-plate, though it had cost them â£50,000. they then erected in its stead, for an equal sum of money, a 14,000-ton pressure hydraulic press, which fitly succeeds it as the most powerful of its kind in the world. the change was made for three reasons. first, that the impact of so huge a block of metal necessitates the anvil being many times as heavy, and even then the shock to surrounding machinery may be very severe. secondly, the larger the forging to be hammered, the less is the reaction of the anvil, so that all the force of the blow tends to be absorbed by the side facing the hammer; whereas with a small bar the anvil's inertia would have almost as much effect as the actual blow. thirdly, the blow of the hammer is so instantaneous that the metal has not time to "flow" properly, and this leads to imperfect forgings, the surface of which may have been cracked. for very large work, therefore, the hammer is going out of fashion and the press coming in, though for lighter jobs it is still widely used. before leaving the subject we may glance at the double-headed horizontal hammer, such as is to be found in the forge-shop of the horwich railway works. two hammers, carried on rails and rollers, advance in unison from each side and pound work laid on a support between them. each acts as anvil to the other, while doing its full share of the work. so that not only is a great deal of weight saved, but shocks are almost entirely absorbed; while the fact that each hammer need make a blow of only half the length of what would be required from a single hammer, enables twice as many blows to be delivered in a given time. hydraulic tools before discussing these in detail we shall do well to trace the history of the bramah press, which may be said to be their parent, since the principle employed in most hydraulic devices for the workshop, as also the idea of using water as a means of transmitting power under pressure, are justly attributed to joseph bramah. if you take a dive into the sea and fall flat on the surface instead of entering at the graceful angle you intended, you will feel for some time afterwards as if an enemy had slapped you violently on the chest and stomach. you have learnt by sad experience that water, which seems to offer so little resistance to a body drawn slowly through it, is remarkably hard if struck violently. in fact, if enclosed, it becomes more incompressible than steel, without in any way losing its fluidity. we possess in water, therefore, a very useful agent for transmitting energy from one point to another. shove one end of a column of water, and it gives a push to anything at its other end; but then it must be enclosed in a tube to guide its operation. by a natural law all fluids press evenly on every unit of a surface that confines them. you may put sand into a bucket with a bottom of cardboard and beat hard upon the surface of the sand without knocking out the bottom. the friction between the sand particles and the bucket's sides entirely absorbs the blow. but if water were substituted for sand and struck with an object that just fitted the bucket so as to prevent the escape of liquid, the bottom, and sides, too, would be ripped open. the writer of this book once fired a candle out of a gun at a hermetically sealed tin of water to see what the effect would be. (another candle had already been fired through an iron plate 1/4 of an inch thick.) the impact _slightly_ compressed the water in the tin, which gave back all the energy in a recoil which split the sheet metal open and flung portions of it many feet into the air. but the candle never got through the side. this affords a very good idea of the almost absolute incompressibility of a liquid. we may now return to history. joseph bramah was born in 1748 at barnsley, in yorkshire. as the son of a farm labourer his lot in life would probably have been to follow the plough had not an accident to his right ankle compelled him to earn his living in some other way. he therefore turned carpenter and developed such an aptitude for mechanics that we find him, when forty years old, manufacturing the locks with which his name is associated, and six years later experimenting with the hydraulic press. this may be described simply as a large cylinder in which works a solid piston of a diameter almost equal to that of the bore, connected to a force pump. every stroke of the pump drives a little water into the cylinder, and as the water pressure is the same throughout, the total stress on the piston end is equal to that on the pump plunger multiplied by the number of times that the one exceeds the other in area. suppose, then, that the plunger is one inch in diameter and the piston one foot, and that a man drives down the plunger with a force of 1,000 lbs., then the total pressure on the piston end will be 144 ã� 1,000 lbs.; but for every inch that the plunger has travelled the piston moves only 1/144 of an inch, thus illustrating the law that what is gained in time is lost in power, and _vice versã¢_. the great difficulty encountered by bramah was the prevention of leakage between the piston and the cylinder walls. if he packed it so tightly that no water could pass, then the piston jammed; if the packing was eased, then the leak recommenced. bramah tried all manner of expedients without success. at last his foreman, henry maudslay--already mentioned in connection with the lathe slide-rest--conceived an idea which showed real genius by reason of its very simplicity. why not, he said, let the water itself give sufficient tightness to the packing, which must be a collar of stout leather with an inverted u-shaped section? this suggestion saved the situation. a recess was turned in the neck of the cylinder at the point formerly occupied by the stuffing-box, and into this the collar was set, the edges pointing downwards. when water entered under pressure it forced the edges in different directions, one against the piston, the other against the wall of the recess, with a degree of tightness proportioned to the pressure. as soon as the pressure was removed the collar collapsed, and allowed the piston to pass back into the cylinder without friction. a similar device, to turn to smaller things for a moment, is employed in a cycle tyre inflater, a cup-shaped leather being attached to the rear end of the piston to seal it during the pressure stroke, though acting as an inlet valve for the suction stroke. what we owe to joseph bramah and henry maudslay for their joint invention--the honour must be divided, like that of designing the steam hammer between nasmyth and wilson--it would indeed be hard to estimate. wherever steady but enormous effort is required for lifting huge girders, houses, ships; for forcing wheels off their axles; for elevators; for advancing the boring shield of a tunnel; for compressing hay, wool, cotton, wood, even metal; for riveting, bending, drilling steel plates--there you will find some modification of the hydraulic press useful, if not indispensable. however, as we are now prepared for a consideration of details, we may return to our workshop, and see what water is doing there. outside stands a cylindrical object many feet broad and high, which can move up and down in vertical guides. if you peep underneath, you notice the shining steel shaft which supports the entire weight of this tank or coffer filled with heavy articles--stones, scrap iron, etc. the shaft is the piston-plunger of a very long cylinder connected by pipes to pumping engines and hydraulic machines. it and the mass it bears up serves as a reservoir of energy. if the pumping engines were coupled up directly to the hydraulic tools, whenever a workman desired to use a press, drill, or stamp, as the case might be, he would have to send a signal to the engine-man to start the pumps, and another signal to tell him when to stop. this would lead to great waste of time, and a danger of injuring the tackle from over driving. but with an accumulator there is always a supply of water under pressure at command, for as soon as the ram is nearly down, the engines are automatically started to pump it up again. in short, the accumulator is to hydraulic machinery what their bag is to bagpipes, or the air reservoir to an organ. in large towns high-pressure water is distributed through special mains by companies who make a business of supplying factories, engineering works, and other places where there is need for it, though not sufficient need to justify the occupiers in laying down special pumping plant. london can boast five central distributing stations, where engines of 6,500 h.p. are engaged in keeping nine large accumulators full to feed 120 miles of pipes varying in diameter from seven inches downwards. the pressure is 700 lbs. to the square inch. liverpool has twenty-three miles of pipes under 850 lbs. pressure; manchester seventeen miles under 1,100 lbs. to these may be added glasgow, hull, birmingham, geneva, paris, berlin, antwerp, and many other large cities in both europe and the united states. for very special purposes, such as making metal forgings, pressures up to _twelve tons_ to the square inch may be required. to produce this "intensifiers" are used, _i.e._ presses worked from the ordinary hydraulic mains which pump water into a cylinder of larger diameter connected with the forging press. the largest english forging press is to be found in the openshaw works of sir w. g. armstrong, whitworth, and company. its duty is to consolidate armour-plate ingots by squeezing, preparatory to their passing through the rolling mills. it has one huge ram 78 inches in diameter, into the cylinder of which water is pumped by engines of 4,000 h.p., under a pressure of 6,720 lbs. to the square inch, which gives a total ram force of 12,000 tons. it has a total height of 33 feet, is 22 feet wide, and 175 feet long, and weighs 1,280 tons. on each side of the anvil is a trench fitted with platforms and machinery for moving the ingot across the ingot block. two 100-ton electric cranes with hydraulic lifting cylinders serve the press. [illustration: a huge hydraulic press the 12,000-ton pressure whitworth hydraulic press, used for consolidating steel ingots for armour-plating. water is forced into the ram cylinder at a pressure of three tons to the square inch. notice the man to the left of the press.] the bethlehem works "squeezer" has two rams, each of much smaller diameter than the armstrong-whitworth, but operated by a 10-1/2 tons pressure to the square inch. it handles ingots of over 120 tons weight for armour-plating. in 1895 mr. william corey, of pittsburg, took out a patent for toughening nickel steel plates by subjecting them, while heated to a temperature of 2,000â° f., to great compression, which elongates them only slightly, though reducing their thickness considerably. the heating of a large plate takes from ten to twenty hours; it is then ready to be placed between the jaws of the big press, which are about a foot wide. the plate is moved forward between the jaws after each stroke until the entire surface has been treated. at one stroke a 17-inch plate is reduced to 16 inches, and subsequent squeezings give it a final thickness of 14 inches. its length has meanwhile increased from 16 to 18-1/2 feet, or in that proportion, while its breadth has remained practically unaltered. a simple sum shows that metal which originally occupied 32-2/3 cubic inches has now been compressed into 31 cubic inches. this alteration being effected without any injury to the surface, a plate very tough inside and very hard outside is made. the plate is next reheated to 1,350â° f., and allowed to cool very gradually to a low temperature to "anneal" it. then once again the furnaces are started to bring it back to 1,350â°, when cold water is squirted all over the surface to give it a proper temper. if it bends and warps at all during this process, a slight reheating and a second treatment in the press restores its shape. the hydraulic press is also used for bending or stamping plates in all manners of forms. you may see 8-inch steel slabs being quietly squeezed in a pair of huge dies till they have attained a semicircular shape, to fit them for the protection of a man-of-war's big-gun turret; or thinner stuff having its ends turned over to make a flange; or still slenderer metal stamped into the shape of a complete steel boat, as easily as the tinsmith stamps tartlet moulds. in another workshop a pair of massive jaws worked by water power are breaking up iron pigs into pieces suitable for the melting furnace. the manufacture of munitions of war also calls for the aid of this powerful ally. take the field-gun and its ammunition. "the gun itself is a steel barrel, hydraulically forged, and afterwards wire-wound; the carriage is built up of steel plates, flanged and shaped in hydraulic presses; the wheels have their naves composed of hydraulically flanged and corrugated steel discs, and even the tyres are forced on cold by hydraulic tyre-setters, the rams of which are powerful enough to reduce the diameter of the welded tyre until the latter tightly nips the wheel. the shells for the gun are punched and drawn by powerful hydraulic presses, and the copper driving-bands are fixed on the projectiles in special hydraulic presses. quick-firing cartridge-cases are capped, drawn, and headed by an hydraulic press, whose huge mass always impresses the uninitiated as absurdly out of proportion to the small size of the finished case, and finally the cordite firing charge is dependent on hydraulic presses for its density and shape."[9] the press for placing the "driving-band" on a shell is particularly interesting. after the shell has been shaped and its exterior turned smooth and true, a groove is cut round it near the rear end. into this groove a band of copper is forced to prevent the leakage of gas from the firing charge past the shell, and also to bite the rifling which imparts a rotatory motion to the shell. the press for performing the operation has six cylinders and rams arranged spoke-wise inside a massive steel ring; the rams carrying concave heads which, when the full stroke is made, meet at the centre so as to form a complete circle. "pressure is admitted," says mr. petch, "to the cylinders by copper pipes connected up to a circular distributing pipe. the press takes water from the 700-pounds main for the first 3/8-inch of the stroke, and for the last 1/8-inch water pressure at 3 tons per square inch is used. the total pressure on all the rams to band a 6-inch shell is only 600 tons, but for a 12-inch shell no less than 2,800 tons is necessary." electric tools in a shipyard of late years electricity has taken a very prominent part in workshop equipment, on account of the ease with which it can be applied to a machine, the freedom from belting and overhead gear which it gives, and its greater economy. in a lathe-shop, where only half the lathes may be in motion at a time, the shafting and the belts for the total number is constantly whirling, absorbing uselessly a lot of power. if, however, a separate motor be fitted to each lathe, the workman can switch it on and off at his pleasure. the new york shipbuilding company, a very modern enterprise, depends mainly on electrical power for driving its machinery, in preference to belting, compressed air, or water. let us stroll through the various shops, and note the uses to which the current has been harnessed. before entering, our attention is arrested by a huge gantry crane, borne by two columns which travel on rails. from the cross girder, or bridge, 88 feet long, hang two lifting magnets, worked by 25 h.p. motors, which raise the load at the rate of 20 feet per minute. motors of equal power move the whole gantry along its rails over the great piles of steel plates and girders from which it selects victims to feed the maw of the shops. the main building is of enormous size, covering with its single roof no less than eighteen acres! just imagine four acres of skylights and two acres of windows, and you may be able to calculate the little glazier's bill that might result from a bad hailstorm. in this immense chamber are included the machine, boiler, blacksmith, plate, frame, pipe, and mould shops, the general storerooms, the building ways, and outfitting slips. "the material which enters the plate and storage rooms at one end, does not leave the building until it goes out as a part of the completed ship for which it was intended, when the vessel is ready to enter service; there are installed in one main building, and under one roof, all the material and machinery necessary for the construction of the largest ship known to commerce, and eight sets of ship-ways, built upon masonry foundations, covered by roofs of steel and glass, and spanned by cranes up to 100 tons lifting capacity, are practically as much a part of the immense main building as the boiler shop or machine shop."[10] a huge 100-ton crane of 121-foot span dominates the machine-shop and ship-ways at a height of 120 feet. it toys with a big engine or boiler, picking it up when the riveters, caulkers, and fitters have done their work, and dropping it gently into the bowels of a partly-finished vessel. a number of smaller cranes run about with their loads. those which handle plates are, like the big gantry already referred to, equipped with powerful electro-magnets which fix like leeches on the metal, and will not let go their hold until the current is broken by the pressing of a button somewhere on the bridge. sometimes several plates are picked up at once, and then it is pretty to see how the man in charge drops them in succession, one here, another there, by merely opening and closing the switch very quickly, so that the plate furthest from the magnets falls before the magnetism has passed out of the nearer plates. another interesting type is the extension-arm crane, which shoots out an arm between two pillars, grips something, and pulls it back into the main aisle, down which it travels without impediment. on every side are fresh wonders. here is an immense rolling machine, fed with plates 27 feet wide, which bends the 1-1/8-inch thick metal as if it were so much pastry; or turns over the edges neatly at the command of a 50 h.p. motor. there we have an electric plate-planer scraping the surface of a sheet half the length of a cricket pitch. as soon as a stroke is finished the bed reverses automatically, while the tool turns over to offer its edge to the metal approaching from the other side. all so quietly, yet irresistibly done! now mark these punches as they bite 1-1/4-inch holes through steel plates over an inch thick, one every two seconds. a man cutting wads out of cardboard could hardly perform his work so quickly and well. almost as horribly resistless is the circular saw which eats its way quite unconcernedly through bars six inches square, or snips lengths off steel beams. what is that strange-looking machine over there? it has three columns which move on circular rails round a table in the centre. up and down each column passes a stage carrying with it a workman and an electric drill working four spindles. look! here comes a crane with a boiler shell, the plates of which have been bolted in position. the crane lets down its load, end-up, on to the table, and trots off, while the three workmen move their columns round till the twelve drills are opposite their work. then whirr! a dozen twisted steel points, ranged in three sets of four, one drill above the other, bite into the boiler plates, opening out holes at mathematically correct intervals all down the overlapping seam-plates. this job done, the columns move round the boiler, and their drills pierce it first near the lower edge, then near the upper. the crane returns, grips the cylinder, and bears it off to the riveters, who are waiting with their hydraulic presses to squeeze the rivets into the holes just made, and shape their heads into neat hemispheres. as it swings through the air the size of the boiler is dwarfed by its surroundings; but if you had put a rule to it on the table you would have found that it measured 20 feet in diameter and as many in length. a few months hence furnaces will rage in its stomach, and cause it to force tons of steam into the mighty cylinders driving some majestic vessel across the atlantic. we pass giant lathes busy on the propeller shafts, huge boring mills which slowly smooth the interior of a cylinder, planers which face the valve slides; and we arrive, eye-weary, at the launching-ways where an ocean liner is being given her finishing touches. then we begin to moralise. that 600-foot floating palace is a concretion of parts, shaped, punched, cut, planed, bored, fixed by electricity. where does man come in? well, he harnessed the current, he guided it, he said "do this," and it did it. does not that seem to be his fair share of the work? footnotes: [5] _industrial biographies_, dr. s. smiles. [6] _industrial biographies._ [7] _industrial biographies._ [8] _chambers's encyclopã¦dia._ [9] mr. a. f. petch in _cassier's magazine_. [10] _cassier's magazine._ chapter iv portable tools "if the mountain won't come to mahomet," says the proverb, "mahomet must go to the mountain." this is as true in the workshop as outside;--mahomet being the tool, the mountain the work on which it must be used. with the increase in size of machinery and engineering material, methods half a century old do not, in many cases, suffice; especially at a time when commercial competition has greatly reduced the margin of profits formerly expected by the manufacturer. to take the case of a large shaft, which must have a slot cut along it on one side to accommodate the key-wedge, which holds an eccentric for moving the steam valves of a cylinder, or a screw-propeller, so that it cannot slip. the mass weighs, perhaps, twenty tons. one way of doing the job is to transport the shaft under a drill that will cut a hole at each end of the slot area, and then to turn it over to the planer for the intermediate metal to be scraped out. this is a very toilsome and expensive business, entailing the use of costly machinery which might be doing more useful work, and the sacrifice of much valuable time. inventors have therefore produced portable tools which can perform work on big bodies just as efficiently as if it had been done by larger machinery, in a fraction of the time and at a greatly reduced cost. to quote an example, the cutting of a key-way of the kind just described by big machines would consume perhaps a whole day, whereas the light, portable, easily attached miller, now generally used, bites it out in ninety minutes. pneumatic tools the best known of these is the pneumatic hammer. it consists of a cylinder, inside which moves a solid piston having a stroke of from half an inch to six inches. air is supplied through flexible tubing from a compressing pump worked by steam. the piston beats on a loose block of metal carried in the end of the tool, which does the actual striking. the piston suddenly decreases in diameter at about the centre of its length, leaving a shoulder on which air can work to effect the withdrawal stroke. by a very simple arrangement of air-ports the piston is made to act as its own valve. as the plane side of the piston has a greater area than that into which the piston-rod fits, the striking movement is much more violent than the return. under a pressure of several hundreds of pounds to the square inch a pneumatic hammer delivers upwards of 7,000 blows per minute; the quick succession of comparatively gentle taps having the effect of a much smaller number of heavier blows. for the flat hammer head can be substituted a curved die for riveting, or a chipping chisel, or a caulking iron, to close the seams of boilers. the riveter is peculiarly useful for ship and bridge-building work where it is impossible to apply an hydraulic tool. a skilled workman will close the rivet heads as fast as his assistant can place them in their holes; certainly in less than half the time needed for swing-hammer closing. even more effective proportionately is the pneumatic chipper. the writer has seen one cut a strip off the edge of a half-inch steel plate at the rate of several inches a minute. to the uninitiated beholder it would seem impossible that a tool weighing less than two stone could thus force its way through solid metal. the speed of the piston is so high that, though it scales but a few pounds, its momentum is great enough to advance the chisel a fraction of an inch, and the individual advances, following one another with inconceivable rapidity, soon total up into a big cut. automatic chisels are very popular with ornamental masons, as they lend themselves to the sculpturing of elaborate designs in stone and marble. their principle, modified to suit work of another character, is seen in percussive rock drills, such as the ingersoll sergeant. in this case the piston and tool are solid, and the air is let into the cylinder by means of slide valves operated by tappets which the piston strikes during its movements. some types of the rock-drill are controllable as to the length of their stroke, so that it can be shortened while the "entry" of the hole is being made and gradually increased as the hole deepens. for perpendicular boring the drill is mounted on a heavily weighted tripod, the inertia of which effectively damps all recoil from the shock of striking; for horizontal work, and sometimes for vertical, the support is a pillar wedged between the walls of the tunnel, or shaft. an ingenious detail is the rifled bar which causes the drill to rotate slightly on its axis between every two strokes, so that it may not jam. the drills are light enough to be easily erected and dismantled, and compact, so that they can be used in restricted and out-of-the way places, while their simplicity entails little special training on the part of the workman. with pneumatic and other power-drills the cost of piercing holes for explosive charges is reduced to less than one-quarter of that of "jumping" with a crowbar and sledgehammers. with the hand method two men are required, usually more; one man to hold, guide, and turn the drill; and the other, or others, to strike the blows with hammers. the machine, striking a blow far more rapidly than can be done by hand, reduces the number of operators to one man, and perhaps his helper. so durable is the metal of these wonderful little mechanisms that the delivery of 360,000 blows daily for months, even though each is given with a force of perhaps half a ton, fails to wear them out; or at the most only necessitates the renewal of some minor and cheap part. the debt that civilisation owes to the substitution of mechanical for hand labour will be fully understood by anyone who is conversant with the history of tunnel-driving and mining. another application of pneumatics is seen in the device for cutting off the ends of stay bolts of locomotive boilers. it consists of a cylinder about fifteen inches in diameter, the piston of which operates a pair of large nippers capable of shearing half-inch bars. the whole apparatus weighs but three-quarters of a hundredweight, yet its power is such that it can trim bolts forty times as fast as a man working with hammer and cold-chisel, and more thoroughly. then there is the machine for breaking the short bolts which hold together the outer and inner shells of the water-jacket round a locomotive furnace. a threaded bar, along which travels a nut, has a hook on its end to catch the bolt. the nut is screwed up to make the proper adjustment, and a pneumatic cylinder pulls on the hook with a force of many tons, easily shearing through the bolt. we must not forget the _pneumatic borer_ for cutting holes in wood or metal, or enlarging holes already existing. the head of the borer contains three little cylinders, set at an angle of 120â°, to rotate the drill, the valves opening automatically to admit air at very high pressures behind the pistons. any carpenter can imagine the advantage of a drill which has merely to be forced against its work, the movement of a small lever by the thumb doing the rest! next on the list comes the _pneumatic painter_, which acts on much the same principle as the scent-spray. mechanical painting first came to the fore in 1893, when the huge chicago exposition provided many acres of surfaces which had to be protected from the weather or hidden from sight. the following description of one of the machines used to replace hand-work is given in _cassier's magazine_: "the paint is atomized and sprayed on to the work by a stream of compressed air. from a small air-compressor the air is led, through flexible hose, to a paint-tank, which is provided with an air-tight cover and clamping screws. the paint is contained in a pot which can be readily removed and replaced by another when a different colour is required. this arrangement of interchangeable tins is also important as facilitating easy cleaning. the container is furnished with a semi-rotary stirrer, the spindle passing through a stuffing-box in the cover, and ending in a handle by which the whole thing complete may be carried about. the compressor is necessarily fixed or stationary, but the paint-tank, connected to it by the single air-hose, can be moved close to the work, while the length of hose from the tank to the nozzle gives the freedom of movement necessary. air-pressure is admitted to the tank by a bottom valve, and forces the paint up an internal pipe and along a hose from the tank to the spraying nozzle, to which air-pressure is also led by a second hose. the nozzle is practically an injector of special form. the flow of paint at the nozzle is controlled by a small plug valve and spring lever, on which the operator keeps his thumb while working, and which, on release, closes automatically. when it is required to change from one colour to another, or to use a different material, such as varnish, the can, previously in use, is removed, and air, or, if necessary, paraffin oil, is blown through the length of hose which supplies the paint until it is completely clean." the writer then mentions as an instance of the machine's efficiency that it has covered a 30 feet by 8 feet boiler in less than an hour, and that at one large bridge yard a 70 feet by 6 feet girder with all its projecting parts was coated with boiled oil in two hours--a job which would have occupied a man with a brush a whole day to execute. apart from saving time, the machine produces a surface quite free from brush marks, and easily reaches surfaces in intricate mouldings which are difficult to get at with a brush. the _pneumatic sand-jet_ is used for a variety of purposes: for cleaning off old paint, or the weathered surface of stonework; for polishing up castings and forgings after they have been brazed. at the cycle factory you will find the sand-jet hard at work on the joints of cycle frames, which must be cleared of all roughness before they are fit for the enameller. the writer, a few days before penning these lines, watched a jet removing london grime from the face of a large hotel. down a side street stood a steam-engine busily compressing air, which was led by long pipes to the jet, situated on some lofty scaffolding. the rapidity with which the flying grains scoured off smoke deposits attracted the notice of a large crowd, which gazed with upturned heads at the whitened stones. a peculiarity about the jet is that it proves much more effective on hard material than on soft, as the latter, by offering an elastic surface, robs the sand of its cutting power. after merely mentioning the _pneumatic rammer_ for forcing sand into foundry moulds, we pass to the _pneumatic sand-papering_ machine, which may be described briefly as a revolving disc carrying a circle of sand-paper on its face revolved between guards which keep it flat to its work. the disc flies round many hundreds of times per minute, rapidly wearing down the fibrous surface of the wood it touches. when the coarse paper has done its work a finely-grained cloth is substituted to produce the finish needful for painting. chapter v the pedrail: a walking steam-engine have you ever watched carefully a steam-roller's action on the road when it is working on newly laid stones? if you have, you noticed that the stones, gravel, etc., in front of the roller moved with a wave-like motion, so that the engine was practically climbing a never-ending hill. no wonder then that the mechanism of such a machine needs to be very strong, and its power multiplied by means of suitable gearing. again, suppose that an iron-tyred vehicle, travelling at a rapid pace, meets a large stone, what happens? either the stone is forced into the ground or the wheel must rise over it. in either case there will be a jar to the vehicle and a loss of propulsive power. do not all cyclists know the fatigue of riding over a bumpy road--fatigue to both muscles and nerves? as regards motors and cycles the vibration trouble has been largely reduced by the employment of pneumatic tyres, which _lap over_ small objects, and when they strike large ones minimise the shock by their buffer-like nature. yet there is still a great loss of power, and if pneumatic-tyred vehicles suffer, what must happen to the solid, snorting, inelastic traction-engine? on hard roads it rattles and bumps along, pulverising stones, crushing the surface. when soft ground is encountered, in sink the wheels, because their bearing surface must be increased until it is sufficient to carry the engine's weight. but by the time that they are six inches below the surface there will be a continuous vertical belt of earth six inches deep to be crushed down incessantly by their advance. how much more favourably situated is the railway locomotive or truck. _their_ wheels touch metal at a point but a fraction of an inch in length; consequently there is nothing to hamper their progression. so great is the difference between the rail and the road that experiment has shown that, whereas a pull of from 8 to 10 lbs. will move a ton on rails, an equal weight requires a tractive force of 50 to 100 lbs. on the ordinary turnpike. in order to obviate this great wastage of power, various attempts have been made to provide a road locomotive with means for laying its own rail track as it proceeds. about forty years ago mr. boydell constructed a wheel which took its own rail with it, the rails being arranged about the wheel like a hexagon round a circle, so that as the wheel moved it always rested on one of the hexagon's sides, itself flat on the ground. this device had two serious drawbacks. in the first place, the plates made a rattling noise which has been compared to the reports of a maxim gun; secondly, though the contrivance acted fairly well on level ground, it failed when uneven surfaces were encountered. thus, if a brick lay across the path, one end of a plate rested on the brick, the other on the ground behind, and the unsupported centre had to carry a sudden, severe strain. furthermore, the plates, being connected at the angles of the hexagon, could not tilt sideways, with the result that breakages were frequent. of late years another inventor, mr. j. b. diplock, has come forward with an invention which bids fair to revolutionise heavy road traffic. at present, though it has reached a practical stage and undergone many tests satisfactorily, it has not been made absolutely perfect, for the simple reason that no great invention jumps to finality all at once. are not engineers still improving the locomotive? the pedrail, as it has been named, signifies a rail moving on feet. mr. diplock, observing that a horse has for its weight a tractive force much in excess of the traction-engine, took a hint from nature, and conceived the idea of copying the horse's foot action. the reader must not imagine that here is a return to the abortive and rather ludicrous attempts at a walking locomotive made many years ago, when some engineers considered it proper that a railway engine should be _propelled_ by legs. mr. diplock's device not merely propels, but also steps, _i.e._ selects the spot on the ground which shall be the momentary point at which propulsive force shall be exerted. to make this clearer, consider the action of a wheel. first, we will suppose that the spokes, any number you please, are connected at their outer ends by flat plates. as each angle is passed the wheel falls flop on to the next plate. the greater the number of the spokes, the less will be each successive jar (or step); and consequently the perfect wheel is theoretically one in which the sides have been so much multiplied as to be infinitely short. a horse has practically two wheels, its front legs one, its back legs the other. the shoulder and hip joints form the axles, and the legs the spokes. as the animal pulls, the leg on the ground advances at the shoulder past the vertical position, and the horse would fall forwards were it not for the other leg which has been advanced simultaneously. each step corresponds to our many-sided wheel falling on to a flat side--and the "hammer, hammer, hammer on the hard high road" is the horsey counterpart of the metallic rattle. on rough ground a horse has a great advantage over a wheeled tractor, because it can put its feet down _on the top_ of objects of different elevations, and _still pull_. a wheel cannot do this, and, as we have seen, a loss of power results. our inventor, therefore, created in his pedrail a compromise between the railway smoothness and ease of running and the selective and accommodating powers of a quadruped. we must now plunge into the mechanical details of the pedrail, which is, strictly speaking, a term confined to the wheel alone. our illustration will aid the reader to follow the working of the various parts. in a railway we have (a) sleepers, on the ground, (b) rails attached to the sleepers, (c) wheels rolling over the rails. in the pedrail the order, reckoning upwards, is altered. on the ground is the _ped_, or movable sleeper, carrying wheels, over which a rail attached to the moving vehicle glides continuously. the _principle_ is used by anyone who puts wooden rollers down to help him move heavy furniture about. of course, the peds cannot be put on the ground and left behind; they must accompany their rollers and rails. we will endeavour to explain in simple words how this is effected. to the axles of the locomotive is attached firmly a flat, vertical plate, parallel to the sides of the fire-box. pivoted to it, top and bottom, at their centres, are two horizontal rocking arms; and these have their extremities connected by two bow-shaped bars, or cams, their convex edges pointing outwards, away from the axle. powerful springs also join the rocking arms, and tend to keep them in a horizontal position. thus we have a powerful frame, which can oscillate up and down at either end. the bottom arm is the rail on which the whole weight of the axle rests. the rotating and moving parts consist of a large, flat, circular case, the sides of which are a few inches apart. its circumference is pierced by fourteen openings, provided with guides, to accommodate as many short sliding spokes, which are in no way attached to the main axle. each spoke is shaped somewhat like a tuning-fork. in the v is a roller-wheel, and at the tip is a "ped," or foot. as the case revolves, the tuning-fork spokes pass, as it were, with a leg on each side of the framework referred to above; the wheel of each spoke being the only part which comes into contact with the frame. strong springs hold the spokes and rollers normally at an equal distance from the wheel's centre. it must now be stated that the object of the framework is to thrust the rollers outwards as they approach the ground, and slide them below the rail. the side-pieces of the frame are, as will be noticed (see fig. 3), eccentric, _i.e._ points on their surfaces are at different distances from the axle centre. this is to meet the fact that the distance from the axle to the ground is greater in an oblique direction than it is vertically, and therefore for three spokes to be carrying the weight at once, two of them must be more extended than the third. so then a spoke is moved outward by the frame till its roller gets under the rail, and as it passes off it it gradually slides inwards again. it will be obvious to the reader that, if the "peds" were attached inflexibly to the ends of their spokes they would strike the ground at an angle, and, of course, be badly strained. now, mr. diplock meant his "peds" to be as like feet as possible, and come down _flat_. he therefore furnished them with ankles, that is, ball-and-socket joints, so that they could move loosely on their spokes in all directions; and as such a contrivance must be protected from dust and dirt, the inventor produced what has been called a "crustacean joint," on account of the resemblance it bears to the overlapping armour-plates of a lobster's tail. the plates, which suggest very thin quoits, are made of copper, and can be renewed at small cost when badly worn. an elastic spring collar at the top takes up all wear automatically, and renders the plates noiseless. this detail cost its inventor much work. the first joint made represented an expenditure of â£6; but now, thanks to automatic machinery, any number can be turned out at 3s. 6d. each. a word about the feet. a wheel has fourteen of these. they are eleven inches in diameter at the tread, and soled with rubber in eight segments, with strips of wood between the segments to prevent suction in clay soil. the segments are held together by a malleable cast-iron ring around the periphery of the feet and a tightening core in the centre. these wearing parts, being separate from the rest of the foot, are easily and cheaply renewed, and repairs can be quickly effected, if necessary, when on the road. the surface in contact with the ground being composed of the three substances--metal, wood, and rubber, which all take a bearing, provides a combination of materials adapted to the best adhesion and wear on any class of road, or even on no road at all. [illustration: fig. 3] motive power is transmitted by the machinery to the wheel axle, from that to the casing, from the casing to the sliding spokes. as there are alternately two and three feet simultaneously in contact with the ground, the power of adhesion is very great--much greater than that of an ordinary traction-engine. this is what professor hele-shaw says in a report on a pedrail tractor: "the weight of the engine is spread over no less than twelve feet, each one of which presses upon the ground with an area immensely greater--probably as much as ten times greater--than that of all the wheels (of an ordinary traction-engine) taken together on a hard road. upon a soft road all comparison between wheels and the action of these feet ceases. the contact of each of the feet of the pedrail is absolutely free from all slipping action, and attains the absolute ideal of working, being merely placed in position without sliding to take up the load, and then lifted up again without any sliding to be carried to a new position on the road." it is necessary that the feet should come down flat on the ground. if they struck it at all edgeways they would "sprain their ankles"; otherwise, probably break off at the ball joint. mechanism was, therefore, introduced by which the feet would be turned over as they approached the ground, and be held at the proper angle ready for the "step." without the aid of a special diagram it would be difficult to explain in detail how this is managed; and it must suffice to say that the chief feature is a friction-clutch worked by the roller of the foot's spoke. to the onlooker the manner in which the pedrail crawls over obstacles is almost weird. the writer was shown a small working model of a pedrail, propelled along a board covered with bits of cork, wood, etc. the axle of the wheel scarcely moved upwards at all, and had he not actually seen the obstacles he would have been inclined to doubt their existence. an ordinary wheel of equal diameter took the obstructions with a series of bumps and bounds that made the contrast very striking. [illustration: fig. 4] an extreme instance of the pedrail's capacity would be afforded by the ascent of a flight of steps (see fig. 4). in such a case the three "peds" carrying the weight of an axle would not be on the same level. that makes no difference, because the frame merely tilts on its top and bottom pivots, the front of the rail rising to a higher level than the back end, and the back spokes being projected by the rail much further than those in front, so that the engine is simply levered over its rollers up an inclined plane. similarly, in descending, the front spokes are thrust out the furthest, and the reverse action takes place. with so many moving parts everything must be well lubricated, or the wear would soon become serious. the feet are kept properly greased by being filled with a mixture of blacklead and grease of suitable quality, which requires renewal at long intervals only. the sliding spokes, rollers, and friction-clutches are all lubricated from one central oil-chamber, through a beautiful system of oil-tubes, which provides a circulation of the oil throughout all the moving parts. the central oil-chamber is filled from one orifice, and holds a sufficient supply of oil for a long journey. we may now turn for a moment from the pedrail itself to the vehicles to which it is attached. here, again, we are met by novelties, for in his engines mr. diplock has so arranged matters, that not only can both front and back pairs of wheels be used as drivers, but both also take part in the steering. as may be imagined, many difficulties had to be surmounted before this innovation was complete. but that it was worth while is evident from the small space in which a double-steering tractor can turn, thanks to both its axles being movable, and from the increased power. another important feature must also be noticed, viz. that the axles can both tip vertically, so that when the front left wheel is higher than its fellow, the left back wheel may be lower than the right back wheel. in short, _flexibility_ and power are the ideals which mr. diplock has striven to reach. how far he has been successful may be gathered from the reports of experts. professor hele-shaw, f.r.s., says: "the pedrail constitutes, in my belief, the successful solution of a walking machine, which, whilst obviating the chief objections to the ordinary wheel running upon the road, can be made to travel anywhere where an ordinary wheel can go, and in many places where it cannot. at the same time it has the mechanical advantages which have made the railway system such a phenomenal success. it constitutes, in my belief, the solution of one of the most difficult mechanical problems, and deserves to be considered as an invention quite apart from any particular means by which it is actuated, whether it is placed upon a self-propelled carriage or a vehicle drawn by any agency, mechanical or otherwise.... the way in which all four wheels are driven simultaneously so as to give the maximum pulling effect by means of elastic connection is in itself sufficient to mark the engine as a most valuable departure from common practice. hitherto this driving of four wheels has never been successfully achieved, partly because of the difficulty of turning the steering-wheels, and partly because, until the present invention of mr. diplock, the front and hind wheels would act against each other, a defect at first experienced and overcome by the inventor in his first engine." [illustration: a pedrail tractor engaged in war office trials the inventor, mr. j. b. diplock, is standing on the left of the group. observe the manner in which the feet gradually assume a horizontal position as they approach the ground.] on january 8th, 1902, mr. diplock tried an engine fitted with two ordinary wheels behind and two pedrails in front. the authority quoted above was present at the trials, and his opinion will therefore be interesting. "the points which struck me immediately were (1) the marvellous ease with which it started into action, (2) the little noise with which it worked.... another thing which i noticed was the difference in the behaviour of the feet and wheels. the feet did not in any way seem to affect the surface of the road. throwing down large stones the size of the fist into their path, the feet simply set themselves to an angle in passing over the stones, and did not crush them; whereas, the wheel coming after invariably crushed the stones, and, moreover, distorted the road surface. "coming to the top of the hill, i made the pedrail walk first over 3-inch planks, then 6-inch, and finally over a 9-inch balk.... one could scarcely believe, on witnessing these experiments, that the whole structure was not permanently distorted and strained, whereas it was evidently within the limits of play allowed by the mechanism. as a proof of this the diplock engine walked down to the works, and i then witnessed its ascent of a lane, beside the engineering works, which had ruts eight or ten inches deep, and was a steep slope. this lane was composed in places of the softest mud, and whereas the wheels squeezed out the ground in all directions, the feet of the pedrails set themselves at the angles of the rut where it was hard, or walked through the soft and yielding mud without making the slightest disturbance of the surrounding ground.... i came away from that trial with the firm conviction that i had seen what i believe to be the dawn of a new era in mechanical transport." mr. diplock does not regard the pedrail as an end in itself so much as a means to an end, viz. the development of road-borne traffic. for very long distances which must be covered in a minimum of time the railway will hold its own. but there is a growing feeling that unless the railways can be fed by subsidiary methods of transport more effectively than at present, and unless remote country districts, whither it would not pay to carry even a light railway, are brought into closer touch with the busier parts, our communications cannot be considered satisfactory, and we are not getting the best value out of our roads. for many classes of goods _cheapness_ of transportation is of more importance than _speed_; witness the fact that coal is so often sent by canal rather than by rail. here, then, is the chance for the pedrail tractor and its long train of vehicles fitted with pedrail wheels, which will tend to improve the road surfaces they travel over. mr. diplock sets out in his interesting book, _a new system of heavy goods transport on common roads_, a scheme for collecting goods from "branch" routes on to "main" routes, where a number of cars will be coupled up and towed by powerful tractors. with ordinary four-wheeled trucks it is difficult to take a number round a sharp corner, since each truck describes a more sudden circle than its predecessor, the last often endeavouring to climb the pavement. four-wheeled would therefore be replaced by two-wheeled trucks, provided with special couplings to prevent the cars tilting, while allowing them to turn. cars so connected would follow the same track round a curve. the body of the car would be removable, and of a standard size. it could be attached to a simple horse frame for transport into the fields. there the farmer would load his produce, and when the body was full it would be returned to the road, picked up by a crane attached to the tractor, swung on to its carriage and wheels, and taken away to join other cars. by making the bodies of such dimensions as to fit three into an ordinary railway truck, they could be entrained easily. on reaching their destination another tractor would lift them out, fit them to wheels, and trundle them off to the consumer. by this method there would be no "breaking bulk" of goods required from the time it was first loaded till it was exposed in the market for sale. these things are, of course, in the future. of more present importance is the fact that the war office has from the first taken great interest in the new invention, which promises to be of value for military transport over ground either rough or boggy. trials have been made by the authorities with encouraging results. that daring writer, mr. h. g. wells, has in his _land ironclads_ pictured the pedrail taking an offensive part in warfare. huge steel-plated forts, mounted on pedrails, and full of heavy artillery and machine guns, sweep slowly across the country towards where the enemy has entrenched himself. the forts are impervious alike to shell and bullet, but as they cross ditch or hillock in their gigantic stride, their artillery works havoc among their opponents, who are finally forced to an unconditional surrender. even if the pedrail is not made to carry weapons of destruction, we can, after our experiences with horseflesh in the boer war, understand how important it may become for commissariat purposes. the feats which it has already performed mark it as just the locomotive to tackle the rough country in which baggage trains often find themselves. to conclude with a more peaceful use for it. when fresh country is opened up, years must often pass before a proper high road can be made, yet there is great need of an organised system of transport. whither ordinary traction-engines, or carts, even horses, could scarcely penetrate, the pedrail tractor, thanks to its big, flat feet, which give it, as someone has remarked, the appearance of "a cross between a traction-engine and an elephant," will be able to push its way at the forefront of advancing civilisation. at home we shall have good reason to welcome the pedrail if it frees us from those terrible corrugated tracks so dreaded by the cyclist, and to bless it if it actually beats our roads down into a greater smoothness than they now can boast. chapter vi internal combustion engines oil engines--engines worked with producer gas--blast furnace gas engines if carbon and oxygen be made to combine chemically, the process is accompanied by the phenomenon called _heat_. if heat be applied to a liquid or gas in a confined space it causes a violent separation of its molecules, and power is developed. in the case of a steam-engine the fuel is coal (carbon in a more or less pure form), the fluid, water. by burning the fuel under a boiler, a gas is formed which, if confined, rapidly increases the pressure on the walls of the confining vessel. if allowed to pass into a cylinder, the molecules of steam, struggling to get as far as possible from one another, will do useful work on a piston connected by rods to a revolving crank. we here see the combustion of fuel external to the cylinder, i.e. under the boiler, and the fuel and fluid kept apart out of actual contact. in the gas or oil-vapour engine the fuel is brought into contact with the fluid which does the work, mixed with it, and burnt _inside_ the cylinder. therefore these engines are termed _internal combustion_ engines. supposing that a little gunpowder were placed in a cylinder, of which the piston had been pushed almost as far in as it would go, and that the powder were fired by electricity. the charcoal would unite with the oxygen contained in the saltpetre and form a large volume of gas. this gas, being heated by the ignition, would instantaneously expand and drive out the piston violently. a very similar thing happens at each explosion of an internal combustion engine. into the cylinder is drawn a charge of gas, containing carbon, oxygen, and hydrogen, and also a proportion of air. this charge is squeezed by the inward movement of the piston; its temperature is raised by the compression, and at the proper moment it is ignited. the oxygen and carbon seize on one another and burn (or combine), the heat being increased by the combustion of the hydrogen. the air atoms are expanded by the heat, and work is done on the piston. but the explosion is much gentler than in the case of gunpowder. during recent years the internal combustion engine has been making rapid progress, ousting steam power from many positions in which it once reigned supreme. we see it propelling vehicles along roads and rails, driving boats through the water, and doing duty in generating stations and smelting works to turn dynamos or drive air-pumps--not to mention the thousand other forms of usefulness which, were they enumerated here, would fill several pages. a decade ago an internal combustion engine of 100 h.p. was a wonder; to-day single engines are built to develop 3,000 h.p., and in a few years even this enormous capacity will doubtless be increased. it is interesting to note that the rival systems--gas and steam--were being experimented with at the same time by robert street and james watt respectively. while watt applied his genius to the useful development of the power latent in boiling water, street, in 1794, took out letters patent for an engine to be worked by the explosions caused by vaporising spirits of turpentine on a hot metal surface, mixing the vapour with air in a cylinder, exploding the mixture, and using the explosion to move a piston. in his, and subsequent designs, the mixture was pumped in from a separate cylinder under slight pressure. lenoir, in 1860, conceived the idea of making the piston _suck_ in the charge, so abolishing the need of a separate pump; and many engines built under his patents were long in use, though, if judged by modern standards, they were very wasteful of fuel. two years later alphonse beau de rochas proposed the further improvement of utilising the cylinder, not only as a suction pump, but also as a compressor; since he saw that a compressed mixture would ignite very much more readily than one not under pressure. rochas held the secret of success in his grasp, but failed to turn it to practical account. the "otto cycle," invented by dr. otto in 1876, is really only rochas's suggestion materialised. the large majority of internal combustion engines employ this "cycle" of operations, so we may state its exact meaning:-(1) a mixture of explosive gas and air is drawn into the cylinder by the piston as it passes outwards (i.e. in the direction of the crank), through the inlet valve. (2) the valve closes, and the returning piston compresses the mixture. (3) the mixture is fired as the piston commences its second journey outwards, and gives the "power" stroke. (4) the piston, returning again, ejects the exploded mixture through the outlet or exhaust valve, which began to open towards the end of the third stroke. briefly stated, the "cycle" is--suction, compression, explosion, expulsion; one impulse being given during each cycle, which occupies two complete revolutions of the fly-wheel. since the first, second, and third operations all absorb energy, the wheel must be heavy enough to store sufficient momentum during the "power" stroke to carry the piston through all its three other duties. year by year, the compression of the mixture has been increased, and improvements have been made in the methods of governing the speed of the engine, so that it may be suitable for work in which the "load" is constantly varying. by doubling, trebling, and quadrupling the cylinders the drive is rendered more and more steady, and the elasticity of a steam-engine more nearly approached. the internal combustion engine has "arrived" so late because in the earlier part of last century conditions were not favourable to its development. illuminating gas had not come into general use, and such coal gas as was made was expensive. the great oil-fields of america and russia had not been discovered. but while the proper fuels for this type of motor were absent, coal, the food of the steam-engine, lay ready to hand, and in forms which, though useless for many purposes, could be advantageously burnt under a boiler. now the situation has altered. gas is abundant; and oil of the right sort costs only a few pence a gallon. inventors and manufacturers have grasped the opportunity. to-day over 3,000,000 h.p. is developed continuously by the internal combustion engine. steam would not have met so formidable a rival had not that rival had some great advantages to offer. what are these? well, first enter a factory driven by steam power, and carefully note what you see. then visit a large gasor oil-engine plant. you will conclude that the latter scores on many points. there are no stokers required. no boilers threaten possible explosions. the heat is less. the dust and dirt are less. the space occupied by the engines is less. there is no noisome smoke to be led away through tall and expensive chimneys. if work is stopped for an hour or a day, there are no fires to be banked or drawn--involving waste in either case. above all, the gas engine is more efficient, or, if you like to express the same thing in other words, more economical. if you use only one horse-power for one hour a day, it doesn't much matter whether that horse-power-hour costs 4d. or 5d. but in a factory where a thousand horse-power is required all day long, the extra pence make a big total. if, therefore, the proprietor finds that a shilling's-worth of gas or oil does a quarter as much work again as a shilling's-worth of coal, and that either form of fuel is easily obtained, you may be sure that, so far as economy is concerned, he will make up his mind without difficulty as to the class of engine to be employed. a pound of coal burnt under the best type of steam-engine gives but 10 per cent. of its heating value in useful work. a good oil-engine gives 20-25 per cent., and in special types the figures are said to rise to 35-40 per cent. we may notice another point, viz. that, while a steam-engine must be kept as hot as possible to be efficient, an internal combustion engine must be cooled. in the former case no advantage, beyond increased efficiency, results. but in the latter the water passed round the cylinders to take up the surplus heat has a value for warming the building or for manufacturing processes. putting one thing with another, experts agree that the explosion engine is the prime mover of the future. steam has apparently been developed almost to its limit. its rival is but half-grown, though already a giant. some internal combustion engines use petroleum as their fuel, converting it into gas before it is mixed with air to form the charge; others use coal-gas drawn from the lighting mains; "poor gas" made in special plants for power purposes; or natural gas issuing from the ground. natural gas occurs in very large quantities in the united states, where it is conveyed through pipes under pressure for hundreds of miles, and distributed among factories and houses for driving machinery, heating, and cooking. in england and europe the petroleum engine and coal-gas engine have been most utilised; but of late the employment of smelting-furnace gases--formerly blown into the air and wasted--and of "producer" gas has come into great favour with manufacturers. the latest development is the "suction" gas engine, which makes its own gas by drawing steam and air through glowing fuel during the suction stroke. we will consider the various types under separate headings devoted (1) to the oil-fuel engine, (2) the producer-gas engine and the suction-gas engine, (3) blast-furnace gas engines, with reference to the installations used in connection with the last two. all explosion engines (excepting the very small types employed on motor cycles) have a water-jacket round the cylinders to absorb some of the heat of combustion, which would otherwise render the metal so hot as to make proper lubrication impossible, and also would unduly expand the incoming charge of gas and air before compression. the ideal engine would take in a full charge of cold mixture, which would receive no heat from the walls of the cylinder, and during the explosion would pass no heat through the walls. in other words, the ideal metal for the cylinders would be one absolutely non-receptive of heat. in the absence of this, engineers are obliged to make a compromise, and to keep the cylinder at such a temperature that it can be lubricated fittingly, while not becoming so cold as to absorb _too much_ of the heat of explosion. oil engines these fall into two main classes:-(a) those using light, volatile, mineral oils--such as petrol and benzoline--and alcohol, a vegetable product. (b) those using heavy oils, such as paraffin oil (kerosene) and the denser constituents of rock-oil left in the stills after the kerosene has been driven off. american petroleum is rich in burning-oil and petrol; russian in the very heavy residue, called _astakti_. given the proper apparatus for vaporisation, mineral oils of any density can be used in the explosion engine. the first class is so well known as the mover of motor vehicles and boats that we need not linger here on it. it may, however, be remarked that engines using the easily-vaporised oils are not of large powers, since the fuel is too expensive to make them valuable for installations where large units of power are needed. they have been adopted for locomotives on account of their lightness, and the ease with which they can be started. petrol vaporises at ordinary temperatures, so that air merely passed over the spirit absorbs sufficient vapour to form an explosive mixture. the "jet" carburetter, now generally employed, makes the mixture more positive by atomising the spirit as it passes through a very fine nozzle into the mixing chamber under the suction from the cylinder. on account of their small size spirit engines work at very high speeds as compared with the large oil or gas engine. thus, while a 2,000 h.p. kã¶rting gas engine develops full power at eighty-five revolutions a minute, the tiny cycle motor must be driven at 2,000 to 3,000 revolutions. speaking generally, as the size increases the speed decreases. of heavy oil engines there are some dozens of well-tried types. they differ in their methods of effecting the following operations. 1. the feeding of the oil fuel to the engine. 2. the conversion of the oil into vapour. 3. the ignition of the charge. 4. the governing of speed. all these engines have a vaporiser, or chamber wherein the oil is converted into gas by the action of heat. when starting-up the engine, this chamber must be heated by a specially designed lamp, similar in principle to that used by house painters for burning old paint off wood or metal. let us now consider the operations enumerated above in some detail. 1. _the oil supply._ fuel is transferred from the storage tank to the vaporiser either by the action of gravity through a regulating device to prevent "flooding," or by means of a small pump, or by the suction of the piston, which _lifts_ the liquid. in some engines the air and gas enter the cylinder through a single valve; in others through separate valves. 2. _vaporisation._ as already remarked, the vaporising chamber must be heated to start the engine. when work has begun the lamp may be removed if the engine is so designed that the chamber stores up sufficient heat in its walls from each explosion to vaporise the charge for the next power stroke. the crossley engine has a lamp continuously burning; the hornsby-ackroyd depends upon the storage of heat from explosions in a chamber opening into the cylinder. the best designs are fairly equally divided between the two systems. 3. _ignition_ of the compressed charge is effected in one of four ways: by bringing the charge, at the end of the compression stroke, into contact with a closed tube projecting from the cylinder and heated outside by a continuously burning lamp; by the heat stored in some part of the combustion chamber (_i.e._ that portion of the cylinder not swept by the piston); by an electric spark; or by the mere heat of compression. the second and third methods are confined to comparatively few makes; and the diesel oil engine (of which more presently) has a monopoly of the fourth. 4. _governing._ all engines which turn machinery doing intermittent work--such as that of a sawmill, or electric generating plant connected with a number of motors--must be very carefully guarded from overrunning. imagine the effect on an engine which is putting out its whole strength and getting full charges of fuel, if the belt suddenly slipped off and it were "allowed its head." a burst fly-wheel would be only one of the results. the steam-engine is easily controlled by the centrifugal action of a ball-governor, which, as the speed increases, gradually spreads its balls and lifts a lever connected with a valve in the steam supply pipe. owing to its elastic nature, steam will do useful work if admitted in small quantities to the cylinder. but a difficulty arises with the internal combustion engine if the _supply_ of mixture is similarly throttled, because a loss of quantity means loss of compression and bad ignition. many oil engines are therefore governed by apparatus which, when the speed exceeds a certain limit, cuts off the supply altogether, either by throwing the oil-pump temporarily out of action, or by lifting the exhaust valve so that the movement of the piston causes no suction--the "hit-and-miss" method, as it is called. the means adopted depends on the design of the engine; and it must be said that, though all the devices commonly used effect their purpose, none are perfect; this being due rather to the nature of an internal explosion engine than to any lack of ingenuity on the part of inventors. the steadiest running is probably given with the throttle control, which diminishes the supply. on motor cars this method has practically ousted the "hit-and-miss" governed exhaust valve; but in stationary engines we more commonly find the speed controlled by robbing the mixture of the explosive gas in inverse proportion to the amount of the work required from the engine. the diesel oil engine, on account of some features peculiar to it, is treated separately. in 1901 an expert wrote of it that "the engine has not attained any commercial position." herr rudolph diesel, the inventor, has, however, won a high place for his prime-mover among those which consume liquid fuel, on account of its extraordinary economy. the makers claim--as the result of many tests--that with the crude rock-oil (costing in bulk about 2d. a gallon) which it uses, a horse-power can be developed for one hour by this engine for _one-tenth of a penny_. the daily fuel bill for a 100 h.p. engine running ten hours per day would therefore be 8s. 4d. to compete with the diesel engine a steam installation would have to be of the very highest class of triple-expansion type, of not less than 400 h.p., and using every hour per horse-power only 1-3/4 lbs. of coal at 9s. per ton. very few large steam-engines work under conditions so favourable, and with small sizes 3-4 lbs. of coal would be burnt for every "horse-power-hour." the diesel differs from other internal combustion engines in the following respects:- 1. it works with very much higher compression. 2. the ignition is spontaneous, resulting from the high compression of the charge alone. 3. the fuel is not admitted into the cylinder until the power-stroke begins, and enters in the form of a fine spray. 4. the combustion of the fuel is much slower, and therefore gives a more continuous and elastic push to the piston. the engine works on the ordinary otto cycle. to start it, air compressed in a separate vessel is injected into the cylinder. the piston flies out, and on its return squeezes the air to about 500 lbs. to the square inch, thus rendering it incandescent.[11] just as the piston begins to move out again a valve in the cylinder-head opens, and a jet of pulverised oil is squirted in by air compressed to 100 lbs. per square inch more than the pressure in the cylinder. the vapour, meeting the hot air, burns, but comparatively slowly: the pressure in the cylinder during the stroke decreasing much more gradually than in other engines. governing is effected by regulation of the amount of oil admitted into the cylinder. in spite of its high compression this engine runs with very little vibration. the writer saw a penny stand unmoved on its edge on the top of a cylinder in which the piston was reciprocating 500 times a minute! engines worked by producer-gas these engines are worked by a special gas generated in an apparatus called a "producer." if air is forced through incandescent carbon in a closed furnace its oxygen unites with the carbon and forms carbonic acid gas, known chemically as co_{2}, because every molecule of the gas contains one atom of carbon and two of oxygen. this gas, being the product of combustion, cannot burn (_i.e._ combine with more oxygen), but as it passes up through the glowing coke, coal, or other fuel, it absorbs another carbon atom into every molecule, and we have c_{2}o_{2}, or 2 co, which we know as _carbon monoxide_. this gas may be seen burning on the top of an open fire with a very pale blue flame, as it once more combines with oxygen to form carbonic acid gas. the carbon monoxide is valuable as a heating agent, and when mixed with air forms an explosive mixture. if along with the air sent into our furnace there goes a proportion of steam, further chemical action results. the oxygen of the steam combines with carbon to form carbon monoxide, and sets free the hydrogen. the latter gas, when it combines with oxygen in combustion, causes intense heat; so that if from the furnace we can draw off carbon monoxide and hydrogen, we shall be able to get a mixture which during combustion will set up great heat in the cylinder of an engine. in 1878 mr. emerson dowson invented an apparatus for manufacturing a gas suitable for power plant, the gas being known as producer or poor gas, the last term referring to its poorness in hydrogen as compared with coal and other gases. while the hydrogen is a desirable ingredient in an explosive charge, it must not form a large proportion, since under compression it renders the mixture in which it takes part dangerously combustible, and liable to spontaneous ignition before the piston has finished the compression stroke. water-gas, very rich in hydrogen, and made by a very similar process, is therefore not suitable for internal combustion engines. there are many types of producers, but they fall under two main heads, _i.e._ the _pressure_ and the _suction_. the _pressure_ producer contains the following essential parts:-the _generator_, a vertical furnace fed from the top through an air-tight trap, and shut off below from the outside atmosphere by having its foot immersed in water. any fuel or ashes which fall through the bars into the water can be abstracted without spoiling the draught. air and steam are forced into the generator, and pass up through the fuel with the chemical results already described. the gases then flow into a _cooler_, enclosed in a water-jacket, through which water circulates, and on into a _scrubber_, where they must find their way upwards through coke kept dripping with water from overhead jets. the water collects impurities of all sorts, and the gas is then ready for storage in the gas-holders or for immediate use in the engines. a pound of anthracite coal thus burnt will yield enough gas to develop 1 h.p. for one hour. _suction gas plants._--with these gas is not stored in larger quantities than are needed for the immediate work of the engine. in fact, the engine itself during its suction strokes _draws_ air and steam through a very small furnace, coolers, and scrubbers direct into the cylinder. the furnace is therefore fed with air and water, not by pressure from outside, but by suction from inside, hence the name "suction producer." at the present time suction gas engines are being built for use on ships, since a pound of fuel thus consumed will drive a vessel further than if burnt under a steam boiler. very possibly the big ocean liners of twenty years hence may be fitted with such engines in the place of the triple and quadruple expansion steam machinery now doing the work. blast-furnace gas engines every iron blast-furnace is very similar in construction and action to the generator of a producer-gas plant. into it are fed through a hopper, situated in the top, layers of ore, coal or coke, and limestone. at the bottom enters a blast of air heated by passing through a stove of firebrick raised to a high temperature by the carbon monoxide gas coming off from the furnace. when the stove has been well heated the gas supply is shut off from it and switched to the engine-house to create power for driving the huge blowers. the gas contains practically no hydrogen, as the air sent through the furnace is dry; but since it will stand high compression, it is very suitable for use in large engines. formerly all the gas from the furnace was expelled into the open air and absolutely wasted; then it was utilised to heat the forced draught to the furnace; next, to burn under boilers; and last of all, at the suggestion of mr. b. h. thwaite, to operate internal combustion engines for blowing purposes. thus, in the fitness of things, we now see the biggest gas engines in the world installed where gas is created in the largest quantities, and an interesting cycle of actions results. the engine pumps the air; the air blows the furnace and melts the iron out of the ore; the furnace creates the gas; the gas heats the air or works the engines to pump more air. so engines and furnace mutually help each other, instead of all the obligation being on the one side. when, a few years ago, the method was first introduced, engines were damaged by the presence of dust carried with the gas from the furnace. mr. b. h. thwaite has, however, perfected means for the separation of injurious matter, and blast-furnace gas is coming into general use in england and on the continent. some idea of the power which has been going to waste in ironworks for decades past may be gathered from a report of professor hubert after experiments made in 1900. he says that engines of large size do not use more than 100 cubic feet of average blast-furnace gas per effective horse-power-hour, which is less than one-fourth of the consumption of gas required to develop the same power from boilers and good modern condensing steam-engines, so that there is an immense surplus of power to be obtained from a blast-furnace if the blowing engines are worked by the gas it generates, a surplus which can be still further increased if the gas is properly cleaned. it is estimated that for every 100 tons of coke used in an ordinary cleveland blast-furnace, after making ample allowance for gas for the stoves and power for the lifts, pumps, etc., and for gas for working the necessary blowing engines, there is a surplus of at least _1,500 h.p._; so that by economising gas by cleaning, and developing the necessary power by gas engines, every furnace owner would have a very large surplus of power for his steel or other works, or for selling in the form of electricity or otherwise. yet all this gas had been formerly turned loose for the breezes to warm their fingers at! truly, as an observant writer has recorded, the sight of a special plant being put up near a blast furnace to manufacture gas for the blowing engines suggests the pumping of water uphill in order to get water-power! messrs. westgarth and richardson, of middlesbrough; the john cockerill company, of seraing, belgium; and the de la vergne company, of new york, are among the chief makers of the largest gas engines in the world, ranging up to 3,750 h.p. each. these immense machines, some with fly-wheels 30 feet in diameter, and cylinders spacious enough for a man to stand erect in, work blowers for furnaces or drive dynamos. at the works of the manufacturers mentioned the engines helped to make the steel, and turn the machinery for the creation of brother monsters. [illustration: gigantic gas engines five of sixteen 2,000 h.p. kã¶rting gas engines built by the de la vergne company of new york city for blowing the blast furnaces of the lackawanna steel company. the gas-engine plant at these works is the largest in the world. notice the man to the left.] this use of a "bye-product" of industry is remarkable, but it can be paralleled. furnace slag, once cast away as useless, is now recognised to be a valuable manure, or is converted into bricks, tiles, cement, and other building materials. again, the former waste from the coal-gas purifier assumes importance as the origin of aniline dyes, creosote, saccharine, ammonia, and oils. we really appear to be within sight of the happy time when waste will be unknown. and it therefore is curious that we still burn gas as an illuminant, when the same, if made to work an engine, would give more lighting power in the shape of electric current supplying incandescent lamps. footnote: [11] the fact that air is heated to combustion point by compression has long been known to the chinese. in _the river of golden sand_, captain gill writes: "the natives have an apparatus by which they strike a light by compressed air. the apparatus consists of a wooden cylinder 2-1/2 inches long by 3/4 inch in diameter. this is closed at one end; the bore being about the size of a stout quill pen, an air-tight piston fits into this with a large flat knob at the top. the other end of the piston is slightly hollowed out, and a very small piece of tinder is placed on the top thus formed. the cylinder is held in one hand, the piston inserted and pushed about half-way down; a very sharp blow is then delivered with the palm of the hand on to the top of the knob; the hand must at the same time close on the knob, and instantly withdraw the piston, when the tinder will be found alight. the compression of the air produces heat enough to light the tinder; but this will go out again unless the piston is withdrawn very sharply. i tried a great many times, but covered myself with confusion in fruitless efforts to get a light, for the natives never miss it." chapter vii motor-cars the motor omnibus--railway motor-cars the development of the motor-car has been phenomenal. early in 1896 the only mechanically moved vehicles to be seen on our roads were the traction-engine, preceded by a man bearing a red flag, the steam-roller, and, in the towns, a few trams. to-day the motor is apparent everywhere, dodging through street traffic, or raising the dust of the country roads and lanes, or lumbering along with its load of merchandise at a steady gait. as a purely speed machine the motor-car has practically reached its limit. with 100 h.p. or more crowded into a vehicle scaling only a ton, the record rate of travel has approached two miles in a minute on specially prepared and peculiarly suitable tracks. even up steep hills such a monster will career at nearly eighty miles an hour. next to the racing car comes the touring car, engined to give sixty miles an hour on the level in the more powerful types, or a much lower speed in the car intended for quieter travel, and for people who are not prepared to face a big bill for upkeep. the luxury of the age has invaded the design of automobiles till the gorgeously decorated and comfortably furnished pullman of the railway has found a counterpart in the motor caravan with its accommodation for sleeping and feeding. while the town dweller rolls along in electric landaulet, screened from wind and weather, the tourist may explore the roads of the world well housed and lolling at ease behind the windows of his 2,000-guinea machine, on which the engineer and carriage builder have lavished their utmost skill. the taunt of unreliability once levelled--and with justice--at the motor-car, is fast losing its force, owing to the vast improvements in design and details which manufacturers have been stimulated to make. the motor-car industry has a great future before it, and the prizes therein are such as to tempt both inventor and engineer. every week scores of patents are granted for devices which aim at the perfection of some part of a car, its tyres, its wheels, or its engines. until standard types for all grades of motor vehicles have been established, this restless flow of ideas will continue. its volume is the most striking proof of the vitality of the industry. the uses to which the motor vehicle has been put are legion. on railways the motor carriage is catering for local traffic. on the roads the motor omnibus is steadily increasing its numbers. tradesmen of all sorts, and persons concerned with the distribution of commodities, find that the petrolor steam-moved car or lorry has very decided advantages over horse traction. our postal authorities have adopted the motor mail van. the war office looks to the motor to solve some of its transportation difficulties. in short, the "motor age" has arrived, which will, relatively to the "railway age," play much the same part as that epoch did to the "horse age." at the ultimate effects of the change we can only guess; but we see already, in the great acceleration of travel wherever the motor is employed, that many social institutions are about to be revolutionised. but for the determined opposition in the 'thirties of last century to the steam omnibus we should doubtless live to-day in a very different manner. our population would be scattered more broadcast over the country instead of being herded in huge towns. many railways would have remained unbuilt, but our roads would be kept in much better condition, special tracks having been built for the rapid travel of the motor. we have only to look to a country now in course of development to see that the road, which leads everywhere, will, in combination with the motor vehicle, eventually supplant, or at any rate render unnecessary, the costly network of railways which must be a network of very fine mesh to meet the needs of a civilised community. in the scope of a few pages it is impossible to cover even a tithe of the field occupied by the ubiquitous motor-car, and we must, therefore, restrict ourselves to a glance at the manufacture of its mechanism, and a few short excursions into those developments which promise most to alter our modes of life. we will begin with a trip over one of the largest motor factories in the world, selecting that of messrs. dion and bouton, whose names are inseparable from the history of the modern motor-car. they may justly claim that to deal with the origin, rise, and progress of the huge business which they have built up would be to give an account, in its general lines, of all the phases through which the motor, especially the petrol motor, has passed from its crudest shape to its present state of comparative perfection. the count albert de dion was, in his earlier days, little concerned with things mechanical. he turned rather to the fashionable pursuit of duelling, in which he seems to have made a name. but he was not the man to waste his life in such inanities, and when, one day, he was walking down the paris boulevards, his attention was riveted by a little clockwork carriage exposed for sale among other new year's gifts. that moment was fraught with great consequences, for an inventive mind had found a proper scope for its energy. why, thought he, could not real cars be made to run by some better form of motive power? on inquiring he learnt that a workman named bouton had produced the car. the count, therefore, sought the artisan; with whom he worked out the problem which had now become his aim in life. hence it is that the names "dion--bouton" are found on thousands of engines all over the world. the partners scored their first successes with steamand petrol-driven tricycles, built in a small workshop in the avenue malakoff in paris. the works were then transferred to puteaux, which has since developed into the great automobile centre of the world, and after two more changes found a resting-place on the quai national. here close upon 3,000 hands are engaged in supplying the world's requirements in motors and cars. let us enter the huge block of buildings and watch them at work. the drawing-office is the brain of the factory. within its walls new ideas are being put into practical shape by skilled draughtsmen. the drawings are sent to the model-making shop, where the parts are first fashioned in wood. the shop contains dozens of big benches, circular saws, and planing machines, one of them in the form of a revolving drum carrying a number of planes, which turns thousands of times a minute, and shapes off the rough surface of the blocks of hard wood as if it were so much clay. these blocks are cut, planed, and turned, and then put into the hands of a remarkably skilled class of workmen, who, with rule, calliper, and chisel, shape out cylinders and other parts to the drawings before them with wonderful patience and exactness. after the model has been fashioned, the next step is to make a clay mould from the same, with a hole in the top through which the molten metal is poured. the foundry is most picturesque in a lurid, rembrandtesque fashion: "it is black everywhere. the floor, walls, and roof are black, and the foundry hands look like unwashed penitents in sackcloth and ashes. at the end of the building there is a raised brickwork, and when the visitor is able to see in the darkness, he distinguishes a number of raised lids along the top, while here and there are strewn about huge iron ladles like buckets. on the foreman giving the word, a man steps up on the brickwork and removes the lid, when a column of intense white light strikes upwards. it gives one the impression of coming from the bowels of the earth, like a hole opening out in a volcano. the man bestrides the aperture, down which he drops the ladle at the end of a long pole, and then pulling it up again full of a straw-coloured, shining liquid, so close to him that we shudder at the idea of its spilling over his legs and feet, he pours the molten metal into a big ladle, which is seized by two men who pour the liquid into the moulds. the work is more difficult than it looks, for it requires a lot of practice to fill the moulds in such a way as to avoid blow-holes and flaws that prove such a serious item in foundry practice." in the case-hardening department, next door, there are six huge ovens with sliding fronts. therein are set parts which have been forged or machined, and are subjected to a high temperature while covered in charcoal, so that the skin of the metal may absorb carbon at high temperatures and become extremely tough. all shafts, gears, and other moving parts of a car are subjected to this treatment, which permits a considerable reduction in the weight of metal used, and greatly increases its resistance to wear. after being "carbonised," the material is tempered by immersion in water while of a certain heat, judged by the colour of the hot metal. we now pass to the turning-shop, where the cylinders are bored out by a grinding disc rapidly rotating on an eccentric shaft, which is gradually advanced through the cylinder as it revolves. the utmost accuracy, to the 1/10,000 part of an inch, is necessary in this operation, since the bore must be perfectly cylindrical, and also of a standard size, so that any standard piston may exactly fit it. after being bored, or rather ground, the walls of the cylinder are highly polished, and the article is ready for testing. the workman entrusted with this task hermetically closes the ends by inserting the cylinder between the plates of an hydraulic press, and pumps in water to a required pressure. if there be the slightest crack, crevice, or hole, the water finds its way through, and the piece is condemned to the rubbish heap. in the "motor-room" are scores of cylinders, crank-cases, and gears ready for finishing. here the outside of bored cylinders is touched up by files to remove any marks and rough projections left by the moulds. the crank-cases of aluminium are taken in hand by men who chisel the edges where the two halves fit, chipping off the metal with wonderful skill and precision. the edges are then ground smooth, and after the halves have been accurately fitted, the holes for the bolts connecting them are drilled in a special machine, which presents a drill to each hole in succession. having seen the various operations which a cylinder has to go through, we pass into another shop given up to long lines of benches where various motor parts are being completed. each piece, however small, is treated as of the utmost importance, since the failure of even a tiny pin may bring the largest car to a standstill. we see a man testing pump discs against a standard template to prove their absolute accuracy. close by, another man is finishing a fly-wheel, chipping off specks of metal to make the balance true. we now understand that machine tools cannot utterly displace the human hand and eye. the fitters, with touches of the file, remove matter in such minute quantities that its removal might seem of no consequence. but "matter in the wrong place" is the cause of many breakdowns. we should naturally expect that engines cast from the same pattern, handled by the same machines, finished by the same men, would give identical results. but as two bicycles of similar make will run differently, so do engines of one type develop peculiarities. the motors are therefore taken into a testing-room and bolted to two rows of benches, forty at a time. here they run under power for long periods, creating a deafening uproar, until all parts work "sweetly." the power of the engines is tested by harnessing them to dynamos and noting the amount of current developed at a certain speed. we might linger in the departments where accumulators, sparking plugs, and other parts of the electrical apparatus of a car are made, or in the laboratory where chemists pry into the results of a new alloy, aided by powerful microscopes and marvellously delicate scales. but we will stop only to note the powerful machine which is stretching and crushing metal to ascertain its toughness. no care in experimenting is spared. the chemist, poring over his test tubes, plays as important a part in the construction of a car as the foundry man or the turner. the machine-shop is an object-lesson among the tools noticed in previous chapters of this book. "here is a huge planing machine travelling to and fro over a copper bar. a crank shaft has been cut out of solid steel by boring holes close together through a thick plate, and the two sides of the plate have been broken off, leaving the rough shaft with its edges composed of a considerable number of semicircles. the shaft is slowly rotated on a lathe, and tiny clouds of smoke arise as the tool nicks off pieces of metal to reduce the shaft to a circular shape. other machines, with high-speed tool steel, are finishing gear shafts. fly-wheels are being turned and worm shafts cut. all these laborious operations are carried out by the machines, each under the control of one man whose mind is intent upon the work, ready to stop the machine or adjust the material as may be required. as a contrast to the heavy machines we will pass to the light automatic tools which are grouped in a gallery.... the eye is bewildered by the moving mass, but the whirling of the pulley shafts and the clicking of the capstan lathes is soothing to the ear, while the mind is greatly impressed by the ingenuity of man in suppressing labour by means of machines, of which half a dozen can be easily looked after by one hand, who has nothing to do but to see that they are fed with material. a rod of steel is put into the machine, and the turret, with half a dozen different tools, presents first one and then the other to the end of the rod bathed in thick oil, so that it is rapidly turned, bored, and shaped into caps, nuts, bolts, and the scores of other little accessories required in fitting up a motor-car. on seeing how all this work is done mechanically and methodically, with scarcely any other expense but the capital required in the upkeep of the machines and in driving them, one wonders how the automobile industry could be carried on without this labour-saving mechanism. in any event, if all these little pieces had to be turned out by hand, it is certain that the cost of the motor-car would be considerably more than it is, even if it did not reach to such a figure as to make it prohibitive to all but wealthy buyers. down one side of the gallery the machines are engaged in cutting gears with so much precision that, when tested by turning them together on pins on a bench at the end of the gallery, it is very rare indeed that any one of them is found defective. this installation of automatic tools is one of the largest of its kind in a motor-car works, if not in any engineering shop, and each one has been carefully selected in view of its efficiency for particular classes of work, so that we see machines from america, england, france, and germany." in the fitting-shops the multitude of parts are assembled to form the _chassis_ or mechanical carriage of the car, to which, in a separate shop, is added the body for the accommodation of passengers. the whole is painted and carefully varnished after it has been out on the road for trials to discover any weak spot in its anatomy. then the car is ready for sale. when one considers the racketing that a high-powered car has to stand, and the high speed of its moving parts, one can understand why those parts must be made so carefully and precisely, and also how this care must conduce to the expense of the finished article. it has been said that it is easy to make a good watch, but difficult to make a good motor; for though they both require an equal amount of exactitude and skill, the latter has to stand much more wear in proportion. when you look at a first-grade car bearing a great maker's name, you have under your eyes one of the most wonderful pieces of mechanism the world can show. we will not leave the de dion-bouton works without a further glance at the human element. the company never have a slack time, and consequently can employ the same number of people all the year round. they pride themselves on the fact that the great majority of the men have been in their employ for several years, with the result that they have around them a class of workmen who are steady, reliable and, above all, skilful in the particular work they are engaged upon. there are more than 2,600 men and about 100 women, these latter being employed chiefly in the manufacture of sparking plugs and in other departments where there is no night work. they are mostly the wives or widows of old workmen, and in thus finding employment for them the firm provides for those who would otherwise be left without resource, and at the same time earns the gratitude of their employã©s. note.--the author gratefully acknowledges the help given by messrs. de dion-bouton, ltd., in providing materials for this account of their works. the motor omnibus prior to the emancipation of the road automobile in 1896, permission had been granted to corporations to run trams driven by mechanical power through towns. the steam tram, its engine protected by a case which hid the machinery from the view of restive horses, panted up and down our streets, drawing one or more vehicles behind it. the electric tram presently came over from america and soon established its superiority to the steamer with respect to speed, freedom from smell and smoke, and noiselessness: the system generally adopted was that invented in 1887 by frank j. sprague, in which an overhead cable supported on posts or slung from wires spanning the track carries current to a trolley arm projecting from the vehicle. the return current passes through the rails, which are made electrically continuous by having their individual lengths either welded together or joined by metal strips. in america, where wide streets and rapidly growing cities are the rule, the electric tramway serves very useful ends; the best proof of its utility being the total mileage of the tracks. statistics for 1902 show that since 1890 the mileage had increased from 1,261 to 21,920 miles; and the number of passengers carried from 2,023,010,202 to 4,813,466,001, or an increase of 137â·94 per cent. it is interesting to note that electricity has in the united states almost completely ousted steam and animal traction so far as street cars are concerned; since the 5,661 miles once served by animal power have dwindled to 259, and steam can claim only 169 miles of track. next to the united states comes germany as a user of electricity for tractive purposes; though she is a very bad second with only about 6,000 miles of track; and england takes third place with about 3,000 miles. that the british isles, so well provided with railways, should be so poorly equipped with tramways is comprehensible when we consider the narrowness of the streets of her largest towns, where a good service of public vehicles is most needed. the installation of a tram-line necessitates the tearing up of a street, and in many cases the closing of that street to traffic. we can hardly imagine the dislocation of business that would result from such a blockage of, say, the strand and high holborn; but since it has been calculated that no less than five millions of pounds sterling are lost to our great metropolis yearly by the obstructions of gas, water, telegraph, and telephone operations, which only partially close a thoroughfare, or by the relaying of the road surface, which is not a very lengthy matter if properly conducted, we might reckon the financial loss resulting from the laying of tram-rails at many millions. even were they laid, the trouble would not cease, for a tram is confined to its track, and cannot make way for other traffic. this inadaptability has been the cause of the great outcry lately raised against the way in which tram-line companies have monopolised the main streets and approaches to many of our largest towns. while the electric tram is beneficial to a large class of people, as a cheap method of locomotion between home and business, it sadly handicaps all owners of vehicles vexatiously delayed by the tram. at brentford, to take a notorious example, the double tram-line so completely fills the high street that it is at places impossible for a cart or carriage to remain at the kerbstone. another charge levelled with justice at the tram-line is that the rails and their setting are dangerous to cyclists, motorists, and even heavy vehicles, especially in wet weather, when the "side-slip" demon becomes a real terror. english municipalities are therefore faced by a serious problem. improved locomotion is necessary; how can it best be provided? by smooth-running, luxurious, well-lighted electric trams, travelling over a track laid at great expense, and a continual nuisance to a large section of the community; or by vehicles independent of a central source of power, and free to move in any direction according to the needs of the traffic? where tramways exist, those responsible for laying them at the rate of several thousand pounds per mile are naturally reluctant to abandon them. but where the fixed track has not yet arrived an alternative method of transport is open, viz. the automobile omnibus. quite recently we have seen in london and other towns a great increase in the number of motor buses, which often ply far out into the country. from the point of speed they are very superior to the horsed vehicle, and statistics show that they are also less costly to run in proportion to the fares carried, while passengers will unanimously acknowledge their greater comfort. to change from the ancient, rattling two-horse conveyance, which jolts us on rough roads, and occasionally sends a thrill up the spine when the brakes are applied, to the roomy steamor petrol-driven bus, which overtakes and threads its way through the slower traffic, is a pleasant experience. so the motor buses are crowded, while the horsed rivals on the same route trundle along half empty. since the one class of vehicles can travel at an average pace of ten miles an hour, as against the four miles an hour of the other, no wonder that this should be so. even if the running costs of a motor bus for a given distance exceed that of an electric tram, we must remember that, whereas a bus runs on already existing roads, an immense amount of capital must be sunk in laying the track for the tram, and the interest on this sum has to be added to the total running costs. the next decade will probably decide whether automobiles or trams are to serve the needs of the community in districts where at present no efficient service of any kind exists. in london motor buses are being placed on the roads by scores, and the day cannot be far distant when the horse will disappear from the bus as it is already fast vanishing from the front of the tram. both petrol and steam, and in some cases a combination of petrol and electricity, are used to propel the motor bus. it has not yet been decided which form of power yields the best results. petrol is probably the cheaper fuel, but steam gives the quieter running; and could electric storage batteries be made sufficiently light and durable they would have a strong claim to precedence. there has lately appeared a new form of accumulator--the von rothmund--which promises well, since weight for weight it far exceeds in capacity any other type, and is so constructed that it will stand a lot of rough usage. a car fitted with a von rothmund battery scaling about 1,500 lbs. has run 200 miles on one charge, and it is anticipated that with improvements in motors a 1,100-lb. battery will readily be run 150 miles as against the 50 miles in the case of a lead battery of equal weight. there is a large sphere open to the motor bus outside districts where the electric tram would enter into serious competition with it. we have before us a sketch-map of the great western railway, one of the most enterprising systems with regard to its use of motors to feed its rails. no less than thirty road services are in operation, and their number is being steadily augmented. in fact, it looks as if in the near future the motor service will largely supplant the branch railway, blessed with very few trains a day. a motor bus service plying every half-hour between a town and the nearest important main-line station would be more valuable to the inhabitants than half a dozen trains a day, especially if the passenger vehicles were supplemented by lorries for the carriage of luggage and heavy goods. in this connection we may notice an invention of m. renard--a motor train of several vehicles towed by a single engine. we have all seen the traction-engine puffing along with its tail of trucks, and been impressed by the weight of the locomotive, and also by the manner in which the train occupies a road when passing a corner. the weight is necessary to give sufficient grip to move the whole train, while the spreading of the vehicles across the thoroughfare on a curve arises from the fact that each vehicle does not follow the path of that preceding it, but describes part of a smaller circle. m. renard has, in his motor train, evaded the need for a heavy tractor by providing _every_ vehicle with a pair of driving wheels, and transmitting the power to those wheels by a special flexible propeller shaft which passes from the powerful motor on the leading vehicle under all the other vehicles, engaging in succession with mechanism attached to all the driving axles. in this manner each car yields its quotum of adhesion for its own propulsion, and the necessity for great weight is obviated. special couplings ensure that the path taken by the tractor shall be faithfully followed by all its followers. a motor train of this description has travelled from paris to berlin and drawn to itself a great deal of attention. "will it," asks a writer in _the world's work_, "ultimately displace the conventional traction-engine and its heavy trailing waggons? every municipality and county council is only too painfully cognisant of the dire effects upon the roads exercised by the cumbrous wheels of these unwieldy locomotives and trains. with the renard train, however, the trailing coaches can be of light construction, carried on ordinary wheels which do not cut up or otherwise damage the roadway surface. many other advantages inherent in such a train might be enumerated. the most important, however, are the flexibility of the whole train; its complete control; faster speed without any attendant danger; its remarkable braking arrangements as afforded by the continuous propeller shaft gearing directly with the driving-wheels of each carriage; its low cost of maintenance, serviceability, and instant use; and the reduction in the number of men requisite for the attention of the train while on a journey." were the system a success, it would find plenty of scope to convey passengers and commodities through districts too sparsely populated to render a railway profitable. people would talk about travelling or sending goods by the "ten-thirty motor train," just as now we speak of the "eleven-fifteen to town." as a carrier and distributer of mails, the motor van has already established a position. to quote but a couple of instances, there are the services between london and brighton, and liverpool and manchester. in the isle of wight motor omnibuses connect all the principal towns and villages. each bus is a travelling post-office in which, by an arrangement with the postmaster-general, anybody may post letters at the recognised stopping-places or whenever the vehicle has halted for any purpose. in paris, london, berlin, the motor mail van is a common sight. it has even penetrated the interior of india, where the maharajah of gwalior uses a specially fitted steam car for the delivery of his private mails. and, as though to show that man alone shall not profit by the new mode of locomotion, paris owns a motor-car which conveys lost dogs from the different police-stations to the dogs' home! in fact, there seems to be no purpose to which a horse-drawn vehicle can be put, which either has not been, or shortly will be, invaded by the motor. railway motor-cars in the early days of railway construction vehicles were used which combined a steam locomotive with an ordinary passenger carriage. after being abandoned for many years, the "steam carriage" was revived, in 1902, by the london and south western and great western railways for local service and the handling of passenger traffic on branch lines. since that year rail motor-cars have multiplied; some being run by steam, others by petrol engines, and others, again, by electricity generated by petrol engines. the first class we need not describe in any detail, as it presents no features of peculiar interest. the north eastern has had in use two rail-motors, each fifty-two feet long, with a compartment at each end for the driver, and a central saloon to carry fifty-two passengers. an 80 h.p. four-cylindered wolseley petrol motor drives a westinghouse electric generator, which sends current into a couple of 55 h.p. electric motors geared to the running-wheels. an air compressor fitted to the rear bogie supplies the westinghouse air brakes, while in addition a powerful electric brake is fitted, acting on the rails as well as the wheels. the coach scales thirty-five tons. the chief advantage of this "composite" system of power transmission is that the engine is kept running at a constant speed, while the power it develops at the electric motors is regulated by switches which control the action of the armature and field magnets. when heavy work must be done the engine is supplied with more gaseous mixture, and the generators are so operated as to develop full power. in this manner all the variable speed gears and clutches necessary when the petrol motor is connected to the driving-wheels are done away with. the latter system gives, however, greater economy of fuel, and the great northern railway has adopted it in preference to the petrol-electric. this railway has many small branch lines running through thinly populated districts, which, though important as feeders of the main tracks, are often worked at a loss. a satisfactory type of automobile carriage would not only avoid this loss, but also largely prevent the competition of road motors. the car should be powerful enough to draw an extra van or two on occasion, since horses and heavy luggage may sometimes accompany the passengers. messrs. dick, kerr, and company have built a car, which, when loaded with its complement of passengers, weighs about sixteen tons. the motive power is supplied by two four-cylinder petrol engines of the daimler type, each giving 36 h.p. these are suspended on a special frame, independent of that which carries the coach body, so that the passengers are not troubled by the vibration of the engines, even when the vehicle is at rest. the great feature of the car is the lightness of the machinery--only two tons in weight--though it develops sufficient power to move the carriage at fifty miles per hour. after travelling 2,000 miles the machinery showed no appreciable signs of wear; so that the company considers that it has found a reliable type of motor for the working of the short line between hatfield and hertford. since one man can drive a petrol car, while two--a driver and a stoker--are necessary on a steam car, a considerable reduction in wages will result from the employment of these vehicles. engineers find motor-trolleys very convenient for inspecting the lines under their care. on the london and south western railway a trolley driven by a 6-8 h.p. engine, and provided with a change-gear giving six, fifteen, and thirty miles per hour in either direction, is at work. it seats four persons. in the colonies, notably in south africa, where coal and wood fuel is scarce or expensive, the motor-trolley, capable of carrying petrol for 300 miles' travel, is rapidly gaining ground among railway inspectors. makers are turning their attention to petrol shunting engines, useful in goods yards, mines, sewerage works. firms such as messrs. maudslay and company, of coventry; the wolseley tool and motor car company; messrs. panhard and levassor; messrs. kerr, stuart, and company have brought out locomotives of this kind which will draw loads up to sixty tons. the fact that a petrol engine is ready for work at a moment's notice, and when idle is not "eating its head off," and has no furnace or boiler to require attention, is very much in its favour where comparatively light loads have to be hauled. chapter viii the motor afloat pleasure boats--motor lifeboats--motor fishing boats--a motor fire float--the mechanism of the motor boat--the two-stroke motor--motor boats for the navy having made such conquests on land, and rendered possible aerial feats which could scarcely have been performed by steam, the explosion motor further vindicates its versatility by its fine exploits in the water. at the paris exhibition of 1889 gottlieb daimler, the inventor who made the petrol engine commercially valuable as an aid to locomotion, showed a small gas-driven boat, which by most visitors to the exhibition was mistaken for an ordinary steam launch, and attracted little interest. not deterred by this want of appreciation, mr. daimler continued to perfect the idea for which, with a prophet's eye, he saw great possibilities; and soon motor launches became a fairly common sight on german rivers. they were received with some enthusiasm in the united states, as being particularly suitable for the inland lakes and waterways with which that country is so abundantly blessed; but met with small recognition from the english, who might reasonably have been expected to take great interest in any new nautical invention. now, however, english manufacturers have awaked fully to their error; and on all sides we see boats built by firms competing for the lead in an industry which in a few years' time may reach colossal proportions. [illustration: a modern car and boat in the background is the racing motor boat "napier ii.", which on a trial trip travelled over the "measured mile" at 30â·93 miles per hour. in the foreground is a "napier" racing car, which has attained a speed of 104â·8 miles per hour.] until quite recently the marine motor was a small affair, developing only a few horse-power. but because the gas-engine for automobile work had been so vastly improved in the last decade, it attracted notice as a rival to steam for driving launches and pleasure boats, and soon asserted itself as a reliable mover of vessels of considerable size. to promote the development of the industry, to test the endurance of the machine, and to show the weak spots of mechanical design, trials and races were organised on much the same lines as those which have kept the motor-car so prominently before the public--races in the solent, across the channel, and across the mediterranean. the speed, as in the case of cars, has risen very rapidly with the motor boat. when, in february, 1905, a napier racer did some trial spins over the measured mile in the thames at long reach, she attained 28â·57 miles per hour on the first run. on turning, the tide was favourable, and the figures rose to 30â·93 m.p.h., while the third improved on this by over a mile. her mean speed was 29â·925 m.p.h., or about 2/3 m.p.h. better than the previous record--standing to the credit of the american _challenger_. the latter had, however, the still waters of a lake for her venue, so that the napier's performance was actually even more creditable than the mere figures would seem to imply. at a luncheon which concluded the trial, mr. yarrow, who had built the steel hull, said: "to give an idea of what an advance the adoption of the internal combustion engine really represents, i should like to state that, if we were asked to guarantee the best speed we could with a boat of the size of napier ii., fitted with the latest form of steam machinery of as reliable a character as the internal combustion engine in the present boat, we should not like to name more than sixteen knots. so that it may be taken that the adoption of the internal combustion engine, in place of the steam-engine, for a vessel of this size, really represents an additional speed of ten knots an hour. i should here point out that the speed of a vessel increases rapidly with its size. for example: in what is termed a second-class torpedo boat, sixty feet in length, the best speed we could obtain would be twenty knots; but for a vessel of, say, 200 feet in length, with similar but proportionately larger machinery, a speed of thirty knots could be obtained. therefore, the obtaining of a speed of practically twenty-six knots in the yarrow-napier boat, only forty feet in length, points to the possibility, in the not far-distant future, of propelling a vessel 220 feet in length at even forty-five knots per hour. all that remains to be done is to perfect the internal combustion engine, so as to enable large sizes to be successfully made." boats of 300 h.p. and upwards are being built; and the project has been mooted of holding a transatlantic race, open to motor boats of all sizes, which should be quite self-contained and able to carry sufficient fuel to make the passage without taking in fresh supplies. in view of the perils that would be risked by all but large craft, and in consideration of the prejudice that motor boats might incur in event of any fatalities, the automobile club of france set its face against the venture, and it fell through. it is possible, however, that the scheme may be revived as soon as larger motor boats are afloat, since the atlantic has actually been crossed by a craft of 12 h.p., measuring only forty feet at the water-line. this happened in 1902, when captain newman and his son, a boy twelve years old, started from new york, and made falmouth harbour after thirty days of anxious travel over the uncertain and sometimes tempestuous ocean. the boat, named the _abiel abbot low_, carried auxiliary sails of small size, and was not by any means built for such a voyage. the engine--a two-cylinder--burned kerosene. captain newman received â£1,000 from the new york kerosene oil engine company for his feat. the money was well earned. though provided with proper navigating instruments--which he knew how to use well--newman had a hard time of it to keep his craft afloat, his watches sometimes lasting two days on end when the weather was bad. yet the brave pair won through; and probably even more welcome than the sense of success achieved and the reward gained was the long two-days' sleep which they were able to get on reaching falmouth harbour. pleasure boats we may now consider the pleasure and commercial uses of the motor boat and marine motor. as a means of recreation a small dinghy driven by a low-powered engine offers great possibilities. its cost is low, its upkeep small, and its handiness very great. already a number of such craft are furrowing the surface of the thames, seine, rhine, and many other rivers in europe and america. while racing craft are for the wealthy alone, many individuals of the class known as "the man of moderate means" do not mind putting down â£70 to â£100 for a neat boat, the maintenance of which is not nearly so serious a matter as that of a small car. tyre troubles have no counterpart afloat. the marine motor dispenses with change gears. water being a much more yielding medium than mother earth, the shocks of starting and stopping are not such as to strain machinery. then again, the cooling of the cylinders is a simple matter with an unlimited amount of water almost washing the engine. and as the surface of water does not run uphill, a small motor will show to better advantage on a river than on a road. thus, a 5 h.p. car will not conveniently carry more than two people if it is expected to climb slopes at more than a crawl. affix a motor of equal power to a boat which accommodates half a dozen persons, and it will move them all along at a smart pace as compared with the rate of travel given by oars. after all, on a river one does not want to travel fast--rather to avoid the hard labour which rowing undoubtedly does become with a craft roomy enough to be comfortable for a party. the marine motor also scores under the heading of adaptability. a wagonette could not be converted into a motor-car with any success. but a good-sized row-boat may easily blossom out as a useful self-propelled boat. you may buy complete apparatus--motor, tanks, screw, batteries, etc.--for clamping direct on to the stern, and there you are--a motor boat while you wait! even more sudden still is the conversion effected by the motogodille, which may be described as a motor screw and rudder in one. the makers are the buchet company, a well-known french firm. "engine and carburetter, petrol tank, coil, accumulator, lubricating oil reservoir, exhaust box, propeller shaft, and propeller with guard are all provided, so that the outfit requires no additional accessories. for mounting in position at the stern of the boat, the complete set is balanced on a standard, and carries a steering arm, on which the tanks are mounted; and also the stern tube and propeller guard, which are in one solid piece, in addition to the engine. in order that no balancing feats shall be required of the person in charge, there is, on the supporting standard, a quadrant, in the notches of which a lever on the engine frame engages, thus allowing the rigid framework, and therefore the propeller shaft, to be maintained at any angle to the vertical without trouble."[12] the 2 h.p. engine drives a boat 16 feet long by 4 feet 6 inches beam at 6-1/2 miles per hour through still water. as the motogodille can be swerved to right or left on its standard, it acts as a very efficient rudder, while its action takes no way off the boat. for people who like an easy life on hot summer days, reclining on soft cushions, and peeping up through the branches which overhang picturesque streams, there is the motor punt, which can move in water so shallow that it would strand even a row-boat. the oxford undergraduate of to-morrow will explore the leafy recesses of the "cher," not with the long pole laboriously raised and pushed aft, but by the power of a snug little motor throbbing gently at the stern. and on the open river we shall see the steam launch replaced by craft having much better accommodation for passengers, while free from the dirt and smells which are inseparable from the use of steam-power. the petrol launch will rival the electric in spaciousness, and the steamer in its speed and power, size for size. some people have an antipathy to this new form of river locomotion on account of the risks which accompany the presence of petrol. were a motor launch to ignite in, say, boulter's lock on a summer sunday, or at the henley regatta, there might indeed be a catastrophe. the same danger has before now been flaunted in the face of the automobilist on land; yet cases of the accidental ignition of cars are very, very rare, and on the water would be more rare still, because the tanks can be more easily examined for leaks. still, it behoves every owner of a launch to keep his eye very widely open for leakage, because any escaping liquid would create a collection of gas in the bottom of the boat, from which it could not escape like the gas forming from drops spilled on the road. [illustration: _photo branger & cie, paris._ the motogodille the motogodille, or motor rudder, consists of a screw propeller fitted to a small buchet motor. the whole apparatus is mounted on a standard in the stern, and the operator, by moving the inboard arm to right or left, can steer the boat as he wishes. a 2-h.p. motor gives a speed of 5 to 6 miles an hour.] the future popularity of the motor boat is assured. the waterside dweller will find it invaluable as a means of carrying him to other parts of the stream. the "longshoreman" will be able to venture much further out to sea than he could while he depended on muscles or wind alone, and with much greater certainty of returning up to time. a whole network of waterways intersects civilised countries--often far better kept than the roads--offering fresh fields for the tourist to conquer. river scenery and beautiful scenery more often than not go together. the car or cycle may be able to follow the course of a stream from source to mouth; yet this is the exception rather than the rule. we shoot _over_ the stream in the train or on our machines; note that it looks picturesque; wonder vaguely whither it flows and whence it comes; and continue our journey, recking little of the charming sights to be seen by anyone who would trust himself to the water. hitherto the great difficulty has been one of locomotion. in a narrow stream sailing is generally out of the question; haulage by man or beast becomes tedious, even if possible; and rowing day after day presupposes a good physical condition. in the motor boat the holiday maker has an ideal craft. it occupies little room; can carry fuel sufficient for long distances; is unwearying; and is economical as regards its running expenses. we ought not to be surprised, therefore, if in a few years the jaded business man turns as naturally to a spin or trip on the rivers and canals of his country as he now turns to his car and a rush over the dusty highway. then will begin another era for the disused canal, the vegetation-choked stream; and our maps will pay more attention to the paths which nature has water-worn in the course of the ages. to the scientific explorer also the motor affords valuable help. many countries, in which roads are practically non-existent, can boast fine rivers fed by innumerable streams. what fields of adventure, sport, and science would be open to the possessor of a fast launch on the amazon, the congo, the mackenzie, or the orinoco, provided only that he could occasionally replenish his fuel tanks! motor lifeboats turning to the more serious side of life, we find the marine motor still much in evidence. on account of its comparatively short existence it is at present only in the experimental stage in many applications, and time must pass before its position is fully established. take, for instance, the motor lifeboat lately built for the royal national lifeboat institution. here are encountered difficulties of a kind very different from those of a racing craft. a lifeboat is most valuable in rough weather, which means more or less water often coming aboard. if the water reached the machinery, troubles with the electrical ignition apparatus would result. so the motor must be enclosed in a water-tight compartment. and if so enclosed it must be specially reliable. also, since a lifeboat sometimes upsets, the machinery needs to be so disposed as not to interfere with her self-righting qualities. the list might easily be extended. an account of the first motor life-saver will interest readers, so we once again have recourse to the chief authority on such topics--the _motor boat_--for particulars. the boat selected for experiment was an old one formerly stationed at folkestone, measuring thirty-eight feet long by eight feet beam, pulling twelve oars, double-banked, and of the usual self-righting type, rigged with jib, fore-lug, and mizzen. after she had been hauled up in mr. guy's yard, where some of the air-cases under the deck amidships were taken out, a strong mahogany case, measuring four feet long by three feet wide and as high as the gunwales, lined with sheet copper so as to be water-tight, with a close-fitting lid which could be easily removed on shore, was fitted in place, and the whole of the vital parts of the machinery, comprising a two-cylinder motor of 10 h.p., together with all the necessary pumps, carburetter, electric equipment, etc., were fitted inside this case. the engine drives a three-bladed propeller through a long shaft with a disconnecting clutch between, so that for starting or stopping temporarily the screw can be disconnected from the engine. the petrol, which serves as fuel for the engine, is carried in a metal tank stored away inside the forward "end" box, where it is beyond any possibility of accidental damage. sufficient fuel for a continuous run of over ten hours is carried. the engine is started by a handle fitted on the fore side of the case, which can be worked by two men. the position and size of the engine-case is such that only two oars are interfered with, but it does not follow that the propelling power of the two displaced men is entirely lost, because they can double bank some of the other oars when necessary. fitted thus, the lifeboat was tested in all sorts of weather during the month of april, and it was found that she could be driven fairly well against a sea by means of the motor alone; but when it was used to assist the sails the true use of the motor as an auxiliary became apparent, and the boat would work to windward in a way previously unattainable. neither the pitching or rolling in a seaway, in any weather then obtainable, interfered at all with the proper working or starting of the motor, which worked steadily and well throughout. having been through these preliminary tests, she was more severely tried. running over the measured mile with full crew and stores on board, she developed over six knots an hour. the men were then replaced by equivalent weights lashed to the thwarts, and she was capsized by a crane four times, her sails set and the sheets made fast, yet she righted herself without difficulty. an interesting feature of the capsize was that the motor stopped automatically when the boat had partly turned over. this arrangement prevents her from running away from the crew if they should be pitched out. the motor started again after a few turns of the handle, so proving that the protecting compartment had kept the water at bay. from this account it is obvious that a valuable aid to life-saving at sea has been found. the steam lifeboat, propelled by a jet of water squirted out by pumps below the water line, is satisfactory so long as the boat keeps upright. but in event of an upset the fires must necessarily be extinguished. no such disability attends the petrol-driven craft, and we shall be glad to think that the brave fellows who risk their lives in the cause of humanity will be spared the intense physical toil which a long row to windward in a heavy sea entails. the general adoption of this new ally will take time, and must depend largely on the liberality of subscribers to the fine institution responsible for lifeboat maintenance; but it is satisfactory to learn that the committee has given the boat in question a practical chance in the open sea by stationing her at newhaven, sussex, as a unit in the lifeboat fleet. motor fishing boats it is a pretty sight to watch a fishing fleet enter the harbour with its catch, taken far away on the waters beyond the horizon while landsmen slept. the sails, some white, some brown, some wondrously patched and bearing the visible marks of many a hard fight with the wind, belly out in graceful lines as the boats slip past the harbour entrance. no wonder that the painter has so often found subjects for his canvas and brushes among the toilers of the deep. but underlying the romance and picturesqueness of the craft there is stern business. those boats may be returning with full cargoes, such as will yield good profits to owner and crew; or, on the other hand, the hold may be empty, and many honest hearts be heavy at the thought of wasted days. a few years ago the yarmouth herring fleet is said to have returned on one occasion with but a single fish to the credit of the whole fleet! this might have been a mere figure of speech; it stands, at any rate, for many thousands of pounds lost by the hardy fishermen. when the boats have been made fast, the fish, if already disentangled from the nets, is usually sold at once by auction, the price depending largely on the individual size and freshness of the "catch." now, with the increase in the number of boats and from other causes, the waters near home have been so well fished over that much longer journeys must be made to the "grounds" than were formerly necessary. trawling, that is, dragging a large bag-net--its mouth kept open by a beam and weights--along the bottom of the sea for flatfish, has long been performed by powerful steam vessels, which may any day be seen leaving or entering hull or grimsby in large numbers. surface fishing, wherein a long drift-net, weighted at its lower edge and buoyed at the upper edge to enable it to keep a perpendicular position, is used for herring and mackerel, and in this industry wind power alone is generally used by british fishermen. the herring-boat sets sail for the grounds in the morning, and at sundown should be at the scene of action. her nets, aggregating, perhaps, a mile in length, are then "shot," and the boat drifts along towing the line behind her. if fish appear, the nets are hauled in soon after daybreak by the aid of a capstan. the labour of bringing a mile of nets aboard is very severe--so severe, in fact, that the larger boats in many cases employ the help of a small steam-engine. during the return voyage the fish is freed from the meshes, and thrown into the hold ready for sale as soon as land is reached. fish, whether for salting or immediate consumption, should be fresh. no class of human food seems to deteriorate so quickly when life is extinct as the "denizens of the deep," so that it is of primary importance to fishermen that their homeward journey should be performed in the shortest possible time. if winds are contrary or absent there may be such delay as to need the liberal use of salt, and even that useful commodity will not stave off a fall in value. it therefore often happens that a really fine catch arrives at its market in a condition which spells heavy loss to the catchers. a slow return also means missing a day's fishing, which may represent â£200 to â£300. for this reason the dogger bank fishing fleet is served by steam tenders, which carry off the catches as they are made, and thus obviate the necessity for a boat's return to port when its hold is full. such a system will not, however, be profitable to boats owned by individuals, and working within a comparatively short distance of land. each boat must depend on its particular powers, the first to return getting rather better prices than those which come "with the crowd." so steam power is in some cases installed as an auxiliary to the sails, though it may entail the outlay of â£2,000 as first cost, and a big bill for upkeep and management. "small" men cannot afford this expense, and they would be doomed to watch their richer brethren slip into the market before them had not the explosion motor come to their aid. this just meets their case; it is not nearly so expensive to install as steam, occupies much less room, is easier to handle, and therefore saves the expense of trained attendants. fishermen are notoriously conservative. to them a change from methods sanctioned by many years of practice is abhorrent. what sufficed for their fathers, they say, should suffice for them. their trade is so uncertain that a bad season would see no return for the cost of the motor, since, where no fish are caught, it makes little difference whether the journey to port be quick or slow. however, the motor is bound to come. it has been applied to fishing boats with marked success. while the nets are out, the motor is stopped, and costs not a penny more till the time comes for hauling in. then it is geared up with a capstan, and saves the crew much of their hardest work. when all is aboard, the capstan hands over the power to the screw, which, together with the sails, propels the vessel homewards at a smart pace. the skipper is certain of making land in good time for the market; and he will be ready for the out voyage next morning. another point in favour of the motor is that, when storms blow up, the fleet will be able to run for shelter even if the wind be adverse; and we should hear less of the sacrifice of life which makes sad reading after every severe gale. as to the machinery to be employed, mr. f. miller, of oulton broad, who first applied the gas-motor to a fishing smack--the _pioneer_--considers that a 12 h.p. engine would suffice as an auxiliary for small craft of the class found in the northern parts of great britain. the norfolk boats would require a 30 h.p.; and a full-powered boat--_i.e._ one that could depend on the motor entirely--should carry a three-cylinder engine of 80 h.p. in any case, the machinery must be enclosed and well protected; while the lubrication arrangements should be such as to be understood easily by unskilled persons, and absolutely reliable. owing to the moisture in the atmosphere the ordinary high-tension coil ignition, such as is used on most motor-cars, would not prove efficient, and it is therefore replaced by a low-tension type which makes and breaks the primary circuit by means of a rocking arm working through the walls of the cylinder. lastly, all parts which require occasional examination or adjustment must be easily accessible, so that they may receive proper attention at sea, and not send the vessel home a "lame duck" under sail. the advantages of the motor are so great that the scotch authorities have taken the matter up seriously, appointing an expert to make inquiries. it is therefore quite possible that before many years have elapsed the motor will play an important part in the task of supplying our breakfast tables with the dainty sole or toothsome herring. a motor fire float as a good instance of this particular adaptation of the explosion engine to fire-extinction work, we may quote the apparatus now in attendance on the huge factory of messrs. huntley and palmer, the famous reading biscuit makers. the factory lies along the banks of the river kennet, which are joined by bridges so close to the water that a steamer could not pass under them. messrs. merryweather accordingly built the motor float, 32 feet long, 9-1/2 feet beam, and drawing 27 inches. two engines, each having four cylinders of a total of 30 h.p., drive two sets of three-cylinder "hatfield" pumps, which give a continuous feed to the hose. engines and pumps are mounted on a single bed-plate, and are worked separately, unless it be found advisable to "siamese" the hoses to feed a single 1-1/2-inch jet, which can be flung to a great height. one of the most interesting features of the float is the method of propulsion. as its movements are limited to a few hundred yards, the fitting of a screw was considered unnecessary, its place being taken by four jets, two at each end, through which water is forced against the outside water by the extinguishing pumps. these will move the float either forward or astern, steer her, or turn her round. so here once again petrol has trodden upon the toes of giant steam: and very effectively, too. the mechanism of the motor boat in many points the marine motor reproduces the machinery built into cars. the valve arrangements, governors, design of cylinders and water-jackets are practically the same. small boats carry one cylinder or perhaps two, just as a small car is content with the same number; but a racing or heavy boat employs four, six, and, in one case at least, twelve cylinders, which abolish all "dead points" and enable the screw to work very slowly without engine vibration, as the drive is continuous. the large marine motor is designed to run at a slower rate than the land motor, and its cylinders are, therefore, of greater size. some of the cylinders exhibited in the automobile show at the london "olympia" seemed enormous when compared with those doing duty on even high-powered cars; being more suggestive of the parts of an electric lighting plant than of a machine which has to be tucked away in a boat. except for the reversing gear, gearing is generally absent on the motor boat. the chauffeur has not to keep changing his speed lever from one notch to another according to the nature of the country. on the sea conditions are more consistently favourable or unfavourable, and, as in a steamboat, speed is controlled by opening or closing the throttle. the screw will always be turned by the machinery, but its effect on the boat must depend on its size and the forces acting in opposition to it. since water is yielding, it does not offer a parallel to the road. should a car meet a hill too steep for its climbing powers, the engines must come to rest. the wheel does not slip on the road, and so long as there is sufficient power it will force the car up the severest incline; as soon as the power proves too small for the task in hand the car "lies down." in a motor boat, however, the engine may keep the screw moving without doing more against wind and tide than prevent the boat from "advancing backwards." the only way to make the boat efficient to meet all possible conditions would be to increase the size or alter the pitch of the screw, and to install more powerful engines. "gearing down"--as in a motor-car--being useless, the only mechanism needed on a motor boat in connection with the transmission of power from cylinders to screw is the reversing gear. though engines have been designed with devices for reversing by means of the cams operating the valves, the reversal of the screw's movement is generally effected through gears on the transmission apparatus. the simplest arrangement, though not the most perfect mechanically, is a reversible screw, the blades of which can be made to feather this way or that by the movement of a lever. sometimes two screws are employed, with opposite twists, the one doing duty while the other revolves idly. but for fast and heavy boats a single solid screw with immovable blades is undoubtedly preferable; its reversal being effected by means of friction clutches. the inelasticity of the explosion motor renders it necessary that the change be made gradually, or the kick of the screw against the motor might cause breakages. the clutch, gradually engaging with a disc revolved by the propeller shaft, first stops the antagonistic motion, and then converts it into similar motion. many devices have been invented to bring this about, but as a description of them would not be interesting, we pass on to a consideration of the fuel used in the motor boat. petrol has the upper hand at present, yet heavier oil must eventually prevail, on account both of its cheapness and of its greater safety. the only objection to its use is the difficulty attending the starting of the engine with kerosene; and this is met by using petrol till the engine and carburetter are hot, and then switching on the petroleum. when once the carburetter has been warmed by exhaust gases to about 270â° fahrenheit it will work as well with the heavy as with the light fuel. since any oil or spirit may leak from its tanks and cause danger, an effort has been made to substitute solid for liquid fuel. the substance selected is naphthalene--well known as a protector of clothes against moths. at the "olympia" automobile exhibition of 1905 the writer saw an engine--the chenier leon--which had been run with balls of this chemical, fed to the carburetter through a melting-pot. for a description of this engine we must once again have recourse to the _motor boat_. the inventors had decided to test its performance with petrol, paraffin, and naphthalene respectively. "the motor, screwed to a testing bench, was connected by the usual belt to a dynamo, so that the power developed under each variety of fuel might be electrically measured, and was then started up on petrol. as soon as the parts were sufficiently warmed up by the exhaust heat, the petrol was turned off, and the motor run for some time on paraffin, until sufficient naphthalene was thoroughly melted to the consistency of a thick syrup. the naphthalene was then fed to its mixing valve through a small pipe dipping into the bottom of the melting-pot, and thence sprayed into the induction chamber to carburate the air therein. hitherto, the motor had given an average of 12 electrical h.p. at 1,000 revolutions per minute, and it was noticed that as soon as the change was made, this was fully maintained. this test, when continued, bore out others which had previously been made by the firm, and showed the consumption of each of the three fuels to be a little over 12 lbs. per hour for the 12 electrical h.p. given by the motor. still, the paraffin and naphthalene worked out about equal as to cost, and considering that the latter was in its purest form, as sold for a clothes preservative, we have yet to see how much better its commercial showing will be with lower grades, assuming beforehand that its thermal efficiency and behaviour are as good. "on the ground of convenience naphthalene, as a solid, is a very long way in front of its liquid rival, kerosene. its exhaust, too, was much freer from odour, and it appears that, unlike paraffin, it forms neither tar, soot, nor sticky matter, but, on the contrary, has a tendency to brighten all valves, cylinders, walls, etc., any little deposit being a light powder which would be carried into the exhaust." the two-stroke motor in the ordinary "otto-cycle" motor an explosion occurs once in every two revolutions of the crank. with a single cylinder the energy of the explosion must be stored up in a heavy fly-wheel to carry the engine through the three other operations of scavenging, sucking in a fresh charge, and compressing it preparatory to the next explosion. with two cylinders the fly-wheel can be made lighter, as an explosion occurs every revolution; and in a four-cylinder engine we might almost dispense with the wheel altogether, since the drive is continuous, just as in a double-cylindered steam-engine. the two-stroke motor, _i.e._ one which makes an explosion for every revolution, is an attempt to unite the advantages of a two-cylindered engine of the otto type with the lightness of a single-cylindered engine. as it has been largely used for motor boats, especially in america, a short description of its working may be given here. in the first place, all moving cylinder valves are done away with, their functions being performed by openings covered and opened by the movements of the piston. the crank chamber is quite gas-tight, and has in it a non-return valve through which vapour is drawn from the carburetter every time the piston moves away from the centre. there is also a pipe connecting it with the lower part of the cylinder, but the other end of this is covered by the piston until it has all but finished its stroke. let us suppose that an explosion has just taken place. the piston rushes downwards, compressing the gas in the crank chamber to some extent. when the stroke is three-parts performed a second hole, on the opposite side of the cylinder from the aperture already referred to, is uncovered by the piston, and the exploded gases partly escape. immediately afterwards the second hole is uncovered also, and the fresh charge rushes in from the crank case, being deflected upwards by a plate on the top of the piston, so as to help drive out the exhaust products. the returning piston covers both holes and compresses the charge till the moment of explosion, when the process is repeated. it may be said in favour of this type of engine that it is very simple and free from vibration; against it that, owing to the imperfect scavenging of exploded charges, it does not develop so much power as an otto-cycle engine of equal cylinder dimensions; also that it is apt to overheat, while it uses double the amount of electric current. motor boats for the navy a country which, like england, depends on the command of the sea for its very existence may well keep a sharp eye on any invention that tends to render that command more certain. in recent years we have heard a lot said, and read a lot written, about the importance of swift boats which in war time could be launched against a hostile fleet, armed with the deadly torpedo. the russo-japanese war has given us a fine example of what can be accomplished by daring men and swift torpedo craft. for some reason or other the british navy has not kept abreast of france in the number of her torpedo vessels. reference to official figures shows that, while our neighbours can boast 280 "hornets," we have to our credit only 225. in the house of commons, on august 10th, 1904, mr. henry norman, m.p., asked the secretary of the admiralty whether, in view of the proofs recently afforded of trustworthiness, speed, simplicity, and comparatively low cost of small vessels propelled by petrol motors, he would consider the advisability of testing this class of vessel in his majesty's navy. the secretary replied that the admiralty had kept a watch on the recent trials and meant to make practical tests with motor pinnaces. in view of the danger that would accompany the storage of petrol on board ship, the paraffin motor was preferable for naval purposes; and an 80 h.p. four-cylindered motor of this type has been ordered from messrs. vosper, of portsmouth. mr. norman, writing in _the world's work_ on the subject, says: "there can be no question that such high speed and cheap construction (80 h.p. giving in the little boat as much speed--to consider that only--as eight thousand in the big boat) point to the use of motor boats for naval purposes in the near future. a torpedo boat exists only to carry one or two torpedoes within launching distance of the enemy. the smaller and cheaper she can be, and the fewer men she carries, provided always she be able to face a fairly rough sea, the better. now the ordinary steam torpedo boat carries perhaps twenty men, and costs anything from â£50,000 to â£100,000. a motor boat of equal or greater speed could probably be built for â£15,000, and would carry a crew of two men. six motor boats, therefore, could be built for the cost of one steamboat, and their total crews would not number so many as the crew of the one. moreover, they could all be slung on board a single vessel, and only set afloat near the scene of action. a prophetic friend of mine declares that the most dangerous warship of the future will be a big vessel, unarmoured and only lightly armed, but of the utmost possible speed, carrying twenty or more motor torpedo boats slung on davits. she will rely on her greater speed for her own safety, if attacked; she will approach as near the scene of action as possible, and will drop all her little boats into the water, and they will make a simultaneous attack. their hulls would be clean, their machinery in perfect order, their crews fresh and full of energy, and it would be strange if one of the twenty did not strike home. and the destruction of a battleship or great cruiser at the cost of a score of these little wasps, manned by two-score men, would be a very fine naval bargain." mr. norman omits one recommendation that must in active service count heavily in favour of the motor boat, and that is its practical invisibility in the day or at night time. the destroyer, when travelling at high speed, betrays its presence by clouds of smoke or red-hot funnels. the motor boat is entirely free from such dangerous accompaniments; the exhaust from the cylinders is invisible in every way. the very absence of funnels must also be in itself a great advantage. the eye, roving over the waters, might easily "pick up" a series of stumpy, black objects of hard outline; but the motor boat, riding low and flatly on the waves, would probably escape notice, especially when a search-light alone can detect its approach. it may reasonably be said that the admiralty knows its own business best, and that the outsider's opinion is not wanted. the "man in the street" has become notorious for his paper generalship and strategy, and fallen somewhat into disrepute as an adviser on military and naval matters. yet we must not forget this: that many--we might say most--of the advances in naval mechanisms, armour, and weapons of defence have not been evolved by naval men, but by the highly educated and ingenious civilian who, unblinded by precedent or professional conservatism, can watch the game even better in some respects than the players themselves, and see what the next move should be. that move may be rather unorthodox--like the application of steam to men-o'-war--but none the less the correct one under the circumstances. we allowed other nations to lead us in the matter of breech-loading cannon, armour-plate, submarines, the abolition of combustible material on warships. shall we also allow them to get ahead with motor boats, and begin to consider that there _may_ be something in motor auxiliaries for the fleet when they are already well supplied? if there is a country which should above all others lose no time in adding the motor to her means of defence, that country is great britain. footnote: [12] _the motor boat_, march 16th, 1905. chapter ix the motor cycle in 1884 the count de dion, working in partnership with messrs. bouton and trã©pardoux, produced a practical steam tricycle. two years later appeared a somewhat similar vehicle by the same makers which attained the remarkable speed of forty miles an hour. mr. serpollet, now famous for his steam cars, built at about the same time a three-wheeled steam tricycle, which also proved successful. but the continuous stoking of the miniature boilers, and the difficulty of keeping them properly supplied with water, prevented the steam-driven cycle from becoming popular; and when the petrol motor had proved its value on heavy vehicles, inventors soon saw that the explosion engine was very much better suited for a light automobile than had been the cumbrous fittings inseparable from the employment of steam. by 1895 a neat petrol tricycle was on the market; and after the de dion machines had given proof in races of their capabilities, they at once sprang into popular favour. for the next five years the motor tricycle was a common sight in france, where the excellent roads and the freedom from the restrictions prevailing on the other side of the channel recommended it to cyclists who wished for a more speedy method of locomotion than unaided legs could give, yet could not afford to purchase a car. the motor bicycle soon appeared in the field. the earlier types of the two-wheeled motor were naturally clumsy and inefficient. the need of a lamp constantly burning to ignite the charges in the cylinder proved a much greater nuisance on the bicycle than on the tricycle, which carried its driving gear behind the saddle. the writer well remembers trying an early pattern of the werner motor bicycle in the champs elysã©es in 1897, and his alarm when the owner, while starting the blowlamp on the steering pillar, was suddenly enveloped in flames, which played havoc with his hair, and might easily have caused more serious injuries. riders were naturally nervous at carrying a flame near the handle-bars, so close to a tank of inflammable petrol liable to leak and catch fire. the advent of electrical ignition for the gaseous charges opened the way for great improvements, and the motor bicycle slowly but surely ousted its heavier three-wheeled rival. designs were altered; the engine was placed in or below the frame instead of over the front wheel, and made to drive the back wheel by means of a leather belt. in the earliest types the motive force had either been transmitted by belt to the front wheel, or directly to the rear wheel by the piston rods working cranks on its spindle. the progress of the motor bicycle has, since 1900, been rapid, and many thousands of machines are now in use. the fact that the engines must necessarily be very small compels all possible saving in weight, and an ability to run continuously at very high speeds without showing serious wear and tear. details have therefore been perfected, and though at the present day no motor cyclist of wide experience can claim immunity from trouble with his speedy little mount, a really well-designed and well-built machine proves wonderfully efficient, and opens possibilities of locomotion to "the man of moderate means" which were beyond the reach of the rider of a pedal-driven bicycle. in its way the motor cycle may claim to be one of the most marvellous products of human mechanical skill. weight has been reduced until a power equal to that of three horses can be harnessed to a vehicle which, when stored with sufficient petrol and electricity to carry it and rider 150 miles, scales about a hundredweight. it will pursue its even course up and down hill at an average of twenty or more miles an hour, the only attention it requires being an occasional charge of oil squirted into the air-tight case in which the crank and fly-wheels revolve. the consumption of fuel is ridiculously small, since an economical engine will cover fifteen miles on a pint of spirit, which costs about three-halfpence. practically all motor-cycle engines work on the "otto-cycle" principle. motors which give an impulse every revolution by compressing the charge in the crank-case or in a separate cylinder, so that it may enter the working cylinder under pressure, have been tried, but hitherto with but moderate success. there is, however, a growing tendency to compass an explosion every revolution by fitting two cylinders, and from time to time four-cylindered cycles have appeared. the disadvantages attending the care and adjustment of so many moving parts has been the cause of four-cylindered cycle motors being unsuccessful from a commercial standpoint, though riders who are prepared to risk extra trouble and expense may find compensation in the quiet, vibrationless drive of a motor which gives two impulses for every turn of the fly-wheel. the acme of lightness in proportion to power developed has been attained by the "barry" engine, in which the cylinders and their attachments are made to revolve about a fixed crank, and perform themselves the function of a fly-wheel. so great is the saving of weight that the makers claim a horse-power for every four pounds scaled by the engines; thus, a 3-1/2 h.p. motor would only just tip the beam against one stone. as the writer has personally inspected a barry engine, he is able to give a brief account of its action. it has two cylinders, arranged to face one another on opposite sides of a central air-tight crank-case, the inner end of each cylinder opening into the case. both pistons advance towards, and recede from, the centre of the case simultaneously. the air-and-gas mixture is admitted into the crank-case through a hole in the fixed crank-spindle, communicating with a pipe leading from the carburetter. the inlet is controlled by a valve, which opens while the pistons are parting, and closes when they approach one another. we will suppose that the engine is just starting. the pistons are in a position nearest to the crank-case. as they separate they draw a charge--equal in volume to double the cubical contents of one cylinder--into the crank-case through its inlet valve. during the return stroke the charge is squeezed, and passes through a valve into a chamber which forms, as it were, the fourth spoke of a four-spoked wheel, of which the other three spokes are the cylinders and the "silencer." this chamber is connected by pipes to the inlet valves of the cylinders, which are mechanically opened alternately by the action of special cams on the crank-shaft. the cylinder which gets the contents of the compression chamber receives considerably more "mixture" than would flow in under natural suction, and the compression is therefore greater than in the ordinary type of cycle motor, and the explosion more violent. hence it comes about that the cylinders, which have a bore of only 2 in. and a 2-in. stroke for the piston, develop nearly 2 h.p. each. it may at first appear rather mysterious how, if the cranks are rigidly attached to the cycle frame, any motion can be imparted to the driving-wheel. the explanation is simple enough: a belt pulley is affixed to one side of the crank-case, and revolves with the cylinders, the silencer, and compression chamber. the rotation is caused by the effort of the piston to get as far as possible away from the closed end of the cylinder after an explosion. where a crank is movable but the cylinder fixed, the former would be turned round; where the crank is immovable but the cylinder movable, the travel of the piston is possible only if the cylinder moves round the crank. a series of explosions following one another in rapid succession gives the moving parts of the barry engine sufficient momentum to suck in charges, compress them, and eject the burnt gases. the plan is ingenious, and as the machine into which this type of engine is built weighs altogether only about 70 lbs., the "sport" of motor cycling is open to those people whose age or want of strength would preclude them from the use of the heavy mounts which are still to be seen about the roads. in the future we may expect to find motor cycles approach very closely to a half-hundredweight standard without sacrificing the rigidity needful for fast locomotion over second-class roads. for "pace-making" on racing tracks, motor cycles ranging up to 24 h.p. have been used; but these are essentially "freak" machines of no practical value for ordinary purposes. even 3-4 h.p. cycles have set up wonderful records, exceeding fifty miles in the hour, a speed equal to that of a good express train. in comparison with the feats of motor-cars, their achievements may not appear very startling; but when we consider the small size and weight, and the simplicity of the mechanisms which propel cycle and rider at nearly a mile a minute, the result seems marvellous enough. during the last few years the tricycle has again come into favour, but with the arrangement of its wheels altered; two steering-wheels being placed in front, and a single driving-wheel behind. the main advantage of this inversion is that it permits the fixing of a seat in front of the driver, in which a passenger can be comfortably accommodated. the modern "tricar," with its high-powered, doubled-cylindered engines, its change-speed gears, its friction clutch for bringing the engines gradually into action, its forced water circulation for cooling the cylinders, and its spring-hung frame, is in reality more a car than a cycle, and escapes from the former category only on account of the number of its wheels. to the tourist, or to the person who does not find pleasure in solitary riding, the tricar offers many advantages, and, though decidedly more expensive to keep up than a motor bicycle, entails only very modest bills in comparison with those which affect many owners of cars. the development of the motor cycle has been hastened and fostered by frequent speed and reliability contests, in which the nimble little motor has acquitted itself wonderfully. a hill a mile long, with very steep gradients, has been ascended in considerably less than two minutes by a 3-1/4 h.p. motor. we read of motor cycles travelling from land's end to john-o'-groats; from calcutta to bombay; from sydney to melbourne; from paris to rome--all in phenomenal times considering the physical difficulties of the various routes. such tests prove the endurance of the motor cycle, and pave the way to its use in more profitable employments. volunteer cycling corps often include a motor or two, which in active service would be most valuable for scouting purposes, especially if powerful enough to tow a light machine-gun. commercial travellers, fitting a box to the front of a tricar, are able to scour the country quickly and inexpensively in quest of orders for the firms they represent. the police find the motor helpful for patrolling the roads. on the continent, and especially in germany, town and country postmen collect and deliver parcels and letters with the aid of the petrol-driven tricycle, and thereby save much time, while improving the service. before long, "hark 'tis the twanging horn" will once again herald the postman's approach in a thousand rural districts, but the horn will not hang from the belt of a horseman, such as the poet cowper describes, but will be secured to the handle-bars of a neat tricar. thus history repeats itself. [illustration: _photo_] [_cribb, southsea._ a motor lawn-mower a machine of this kind will cut several acres a day, and also acts as an efficient roller. the operator is able to empty the contents of the catch-box without leaving his seat.] that the motor cycle is still far from perfect almost goes without saying; but every year sees a decided advance in its design and efficiency. the messy, troublesome accumulator will eventually give way to a neat little dynamo, which is driven by the engine and creates current for exploding the cylinder charges as the machine travels. when the cycle is at rest there would then be no fear of electricity leaking away through some secret "short circuit," since the current ceases with the need for it, but starts again when its presence is required. the proper cooling of the cylinders has been made an easier matter than formerly by the introduction of fans which direct a stream of cold air on to the cylinder head. professor h. l. callendar has shown in a series of experiments that a fan, which absorbs only 2 to 3 per cent. of an engine's power, will increase the engine's efficiency immensely when a low gear is being used for hill climbing, and the rate of motion through the air has fallen below that requisite to carry off the surplus heat of the motor. if an engine maintains a good working temperature when it progresses through space two feet for every explosion, it would overheat if the amount of progression were, through the medium of a change-gear attachment, reduced to one foot, a change which would be advisable on a steep hill. the fan then supplies the deficiency by imitating the natural rush of air. as professor callendar says: "the most important point for the motor cyclist is to secure the maximum of power with the minimum of weight. with this object, the first essentials are a variable speed gear of wide range, and some efficient method of cooling to prevent overheating at low gears.... it is unscientific to double the weight and power of the machine in order to climb a few hills, when the same result can be secured with a variable gear. it is unnecessary to resort to the weight and complication of water cooling when a light fan will do all that is required." thus, with the aid of a fan and a gear which will give at least two speeds, the motor cyclist can, with an engine of 2 h.p., climb almost any hill, even without resorting to the help of the pedals. his motion is therefore practically continuous. to be comfortable, he desires immunity from the vibration which quick movement over any but first-class roads sets up in the machine, especially in its forward parts. several successful spring forks and pneumatic devices have been invented to combat the vibration bogy; and these, in conjunction with a spring pillar for the saddle, which can itself be made most resilient, relieve the rider almost entirely of the jolting which at the end of a long day's ride is apt to induce a feeling of exhaustion. the motor tricycle, which once had a rather bad name for its rough treatment of the nerves, is also now furnished with springs to all wheels, and approximates to the car in the smoothness of its progression. assuming, then, that we have motor vehicles so light as to be very manageable, sufficiently powerful to climb severe gradients, reliable, comfortable to ride, and economical in their consumption of fuel and oil, we are able to foresee that they will modify the conditions of social existence. the ordinary pedal-driven cycle has made it possible for the worker to live much further from his work than formerly. "to-morrow, with a motor bicycle, his home may be fifteen miles away, and those extra miles will make a great difference in rent, and in the health of his family. in fact, it almost promises to reconcile the garden city ideal with the industrial conditions of to-day, by enabling a man to work in the town, and have his home in the country. this advantage applies, of course, less to london than to other great cities, on account of the seemingly endless miles of streets to be traversed before the country is reached. in most manufacturing centres, however, the motoring workman could get to his cottage home by a journey of a few miles. even in london, moreover, this disadvantage will be overcome to a large extent in the future, for it is as certain as anything of the kind can be that we must ultimately have special highways, smooth, dustless, reserved for motor traffic, leading out of london in the principal directions.... my own conviction is that motor cycling, the simplest, the quickest, the cheapest independent locomotion that has ever been known, is destined to enjoy enormous development. i believe that within a few years the motor bicycle and tricycle will be sold by hundreds of thousands, and that many of the social and industrial conditions of our time will be greatly and beneficially affected by them."[13] footnote: [13] henry norman, esq., m.p., in _the world's work_. chapter x fire engines a good motto to blazon over the doors of a fire-brigade station would be "he gives help twice who gives help quickly." the spirit of it is certainly shown by the brave men who, as soon as the warning signal comes, spring to the engines and in a few minutes are careering at full speed to the scene of operations. speed and smartness have for many years past been associated with our fire brigades. we read how horses are always kept ready to be led to the engines; how their harness is dropped on to them and deft fingers set the buckles right in a twinkling, so that almost before an onlooker has time to realise what is happening the sturdy animals are beating the ground with flying hoofs. and few dwellers in large cities have not heard the cry of the firemen, as it rises from an indistinct murmur into a loud shout, before which the traffic, however dense, melts away to the side of the road and leaves a clear passage for the engines, driven at high speed and yet with such skill that accidents are of rare occurrence. the noise, the gleam of the polished helmets, the efforts of the noble animals, which seem as keen as the men themselves to reach the fire, combine to paint a scene which lingers long in the memory. but efficient as the "horsed" engine is, it has its limitations. animal strength and endurance are not an indefinite quantity; while the fireman grudges even the few short moments which are occupied by the inspanning of the team. in many towns, therefore, we find the mechanically propelled fire engine coming into favour. the power for working the pumps is now given a second duty of turning the driving-wheels. a parallel can be found in the steam-engine used for threshing-machines, which once had to be towed by horses, but now travels of itself, dragging machine and other vehicles behind it. the earlier types of automobile fire engines used the boiler's steam to move them over the road. liverpool, a very enterprising city as regards the extinction of fire, has for some time past owned a powerful steamer, which can be turned out within a minute of the call, can travel at any speed up to thirty miles an hour, and can pump 500 gallons per minute continuously. its success has led to the purchase of other motor engines, some fitted with a chemical apparatus, which, by the action of acid on a solution of soda in closed cylinders, is enabled to fling water impregnated with carbonic acid gas on to the fire the moment it arrives within working distance of the conflagration, and gives very valuable "first aid" while the pumping apparatus is being got into order. [illustration: two motor fire-engines built by messrs. merryweather, london. that on the left is driven by petrol, and in addition to pumping-gear carries a wheeled fire-escape. that on the right is driven by steam. both types are much faster than horses, being able to travel at a rate of over 20 miles an hour.] as might reasonably be expected, the petrol motor has found a fine field for its energies in connection with fire extinction. since it occupies comparatively little space, more accommodation can be allowed for the firemen and gear. furthermore, a petrol engine can be started in a few seconds by a turn of a handle, whereas a steamer is delayed until steam has been generated. messrs. merryweather have built a four-cylindered, 30 h.p. petrol fire engine capable of a speed of forty miles an hour. it has two systems of ignition--the magneto (or small dynamo) and the ordinary accumulator and coil--so that electrical breakdowns are not likely to occur. a fast motor of this kind, with a pumping capacity of 300 gallons per minute, is peculiarly suited for large country estates, where it can be made to perform household or farm duties when not required for its primary purpose. considering the great number of country mansions, historically interesting, and full of artistic treasures, which england boasts, it is a matter for regret that such an engine is not always included among the appliances with which every such property is furnished. how often we read "old mansion totally destroyed by fire," which usually means that in a few short hours priceless pictures, furniture, and other objects of art have been destroyed, because help, when it did come, arrived too late. owners are, however, more keenly alive to their responsibilities now than formerly. the small hand-worked engine, or the hydrant of moderate pressure, is not considered a sufficient guard for the house and its contents. in many establishments the electric lighting engines are designed to work either the dynamo or a set of pumps as occasion may demand; or the motor is mounted on wheels so that it may be easily dragged by hand to any desired spot. the "latest thing" in motor fire engines is one which carries a fire-escape with it, in addition to water-flinging machinery. an engine of this type is to be found in some of the london suburbs. a chemical cylinder lies under the driver's seat, where it is well out of the way, and coiled beside it is its reel of hose. the "escape" rests on the top of the vehicle, the wheels hanging over the rear end, while the top projects some distance in front of the steering wheels. the ladder, of telescopic design, can be extended to fifty feet as soon as it has been lowered to the ground. since the saving of life is even more important than the saving of property, it is very desirable that a means of escape should be at hand at the earliest possible moment after an outbreak. this combination apparatus enables the brigade to nip a fire in the bud, if it is still a comparatively small affair, and also to rescue any people whose exit may have been cut off by the fire having started on or near the staircases. the wolseley motor-car company has established a type of chemical motor fire engine which promises to be very successful. a 20 h.p. motor is placed forward under the frame to keep the centre of gravity low. when fully laden, it carries a crew of eight men, two 9-foot ladders, two portable chemical extinguishers, a 50-gallon chemical cylinder, and a reel on which is wound a hose fifty-three yards long. the wheels are a combination of the wooden "artillery" and the wire "spider," wires being strung from the outer end of the hub to the outer ends of the wooden spokes to give them increased power to resist the strain of sudden turns or collisions. an artillery wheel, not thus reinforced, is apt to buckle sideways and snap its spokes when twisted at all. england has always led the way in matters relating to fire extinction, and to her is due the credit of first harnessing mechanical motive power to the fire engine. other countries are following her example, and consequently we find fire apparatus moved by the petrol motor in places so far apart as cape town, valparaiso, mauritius, sydney, berlin, new york, montreal. there can be no doubt but that in a very few years horse-traction will be abandoned by the brigades of our large towns. it has been suggested that the fire-pump of the future will be driven by electricity drawn from switches on the street mains; enough current being stored in accumulators to move the pump from station to fire. in such a case it would be possible to use very powerful pumps, as an electric motor is extremely vigorous for its size and weight. even to-day steam fire engines can fling 2,000 gallons per minute, and fire floats (for use on the water) considerably more. possibly the engine of to-morrow will pour 5,000 gallons a minute on the flames if it can get that amount from the water mains, and so render it unnecessary to summon in a large number of engines to quell a big conflagration. three hundred thousand gallons an hour ought to check a very considerable "blaze." the force with which a jet of water leaves the huge nozzle of a powerful engine is so great that it would seriously injure a spectator at a distance of fifty yards. the "kick-back" of the water on the nozzle is sometimes sufficient to overcome the power of one man to hold the nozzle in position with his hands, and it becomes needful to provide supports with pointed ends to stick into the ground, or hooks which can be attached to the rungs of a ladder. for an attack on the upper storeys of a house a special "water tower" is much used in america. it consists of a lattice-work iron frame, about twenty-five feet long, inside which slides an extensible iron tube five inches in diameter. the tower is attached to one end of a wagon of unusual length and breadth, and is raised to a vertical position by a rack gearing with a quadrant built into its base below the trunnions or pivots on which it swings. carbonic acid gas, generated in a cylinder carried on the wagon, works a piston connected with the racks, and on a tap being turned slowly brings the tower to the perpendicular, when it is locked. the telescopic tube, carrying the hose inside it, is then pulled up by windlasses, until the 2-1/2-inch nozzle is nearly fifty feet from the ground. the nozzle itself can be rotated from below by rods and gearing, and the angle of the stream regulated by a rope. if several engines simultaneously deliver their water to the tower hoses 1,000 gallons a minute can be concentrated in a continuous 2-1/2-inch jet on to the fire. the ordinary horsed fire engine is simple in its design and parts. the vertical boiler contains a number of nearly horizontal water tubes, which offer a great surface to the furnace gases, so that it may raise steam very quickly. the actual water capacity of the boiler is small, and therefore it must be fed continuously by a special pump. the pumps, two or three in number, usually have piston rods working direct from the steam cylinders on the plungers of the pumps. between cylinders and pumps are slots in the rods in which rotate cranks connected with one another and with a fly-wheel which helps to keep the running steady. after leaving the pumps the water enters a large air vessel, which reduces the sudden shocks of delivery by the cushioning effect of the air, and causes a steady pressure on the water in the hoses. chapter xi fire-alarms and automatic fire extinguishers assuming that a town has a well-appointed fire brigade, equipped with the most up-to-date engines, it still cannot be considered efficiently protected against the ravages of the fire-fiend unless the outbreak of a fire can be notified immediately to the stations, and local mechanical means of suppression come into action almost simultaneously with the commencement of the conflagration. "what you do, do quickly" is the keynote of successful fire-suppression; and its importance has been practically recognised in the invention of hundreds of devices, some of which we will glance at in the following pages. the electric circuit is the most valuable servant that we have to warn us of danger. dotted about the streets are posts carrying at the top a circular box, which contains a knob. as soon as a fire is observed, anyone may run to such a post, smash the glass screening the knob, and pull out the latter. this action flashes the alarm to the nearest fire-station, and a few minutes later an engine is dashing to the rescue. help may also be summoned by means of the ordinary telephone exchanges or from police-stations in direct telephonic communication with the brigade depã´ts. all devices depending for their ultimate value on human initiative leave a good deal to be desired. they presuppose conditions which _may_ be absent. for instance, an electric wire in a large factory ignites some combustible material during the night. a passer-by may happen to see flames while the fire is in an early stage. on the other hand, it is equally probable that the conflagration may be well established before the alarm is given, with the result that the fire brigade arrives too late to do much good. what we need, therefore, is a mechanical means of calling attention to the danger automatically, with a quickness which will give the brigade or people close at hand a chance of strangling the monster almost as soon as it is born, and with a precision as to locality that will save the precious time wasted in hunting for the exact point to be attacked. mr. g. h. oatway, m.i.e.e., in a valuable paper read before the international congress of fire brigades in london in 1903, says that the difference between the damage resulting from a fire signalled in its early stage, and the same fire reported when it has spread to two or three floors, is often the difference between a nominal loss and a "burn out." the reformer, he continues, who aims at reducing fire waste must turn his attention primarily to hastening the alarm. the true cure of the matter is, not what quantity of gear it takes to deal with huge conflagrations, but how to concentrate at the earliest stage upon the outbreaks as they occur, and to check them before they have grown beyond control. he cites the fire record of glasgow of 1902, from which it appears that three fires alone accounted for 40 per cent. of the year's total loss, ten fires for 73 per cent., and the other 706 for only 27 per cent., or an average of â£72 per fire. had the first three fires only been notified at an earlier stage, nearly â£72,000 would have been saved. captain sir e. m. shaw, late chief of the london fire brigade, has put the following on record: "having devoted a very large portion of the active period of my working life in bringing into general use mechanical and hydraulic appliances for dealing with fires after they have been discovered, i nevertheless give and have always given the highest place to the early discovery and indication of fire, and not by any means to the steam, the hydraulic, or the numerous other mechanical appliances on which the principal labours of my life have been bestowed." a fire given fifteen minutes' start is often hard to overtake. imagine a warehouse alight on three floors before the alarm is raised! engines may come one after another and pour deluges of water on the flames, yet as likely as not we read next morning of "total destruction." no stitch in time has saved nine! the sad part about fires is that they represent so much absolute waste. in commercial transactions, if one party loses the other gains; wealth is merely transferred, and still remains in the community. but in the matter of fire this is not the case. supposing that a huge cotton mill is burnt down. the re-erection will, it is true, cause a lot of money to change hands; but what has resulted from the money that has _already_ been put into the mill? nothing. so many hundred thousands of pounds have been dematerialised and left nothing behind to represent them. the great ottawa fire of a few years ago may be remembered as a terrible example of such total loss of human effort. the history of fire-alarms the first recorded specification for an automatic detecting device bears the date 1763. in that year a mr. john greene patented an arrangement of cords, weights, and pulleys, which, when the cord burnt through, caused the movement of an indicating semaphore arm. as this action appealed only to the eye, it might easily pass unnoticed, and we can imagine that mr. greene did not find a gold mine in his invention. twenty-four years later an advance was made when william stedman introduced a "philosophical fire alarum." "his apparatus consisted of a pivoted bulb having an open neck, and containing mercury, spirit or other liquid. as the heat of the room increased, the expansion of the fluid caused it to spill over, release a trigger, and allow a mechanical gong to run down. this arrangement, whilst an advance upon the first referred to, is quite impracticable. evaporation of fluid, expansion of mercury, a stiff crank, or other causes which will readily occur to you, and the thing is useless."[14] in 1806 an automatic method for sprinkling water over a fire appeared. the idea was simplicity itself: a network of water mains, with taps controlled by cords, which burnt through and turned on the water. william congreve patented, three years later, a sprinkler which was an improvement, in that it indicated the position of the fire in a building by dropping one of a number of weights. but string is not to be relied upon. it may "perish" and break when no fire is about, and any system of extinction depending on it might prove a double-edged weapon. the nineteenth century produced hundreds of devices for alarming and extinguishing automatically. all depended upon the principle of the expansion or melting of metal in the increased temperature arising from a fire. at one time the circuit-closing thermometer was popular on account of its simplicity. "its drawback," says mr. oatway, "is the smallness of its heat-collecting surface, its isolation, and, last and worst of all, its fixity of operation. in thermometer or fuse-alarm practice it is usual to place the detectors at intervals of about ten feet or so, so that a room of any size will contain a number. if a fire breaks out, the ceiling is blanketed with heat, and every detector feels its influence. each is affected, but none can give the alarm until some one of the number absolutely reaches the set point or melts out. having no means of varying the composition of the solder or shifting the wire, an actuating point must be selected which is high enough to give a good working margin over the maximum industrial or seasonal heat of the year; and thus it comes about that if the fire breaks out in winter, or when the room is at its lowest temperature, the amount of loss is considerably and quite unnecessarily increased. in a device set to fuse at 150â° fahrenheit, it will be clear to every one that the measure of the damage will depend upon the normal temperature of the room at the time of the outbreak. if the mercury is in the nineties, there is only some sixty degrees of a rise to wait for; whilst if it happens to be a winter's night, the alarm is held back for a rise of perhaps 120â°. what chance is there in this case for a good stop?" mr. oatway has examined the fuses under different conditions, and his conclusions are drawn from practical tests. great intelligence will not be required to appreciate the force of his arguments. inasmuch as the rise of temperature caused by a fire is relative, during the early stages at least, to the general heat of the atmosphere, it becomes obvious that an automatic fire-alarm should be one which will keep parallel, as it were, with fluctuations of natural heat. thus, if the "danger rise" be fixed at 100â°, the alarm should be given on a cold night as certainly as at midday in summer. it was the failure of early patterns in this respect that led to their being discredited by the fire-brigade authorities. the writer already quoted has laid down the functions of a perfect alarm:-(a) to detect the fire at a uniformly early period, under all atmospheric and industrial conditions. (b) to give the alarm upon the premises, and simultaneously to the brigade, by a definite and unmistakable message. (c) to facilitate the work of extinction by indicating the position of the outbreak in the building attacked. the "may oatway" alarm has got round the first difficulty in a most ingenious manner by adapting the principle of the compensation methods already described in connection with watches. the alarm consists of a steel rod of a section found to be most suitable for the purpose. to the side is attached by screws entering the rod near the ends a copper wire, which is long enough to sag slightly at its centre, from which depends a silver chain carrying a carbon contact-piece. a short distance below the carbon are the two terminals of the electric circuit which, when completed by the lowering of the carbon, gives the alarm. now if there be a very gradual change of temperature the steel rod lengthens slowly, and so does the copper wire, so that the amount of sag remains practically what it was before. but in event of a fire the copper expands much more quickly than the steel, and sags until the carbon completes the circuit. the whole thing is beautifully simple, very durable, quite consistent, and reliable. as soon as the temperature diminishes, on the extinction of the fire, the alarm automatically returns to its normal position, ready for further work. now for the second function, that of giving the alarm in many places at once. the closed circuit does not itself directly cause bells to ring: it works a "relay," that is, a second and more powerful circuit. in fact, it is the counterpart of the engine driver, who does not himself make the locomotive move, but merely turns on the steam. an installation has been introduced in the poplar workhouse--to quote an instance. were a fire to break out, one of the 276 detectors would soon set twenty-five bells in action, one in each officer's room. similarly, in the warehousemen's orphanage at cheadle hulme, every dormitory would be aroused, and every officer, including the principal in his house some distance away. messrs. arthur and company, of glasgow, have a warehouse fortified with 600 of these "nerve centres," all yoked to four position indicators, three of which actuate a "master" indicator connected with the central fire-station. there is no hole or corner in this huge establishment where the fire-demon could essay his fell work without being at once spied upon by a detector. we may glance for a moment at the mechanism which sends an unmistakable message for help. at the brigade station there is a number of small tablets, each protected by a flap, on the outside of which is the word safe, on the inside fire. normally the flap is closed. as soon as the circuit is completed, a magnet releases the flap, and a bell begins to ring. now, it is possible that the circuit might be closed accidentally by contact somewhere between the premises it serves and the fire-station. so that the official on guard, seeing "j. brown and company" on the uncovered tablet, might despatch the engines to the place indicated on a wild-goose chase. to prevent such false alarms the transmitter not only rings the station up, but automatically sends an unmistakable message. when a fire occurs an automatic printing machine is set in motion to despatch a cipher in the morse code _four times_ to the station. an accidental circuit could not do this; therefore, when the officer sees on the receiving tape the well-known cipher, he turns out his men with all speed. on arriving at their destination the firemen receive valuable help from the "position indicator," which guides them to their work. on a special board is seen a row, or rows, of shutters similar to those already mentioned. each row belongs to a floor; each unit of the row to a room. a glance suffices to tell that the trouble is, say, in the most southerly room of the second floor. no notice is therefore taken of smoke rolling out of other parts of the building, until the danger spot has been attacked. that the firemen appreciate such an ally goes without saying. every fire extinguished is a point to their credit. also, the risks they run are greatly diminished, while the wear and tear of tackle is proportionately reduced. the fireman is noted for his courage and unflinching performance of duty. the discomforts of his profession are sometimes severe, and its dangers as certain as they are at times appalling. therefore we welcome any mechanical method which at once shortens his work, lessens his peril, and protects property from damage. mr. oatway draws special attention to the need for simultaneous warning on the premises and at the fire-station. "i remember," he says, "many cases, but perhaps no better illustration need be looked for than the case of a cotton mill in lancashire about two years ago (1901). the fire was seen to start at a few minutes past seven; a fuse blew out, and sparked some cotton; but it looked such a simple job that the operatives elected to deal with it. at twenty minutes to eight it dawned upon somebody that the brigade had better be sent for, because the fire was getting away; and in due course they arrived; but the mill, already doomed, became a total loss. in every centre similar instances can be quoted. there is nothing in any automatic system to discourage individual effort. inmates can put the fire out, if able; but in any case the brigade gets timely and definite notice, and if on their arrival they find the fire extinguished, as chief superintendent thomas put it when we opened the dingle station after the fatal train-burning, 'so much the better, we shall get to our beds all the quicker.' this is the common-sense view of it. helpers work none the less intelligently because they know the brigade is coming; and it is necessary to provide some automatic method of calling them, because you can never rely upon anybody who is unfamiliar with fire doing the right thing at the proper time." messrs. may and oatway, who give their name to the alarm described above, first introduced their apparatus in new zealand, from which country it has spread over the british empire. the largest installation is at messrs. clark and company's anchor mills, paisley. the whole of the immense block of buildings, the greater part of which was previously protected by "sprinklers" only, is now electrically protected also; and connected up with the fire brigade, and through their station with the sleeping quarters of every fireman. some figures will be interesting here. there are 119 _miles_ of internal alarm circuits; 5-1/4 miles of underground cable between buildings; 19 automatic telegraphs; 21 automatic position indicators; 20 alarm gongs a foot in diameter. early in january, 1905, a fire broke out in these buildings during the dinner hour, when most of the works' firemen were at their midday meal. the alarm sounded simultaneously at the works' fire-station and at the firemen's houses, which are situated on the other side of the street from the mill. the firemen were on the spot immediately, and were enabled to subdue the flames, which had broken out in the building occupied as warehouse and office, before it had got a firm hold of the inflammable material, although not before one of the large stacks of finished thread was ablaze. the brigade, however, were soon masters of the situation, and the damage done was under â£100. there is little doubt, had the alarm been left to the ordinary course, the building would have been totally destroyed.[15] in those few minutes the installation saved its entire cost many times over. truly "a little fire is quickly trodden out, which, being suffered, rivers cannot quench." here, in a shakespearean nutshell, is the whole science of fire protection. automatic sprinklers as these have been referred to several times a short description may appropriately be given. the building which they protect is fitted with a network of mains and branches ramifying into each room. at the end of each branch is a nozzle, the mouth of which is bridged over by a metal arch carrying a small plate. between the bridge and a glass plug closing the nozzle is a bar of easily fusible solder. when the temperature has risen to danger point the solder melts, and the plug is driven out by the water, which strikes the plate and scatters in all directions. this device has proved very valuable on many occasions. the _encyclopã¦dia britannica_ (tenth edition) states that, in the record of the american associated factory mutual companies for the 5-1/2 years ending january 1, 1900, it appears that out of 563 fires where sprinklers came into play 129 were extinguished by one jet; 83 by two jets; 61 by three; 44 by four; 40 by five. the fire-bucket is the simplest device we have as a first aid; and very effective it often proves. insurance statistics show that more fires are put out by pails than by all other appliances put together. the important point to be remembered in connection with them is that they should always _be kept full_; so that, at the critical moment, there may be no hurried rushing about to find the two gallons of liquid which each is supposed to contain permanently. in _cassier's magazine_ (vol. xx. p. 85) is given an account of the manner in which an ingenious mill superintendent ensured the pails on the premises being ready for duty. the hooks carrying the pails were fitted up with pieces of spring steel strong enough to lift the pail when nearly empty, but not sufficiently so to lift a full pail. just over each spring, in such a position as to be out of the way of the handle of the pail, was set a metal point, connected with a wire from an open-circuit battery. so long as the pails were full, their weight, when hung on their hooks, kept the springs down, but as soon as one was removed, or lost a considerable part of its contents by evaporation or otherwise, the spring on its hook would rise, come into contact with the metal point, thus close the battery circuit and ring a bell in the manager's office, at the same time showing which was the bucket at fault. the bell continued to ring till the deficiency had been made right; and by this simple contrivance the buckets were protected from misuse or lack of attention. footnotes: [14] mr. w. h. oatway. [15] _glasgow evening news._ chapter xii the machinery of a ship the reversing engine--marine engine speed governors--the steering engine--blowing and ventilating apparatus--pumps--feed heaters--feed-water filters--distillers--refrigerators--the search-light--wireless telegraphy instruments--safety devices--the transmission of power on a ship with many travellers by sea the first impulse, after bunks have been visited and baggage has been safely stored away, is to saunter off to the hatches over the engine-room and peer down into the shining machinery which forms the heart of the vessel. some engine is sure to be at work to remind them of the great power stored down there below, and to give a foretaste of what to expect when the engine-room gong sounds and the man in charge opens the huge throttle controlling some thousands of horse-power. by craning forward over the edge of the ship, a jet of water may be seen spurting from a hole in the side just above the water-line, denoting either that a pump is emptying the bilge, or that the condensers are being cooled ready for the work before them. towards the forecastle a busy little donkey engine is lifting bunches of luggage off the quay by means of a rope passing over a swinging spar attached to the mast, and lowering it into the nether regions where stevedores pack it neatly away. in a small compartment on the upper deck is some mysterious, and not very important-looking, gear: yet, as it operates the rudder, it claims a place of honour equalling that of the main engines which turn the screw. to the ordinary passenger the very existence of much other machinery--the reversing engines, the air-pumps, the condensers, the "feed" heaters, the filters, the evaporators and refrigerators, and the ventilators--is most probably unsuspected. the electric light he would, from his experience of things ashore, vaguely connect with an engine "somewhere." but the apparatus referred to either works so unobtrusively or is so sequestered from the public eye that one might travel for weeks without even hearing mention of it. on a warship the amount of machinery is vastly increased. in fact, every war vessel, from the first-class battleship to the smallest "destroyer," is practically a congeries of machines; accommodation for human beings taking a very secondary place. big guns must be trained, fed, and cleaned by machinery; and these processes, simple as they sound, need most elaborate devices. the difference in respect of mechanism between the _king edward vii._ and nelson's _victory_ is as great as that between a motor-car and a farmer's cart. it would not be too much to say that the mechanical knowledge of any period is very adequately gauged from its fighting vessels. [illustration: _photo_] [_cribb, southsea._ a gigantic sheer-legs used for lowering boilers, big guns, turrets, etc., into men-of-war. the legs rise to a height of 140 feet, and will handle weights up to 150 tons.] during the last twenty years marine engines have been enormously improved. but the advance of auxiliary appliances has been even more marked. in earlier times the matter considered of primary importance was the propulsion of the vessel; and engineers turned their attention to the problem of crowding the greatest possible amount of power into the least possible amount of space. this was effected mainly by the "compounding" of engines--using the steam over and over again in cylinders of increasing size--and by improving the design of boilers. as soon as this business had been well forwarded, auxiliary machinery, which, though not absolutely necessary for movement, greatly affected the ease, comfort, and economy of working a ship, got its share of notice, with the result that a tour round the "works" of a modern battleship or liner is a growing wonder and a liberal education in itself. this chapter will deal with the auxiliaries to be found in large vessels designed for peaceful or warlike uses. many devices are common to ships of both classes, and some are confined to one type only, though the "steel wall" certainly has the advantage with regard to multiplicity. we may begin with the reversing engine all marine engines should be fitted with some apparatus which enables the engineer to reverse them from full speed ahead to full speed astern in a few seconds. the effort required to perform the operation of shifting over the valves is such as to necessitate the help of steam. therefore you will find a special device in the engine-room which, when the engineer moves a small lever either way from the normal position, lets steam into a cylinder and moves rods reversing the main engine. by a link action (which could not be explained without a special diagram) the valves of the auxiliary are closed automatically as soon as the task has been performed; so that there is no constant pressure on the one or the other side of its piston. to prevent the reversal being too sudden, the auxiliary's piston-rod is prolonged, and fitted to a second piston working in a second cylinder full of glycerine or oil. this piston is pierced with a small hole, through which the incompressible liquid passes as the piston moves. since its passage is gradual, the engines are reversed deliberately enough to protect their valves from any severe strains. these reversing engines can, if the steam serving them fails, be worked by hand. marine engine speed governors when a ship is passing through a strong sea and pitches as she crosses the waves, the screw is from time to time lifted clear of the water, and the engines which a moment before had been doing their utmost, suddenly find their load taken off them. the result is "racing" of the machinery, which makes itself very unpleasantly felt from one end of the ship to the other. then the screw, revolving at a speed much above the normal, suddenly plunges into the water again, and encounters great resistance to its revolution. a series of changes from full to no "load," as engineers term it, must be harmful to any engines, even though the evil effects are not shown at once. great strains are set up which shake bolts loose, or may crack the heavy standards in which the cranks and shaft work, and even seriously tax the shaft itself and the screw. on land every stationary engine set to do tasks in which the load varies--which practically means all stationary engines--are fitted with a governor, to cut off the steam directly a certain rate of revolution is exceeded. these engines are the more easily governed because they carry heavy fly-wheels, which pick up or lose their velocity gradually. a marine engine, on the other hand, has only the screw to steady it, and this is extremely light in proportion to the power which drives it; in fact, has scarcely any controlling influence at all as soon as it leaves the water. marine engineers, therefore, need some mechanical means of restraining their engines from "running away." the device must be very sensitive and quick acting, since the engines would increase their rate threefold in a second if left ungoverned when running "free"; while on the other hand it must not throttle the steam supply a moment after the work has begun again when the screw takes the water. many mechanisms have been invented to curb the marine engine. some have proved fairly successful, others practically useless; and the fact remains that, owing to the greater difficulty of the task, marine governing is not so delicate as that of land engines. a great number of steamships are not fitted with governors, for the simple reason that the engineers are sceptical about such devices as a class and "would rather not be bothered with them." but whatever may have been its record in the past, the marine governor is at the present time sufficiently developed to form an item in the engine-rooms of many of our largest ships. we select as one of the best devices yet produced that known as andrews' patent governor; and append a short description. it consists of two main parts--the pumps and the ram closing the throttle. the pumps, two in number, are worked alternately by some moving part of the engine, such as the air-pump lever. they inject water through a small pipe into a cylinder, the piston-rod of which operates a throttle valve in the main steam supply to the engines. at the bottom of this cylinder is a by-pass, or artificial leak, through which the water flows back to the pumps. the size of the flow through the by-pass is controlled by a screw adjustment. we will suppose that the governor is set to permit one hundred revolutions a minute. as long as that rate is not exceeded the by-pass will let out as much water as the pumps can inject into the cylinder, and the piston is not moved. but as soon as the engines begin to race, the pumps send in an excess, and the piston immediately begins to rise, closing the throttle. as the speed falls, the leak gets the upper hand again, and the piston is pushed down by a powerful spring, opening the throttle. it might be supposed that, when the screw "races," the pumps would not only close the throttle, but also press so hard on it as to cause damage to some part of the apparatus before the speed had fallen again. this is prevented by the presence of a second control valve (or leak) worked by a connecting-rod rising along with the piston-rod of the ram. the two rods are held in engagement by a powerful spring which presses them together, so that a hollow in the first engages with a projection on the second. immediately the pressure increases and the piston rises, the second valve is shut by the lifting of its rod, and so farther augments the pressure in the cylinder and quickens the closing of the throttle valve. this pressure increase must, however, be checked, or the piston would overrun and stop the engines. so when the piston has nearly finished its stroke the connecting-rod comes into contact with a stop which disengages it from the piston-rod and allows the second control valve to be fully opened by the spring pulling on its rod. the piston at once sinks to such a position as the pressure allows, and the action is repeated time after time. the governing is practically instantaneous, though without shock, and is said to keep the engine within 3 per cent. of the normal rate. that is, if 100 be the proper number of revolutions, it would not be allowed to exceed 103 or drop below 97. such governing is, in technical language, very "close." the idea is very ingenious: pumps working against a leak, and as soon as they have mastered it, being aided by a secondary valve which reduces the size of the leak so as to render the effect of the pumps increasingly rapid until the throttle has been closed. then the secondary valve is suddenly thrown out of action, gives the leak full play, and causes the throttle to open quickly so that the steam may be cut off only for a moment. by the turning of a small milled screw-head a couple of inches in diameter the pace of 5,000 h.p. engines is as fully regulated as if a powerful brake were applied the moment they exceeded "the legal limit." steering engines the uninitiated may think that the man on the bridge, revolving a spoked-wheel with apparently small exertion, is directly moving the rudder to port or to starboard as he wishes. but the helm of a large vessel, travelling at high speed, could not be so easily deflected were not some giant at work down below in obedience to the easy motions of the wheel. sometimes in a special little cabin on deck, but more often in the engine-room, where it can be tended by the staff, there is the steering engine, usually worked by steam-power. two little cylinders turn a worm-screw which revolves a worm-wheel and a train of cogs, the last of which moves to right or left a quadrant attached to the chains or cables which work the rudder. all that the steersman has to do with his wheel is to put the engine in forward, backward, or middle gear. the steam being admitted to the cylinders quickly moves the helm to the position required. a particularly ingenious steam gear is that made by messrs. harfield and company, of london. its chief feature is the arrangement whereby the power to move the rudder into any position remains constant. if you have ever steered a boat, you will remember that, when a sudden curve must be made, you have to put far more strength into the tiller than would suffice for a slight change of direction. now, if a steam-engine and gear were so built as to give sufficient pressure on the helm in all positions, it would, if powerful enough to put the ship hard-a-port, evidently be overpowered for the gentler movements, and would waste steam. the harfield gear has the last of the cog-train--the one which engages with the rack operating the tiller--mounted eccentrically. the rack itself is not part of a circle, but almost flat centrally, and sharply bent at the ends. in short, the curve is such that the rack teeth engage with the eccentric cog at all points of the latter's revolution. when the helm is normal the longest radius of the eccentric is turned towards the rack. in this position it exerts least power; but least power is then needed. as the helm goes over, the radius of the cogs gradually decreases, and its leverage proportionately increases. so that the engine is taxed uniformly all the time. some war vessels, including the ill-fated russian cruiser _variag_, have been fitted with electric steering gear, operated by a motor in which the direction of the current can be varied at the will of the helmsman. all power gears are so arranged that, in case of a breakdown of the power, a hand-wheel can be quickly brought into play. blowing and ventilating apparatus a railway locomotive sends the exhaust steam up the funnel with sufficient force to expel all air from the same and to create a vacuum. the only passage for the air flying to fill this empty space lies through the fire-box and tubes traversing the boiler from end to end. were it not for the "induced draught"--the invention of george stephenson--no locomotive would be able to draw a train at a higher speed than a few miles an hour. on shipboard the fresh water used in the boilers is far too precious to be wasted by using it as a fire-exciter. salt water to make good the loss would soon corrode the boilers and cause terrible explosions. therefore the necessary draught is created by _forcing_ air through the furnaces instead of by _drawing_ it. the stoke-hold is entirely separated from the outer air, except for the ventilators, down which air is forced by centrifugal pumps at considerable pressure. this draught serves two purposes. it lowers the temperature of the stoke-hold, which otherwise would be unbearable, and also feeds the fires with plenty of oxygen. the air forced in can escape in one way only, viz. by passing through the furnaces. when the ship is slowed down the "forced draught" is turned off, and then you see the poor stokers coming up for a breath of fresh air. in the red sea or other tropical latitudes these grimy but useful men have a very hard time of it. while passengers up above are grumbling at the heat, the stoker below is almost fainting, although clad in nothing but the thinnest of trousers. in the engine-room also things at times become uncomfortably warm. take the case of the united states monitor _amphitrite_, which went into commission in 1895 for a trial run. both stoke-hold and engine-room were very insufficiently ventilated. the vessel started from hampton roads for brunswick, georgia. "the trip of about 500 miles occupied five days in the latter part of july, and, for sheer suffering, has perhaps seldom been equalled in our naval history. the fire-room (stoke-hold) temperature was never below 150â°, and often above 170â°, while the engine-room ranged closely about 150â°. for the first twenty-four hours the men stood it well, but on the second day seven succumbed to the heat and were put on the sick list, one of them nearly dying; before the voyage was ended, twenty-eight had been driven to seek medical attendance. the gaps thus created were partially filled with inexperienced men from the deck force, until there was only a lifeboat's crew left in each watch.... on the evening of the fourth day out our men had literally fought the fire to a finish and had been vanquished; the watch on duty broke down one by one, and the engines, after lumbering along slower and slower, actually stopped for want of steam.... at daybreak the next morning we got under way and steamed at a very conservative rate to our destination, fortunately only about ten miles distant. the scene in the fire-room that morning was not of this earth, and far beyond description. the heat was almost destructive to life; steam was blowing from many defective joints and water columns; tools, ladders, doors, and all fittings were too hot to touch; and the place was dense with smoke escaping from furnace doors, for there was absolutely no draught. the men collected to build up the fires were the best of those remaining fit for duty, but they were worn out physically, were nervous, apprehensive, and dispirited. rough irish firemen, who would stand in a fair fight till killed in their tracks, were crying like children, and begging to be allowed to go on deck, so completely were they unmanned by the cruel ordeal they had endured so long. 'hell afloat' is a nautical figure of speech often idly used, but then we saw it. for a month thereafter the ship was actively employed on the southern coast, drilling militia at different ports, and sweltering in the new dock at port royal. one trip of twenty-nine hours broke the record for heat, the fire-room being frequently above 180â°. all fire-room temperatures were taken in the actual spaces where the men had to work, and not from hot corners or overhead pockets."[16] the ventilators were subsequently altered, and the men enjoyed comparative comfort. the words quoted will suffice to establish the importance of a proper current of air where men have to work. one of the greatest difficulties encountered in deep mining is that, while the temperature approaches and sometimes passes that of a stoke-hold, the task of sending down a cool current from above is, with depths of 4,000 ft. and over, a very awkward one to carry out. on passenger ships the fans ventilating the cabins and saloons are constantly at work, either sucking out foul air or driving in fresh. the principle of the fan is very similar to that of the centrifugal water pump--vanes rotating in a case open at the centre, through which the air enters, to be flung by the blades against the sides of the case and driven out of an opening in its circumference. sometimes an ordinary screw-shaped fan, such as we often see in public buildings, is employed. pumps every steamship carries several varieties of pump. first, there are the large pumps, generally of a simple type, for emptying the bilge or any compartment of the ship which may have sprung a leak. "all hands to the pumps!" is now seldom heard on a steamer, for the opening of a steam-cock sets machinery in motion which will successfully fight any but a very severe breach. it is needless to say that these pumps form a very important part of a ship's equipment, without which many a fine vessel would have sunk which has struggled to land. the pumps for the condensers form another class. these are centrifugal force pumps; their duty is to circulate cold sea-water round the nests of tubes through which steam flows after passing through the cylinders. it is thus converted once more into water, ready for use again in the boiler. every atom of the water is evaporated, condensed, and pumped back into the boiler once in a period ranging from fifteen minutes to an hour, according to the type of boiler and the size of the supply tanks. some condensers have the cooling water passed through the tubes, and the steam circulated round these in an air-tight chamber. in any case, the condenser should be so designed as to offer a large amount of cold surface to the hot vapour. a breakdown of the condenser pumps is a serious mishap, since steam would then be wasted, which represents so much fresh water--hard to replace in the open sea. it would be comparable to the disarrangement of the circulating pump on a motor-car, though the effects are different. we must not forget the feed-pumps for the boilers. on their efficient action depends the safety of the ship and her passengers. water must be maintained at a certain level in the boiler, so that all tube and other surfaces in direct contact with the furnace gases may be covered. the disastrous explosions we sometimes hear of are often caused by the failure of a pump, the burning of a tube or plate, and the inevitable collapse of the same. the firms of weir and worthington are among the best-known makers of the special high-pressure pumps used for throwing large quantities of water into the boilers of mercantile and war vessels. feed heaters as the fuel supply of a vessel cannot easily be replenished on the high seas, economy in coal consumption is very desirable. if you put a cold spoon into a boiling saucepan ebullition is checked at once, though only for a moment, while the spoon takes in the temperature of the water. similarly, if cold water be fed into a boiler the steam pressure at once falls. therefore the hotter the feed water is the better. the feed heater is the reverse of the condenser. in the latter, cold water is used to cool hot steam; in the former, hot steam to heat cold water. there are many patterns of heaters. one type, largely used, sprays the cold water through a valve into a chamber through which steam is passed from the engines. the spray, falling through the hot vapour, partially condenses it and takes up some of its heat. the surplus steam travels on to the condensers. a float in the lower part of the chamber governs a valve admitting steam to the boiler pumps, so that as soon as a certain amount of water has accumulated the pumps are started, and the hot liquid is forced into the boiler. another type, the hampson feeder, sends steam through pipes of a wavy form surrounded by the feed water, there being no actual contact between liquid and vapour. an ally of the heater is the feed-water filter, which removes suspended matter which, if it entered the boiler, would form a deposit round the tubes, and while decreasing their efficiency, make them more liable to burning. the most dangerous element caught by the filters is fatty matter--oil which has entered the cylinders and been carried off by the exhaust steam. the filter is either high pressure, _i.e._ situated between the pump and the boiler; or low pressure, _i.e._ between the pump and the reservoir from which it draws its water. the second class must have large areas, so as not to throttle the supply unduly. many kinds of filtering media have been tried--fabrics of silk, calico, cocoanut fibre, towelling, sawdust, cork dust, charcoal, coke; but the ideal substance, at once cheap, easily obtainable, durable, and completely effective, yet remains to be found. a filter should be so constructed that the filtering substance is very accessible for cleansing or renewal. distillers we now come to a part of a ship's plant very necessary for both machines and human beings. many a time have people been in the position of the ancient mariner, who exclaimed:- "water, water, everywhere, but not a drop to drink!" water is so weighty that a ship cannot carry more than a very limited quantity, and that for the immediate needs of her passengers. the boilers, in spite of their condensers, waste a good deal of steam at safety valves through leaking joints and packings, and in other ways. this loss must be made good, for, as already remarked, salt water spells the speedy ruin of any boiler it enters. the distiller in its simplest form combines a boiler for changing water into vapour, with a condenser for reconverting it to liquid. solids in impure water do not pass off with the steam, so that the latter, if condensed in clean vessels, is fit for drinking or for use in the engine boilers. a pound of steam will, under this system, give a pound of water. but as such procedure would be extravagant of fuel, _compound_ condensers are used, which act in the following manner. high-pressure steam is passed from the engine boilers into the tubes of an evaporator, and converts the salt water surrounding it into steam. the boiler steam then travels into its own condenser or into the feed water heater, while the steam it generated passes into the coils of a second evaporator, converts water there into steam, and itself goes to a condenser. the steam generated in the second evaporator does similar duty in a third evaporator. so that one pound of high-pressure steam is directly reconverted to water, and also indirectly produces between two and three pounds of fresh water. the condensers used are similar to those already described in connection with the engines, and need no further comment. about the evaporators, it may be said that they are so constructed that they can be cleaned out easily as soon as the accumulation of salt and other matter renders the operation necessary. usually one side is hinged, and provided with a number of bolts all round the edges which are quickly removed and replaced. the united states navy includes a ship, the _iris_, whose sole duty is to supply the fleet she attends with plenty of fresh water. she was built in 1885 by messrs. r. and w. hawthorn, of newcastle-on-tyne, and measures 310 feet in length, 38-1/2 feet beam. for her size she has remarkable bunker capacity, and can accommodate nearly 2,500 tons of coal. fore and aft are huge storage tanks to hold between them about 170,000 gallons of fresh water. her stills can produce a maximum of 60,000 gallons a day. it has been reckoned that each _ton_ of water distilled costs only 18 cents; or, stated otherwise, that 40 gallons cost one penny. at many ports fresh water costs three or four times this figure; and even when procured is of doubtful purity. during the spanish-american war the _iris_ and a sister ship, the _rainbow_, proved most useful. refrigerators of late years the frozen-meat trade has increased by leaps and bounds. australia, new zealand, argentina, canada, and the united states send millions of pounds' worth of mutton and beef across the water every year to help feed the populations of england and europe. in past times the live animals were sent, to be either killed when disembarked or fatted up for the market. this practice was expensive, and attended by much suffering of the unfortunate creatures if bad weather knocked the vessel about. refrigerating machinery has altered the traffic most fundamentally. not only can more meat be sent at lower rates, but the variety is increased; and many other substances than flesh are often found in the cold stores of a ship--butter and fruit being important items. certain steamship lines, such as the shaw, savill, and albion--plying between england and australasia--include vessels specially built for the transport of vast numbers of carcases. upwards of a million carcases have been packed into the hull of a single ship and kept perfectly fresh during the long six weeks' voyage across the equator. every passenger-carrying steamer is provided with refrigerating rooms for the storage of perishable provisions; and as the comfort of the passengers, not to say their luxury, is bound up with these compartments, it will be interesting to glance at the method employed for creating local frost amid surrounding heat. the big principle underlying the refrigerator is this--that a liquid when turned into gas _absorbs_ heat (thus, to convert water into steam you must feed it with heat from a fire), and that as soon as the gas loses a certain amount of its heat it reverts to liquid form. now take ammonia gas. the "spirits of hartshorn" we buy at the chemist's is water impregnated with this gas. at ordinary living temperatures the water gives out the gas, as a sniff at the bottle proves in a most effective manner. if this gas were cooled to 37â·3â° below zero it would assume a liquid state, _i.e._ that temperature marks its boiling point. similarly steam, cooled to 212â° fahr., becomes water. boiling point, therefore, merely means the temperature at which the change occurs. ammonia liquid, when gasifying, absorbs a great amount of heat from its surroundings--air, water, or whatever they may be. so that if we put a tumbler full of the liquid into a basin of water it would rob the water of enough heat to cause the formation of ice. the refrigerating machine, generally employed on ships, is one which constantly turns the ammonia liquid into gas, and the gas back into liquid. the first process produces the cold used in the freezing-rooms. the apparatus consists of three main parts:-(1) the _compressor_, for squeezing ammonia gas. (2) the _condenser_, for liquefying the gas. (3) the _evaporator_, for gasifying the liquid. the _compressor_ is a pump. the _condenser_, a tube or series of tubes outside which cold water is circulated. the _evaporator_, a spiral tube or tubes passing through a vessel full of brine. between the condenser and evaporator is a valve, which allows the liquid to pass from the one to the other in proper quantities. we can now watch the cycle of operations. the compressor sucks in a charge of very cold gas from the evaporator, and squeezes it into a fraction of its original volume, thereby heating it. the heated gas now passes into the condenser coils and, as it expands, encounters the chilling effects of the water circulating outside, which robs it of heat and causes it to liquefy. it is next slowly admitted through the expansion valve into the evaporator. here it gradually picks up the heat necessary for its gaseous form: taking it from the brine outside the coils, which has a very low freezing-point. the brine is circulated by pumps through pipes lining the walls of the freezing-room, and robs the air there of its heat until a temperature somewhat below the freezing-point of water is reached. the room is well protected by layers of charcoal or silicate cotton, which are very bad conductors of heat. how the chamber strikes a novice can be gathered from the following description of a cunard liner's refrigerating room. "it is a curious and interesting sight. it may be a hot day on deck, nearing new york, and everyone is going about in sun hats and light clothes. we descend a couple of flights of stairs, turn a key, and here is winter, sparkling in glassy frost upon the pale carcases of fowls and game, and ruddy joints of meat, crystallising the yellow apples and black grapes to the likeness of sweetmeats in a grocer's shop, gathering on the wall-pipes in scintillating coats of snow nearly an inch deep. you can make a snowball down here, if you like, and carry it up on deck to astonish the languid loungers sheltering from the sun under the protection of the promenade-deck roof. such is the modern substitute for the old-time salt-beef cask and bags of dried pease!" the larder is so near the kitchen that while below decks we may just peep into the kitchens, where a white-capped _chef_ presides over an army of assistants. inside a huge oven are dozens of joints turning round and round by the agency of an invisible electric-motor. but what most tickles the imagination is an electrical egg-boiling apparatus, which ensures the correct amount of cooking to any egg. a row of metal dippers, with perforated bottoms, is suspended over a trough of boiling water. each dipper is marked for a certain time--one minute, two, three, four, and so on. the dippers, filled with eggs, are pushed down into the water. no need to worry lest they should be "done to a bullet," for at the expiry of a minute up springs the one-minute dipper; and after each succeeding minute the others follow in due rotation. where 2,000 eggs or more are devoured daily this ingenious automatic device plays no mean part. the search-light all liners and war vessels now carry apparatus which will enable them to detect danger at night time, whether rocks or an enemy's fleet, icebergs or a water-logged derelict. on the bridge, or on some other commanding part of the vessel's structure, is a circular, glass-fronted case, backed with a mirror of peculiar shape. inside are two carbon points almost touching, across which, at the turn of a handle, leaps a shower of sparks so continuous as to form a dazzling light. the rays from the electric arc, as it is called, either pass directly through the glass lens, or are caught by the parabolic reflector and shot back through it in an almost parallel pencil of wonderful intensity, which illumines the darkness like a ray of sunshine slanting through a crack in the shutter of a room. the search-light draws its current from special dynamos, which absorb many horse-power in the case of the powerful apparatus used on warships. at a distance of several miles a page of print may be easily read by the beams of these scrutinisers of the night. the finest search-lights are to be found ashore at naval ports, where, in case of war, a sharp look-out must be kept for hostile vessels. portsmouth boasts a light of over a million candle-power, but even this is quite eclipsed by a monster light built by the schuckert company, of nuremberg, germany, which gives the effect of 816,000,000 candles. an instrument of such power would be useless on board ship, owing to the great amount of current it devours, but in a port, connected with the lighting plant of a large town, it would serve to illumine the country round for many miles. in addition to its value as an "eye," the search-light can be utilised as an "ear." ernst ruhmer, a german scientist, has discovered a method of telephoning along a beam of light from a naval projector. the amount of current passing into the arc is regulated by the pulsations of a telephone battery and transmitter. if the beam be caught by a parabolic reflector, in the focus of which is a selenium cell connected with a battery and a pair of sensitive telephone receivers, the effect of these pulsations of light is _heard_. selenium being a metal which varies its resistance to an electric circuit in proportion to the intensity of light shining upon it, any fluctuations of the search-light's beams cause electric fluctuations of equal rapidity in the telephone circuit; and since these waves arise from the vibrations of speech, the electric vibrations they cause in the selenium circuit are retransformed at the receiver into the sounds of speech. this german apparatus makes it possible to send messages nine or ten miles over a powerful projector beam. in the united states navy, and in other navies as well, night signals are flashed by the electric light. the pattern of lamp used in the united states navy is divided transversely into two compartments, the upper having a white, the lower a red, lens. four of these lamps are hung one above the other from a mast. a switch-board connected with the eight incandescent lamps in the series enables the operator to send any required signal, one letter or figure being flashed at a time. during the spanish-american war the united states fleet made great use of this simple system, which on a clear night is very effective up to distances of four miles. large arc-lamps slung on yards over the deck give great help for coaling and unloading vessels at night time. the touch of a switch lights up the deck with the brilliancy of a well-equipped railway station. the day of the "lantern, dimly burning," has long passed away from the big liner, cargo boat, and warship. wireless telegraphy instruments solitude is being rapidly banished from the earth's surface. by solitude we mean entire separation from news of the world, and the inability to get into touch with people far away. on the remote ranches of the united states, in sequestered norwegian fiords, in the folds of the eternal hills where the only other living creature is the eagle, man may still be as conversant with what is going on in china or peru as if he were living in the busy streets of a capital town. the electric wire is the magic news-bringer. wherever man can go it can go too, and also into many places besides. we must make one exception--the surface of the sea. cables rest on ocean's bed, but they would be useless if floated on its surface to act as marine telegraph offices. winds and waves would soon batter them to pieces, even if they could be moored, which in a thousand fathoms may be considered impracticable. so until a few years back the occupants of a ship were truly isolated from the time that they left port until they reached land again, except for the rare occasions when a passing vessel might give them a fragment of news. this has all been changed. stroll into the saloon of one of our large atlantic liners and you will see telegram forms lying on the tables. in the 'nineties they would have been about as useful aboard ships as a mackintosh coat in the sahara. a glance, however, at pamphlets scattered around informs you that the ship carries a marconi wireless installation, and that a marconi telegram, handed in at the ship's telegraph office, will be despatched on the wings of ether waves to the land far over the horizon. inside the cabin streams of sparks scintillate with a cracking noise, and your message shoots into space from a wire suspended on insulators from one of the mast heads. if circumstances favour, you may receive a reply from the unseen before the steamer has got out of range of the coast stations. the immense installations at poldhu, cornwall, and in newfoundland, could be used to flash the words to a ship at any point of the transatlantic journey. owing to lack of space, and consequently power, the steamer's transmitting apparatus has a limited capacity. the first shipping company to grasp the possibilities of the commercial working of the marconi system was the nord-deutscher-lloyd, whose mail steamer, _kaiser wilhelm der grosse_, was fitted in march, 1900. at the present time many of the large atlantic steamship companies carry a wireless installation as a matter of course, ranking it among necessary things. the cunard, american atlantic transport, allan, compagnie transatlantique, hamburg-american, and nord-deutscher-lloyd lines make full use of the system, as the conveniences it gives far outweigh any expense. a short time since maritime signalling was extremely limited in its range, being effected by flags, semaphores, lights, and sounds, which in stormy weather became uncertain agents, and in foggy, useless. also the operations of transmitting and receiving were so slow that many a message had to remain uncompleted. the following paragraph, which appeared in _the times_ of december 11th, 1903, is significant of the very practical value of marine wireless telegraphy. "the american steamer _kroonland_, from antwerp for new york, which, as reported yesterday, disabled her steering gear when west of the fastnet, and had to put back, arrived yesterday morning at queenstown. the saloon passengers speak in the highest terms of praise of the utility of the marconi wireless telegraphy with which the liner is fitted, and of the facility with which, when the accident occurred, the passengers were able to communicate with their friends, in england, scotland, and the continent, and even america, and get replies before the irish coast was sighted. the accident occurred on tuesday about noon, when the liner was 130 miles west of the fastnet, and communication was at once made with the marconi station at crookhaven. captain doxrud was enabled accordingly to send messages to the chief agents of the american line, at antwerp, stating the nature of the damage to the steering gear of the steamer, and that he would have to abandon the idea of prosecuting the western voyage. within an hour and a half a message was received by the captain from the agents instructing him what to do, and at once the _kroonland_ was headed for queenstown. three-fourths of the total number of the saloon passengers and a goodly number of the second cabin sent messages to their friends in various parts of the world, and replies were received even from the continent before the fastnet was sighted. seven or eight passengers telegraphed to relatives for money, and replies were received in four instances, authorising the purser to advance the amounts required, and the money was paid over in each case to the passengers." the possibility of thus communicating between vessel and land, or vessel and vessel, removes much of the anxiety attending a sea voyage. business men, for whom even a few days' want of touch with the mercantile markets may be a serious matter, can send long messages in code or otherwise instructing their agents what to do; while they can receive information to shape their actions when they reach land. the "uncommercial traveller" also is pleased and grateful on receiving a message from home. the feeling of loneliness is eliminated. the ocean has lost its right to the term bestowed by horace--_dissociabilis_, "the separator." [illustration: _photo_] [_cribb, southsea._ fixing a battle-ram the ram of a battleship being placed in position with the aid of a huge crane. the size of the ram will be appreciated from the dwarfing effect it has on that of the man perched near the lifting tackle.] steamship companies vie with one another in their efforts to keep their passengers well posted in the latest news. bulletins, or small newspapers, are issued daily during the voyage, which give, in very condensed form, accounts of events interesting to those on board. "the amount of fresh news a steamer gathers during a passage is considerable, and is greatly relished by the passengers, who are invariably ravenous for signs of the busy life they left behind, more especially when they have departed on the verge of some important event taking place; and the bulletins are eagerly sought for when it is announced that an inward-bound ship is in communication. the shipowners realise the importance and usefulness of being able to communicate with their commanders before the huge vessels enter narrow waters, and issue instructions concerning their movements. "the stations, which are placed at carefully-selected points at well-adapted distances around the coast, are connected with either the land telegraph or telephone line, or are close to a telegraph office. they are kept open night and day, as the times of the ships passing are, of course, greatly dependent on the weather encountered during the voyage. for those on shore who are anxious to greet their friends on arrival--with good or bad news, as the case may be--this arrangement enables them to be informed of the exact time of the ship's expected arrival, and they are left free to their own devices, instead of enduring long waits on draughty piers and docks--which, on a wet or windy day, are almost enough to damp the warmest and most enthusiastic welcome. "cases have occurred where a telegram, sent from the american side to an outlying english land-station two days after a ship has left, has been transmitted to an outgoing steamer, which in turn has re-transmitted it to the astonished passenger two days prior to his arrival off the english coast; and it has now become quite a common thing for competing teams on vessels many miles apart, and out of sight of each other, to arrange chess matches with each other, some of these interesting events taking two or more days to be played to a finish."[17] for naval purposes, wireless telegraphy has assumed an importance which can hardly be overestimated, as the whole efficiency of a fine fleet may depend upon a single message flashed through space. all navies are fitting instruments, the british admiralty being well to the fore. even in manoeuvres and during the execution of tactical formations the apparatus is constantly at work. the admiral gives the word, and a dozen paper tapes moving jerkily through morse machines, pass the message round the fleet. the japanese naval successes have, doubtless, been largely due to their up-to-date employment of this latest development of western electrical science. no one knows how soon the time may come when the fate of a nation may depend on the proper working of a machine covering a few square feet of a cabin table; for, rapid as has been the growth of wireless telegraphy, it is yet in its infancy. safety devices a ship is usually divided into compartments by cross bulkheads of steel. in event of a collision or damage by torpedoes or shell, the water rushing through the break can be prevented from swamping the ship by closing the bulkhead doors. messrs. j. stone and company, of deptford, have patented a system of hydraulically operated bulkhead doors, which is finding great favour among shipbuilders on account of its versatility. each door is closed by an hydraulic cylinder placed above it. the valves of the cylinder are opened automatically by a float when the water rises in the compartment, and every cylinder is also controllable independently from the bridge and other stations in the ship, and by separate hand levers alongside the bulkhead. the doors can therefore be closed collectively or individually. should it happen that, when a door has been closed, someone is imprisoned, the prisoner can open the door by depressing a lever inside the compartment, and make his escape. but the door is closed behind him by the action of the float. the transmission of power on a ship there are four power agents available on board ship, all derived directly or indirectly from the steam boilers. they are:- (1) steam. (2) high-pressure water. (3) compressed air. (4) electricity. on some ships we may find all four working side by side to drive the multifarious auxiliaries, since each has its peculiar advantages and disadvantages. at the same time, marine engineers prefer to reduce the number as far as possible, since each class of transmission needs specially trained mechanics, and introduces its special complications. let us take the four agents in order and briefly consider their value. _steam_ is so largely used in all departments of engineering that its working is better understood by the bulk of average mechanics than hydraulic power, compressed air, or electricity. but for marine work it has very serious drawbacks, especially on a war vessel. imagine a ship which contains a network of steam-pipes running from end to end, and from side to side. the pipes must, on account of the many obstacles they encounter, twist and turn about in a manner which might be avoided on land, where room is more available. every bend means friction and loss of power. again, the condensation of steam in long pipes is notorious. even if they are well jacketed, a great deal of heat will radiate from the ducts into the below-deck atmosphere, which is generally too close and hot to be pleasant without any such further warming. so that, while power is lost, discomfort increases, with a decided lowering of human efficiency. we must not forget, either, the risk attending the presence of a steam-pipe. were it broken, by accident or in a naval engagement, a great loss of life might result, or, at least, the abandonment of all neighbouring machinery. for these reasons there is, therefore, a tendency to abolish the direct use of steam in the auxiliary machinery of a modern vessel. _high-pressure water_ is free from heating and danger troubles, and consequently is used for much heavy work, such as training guns, raising ashes and ammunition, and steering. one of its great advantages is its inelasticity, which prevents the overrunning of gear worked by it. water, being incompressible, gives a "positive" drive; thus, if the pump delivers a pint at each stroke in the engine-room a pint must pass into the motor, assuming that all joints are tight, and the work due from the passage of one pint is done. air and steam--and electricity too, if not very delicately controlled--are apt to work in fits and starts when operating against varying resistance, and "run away" from the engineer. an objection to hydraulic power is, that all leakage from the system must be replaced by fresh water manufactured on board, which, as we have seen, is no easy task. _compressed air_, like steam, may cause explosions; but when it escapes in small quantities only it has a beneficial effect in cooling and freshening the air below decks. the exhaust from an air-driven motor is welcome for the same reason, that it aids ventilation. on a fighting ship it is of the utmost importance that the _personnel_ should be in good physical condition; and when the battle-hatches have been battened down for an engagement any supply of fresh oxygen means an increased "staying power" for officers and crew. poisoned air brings mental slackness, and weakening of resolve; so that if the motive power of heavy machinery can be made to do a second duty, so much the better for all concerned. compressed air also proves useful as a water-excluder. if a vessel contain, as it should, a number of water-tight compartments, any water rushing into one of these can be expelled by injecting air until the pressure inside is equal to that of the draught of water of the vessel outside. on land compressed-air installations include reservoirs of large size in which air can be stored till needed, and which take the place of the accumulator used with hydraulic power. on shipboard want of space reduces such reservoirs to minimum dimensions, so that the compressors must squirt their air almost directly into the cylinders which do the work. when the load, or work, is constantly varying, this direct drive proves somewhat of a nuisance, since the compressors, if worked continuously at their maximum capacity, must waste large quantities of air, while if run spasmodically, as occasion demands, they require much more attention. it is therefore considered advisable by some marine engineers to make compressed air perform as many functions as possible when it is present on a vessel. the united states monitor _terror_ is an instance of a warship which depends on this agency for working her guns and turrets, handling ammunition, and--a somewhat unusual practice--controlling the helm. the last operation is performed by two large cylinders placed face to face athwart the ship. they have a common piston-rod, in the middle of which is a slot for the tiller to pass through. air is admitted to the cylinders by a valve which is controlled by wires passing over a train of wheels from different stations on the ship. an ingenious device automatically prevents the tiller from moving over too fast, and also helps to lessen the shocks given to the rudder by a heavy sea. we now come to _electricity_, the fourth and most modern form of transmission. its chief recommendation is that the wires through which it flows lend themselves readily to a tortuous course without in any way throttling the passage of power. and as every ship must carry a generating plant for lighting purposes, the same staff will serve to tend a second plant for auxiliary machinery. electric motors work with practically no vibration, are light for their power, and can be very easily controlled from a distance. they therefore enjoy increasing favour; and are found in deck-winches, anchor-capstans, ammunition hoists, ventilation blowers, and cranes. they also control the movements of gun-turrets, having been found most suitable for this work. if the current were to get loose in a ship it would undoubtedly cause more damage than an escape of compressed air or water. electricity, even when every known means of keeping it within bounds has been tried, is suspected of causing deterioration to the metalwork of ships. but these disadvantages are not serious enough to hamper the progress of electrical science as applied to marine engineering; and the undoubted economy of the electric motor, its noiselessness, its manageableness, and comparatively small size will, no doubt, in the future lead to its much more extensive use on board our floating palaces and floating forts. footnotes: [16] f. m. bennett, in the journal of the american society of naval engineers. [17] charles v. daly, in _the magazine of commerce_. chapter xiii "the nurse of the navy" just as a navy requires floating distilleries, floating coal stores and floating docks, so does it find very important uses for a floating workshop, which can accompany a fleet to sea and execute such repairs as might otherwise entail the return of a ship to port. the british navy has a valuable ally of this kind in the torpedo depã´t ship _vulcan_, which contains so much machinery, in addition to the "auxiliaries" already described, that a short account of this vessel will be interesting. the _vulcan_, known as "the nurse of the navy," was launched in 1889. she measures 350 feet in length, 58 feet in beam, and has a displacement of 6,830 tons. her bunkers, of which there are twenty-one, hold 1,000 tons of coal, independently of an extra 300 tons which can be stowed in other neighbouring compartments. when fully coaled she can cruise for 7,000 miles at a speed of 10 knots; or travel at first-class cruiser speed for shorter distances. the most striking objects on the _vulcan_ are two huge hydraulic cranes, placed almost amidships abreast of one another. they have a total height of 65 feet, and "overhang" 35 feet, so as to be able to lift boats when the torpedo-nets are out and the sides of the vessel cannot be approached. the feet of the cranes sink 30 feet through the ship to secure rigidity, and the upper deck, which bears most of the strain, is strongly reinforced. inside the pillar of each crane is the lifting machinery, an hydraulic ram 17-1/2 inches in diameter and of 10-foot stroke. by means of fourfold pulleys the lift is increased to 40 feet. when working under the full pressure of 1,000 lbs. to the square inch, the cranes have a hoisting power of twenty tons. in addition to the main ram there is a much smaller one, the function of which is to keep the "slings" (or cables by which the boat is hoisted) taut after a boat has been hooked until the actual moment of lifting comes. but for this arrangement there would be a danger of the slings slackening as the boat rises and falls in a seaway. the small ram controls the larger, and the latter cannot come into action until its auxiliary has tightened up the slings, so that no dangerous jerk can occur when the hoisting begins. the cranes are revolved by two sets of hydraulic rams, which operate chains passing round drums at the feet of the cranes, and turn them through three-quarters of a circle. on the _vulcan's_ deck lie six torpedo boats and three despatch boats. the former are 60 feet long, and can attain a speed of 16 knots an hour. when an enemy is sighted these would be sent off to worry the hostile vessels with their deadly torpedoes, and on their return would be quickly picked up and restored to their berths, ready for further use. [illustration: _photo cribb._ a 12-inch gun being lowered into its place in the turret of a warship by a gigantic sheer-leg crane, one leg of which is partly visible on the left of the picture.] the cranes also serve to lift on board heavy pieces of machinery from other vessels for repair. down below decks is the workshop, wherein "jobs" are done on the high seas. it has quite a respectable equipment: five lathes, ranging from 15 feet to 3-1/2 feet in length; drilling, planing, slotting, shaping, punching machines; a carpenter's bench; fitters' benches; and a furnace for melting steel. there is also a blacksmith's shop with an hydraulic forging press and a forge blown by machinery; not to mention a large array of tools of all kinds. special engines are installed to operate the repairs department. the _vulcan_ also carries search-lights of 25,000 candle-power; bilge pumps which will deliver over 5,000 tons of water per hour; two sets of engines for supplying the hydraulic machinery; air-compressing engines to feed the whitehead torpedoes; a distilling plant; and last, but by no means least, main engines of 12,000 h.p. drawing steam from four huge cylindrical boilers 17 feet long and 14 feet in diameter. altogether, the _vulcan_ is a very complete floating workshop, sufficiently speedy to keep up with a fleet, and even to do scouting work. her guns and her torpedo craft would render her a very troublesome customer in a fight, though, being practically unarmoured, she would keep as clear of the conflict as possible, acting on the offensive through the proxy of her "hornets." she constitutes the first of a type of vessel which has been suggested by experts, viz. one of high speed and unarmoured, but capable of carrying a swarm of torpedo boats which could be launched in pursuit of the foe. even if 50 per cent. of the craft were destroyed, the price would be small if a single torpedo were successfully fired at a battleship. the naval motor boat, to which reference has already been made, would just "fill the bill" for such a cruiser; and in the event of a score of them being dropped into the water at a critical moment, they might easily turn the scale in favour of their side. chapter xiv the mechanism of diving diving being a profession which can be carried on in its simplest form with the simplest possible apparatus--merely a rope and a stone--its history reaches back into the dim and inexplorable past. we may well believe that the first man who explored the depths of the sea for treasure lived as long ago as the first seeker for minerals in the bosom of the earth. even when we come to the various appliances which have been gradually developed in the course of centuries, our records are very imperfect. alexander the great is said to have descended in a machine which kept him dry, while he sought for fresh worlds to conquer below the waves. aristotle mentions a device enabling men to remain some time under water. this is all the information, and a very meagre total, too, that we get from classical times. stepping across 1,500 years we reach the thirteenth century, about the middle of which roger bacon is said to have invented the diving-bell. but like some other discoveries attributed to that middle-age physicist, the authenticity of this rests on very slender foundations. in a book published early in the sixteenth century there appears an illustration of a diver wearing a cap or helmet, to which is attached a leather tube floated on the surface of the water by an inflated bag. this is evidently the diving dress in its crudest form; and when we read how, in 1538, two greeks made a submarine trip under a huge inverted chamber, which kept them dry, in the presence of the great emperor charles v. and some 12,000 spectators, we recognise the diving-bell, now so well known. the latter device did not reach a really practical form till 1717, when dr. halley, a member of the royal society, built a bell of wood lined with lead. the divers were supplied with air by having casks-full lowered to them as required. to quote his own words: "to supply air to this bell under water, i caused a couple of barrels of about thirty gallons each to be cased with lead, so as to sink empty, each of them having a bunghole in its lowest parts to let in the water, as the air in them condensed on their descent, and to let it out again when they were drawn up full from below. and to a hole in the uppermost parts of these barrels i fixed a leathern hose, long enough to fall below the bunghole, being kept down by a weight appended, so that the air in the upper parts of the barrels could not escape, unless the lower ends of these hose were first lifted up. the air-barrels being thus prepared, i fitted them with tackle proper to make them rise and fall alternately, after the manner of two buckets in a well; and in their descent they were directed by lines fastened to the under edge of the bell, which passed through rings on both sides of the leathern hose in each barrel, so that, sliding down by these lines, they came readily to the hand of a man, who stood on purpose to receive them, and to take up the ends of the hose into the bell. through these hose, as soon as their ends came above the surface of the water in the barrels, all the air that was included in the upper parts of them was blown with great force into the bell, whilst the water entered at the bungholes below and filled them, and as soon as the air of one barrel had been thus received, upon a signal given that was drawn up, and at the same time the other descended, and by an alternate succession, provided air so quick and in such plenty that i myself have been one of five who have been together at the bottom, in nine to ten fathoms water, for above an hour and a half at a time, without any sort of ill-consequence, and i might have continued there so long as i pleased for anything that appeared to the contrary." after referring to the fact that, when the sea was clear and the sun shining, he could see to read or write in the submerged bell, thanks to a glass window in it, the doctor goes on to say: "this i take to be an invention applicable to various uses, such as fishing for pearls, diving for coral or sponges and the like, in far greater depths than has hitherto been thought possible; also for the fitting and placing of the foundations of moles, bridges, etc., in rocky bottoms, and for cleaning and scrubbing ships' bottoms when foul, in calm weather at sea. i shall only intimate that, _by an additional contrivance_, i have found it not impracticable for a diver to go out of an engine to a good distance from it, the air being conveyed to him with a continued stream by small flexible pipes, which pipes may serve as a clue to direct him back again when he would return to the bell." we have italicised certain words to draw attention to the fact that dr. halley had invented not only the diving bell, but also the diving dress. though he foresaw practically all the uses to which diving mechanism could be put, the absence of a means for forcing air _under pressure_ into the bell or dress greatly limited the utility of his contrivances, since the deeper they sank below the water the further would the latter rise inside them. it was left for john smeaton, of eddystone lighthouse fame, to introduce the _air-pump_ as an auxiliary, which, by making the pressure of the air inside the bell equal to that of the water outside, kept the bell quite free of water. smeaton replaced halley's tub by a square, solid cast-iron box, 50 cwt. in weight, large enough to accommodate two men at a time. the modern bell is merely an enlarged edition of this type, furnished with telephones, electric lamps, and, in some cases, with a special air-lock, into which the men may pass when the bell is raised. the pressure in the air-lock is very gradually decreased after the bell has reached the surface, if work has been conducted at great depths, so that the evil effects sometimes attending a sudden change of pressure on the body may be avoided. diving bells are very useful for laying submarine masonry, usually consisting of huge stone blocks set in hydraulic cement. helmet divers explore and prepare the surface on which the blocks are to be placed. then the bell, slung either from a crane on the masonry already built above water-level, or from a specially fitted barge, comes into action. the block is lowered by its own crane on to the bottom. the bell descends upon it and the crew seize it with tackle suspended inside the bell. instructions are sent up as to the direction in which the bell should be moved with its burden, and as soon as the exact spot has been reached the signal for lowering is given, and the stone settles on to the cement laid ready for it. the modern diver is not sent out from a bell, but has his separate and independent apparatus. the first practical diving helmet was that of kleingert, a german. this enclosed the diver as far as the waist, and constituted a small diving bell, since the bottom was open for the escape of vitiated air. twenty years later, or just a century after the invention of halley's bell, augustus siebe, the founder of the present great london firm of siebe, gorman, and company, produced a more convenient "open" dress, consisting of a copper helmet and shoulder-plate in one piece, attached to a waterproof jacket reaching to the hips. the disadvantage of the open dress was, that the diver had to maintain an almost upright position, or the water would have invaded his helmet. mr. siebe therefore added a necessary improvement, and extended the dress to the feet, giving his diver a "close" protection from the water. we may pass over the gradual development of the "close" dress and glance at the most up-to-date equipment in which the "toilers of the deep" explore the bed of old ocean. the dress--legging, body, and sleeves--is all in one piece, with a large-enough opening at the shoulders for the body to pass through. the helmet, with front and side windows, is attached by a "bayonet joint" to the shoulder-plate, itself made fast to the upper edge of the dress by screws which press a metal ring against the lower edge of the plate so as to pinch the edge of the dress. [illustration: _photo cribb._ the diver at work note the telephone attachment, the wires of which are embedded in the life-line held by the bluejacket on the left. by means of the telephone the diver can give and receive full instructions about his work.] at the back are an inlet and an outlet valve. between the front and a side window is the transmitter of a loud-sounding telephone, and in the crown the receiver and the button of an electric bell. the telephone wires, and also the wires for a powerful electric light, working on a ball-and-socket joint in front of the dress, are embedded into the life-line. the air-tube, of canvas and rubber, has a stiffening of wire to prevent its being throttled on coming into contact with any object. a pair of weighted boots, each scaling 17 lbs., two 40-lb. lead weights slung over the shoulder, and a knife worn at the waist-belt, complete the outfit of the diver, which, not including the several layers of underclothing necessary to exclude the cold found at great depths, totals nearly 140 lbs. of this the copper helmet accounts for 36 lbs. on the surface are the air-pumps, which may be of several types--single-cylinder, double-acting; double-cylinder, double-acting; or three or four cylinder, single-acting--according to the nature of the work. all patterns are so constructed that the valves may be easily removed and examined. the pressure on a diver increases in the ratio of about 4-1/4 lbs. for every ten feet he descends below the surface. a novice experiences severe pains in the ears and eyes at a few fathoms' depth, which, however, pass off when the pressures both inside and outside of the various organs have become equalised. on rising to the surface again the pains recur, since the external pressure on the body falls more quickly than the internal. the rule for all divers, therefore, is "slow down, slow up." men of good constitution and resourcefulness are needed for the profession of diving. only a few can work at extreme depths, though an old hand is able to remain for several hours at a time in sixty feet of water. the record depth reached by a diver is claimed by james hooper, who, when removing the cargo of the _cape horn_, wrecked off the coast of south america, made seven descents to 201 feet, one of which lasted forty-two minutes. in spite of the dangers and inconveniences attached to his calling, the diver finds in it compensations, and even fascinations, which outweigh its disadvantages. the pay is good--â£1 to â£2 a day--and in deep-sea salvage he often gets a substantial percentage of all the treasure recovered, the percentage rising as the depth increases. thus the diver alexander lambert, who performed some plucky feats during the driving of the severn tunnel,[18] received â£4,000 for the recovery of â£70,000 worth of gold from the _alphonso xii._, sunk off grand canary. divers ridyard and penk recovered â£50,000 from the _hamilla mitchell_, which lay in 160 feet of water off shanghai, after nearly being captured by chinese pirates; and we could add many other instances in which treasure has been rescued from the maw of the sea. the most useful sphere for a diver is undoubtedly connected with the harbour work and the cleaning of ships' bottoms. for the latter purpose every large warship in the british navy carries at least one diver. after ships have been long in the water barnacles and marine growths accumulate on the below-water plates in such quantities as to seriously diminish the ship's speed, which means a great waste of fuel, and would entail a loss of efficiency in case of war breaking out. armed with the proper tools, a gang of divers will soon clean the "foul bottom," at a much smaller cost of time and money than would be incurred by dry-docking the vessel. the navy has at portsmouth, sheerness, and devonport schools where diving is taught to picked men, the depth in which they work being gradually increased to 120 feet. messrs. siebe and gorman employ hundreds of divers in all parts of the world, on all kinds of submarine work, and they are able to boast that never has a defect in their apparatus been responsible for a single death. this is due both to the very careful tests to which every article is subjected before it leaves their works, and also to the thorough training given to their employã©s. in the sponge and pearl-fishing industries the diving dress is gradually ousting the unaided powers of the naked diver. one man equipped with a standard dress can do the work of twenty natural divers, and do it more efficiently, as he can pick and choose his material. this chapter may conclude with a reference to the apparatus now used in exploring or rescue work in mines, where deadly fumes have overcome the miners. it consists of an air-tight mask connected by tubes to a chamber full of oxygen and to a bag containing materials which absorb the carbonic acid of exhaled air. the wearer uses the same air over and over again, and is able to remain independent of the outer atmosphere for more than an hour. the apparatus is also useful for firemen when they have to pass through thick smoke. footnote: [18] vide _the romance of modern engineering_, p. 212. chapter xv apparatus for raising sunken ships and treasure it is somewhat curious that, while the sciences connected with the building of ships have progressed with giant strides, little attention has been paid to the art of raising vessels which have found watery graves in comparatively shallow depths. the total shipping losses of a single year make terrible reading, since they represent the extinction of many brave sailors and the disappearance of huge masses of the world's wealth. a life lost is lost for ever, but cargoes can be recovered if not sunk in water deeper than 180 feet. yet with all our modern machinery the percentage of vessels raised from even shallow depths is small. there are practically only two methods of raising a foundered ship: first, to caulk up all leaks and pump her dry; and secondly, to pass cables under her, and lift her bodily by the aid of pontoons, or "camels." the second method is that more generally used, especially in the estuaries of big rivers where there is a considerable tide. the pontoons, having a united displacement greater than that of the vessel to be raised, are brought over her at low tide. divers pass under her bottom huge steel cables, which are attached to the "camels." as the tide flows the pontoons sink until they have displaced a weight of water equal to that of the vessel, and then they begin to raise her, and can be towed into shallower water, to repeat the process if necessary next tide. as soon as the deck is above water the vessel may be pumped empty, when all leaks have been stopped. in water where there is no tide the natural lift must be replaced by artificial power. under such circumstances the salvage firms use lighters provided with powerful winches, each able to lift up to 800 tons on huge steel cables nearly a foot in diameter. the winches can be moved across a lighter, the cables falling perpendicularly, through transverse wells almost dividing the lighter into separate lengths, so as to get a direct pull. if the wreck has only half the displacement of the lighters, the cables can be passed over rollers on the inner edges of the pontoons, the weight of the raising vessel being counteracted by water let into compartments in the outer side of the pontoons. there are ten great salvage companies in the british isles and europe. the best equipped of these is the neptune company, of stockholm, which has raised 1,500 vessels, worth over â£5,000,000 sterling even in their damaged condition, among them the ill-fated submarine "a1." yet this total represents but a small part of the wealth that has gone to the bottom within a short distance of our coasts. turning from the salvage of wrecks to the salvage of precious metal and bulky objects that are known to strew the sea-floor in many places, we must notice the hydroscope, the invention of cavaliere pino, an italian. in 1702 there sank in vigo bay, on the north-west coast of spain, twenty-five galleons laden with treasure from america, as the result of an attack by english and dutch men-of-war. gold representing â£28,000,000 was on those vessels. down it went to the bottom, and there it is still. so rich a prize has naturally not failed to attract daring spirits, among whom was giuseppe pino. this inventor has produced many devices, the most notable among them the hydroscope, which may best be described as a huge telescope for peering into the depths of the sea. a large circular tank floats on the top of the water. from the centre of its bottom hangs a series of tubes fitting one into the other, so that the whole series can be shortened or lengthened at will. through the tubes a man can descend to the chamber at their lower extremity, in the sides of which are twelve lenses specially made by saint gobain, of paris, which act as submarine telescopes. pino's hydroscope has been at work for some time in vigo bay, its operations closely watched by a spanish war vessel, which will exact 20 per cent. of all treasure recovered. while the hydroscope acts as an eye, the lifting of an object is accomplished by attaching to it large canvas bags furnished with air-tight internal rubber bladders. these have air pumped into them till its pressure overcomes that of the water outside, and the bag then rises like a cork, carrying its load with it. an "elevator"--nine sacks fixed to one frame--will raise twenty-five to thirty tons. so far cavaliere pino has salvaged old spanish guns, cannon-balls, and pieces of valuable old wood; and presently he may alight on the specie which is the main object of his search. another spanish wreck, the _florida_, which was a unit of the spanish armada, and sank in tobermory bay, the isle of mull, has many times been attacked by divers. the last attempt made to recover the treasure which that ill-fated vessel was reputed to bear is that of the steam lighter _sealight_, which employed a very powerful sand pump to suck up any objects which it might encounter on the sea-bottom. many interesting relics have been raised by the pumps and attendant divers--coins, bones, jewels, timbers, cannon, muskets, pistols, swords, and a compass, which is so constructed that pressure on the top causes the legs to spread. one of the cannon, fifty-four inches long, has a separate powder chamber, the shot and wad still in the gun, and traces of powder in the chamber. it is curious that what we usually consider so modern an invention as the breech-loading cannon should be found side by side with stone balls. the heavier objects were, of course, raised by divers. in this quest also the treasure deposit has not yet been tapped. chapter xvi the handling of grain the elevator--the suction pneumatic grain-lifter--the pneumatic blast grain-lifter--the combined system the elevator on or near the quays of our large seaports, london, liverpool, manchester, bristol, hull, leith, dublin, may be seen huge buildings of severe and ugly outline, utterly devoid of any attempt at decoration. yet we should view them with respect, for they are to the inhabitants of the british isles what the inland granaries of egypt were to the dwellers by the nile in the time of joseph. could we strip off the roofs and walls of these structures, we should see vast bins full of wheat, or spacious floors deeply strewn with the material for countless loaves. the grain warehouses of britain--the americans would term them "elevators"--have a total capacity of 10,000,000 quarters. multiply those figures by eight, and you have the number of bushels, each of which will yield the flour for about forty 2-lb. loaves. in these granaries is stored the grain which comes from abroad. with the opening up of new lands in north and south america, and the exploitation of the great wheat-growing steppes of russia, english agriculture has declined, and we are content to import five-sixths of our breadstuffs, and an even larger proportion of grain foods for domestic animals. it arrives from the united states, india, russia, argentina, canada, and australia in vessels often built specially for grain transport; and as it cannot be immediately distributed, must be stored in bulk in properly designed buildings. these contain either many storeys, over which the grain is spread to get rid of superfluous moisture which might cause dangerous heating; or huge bins, or "silos," in which it can be kept from contact with the air. experiments have proved that wheat is more successfully preserved if the air is excluded than if left in the open, provided that it is dry. the ancient egyptians used brick granaries, filled from the top, and tapped at the bottom, in which, to judge by the account of a grievous famine given in the book of genesis, their wheat was preserved for at least seven years. during last century the silo fell into disrepute; but now we have gone back to the egyptian plan of closed bins, which are constructed of wood, brick, ferro-concrete, or iron, and are of square, hexagonal, or round section. they are set close together, many under one roof, to economise space; as many as 2,985,000 bushels being provided for in the largest english storehouse. such vast quantities of grain require well-devised machinery for their transport from ship to bin or floor, weighing, clearing, and for their transference to barges, coasting vessels, or railway trucks. the alexander grain warehouse of liverpool may be taken as a typical example of a well-equipped silo granary. it measures 240 by 172 feet, and contains 250 hexagonal bins of brickwork, each 80 feet deep and 12 feet in diameter. the grain is lifted from barges by four elevators placed at intervals along the edge of the quay. the elevator is a wooden case, 40 or 50 feet high, in which an endless band furnished with buckets travels over two rollers placed at the top and bottom. these are let down into the hold and scoop up the grain at the rate of from 75 to 150 tons per hour, according to their size. as soon as a bucket reaches the top roller it empties its charge into a spout, which delivers the grain into a bin, whence it is lifted again 32 feet by a second elevator to a bin from which it flows by gravity to a weighing hopper beneath; and as soon as two tons has collected, the contents are emptied automatically into a distributing hopper. after all this, the grain still has a long journey before it; for it is now shot out on to an endless, flat conveyer belt moving at a rate of 9 to 10 feet per second. it is carried horizontally by this for some distance along the quay, and falls on to a second belt moving at right angles to the first, which whisks it off to the receiving elevators of the storehouse. once more it is lifted, this time 132 feet, to the top floor of the building, and dropped on to a third belt, which runs over a movable throwing-off carriage. this can be placed at any point of the belt's travel, to transfer the grain to any of the spouts leading to the 250 bins. here it rests for a time. when needed for the market it flows out at the bottom of a bin on to belts leading to delivery elevators, from which it may be either passed back to a storage bin after being well aired, or shot into wagons or vessels. from first to last a single grain may have to travel three miles between the ship and the truck without being touched once by a human hand. the vertical transport of grain is generally effected by an endless belt, to which buckets are attached at short intervals. the grain, fed to the buckets either by hand or by mechanical means, is scooped up, whirled aloft, and when it has passed the topmost point of its travel, and just as the bucket is commencing the descent, it flies by centrifugal force into a hopper which guides it to the travelling belt, as already described. of late years, however, much attention has been paid to pneumatic methods of elevating, by which a cargo is transferred from ship to storehouse, or from ship to ship, through flexible tubes, the motive power being either the pressure of atmospheric air rushing in to fill a vacuum, or high-pressure air which blows the grain through the tube in much the same way as a steam injector forces water into a boiler. sometimes both systems are used in combination. we will first consider these methods separately. the suction pneumatic grain-lifter is the invention of mr. fred e. duckham, engineer of the millwall docks, london. the ships in which grain is brought to england often contain a "mixed" cargo as well; and that the unloading of this may proceed simultaneously with the moving of the wheat it is necessary to keep the hatches clear. as long as the grain is directly under a hatchway, a bucket elevator can reach it; but all that is not so conveniently situated must be brought within range of the buckets. this means a large bill for labour, even if machinery is employed to help the "trimming." mr. duckham therefore designed an elevator which could easily reach any corner of a ship's interior. the principal parts are a large cylindrical air-tight tank, an engine to exhaust air from the same, and long hoses, armoured inside with a steel lining, connected at one end to the tank, and furnished at the other with a nozzle. these hoses extend from the receiving tank to the grain, which, when the air has been exhausted to five or six pounds to the square inch, flies up the tubes into the tank. at the bottom of the tank are ingenious air-locks, to allow the grain to pass into a bin below without admitting air to spoil the vacuum. the locks are automatic, and as soon as a certain quantity of grain has collected, tip sideways, closing the port through which it flowed, and allowing it to drop through a hinged door. two locks are attached together, the one discharging while the other is filling. an elevator of this kind will shift 150 tons or more an hour. mr. duckham claims for his invention that it has no limit in capacity. it is practically independent of everything but its own steam power; and the labour of one man suffices to keep its flexible suckers buried in grain. no corner is inaccessible to the nozzle. the pipes occupy only a very small part of the hatchway. they can be set to work immediately a vessel comes alongside. as many as a quarter of a million bushels are handled daily by one of these machines. the pneumatic elevator is often installed on a floating base, so that it may be moved about in a dock. the pneumatic blast grain-lifter differs from the system just described in that the grain is _driven_ through the pipes or hoses by air compressed to several pounds above atmospheric pressure. a small tube attached to the main hose conveys compressed air to the nozzle through which grain enters the tube. the nozzle consists of a short length of metal piping which is buried in the grain. one half of it is encased by a jacket into which the compressed air rushes. as the air escapes at high speed past the inner end of the piping into the main hose, it causes a vacuum in the piping and draws in grain, which is shot up the hose by the pressure behind it. as already remarked, the action of this pneumatic elevator is similar to that of a steam injector. the combined system under some conditions it is found convenient to employ both suction and blast in combination: suction to draw the grain from a vessel's hold into elevators, from which it is transferred to the warehouse by blast. special boats are built for this work, _e.g._ the _garryowen_, which has on board suction plant for transferring grain from a ship to barges, and also blowing apparatus for elevating it into storehouses or into another ship. the _garryowen_ has the hull and engines of an ordinary screw steamer, so that it can ply up and down the shannon and partly unload a vessel to reduce its draught sufficiently to allow it to reach limerick docks. floating elevators of this kind are able to handle upwards of 150 tons of grain per hour. chapter xvii mechanical transporters and conveyers mechanical conveyers--ropeways--cableways--telpherage--coaling warships at sea a man carrying a sack of coal over a plank laid from the wharf to the ship's side, a bricklayer's labourer moving slowly up a ladder with his hod of mortar--these illustrate the most primitive methods of shifting material from one spot to another. when the wheelbarrow is used in the one case, and a rope and pulley in the other, an advance has been made, but the effort is still great in proportion to the work accomplished; and were such processes universal in the great industries connected with mining and manufacture, the labour bill would be ruinous. the development of methods of transportation has gone on simultaneously with the improvement of machinery of all kinds. to be successful, an industry must be conducted economically throughout. thus, to follow the history of wheat from the time that it is selected for sowing till it forms a loaf, we see it mechanically placed in the ground, mechanically reaped, threshed, and dressed, mechanically hauled to the elevator, mechanically transferred to the bins of the same, mechanically shot into trucks or a ship, mechanically raised into a flour-mill, where it is cleaned, ground, weighed, packed, and trucked by machinery, mechanically mixed with yeast and baked, and possibly distributed by mechanically operated vehicles. as a result we get a 2-lb. loaf for less than three-pence. anyone who thinks that the price is regulated merely by the _amount_ of wheat grown is greatly mistaken, for the cheapness of handling and transportation conduces at least equally to the cheapness of the finished article. the same may be said of the metal articles with which every house is furnished. a fender would be dearer than it is were not the iron ore cheaply transported from mine to rail, from rail to the smelting furnace, from the ground to the top of the furnace. in short, to whatever industry we look, in which large quantities of raw or finished material have to be moved, stored, and distributed, the mechanical conveyer has supplanted human labour to such an extent that in lack of such devices we can scarcely conceive how the industry could be conducted without either proving ruinous to the people who control it or enhancing prices enormously. the types of elevators and conveyers now commonly used in all parts of the world are so numerous that in the following pages only some selected examples can be treated. speaking broadly, the mechanical transporter can be classified under two main heads--(1) those which handle materials _continuously_, as in the case of belt conveyers, pneumatic grain dischargers, etc.; and (2) those which work _intermittently_, such as the telpher, which carries skips on an aerial ropeway. the first class are most useful for short distances; the latter for longer distances, or where the conditions are such that the material must be transported in large masses at a time by powerful grabs. some transporters work only in a vertical direction; others only horizontally; while a third large section combine the two movements. again, while some are mere conveyers of material shot into or attached to them, others scoop up their loads as they move. the distinctions in detail are numerous, and will be brought out in the chapters devoted to the various types. mechanical conveyers we have already noticed band conveyers in connection with the transportation of grain. they are also used for handling coal, coke, diamond "dirt," gold ore, and other minerals, and for moving filled sacks. the belts are sometimes made of rubber or of balata faced with rubber on the upper surface, which has to stand most of the wear and tear--sometimes of metal plates joined together by hinges at the ends. a modification of the belt is the continuous trough, with sloping or vertical sides. this is built of open-ended sections jointed so that they may pass round the terminal rollers. while travelling in a straight line the sides of the sections touch, preventing any escape of the material carried, but at the rollers the ends open in a v-shape. another form of conveyer has a stationary trough through which the substance to be handled is pulled along by plates attached to cables or endless chains running on rollers. or the moving agency may be plates dragged backwards and forwards periodically, the plates hanging in one direction only, like flap valves, so as to pass over the material during the backward stroke, and bite it during the forward stroke. the vibrating conveyer is a trough which moves bodily backwards and forwards on hinged supports, the oscillation gradually shaking its contents along. as no dragging or pushing plates are here needed, this form of conveyer is very suitable for materials which are liable to be injured by rough treatment. ropeways a certain person on asking what was the distance from x to y, received the reply, "it is ten miles as the crow flies." the country being mountainous, the answer did not satisfy him, and he said, "oh! but you see, i am _not_ a crow." engineers laying out a railway can sympathise with this gentleman, for they know from sad experience that places only a few miles apart in a straight line often require a track many miles long to connect them if gradients are to be kept moderate. now a locomotive, a railway carriage, or a goods truck is very heavy, and must run on the firm bosom of mother earth. but for comparatively light bodies a path may be made which much more nearly resembles the proverbial flight of the crow, or, as our american cousins would say, a bee-line. if you have travelled in norway and switzerland you probably have noticed here and there steel wire ropes spanning a torrent or hanging across a narrow valley. over these ropes the peasants shoot their hay crops or wood faggots from the mountain-side to their homes, or to a point near a road where the material can be transferred to carts. adventurous folk even dare to entrust their own bodies to the seemingly frail steel thread, using a brake to control the velocity of the descent. the history of the modern ropeway and cableway dates from the 'thirties, when the invention of wire rope supplied a flexible carrying agent of great strength in proportion to its weight, and of sufficient hardness to resist much wear and tear, and too inelastic to stretch under repeated stresses. to prevent confusion, we may at once state that a ropeway is an aerial track used only for the _conveyance_ of material; whereas a cableway hoists as well as conveys. a further distinction--though it does not hold good in all cases--may be seen in the fact that, while cableways are of a single span, ropeways are carried for distances ranging up to twenty miles over towers or poles placed at convenient intervals. ropeways fall into two main classes: first, those in which the rope supporting the weight of the thing carried moves; secondly, those in which the carrier rope is stationary, and the skips, or tubs, etc., are dragged along it by a second rope. the moving rope system is best adapted for light loads, not exceeding six hundredweight or so; but over the second class bodies scaling five or six tons have often been moved. in both systems the line may be single or double, according to the amount of traffic which it has to accommodate. the chief advantage of the double ropeway is that it permits a continuous service and an economy of power, since in cases where material has to be delivered at a lower level than the point at which it is shipped, the weight of the descending full trucks can be utilised to haul up ascending empty trucks. spans of 2,000 feet or two-fifths of a mile are not at all unusual in very rough country where the spots on which supports can be erected are few and far between; but engineers naturally endeavour to make the span as short as possible, in order to be able to use a small size of rope. glancing at some interesting ropeways, we may first notice that used in the construction of the new beachy head lighthouse, recently erected on the foreshore below the head on which the original structure stands. for the sake of convenience, the workshops, storage yards, etc., were placed on the cliffs, 400 feet above the sea and some 800 feet in a direct line from the site of the new lighthouse. between the cliff summit and a staging in the sea were stretched two huge steel ropes, the one, six inches in circumference, for the track over which the four-ton blocks of granite used in the building, machinery, tools, etc., should be lowered; the other, 5-1/2 inches in circumference, for the return of the carriers and trucks containing workmen. the ropes had a breaking strain of 120 and 100 tons respectively; that is to say, if put in an hydraulic testing machine they would have withstood pulls equal to those exerted by masses of these weights hung on them. their top ends were anchored in solid rock; their lower ends to a mass of concrete built up in the chalk forming the sea-bottom. when a granite block was attached to the carrier travelling on the rope, its weight was gradually transferred to the rope by lowering the truck on which it had arrived until the latter was clear of the block. as soon as the stone started on its journey the truck was lifted again to the level of the rails and trundled away. a brakesman, stationed at a point whence he could command the whole ropeway, had under his hand the brake wheels regulating the movements of the trailing ropes for lowering and hauling on the two tracks. another interesting ropeway is that at hong-kong, which transports the workmen in a sugar factory on the low, fever-breeding levels to their homes in the hills where they may sleep secure from noxious microbes. the carriers accommodate six men at a time, and move at the rate of eight miles an hour. the sensation of being hauled through mid-air must be an exhilarating one, and some of us would not mind changing places with the workmen for a trip or two, reassured by the fact that this ropeway has been in operation for several years without any accident. in southern india, in the anamalai hills, a ropeway is used for delivering sawn timber from the forests to a point 1-1/4 miles below. prior to the establishment of this ropeway the logs were sent down a circuitous mountain track on bullock carts. its erection was a matter of great difficulty, on account of the steep gradients and the dense and unhealthy forest through which a path had to be cut; not to mention the dragging uphill of a cable which, with the reel on which it was wound, weighed four tons. for this last operation the combined strength of nine elephants and a number of coolies had to be requisitioned, since the friction of the rope dragging on the ground was enormous. however, the engineers soon had the cable stretched over its supports, and the winding machinery in place at the top of the grade. the single rope serves for both up and down traffic; a central crossing station being provided at which the descending can pass the ascending carrier. seven sleepers at a time are sent flying down the track at a rate of twenty miles an hour: a load departing every half-hour. the saving of labour, time, and expense is said to be very great, and when the saw mills have a larger output the economy of working will be still more remarkable. the longest passenger ropeway ever built is probably that over the chilkoot pass in alaska, which was constructed in 1897 and 1898 to transport miners from dyea to crater lake on their way to the yukon goldfields. from crater lake to the klondike the yukon river serves as a natural road, but the climb to its head waters was a matter of great difficulty, especially during the winter months, and accompanied by much suffering. but when the trestles had been erected for the fixed ropes, two in number, miners and their kits were hauled over the seven miles at little physical cost, though naturally the charges for transportation ruled higher than in less rugged regions. the opening of the white pass railway from skagway has largely abolished the need for this cable track, which has nevertheless done very useful work. the chilkoot ropeway has at least two spans of over 1,500 feet. as an engineering enterprise it claims our consideration, since the conveyance of ropes, timber, engines, etc., into so inhospitable a region, and the piecing of them together, demanded great persistence on the part of the engineers and their employã©s. cableways for removing the "over-burden" of surface mines and dumping it in suitable places, for excavating canals, for dredging, and for many other operations in which matter has to be moved comparatively short distances, the cableway is largely employed. we have already noticed that it differs from the ropeway in that it has to hoist and discharge its burdens as well as convey them. the cableway generally consists of a single span between two towers, which are either fixed or movable on rails according to the requirements of the work to be done. in addition to the main cable which bears the weight, and the rope which moves the skips along it, the cableway has the "fall" rope, which lowers the skip to the ground and raises it; the dumping rope, which discharges it; and the "button" rope, which pulls blocks off the horn of the skip truck at intervals as the latter moves, to support the "fall" rope from the main cable. if the fall rope sagged its weight would, after a certain amount had been paid out, overcome the weight of the skip, and render it impossible to lower the skip to the filling point. so a series of fall-rope carriers are, at the commencement of a journey from one end of the cableway, riding on an arm in front of the skip carriage. the button-rope, passing under a pulley on the top of the skip carriage, is furnished at intervals with buttons of a size increasing towards the point at which the skip must be lowered. the holes in the carriers are similarly graduated so as to pass over any button but the one intended to arrest them. if we watched a skip travelling to the lowering point, we should notice that the carriers were successively pulled off the skip carriage by the buttons, and strung along over the main cable and under the fall rope. when the skip has been lowered and filled the fall and hauling ropes are wound in; the skip rises to the main cable, and begins to travel towards the dumping point. as long as the dumping rope is also hauled in at the same rate as the hauling rope it has no effect on the skip, but when its rate of travel is increased by moving it on to a larger winding drum, the skip is tipped or opened, as the case may be, without being arrested. the skip may be filled by hand or made self-filling where circumstances permit. the cableway is so economical in its working that it has greatly advanced the process of "open-pit" mining. where ore lies near the surface it is desirable to remove the useless overlying matter (called "over-burden") bodily, and to convey it right away, in preference to sinking shallow shafts with their attendant drawbacks of timbering and pumping. an inclined railway is handicapped by the fact that it must occupy some of the surface to be uncovered, while liable to blockage by the dã©bris of blasting operations. the suspended cableway neither obstructs anything nor can be obstructed, and is profitably employed when a ton of ore is laid bare for every four tons of over-burden removed. in the case of the tilly foster mine, new york, where the removal of 300,000 tons of rock exposed 600,000 tons of ore from an excavation 450 ft. long by 300 ft. wide, the saving effected by the cableway was enormous. again, referring to the chicago drainage canal, "the records show that while labourers, sledging and filling into cars, averaged only 7 to 8-1/2 cubic yards per man per day, in filling into skips for the cable ways the labourers averaged from 12 to 17 cubic yards per day."[19] the first cableway erected by the lidgerwood manufacturing company for the prosecution of this engineering work handled 10,821 cubic yards a month, and proved so successful that nineteen similar plants were added. the cableways are suspended in this instance from two towers moving on parallel tracks on each bank of the canal, the towers being heavily ballasted on the outer sides of their bases to counteract the pull of the cable. from time to time, when a length had been cleared, the towers were moved forward by engines hauling on fixed anchors. the cableway is much used in the erection of masonry piers for bridges across rivers or valleys. materials are conveyed by it rapidly and easily to points over the piers and lowered into position. spans of over 1,500 feet have been exceeded for such purposes; and if need be, spans of 2,000 feet could be made to carry loads of twenty-five tons at a rate of twenty miles an hour. telpherage on most ropeways the skips or other conveyances are moved along the fixed ropes by trailing ropes working round drums driven by steam and controlled by brakes. but the employment of electricity has provided a system called _telpherage_, in which the vehicle carries its own motor, fed by current from the rope on which it runs and from auxiliary cables suspended a short distance above the main rope. "telpher" is a term derived from two greek words signifying "a far carrier," since the motor so named will move any distance so long as a track and current is supplied to it. the carrier--for ore, coal, earth, barrels, sacks, timber, etc.--is suspended from the telpher by the usual hook-shaped support common to ropeways, to enable the load to pass the arms of the posts or trestles bearing the rope. the telpher usually has two motors, one placed on each side of a two-wheeled carriage so as to balance; but sometimes only a single motor is employed. just above the running cable is the "trolley" cable, from which the telpher picks up current through a hinged arm, after the manner of an electric tram. the carriers are controlled on steep grades by an electric braking device, which acts automatically, its effect varying with the speed at which the telpher runs. the carrier wheels, driven by the motors, adhere to the cable without slipping on grades as severe as three in ten, even when the surface has been moistened by rain. "in order to stop the telpher at any desired point, the trolley wire is divided into a number of sections, each controlled by a switch conveniently located. by opening a switch the current is cut off from the corresponding section, and the telpher will stop when it reaches this point. it is again started by closing the switch. at curves a section of the trolley wire (_i.e._ overhead cable for current) is connected to the source of current through a 'resistance' which lowers the voltage (pressure of the current) across the motors at this point. thus, upon approaching a curve, the telpher automatically slows down, runs slowly around the curve until it passes the resistance section, and is then automatically accelerated."[20] the telpher line is very useful (for transporting material considerable distances) in districts where it would not pay to construct a surface railway. on plantations it serves admirably to shift grain, fruits, tobacco, and other agricultural products. then, again, a wide field is open to it for transmitting light articles, such as castings and parts of machinery, from one part of a foundry or manufactory to another, or from factory to vessel or truck for shipment. when coal has to be handled, the buckets are dumped automatically into bins. the telpher has much the same advantages over the steam-worked ropeway that an electric tram has over one moved by an endless cable. its control is easier; there is less friction; and the speed is higher. and in common with ropeways it can claim independence of obstructions on the ground, and the ability to cross ravines with ease, which in the case of a railway would have to be bridged at great expense. coaling warships at sea the war between russia and japan has brought prominently before the public the necessity of being able to keep a war vessel well supplied with coal: a task by no means easy when coaling stations are few and far between. the voyage of admiral rojdestvensky from russia to eastern waters was marked by occasions on which he entered neutral ports to draw supplies for his furnaces, though we know that colliers sailed with the warships to replenish their exhausted bunkers. in the old days of sailing vessels, their motive power, even if fitful, was inexhaustible. but now that steam reigns supreme as the mover of the world's floating forts, the problem of "keeping the sea" has become in one way very much more complicated. the radius of a vessel's action is limited by the capacity of her coal bunkers. her captain in war time would be perpetually perplexed by the question of fuel, since movement is essential to naval success, while any misjudged fast steaming in pursuit of the enemy might render his ship an inert mass, incapable of motion, because the coal supplies had given out; or at least might compel him to return for supplies to the nearest port at a slow speed, losing valuable time. [illustration: a temperley-miller marine cableway coaling h.m.s. "trafalgar" at sea a carrier, from which are slung the sacks of coal, is hauled backwards and forwards by steel ropes stretching between the foremast of the transport and a mast rigged on the warship.] just as a competitor in a long-distance race takes his nourishment without halting, so should a battleship be able to coal "on the wing." the task of transferring so many tons of the mineral from one ship's hold to that of another may seem easy enough to the inexperienced critic, and under favourable conditions it might not be attended by great difficulty. "why," someone may say, "you have only to bring the collier alongside the warship, make her fast, and heave out the coals." in a perfect calm this might be feasible; but let the slightest swell arise, and then how the sides of the two craft would bump together, with dire results to the weaker party! actual tests have shown this. at present "broadside" coaling is considered impracticable, but the "from bow to stern" method has passed through its initial stages, and after many failures has reached a point of considerable efficiency. the difficulties in transferring coal from a collier to a warship by which she is being towed will be apparent after very little reflection. in the first place, there is the danger of the cableway and its load dipping into the water, should the distance between the two vessels be suddenly diminished, and the corresponding danger of the cable snapping should the pitching of the vessels increase the distance between the terminals of the cableway. these difficulties have made it impossible to merely shoot coals down a rope attached high up a mast of the collier and to the deck of the warship. what is evidently needed is some system which shall pay the cableway out or take it in automatically, so as to counterbalance any lengthening or shortening movement of the vessels. the lidgerwood manufacturing company of new york, under the direction of mr. spencer miller, have brought out a cableway specially adapted for marine work. the two vessels concerned are attached by a stout tow-line, the collier, of course, being in the rear. to carry the load, a single endless wire rope, 3/8 inch in diameter and 2,000 feet long, is employed. it spans the distance between collier and ship twice, giving an inward track for full sacks, and an outward track for their return to the collier. on one vessel are two winches, the drums of which both turn in the same direction; but while one drum is rigidly attached to its axle, the other slips under a stress greater than that needed to keep the rope sufficiently taut. since the rope passes round a pulley at the other terminal, pressure placed at any point on the rope will tend to tighten both tracks, while a slackening at any point would similarly ease them. supposing, then, that the ships suddenly approach, there will be a certain amount of slack at once wound in; if, on the other hand, the ships draw apart, the slipping drum will pay out rope sufficient to supply the need. the constant slipping of this drum sets up great heat, which is dissipated by currents of air. as the sacks of coal arrive on the man-of-war they are automatically detached from the cable, and fall down a chute into the hold. in the temperley miller marine cableway the load is carried on a main cable kept taut by a friction drum, and the hauling is done by an endless rope which has its own separate winches. in actual tests made at sea in rough weather sixty tons per hour have been transferred, the vessels moving at from four to eight miles an hour. footnotes: [19] _cassier's magazine._ [20] _cassier's magazine._ chapter xviii automatic weighers scarcely less important than the rapid transference of materials from one place to another is the quick and accurate weighing of the same. if a pneumatic grain elevator were used in conjunction with an ordinary set of scales such as are to be found at a corn dealer's there would be great delay, and the advantage of the elevator would largely be lost. similarly a mechanical transporter of coal or ore should automatically register the tonnage of the mineral handled, to prevent undue waste of time. there are in existence many types of automatic weighing machines, the general principles of which vary with the nature of the commodity to be weighed. finely divided substances, such as grain, seeds, and sugar, are usually handled by _hopper_ weighers. the grain, etc., is passed into a bin, from the bottom of which it flows into a large pan. when the proper unit of weight--a hundredweight or a ton--has nearly been attained, the flow is automatically throttled, so that it may be more exactly controlled, and as soon as the full amount has passed, the machine closes the hopper door and tips the pan over. the latter delivers its contents and returns to its original position, while the door above is simultaneously opened for the operation to be repeated. a counting apparatus records the number of tips, so that a glance suffices to learn how much material has passed through the weigher, which may be locked up and allowed to look after itself for hours together. the "chronos" automatic grain scale is built in many sizes for charges of from 12 to 3,300 lbs. of grain, and tips five times a minute. avery's grain weigher takes up to 5-1/2 tons at a time. for materials of a lumpy nature, such as coal and ore, a different method is generally used. the hopper process would not be absolutely accurate, since the rate of feed cannot be exactly controlled when dust and large lumps weighing half a hundredweight or more are all jumbled together. therefore instead of a pan which tips automatically as soon as it has received a fixed weight, we find a bin which, when a quantity roughly equal to the correct amount has been let in, sinks on to a weigher and has its contents registered by an automatic counter, which continuously adds up the total of a number of weighings and displays it on a dial. so that if there be 10 lbs. in excess of a ton at the first charge, the dial records "one ton," and keeps the 10 lbs. "up its sleeve" against the next weighing, to which the excess is added. avery's mineral scale works, however, on much the same principle as that for grain already noticed, a special device being fitted to render the feed to the weighing pan as regular as possible. his weigher is used to feed mechanical furnace stokers. the quantity of coal used can thus be checked, while an automatic apparatus prevents the stoker bunkers from being overfilled. _continuous weighers_ register the amount carried by a conveyer while in motion. the recording apparatus comes into action at fixed intervals, _e.g._ as soon as the conveyer has moved ten feet. the weighing mechanism is practically part of the conveyer, and takes the weight of ten feet. the steelyard is adjusted to exactly counterbalance the unloaded belt or skips of its length, but rises in proportion to the load. as soon as the conveyer has travelled ten feet the weight on the machine is immediately recorded, and the steelyard returns to zero. _intermittent weighers_ record the weight of trucks or tubs passing over a railway or the cables of aerial track, the weigher forming part of the track and coming into play as soon as a load is fully on it. some machines not only weigh material, but also stow and pack it. we find a good instance in timewell's sacking apparatus, which weighs corn, chaff, flour, oatmeal, rice, coffee, etc., transfers it to sacks, and _sews the sack up_ automatically. the amount of time saved by such a machine must be very great. note.--the author desires to express his indebtedness to mr. george f. zimmer's _the mechanical handling of material_ for some of the information contained in the above chapter; and to the publishers, messrs. a. crosby lockwood and son, for permission to make use of the same. chapter xix transporter bridges when the writer was in rouen, in 1898, two lofty iron towers were being constructed by the seine: the one on the quai du havre, the other on the quai capelier, which borders the river on the side of the suburb st. sever. the towers rose so far towards the sky that one had to throw one's head very far back to watch the workmen perched on the summit of the framework. what were the towers for? they seemed much too slender for the piers of an ordinary suspension bridge fit to carry heavy traffic. an inquiry produced the information that they were the first instalment of a "transbordeur," or transporter bridge. what is a bridge of this kind? well, it may best be described as a very lofty suspension bridge, the girder of which is far above the water to allow the passage of masted ships. the suspended girder serves only as the run-way for a truck from which a travelling car hangs by stout steel ropes, the bottom of the car being but a few feet above the water. the truck is carried across from tower to tower, either by electric motors or by cables operated by steam-power. the transporter bridge in a primitive form has existed for some centuries, but its present design is of very modern growth. with the increase of population has come an increased need for uninterrupted communication. where rivers intervene they must be bridged, and we see a steady growth in the number of bridges in london, paris, new york, and other large towns. unfortunately a bridge, while joining land to land, separates water from water, and the dislocation of river traffic might not be compensated by the conveniences given to land traffic. the forth, brooklyn, saltash, and other bridges have, therefore, been built of such a height as to leave sufficient head-room under the girders for the masts of the tallest ships. but what money they have cost! and even the tower bridge, with its hinged bascules, or leaves, and bridges with centres revolving horizontally, devour large sums. wanted, therefore, an efficient means of transport across a river which, though not costly to install, shall offer a good service and not impede river traffic. thirty years ago mr. charles smith, a hartlepool engineer, designed a bridge of the transporter type for crossing the tees at middlesbrough. the bridge was not built, because people feared that the towers would not stand the buffets of the north-easterly gales. the idea promulgated by an englishman was taken up by foreign engineers, who have erected bridges in spain, tunis, and france. so successful has this type of ferry-bridge proved, that it is now receiving recognition in the land of its birth, and at the present time transporter bridges are nearing completion in wales and on the mersey. [illustration: the latest type of bridge the transporter bridge at bizerta, tunis. it has a span of 500 feet, and the suspension girder is 120 feet above high water, so that the largest vessels may pass under it from the mediterranean to the inland lakes. the car is seen near the bottom of the right-hand tower.] the first "transbordeur" built was that spanning the nervion, a river flowing into the bay of biscay near bilbao, a spanish town famous for the great deposits of iron ore close by. a pair of towers rises on each bank to a height of 240 feet, and carry a suspended trussed girder 530 feet long at a level of 150 feet above high-water mark. the car, giving accommodation for 200 passengers (it does not handle vehicles), hangs on the end of cables 130 feet long, and is propelled by a steam-engine situated in one of the towers. motion is controlled by the car-conductor, who is connected electrically with the engine-room. the lofty towers are supported on the landward side by stout steel ropes firmly anchored in the ground. these ropes are carried over the girder in the familiar curve of the suspension bridge, and attached to it at regular intervals by vertical steel braces. the cost of the bridge--â£32,000--compares favourably with that of any alternative non-traffic-blocking scheme, and the graceful, airy lines of the erection are by no means a blot on the landscape. the second "transbordeur" is that of rouen, already referred to. its span is rather less--467 feet--but the suspension girder lies higher by 14 feet. the car is 42 feet long by 36 broad, and weighs, with a full load, 60 tons. a passage, which occupies 55 seconds, costs one penny first class, one halfpenny second class; while a vehicle and horses pay 2-1/2d. to 4d., according to weight. the car is propelled by electricity, under the control of a man in the conning-tower perched on the roof. at bizerta we find the third flying-ferry, which connects that town with tunis, over a narrow channel between the mediterranean sea and two inland lakes. it replaced a steam-ferry which had done duty for about ten years. the lakes being an anchorage for war vessels, it was imperative that any bridge over the straits should not interrupt free ingress and egress. this bridge has a span of 500 feet, and like that at bilbao is worked by steam. light as the structure appears, it has withstood a cyclone which did great damage in the neighbourhood. it is reported that the french government has decided to remove the bridge to some other port, because its prominence would make it serve as a range-finder for an enemy's cannon in time of war. its place would be taken either by a floating-bridge or by a submarine tunnel. the nantes "transporter" over the loire differs from its fellows in one respect, viz. that it is built on the cantilever or balance principle. instead of a single girder spanning the space between the towers, it has three girders, the two end ones being balanced on the towers and anchored at their landward extremities by vertical cables. the gap between them is bridged by a third girder of bow shape, which is stiff enough in itself to need no central support. the motive power is electricity. all these structures will soon be eclipsed by two english bridges: the one over the usk at newport, monmouthshire; the other over the mersey and manchester ship canal at runcorn "gap," where the river narrows to 1,200 feet. the first of these has towers 250 feet high and 685 feet apart. the girders will give 170 feet head-room above high-water mark. five hundred passengers will be able to travel at one time on the car, besides a number of road vehicles, and as the passage is calculated to take only one minute, the average velocity will exceed eight miles an hour. the cost has been set down at â£65,000, or about one-thirtieth that of a suspension bridge, and one-third that of a bascule bridge. the bridge is being built by the french engineers responsible for the rouen _transbordeur_. coming to the much more imposing runcorn bridge we find even these figures exceeded. this span is 1,000 feet in length. the designer, mr. john j. webster, has already made a name with the great wheel which, at earl's court, london, has given many thousands of pleasure-seekers an aerial trip above the roofs of the metropolis. the following account by mr. w. g. archer in the _magazine of commerce_ describes this mammoth of its kind in some detail:-"the two main towers carrying the cables and the stiffening girders are built, one on the south side of the ship canal, and the other on the foreshore on the north bank of the river; and the approaches consist of new roadways, nearly flat, built between stone and concrete retaining walls as far as the water's edge, and a corrugated steel flooring, upon which are laid the timber blocks on concrete, resting on steel elliptical girders and cast-iron columns. the roadway in front of the towers is widened out to 70 feet, for marshalling the traffic, and for providing space for waiting-rooms, etc. the towers are constructed wholly of steel, rise 190 feet above high-water level, and are bolted firmly to the cast-iron cylinders below. each tower consists of four legs, spaced 30 feet apart at the base, and each pair of towers are 70 feet apart, and are braced together with strong horizontal and diagonal frames. each of the two main cables consists of 19 steel ropes bound together, each rope being built up of 127 wires 0â·16 inches in diameter. the ends of the cable backstays are anchored into the solid rock on each side of the river, about 30 feet from the rock surface. the weight of the main cables is about 243 tons, and from them are suspended two longitudinal stiffening girders, 18 feet deep, and placed 35 feet apart horizontally, the underside of the girders being 82 feet above the level of high water.... upon the lower flange of the stiffening girders are fixed the rails upon which runs the traveller, from which is suspended the car. the traveller is 77 feet long, and is carried by sixteen wheels on each rail. it is propelled by two electric motors of about 35 horse-power each.... the car will be capable of holding at one time four large wagons and 300 passengers, the latter being protected from the weather by a glazed shelter.... the time occupied by the car in crossing will be 2-1/4 minutes, so, allowing for the time spent in loading and unloading, it will be capable of making nine or ten trips per hour. this bridge, when completed, will have the largest span of any bridge in the united kingdom designed for carrying road traffic, the clear space over the mersey and ship canal being 1,000 feet.... the total cost of the structure, including parliamentary expenses, will be about â£150,000." mr. archer adds that, in spite of prophecies of disastrous collisions between transporter cars and passing ships, there has up to date been no accident of any kind. to those in search of a new sensation the experience of skimming swiftly a few feet above the water may be recommended. chapter xx boat and ship raising lifts in modern locomotion, whether by land or water, it becomes increasingly necessary to keep the way unobstructed where traffic is confined to the narrow limits of a pair of rails, a road, or a canal channel. we widen our roads; we double and quadruple our rails. canals are, as a rule, not alterable except at immense cost; and if, in the first instance, they were not built broad enough for the work that they are afterwards called upon to do, much of their business must pass to rival methods of transportation. modern canals, such as the manchester and kiel canals, were given generous proportions to start with, as their purpose was to pass ocean-going ships, and for many years it will not be necessary to enlarge them. the suez canal has been widened in recent years, by means of dredgers, which easily scoop out the sandy soil through which it runs and deposit it on the banks. but the corinth canal, cut through solid rock, cannot be thus economically expanded, and as a result it has proved a commercial failure. even if a canal be of full capacity in its channel-way there are points at which its traffic is throttled. however gently the country it traverses may slope, there must occur at intervals the necessity of making a lock for transferring vessels from one level to the other. sometimes the ascent or descent is effected by a series of steps, or flight of locks, on account of the magnitude of the fall; and in such cases the loss of time becomes a serious addition to the cost of transport. in several instances engineers have got over the difficulty by ingenious hydraulic lifts, which in a few minutes pass a boat through a perpendicular distance of many feet. at anderton, where the trent and mersey canal meets the weaver navigation, barges up to 100 tons displacement are raised fifty feet. two troughs, each weighing with their contents 240 tons, are carried by two cast-iron rams placed under their centres, the cylinders of which are connected by piping. when both troughs are full the pressure on the rams is equal, and no movement results; but if six inches of water be transferred from the one to the other, the heavier at once forces up the lighter. at fontinettes, on the neufosse canal, in france, at la louviã¨re, in belgium, and at peterborough, in canada, similar installations are found; the last handling vessels of 400 tons through a rise of 65 feet. fine engineering feats as these are, they do not equal the canal-lift on the dortmund-ems canal, which puts dortmund in direct water communication with the elbe, and opens the coal and iron deposits of the rhine and upper silesia to the busy manufacturing district lying between these two localities. about ten miles from its eastern extremity the main reach of the canal forks off at heinrichenburg, from the northward branch running to dortmund, its level being on the average some 49 feet lower than the branch. for the transference of boats an "up" and "down" line of four locks each would have been needed; and apart from the inevitable two hours' delay for locking, this method would have entailed the loss of a great quantity of precious water. mr. r. gerdau, a prominent engineer of dã¼sseldorf-grafenburg, therefore suggested an hydraulic lift, which should accommodate boats of 700 tons, and pass them from the one level to the other in five minutes. this scheme was approved, and has recently been completed. the principle of the lift is as follows:--a trough, 233 feet long, rests on five vertical supports, themselves carried by as many hollow cylindrical floats moving up and down in deep wells full of water. the buoyancy of the five floats is just equal to the combined weight of the trough and its load, so that a comparatively small force causes the latter to rise or fall, as required. by letting off water from the trough--which is, of course, furnished with doors to seal its ends--it would be made to ascend; while the addition of a few tons would cause a descent. but this would mean waste of water; and, were the trough not otherwise governed, a serious accident might happen if a float sprang a leak. motion is therefore imparted to the trough by four huge vertical screws, resting on solid masonry piers, and turning in large collars attached to the trough near its corners. all the screws work in unison through gearing, as they are sufficiently stout to bear the whole load; even were the floats removed, no tilting or sudden fall is possible. the screws are driven by an electric motor of 150 horse-power, perched on the girders joining the tops of four steel towers which act as guides for the trough to move in, while they absorb all wind-pressure. under normal circumstances the trough rises or sinks at a speed of four inches per second. the total mass in motion--trough, water, boat, and floats--is 3,100 tons. our ideas of a float do not ordinarily rise above the small cork which we take with us when we go a-fishing, or at the most above the buoy which bobs up and down to mark a fair-way. these five "floats"--so called--belong to a very much larger class of creations. each is 30 feet across inside and 46-1/2 feet high. their wells, 138 feet deep, are lined with concrete nearly a yard thick, to ensure absolute water-tightness, inside the stout iron casings, which rise 82 feet above the bottom. in view of the immense weight which they have to carry, the piers under the screw-spindles are extremely solid. at its base each measures 14 feet by 12 feet 4 inches, and tapers upwards for 36 feet till these dimensions have contracted to 8 feet 10 inches by 6 feet 6 inches. the spindles, 80 feet long and 11 inches in diameter, must be four of the largest screws in existence. to make it absolutely certain that they contained no flaws, a 4-inch central hole was drilled through them longitudinally--another considerable workshop feat. if shafts of such length were left unsupported when the trough was at its highest point, there would be danger of their bending and breaking; and they are, therefore, provided with four sliding collars each, connected each to its fellow by a rod. when the trough has risen a fifth of its travel the first rod lifts the first collar, which moves in the guide-pillars. this in turn raises the second; the second the third; and so on. so that by the time the trough is fully raised each spindle is kept in line by four intermediate supports. the trough, 233 feet long by 34-1/2 feet wide, will receive a vessel 223 feet long between perpendiculars. it has a rectangular section, and is built up of stout plates laid on strong cross-girders, all carried by a single huge longitudinal girder resting on the float columns. one of the most difficult problems inseparable from a structure of this kind is the provision of a water-tight joint between the trough and the upper and lower reaches of the canal. at each end of the trough is a sliding door faced on its outer edges with indiarubber, which the pressure of the water inside holds tightly against flanges when pressure on the outside is removed. the termination of the canal reaches have similar doors; but as it would be impossible to arrange things so accurately that the two sets of flanges should be water-tight, a wedge, shaped like a big u, and faced on both sides with rubber, is interposed. the wedge at the lower reach gate is thickest at the bottom; the upper wedge the reverse; so that the trough in both cases jams it tight as it comes to rest. the wedges can be raised or lowered in accordance with the fluctuations of the canals. after thus briefly outlining the main constructional features of the lift, let us watch a boat pass through from the lower to the upper level. it is a steamer of 600 tons burden, quite a formidable craft to meet so far inland; while some distance away it blows a warning whistle, and the motor-man at his post moves a lever which sets the screw in motion. the trough sinks until it has reached the proper level, when the current is automatically broken, and it sinks no further. its travel is thus controllable to within 3/16 of an inch. an interlocking arrangement makes it impossible to open the trough or reach gates until the trough has settled or risen to the level of the water outside. on the other hand, the motor driving the lifting screws cannot be started until the gates have been closed, so that an accidental flooding of the countryside is amply provided against. a man now turns the crank of a winch on the canal bank and unlocks the canal gate. a second twist couples the gates between the canal and the trough together and starts the lifting-motors overhead, which raise the twenty-eight ton mass twenty-three feet clear of the water-level. the boat enters; the doors are lowered and uncoupled; the reach gate is locked. the spindle-motor now starts; up "she" goes, and the process of coupling and raising gates is repeated before she is released into the upper reach. from start to finish the transfer occupies about five minutes. if a boat is not self-propelled, electric capstans help it to enter and leave the trough. such a vessel could not be passed through in less than twenty minutes. putting on one side the ship dry docks, which can raise a 15,000 ton vessel clear of the sea, the dortmund hydraulic lift is the largest lift in the world, and the novelty of its design will, it is hoped, render the above account acceptable to the reader. before leaving the subject another canal lift may be noticed--that on the grand junction canal at foxton, leicestershire--which has replaced a system of ten locks, to raise barges through a height of 75 feet. the new method is the invention of messrs. g. and c. b. j. thomas. in principle it consists of an inclined railway, having eight rails, four for the "up" and as many for the "down" traffic. on each set of four rails runs a tank mounted on eight wheels, which is connected with a similar tank on the other set by 7-inch steel-wire ropes passing round winding drums at the top of the incline. the tanks are thus balanced. at the foot of the incline a barge which has to ascend is floated into whichever tank may be ready to receive it, and the end gate is closed. an engine is then started, and the laden tank slides "broadside on" up the 300-foot slope. the summit being reached, the tank gates are brought into register with those of the upper reach, and as soon as they have been opened the boat floats out into the upper canal. boats of 70 tons can be thus transferred in about twelve minutes, at a cost of but a few pence each. on a busy day 6,000 tons are handled. [illustration: _by permission of_] [_mr. gordon thomas._ a boat lift a canal barge lift which has superseded ten locks at foxton, leicestershire. two tanks, balancing one another, run on separate tracks up and down an incline. at the bottom and top of the incline the tank is submerged so that a barge may float in or out.] a ship-raising lift the writer has treated one form of lift for raising ships out of the water--the floating dry dock--elsewhere,[21] so his remarks in this place will be confined to mechanism which, having its foundations on mother earth, heaves mighty vessels out of their proper element by the force of hydraulic pressure. looking round for a good example of an hydraulic ship-lift, we select that of the union ironworks, san francisco. some years ago the works were moved from the heart of the city to the edge of mission bay, with the object of carrying on a large business in marine engineering and shipbuilding. for such a purpose a dry dock, which in a short time will lift a vessel clear of the water for cleaning or repairs, is of great importance to both owners and workmen. by the courtesy of the proprietors of _cassier's magazine_ we are allowed to append the following account of this interesting lift. the site available for a dock at the union ironworks was a mud-flat. the depth of soft mud being from 80 to 90 feet, would render the working of a graving dock (_i.e._ one dug out of the ground and pumped dry when the entrance doors have been closed) very disagreeable; as such docks, where much mud is carried in with the water, require a long time to be cleaned and to dry out. plans were therefore prepared by mr. george w. dickie for an hydraulic dock, including an automatic control, which the designer felt confident would meet all the requirements of the situation, and which, after careful consideration, the union ironworks decided to build. work was begun in january, 1886, and the dock was opened for business on june 15th, 1887--a very fine record. this dock consists of a platform built of cross and longitudinal steel girders, 62 feet wide and 440 feet long, having keel blocks and sliding bilge blocks upon which the ship to be lifted rests. the lifting power is generated by a set of four steam-driven, single-acting horizontal plunger pumps, the diameter of the plungers being 3-1/2 inches and the stroke 36 inches. forty strokes per minute is the regular speed. there is a weighted accumulator, or regulator, connected with the pumps, the throttle valve of the engines being controlled by the accumulator.[22] the load on the accumulator consists of a number of flat discs of metal, the first one about 14 inches thick and the others about 4 inches thick, the diameter being about 4 feet. the first disc gives a pressure of 300 lbs. per square inch. this is sufficient to lift the dock platform without a ship, and is always kept on. in lifting a ship, as she comes out of the water and gets heavier on the platform, additional discs are taken on by the accumulator ram as required. the discs are suspended by pins on the side catching into links of a chain. the engineer, to take on another disc, unhooks the throttle from the accumulator rod, runs the engine a little above the normal speed, the accumulator rises and takes the weight of the disc to be added; the link carrying that disc is thus relieved and is withdrawn. the engineer again hooks the accumulator rod to the engine throttle, and the whole is self-acting again until another weight is required. when all the discs are on the ram the full pressure of 1,100 lbs. per square inch is reached, which enables a ship of 4,000 tons weight to be raised. there are eighteen hydraulic rams on each side of the dock. these rams are each 30 inches in diameter and have a stroke of 16 feet; and as the platform rises 2 feet for 1 foot movement of the rams, the total vertical movement of the platform is 32 feet. when lowered to the lowest limit there are 22 feet of water over the keel blocks at high tide. the foundations consist of seventy-two cylinders of iron, which extend from the top girders to several feet below the mud line. these cylinders are driven full of piles, no pile being shorter than 90 feet. the cylinders are to protect the piles from the _teredo_ (the timber-boring worm), which is very destructive in san francisco harbour. a heavy cast-iron cap completes each of the foundation piers, and two heavy steel girders extend the full length of the dock on each side, resting on the foundation piers and uniting them all longitudinally. the hydraulic cylinders are carried by large castings resting on the girders, each having a central opening to receive a cylinder, which passes down between the piers. there are thirty-six foundation piers, and eighteen hydraulic cylinders on each side of the dock. on the top of each hydraulic ram is a heavy sheave or pulley, 6 feet in diameter, over which pass eight steel cables, 2 inches in diameter, making in all 288 cables. one end of each cable is anchored in the bed-plates supporting the hydraulic cylinders, while the other end is secured to the side girders of the platform. each of the cables has been tested with a load of 80 tons, so that the total test load for the ropes has been 21,000 tons. in lifting a ship the load is never evenly distributed on the platform. there is, in fact, often more than one ship on the platform at once. some rams, therefore, may have a full load and others much less. under these conditions, to keep the platform a true plane, irrespective of the irregular distribution of the load, mr. dickie designed a special valve gear to make the action of the dock perfectly automatic. down each side of the dock a shaft is carried, operated by a special engine in the power house. at each hydraulic ram this shaft carries a worm, gearing with a worm-wheel on a vertical screw extending the full height reached by the stroke of the ram. this screw works in a nut on the end of a lever, the other end of which is attached to the ram. between the two points of support a rod, working the valves--also carried by the ram--engages with the lever. if at a given moment the screw-end is raised, say, six inches, the lever opens the valve. as the ram rises, the lever, having its other end similarly lifted by the rise, gradually assumes a horizontal position, and the valve closes. to lift the dock the engine working the valve shaft is started, and with it the operating screws. these, through the levers, open the inlet valves. the rams now begin to move up: if any one has a light load it will move up ahead of the other, but in doing so it lifts the other end of the lever and closes the valve. in fact, the screws are continually opening the valves, while the motion of the rams is continually closing them, so that no ram can move ahead of its screw, and the speed of the screw determines the rate of movement of the lifting platform. to lower the dock, the engine operating the valve shaft is reversed, and the screws and levers then control the outlet valves as they controlled the inlet valves in raising. when the platform has reached the limit of its movement, a line of locks on top of the foundation girders, thirty-six on each side, are pushed under the platform by an hydraulic cylinder, and the platform is lowered on to them, where it rests until the work is done on the ship; then the platform is again lifted, the locks are drawn back, and the platform with its load is lowered until the ship floats out. all the operations are automatic. since the dock was opened well over a thousand ships have been lifted in it without any accident whatever; the total register tonnage approaching 2,000,000. the great favour in which the dock is held by shipowners and captains is partly due to the fact already mentioned, that the ship is lifted above the level of tide water, where the air can circulate freely under the bottom, thus quickly taking up all the moisture, and where the workmen can carry on operations with greater comfort. when extensive repairs have to be undertaken on iron or steel vessels, the fact that this dock forms part of an extensive shipbuilding plant, and is located right in the yard, enables such repairs to be executed with despatch and economy. several large steamships have had the under-water portions of their hulls practically rebuilt in this dock. the steamship _columbia_, of the oregon line, had practically a new bottom, including the whole of the keel, completed in twenty-six days. this is possible, because every facility is alongside the dock and the bottom of the vessel is on a level with the yard. this being the only hydraulic dock controlled automatically (in 1897), it has attracted a large amount of attention from engineering experts in this class of work. english, french, german, and russian engineers have visited the union iron works to study its working, and their reports have done much to bring the facilities offered to shipping for repairs by the union iron works to the notice of shipowners all the world over. footnotes: [21] _the romance of modern engineering_, pp. 383 foll. [22] for explanation of the "accumulator," see the chapter on hydraulic tools (p. 81). chapter xxi a self-moving staircase at the american exhibition, held in the crystal palace in 1902, there was shown a staircase which, on payment of a penny, transported any sufficiently daring person from the ground-floor to the gallery above. all that the experimenters had to do was to step boldly on, take hold of the balustrade, which moved at an equal pace with the stairs, and step off when the upper level was reached. the "escalator" (latin _scalae_ = flight of stairs) hails from the united states, where it is proving a serious rival to the elevator. in principle, it is a continuously working lift, the slow travel of which is more than compensated by the fact that it is always available. the ordinary elevator is very useful in a large business or commercial house, where it saves the legs of people who, if they had to tramp up flight after flight of stairs, would probably not spend so much money as they would be ready to part with if their vertical travel from one floor to another was entirely free of effort. but the ordinary lift is, like a railway, intermittent. we all know what it means to stand at the grille and watch the cage slide downwards on its journey of, perhaps, four floors, when we want to go to a floor higher up. rather than face the delay we use our legs. theoretically, therefore, a large emporium should contain at least two lifts. if the number be further increased, the would-be passenger will have a still better chance of getting off at once. thus at the station of the central london railway we have to wait but a very few seconds before a grille is thrown back and an attendant invites us to "hurry up there, please!" yet there is delay while the cage is being filled. the actual journey occupies but a small fraction of the time which elapses between the moment when the first passenger enters the lift at the one end of the trip and the moment when the last person leaves it at the other end. in a building where the lift stops every fifteen feet or so to take people on or put them off, the waste of time is still more accentuated. the escalator is always ready. you step on and are transported one stage. a second staircase takes you on at once if you desire it. there is no delay. furthermore, the room occupied by a single escalator is much less than that occupied by the number of lifts required to give anything like an equally efficient service. in large american stores, then, it is coming into favour, and also on the manhattan elevated railway of new york. when once the little nervousness accompanying the first use has worn off, it eclipses the lift. a writer in _cassier's magazine_ says: "in one large retail store during the holiday season more than 6,000 persons per hour have been carried upon the escalator for five hours of the day, and the aggregate for an entire day is believed to be 50,000. in the same store on an ordinary day the passengers alighting at the second floor from the eight large lifts, which run from the basement to the fifth floor, were counted, likewise the number at the escalator. this latter was found to be 859 per cent. of the number delivered by the eight lifts. in another establishment, in a very busy hour, the number taken from the first floor by the escalator was four times the number taken from the first floor by the fourteen lifts, which were running at their maximum capacity. to the merchant this spells opportunity for business. "the experience at the twenty-third street and sixth avenue station of the manhattan elevated railway in new york, during a recent shut-down of the escalator, which has been in service for some time, is interesting as showing the attitude of the public, of which many millions have been carried by the installation during the several years of its operation. the daily traffic receipts of this station for a period beginning several weeks before the shut-down and extending as many after, for the years 1903 and 1902, and receipts of the adjacent stations for the same period were carefully plotted ... and the loss area during the period of shut-down was determined. the loss area was found to embrace 64,645 fares. it was, furthermore, daily a matter of observation that numbers of people, finding that the escalator was not running, refused to climb the stairs, and turned away from the station. "in the case of a great store, the escalator may be constructed as one continuous machine, with landings at each floor, and so arranged that steps which carry passengers up may perform a like service in carrying others down; or separate machines may be installed in various locations affording the best opportunity for displaying merchandise to the customer who may be proceeding from the lower to the upper floor. in the case of a six-storey building so equipped with escalator service in both directions, or in all ten escalator flights, it is obvious that the facilities are equal to an impossible number of elevators; and as facility of access has a direct bearing upon opportunities for business, it may well be argued that the relative value, measured by rent, of the main and upper floors is greatly changed." each step in a staircase has two parts--the "tread" or horizontal board on which the foot is placed, and the vertical "riser" which acts both as a support to the tread above and also prevents the foot from slipping under the tread. in the escalator each tread is attached rigidly to its riser, and the two together form an independent unit. for the convenience of passengers in stepping on or off at the upper and lower landings, the treads in these places are all in the same horizontal plane. as they approach the incline the risers gradually appear, and the treads separate vertically. at the top of the incline the process is gradually reversed, the risers disappearing until the treads once more form a horizontal belt. the means of effecting this change is most ingenious. each tread and its riser is carried on a couple of vertical triangular brackets, one at each side of the staircase. the base of the bracket is uppermost, to engage with the tread, and its apex has a hole through which passes a transverse bar, which in its central part forms a pin in the link-chain by which power is transmitted to the escalator. naturally, the step would tip over. this is prevented by a yoke attached to each end of the bar, at right angles to it and parallel to the tread. the yoke has at each extremity a small wheel running on its own rail--there being two rails for each side of the staircase. since step, brackets, bar, and yoke are all rigidly joined together, the step is unable to leave the horizontal, but its relation to the steps above and below is determined by the arrangement of the rails on which the yoke wheels run. when these are in the same plane, all the yokes, and consequently the treads, will also be in the same plane. but at the incline, where the inner rail gradually sinks lower than its fellow, the front wheel of one tread is lower than the front wheel of the next, and the risers appear. it may be added that, owing to the double track at each side of the staircase, the back wheel of one tread does not interfere with the front wheel of that below; and that on the level they come abreast without jostling, as the yoke is bent. the chain, of which the step-bars form pins, travels under the centre of the staircase. it is made up of links eighteen inches long, having, in addition to the bars, a number of steel cross-pins 1-1/2 inches in diameter, their axes three inches apart, so that the chain as a whole has a three-inch "pitch." the hubs of the links are bushed with bronze, and have a graphite "inlay," which makes them self-lubricating. every joint is turned to within 1/1,000 inch of absolute accuracy. the tracks are of steel and hardwood, insulated from the ironwork which supports them by sheets of rubber. the wheels are so constructed as to be practically noiseless, so that as a whole the escalator works very quietly. "it has been observed," says the authority already quoted, "that beginners take pains to step upon a single tread, and that after a little experience no attention whatever is given to the footing, owing to the facility of adapting oneself to the situation. the upper landing is somewhat longer, thereby affording an interval for stepping off at either side of sufficient duration to meet the requirements of the aged and infirm. the sole function of the travelling landing is to provide a time interval to meet the requirements of the slowest-acting passenger, and not of the alert. the terminal of the exit landing, be it top or bottom (for the escalator operates equally well for either ascent or descent), is a barrier, called the shunt, of which the lower member travels horizontally in a plane oblique to the direction of movement of the steps, and at a speed proportionately greater, thereby imparting a right-angle resultant to the person or obstacle on the step which may come in contact with the shunt. by reason of this resultant motion, the person or obstacle is gently pushed off the end of the step upon the floor, without shock or injury in the slightest degree. the motion of the escalator is so smooth and constant that it does not interpose the least obstacle to the free movement of the passenger, who may walk in either direction or assume any attitude to the same degree as upon a stationary staircase." at cleveland, u.s.a., there has been erected a rolling roadway, consisting of an inclined endless belt and platform made of planks eight feet long, placed transversely across the roadway. the timbers are fastened together in trucks of two planks each, adjoining trucks being joined by heavy links to form a moving roadway, which runs on 4,000 small wheels. at each end the roadway, which is continuous, passes round enormous rollers. its total length is 420 feet, and the rise 65 feet. four electric motors placed at regular intervals along its length, and all controlled by one man at the head of the incline, drive it at three miles an hour. it can accommodate six wagons at a time. chapter xxii pneumatic mail tubes you put your money on the counter. the shop assistant makes out a bill; and you wonder what he will do with it next. these large stores know nothing of an open till. yet there are no cashiers' desks visible; nor any overhead wires to whisk a carrier off to some corner where a young lady, enthroned in a box, controls all the pecuniary affairs of that department. while you are wondering the assistant has wrapped the coin in the bill and put the two into a dumb-bell-shaped carrier, which he drops into a hole. a few seconds later, flop! and the carrier has returned into a basket under another opening. there is something so mysterious about the operation that you ask questions, and it is explained to you that there are pneumatic tubes running from every counter in the building to a central pay-desk on the first or second floor; and that an engine somewhere in the basement is hard at work all day compressing air to shoot the carriers through their tubes. certainly a great improvement on those croquet-ball receptacles which progressed with a deliberation maddening to anyone in a hurry along a wooden suspended railway! now, imagine tubes of this sort, only of much larger diameter, in some cases, passing for miles under the streets and houses, and you will have an idea of what the pneumatic mail despatch means: the cash and bill being replaced by letters, telegrams, and possibly small parcels. "swift as the wind" is a phrase often in our mouths, when we wish to emphasise the celerity of an individual, an animal, or a machine in getting from one spot of the earth's surface to another. mercury, the messenger of uncertain-tempered jove, was pictured with wings on his feet to convey, symbolically, the same notion of speed. the modern human messenger is so poor a counterpart of the god, and his feet are so far from being winged, that for certain purposes we have fallen back on elemental air-currents, not unrestrained like the breezes, but confined to the narrow and certain paths of the metal tube. the pneumatic despatch, which at the present day is by no means universal, has been tried in various forms for several decades. its first public installation dates from 1853, when a tube three inches in diameter and 220 yards long was laid in london to connect the international telegraph company with the stock exchange. a vacuum was created artificially in front of the carrier, which the ordinary pressure of the atmosphere forced through the tube. soon after this the post-office authorities took the matter up, as the pneumatic system promised to be useful for the transmission of letters; but refused to face the initial expense of laying the tube lines. when, in 1858, mr. c. f. varley introduced the high pressure method, pneumatic despatch received an impetus comparable to that given to the steam-engine by the employment of high-pressure steam. it was now possible to use a double line of tubes economically, the air compressed for sending the carriers through the one line being pumped out of a chamber which sucked them back through the other. tubes for postal work were soon installed in many large towns in great britain, europe, and the united states; including the thirty-inch pneumatic railway between the north-western district post office in eversholt street and euston station, which for some months of 1863 transported the mails between these two points. the air was exhausted in front of the carriage by a large fan. encouraged by its success, the company built a much larger tube, nearly 4-1/2 feet in diameter, to connect euston station with the general post office. this carried fourteen tons of post-office matter from one end to the other in a quarter of an hour. there was an intermediate station in holborn, where the engines for exhausting had been installed. but owing to the difficulty of preventing air leakage round the carriages the undertaking proved a commercial failure, and for years the very route of this pneumatic railway could not be found; so quickly are "failures" forgotten! the more useful small tube grew most vigorously in america and france. in, or about, the year 1875 the western union telegraph company laid tubes in new york to despatch telegrams from one part of the city to the other, because they found it quicker to send them this way than over the wires. eighteen years later fifteen miles of tubes were installed in chicago to connect the main offices of the same company with the newspaper offices in the town, and with various important public buildings. messages which formerly took an hour or more in delivery are now flipped from end to end in a few seconds. the philadelphia people meanwhile had been busy with a double line of six-inch tubes, 3,000 feet long, laid by mr. b. c. batcheller between the bourse and the general post office, for the carriage of mails. the first thing to pass through was a bible wrapped in the "stars and stripes." a 30 horse-power engine is kept busy exhausting and compressing the air needed for the service, which amounts to about 800 cubic feet per minute. philadelphia can also boast an eight-inch service, connecting the general post office with the union railway station, a mile away. one and a half minutes suffice for the transit of the large carriers packed tightly with letters and circulars, nearly half a million of which are handled by these tubes daily. new york is equally well served. tubes run from the general post office to the produce exchange, to brooklyn, and to the grand central station. the last is 3-1/2 miles distant; but seven minutes only are needed for a tube journey which formerly occupied the mail vans for nearly three-quarters of an hour. paris is the city of the _petit bleu_, so important an institution in the gay capital. here a network of tubes connects every post office in the urban area with a central bureau, acting the part of a telephone exchange. if you want to send an express message to a friend anywhere in paris, you buy a _petit bleu_, _i.e._ a very thin letter-card not exceeding 1/4 oz. in weight, at the nearest post office, and post it in a special box. it whirls away to the exchange, and is delivered from there if its destination be close at hand; otherwise it makes a second journey to the office most conveniently situated for delivery. everybody uses the _voie pneumatique_ of paris, so much cheaper than, and quite as expeditious as, the telegraph; with the additional advantage that all messages are transmitted in the sender's own handwriting. the system has been instituted for a quarter of a century, and the parisians would feel lost without it. london is by no means tubeless, for it has over forty miles of 1-1/2, 2-1/4, and 3-inch lines radiating from the postal nerve-centre of the metropolis, of lengths ranging from 100 to 2,000 yards. the tubes are in all cases composed of lead, enclosed in a protecting iron piping. to make a joint great care must be exercised, so as to avoid any irregularity of bore. when a length of piping is added to the line, a chain is first passed through it, which has at the end a bright steel mandrel just a shade larger than the pipe's internal diameter. this is heated and pushed half-way into the pipe already laid; and the new length is forced on to the other half till the ends touch. a plumber's joint having been made, the mandrel is drawn by the chain through the new length, obliterating any dents or malformations in the interior. the main lines are doubled--an "up" and a "down" track; short branches have one tube only to work the inward and the outward despatches. the carriers are made of gutta-percha covered with felt. one end is closed by felt discs fitting the tube accurately to prevent the passage of air, the other is open for the introduction of messages. as they fly through the tube, the carriers work an automatic signalling apparatus, which tells how far they have progressed and when it will be safe to despatch the next carrier. the london post-office system is worked by six large engines situated in the basement of the general post office. so useful has the pneumatic tube proved that a bill has been before parliament for supplying london with a 12-inch network of tubes, totalling 100 miles of double line. in a letter published in _the times_, april 19, 1905, the promoters of the scheme give a succinct account of their intentions, and of the benefits which they expect to accrue from the scheme if brought to completion. the batcheller system, they write, with which it is proposed to equip london, is not a development of the miniature systems used for telegrams or single letters here or in paris, berlin, and other cities. such systems deal with a felt carrier weighing a few ounces, which is stopped by being blown into a box. the batcheller system deals with a loaded steel carrier weighing seventy pounds travelling with a very high momentum. the difference is fundamental. in this sense pneumatic tubes are a recent invention, and absolutely new to europe. the batcheller system is the response to a pressing need. careful observations show that more than 30 per cent. of the street traffic is occupied with parcels and mails. these form a distinct class, differentiated from passengers on the one hand and from heavy goods on the other. the batcheller system will do for parcels and mails what the underground electric railways do for passengers. it has been in use for twelve years in america for mail purposes, and where used has come to be regarded as indispensable. the plan for london provides for nearly one hundred miles of double tubes with about twice that number of stations for receiving and delivery. the system will cover practically the county of london, and no point within that area can be more than one-quarter of a mile from a tube station. beyond the county of london deliveries will be made by a carefully organised suburban motor-cart service. thirty of the receiving stations are to be established in the large stores. the diameter of the tube is to be of a size that will accommodate 80 per cent. of the parcels, as now wrapped, and 90 per cent. with slight adaptation. the remaining 10 per cent.--furniture, pianos, and other heavy goods--are to be dealt with by a supplementary motor service. if the tubes were enlarged their object would be partially defeated, for with the increased size would go increased cost, great surplus of capacity, less frequent despatch, and lower efficiency generally. the unsuccessful euston tunnel of forty years ago--practically an underground railway--is an extreme illustration of this point, though in that case there were grave mechanical defects as well. from a mechanical point of view the system has been brought to such perfection that it is no more experimental than a locomotive or an electric tramcar. the unique value of tube service is due to immediate despatch, high velocity of transit, immunity from traffic interruption, and economy. the greatest obstacle to rapid intercommunication is the delay resulting from accumulations due to time schedules. the function of tube service is to abolish time schedules and all consequent delays. the number of trades parcels annually delivered in london is estimated at _more than 200,000,000_. a careful canvass has been made of 1,000 shops only, which represent a very small fraction of the total number in the county. as a result it has been ascertained that these 1,000 shops deliver no fewer than 60,000,000 parcels yearly, a fact that seems to more than justify the foregoing estimate; on the other hand, it is known from official data that the parcel post in london is represented by less than 25,000,000, or one-ninth of the total parcel traffic. with a tube system in operation, every parcel, instead of waiting for "the next delivery," would leave the shop immediately. after being despatched by the tube it would be delivered at a tube station within a quarter of a mile at least of its destination, and thence by messenger. the entire time consumed for an ordinary parcel would be not over an hour, and for a special parcel fifteen to twenty minutes. they require from three to six hours or longer at present. the advantages of the tube system to the public would be manifold. customers would find their purchases at home upon their return, or, if they preferred, could do their shopping by telephone, making their selections from goods sent on approval by tube. the shopman would find himself relieved from a vast amount of confusion and annoyance, less of his shop space given up to delivery, and his expenses reduced. small shops would be able to draw upon wholesale houses for goods not in stock, while the customer waited. such delay and confusion as are frequently occasioned by fogs would be reduced to a minimum. while the success of the project is not dependent on post office support, the post office should be one of the greatest gainers by it. the time of delivery of local letters would be reduced from an average of three hours and six minutes to one hour. express letters would be delivered more quickly than telegrams. this has been demonstrated conclusively again and again in new york and other american cities where the tubes have been in operation for years. the latest time of posting country letters would be deferred from one-half to one hour, and incoming letters would be advanced by a similar period. the parcels post would gain in precisely the same way, but to an even larger extent. if the post office choose to avail themselves of the opportunity, every post office will become a tube station and every tube station a post office. thus the same number of postmen covering but a tithe of the present distances could make deliveries without time schedules at intervals of a few minutes with a handful instead of a bagful of letters. the sorting of mails would be performed at every station instead of at a few. incoming country mails would be taken from the bags at the railway termini, and the same bags refilled with outgoing country mails, thus avoiding needless carriage to the post office and back. no bags at all would be used for local mails, the steel carriers themselves answering that purpose. at every tube terminal a post-office clerk would be stationed, so that the mails would never for an instant be out of post-office control. its absolute security would be further ensured by a system of locking, so that the carriers could only be opened by authorised persons at the station to which they were directed. these safeguards offer a striking contrast to the present method that entrusts mail bags to the sole custody of van drivers in the employ of private contractors. if the mails were handled by tube, business men would be able to communicate with each other and receive replies several times in one day, and country and foreign letters could always be answered upon the day of receipt. the effect would be felt all over the empire. would the laying of the tubes seriously impede traffic? the promoters assure us that the inconvenience would not be comparable to that caused by laying a gas, water, or telephone system. when one of those has been laid the annoyance, they urge, has only begun. the streets must be periodically reopened for the purpose of making thousands of house connections, extensions, and repairs. when a pneumatic tube is once down it is good for a generation at least. it is not subject to recurrent alterations incidental to house connections and repairs. in three american cities the tubes have been touched but three times in twelve years, and in those cases the causes were a bursting water main and faulty adjacent electric installations. the repairs were effected in a few hours. from a general consideration of the scheme we may now turn to some mechanical details. the pipes would be of 1 foot internal diameter, made in 12-foot lengths. "straight sections," writes an engineering correspondent of _the times_, "would be of cast-iron, bored, counter-bored, and turned to a slight taper at one end, to fit a recess at the other end (of the next tube), to form the joints, which could be caulked. joints made in this way are estimated to permit of a deflection of 2 inches from the straight, so that the laying and bedding need not be exact. bent sections are to be of seamless brass; these are bored true before bending. the permissible curvature is determined upon the basis of a _maximum_ bend of 1 foot radius for every 1 inch of diameter; the 1 foot diameter of the london tubes would consequently be allowed a _maximum_ curvature of 12 foot radius. measured at the enlarged end, the over-all diameter of each pipe is 17 inches, and as two such pipes are to be laid side by side, with 18 inches between centres, the clear width will be 35 inches. the trenches are therefore to be cut 36 inches wide, and in order to have a comparatively free run for the sections, it is proposed to cut the trenches 6 feet deep." when the hundred miles of piping have been laid, the entire system will be tested to a pressure of 25 lbs. to the square inch, or about two and a half times the working pressure. engines of 10,000 h.p. will be required to feed the lines with air, for the propulsion of the carriers, each 3 feet 10 inches long, and weighing 70 lbs. in order to ensure the delivery of a carrier at its proper destination, whether a terminus or an intermediate station, mr. batcheller has made a most ingenious provision. on the front of a carrier is fixed a metal plate of a certain diameter. at each station two electric wires project into the tube, and as soon as a plate of sufficient diameter to short-circuit these wires arrives, the current operates delivery mechanism, and the carrier is switched off into the station box. the despatcher, knowing the exact size of disc for each station, can therefore make certain that the carrier shall not go astray. it may occur to the reader that, should a carrier accidentally stick anywhere in the tubes, it would be a matter of great difficulty to locate it. evidently one could not feel for it with a long rod in half a mile of tubing--the distance between every two stations--with much hope of finding it. but science has evolved a simple, and at the same time quite reliable, method of coping with the problem. m. bontemps is the inventor. he located troubles in the paris tubes by firing a pistol, and exactly measuring the time which elapsed between the report and its echo. as the rate of sound travel is definitely known, instruments of great delicacy enable the necessary calculations to be made with great accuracy. when a breakdown occurred on the philadelphia tube line, mr. batcheller employed this method with great success, for a street excavation, made on the strength of rough measurements with the timing apparatus, came within a few feet of the actual break in the pipe, caused by a subsidence, while the carriers themselves were found almost exactly at the point where the workmen had been told to begin digging.[23] there is no doubt that, were such a system as that proposed established, an enormous amount of time would be saved to the community. "a letter from charing cross to liverpool street," says _the world's work_, "occupies by post three hours; by tube transit it would occupy twenty to forty minutes, or by an express system of tube transit ten to fifteen minutes. express messages carried by the post office in london last year (1903) numbered about a million and a half, but the cost sometimes seems very heavy. to send a special message by hand from hampstead to fleet street, for example, costs 1s. 3d., and takes about an hour. it is claimed that it could be sent by pneumatic tube at a cost of 3d. in from fifteen to twenty minutes, and that for local service the tube would be far quicker than the telegraph, and many times cheaper." it has been calculated that from one-sixth to one-quarter of the wheeled traffic of london is occupied with the distribution of mails and parcels; and if the tubes relieved the streets to this extent, this fact alone would be a strong argument in their favour. it is impossible to believe that tube transmission on a gigantic scale will not come. hitherto its development has been hindered by mechanical difficulties. but these have been mostly removed. in the united states, where the adage "time is money" is lived up to in a manner scarcely known on this side of the atlantic, the device has been welcomed for public libraries, warehouses, railway depã´ts, factories--in short, for all purposes where the employment of human messengers means delay and uncertainty. twenty years ago berlier proposed to connect london and paris by tubes of a diameter equal to that of the pipes contemplated in the scheme now before parliament. our descendants may see the tubes laid; for when once a system of transportation has been proved efficient on a large scale its development soon assumes huge proportions. and even the present generation may witness the tubes of our big cities lengthen their octopus arms till town and town are in direct communication. after all it is merely a question of "will it pay?" we have the _means_ of uniting edinburgh and london by tube as effectually as by telephone or telegraph. and since the general trend of modern commerce is to bring the article to the customer rather than to give the customer the trouble of going to select the article _in situ_--this applies, of course, to small portable things only--"shopping from a distance" will come into greater favour, and the pneumatic tube will be recognised as a valuable ally. we can imagine that mrs. robinson of, say, reading, will be glad to be spared the fatigue of a journey to regent street when a short conversation over the telephone wires is sufficient to bring to her door, within an hour, a selection of silver ware from which to choose a wedding present. and her husband, whose car has perhaps broken a rod at newbury, will be equally glad of the quick delivery of a duplicate part from the makers. these are only two possible instances, which do not claim to be typical or particularly striking. if you sit down and consider what an immense amount of time and expense could be saved to you in the course of a year by a "lightning despatch," you will soon come to the conclusion that the pneumatic tube has a great future before it. footnote: [23] _cassier's magazine_, xiii, 456. chapter xxiii an electric postal system far swifter than the movements of air are those of the electric current, which travels many thousands of miles in a second of time. thirty miles an hour is the speed proposed for the pneumatic tube system mentioned in our last chapter. an italian, count roberto taeggi piscicelli, has elaborated an electric post which, if realised, will make such a velocity as that seem very slow motion indeed. cable railways, for the transmission of minerals, are in very common use all over the world. at hong-kong and elsewhere they do good service for the transport of human beings. the car or truck is hauled along a stout steel cable, supported at intervals on strong poles of wood or metal, by an endless rope wound off and on to a steam-driven drum at one end of the line, or motion is imparted to it by a motor, which picks up current as it goes from the cable itself and other wires with which contact is made. count piscicelli's electric post is an adaptation of the electric cableway to the needs of parcel and letter distribution. at present the mail service between towns is entirely dependent on the railway for considerable distances, and on motors and horsed vehicles in cases where only a comparatively few miles intervene. london and birmingham, to take an instance, are served by seven despatches each way every twenty-four hours. a letter sent from london in the morning would, under the most favourable conditions, not bring an answer the same day--at least, not during business hours. so that urgent correspondence must be conducted over either the telephone or the telegraph wires. count piscicelli proposes a network of light cableways--four lines on a single set of supports--between the great towns of britain. each line--or rather track--consists of four wires, two above and two below, each pair on the same level. the upper pair form the run-way for the two main wheels of the carrier; the lower pair are for the trailing wheels. three of the wires supply the three-phase current which drives the carrier; the fourth operates the automatic switches installed every three or four miles for transforming the high-tension 5,000-volt current into low-tension 500-volt current in the section just being entered. the carriers would be suitable for letters, book-parcels, and light packages. the speed at which they would move--150 miles per hour to begin with--would render possible a ten-minute service between, say, the towns already mentioned. the inventor has hopes of increasing the speed to 250 m.p.h., a velocity which would appear visionary had we not already before us the fact that an electric car, weighing many tons, has already been sent over the berlin-zossen railway at 131-1/2 miles per hour. at any rate, the electric post can reasonably be expected to outstrip the ordinary express train. "should such speeds as count piscicelli confidently discusses," says _the world's work_, "be attained, they would undoubtedly confer immense benefits upon the mercantile and agricultural community--upon the agricultural community because in this system is to be found that avenue of transmission to big centres of population of the products of _la petite culture_, in which mr. rider haggard, for example, in his invaluable book on _rural england_, sees help for the farmer and for all connected with the cultivation of the soil. count piscicelli proposes to obviate the delays at despatching and receiving towns by an inter-urban postal system, in which the principal offices of any city would be connected with the head-office and with the principal railway termini. from each of the sub-offices would radiate further lines, along which post-collecting pillars are erected, and over which lighter motors and collecting boxes (similar to the despatch boxes) travel. the letter is put in through a slot and the stamp cancelled by an automatic apparatus with the name of the district, number of the post, and time of posting. the letter then falls into a box at the foot of the column. on the approach of a collecting-box the letter slot would be closed, and by means of an electric motor the receptacle containing the letters lifted to the top of the column and its contents deposited in the collecting-box, which travels alone past other post-collecting poles, taking from each its toll, and so on to the district office. here, in a mercantile centre, a first sorting takes place, local letters being retained for distribution by postmen, and other boxes carry their respective loads to the different railway termini, or central office." were such an order of things established, there would be a good excuse for the old country woman who sat watching the telegraph wire for the passage of a pair of boots she was sending to her son in far away "lunnon"! chapter xxiv agricultural machinery ploughs--drills and seeders--reaping machines--threshing machines--petrol-driven field machinery--electrical farming machinery agriculture is at once the oldest and most important of all national industries. man being a graminivorous animal--witness his molar, or grinding, "double" teeth--has, since the earliest times, been obliged to observe the seasons, planting his crops when the ground is moist, and reaping them when the weather is warm and dry. apart from the nomad races of the deserts and steppes, who find their chief subsistence in the products of the date-palm and of their flocks and herds, all nations cultivate a large portion of the country which they inhabit. ancient monuments, the oldest inscriptions and writings, bear witness to the prime importance of the plough and reaping-hook; and it may be reasonably assumed that the progress of civilisation is proved by the increased use of cereal foods, and better methods of garnering and preparing them. for thousands of years the sickle, which greek and roman artists placed in the hand of their goddess of the harvest, and the rude plough, consisting of, perhaps, only a crooked bough with a pointed end, were practically the only implements known to the husbandman besides his spade and mattock. where labour is abundant and each householder has time to cultivate the little plot which suffices for the maintenance of his own family, and while there is little inducement to take part in other than agricultural industries--tedious and time-wasting methods have held their own. but in highly civilised communities carrying on manufactures of all sorts it is difficult for the farmer to secure an abundance of human help, and yet it is recognised that a speedy preparation and sowing of the land, and a prompt gathering and threshing of the harvest, is all in favour of producing a successful and well-conditioned crop. in england, eighty years ago, three men lived in the country for every one who lived in the town. now the proportion has been reversed; and that not in the british isles alone. the world does not mean to starve; but civilisation demands that as few people as possible should be devoted to procuring the "staff of life" for both man and beast. we should reasonably expect, therefore, that the immense advance made in mechanical science during the last century should have left a deep mark on agricultural appliances. such an expectation is more than justified; for are there not many among us who have seen the sickle and the flail at work where now the "self-binder" and threshing machine perform the same duties in a fraction of the time formerly required? the ploughman, plodding sturdily down the furrow behind his clever team, is indeed still a common sight; but in the tilling season do we not hear the snort of the steam-engine, as its steel rope tears a six-furrow plough through the mellow earth? when the harvest comes we realise even more clearly how largely machinery has supplanted man; while in the processes of separating the grain from its straw the human element plays an even smaller part. it would not be too much to say that, were we to revert next year to the practices of our grandfathers, we should starve in the year following. this chapter will be confined to a consideration of machinery operated by horse, steam, or other power, which falls under four main headings,--ploughs, drills, reapers, and threshers. ploughs the firm of messrs. john fowler and company, of leeds, is most intimately connected with the introduction of the steam plough and cultivator. their first type of outfit included one engine only, the traversing of the plough across the field being effected by means of cables passing round a pulley on a low, four-wheeled truck, moved along the opposite edge of the field by ropes dragging on an anchor. another method was to have the engine stationary at one corner of the field, and an anchor at each of the three other corners, the two at the ends of the furrow being moved for every journey of the plough. in, or about, the year 1865 this arrangement succumbed to the simple and, as it now seems to us, obvious improvement of introducing a second engine to progress vis-ã -vis with the first, and do its share of the pulling. the modern eight-furrow steam plough will turn ten acres a day quite easily, at a much lower cost than that of horse labour. for tearing up land after a crop "cultivators" are sometimes used. they have arrowhead-shaped coulters, which cut very deep and bring large quantities of fresh earth to the surface. the ground is now pulverised by harrows of various shapes, according to the nature of the crop to be sown. english farmers generally employ the spike harrow; but yankee agriculturists make great use of the spring-tooth form, which may best be described as an arrangement of very strong springs much resembling in outline the springs of house bells. the shorter arm is attached to the frame, while the longer and pointed arm tears the earth. drills and seeders in highly civilised countries the man carrying a basket from which he flings seeds broadcast is a very rare sight indeed. the primitive method may have been effective--a good sower could cover an acre evenly with half a pint of turnip seed--but very slow. we now use a long bin mounted on wheels, which revolves discs inside the bin, furnished with tiny spoons round the periphery to scoop small quantities of seed into tubes terminating in a coulter. the farmer is thus certain of having evenly planted and parallel rows of grain, which in the early spring, when the sprouting begins, make so pleasant an addition to the landscape. the "corn," or maize, crop of the united states is so important that it demands special sowing machinery, which plants single grains at intervals of about eighteen inches. a somewhat similar device is used for planting potatoes. passing over the weeding machines, which offer no features of particular interest, we come to the reaping machines, on which a vast amount of ingenuity has been expended. at the beginning of the nineteenth century the royal agricultural society of great britain offered a prize for the introduction of a really useful machine which should replace the scythe and sickle. several machines were brought out, but they did not prove practical enough to attract much attention. cyrus h. mccormick invented in 1831 the reaper, which, with very many improvements added, is to-day employed in all parts of the world. the most noticeable point of this machine was the bar furnished with a row of triangular blades which passed very rapidly to and fro through slots in an equal number of sharp steel points, against which they cut the grain. the to-and-fro action of the cutter-blade was produced by a connecting-rod working on a crank rotated by the wheels carrying the machine. [illustration: a wheat-cutter a "heading reaper" being pushed over a wheat crop by six mules. it cuts off the ears only, leaving the straw standing. the largest machines of this type used in california take swathes 50 feet broad.] the first mccormick reaper did wonders on a virginian farm; other inventors were stimulated; and in 1833 there appeared the hussey reaper, built on somewhat similar lines. for twelve years or so these two machines competed against one another all over the united states; and then mccormick added a raker attachment, which, when sufficient grain had accumulated on the platform, enabled a second man on the machine to sweep it off to be tied up into a sheaf. at the great exhibition held in london in 1851, the judges awarded a special medal to the inventor, reporting that the whole expense of the exhibition would have been well recouped if only the reaper were introduced into england. from france mccormick received the decoration of the legion of honour "for having done more for the cause of agriculture than any man then living." it would be reasonable to expect that, after this public recognition, the mechanical reaper would have been immediately valued at its true worth. "yet no man had more difficulty in introducing his machines than that pioneer inventor of agricultural implements. farmers everywhere were slow to accept it, and manufacturers were unwilling to undertake its manufacture. even after the value of the machine had been demonstrated, everyone seemed to fear that it would break down on rocky and uneven fields; and the inventor had to demonstrate in person to the farmers the practicability of the reapers, and then even guarantee them before the money could be obtained. through all these trying discouragements the persistent inventor passed before he saw any reward for the work that he had spent half a lifetime in perfecting. the ultimate triumph of the inventor may be sufficient reward for his labours and discouragements, but those who would begrudge him the wealth that he subsequently made from his invention should consider some of the difficulties and obstacles he had to overcome in the beginning."[24] in 1858 an attachment was fitted to replace the second passenger on the machine. four men followed behind to tie up the grain as it was shot off the machine. inventors tried to abolish the need for these extra hands by means of a self-binding device. a practical method, employing wire, appeared in 1860; but so great was the trouble caused by stray pieces of the wire getting into threshing and other machinery through which the grain subsequently passed that farmers went back to hand work, until the appleby patent of 1873 replaced wire by twine. words alone would convey little idea of how the corn is collected and encircled with twine; how the knot is tied by an ingenious shuttle mechanism; and how it is thrown out into a set of arms which collect sufficient sheaves to form a "stook" before it lets them fall. so we would advise our readers to take the next chance of examining a modern self-binder, and to persuade the man in charge to give as lucid an explanation as he can of the way in which things are done. popular prejudice having once been conquered, the success of the reapers was assured. the year 1870 saw 60,000 in use; by 1885 the output had increased to 250,000; and to-day the manufacture of agricultural labour-saving machines gives employment to over 200,000 people; an equal number being occupied in their transport and sale in all parts of the globe. in california, perhaps more than in any other country, "power" agricultural machinery is seen at its best. great traction-engines here take the place of human labour to an extraordinary extent. the largest, of 50 h.p. and upwards, "with driving-wheels 60 inches in diameter and flanges of generous width, travel over the uneven surface of the grain fields, crossing ditches and low places, and ascending the sides of steep hills, with as much apparent ease as a locomotive rolls along its steel rails. such powerful traction-engines, or 'automobiles' as they are commonly called by the american farmers, are capable of dragging behind them sixteen 10-inch ploughs, four 6-foot harrows, and a drill and seeder. the land is thus ploughed, drilled, and seeded all at one time. from fifty to seventy-five acres of virgin soil can thus be ploughed and planted in a single day. when the harvest comes the engines are again brought into service, and the fields that would ordinarily defy the best efforts of an army of workmen are garnered quickly and easily. the giant harvester is hitched to the traction-engine in place of the ploughs and harrows, and cuts, binds, and stacks the golden wheat from seventy-five acres in a single day. the cutters are 26 feet wide, and they make a clear swathe across the field. some of them thresh, clean, and sack the wheat as fast as it is cut and bound. other traction-engines follow to gather up the sacked wheat, and whole train-loads of it thus move across the field to the granaries or railways of the seaboard or interior." for "dead ripe" crops the "header" is often used in california. instead of being pulled it is _pushed_ by mules, and merely cuts off the heads, leaving the straw to be trampled down by the animals since it has no value. swathes as wide as 50 feet are thus treated, the grain being threshed out while the machine moves. one of the most beautiful, and at the same time useful, crops in the world is that of maize, which feeds not only vast numbers of human beings, but also countless flocks and herds, the latter eating the green stalks as well as the ripened grain. the united states alone produced no less than 2,523,648,312 bushels of this cereal in 1902, as against 987,000,000 bushels of wheat, and 670,000,000 bushels of barley. now, maize has a very tough stalk, often 10 feet high and an inch thick, which cannot be cut with the ease of wheat or barley. so a special machine has been devised to handle it. the row of corn is picked up, if fallen, by chains furnished with projecting spikes working at an angle to the perpendicular, so as to lift and simultaneously pull back the stalks, which pass into a horizontal v-shaped frame. this has a broad opening in front, but narrows towards its rear end, where stationary sickles fixed on either side give the stalk a drawing cut before it reaches the single knife moving to right and left in the angle of the v, which severs the stalk completely. the mccormick machine gathers the corn in vertical bundles, and ties them up ready for the "shockers." threshing machines in principle these are simple enough. the straw and grain is fed into a slot and pulled down between a toothed rotating drum and a fixed toothed concave. these tear out the grain from the ear. the former falls into the hopper of a winnowing and riddling machine, which clears it from dust and husks, and allows it to pass to a hopper. an endless chain of buckets carries it to the delivery bins, holding just one sackful each, which when full discharge the grain through spouts into the receptacles waiting below their mouths. an automatic counter records the number of sackfuls of corn that have been discharged, so that dishonesty on the part of employã©s becomes practically an impossibility. while the grain is thus treated, oscillating rakes have arranged the straw and shaken it out behind in a form convenient for binding, and the chaff has passed to its proper heap, to be used as fuel for the engine or as food for cattle. petrol-driven field machinery on water, rail, and road the petrol engine has entered into rivalry with steam--very successfully too. and now it bids fair to challenge both steam-engine and horse as the motive power for agricultural operations. probably the best-known english petrol-driven farmer's help is that made by mr. dan albone, of biggleswade, who in past times did much to introduce the safety bicycle to the public. the "ivel" motor is not beautiful to look upon; its sides are slab, its outlines rather suggestive of an inverted punt. but it is a willing and powerful worker; requires no feeding in the early hours of the morning; no careful brush down after the day's work; no halts to ease wearied muscles. in one tank is petrol, in another lubricating oil, in a third water to keep the cylinders cool. a double-cylinder motor of 18 h.p. transmits its energy through a large clutch and train of cogs to the road wheels, made extra wide and well corrugated so that they shall not sink into soft ground or slip on hard. there is a broad pulley-wheel peeping out from one side of the machine, which is ready to drive chaff-cutters or threshers, pump, grind corn, or turn a dynamo at a moment's notice. [illustration: a motor plough the "ivel" agricultural motor pulling a three-furrow plough. a motor thus harnessed will plough six acres a day at a total cost per acre of five shillings. it is also available for reaping, threshing, chaff-cutting, and other duties on a farm.] hitch the "ivel" on to a couple of reapers or a three-furrow plough, and it soon shows its superiority to "man's friend." here are some records:-eleven acres, one rood, thirteen poles of wet loam land ploughed in 17-1/2 hours, at a cost per acre of 5s. nineteen acres of wheat reaped and bound in 10 hours, at a cost of 1s. 9d. per acre. fifteen acres, three roods of heavy grass cut in 3-1/2 hours, cost, 1s. per acre. with horses the average cost of ploughing is about 10s. an acre; of reaping 5s. so that the motor does at least twice the work for the same money. we may quote a paragraph from the pen of "home counties," a well-known and perspicacious writer on agricultural topics. "it is because motor-farming is likely to result in a more thorough cultivation of the land and a more skilful and more enlightened practice of agriculture, and not in a further extension of those deplorable land-scratching and acre-grasping methods of which so many pitiful examples may be seen on our clay soils, that its beginnings are being sympathetically watched by many people who have the best interests of the rural districts and the prosperity of agriculture at heart."[25] will our farmers give the same welcome to the agricultural motor that was formerly accorded to the mechanical reaper? prophecy is risky, but if, before a decade has elapsed, the horse has not been largely replaced by petrol on large farms and light land, the writer of these lines will be much surprised. electrical farming machinery in france, germany, austria, and the united states the electric motor has been turned to agricultural uses. where water-power is available it is peculiarly suitable for stationary work, such as threshing, chaff-cutting, root-slicing, grinding, etc. the current can be easily distributed all over a large farm and harnessed to portable motors. even ploughing has been done with electricity: the energy being derived either from a steam-engine placed near by, or from an overhead supply passing to the plough through trolley arms similar to those used on electric trams. the great advances made recently in electrical power transmission, and in the efficiency of the electric motor, bring the day in sight when on large properties the fields will be girt about by cables and poles as permanent fixtures. all the usual agricultural operations of ploughing, drilling, and reaping will then be independent of horses, or of steam-engines panting laboriously on the headlands. in fact, the experiment has been tried with success in the united states. whichever way we look, giant steam is bowing before a superior power. footnotes: [24] _cassier's magazine._ [25] _the world's work_, vol. iii. 499. chapter xxv dairy machinery milking machines--cream separators--a machine for drying milk milking machines the farm labourer, perched on a three-legged stool, his head leaning against the soft flank of a cow as he squirts the milk in snowy jets into the frothing pail, is, like the blacksmith's forge throwing out its fiery spark-shower, one of those sights which from childhood up exercise a mild fascination over the onlooker. possibly he or she may be an interested person in more senses than one, if the contents of the pail are ultimately to provide a refreshing drink, for milk never looks so tempting as when it carries its natural froth. modern methods of dairying demand the most scrupulous cleanliness in all processes. pails, pans, and "churns" should be scoured until their shining surfaces suggest that on them the tiniest microbe could not find a footing. buildings must be well aired, scrubbed, and treated occasionally with disinfectants. even then danger may lurk unseen, and the milk is therefore for certain purposes sterilised by heating it to a temperature approaching boiling-point and simultaneously agitating it mechanically to prevent the formation of a scum on the surface. it is then poured into sealed bottles which bid defiance to exterior noxious germs. the human hand, even if washed frequently, is a difficult thing to keep scientifically clean. the milkman has to put his hand now on the cow's side, now on his stool; in short, he is constantly touching surfaces which cannot be guaranteed germless. he may, therefore, infect the teats, which in turn infect the milk. so that, for health's sake as well as to minimise the labour and expense of milking, various devices have been tried for mechanically extracting the fluid from the udder. many of these have died quick deaths, on account of their practical imperfections. but one, at least, may be pronounced a success--the lawrence-kennedy cow-milker, which is worked by electricity, and supplies another proof of the adaptability of the "mysterious fluid" to the service of man. on the isle de la loge in the seine is a dairy farm which is most up-to-date in its employment of labour-saving appliances, including that just mentioned. here a turbine generates power to work vacuum pumps of large capacity. the pumps are connected to tubes terminating in cone-shaped rubber caps that can be easily slipped on to the teat; four caps branching out from a single suction chamber. as soon as they have been adjusted, the milkman--now shorn of a great part of his rights to that title--turns on the vacuum cock, and the pulsator, a device to imitate the periodic action of hand milking, commences to work. the number of pulsations per minute can be regulated to a nicety by adjusting screws. on its way to the pail the milk passes through a glass tube, so that the operator may see when the milking is completed. this method eliminates the danger of hand contamination. it also protects the milk entirely from the air, and it has been stated that, when thus extracted, milk keeps sweet for a much longer time than under the old system. the cows apparently do not object to machinery replacing man, not even the jersey breed, which are the most fidgety of all the tribe. under the heading of economy the user scores heavily, for a single attendant can adjust and watch a number of mechanical milkers, whereas "one man, one cow" must be the rule where the hand is used. from the point of romance, the world may lose; the vacuum pump cannot vie with the pretty milkmaid of the songs. practical people will, however, rest content with pure milk _minus_ the beauty, in preference to milk _plus_ the microbe and the milkmaid, who--especially when she is a man--is not always so very beautiful after all. cream separators in the matter of separating the fatty from the watery elements of milk machinery also plays a part. the custom of allowing the cream to "rise" in open pans suffices for small dairies where speed and thoroughness of separation are not of primary importance. but when cream is required in wholesale quantities for the markets of large towns, or for conversion into butter, much greater expedition is needed. the mechanical cream separator takes advantage of the laws of centrifugal force. milk is poured into a bowl rotating at high speed on a vertical axis. the heavier--watery--portions climb up the sides of the bowl in their endeavour to get as far away as possible from the centre of motion; while the lighter particles of cream, not having so much momentum, are compelled to remain at the bottom. by a simple mechanical arrangement, the--very--skim milk is forced out of one tube, and the cream out of another. an efficient separator removes up to 99 per cent. of the butter fat. small sizes, worked by hand, treat from 10 to 100 gallons of milk per hour; while the large machines, extensively used in "creameries," and turned by horse, steam, electric, or other power, have a capacity of 450 gallons per hour. the saving effected by mechanical methods of separation is so great that dairy-farmers can now make a good profit on butter which formerly scarcely covered out-of-pocket expenses incurred in its manufacture. a machine for drying milk milk contains 87 per cent. of water and about 12 per cent. of nutritive matter. milk which has had the water evaporated from it becomes a highly concentrated food, very valuable for many purposes which could not be served by the natural fluid. until lately the process of separating the solid and liquid constituents was too costly to render the manufacture of "dried milk" a profitable industry. but now there is on the market a drying apparatus, manufactured by messrs. james milnes and son, of edinburgh, which almost instantaneously drives off the water. the machine used for this--the just-hatmaker--process is simple. it consists of two large metal drums, 28 inches in diameter and 5 feet long, mounted horizontally in a framework with a space of about one-eighth of an inch between them. high-pressure steam, admitted to the drums through axial pipes, raises their surfaces to a temperature of 220â° fahr. the milk is allowed to flow in thin streams over the revolving drums, the heat of which quickly evaporates the water. a coating of solid matter gradually forms, and this is scraped off by a knife and falls into a receptacle. the milk is not boiled nor chemically altered in any way, though completely sterilised by the heat. this machine promises to revolutionise the milk trade, as farmers will now be able to convert the very perishable product of their dairies into an easily handled and imperishable powder of great use for cooking and the manufacture of sweetmeats. explorers and soldiers can have their milk supply reduced to tabloid form, and a pound tin of the lozenges will temper their tea or coffee over many a camp fire far removed from the domestic cow. chapter xxvi sculpturing machines the savage who, with a flint point or bone splinter, laboriously scratched rude figures on the walls of his cave dwelling, did the best he was capable of to express the emotions which affect the splendidly equipped sculptor of to-day; he wished to record permanently some shape in which for the time he was interested, religiously or otherwise. the sun, moon and stars figure largely in primitive religions as objects of worship. they could be easily suggested by a few strokes of a tool. but when mortals turned from celestial to terrestrial bodies, and to the worship of human or animal forms--the "graven images" of the bible--a much higher level of art was reached by the sculptor, who endeavoured to give faithful representations in marble of the great men of the time and of the gods which his nation acknowledged. the egyptians, whose colossal monuments strew the banks of the nile, worked in the most stubborn materials--basalt, porphyry and granite--which would turn the edge of highly tempered steel, and therefore raise wonder in our minds as to the nature of the tools which the subjects of the pharaohs must have possessed. only one chisel, of a bronze so soft that its edge turned at the first stroke against the rock under which it was found, has so far come to light. of steel tools there is no trace, and we are left to the surmise that the ancients possessed some forgotten method of hardening other metals--including bronze--to a pitch quite unattainable to-day. whatever were their implements, they did magnificent work; witness the splendid sculptures of vast proportions to be found in the british museum; and the yet huger statues, such as those of memnon and those at karnak, which attract tourists yearly to egypt. the egyptians admired magnitude; the greeks perfection of outline. the human form in its most ideal development, so often found among a nation with whom athleticism was almost a religion, inspired many of the great classical sculptors, whose work never has been, and probably never will be, surpassed. great honour awaited the winner in the olympian games; but the most coveted prize of all was the permission given him--this after a succession of victories only--to erect a statue of himself in the sacred grove near the shrine of olympian jove. happy the man who knew that succeeding generations would gaze upon a marble representation of some characteristic attitude assumed by him during his struggle for the laurel crown. until recently the methods of sculpture have remained practically unaltered for thousands of years. the artist first models his idea in clay or wax, on a small scale. he then, if he designs a life-size or colossal statue, erects a kind of iron skeleton to carry the clay of the full-sized model, copied proportionately from the smaller one. when this is finished, a piece-mould is formed from it by applying wet lumps of plaster of paris all over the surface in such a manner that they can be removed piecemeal, and fitted together to form a complete mould. into this liquid plaster is run, for a hollow cast of the whole figure, which is smoothed and given its finishing touches by the master hand. this cast has next to be reproduced in marble. both the cast and the block of marble are set up on "scale-stones," revolving on vertical pivots. an ingenious instrument, called a "pointing machine," now comes into play. it has two arms ending in fine metal points, movable in ball-and-socket joints. these arms are first applied to the model, the lower being adjusted to touch a mark on the scale-stone, the upper to just reach a mark on the figure. the operator then clamps the arms and revolves the machine towards the block of marble, the scale-stone of which has been marked similarly to its fellow. the bottom arm is now set to rest on the corresponding mark of the scale-stone; but the upper, which can slide back telescopically, is prevented from assuming its relative position by the unremoved portions of the block. the workman therefore merely notices the point on the block at which the needle is directed, and drills a hole into the marble on the line of the needle's axis, to a depth sufficient to allow the arm to be fully extended. this process is repeated, in some cases many thousands of times, until the block has been honeycombed with small holes. the carver can now strike off the superfluous marble, never going beyond the depth of a hole; and a rough outline of the statue appears. a more skilled workman follows him to shape the material to a close copy of the cast; and the sculptor himself adds the finishing touches which stamp his personality on the completed work. only a select few of the world's greatest sculptors have ventured to strike their statues direct from the marble, without recourse to a preliminary model. such a one was michelangelo, who, as though seized by a creative frenzy, would hew and hack a block so furiously that the chips flew off like a shower, continuing his attack for hours, yet never making the single false stroke that in the case of other masters has ruined the work of months. he truly was a genius, and must have possessed an almost supernatural faculty of knowing when he had reached the exact depth at any point in the great block of marble from which his design gradually emerged. the formation of artistic _models_ will always require the master's hand; but the _reproduction_ of the cast in marble or stone can now be performed much more expeditiously than is possible with the pointing machine. we have already two successful mechanisms which in an almost incredibly short time will eat a statue out of a block in faithful obedience to the movement of a pointer over the surface of a finished design. they are the wenzel machine sculptor and signor augusto bontempi's _meccaneglofo_. the wenzel sculpturing machine in the basement of a large london business house we found, one dark november afternoon, two men at work with curious-looking frameworks, which they swayed backwards and forwards, up and down, to the accompaniment of a continuous clattering of metal upon stone. approaching nearer, we saw, lying horizontally in the centre of the machine, a small marble statue, its feet clamped to a plate with deep notches in the circumference. on either side, at equal distances, were two horizontal blocks of marble similarly attached to similar plates. the workman had his eyes glued on a blunt-nosed pointer projecting from the middle of a balanced frame. this he passed slowly over the surface of the statue, and simultaneously two whirring drills also attached to the frame ate into the stone blocks just so far as the movement of the frame would permit. the drills were driven by electric power and made some thousands of revolutions per minute, throwing off the stone they bit away in the form of an exceedingly fine white dust. it was most fascinating to watch the almost sentient performance of the drills. just as a pencil in an artist's hands weaves line into line until they all suddenly spring into life and show their meaning, so did the drills chase apparently arbitrary grooves which united, spread, and finally revealed the rough-hewn limb. every now and then the machinist twisted the footplates round one notch, and snicked the retaining bolts into them. this exposed a fresh area of the statue and of the blocks to the pointer and the drills. the large, coarse drills used to clear away the superfluous material during the earlier stages of the work were replaced by finer points. the low relief was scooped out, the limbs moulded, the delicate curves of cheek and the pencilling of eyebrows and lips traced, and in a few hours the copies were ready for the usual smoothing and finishing at the hands of the human sculptor. according to the capacity of the machine two, four, or six duplicates can be made at the cost of a little more power and time. nor is it necessary to confine operations to stone and marble, for we were shown some admirable examples of wooden statues copied from a delicate little bronze, and, were special drills provided, the relations could be reversed, bronze becoming passive to motions controlled by a wooden original. "sculpturing made easy" would be a tempting legend to write over the wenzel machine. but it would not represent the truth. after all, the mechanism only _copies_, it cannot originate, which is the function of the sculptor. it stands to sculpturing in the same relation as the printer's "process block" to the artist's original sketch, or the lithographic plates to the painter's coloured picture. therefore prejudice against machine-made statues is as unreasonable as objection to the carefully-executed _replica_ of a celebrated painting. the sculptor himself has not produced it at first hand, yet his personality has been stamped even on the copy, for the machine can do nothing except what has already been done for it. the machine merely displaces the old and imperfect "pointing" by hand, substituting a method which is cheaper, quicker, and more accurate in its interpretation of the model. it is obvious that, apart from sculpture proper, the industrial arts afford a wide field for this invention. in architecture, for instance, carved wood and stonework for interiors and exteriors of buildings have been regarded hitherto as expensive luxuries, yet in spite of their cost they are increasingly indulged in. the architect now has at his disposal an economical method of carving which will enable him to utilise ornamental stonework to almost any degree. sculptured friezes, cornices, and capitals, which, under the old rã©gime, would represent months of highly paid hand labour, may now be reproduced rapidly and in any quantity by the machine, which could be adapted to work on the scaffolding itself. what will become of the stonemasons? won't they all be thrown out of work, or at least a large number of them? the best answer to these questions will be found in a consideration of industries in which machinery has replaced hand work. has england, as a cotton-spinning nation, benefited because the power-loom was introduced? does she employ more operatives than she would otherwise have done, and are these better paid than the old hand weavers? all these queries must have "yes!" written against them. in like manner, if statuary and decoration becomes inexpensive, twenty people will be able to afford what hitherto was within the reach of but one; and an industry will arise beside which the output of the present-day monumental mason will appear very insignificant. the sculpturing machine undoubtedly brings us one step nearer the universal house beautiful. a complete list of the things which the versatile "wenzel" can perform would be tediously long. let it therefore suffice to mention boot-lasts, gun-stocks, moulds, engineering patterns, numeral letters, and other articles of irregular shape, as some of the more prosaic productions which grow under the buzzing metal points. some readers may be glad to hear that the wenzel promises another hobby for the individual who likes to "use his hands," since miniature machines are purchasable which treat subjects of a size not exceeding six inches in diameter. no previous knowledge of carving is necessary, and as soon as the elementary principles have been mastered the possessor of a small copier can take advantage of wet days to turn out statuettes, busts, and ornamental patterns for his own or friends' mantelpieces. and surely a carefully finished copy in white marble of some dainty classic figure or group will be a gift well worth receiving! the amateur photographer, the fret-sawyer, and the chip-carver will have to write "ichabod" over their workshops! the wenzel has left its experimental stage far behind. the german emperor, after watching the creation of a miniature bust of beethoven, expressed his delight in a machine that could call a musician from lifeless stone. the whole of the interior decoration of the magnificent rathaus, charlottenburg, offers a splendid example of mechanical wood carving, which tourists would do well to inspect. we may now pass to the bontempi sculpturing machine, for such is the translation of the formidable word _meccaneglofo_. this machine is the invention of signor augusto bontempi, a native of parma, who commenced life as a soldier in the italian army, and while still young has won distinction as a clever engineer. his machine differs in most constructional details from the wenzel. to begin with, the pressure of the drills on the marble is imparted by water instead of by the hand; secondly, the block to be cut is arranged vertically instead of horizontally; thirdly, the index-pointer is not rigidly connected to the drill frame, but merely controls the valves of hydraulic mechanism which guides the drills in any required direction. the drills are _rotated_ by electricity, but all their other movements come from the pressure of water. [illustration: a small wenzel automatic sculpturing machine this cuts statuettes, two at a time, out of stone or wood, the cutters being guided by a pointer passed over the surface of the model by the girl.] undoubtedly the most ingenious feature of the bontempi apparatus is the pointer's hydraulic valve, which gives the drills a forward, lateral, or upward movement, or a compound of two or three movements. when the pointer is not touched all the valve orifices remain closed, and the machine ceases to work. should the operator pull the pointer forwards a water-way is opened, and the liquid passes under great pressure to a cylinder which pushes the drill frame forward. if the pointer be also pressed sideways, a second channel opens and brings a second cylinder into action, and the frame as a whole is moved correspondingly, while an upward twist operates yet a third set of cylinders, and the workman himself rises with the drills. as soon as the sensitive tip of the pointer touches an object it telescopes, and immediately closes the valves, so that the drills bore no further in that direction. the original and copies are turned about from time to time on their bases in a manner similar to that already described in treating the wenzel. as many as twenty copies can be made on the largest machines. quite recently there has been installed in southwark, london, a gigantic bontempi which stands 27 feet high, and handles blocks 5 feet 6 inches square by 10 feet high, and some 20 tons in weight. owing to the huge masses to be worked only one copy can be made at a time; though, doubtless, if circumstances warranted the expense, a machine could be built to do double, triple, or quadruple duty. the proprietors have discovered an abrasive to grind granite--ordinary steel chisels would be useless--and they expect a great demand for columns and monumental work in this stubborn material, as their machines turn out finished stuff a dozen times faster than the mason. an interesting story is told about the early days of signor bontempi's invention. when he set up his experimental machine at florence, the workmen, following the example of the luddites, rose in a body and threatened both him and his apparatus with destruction. the police had to be called in to protect the inventor, who thought it prudent to move his workshop to naples, where the populace had broader-minded views. the florentines are now sorry that they drove signor bontempi away, for they find that instead of depressing the labour market, the mechanical sculptor is a very good friend to both proprietor and employã©. note.--for information and illustrations the author has to thank mr. w. hanson boorne, of the machine sculpture company, aldermary house, london, e.c., and mr. e. w. gaz, secretary of the automatic sculpture syndicate, sumner street, southwark. chapter xxvii an automatic rifle while science works ceaselessly to cure the ills that human flesh is heir to, invention as persistently devises weapons for man's destruction. yesterday it was the discoveries of pasteur and the maxim gun; to-day it is the finsen rays and the rexer automatic rifle. though one cannot restrain a sigh on examining a new contrivance, the sole function of which is to deal out death and desolation--sadly wondering why such ingenuity might not have been directed to the perfecting of a machine which would render life more easy and more pleasant; yet from a book which deals with modern mechanisms we may not entirely exclude reference to a class of engines on which man has expended so much thought ever since gunpowder first entered the arena of human strife. we therefore choose as our subject for this chapter a weapon hailing from denmark, a country which, though small in area, contains many inventors of no mean repute. in a london office, within sight of the monument raised to england's great sailor hero, the writer first made acquaintance with the rexer gun, which, venomous device that it is, can spit forth death 300 times a minute, though it weighs only about 18 lbs. its form is that of an ordinary rifle of somewhat clumsy build. the eye at once picks out a pair of supports which project from a ring encircling it near the muzzle. even a strong man would find 18 lbs. too much to hold to his shoulder for any length of time; so the rexer is primarily intended for stationary work. the user lies prone, rests the muzzle on its supports, presses the butt to his shoulder, and blazes away. history repeats itself in the chronicles of firearms, though it is a very long way from the old matchlock supported on a forked stick to the latest thing in rifles propped up by two steel legs. machine-guns, such as the maxim and hotchkiss, weigh 60 lbs. and upwards, and have to be carried on a wheeled carriage, drawn either by horses or by a number of men. in very rough country they must be loaded on pack-horses or mules. when required for action, the gun, its supports and appliances, separated for packing, must be hurriedly reassembled. this means loss of valuable time. the rexer rifle can be carried almost as easily as a lee-metford or mauser, and fires the ordinary small-bore ammunition. wherever infantry or cavalry can go, it can go too, without entailing any appreciable amount of extra haulage. before dealing with its actual use as a fighting arm we will notice the leading features of its construction. the gun comprises the stock, the casing and trigger-plate which enclose the breech mechanism, the barrel, and the perforated barrel cover, to which are attached the forked legs on which the muzzle end is supported when firing, and which fold up under the cover when not in use. the power for working the mechanism is obtained from the recoil, which, when the gun is fired, drives the barrel, together with the breech and the other moving parts, some two inches backwards, thus compressing the powerful recoil-spring which lies behind the breech, enclosed in the front part of the stock, and which, after the force of the recoil is spent, expands, and thus drives the barrel forward again into the firing position. the recoil and return of the breech operate a set of levers and other working parts within the casing, which, by their combined actions following one another in fixed order, open the breech, eject the empty cartridge-case, insert a new cartridge into the chamber, and close the breech; and when the gun is set for automatic action, and the gunner keeps his finger pressed on the trigger, the percussion arm strikes the hammer and the cartridge is fired; the round of operations repeating itself till the magazine is emptied, or until the gunner releases the trigger and thereby interrupts the firing. a noticeable feature is the steel tube surrounding the barrel. it is pierced with a number of openings to permit a circulation of air to cool the barrel, which is furnished with fins similar to those on the cylinder of an air-cooled petrol motor to help dissipate the heat caused by the frequent explosions. near the ends of the cover are the guides, in which the barrel moves backwards and forwards under the influence of the recoil and the recoil-spring. the supports are attached to the casing in such a way that the stock of the gun can be elevated or depressed and traversed through considerable angles without altering the position of the supports on the ground. the rear end of the barrel cover is firmly fixed to the casing of the breech mechanism, and forms with this and the stock the rigid part of the gun in which the moving portions work, their motions being guided and controlled by cams and studs working in grooves and notches and on blocks attached to the rigid parts. without the aid of special diagrams it is rather hard to explain the working of even a simple mechanism; but the writer hopes that the following verbal description, for which he has to thank the rexer company, will at least go some way towards elucidating the action of the breech components. inside the casing is the breech, the front end of which is attached rigidly to the barrel, the rear end being in contact with the recoil arm, which is directly operated by the recoil spring lying in a recess in the stock. in the breech is the breech-block, which has three functions: first to guide the new cartridges from the distributer, which passes them from the magazine one by one into the casing, to the firing position in the chamber (_i.e._ the expanded part of the bore at the rear end of the barrel); secondly, to hold the cartridge firmly fixed in the chamber, and to act as an abutment or support to the back of the cartridge when it is fired, and thus transmit the backward force of the explosion to the recoil spring; thirdly, to allow the spent cartridges to be discharged from the chamber by the extractor, and to direct them by means of a guide curved downwards from the chamber, so that they may be flung through an opening provided for that purpose in the trigger-plate in front of the trigger, and out of the way of the gunner. (this opening is closed by a cover when the gun is not in use, and opens automatically before the shot can be fired.) in order to effect this threefold object, the breech-block is pivoted in the rear to the rear of the breech, and has a vertical angular motion within it, so that the fore end of the block can move into three different positions in relation to the chamber: one, below the chamber to guide the cartridge into it; one, directly in line with the chamber, to back the cartridge; and one, above the chamber, to allow the ejection of the spent cartridge-case by the extractor. the cartridge is fired by a long pin through the breech-block, struck behind by a hammer operated by a special spring. the first function of the breech-block is, as we have said, to act as a guide for the cartridge into the chamber ready for firing, after the fashion of the old martini-henry breech-block. the actual pushing forward of the cartridge is performed by a lever sliding on the top of the block. after the explosion a small vertical lever jerks out the cartridge-case against the block, and causes it to cannon downwards through the aperture in the trigger-plate already mentioned. on the left-hand side of the breech casing is a small chamber, open at the top and on the side next the breech. to the top is clipped the magazine, filled with twenty-five cartridges. the magazine is shaped somewhat like a slice of melon, only that the curved back and front are parallel. the sides converge towards the inner edge. it is closed at the lower end by a spring secured by a catch. when a magazine is attached to the open top of the chamber the catch is released so as to put chamber and magazine in direct communication. the cartridges would then be able to drop straight into the breech chamber through the side slot, were the latter not protected by a curved horizontal shutter, called the distributer. its action is such that when a cartridge is being passed through into the breech casing, the shutter closes, and holds the remaining cartridges in the magazine; and when the cartridge has passed it opens and lets the next into position in the side casing. as soon as a cartridge enters the breech it is pushed forward into the chamber ready for firing by the feeder lever. the magazine and the holder are so arranged that when the last cartridge has passed from the magazine to the distributer, the motion of the moving parts of the gun is arrested till the magazine is removed, when the motion is resumed so far as to push the remaining cartridge into the chamber and bring the breech-block into the firing position. when another magazine has been fixed in the holder, firing can be resumed by pulling the trigger; but if another magazine is not fixed in the holder the last cartridge cannot be fired by pulling the trigger, and only by pulling a handle which will be presently described. this arrangement secures the continuance of the automatic firing being interrupted only by the very brief interval required for charging the apparatus. the gun is fired, as usual, by pulling a trigger. if a steady pull be kept on the trigger the whole contents of the magazine will be fired automatically (the last cartridge excepted); but if such continuous firing is not desired, a few shots at a time may be fired automatically by alternately pulling and releasing the trigger. if it is desired to fire shot by shot from the magazine, a small swivel on the trigger-guard is moved so as to limit the movement of the trigger. by moving this swivel out of the way, automatic firing is resumed. the gun may also be fired without a magazine by simply feeding cartridges by hand into the magazine holder. in front of the trigger-guard is a safety catch, and if this is set to "safe" the gun cannot be fired until the catch is moved to "fire." it is obvious that the recoil cannot come into action until a shot has been fired. a handle is therefore provided on the right-hand side outside the casing, by means of which the bolt forming the axis of the recoil and percussion arms may be turned so as to imitate the action of the recoil. this handle must be turned to bring the first cartridge into the chamber, but this having been done, the handle returns to its normal position, and need not be moved again. we may now watch a gunner at work. he chooses his position, opens out the supports, and pushes them into the ground so as to give the muzzle end a firm bearing. he then takes a magazine from the box he carries with him, and fixes it by a rapid motion into the magazine holder, then, resting his left hand on the stock to steady it, he pulls over the handle with his right so as to bring the barrel and all the moving mechanism into the backward position. he then releases the handle, and the recoil spring comes into action and drives the breech forward, when the controlling gear brings the front end of the breech-block into its downward position, admits the first cartridge into the breech and pushes it forward by the cartridge-feeder into the barrel chamber. the breech-block then rises to its central position at the back of the cartridge, and the gun is ready for firing. if automatic firing is required, the gunner sets the swivel at the back of the trigger in the right position, sights the object at which he has to fire, and pulls the trigger, thereby exploding the first cartridge. the recoil then drives back the barrel and the breech. the breech-block is moved into its highest position, making room for the ejection of the empty cartridge-case, which is then ejected by the extractor. at the end of the recoil the block falls into its lowest position, the cartridge-feeder having then arrived at the back of the breech-block. the recoil-spring now drives the breech forward, admits the new cartridge on to the breech-block and drives it forward by the feeder into the chamber. the breech-block rises to its position behind the cartridge and is locked in that position. the percussion arm is then released automatically, strikes the hammer, and fires the second cartridge, the cycle of operations repeating itself till the last cartridge but one has been fired, when the magazine is charged and the cycle of operations is again renewed and continued till the second set of cartridges has been fired. the operations follow one another with such rapidity that the twenty-five cartridges contained in the magazine can be fired in less than two seconds. at the same time, the rate of firing remains under the control of the gunner, who can interrupt it at any moment by simply releasing the trigger. he can also alter his aim at any time and keep it directed on a moving object and fire at any suitable moment. [illustration: the "rexer" automatic machine gun it only weighs 17-1/2 lb., and can fire 300 shots per minute. the crescent-shaped clips hold 25 cartridges each, and as soon as one has been emptied another can be affixed in a moment.] in service it is not intended that every man should be armed with a rexer, but only 3 to 5 per cent., constituting a separate detachment which would act independently of the artillery and other machine-guns. the latter would, as at present, cover the infantry's advance up to within some 500 yards of the enemy, but at this point would have to cease firing for fear of hitting their own men. this period, when the artillery can neither shoot over the heads of their infantry, nor bring up the guns for fear of losing the teams, affords the golden opportunity for the rexer, which is advanced with the firing line. if the fire of the detachment were concentrated on a part of the enemy's line, that portion would be unable to reply while the attacking force rushed up to close quarters. one hundred men armed with rexers would be as valuable as several hundred carrying the ordinary service weapon, while they would be much more easily disposed, advanced, or withdrawn. a squadron of cavalry would be accompanied by three troopers armed with rexers and by one leading a pack-horse laden with extra magazines. each gunner would have on his horse 400 cartridges, and the pack-horse 2,400 rounds, distributed in leather cases over a specially designed saddle. when a squadron, not provided with machine-guns, has to open a heavy fire, a considerable proportion must remain behind the firing line to hold the horses of the firing party. when, on the other hand, rexers are present, only a few men would dismount, leaving the main body ready to charge at the opportune moment; and, should the attack fail, they could cover the retreat. a use will also be found for the rexer in fortresses and on war vessels; in fact, everywhere where the machine-gun can take a part. after exhaustive trials, the danish government has adopted this weapon for both army and navy; and it doubtless will presently be included in the armament of other governments. there are signs that the most deadly arm of the future will be the automatic rifle. perhaps a pattern even lighter than the rexer may appear. if every unit of a large force could fire 300 rounds a minute, and ammunition were plentiful, we could hardly imagine an assault in which the attacking party would not be wiped out, even if similarly armed; for with the perfection of firearms the man behind cover gets an ever-increasing advantage over his adversary advancing across the open. a ball-bearing rifle rapidity of fire is only one of the desirable features in a firearm. its range--or perhaps we had better say its muzzle velocity--is of almost equal importance. the greater this is, the flatter is the trajectory or curve described by the bullet, and the more extended the "point blank" range and the "danger zone." take the case of two rifles capable of flinging a bullet one mile and two miles respectively. riflemen seldom fire at objects further off than, say, 1,200 yards; so that you might think that, given correct sighting in the weapon and a positive knowledge of the range, both rifles would have equal chances of making a hit. this is not the fact, however, for the more powerful rifle sends its bullet on a course much more nearly parallel to the ground than does the other. therefore an object six feet high would evidently run greater risks of being hit _somewhere_ by the two-mile rifle than by the one-mile. thus, if at 1,200 yards the bullet had fallen to within six feet of the ground, it might not actually strike earth till it had travelled 1,400 yards; whereas with a lesser velocity and higher curve, the point of impact might be only fifty yards behind. evidently a six-foot man would be in danger anywhere in a belt 200 yards broad were the high-velocity rifle in operation, though the danger zone with the other weapon would be contracted to fifty yards. at close quarters a flat trajectory is even more valuable, since it diminishes the need for altering the sights. if a rifle's point-blank range is up to 600 yards, you can fire at a man's head anywhere within that distance with a good chance of hitting him. the farther he is away, the lower he will be hit. a high trajectory would necessitate an alteration of the sights for every fifty yards beyond, say, two hundred. the velocity of a projectile is increased--(1) by increasing the weight of the driving charge; (2) by decreasing the friction between the barrel and the projectile. an american inventor, mr. orlan c. cullen, has adopted a means already well tried in mechanical engineering to decrease friction. he has produced a rifle, the barrel of which has in its walls eight spiral grooves of almost circular section, a small arc of the circle being cut away so as to put the groove in continuous communication with the bore of the barrel. these grooves are filled with steel balls, one-tenth of an inch in diameter, which are a good fit, and on the slot side of the groove project a very tiny distance into the barrel. the bullet--of hard steel--as it is driven through the barrel does not come into contact with the walls, but runs over the balls, which grip it with sufficient force to give it a spinning motion. the inventor claims that there is no appreciable escape of gas round the bullet, as the space between it and the barrel is so minute. the ball races, or grooves, extend back to the powder chamber and forward to the muzzle. their twist ceases a short distance from the muzzle to permit the insertion of recoil cushions, which break the forces of the balls as they are dragged forward by the bullet. mr. cullen holds that a rifle built on this principle gives 40 per cent. greater velocity than one with fixed rifling--to be exact, has a point-blank range of 650 yards as compared with 480 yards of the lee-metford, and will penetrate 116 planks 1 inch thick each. the absence of friction brings absence of heat, which in the case of machine-guns has always proved a difficulty. it also minimises the recoil, and reduces the weight of mountings for large guns. whether these advantages sufficiently outweigh the disadvantages of complication and cleaning difficulties to render the weapon acceptable to military authorities remains to be seen. we can only say that, if the ball bearing proves as valuable in ballistics as it has in machinery, then its adoption for firearms can be only a matter of time. plymouth: w. brendon and son, ltd., printers. * * * * * transcriber's notes minor typographical errors have been corrected. inconsistent accents, punctuation, and hyphenation are as in the original text unless noted below. the following misprints and misspellings are noted or have been corrected in the text. page 38: superscript "1" changed to an inline fraction "1/8" ("50,000 prick-marks 1/8 inch apart"). page 55: "corp" changed to "corps" ("a corps of inventors"). page 145: "populsion" changed to "propulsion" ("for its own propulsion"). page 173: "searchlight" changed to "search-light" to make the latter usage consistent throughout the book ("when a search-light alone"). page 206: "two" changed to "too" ("the reversal being too sudden"). page 244: according to the 1911 encyclopã¦dia britannica, "kleingert" is the correct spelling of the name of the german who invented the "first practical diving helmet". more modern books, however, use a different spelling, referring to (karl heinrich) klingert. page 250: "saint goubin" changed to "saint gobain" ("by saint gobain, of paris"). page 266: "overburden" changed to "over-burden" to make the latter usage consistent throughout the book ('removing the "over-burden" of surface mines'). other changes to the text. footnotes have been relabeled using numbers then collected together at the end of the chapter in which they appear. this has the consequence that, where the same reference is cited in more than one footnote in a chapter, it can result in a sequence of footnotes with identical text. that is not a transcription error. 