transcriber note emphasis denoted as _italics_. u. s. department of agriculture. farmers' bulletin · no. 43. sewage disposal on the farm, and the protection of drinking water. by theobald smith, m. d., _professor in harvard university, pathologist to the massachusetts state board of health, etc._ [illustration] washington: government printing office. 1896. contents. page. introduction 3 disposal of sewage 5 night soil 7 the privy 7 the cesspool 7 the dry-earth closet 8 the water-closet 11 liquid sewage 11 vaults 11 irrigation 12 kitchen and chamber slops 14 waste and garbage 15 protection of drinking water 16 ways of contamination 17 construction of wells 18 conclusion 19 illustrations. fig. 1. shallow barnyard well 6 2. portable earth closet 8 3. old form of earth closet 9 4. earth closet and dry catch 10 5. self-acting peat dust closet 11 6. settling chamber and flush tank for irrigation 12 7. subsurface irrigation of sewage 13 8. garbage cremator 16 sewage disposal on the farm and the protection of drinking water. introduction. the conditions under which homes and their surroundings are kept healthful in the city and in the country differ in many respects, although the principles underlying them are essentially the same. in the city the sanitary condition of homes is maintained chiefly by a system of cooperation and centralization which brings into existence extensive sewerage systems, water supplies, and the collection of house waste by public authority. regulations are prescribed and enforced under which the individual household must avoid all conditions which are likely to prove dangerous to the health of the immediate neighborhood and of the entire community. in the country districts, and more particularly in isolated homesteads, the conditions affecting the health of the household are largely in its own hands, and more individual effort is required to maintain healthful surroundings than in cities. the farmer must supply himself with his drinking water and must get rid of the waste of the household as best he can. on the other hand, the inhabitant of the country is in many ways better off than the dweller in large cities. not only has he pure air to draw upon at all times, but he can supply himself often with purer food than is possible in large communities. though he must procure for himself drinking water, he is, in most cases, able to get a purer water from the ground than the sewage-polluted fluid which is the only water accessible in many cities. while he must get rid of night soil himself rather than have it disposed of by a water-carriage system conveniently located within the house, he may avoid the annoying complications of plumbing, bringing with it the leakages of sewer gas, the plugging up of soil pipes by the roots of trees or by articles carelessly thrown into them. moreover, he has it often within his power to acquire sufficient land around his house to take charge of all sewage and waste and to utilize it as a manure for enriching the soil. nevertheless, it must be acknowledged that when the circumstances under which healthful surroundings are procurable are under the immediate control of each individual household they are apt to be perverted through ignorance and neglect. conditions may then arise which are not only unfavorable to health, but which are likely to lead to severe sickness at any time when the opportunity presents itself. standing between the fortunate inhabitant of a large city whose water-supply and sewerage systems are above reproach and the farmer who bas it within his power to make them so with reference to his own wants, is the half-developed village or town, with its chiefly unsanitary conditions. here the leaky cesspool still exists, close by the family well, or by the neighbor's well. the absence of any system of collecting garbage and miscellaneous waste shows itself by the littering of the yards, the alleys, streets, and even stream beds with all kinds of refuse. in some towns the premature introduction of a water-supply system causes the ground to become still more thoroughly saturated with diluted sewage, so that the wells of those households not yet connected with the water-supply are a continual source of danger. in such communities, appreciation of the necessity for a public control of sanitation has not yet made much headway. the acts of each family violating the laws of health not only react upon itself but upon the immediate neighborhood, often with disastrous results. when typhoid fever has once gained a foothold in such communities it is apt to develop into an epidemic. the tendency of our population to concentrate in villages and towns makes the sanitary improvement of such communities a most important and vital condition of national health and prosperity. the following pages are not intended for these communities, for they need, in most cases, the advice of sanitarians and sanitary engineers, acquainted with local conditions. still, they may be of service in pointing out the dangers which may and do actually beset the population that neglects to dispose of refuse and waste in a manner which does not clash with the laws of health. the chief dangers which threaten rural inhabitants are those arising from polluted drinking water. this is infected from the household excrement and barnyard drainage, as will be described farther on, and its use leads in the main to bowel disturbances, typhoid-fever, and dysenteric affections. it might be claimed that in an isolated homestead the danger is absent because the night soil from the healthy household can not contain the germs of typhoid-fever, and, therefore, the well water can not receive them from leaky cesspools and surface drainage. this would be true if the family lived secluded from other human beings. as the case stands, there is much more communication than is at first thought supposed. there is more or less coming and going of farm hands and other hired help, of tramps, peddlers, etc. the farmer travels more than formerly. he frequently visits neighboring communities. the children go to school. as it has been shown that there may be mild cases of typhoid-fever passing unnoticed, in a farm hand, for example, who leaves on account of ill health, perhaps, and who has meanwhile, in his discharges, deposited the germs of this disease on the premises, it is evident that isolation nowadays does not exist except in remote, thinly settled regions, and that disease germs may make themselves suddenly felt in an unexpected manner in any farmhouse. there are other important reasons, however, why rural sanitation should not be neglected. the health of the large communities of people who draw their food supply from the country is in a measure dependent on the health of the farming community. there is scarcely a city child who is not, in a degree, dependent for its health on the sanitary conditions prevailing in the house of the dairyman. milk has been repeatedly shown to be the means of distributing typhoid-fever and other diseases. any vegetable foods from the farm eaten raw are liable to become carriers of infection under unsanitary conditions. in many parts of our country other causes operate in making the health of many people depend on the proprieties of country homes. the thousands of city people, who flock every summer to the country and bring to the farming community considerable sums of money, should be properly protected against the dangers of polluted water and infected milk by the adoption of suitable methods of sewage disposal. too frequently those who left the city for the purpose of gaining strength by breathing pure air, drinking pure water, and eating pure food, only return with the germs of an often fatal disease within them to swell the typhoid statistics of our large cities. disposal of sewage. the vital thing which thus presents itself is the disposal of fecal matter and other refuse so that the wells, upon which most rural families depend for their drinking water, may remain pure. to this matter we will first turn our attention. every person who tills the soil is acquainted with the remarkable transforming power of the superficial layers of the earth upon manure and excrement. out of these offensive wastes harmless substances are produced which are essential to the growth of vegetation. this power, known as decay, is now generally attributed to very minute organisms (bacteria) which are found in immense numbers in the superficial layers of the soil, which diminish in number as we go deeper, and which completely disappear below a depth of 6 to 12 feet, according to the physical condition of the soil. bacteria are more numerous where waste and excrement are most abundant. when night soil and manure are deposited in excavations or so-called cesspools in the earth, from which the fluid matter may enter the ground at some depth below the surface, where the air or certain kinds of bacteria can penetrate only to a slight extent, the substances, which under the influence of the air (oxygen) and of bacteria near the surface, would have decayed, now undergo partial putrefaction with the setting free of disagreeable gases and odors. the deeper layers of the earth slowly become saturated with organic matter, which is carried by the ground-water into the wells or springs near by. there is also some reason to believe that disease germs live longer in the oxygen-free depths of the soil than at or near the surface. the extent to which the filling up of the soil with excrementitious matter may go on in densely populated cities has been shown by fodor for the hungarian city budapest. by analyzing the soil at different levels from the surface to a depth of about 13 feet, he found, over an area comprising 15 acres, about 1,000,000,000 pounds organic matter, equivalent to the excrement of 100,000 people voided during thirty-seven years. [illustration: fig. 1.--the shallow barnyard well, with privy vault and manure heaps near by. the water is likely to receive fluid from these at any time.] to the surface of the earth we owe thus a purifying influence whose activity furnishes us vegetation and food on the one hand and preservation from disease on the other. this purifying power is not possessed by the deeper layers, and therefore the percolation of organic refuse into them from deep cesspools is wasteful to agriculture and dangerous to our storehouse of drinking water. even the surface of the soil when overloaded with sewage loses partially its power of purifying the organic matter. after sufficient rest, such an overloaded soil regains its original power. the purifying activity of the soil from a sanitary aspect is the same as that governing fertility from an agricultural standpoint, hence any further discussion of this subject is unnecessary. a hint as to the proper disposition of waste, excrement, etc., is furnished by what is stated above concerning the purifying capacities of the earth's surface. waste, night soil, etc., should be deposited with proper precautions on or immediately below the surface of the soil, where it may perform the double function of ridding the household of a nuisance and of enriching the soil itself. this leads us to a consideration of the best means of taking care of the household wastes. these are, in general, of three classes: first, fecal matter; second, kitchen and chamber slops; and third, miscellaneous rubbish and ashes. night soil. the proper disposition of fecal matter or night soil in the country has been one of the most pressing and vexatious problems of modern sanitation. many plans have been suggested, much apparatus has been invented to meet the difficulty, but opinions not only differ but change from year to year and have led to different practices in different countries. moreover, different climatic conditions and the divergent tendencies of rural populations in the various sections of our own country make it impossible to apply the same scheme to the whole country. different degrees of prosperity and wealth, even in the same locality, will bring into use widely different schemes to accomplish the same end. there are in use several systems-_the privy._--the old-fashioned privy, at present still quite a common thing even in cities, is, perhaps, the most favored method of disposing of fecal matter in the country. a pit is dug and a small building set over it. the excrement deposited in it slowly fills it up. the fluids and the solids dissolved by them penetrate the subsoil and diffuse themselves in the ground. rarely is such a pit cleaned out. another is dug and the old one covered up. in this way the ground becomes overloaded with refuse organic matter. it is even stated on good authority that such collections of fecal matter have been found under the dwelling; also, that the privy vaults have been dug until the current of ground-water was reached which was to facilitate the removal of the excrement. it is difficult to conceive a more pernicious custom, or one more certain to pollute the drinking water. the privy vault is the most rudimentary way of getting rid of night soil, and its dangerous features are too plain to be referred to. _the cesspool._--next comes the cesspool, which is usually connected with a water-closet, and may also receive the slops from the kitchen. these are constructed in two ways, either as water-tight receptacles or as simple pervious pits differing in no way from the privy vault excepting, perhaps, in their more dangerous tendencies. all sanitary authorities agree in condemning the leaky cesspool as a most shiftless and dangerous method of getting rid of sewage. in most countries they are prohibited by law in populous communities. in exceptional cases, leaky cesspools may do no harm, as in an isolated house in the country whose cesspool is built at a considerable distance both from the house and the well. the safe distance from any well it would be difficult to state, because that would depend on the character of the subsoil and the general slope of the land. in any case, the cesspool should be on lower ground than the well, as the current of the ground water feeding the latter, usually but not always, conforms to the slope of the surface. a fair estimate of the least allowable distance between well and cesspool would be 100 feet. soluble salts from sewage might still find their way into the well water, but it is quite improbable that disease germs could penetrate the soil for such a distance except where fissures and cracks may be present. [illustration: fig. 2.--portable earth closet. a, the pail to receive the excrement; b, the urine-separating receptacle hanging on the open door; c, mouth of the hopper conveying the dry-earth or ashes from reservoir d upon the night soil in a.] in villages, leaky cesspools are still of frequent occurrence. if the drinking water is taken from wells, such cesspools are a constant menace, and all that is needed in many such towns is a spark in the shape of some disease germ to kindle an epidemic. it is true that years may pass by without the occurrence of more than the usual amount of illness, but even then we have good reason to suppose that in many villages using cesspools the average amount of sickness and mortality is far too high, not to mention the occasional epidemics of typhoid-fever. we may sum up the matter of leaky cesspools by the statement that they may do no harm near isolated houses on farms, provided they are sufficiently far away from the source of water-supply. in small towns cesspools should be prohibited, or only very thoroughly constructed water-tight ones permitted, according to circumstances. the same holds true for the well-known privies. _the dry-earth closet._--the dry conservancy system is a much better method of disposal of excrement, and is extensively in use to-day even in certain large cities on the continent of europe where sewers have not yet been introduced. this consists in the main of the frequent removal of excreta in the country by some man servant or member of the family; in villages and towns according to some cooperative plan. this system has taken various directions, according to circumstances. thus there are what is called the pail system, which consists in the daily or less frequent removal of a pail receiving the excreta; and the earth closet invented by the rev. henry moule, of england, the chief feature of which consists in the covering of the excreta with some absorbent substance like dry-earth or ashes. in some places the excreta are received into a well-built brick or stone receptacle and covered with earth, from which they may be removed from time to time. of these systems the dry-earth closet has received the greatest amount of attention and discussion. it consists, essentially, of a pail to receive night soil, which is covered either automatically or with a scoop with dry-earth (fig. 2). the earth absorbs the fluids and the odors and keeps the closet inoffensive. [illustration: fig. 3.--the old form of earth closet with frame and pail removed to show the mechanism. the handle on the left when raised throws into the pail a certain quantity of dry-earth or ashes from the reservoir or hopper in the rear.] the earth to be used should be a rather fine loam, sifted to remove coarse particles, thoroughly dried by spreading out in the sun or under a shed, and then stored in barrels. the drier the earth the better it is. the finer the particles of earth the greater the capacity for absorbing fluids. for this reason sand is not satisfactory. goal or wood ashes are quite satisfactory, as they are, after proper sifting, of the requisite fineness and are thoroughly dry. the mixture of earth or ashes and night soil should be removed at certain times, depending on the location of the closet, the season of the year, and other conditions. the more frequent the removal the better. the mixture of soil and excrement is so unobjectionable that it has been used over a number of times after being dried each time. this can not be recommended, however, as it is generally accepted nowadays that disease germs may remain alive in such a mixture for some time. in place of the movable earth closets, a water-tight, concreted area may be built in an annex to the house, which is to receive the night soil from a closet on the floor above with the necessary quantity of dry soil (see fig. 4). poore, from whose book the illustration is taken, recommends, in addition, the construction of the floor of such a pit with an inclination sufficient to carry away the urine into some gutter outside filled with absorbent soil. the area should have suitable openings for inspection and for removal of contents, as well as for ventilation. waring recommended a similar system many years ago. the closet described by him discharges into a water-tight vault in the cellar, which requires emptying only occasionally. the contents remain inoffensive, provided sufficient thoroughly dry earth is used. [illustration: fig. 4.--earth closet and dry catch (from poore's "rural hygiene," scale, 1/2 inch equals 1 foot). to prevent drafts the earth closet is closed below by a hinged flap which opens and shuts automatically by means of a counterpoise. the catch below is provided with air bricks and an air shaft leading to a ventilator.] in cold climates, indoor closets are especially desirable to obviate the exposure which can not be avoided when closets are out of doors. for invalids there should be a carefully managed earth closet kept in a well-aired room set apart for this purpose. in warm climates, earth closets should be frequently cleaned. to prevent the attraction of flies and insects and the too rapid decomposition of the contents a little unslacked lime added with the earth to the excrement will be of value. the discharges of persons suffering from typhoid-fever and bowel troubles should be mixed with thin slacked lime[1] (milk of lime). one-half to one hour after the mixing, such discharges may be put upon the soil, always at some distance from a well or spring, a stream, or a field under cultivation. [1] lime, to be used for disinfection, should not be air-slacked, but kept in tightly covered receptacles to prevent this from taking place. in europe, the use of earth and ashes has been superseded by peat dust. the upper layer of peat is dried in the air and ground in a suitable machine. the coarser particles are removed by sifting and used for bedding in stables. the fine portion, which has a very high absorbing power for fluids and is also capable of preventing odors, is used in dry closets. in germany there are at present about thirty factories engaged in the preparation of peat moss for the purposes mentioned. its great advantages over dry earth should bring it into use in our country. (see fig. 5.) it does not matter from a sanitary standpoint which one of the dry-earth systems is adopted, provided the necessary attention be given to it. every system which can be recommended is bad if not properly attended to. the conditions to be observed are: the night soil should be received in water-tight receptacles. it should be frequently removed. it should be utilized in the garden or field by being placed under a thin layer of soil. to excreta from the sick, milk of lime or unslacked lime should be added before disposal in the soil. [illustration: fig. 5.--self-acting peat dust closet. the lid is replaced by a hinged reservoir containing the peat dust. whenever this is let down a certain quantity of peat dust is discharged automatically and thrown, upon the night soil. (from weyl's handbuch der hygiene. ii, p. 315.)] _the water-closet._--there can be no doubt that to-day the water-carriage system, as it is called, or, in simpler language, the indoor water-closet, is preferred to all other contrivances. this is true for the open country as well as for villages and the suburban territories of cities. there is much to be said in favor of the present-day perfect contrivance for the rapid removal of excreta and the exposure thereby prevented. but for all rural inhabitants the cost should be carefully weighed before a water-carriage system is introduced into a house, for none but the best will answer, as all others are likely to become nuisances. the supply of water must be sufficient to flush the water-closet thoroughly and keep all the pipes clean; the plumbing must conform to that in vogue in cities, with its traps and ventilating pipes to prevent the odors of the pipes from escaping into the house; and the disposal of the large quantity of liquid sewage, the most difficult problem, must be properly attended to or it is likely to prove more dangerous to the water-supply than the old dry privy pits. liquid sewage. the methods available to dispose of liquid sewage in the country are water-tight cesspools and irrigation. _vaults._--water-tight cesspools should be constructed of hard-burned brick, laid in cement, and having a similar brick or a concreted bottom. the inside and outside surfaces of the brick wall should be coated with a thin layer of cement, and clay rammed in around the wall, to increase its imperviousness to water. it should be vaulted above, and topped by a square or round central opening, covered with stone or iron plate. cesspools are also made of cast or wrought iron, the joints being made water-tight. cesspools must be ventilated by two pipes, one rising several feet above ground, the other carried to the roof of the house, barn, or other structure near by. the current will, in most cases, tend down the short and up the long pipe. the latter may be dispensed with and the soil pipe of the house act as a flue, provided all branches are perfectly trapped. [illustration: fig. 6.--settling chamber and flush tank for surface and subsurface irrigation of sewage. (from gerhard's "the disposal of household wastes," 1890.)] _irrigation._--the disposal of sewage by irrigation is by far the best method now within reach. two methods are in use, viz, surface and subsoil irrigation. the first in its most complete form consists in carrying the liquid sewage to a piece of ground set apart for the purpose and carefully underdrained. the sewage is allowed to flow over the ground in shallow channels. the fluid slowly disappears in the soil and enters the drains as comparatively pure water, which may be allowed to flow into a stream. for villages this is the best means of disposing of sewage. those who as village officials may be interested in this method will find plans of such sewage farms, together with faithful accounts of their operation and the results obtained, in the annual report of the state board of health of massachusetts for 1892, page 559, and same report for 1893, page 563. suggestions for its application to country houses are given farther on. for isolated rural homes, or village homes commanding a certain amount of ground around the house, the liquid sewage from water-closets, the kitchen and chamber slops may be disposed of by the simple means of subsoil irrigation, first described by mr. moule and subsequently elaborated by colonel waring. the system as used at present in its most successful form consists, outside of the house, of the following parts (see fig. 6): two adjoining water-tight receptacles of brick. one of these receives the sewage from the house and is intended to act as a settling chamber for the coarser particles, paper, etc. this communicates with the second receptacle, which receives from it the fluid sewage. this chamber is called the flush tank and is provided with a siphon. when the fluid has reached a certain level, the siphon is set in operation and discharges the contents of the chamber at one time into the subsoil pipes. [illustration: fig. 7.--subsurface irrigation of sewage: _a_, absorption tiles (gerhard's "the disposal of household wastes"); _b_ and _c_, lines of absorption tiles showing their relation to flush tank (from waring's "sewerage and land drainage").] from the second cistern a system of subsoil pipes laid over a treeless piece of ground, preferably a lawn, receives and discharges the sewage into the ground. these pipes should consist of porous tiles, 2 inches in diameter and about 1 foot long, laid from 8 to 16 inches beneath the surface of the ground, and with a gentle inclination of 2 or 3 inches for every 100 feet. the tiles should have open joints not less than one-fourth of an inch wide. they are laid upon earthen gutters and the joints are protected above by caps from being clogged with earth. the intermittent discharge of the liquid sewage is quite essential to the successful working of this system. if the sewage is allowed to dribble away into the pipes certain portions of these will become supersaturated with fluid and others will not receive any; the purification of the sewage in the soil is thereby rendered imperfect. the discharge of a large quantity of fluid at one time, besides scouring the system of pipes, fills it more uniformly and distributes the work to all parts of the subsoil system. the successful construction of such a plant requires the services of someone familiar with it, and it is therefore not necessary for me to do more than call attention to it here as a highly recommended system for homes, especially in villages, where the proper amount of land is procurable and where the sewage must be disposed of in a manner both inoffensive and safe. in any case the soil of such land must be porous, not clayey and retentive. those who wish to familiarize themselves with the details will find descriptions in the sanitary engineer for 1883, page 530, by philbrick; in "the disposal of household wastes," by gerhard, and in "sewerage and land drainage," by waring. the entire plant is said to cost $200 to $300, the annual expenditures for cleaning, repairs, etc., about $10. the method of subsurface irrigation just described may be too complex and too expensive where land is abundant and neighboring houses at some distance. the simpler method of surface irrigation may be resorted to by laying out at some distance--at least 100 feet--from the house a small sewage farm where the sewage may flow in shallow trenches over the surface and slowly sink into the ground. such an irrigation field must have the same qualities demanded by subsurface irrigation. its surface should have sufficient slope and the soil should be porous, not retentive. the liquid sewage, including kitchen and chamber slops, is conducted to this field in a water-tight tile drain and then allowed to flow into shallow trenches. to avoid the overloading of the soil with sewage at any one place the main distributing trench should be so arranged that it and the irrigating trenches branching from it may be temporarily blocked at any point to divert the sewage into one or more different trenches every day. in winter the warmth of the sewage will keep it in motion and the filtration will go on although the field may be covered with snow and ice. the use of the flush tank as described above would cause a more uniform distribution of the fluid over the field and make the filtration distinctly intermittent. the ground between the trenches may be cultivated to increase the amount of evaporation. if conveniently situated, an orchard may be used as the irrigation field. it should be distinctly understood, however, that marketable fruits and vegetables should not be carelessly allowed to come in contact with fresh sewage, nor should the irrigation field be near the well unless the latter is fairly deep and tubed or tiled to the surface of the water. kitchen and chamber slops. the removal of kitchen and chamber slops is a matter which also requires proper attention, as this liquid frequently gives rise to unhealthful conditions, annoying alike to sight and smell when carelessly disposed of. the simplest way to utilize kitchen slops is to pour them upon plants about the house in summer, in winter upon the soil, each time in another spot, so as not to supersaturate the surface layers of soil in any one place. a means of less trouble recommended by waring is to partly fill with soil a barrel with leaky bottom and cover this with a layer of stable manure to prevent the puddling of the soil. the slops filter through the soil and leave the barrel below as a clear fluid. the barrel is emptied two or three times a year and the contents used for fertilizer. house slops may be disposed of by surface irrigation or by subsoil pipes, as already described. the originator of this method, mr. moule, may here be profitably quoted as to its simplicity and success: where there is a garden the house slops and sink water may, in most cases, be made of great value and removed from the house without the least annoyance the only requirement is that there shall be a gradual incline from the house to the garden. let all the slops fall into a trapped sink, the drain from which to the garden shall be of glazed socket pipes well jointed, and emptying itself into a small tank, 18 inches deep, about a foot wide, and of such length as may be necessary. the surplus rain water from the roof may also enter this. out of this tank lay 3-inch common drain pipes, 8 feet apart and 12 inches below the surface. lay mortar at the top and bottom of the joints, leaving the sides open. if these pipes are extended to a considerable length, small tanks about 1 foot square and 18 inches deep must be sunk at about every 20 or 40 feet to allow for subsidence. these can be emptied as often as required, and the deposit may be either mixed with dry-earth or be dug in at once as manure. the liquid oozes into the cultivated soil, and the result is something fabulous. * * * on a wall 55 feet in length and 16 feet high a vine grows. a 3-inch pipe runs parallel with this at a distance of 6 feet from it for the entire length. the slops flow through this pipe as above described. on this vine year after year had been grown 400 well-ripened bunches of grapes, some of the bunches weighing three-fourths of a pound. during a period of four years, for a certain purpose, the supply was cut off. to the surprise of the gardener scarcely any grapes during those years appeared; but afterwards the supply was restored, and the consequence was an abundant crop, the wood grow fully 16 feet, of good size and well ripened. in place of an indoor sink, an upright tube or hopper may be constructed out of doors in communication with the subsurface pipes into which the waste fluids are poured. waste and garbage. the attractiveness of a rural home depends largely upon the promptness with which all kinds of waste material are disposed of. the abundance of space around the house is a great temptation for the members of the household to use it as a place for storing rubbish and useless, worn-out things. sifted ashes are easily utilized in earth closets and upon walks and roads, to make them compact and firm. other articles of no use, such as broken crockery, bottles, tin cans, etc., can be thrown into depressions and gullies and covered over with earth, or else buried in trenches where subsoil drainage is desirable. the removal of rubbish is a very fruitful theme and might be dealt with at length. its importance as related to health and disease is a subordinate one, and the reformer must appeal to the love of order, propriety, and beauty in and around the home in order to make an impression. garbage is of much less annoyance in the country than in the city, where its collection and destruction is a great expense, and is frequently very unsatisfactorily done. in the country, the household garbage is fed to the swine and poultry, and is in this way profitably used. there are, however, homes where garbage must be taken care of in other ways. it may be buried in the garden or else burned in the kitchen range. recently a device has been patented which enables the housekeeper to place the garbage in a section of the smoke pipe of the range, where it dries out rapidly, burns, and leaves only a little charcoal behind, which may be used for fuel next day. this device has been well recommended by sanitarians (see fig. 8). [illustration: fig. 8.--garbage cremator. the garbage is placed in the perforated frame. the latter is pushed into the smoke pipe, where the garbage becomes slowly carbonized.] protection of drinking; water. the next subject to claim our attention is the protection of the sources of drinking water. in the country water is, as a rule, obtained from wells and springs. the important bearing upon well water of soil purity demands a few explanatory remarks concerning the origin of well water. wells are excavations made into the ground to a variable depth until water is reached. this water is denominated ground or subsoil water. its origin may be better understood if, for the moment, we conceive the surface of the earth as more or less irregular and entirely impervious to water. the rain would collect on this surface and form lakes, ponds, and streams, according to the configuration of the surface. if, now, we conceive this surface covered with sand or other porous earth to a greater or lesser height, and the top of this be considered the earth's actual surface, the water will remain in the same position, but it will be buried within and fill the pores of the overlying soil as subterranean lakes, ponds, and streams. in digging a well we remove this porous layer of earth until we reach these subterranean streams or reservoirs of ground-water. if the above description be thoroughly understood, the condition under which well water may be obtained at different depths will become intelligible, and it will also appear plain why ground-water may flow as any surface stream and pick up on its way various substances which have percolated into the ground. when the bed of porous soil overlying the impervious layers is very deep, wells will have to be dug down to a considerable depth to reach the surface of the ground-water. where this layer of pervious earth is of slight thickness wells will be shallow, and the ground-water may appear on the bottom of gullies, trenches, and wherever the porous layer has been dug or washed away. the movement of the ground-water depends on the inclination or slope of the impervious strata, and has been observed to be quite rapid in some instances. by adding common salt to the water in a well its detection in other wells at a short distance has been found a guide in the determination of the rapidity and direction of the underground current. when the ground-water resting on the uppermost impervious layers is near the surface, and therefore not safe or fit to use as drinking water, it may be possible by digging below this layer to find another porous bed containing water. this source will, in general, be much purer since it is less exposed to pollution from above, and since the water has to travel longer distances underground. such a deep supply must, however, be protected from the superficial supply by a water-tight wall extending to the surface of the deep supply, otherwise the water from the upper layers will simply drain into the well. ways of contamination. wells are exposed to contamination in two ways. the surface water from rain, house slops, and barnyard drainage may find its way into the well at or near the surface of the ground. or the ground-water stream supplying the well with water may in its subterranean movements encounter cesspools or seepings from cesspools, and carry with it soluble and suspended particles, some of which may enter the well. there can be no doubt that a large percentage of the wells are exposed to contamination with refuse matter in the manner described; and it now remains to gauge the danger to health and life which may be carried in the contaminating substance. the danger of typhoid-fever bacteria entering the water has already been mentioned. these may be washed in from the surface or they may pass from cesspools near by through fissures in the ground, passages dug by rats, etc. whether such bacteria can pass through the pores of a compact, unbroken soil from a cesspool to a well near it is a matter not fully settled. since, however, the actual condition of the deeper layers of the soil between cesspool and well can not be known, it becomes imperative to prevent all pollution of the ground-water current supplying wells by either abolishing the cesspools or else placing them at a considerable distance from all sources of water. beside typhoid-fever bacteria, those organisms which cause digestive disturbances, and severer troubles, such as diarrhea, dysentery, and possibly other unknown diseases, may be carried into well water. during cholera epidemics, polluted wells might form centers of infection. eggs of animal parasites may be washed in from the surface. again, the barnyard manure, representing the mixed excrement of various animals, may under certain conditions be bearers of disease germs, and such excrement should, under no conditions, be looked upon as entirely harmless to human beings.[2] [2] it is probable that the filth which gets into cow's milk and which appears to be mainly excrement of cows is largely responsible for the severe summer diseases of infants fed on cow's milk. besides the protection of the ground-water near the well from pollution emanating from cesspools, etc., the surface of the ground about the well should be kept free from manure, slops, and other waste water; hence the well should not be dug under or close by the house,[3] nor should it be located in the barnyard, where the ground is usually saturated with manure. it should be surrounded by turf, and not by richly manured, cultivated, or irrigated soil. the ground immediately around it should slope gently away from it and be paved if possible. the waste water from the well should not be allowed to soak into the ground, but should be collected in water-tight receptacles or else conducted at least 25 feet away in open or closed channels which are water-tight. [3] the water may be carried into the kitchen by running the pipe from the well, horizontally, under ground. construction of wells. the well itself must be so constructed that impurities can not get into it from above or from the sides. if water can soak into it after passing through a few feet of soil only, it can not be regarded as secure from pollution. to prevent this, the well may be provided with a water-tight wall built of hard-burned brick and cement down to the water level. the outside surface of this wall should be covered with a thin layer of cement, and clay pounded and puddled in around it. or, tile may be used to line the well and the joints made water-tight with cement down to the water level. driven wells, i. e., wells constructed of iron tubing driven into the ground, are, perhaps, the safest where the quantity of water needed is not large and where other conditions are favorable. these different devices are all designed to keep water near the surface of the soil from percolating into the well. to keep impurities from entering the well directly from the top considerable care is necessary. such impurities are likely to prove the most dangerous because there is no earth niter to hold them back and destroy them before they can reach the water. adequate protection above may be provided in several ways. the sides of the tiled wells should project above the surface and be securely covered with a water-tight lid. the ordinary well should also have its sides project above the surface and a water-tight cover of heavy planks provided, which should not be disturbed excepting for repairing or cleansing the well. under no circumstances should objects be let down into the well to cool. a still better method of protecting the water from above is to have the lining wall of the well end 3 feet below the surface of the ground and to be topped there with a vaulted roof, closed in the center with a removable iron or stone plate. the top should be covered with 12 inches of clay or loam; above this there should be a layer of sand, and lastly a pavement sloping away in all directions. too much care can not be bestowed upon the household well. it should be guarded jealously and all means applied to put the water above any suspicion of being impure. this is especially true in dairies where well water is used in cleaning the milk cans, and where steam and boiling water have not yet found their way for this end. polluted wells in such houses not only endanger the health of the inmates but that of a more or less numerous body of city customers. in those regions where rain water is the only safe drinking water, the same care is necessary to protect the stored supply from contamination, and no suggestions beyond those already given are necessary here. conclusion. in the foregoing pages it has been the aim of the writer to give a few facts and supply a certain number of ideas which, in the mind of any person who has thoroughly understood them and who thinks for himself, may be safely left to ripen into schemes adapted to his own wants and surroundings. how many resources a man armed with correct views may find in the simplest appliances the reader may judge for himself by consulting chapters ix, x, and xi of dr. vivian poore's very interesting volume on rural hygiene. whether the means for utilizing household wastes there described and adopted by him would be adequate outside of a limited territory of our own country, i am not prepared to state. for the same reason no definite suggestions can be made in these pages, owing to the wide diversity in the climatic and other conditions obtaining over the vast territory of our country. the writer has, furthermore, omitted all statements of detail which properly belong to the sanitary engineer. the works referred to will, however, supply those more directly interested with the facts and figures desired. the principles to be kept in the foreground are the disposal of sewage in the superficial layers of the soil in not too great quantity, the disinfection of the stools of the sick with lime before such disposition is made, the digging of wells in places kept permanently in grass and at some distance from barnyards, and, above all, their thorough protection from contamination from the surface and from the soil immediately below the surface. in every community there are public-spirited citizens who could do much good by taking hold of the simplest and safest methods of disposing of sewage and refuse, putting them into practice, and showing the rest of the community just what good can be accomplished and what harm avoided by a little continuous attention to sanitary matters. in this way many may be led to undertake improvements who, with no definite knowledge of the expense involved and with misgivings as to the final success of the undertaking, would otherwise hesitate to make a beginning. * * * * * farmers' bulletins. these bulletins fire sent free of charge to any address upon application to the secretary of agriculture, washington, d. c. [only the bulletins named below are available for distribution.] no. 15. some destructive potato diseases: what they are and how to prevent them. pp. 8. no. 16. leguminous plants for green manuring and for feeding. pp. 24. no. 18. forage plants for the south. pp. 30. no. 19. important insecticides: directions for their preparation and use. pp. 20. no. 20. washed soils: how to prevent and reclaim them. pp. 22. no. 21. barnyard manure. pp. 32. no. 22. feeding farm animals. pp. 32. no. 23. foods: nutritive value and cost. pp. 32. no. 24. hog cholera and swine plague. pp. 16. no. 26. sweet potatoes: culture and uses. pp. 30. no. 27. flax for seed and fiber. pp. 10. no. 28. weeds; and how to kill them. pp. 30. no. 29. souring of milk and other changes in milk products. pp. 23. no. 30. grape diseases on the pacific coast. pp. 16. no. 31. alfalfa, or lucern. pp. 23. no. 32. silos and silage. pp. 31. no. 33. peach growing for market. pp. 24. no. 34. meats: composition and cooking. pp. 29. no. 35. potato culture. pp. 23. no. 36. cotton seed and its products. pp. 16. no. 37. kafir corn: characteristics, culture, and uses. pp. 12. no. 38. spraying for fruit diseases. pp. 12. no. 39. onion culture. pp. 31. no. 40. farm drainage. pp. 24. no. 41. fowls: care and feeding. pp. 24. no. 42. facts about milk. pp. 29. no. 43. sewage disposal on the farm. pp. 22. no. 44. commercial fertilizers. pp. 24. no. 45. some insects injurious to stored grain. pp. 32. no. 46. irrigation in humid climates. pp. 27. no. 47. insects affecting the cotton plant. pp. 32. no. 48. the manuring of cotton. pp. 16. no. 49. sheep feeding. pp. 24. no. 50. sorghum as a forage crop. pp. 24. no. 51. standard varieties of chickens. pp. 48. no. 52. the sugar beet. pp. 48. no. 53. how to grow mushrooms. pp. 20. no. 51. some common birds in their relation to agriculture. pp. 40. no. 55. the dairy herd: its formation and management. pp. 21. no. 56. experiment station work--i. pp. 30. no. 57. butter making on the farm. pp. 15. no. 58. the soy bean as a forage crop. pg. 24. no. 59. bee keeping. pp. 32. no. 60. methods of curing tobacco. pp. 16. no. 61. asparagus culture. pp. 40. no. 62. marketing farm produce. pp. 28. no. 63. care of milk on the farm. pp. 40. no. 64. ducks and geese. pp. 48. no. 65. experiment station work--ii. pp. 32. no. 66. meadows and pastures. pp. 24. no. 67. forestry for farmers. pp. 48. no. 68. the black rot of the cabbage. pp. 22. * * * * * transcriber note illustrations were moved to prevent splitting paragraphs. transcriber note: text emphasis is denoted as =bold= and _italics_. fractions are represented as 1-2/3. sewage and garbage disposal on the farm [illustration] farmers' bulletin no. 1950 u.s. department of agriculture this bulletin is a guide to up to-date methods for the sanitary disposal of sewage and other household and farm wastes. it tells how to construct satisfactory sanitary facilities and how to maintain them and gives special attention to the questions on sanitation asked most frequently by farm people. solutions to all problems cannot be given here, and often advice must be sought from local sanitary officials. many county and state health departments furnish advice and copies of local regulations and sometimes provide inspection service. where there are no specific local requirements, this bulletin may be accepted as a guide to safe practice. issued march 1944 washington, d. c. revised june 1946 sewage and garbage disposal on the farm by j. w. rockey, _assistant agricultural engineer_,[1] and j. w. simons, _associate agricultural engineer_, _division of farm buildings and rural housing, bureau of plant industry, soils, and agricultural engineering, agricultural research administration_ [1] the senior author prepared the preliminary draft, and the junior author completed the bulletin. contents page characteristics of sewage 1 protection of water sources from household wastes 2 septic-tank systems 2 operation of a septic tank system 2 selecting the site 4 the house sewer 4 the septic tank 8 building a concrete tank 11 the effluent sewer 13 the disposal field 13 disposal methods in tight or wet soils 14 care and maintenance of septic tanks 17 effect of drain solvents and other materials 17 protection against freezing 17 septic-tank troubles 18 grease traps 18 disposal of drainage from fixtures other than toilets 19 cesspools 20 privies 21 care, and maintenance 22 chemical closets 24 disposal of garbage and trash 25 to insure healthful living, domestic wastes must be disposed of. primitive wanderers and too often present-day tourists deposit their wastes promiscuously and move on when the surroundings become foul. this is impractical in built-up communities. therefore, in most cities and in some rural areas sanitary codes regulate the disposal of wastes. characteristics of sewage household sewage ordinarily consists principally of human excrement, toilet paper, garbage, dish water, and other wash water from the various plumbing fixtures and floor drains. many kinds of bacteria, at times disease-producing ones, are contained in the discharges from the human body. epidemics of typhoid fever, dysentery, diarrhea, cholera, and other water-borne diseases may result from the pollution of the water supply with sewage. pollution is carried by water moving underground, as well as by water flowing on the surface. this is especially true in limestone regions, where underground channels and rock crevices permit water to flow for considerable distances with little filtering action. sewage used for fertilizing or irrigating crops[2] may contaminate vegetables or the udders of cows and thus spread disease. anthrax, cholera, and parasitic worms may be present in the surface drainage from fields and barn lots. it is wise to regard all sewage as dangerous and to dispose of it promptly in a sanitary manner, so that disease germs will not pollute the water supplies or be spread by flies, animals, or man. [2] this subject is discussed at length in technical bulletin 675, sewage irrigation as practiced in the western states. protection of water sources from household wastes under most farm conditions a safe place for the disposal of wastes is in the upper 3-foot layer of soil, where the action of bacteria tends to render it harmless. tile disposal fields, such as are used with septic tanks, and earth-pit privies accomplish this if the water table remains several feet below the surface and if the location is remote from water supplies. cesspools and other types of pits do not ordinarily confine contamination to their immediate vicinity and are not recommended except for special conditions. sewage or other wastes discharged into abandoned wells or other pits that reach to the water table or below it are almost certain to contaminate the ground water. it is generally poor practice, and often illegal, to discharge wastes into surface streams. streams do not necessarily purify themselves in 50 feet, 100 feet, or some other stated distance, as is commonly believed. they do tend to purify themselves over long distances through the action of sunlight, aeration, and other factors but may not be safe for domestic use for many miles below the source of pollution. clear, sparkling water is not always safe drinking water. streams in agricultural communities are subject to many sources of pollution and they are likely to become more contaminated as they merge into larger streams. septic-tank systems septic-tank systems, if installed and maintained properly, provide the most sanitary method of sewage disposal for farmhouses equipped with running water. ground water or rock close to the surface, lack of sufficient fall for the sewage to flow by gravity, and too small an absorption area for the effluent limit the satisfactory operation of a septic tank. when these conditions exist, special advice should be sought from a competent local sanitary authority. adverse soil conditions can be overcome if sufficient fall and space are available. the five essential parts (fig. 1) of a septic-tank system are (1) the house sewer; (2) the septic tank; (3) the effluent sewer; (4) the distribution box; and (5) the disposal field. in special cases a grease trap (see fig. 11, p. 19) is added. to facilitate inspection and repairs it is good practice to keep in the house a chart showing the location of the tank and other parts of the system. a septic tank does not necessarily purify the sewage, eliminate odor, or destroy all solid matter. its purpose is to condition the sewage or domestic waste by bacterial action, so that it can be disposed of in a more satisfactory manner. [illustration: figure 1.--a septic-tank system.] operation of a septic-tank system in a septic-tank system the sewage flows by gravity from the farmhouse through the sewer into the tank, where it should remain at least 24 hours. while passing through the tank the solids are acted upon by anaerobic bacteria, which work only in the dark and where there is little air. the heavy particles settle to the bottom as sludge, the lighter particles float as scum, and the remainder passes out of the tank through the effluent sewer to the disposal field. the gas released in the process escapes through a vent provided either in the =t= to the house sewer or the effluent sewer. a tank that is too small may fill up with solids in a short while, because sufficient time is not allowed for breaking them down by fermentation, or the sewage may be pushed right through into the disposal field and clog it. the effluent may contain even more disease germs than the original sewage, and though it may be as clear as spring water it is far from pure and may cause foul odors if discharged or allowed to pool on the surface of the ground. the final disposition of the effluent into the upper layer of the soil exposes it to the action of aerobic bacteria. these bacteria, unlike those in the tank, need air and cannot work in saturated soil or live much more than 3 feet below the surface of the ground. the "living earth," or upper stratum, teems with these bacteria, which convert the dangerous sewage and disease germs into harmless matter and thus tend to purify the effluent if it remains long enough in the top layers of soil before seeping into the subsoil and thence to the ground water. effluent discharged deep in the soil does not receive the benefit of this purifying action. several types of septic tanks are in common use. the one described in this bulletin is the single-chamber type, which can be built with or without siphon. this should meet all average farm needs where there are not more than 16 members in the household. it would be advisable to consult the authorities of the state agricultural college or local health department as to their recommendations because frequently local conditions and larger establishments require special installations. selecting the site first install the tile disposal field where there will be least danger of polluting water supplies, at least 100 feet from water sources if possible and always at a lower surface elevation. this is of greatest importance. even though selecting a more distant location would result in greater initial cost, it would be a good investment as protection against diseases that might result from pollution of water sources. the site should slope away from the house and away from the source of water. gentle unshaded slopes free of trees or shrubbery are best. root-free locations are important because the open-jointed tile cannot be "rootproofed." porous, well-drained, gravelly, or sandy soil allows greater purification. do not have the disposal field in vegetable gardens, under roadways, in swampy land, in muck soils, or in areas having rock substrata sloping toward the water supply. allow sufficient area, where available, to enlarge the field later if needed. the septic tank may be close to the house, but a more distant site would reduce the likelihood of odors if leakage occurs. the tank should also be kept 50 feet or more from any source of water supply and at a lower elevation. it should not be placed under driveways, pavements, or flower beds, as these would make it not readily accessible for periodic inspection. care should be taken to insure that surface drainage from the area around the tank will not reach the vicinity of the water supply. the house sewer material vitrified salt-glazed clay or well-made concrete sewer pipe and cast-iron soil pipe are the standard materials for house sewers on farms. asphalt-impregnated fiber pipe, of a type designed especially for house sewers, appears to be satisfactory for this purpose. cast-iron soil pipe with leaded joints should be used when the sewer is within 50 feet of a well or suction line from a well, within 10 feet of any drinking-water supply line under pressure, within 5 feet of basement foundations, or when laid beneath driveways with less than 3 feet of earth covering the pipes. when within 15 feet of large trees or shrubs, the sewers should have root-tight joints. size for house sewers, 4and 6-inch pipes are generally used. where a 4-inch pipe is used, cast-iron is commonly recommended. grades with little fall require larger pipes. the large sizes are also less liable to become clogged. clay pipe is made in pieces 2 or 2-1/2 feet long, whereas fiber-pipe sections are 4 feet long and cast-iron pipe 5 feet long, so that there are fewer joints. the minimum number of joints is desirable, as there is less danger of stoppage. alinement run the house sewer in a straight line and avoid bends whenever possible. slight changes in direction may be made with one-sixteenth or one-eighth bend fittings. for sharper changes of direction a manhole or distribution box may be used. changes in direction of more than 45 are not recommended unless a manhole is provided. clean-outs are desirable within 5 feet of the septic tank where tanks are placed more than 20 feet from the building and the sewer line is not buried deeper than 4 feet. establishing line and grade the trench for laying the sewer is usually dug after the septic-tank excavation has been completed and the elevation of the tank inlet determined. a simple method of setting guides for the excavation is illustrated in figure 2. digging the trench start digging the trench at the tank end, so that rain or seepage will have an outlet. rounding the bottom of the trench to the shape of the pipe and hollowing out basins for the "bell" ends allows the pipe to rest firmly throughout its full length, permits full calking of joints, and relieves the strain on them. laying the pipe begin laying the pipe at the tank with the bell end uphill. joints in clay-tile pipe are commonly made with portland cement mortar or grout. where root-proof joints are essential, sulfur-sand compounds may be used or copper rings provided and used with cement-mortar joints. asphalt-mastic compounds, however, are more satisfactory. for cast-iron soil pipe, lead is the standard joint material. after the hub is pushed into the bell, oakum (or old hemp rope) is packed with a calking iron or a piece of wood (fig. 3, _a_.) solidly and evenly in the joint to a depth of about half an inch to center the hub end in the bell and to keep the joint filler from getting inside the pipe. oil, grease, or dirt on the joint surfaces should be removed, as it will prevent joint material from sticking. figure 3 shows the different jointing methods. [illustration: figure 2.--establishing grade for sewer. _a_, 2by 4-inch stakes are set each side of the trench at convenient distances _a_, _b_, _c_, and _d_. then a board is nailed horizontally on the stakes at _d_ at a convenient height above the bottom of the trench, that is, the bottom of the sewer leaving the house. a board is nailed likewise to the stakes at a the same height above the inlet to the tank that _d_ is above the bottom of the trench. similarly, boards are set at _b_ and _c_ by sighting from _a_ to _d_ so the tops of the intermediate boards will be in line. _b_, the exact grade of the sewer is obtained by measuring from the grade cord with the 1by 1-inch stick, shown in detail. the length of the stick must equal the height of the board above sewer at _d_.] bituminous, sulfur-sand, lead, and other commercial joint compounds are poured while hot into the joint from a ladle (fig. 3, _f_), and when the work is well done they form a joint that is practically root-proof. they are more expensive than cement mortar. for molding hot compounds, a clay dike, or funnel, built about 3 inches high around the triangular opening at the top of the jointer greatly aids in the rapid and complete filling of the joint space. a hot joint must be poured continuously, otherwise a seam may develop between successive pourings. bituminous compounds make a slightly elastic joint. a joint in 4-inch pipe requires about 3/8 to 1/2 pound of compound and in 6-inch pipe about 1 to 1-1/2 pounds. sulfur-sand joints are hard and inelastic. the compound is made by mixing together equal volumes of ordinary powdered sulfur and very fine clean sand, preferably the finest quicksand, and then heating the mixture until the sulfur melts. a 4-inch joint takes about 3/4 pound and a 6-inch joint about 1-7/8 pounds of the mixture. commercial sulfur-joint compounds also are available. [illustration: figure 3.--jointing sewer pipe. _a_, using calking iron to force packing into joint. _b_, making joint with 1:2 portland cement mortar. use only enough water to dampen the mix. recalk after half an hour, to close shrinkage cracks. _c_, the completed joint. wrap finished joint with cloth and keep dampened, to aid curing. _d_, joint made by pouring 1:1 portland cement grout of creamy consistency into a form. this type of joint is not feasible unless the metal forms shown are available. _e_, use of asbestos runner clamped around pipe, for pouring hot joint. _f_, clay roll used in place of asbestos runner. _g_, a completed bituminous joint. _h_, use of swab, to remove any joint material forced through to inside of pipe.] soft pig lead or old scrap lead is suitable for lead joints on cast-iron pipe. about 3/4 pound per inch of pipe diameter is generally required for each joint. the lead is hot enough to pour when it begins to char the paddle used to skim off the impurities. when it cools it must be calked tightly to take up shrinkage. the calking should be uniform around the entire joint and should stop when the lead is tight. heavy pounding or continued calking may crack the bell of the pipe. it is easier to get good, joints when the pipe is in a vertical position. therefore, two lengths of pipe are frequently joined and are then laid as a single unit in the trench. in using terra cotta pipe, this procedure may be followed only when the joint is made with a mastic compound. cement-mortar joints cannot be used in such cases. before filling the trench, the sewer should be tested to detect possible leaks. earth free from rubbish and large stones should then be tamped around and about 1 foot above the pipe. the septic tank flow through the tank slow, undisturbed flow through the tank is necessary for the separation of solids and liquids and for bacterial action. submerged inlets and outlets or baffle boards reduce disturbance. a submerged outlet prevents scum from passing out with the effluent. the single-chamber tank without a siphon, shown in figure 4, is easy to build, inexpensive, and entirely satisfactory in most instances. in very tight soils or for large installations a siphon and sometimes two chambers are advisable. size the tank should be large enough to retain the sewage at least 24 hours. the size should be determined by the largest number of persons that may live in the house, rather than by the number actually living there at the time the tank is built. the additional cost of a large tank over a small one is relatively little. if there is any question as to which of two sizes should be built, it is wise to choose the larger. the dimensions recommended in the table in figure 4 are based on an average production of 50 gallons of sewage per person per day. unusually large quantities of sewage call for a tank of large capacity. in village and suburban homes where there is less food preparation than on farms and where the number of persons is more or less fixed, slightly smaller sizes will serve. in no case should the capacity of the tank below the flow line be less than 500 gallons. a tank length of two to three times the width should be maintained, and it is advisable to provide a depth of at least 4 feet below the flow line. allow about 1 foot of "freeboard," or air space, above the flow line for the accumulation of gases. this space is generally vented through the soil stack of the house. a siphon (fig. 5) with a dosing chamber is not considered necessary for a farm septic tank except for large installations (1,000 gallons or more), for those in tight soils, and where the disposal field is limited. [illustration] +---------------------------------------------------------------------------+ | capacities, dimensions, and concrete materials | | for septic tanks serving individual dwellings | +---------+--------+--------------------------------+-----------------------+ |_maximum |_liquid |_recommended inside dimensions_ |_materials for concrete| |number of|capacity+-------+--------+-------+-------+ 1:2-1/2:4 mix_ | |persons |of tank |_width_|_length_|_liquid|_total +-------+-------+-------+ |served_ | in | | | depth_| depth_|_cement|_sand |_gravel| | |gallons_| | | | | sacks_| cubic | cubic | | | | | | | | | yards_| yards_| +---------+--------+-------+--------+-------+-------+-------+-------+-------+ |4 or less| 500 | 3'-0" | 6'-0" | 4'-0" | 5'-0" | 16 | 1-1/2 | 2-1/2| +---------+--------+-------+--------+-------+-------+-------+-------+-------+ |6 | 600 | 3'-0" | 7'-0" | 4'-0" | 5'-0" | 17 | 1-3/4 | 2-3/4| +---------+--------+-------+--------+-------+-------+-------+-------+-------+ |8 | 750 | 3'-6" | 7'-6" | 4'-0" | 5'-0" | 19 | 2 | 3 | +---------+--------+-------+--------+-------+-------+-------+-------+-------+ |10 | 900 | 3'-6" | 8'-6" | 4'-0" | 5'-0" | 21 | 2-1/4 | 3-1/4| +---------+--------+-------+--------+-------+-------+-------+-------+-------+ |12 | 1100 | 4'-0" | 5'-6" | 4'-6" | 5'-6" | 24 | 2-1/4 | 3-1/2| +---------+--------+-------+--------+-------+-------+-------+-------+-------+ |14 | 1200 | 4'-0" | 5'-0" | 4'-6" | 5'-6" | 25 | 2-1/2 | 3-3/4| +---------+--------+-------+--------+-------+-------+-------+-------+-------+ |16 | 1500 | 4'-6" | 10'-0" | 4'-6" | 5'-6" | 28 | 2-3/4 | 4-1/4| +---------+--------+-------+--------+-------+-------+-------+-------+-------+ figure 4.--single-chamber septic tank. note alternate use of baffle boards where sanitary tees are omitted at inlet and outlet. the siphon provides intermittent discharge of effluent, which allows time for the disposal area to rest and aerate between discharges. this is more important where the discharge is nearly continuous than in small installations. the frequency and volume of the discharge into the tile field are controlled by the sizes of the siphon and the dosage chamber. the dealer should be informed of the size of the tank and the number of persons in the household, in order that he may furnish the proper unit. a 3or 4-inch siphon will be adequate for almost any farmhouse installation. construction most septic tanks are built of concrete cast in place, since in this way there is a minimum possibility of cracks developing. concrete blocks, however (not cinder blocks), stone, brick, or structural tile are sometimes used. prefabricated commercial tanks of concrete and various other materials also are available. [illustration] +--------------------------------------------------------------+ | siphon | +--------------------------+-----------------------------------+ |_diameter of siphon |_clearance under bell | | a 3" or 4"_ | e 2"_ | +--------------------------+-----------------------------------+ |_diameter of bell |_distance across u-trap | | b 10"or 12"_ | f 10" or 12"_ | +--------------------------+-----------------------------------+ |_bottom of outlet |_bottom of outlet | | to discharge line | to bottom of u-trap | | c 20-1/2" to 25-3/4"_| g 12" or 13"_ | +--------------------------+-----------------------------------+ |_drawing depth |_height above floor | | d 13" to 17"_ | h 7-1/4"to 11-3/4"_ | +--------------------------+-----------------------------------+ | dimensions of dosing chamber | +-----------------+-------------------+------------+-----------+ | _number of |_depth below | | | | persons served_ | discharge line_[3]| _width_[4] | _length_ | +-----------------+-------------------+------------+-----------+ | 4 or less | 16-1/4" to 20-1/4"| 3'-0" | 6'-0" | +-----------------+-------------------+------------+-----------+ | 6 | " | 3'-0" | 7'-0" | +-----------------+-------------------+------------+-----------+ | 8 | " | 3'-6" | 7'-6" | +-----------------+-------------------+------------+-----------+ | 10 | " | 3'-6" | 8'-6" | +-----------------+-------------------+------------+-----------+ | 12 | " | 4'-0" | 8'-6" | +-----------------+-------------------+------------+-----------+ | 14 | " | 4'-0" | 9'-0" | +-----------------+-------------------+------------+-----------+ | 16 | " | 4'-6" | 10'-0" | +-----------------+-------------------+------------+-----------+ [3] depending upon depth c of siphon. [4] same as single chamber tank fig. 4. figure 5.--typical design for a concrete septic tank with a dosing chamber and a siphon. masonry units should be laid in full beds of 1:3 cement mortar and the walls and floor plastered with at least a 1/2-inch coat of 1:2 mortar. cells of concrete blocks and tile must be filled with concrete. masonry walls are generally 8 inches thick, and care must be taken to follow _inside_ dimensions given for concrete tanks. directions for laying structural tile, brick, and concrete blocks can be obtained from dealers or trade associations. commercial tanks are suitable if they embody the essential features given in this bulletin. capacities should be as recommended in figure 4 for concrete tanks. proper installation and periodic servicing also are essential. tanks badly damaged in handling should not be used. rapid corrosion of steel tanks will result if the asphalt coating is impaired. minor defects in precast masonry tanks may often be overcome by plastering the interior with cement mortar. building a concrete tank[5] [5] for information on making and placing concrete, see farmers' bulletin 1772, use of concrete on the farm. a convenient method of assuring correct location of the tank is to build a frame as shown in figure 6. care is necessary to aline it with the center line of the inlet and outlet and to level it so that the distance from the bottom of the 2 by 4's on the form to the lower edge of the inlet hole in the form will permit it to be set at the grade of the house sewer. this frame is used to support the form for the tank. to avoid caving the edges, drive the stakes supporting the frame before beginning the excavation. the lumber in the frame can be used later to make part of the tank baffles. [illustration: figure 6.--method of outlining a septic-tank excavation on the ground surface.] figure 7 shows how an inside form can be built and hung in place. the inlet and outlet tees should be carefully set and tied in place before the concrete is poured. a single length of pipe should be joined to the tee, so that the two can be set in the form as one unit. in most cases the earth walls of the excavations will serve as the outside forms unless the soil is sandy or gravelly and the excavation is deeper than 5 feet. if outside forms are used, space must also be provided for them. forms should be constructed before the excavation is made and the tank built as soon as practical, to avoid warping of forms and caving of earth walls. [illustration: figure 7.--inside form hung in place for single-chamber septic tank, also a form for casting concrete-slab cover in sections.] county agricultural agents, local health departments, building-material dealers, and other agencies often have forms that may be borrowed or rented. the effluent sewer the effluent sewer should be constructed in similar manner and of the same materials as the house sewer and on a slope of 1/8 inch to 1 foot. this line, however, may be laid of terra-cotta pipe, as cast-iron is not considered necessary except in unusual cases. this line should always terminate in a distribution box from which the tile lines of the disposal field lead away. for steep slopes the arrangement shown in figure 9 (p. 15) is practical. joints must be of root-tight construction if the sewer is in the vicinity of trees or shrubs. the length of the sewer depends upon the distance from the tank to a safe site for the disposal field. the disposal field correct installation of the disposal field is of great importance for proper functioning of the septic tank. therefore, the width, depth, and spacing of the tile trenches must be carefully selected. line of 4-inch, openjointed, agricultural drain tile laid in shallow trenches are ordinarily used. perforated fiber drain pipes also may be used and are obtainable in 4-foot lengths. a distribution box with an inlet for the effluent sewer and an outlet for each individual run of disposal tile is the best means of dividing the flow. the outlet serving a large or double disposal field may be alternately opened and closed by means of a sewage switch that permits half the disposal field to work and rest alternately several weeks. a switch is especially helpful in tight soils but should not be provided unless proper maintenance is assured, so that a portion of the disposal field will not be left to handle the entire load of the system for an indefinite period. there are many variations of boxes, but figure 8 shows a practical type. [illustration: figure 8.--typical distribution box.] shallow tile lines the disposal tile should not be more than 18 to 24 inches below the surface, and where the ground-water level rises to the bottom of the trench special underdrains, described on page 16, are necessary. special provisions must also be made where tight soils are encountered. these methods are described in the section entitled "disposal methods in tight or wet soils." the table in figure 9, together with the information given in table 1, below, may be used for estimating the number of tiles needed in any particular soil type. if there is any doubt about this requirement, a percolation test should be made in the disposal field, as follows: dig a hole 1-foot square and to the depth at which the tile is to be laid. this depth in most instances will be about 24 inches and should not exceed 36 inches. fill the hole with water to a depth of 6 inches and observe the time required for the water to seep away; divide by 6 to get the average time for the water to fall 1 inch. the test should be repeated at three or four different points in the disposal field and the average time noted for all tests used. the data in table 1 can then be used to determine the number of tiles needed. where 1 hour is required for the water to fall 1 inch the soil is totally unsuitable, and another site should be selected. soil conditions at the time of the test may vary from year-round average conditions, and this factor must be taken into account. if the soil appears exceptionally dry, greater depths of water may be used or the test repeated in the same hole. in no case should tests be made in filled or frozen ground. where fissured rock formations are encountered, advice should be sought from sanitation specialists. table 1.--_determining tile-disposal field requirements from percolation tests_[6] ------------+----------------------++------------+-------------------- minutes | effective absorption|| minutes | effective absorption required | area required, per || required | area required, per for water to| person, in bottom ||for water to| person, in bottom fall 1 inch | of disposal trenches ||fall 1 inch | of disposal trenches ------------+----------------------++------------+-------------------- | _square feet_ || | _square feet_ | || | 2 or less | 26 || 10 | 52 | 30 || 15 | 63 | 36 || 30 | 90 | 40 || 60[7] | 120 ------------+----------------------++------------+--------------------[6] a minimum of 150 square feet should be provided, equal to 100 feet of 18-inch trench. [7] if more than 60 minutes, use special design with seepage pits or sand-filter trenches. figure 9 suggests methods of arranging the tiles in disposal fields under varying conditions and the length of tiles needed. [illustration: figure 9.--arrangements for tile-disposal fields, method of laying tile, and length of tiles needed.] size and minimum spacing requirements for disposal trenches +---------+----------+----------------------+-------------+ | trench | trench | effective absorption | tile lines | | width-w | depth-d | area in square feet | spacing-s | |in inches| in inches| per lineal foot | in feet | +---------+----------+----------------------+-------------+ | 18 | 18 to 30 | 1.5 | 6.0 | | 24 | 18 to 30 | 2.0 | 6.0 | | 30 | 18 to 36 | 2.5 | 7.5 | | 36 | 24 to 36 | 3.0 | 9.0 | +---------+----------+----------------------+-------------+ wider spacing of the lines desirable where available area permits disposal-tile trench disposal-tile lines--maximum length for each line 100 feet. all lines to be equal in length. disposal-tile lines to slope 2" to 4" per 100 feet, not over 6". sewer-tile lines to slope 1/8" to 1/4" per foot. disposal methods in tight or wet soils if the soil is heavy clay or has tight formation, yet shows some porosity from percolation tests, the efficiency of the field may be increased by placing below the tile lines 12 to 15 inches of additional filter material (washed gravel, crushed stone, slag, clean cinders, or clean bank-run gravel 3/4 to 2-1/2 inches in size). when the surface soil is tight and is underlain by porous soil, sufficient drainage is sometimes obtained for the smaller installations by omitting the tile field and providing a dry well at the end of the effluent sewer, provided the water table will not be contaminated. larger systems under such soil conditions should have a tile field, and absorption can be increased by boring 6or 8-inch holes down to the porous stratum and filling them with gravel or sand; the holes should be 4 to 6 feet apart. another and perhaps the best practice is to excavate the tile trenches 4 to 6 feet and install a lower tile line, as shown in figure 10. this latter method is especially desirable if the upper tight stratum is especially thick, or if there is no porous lower stratum, or if in irrigated regions and where the disposal field is limited in area. where the underdrain tile is not used, the absorption capacity of the field can be increased by providing a rock-filled trench across the lower end of the tiles for the full width of the field. the depth should be not less than 5 feet and the width not less than 3 feet. on account of the beneficial action of bacteria in the upper soil layers it is highly desirable to confine the effluent near the surface rather than to use underdrains. purification becomes slower and less effective, the deeper the drains. in situations where the soil contains considerable moisture or is even saturated, the field may be improved by partially encircling it with a tile line laid to serve as a drain. such a line should be on the high side and have surface outlets for removing the water from the soil. it should not be laid so close to a disposal tile line that it will drain the sewage effluent from the disposal field onto the surface of the ground. [illustration: slope of disposal tile 2 to 4 inches per 100 feet. slope of underdrain tile not less than above. plug upper end of underdrain tile lines, lower end to discharge into rock-filled seepage pit or into other approved outlet. figure 10.--filter trench with underdrains.] when the tile field is underlain by stratified rock or where under-drainage is necessary, advice should be sought from the public health authorities, as regulations in some states may not permit the use of certain methods. care and maintenance of septic tanks a septic tank when first used does not need starters, such as yeast, to promote bacterial action. a good septic tank normally requires no maintenance other than a yearly inspection and an occasional cleaning. frequency of cleaning depends on the capacity of the tank and the quantity and composition of the sewage. tanks of the size recommended in this bulletin may require cleaning at intervals of 3 to 5 years. the tank should be cleaned when 18 to 20 inches of sludge and scum has accumulated. if a drain has not been provided, sludge may be removed by bailing or by pumping with a sludge or bilge pump. it is not necessary to remove the entire liquid contents. burial in a shallow pit or trench with at least 18 to 24 inches of earth cover at a point remote from water sources is the most practical method for disposing of these wastes. a septic tank is intended to handle sewage only. coffee grounds and ground garbage may be included if there is an ample supply of water for flushing and the tank is cleaned more frequently than would otherwise be done. the size of the tank should be increased at least 25 percent if these materials are included in the sewage. =_do not use matches or an open flame to inspect a septic tank, as the gasses produced by decomposing sewage may explode and cause serious injury._= effect of drain solvents and other materials soap, drain solvents, and other mild cleaning or disinfecting solutions used for normal household purposes cause no trouble in the tank. constant use in large quantities, however, and disinfected wastes from the sickroom may prove harmful. wastes from milk rooms, strong chemicals used in sterilizing equipment or in photographic work, and the wastes from filters or water softeners not only reduce bacterial action but also cause abnormally rapid accumulations of sludge and clogging of the tile lines. protection against freezing septic-tank systems seldom freeze when in constant use. warm water and the decomposition of the sewage usually maintain above-freezing temperatures. in cold regions there is trouble from freezing if various parts of the system are not covered adequately. if the system is to be out of service for a period of time or if exposure is severe, it may be advisable to mound over the poorly protected parts of the system with earth, hay, straw, brush, leaves, manure, snow, or the like. in cold regions it is not advisable to install the entire system below frost depth, as this will remove the effluent from the action of the aerobic bacteria in the upper layers of the soil and make the system generally less accessible. new systems put into operation during very cold weather may freeze unless large quantities of hot water are discharged during the first few weeks. septic-tank troubles in sewage disposal, clogging of the disposal field is the most common trouble. this may be caused (1) by a tank too small for the volume of sewage, (2) by failure to clean the tank regularly, (3) by interior arrangement that does not provide slow flow through the tank or that allows scum or sludge to pass out with the effluent, or (4) by a disposal field that is too small or is incorrectly built. the remedy for a clogged disposal field is to dig up and clean the tiles and re-lay them 3 or 4 feet to one side or the other of their former position. sometimes a tile line can be cleaned by opening up the line at each end and flushing it thoroughly with a hose. with this method provision must be made to drain off and safely dispose of the water used for flushing. tile lines laid with improper slope allow the effluent to collect in a limited area and saturate the soil, causing odors. bacteria cannot work in such areas, where the soil becomes sour, or "sewage-sick." these lines must be relaid on the correct slope. odors or a water-logged soil may also indicate that the disposal field is too small. house sewers frequently clog. this is due, in most cases, to roots and less frequently to trash, garbage, or other foreign materials discharged with the sewage. greases in the sewer may cause trouble, especially when the slope is insufficient to give the sewage a cleansing velocity. drain solvents will sometimes remove the obstruction, but more often it is necessary to clean the sewer by rodding. in some cases it may be necessary to dig up the line to reach the obstruction or, at least, to open the line so that it can be rodded from two directions. when it has been cleaned, a manhole could be built for use in case of future trouble. if stoppage is due to roots it may be necessary to re-lay the sewer with root-tight joints, or to move either the sewer or the vegetation so that roots cannot reach the line. grease traps grease traps (fig. 11) are not recommended for the average farm, because they clog easily and require frequent cleaning, but they are desirable for boarding houses and tourist camps where large quantities of grease are produced. the septic tank if of proper design and size will take care of the normal grease from most farm kitchens. the traps must be several times larger than the quantity of greasy water discharged into them at any one time, in order to allow the greases to rise, but they should not be of less than 30 gallons' capacity. the trap is best located in an accessible place in the basement or under the house close to the source of grease and safe from frost. outdoor locations at shallow depths require a covering for insulation against freezing. grease traps should be connected to the kitchen sink only and not to laundry, shower, or water-closet wastes. they must be cleaned periodically for satisfactory operation, and the outlet should be properly trapped. [illustration: figure 11.--typical grease trap.] disposal of drainage from fixtures other than toilets when the farmhouse does not have an indoor toilet but does have a kitchen sink or other similar fixtures, the drainage can be disposed of as shown in figure 12. even where septic tanks have been installed, it is sometimes advisable to have a second disposal field for other fixtures than the toilet, to avoid overloading the tank, especially where large quantities of laundry water are discharged at one time. [illustration: figure 12.--disposal of drainage from kitchen fixtures, using a line of terra cotta or fiber drain tile surrounded with gravel. one or two rock-filled pits at the end of the line increase the absorption area and are desirable where there are several fixtures or the soil is nonporous. the pits may be lined with boards or masonry laid without mortar and provided with a tight cover.] these wastes are not likely to create serious health hazards, but they become nuisances if discharged promiscuously on the ground surface. such drainage should never be permitted on the watershed of a spring. coarse sand and gravel, 12 to 18 inches deep, may be placed on the bottom of the pit, to strain out small particles of solids, which might clog the pores of the soil. if, after a few years, the sand or gravel becomes clogged with solids, it should be replaced with clean materials. if excessive quantities of grease are permitted to enter the sink drain, a grease trap may be advisable. cesspools cesspools are cheap in first cost but high in maintenance costs and often become nuisances. they should be located at least 150 feet from wells, 15 feet from seepage pits and property lines, and 20 feet from dwelling foundations. they should never be used in the vicinity of shallow wells and, in any case, only where permitted by state regulations. the cesspool depends for its action upon seepage into the surrounding soil and consequently is particularly unsatisfactory in tight clay soils. in more open sand and gravel soils the seepage is reduced as the pores of the soil become clogged with particles of solids, until it stops entirely, and overflowing occurs. emptying and then cleaning the walls and floor of a cesspool do not fully open up the clogged soil pores, and overflowing can be expected to occur soon again. solids in cesspools must be removed from time to time by bailing or pumping and should then be buried 18 to 24 inches deep in a trench where the water supply will not be endangered. caustic potash (lye) will to some extent liquefy solids in a cesspool. this treatment does not eliminate the necessity of removing the contents when periodic inspection shows that the cesspool is nearly full. caustic potash converts the greases into soft soap, whereas caustic soda forms a hard soap that does not readily dissolve. the chemical treatment is not effective in liquefying solids in the pores of the soil surrounding the cesspool. [illustration: figure 13.--a neat, whitewashed lattice along the paved walkway provides protection from cold wind and rain and gives added privacy.] when clogging continues and cannot be corrected, in most cases the best solution to the problem would be to abandon the cesspool and install a septic-tank system with tile disposal field. the cesspool should be completely filled with stones, earth, or other solid materials to avoid possible cave-ins.[8] [8] see the septic tank, p. 8. privies a privy when safely located and properly built and maintained is satisfactory for its purpose on the farm. privies should be built 50 to 150 feet from the farmhouse, preferably on the opposite side of the house from prevailing winds, and at least 50 feet from the well. a site downhill from the well is generally safest. in some cases, however, the ground water may flow in a direction opposite to the slope of the surface, in which case the privy should be built on the other side of the well. direction of flow may sometimes be learned from soil surveys, well-driller's data, or other similar sources. a distance of at least 6 feet from fences or other buildings allows for proper mounding of the privy and keeps it away from roof drainage from adjacent buildings. good, tight construction with screened ventilators keeps insects and birds from entering, prevents rapid deterioration of the building, and provides greater comfort for the user. certain features, while not essential to sanitation and satisfactory service, add to personal convenience. a paved walkway, well protected from cold winds and rain, is desirable. a neat, whitewashed lattice, as shown in figure 13, an arbor covered with vines, or a hedge screen adds to privacy. the earth-pit privy is the simplest to build and the one most widely used. it is not generally recommended in localities where underground rock has crevices. for a sanitary type of privy with reinforced concrete[9] floor, riser, and supporting sills see figure 14. because privy units are commonly used as urinals, the use of impervious materials for risers and floors facilitates cleanliness. in the colder climates, wood treated with a preservative is durable and reduces the problem of moisture condensation. therefore, wood could be used if approved by the state department of health. [9] for information on making concrete see farmers' bulletin 1772, use of concrete on the farm. when it is considered impracticable to build the slab and riser of concrete, these parts may be of wood, as shown in figure 16. the building itself may be as shown in either illustration. a wood structure is easy to move to a new location. a pit with a minimum capacity of 50 cubic feet[10] will usually serve five people over a period of 5 to 10 years. the privy should be moved when the pit is filled to within 18 or 20 inches of the top and a strong disinfectant spread in the old pit before covering it with earth. [10] recommended by the committee on promotion of rural sanitation, public health engineering section of the american public health association, 1932. [illustration: figure 14.--sanitary type of privy. detailed plans and a bill of materials for this design can be had from the united states public health service, washington 25, d. c.] it is important to have the earth-pit privy more than 50 feet from the well even where the water table is not near the surface. the ground water should flow from the well toward the privy, and it is important that this direction of flow be determined in advance. wood is most commonly employed for the main part of the building. the ground outside should be sloped as shown, to shed water away from the building, and the roof should extend beyond the walls to shed water away from the pit. care and maintenance all privies require periodic attention. seats and covers should be washed weekly with soap and water or with disinfectants, such as cresol, pine oil, and hypochlorite or chloride of lime. these have deodorant properties and are available at most grocery or drug stores. druggists generally carry a more refined product and consequently the price is higher. during the fly season fly and mosquito eggs will be destroyed by pouring half a pint of crude oil, crankcase oil, fuel oil, kerosene, or borax solution (1 pound powdered borax dissolved in about 10 gallons of water) over the contents of the pit about once a week. [illustration: figure 15.--pit privy of all-wood construction. the sills and riser of this type should either be treated or made of cypress, redwood, cedar, locust, fir, or other decay-resistant wood.] odors from privy pits and vaults can be reduced by covering the contents with dry earth, ashes, manure, or sawdust. these materials fill up the pit rather quickly, but can be used where other deodorants are not available. sometimes two cakes of yeast dissolved in 2 gallons of water are effective in reducing odors. commercial deodorants are available from suppliers of disinfectants. if a person in the family has typhoid fever or is a carrier of that disease or has dysentery, it is advisable to disinfect the excreta. fire, live steam, boiling water, and such chemicals as caustic soda (sodium hydroxide), caustic potash (potassium hydroxide), or hypochlorite or chloride of lime may be used. the heat generated by the slacking of quicklime is also effective. best results are obtained if the infected material is treated prior to depositing it in the privy. further advice may be obtained from physicians, local health officers, or state health departments. chemical closets in general, chemical closets should be used only where there are elderly or infirm people unable to get outdoors, particularly in winter-time. in some localities their use is forbidden by law because of improper maintenance. strict adherence to the manufacturer's directions for making the installation is necessary to obtain satisfactory service. the chief advantage of chemical closets is that they may be within or adjoining the house and used without regard to soil or ground-water conditions. the caustic chemicals required, if used properly, reduce the quantity of solid matter by liquefying action, disinfect and deodorize the contents, and lessen danger from flies. disadvantages are the cost of the chemicals and necessity for careful and constant maintenance. the chemical-tank closet is generally recommended rather than the dry-type chemical closet. three variations of tanks are available commercially. one type contains a clean-out opening in the top of the tank, through which the contents are removed by pumping or bailing. the second type has, in addition to a clean-out opening, a drain valve at the bottom, which is operated by a handle extending to a clean-out opening, so that gravity drainage of the tank is possible. the third type is self-draining; as the excreta are added an equal volume of liquid is spilled out the overflow. the solid matter must be removed manually or through the sludge drain. the last-mentioned type requires frequent addition of chemicals, and the others are recharged after each emptying. the presence of odor is an indication of insufficient chemical or of the need for emptying and recharging. the same precautions apply to selecting an area for disposing of the tank wastes as to disposing of the materials removed from cesspools.[11] since the contents of chemical closets are caustic, they may kill vegetation with which they come in contact. [11] for disposal methods in tight soils, see p. 16. the dry-type chemical closet is cheap, simple, and easy to install but requires frequent emptying. pine tar and coal tar will accomplish only partial disinfection and deodorization, but caustic disinfectants produce liquefication in addition if used in sufficient quantities. the caustic chemicals may cause burns if the receptacle is too full or if spilled where they come in contact with the body. this form of closet is more of an expedient than a permanent installation, and daily care is necessary to prevent the development of insanitary conditions. disposal of garbage and trash domestic garbage and trash on farms can be divided into four classes--(1) waste of plant or animal origin suitable for animal feed, (2) unpalatable plant or animal waste, (3) combustible trash, and (4) noncombustible material. the disposal of these wastes is simplified if the four classes are kept separate. trash to be burned should be kept dry. coffee grounds, tea leaves, citrus rinds, fish heads, entrails, eggshells, and similar material are most readily handled if drained and put in paper sacks. cans should be placed where they will not collect water and become breeding places for mosquitoes. cans will corrode faster if heated sufficiently to burn off all grease. when the trash accumulates it should be hauled to some out-of-the-way place, such as a gully, or buried. neat-appearing garbage containers are desirable for kitchen use and should be small enough to require daily emptying. large containers may be placed within easy reach outside the house and screened with a lattice fence or shrubbery. substantial containers of rust-resistant metal will not quickly become an eyesore and a nuisance. tight covers should be used to keep out prowling animals and to eliminate the habit of tossing wastes from the back door. open or wooden containers are not recommended. a good way to protect the garbage pail is to place it in a small pit that has a manhole frame and a lid that can be raised by foot pedal. a gravel bottom in the pit will assist in draining water away. outdoor receptacles, if emptied and cleaned once a week, generally do not become foul. grease, coffee grounds, and other similar materials that adhere to the sides of containers can be removed by scraping with a little sand prior to scalding. electrically operated units grind garbage and bones and discharge the material through the kitchen-sink drain. they will not handle tin cans, glass, and the like. they may be used on farms if the septic tank is larger than normal and if sufficient water is available for flushing the drain to prevent clogging. garbage to be fed to animals should be preserved as carefully as is human food. to prevent the spread of trichinosis and other diseases, it should be cooked before it is fed to hogs. garbage left uneaten by the animals should be disposed of by one of the methods described above. incineration is the most sanitary method of disposing of farm wastes. garbage, however, is not easily burned. figure 16 shows a type of incinerator[12] suitable for farm homes. details of construction for a brick incinerator are given in figure 17. brick, stone, concrete, or other fire-resistant material may be used. commercial incinerators, some of which are designed to be built into the house, also are available, although these cost considerably more than the home-made type shown. [12] blueprints of this design may be obtained from the extension agricultural engineers at most of the state colleges. a limited quantity of refuse may be burned in a kitchen range or a furnace, but it may cause accumulations of grease in the flue and require frequent cleaning to prevent fire. next to burning, burial is the most desirable method of waste disposal. waste material may be deposited in a trench 3 or 4 feet wide, 7 or 8 feet long, and 4 or 5 feet deep and covered with earth when filled to within 18 inches of the top. if there is no fire hazard, the contents of the trench may be burned. garbage may be included in a compost heap with leaves, peat, manure, and similar materials. the compost pile should be in an inconspicuous place, built up to the desired height with materials that will rot, and then covered with 2 or 3 inches of earth. the top should be level and the sides steep sloping. it is necessary that the material being composted be kept moist; otherwise it will not rot. frequently commercial fertilizer is added to increase the fertilizing value of the compost. ashes and clinkers removed from furnaces should be placed in metal containers to eliminate fire hazard. wood ashes may be spread on the lawn or garden, as they have some fertilizing value. [illustration: figure 16.--a satisfactory incinerator for household use.] [illustration: figure 17.--details of construction of the household incinerator pictured in figure 16.] trash burners of various designs suitable for burning small quantities of paper and rags are available or may be improvised. the main requirements are provision for adequate draft and for preventing the escape of burning paper or live embers. u. s. government printing office: 1948 for sale by the superintendent of documents, u. s. government printing office washington 25. d. c. -price 10 cents * * * * * transcriber note illustrations were repositioned so as to not split paragraphs. transcriber's note italic text is denoted by _underscores_. some minor changes are noted at the end of the book. dirty dustbins and sloppy streets. _a practical treatise on the scavenging and cleansing of cities and towns._ by h. percy boulnois, m. inst. c. e., _member (by exam.) of the sanitary institute of great britain_, city surveyor of exeter. e. & f. n. spon, 16, charing cross. new york, 446, broome street. 1881. james townsend, printer, exeter. preface. some portions of the following pages have already appeared in the monthly numbers of the _sanitary engineer_, and the complete work is now published with a view to assist surveyors of towns and others who are directly engaged in providing that house dustbins shall be regularly cleared, and streets kept clean; and also in the hope that it may be the means of drawing some public attention to the question, thus showing the householder something of what is being done for his welfare by sanitary authorities, and how each individual may assist in the good work, instead of, as is now frequently the case, inadvertently or purposely retarding the execution of some very necessary though unostentatious sanitary measures. i am not aware that any book, or even pamphlet, has yet been written on this subject, and i venture to believe that in these pages there may be found something to interest all readers. h. p. b. exeter, _may, 1881_. contents. chapter i. scavenging. _page_ town scavenging or scavengering--subject divided into 13 heads--public health act, 1875, and its bearings upon the question 1 chapter ii. house refuse. definition of house refuse--the law on the subject--whether trade and garden refuse must be removed by the scavenger--statistics on this point--disputes as to what is trade, garden refuse, or house refuse--suggestions to settle the question--other waste materials 5 chapter iii. the dustbin. the public health act, 1875, on the subject of ashpits--the model bye-laws and six clauses on the same subject--position of the dustbin in respect of the adjacent dwelling-houses--suggestions to burn some of the waste products of a house--objections to the _fixed_ ashpit recommended by the public health act--suggestions for improvements in this direction--movable dust boxes recommended 10 chapter iv. the collection of house refuse. three methods by which this is effected--the law on the subject--statistics on the subject--lay stall accommodation, objections, and advantages--dirty habits of the lower classes--a house to house visitation by the scavengers the best system--if universal, great expense incurred--the bell or signal system--objectionable character of temporary receptacles under this system--state of streets in consequence--suggestions for improvements- specially constructed conveyance and receptacles--advantages of this system both on sanitary and economical grounds--delaying the scavenger--the d signal--convenient hours for the scavengers' visits 17 chapter v. the scavengers' cart. its form and construction--description of the "tip cart"--splashing and dust therefrom--other objections to this form of cart on sanitary and economical grounds--introduction of many new forms of carts and waggons--general description of improvements in their construction--some names of makers of sanitary carts and waggons 27 chapter vi. disposal of house refuse. position of a town with respect to the surrounding district- sale of refuse to farmers and others the most ready and economical means of disposal--site of the refuse depôt--loss of bulk in the refuse at the depôt--difficulty in disposing of old tins, crockery, &c.--replies from 90 towns on the question of disposal of house refuse--condemnation of practice of building over tipped house refuse--destruction by fire--fryer's patent carboniser--dealing with house refuse on a gigantic scale at manchester 31 chapter vii. street cleansing. prosperous appearance of a town--danger of inhaling dust--the law on the subject--who ought to cleanse private courts and alleys?--statistics with reference to this point--number of times streets ought to be cleansed--hand labour or machinery--durability of machines and hand brooms--materials of brooms--construction of streets and traffic affect the question of cleansing materially--returns prepared by the superintendent of scavenging, liverpool--his further remarks on the subject--disposal of road scrapings--street cleansing in paris--the use of disinfectants in paris 46 chapter viii. snow. the density of snow--the amount of snow to be removed in an ordinary street in england--the removal of snow in milan--the removal of snow in paris--suggestions for its removal in england--clearing footways--the effect of salt upon snow--removal of snow in liverpool 61 chapter ix. street watering. watering necessary on sanitary grounds as well as to prevent damage from dust--watering in london--watering by horse and cart--the points of importance to be considered in connection with this service--the diary of a water cart--bayley's hydrostatic van--a description of this machine--its great advantages over the old-fashioned water cart--mr. scott on the subject--a trial in edinburgh- mr. tomkins and bayley's van--a comparative table of effective work by one of these vans--watering streets by ponding water in channel gutters--brown's system of watering--its advantages and objections--watering by hose and reels or by portable iron pipes--watering at reading--watering at paris--use of salt water and other chemicals--watering with disinfectants 73 chapter x. contracts _v._ administration by local authority. opinions on this subject by surveyors of towns--the dust contractor--a model specification of a contract for removal of house refuse--the system of contracts for such work condemned--sanitation first, economy afterwards 86 chapter xi. _£ s. d._ the cost of scavenging--difficulty in fixing any standard of cost--physical character of a town and other causes must be taken into consideration--statistics show very various results--average cost per head of population per annum about one shilling--is hiring horses cheaper than keeping a stud?--reasons in favour of the latter plan--cost of carts, horses, stables, land, &c.--wages of scavengers and carters--depreciation of horse flesh and of plant--a specimen estimate where a stud is kept--another estimate where teams are hired--mr. williams' returns as to cost- list of questions on the subject of scavenging--conclusion 90 chapter i. "scavenging." the word "scavenging," or "scavengering," as it is frequently styled, is a very comprehensive term, as it includes that of house scavenging or the removal of house refuse, and also that of street scavenging, or the sweeping and cleansing of streets, and the carting away of all such materials removed from their surface. in dealing with this subject it will be necessary to consider the following heads, viz.:--(1) what is house refuse, (2) how and in what manner shall it be temporarily stored pending the visit of the scavenger, (3) what are the best methods for its collection, (4) in what manner shall it be eventually disposed of, and (5) the cost of the whole work; (6) which are the best methods for sweeping and cleansing streets, (7) whether machinery is more economical than hand labour, (8) the extra work involved by the ill construction of streets and the materials of which they are formed, (9) whether private courts and alleys not repairable by the sanitary authority should be swept and cleansed by them, (10) the ultimate disposal of excessive accumulations of mud, (11) the removal and disposal of snow, (12) the watering of streets, and (13) the cost of all such work. the public health act of 1875 contains several clauses bearing on the subject of scavenging and the cleansing of streets, and sec. 42, part iii., enacts as follows:-"every local authority may, and when required by order of the local government board shall, themselves undertake or contract for-"the removal of house refuse from premises; "the cleansing of earth closets, privies, ashpits, and cesspools; either for the whole or any part of their district. "moreover, every urban authority and rural authority invested by the local government board with the requisite powers may, and when required by order of the said board shall, themselves undertake or contract for the proper watering of streets for the whole or any part of their district. "all matters collected by the local authority or contractor in pursuance of this section may be sold or otherwise disposed of, and any profits thus made by an urban authority shall be carried to the account of the fund or rate applicable by them for the general purposes of this act; and any profits thus made by a rural authority in respect of any contributory place shall be carried to the account of the fund or rate out of which expenses incurred under this section by that authority in such contributory place are defrayed. "if any person removes or obstructs the local authority or contractor in removing any matters by this section authorised to be removed by the local authority he shall for each offence be liable to a penalty not exceeding _five pounds_: provided that the occupier of a house within the district shall not be liable to such penalty in respect of any such matters which are produced on his own premises and are intended to be removed for sale or for his own use and are in the meantime kept so as not to be a nuisance." section 45 also enacts that "any urban authority may, if they see fit, provide in proper and convenient situations receptacles for the temporary deposit and collection of dust, ashes, and rubbish; they may also provide fit buildings and places for the deposit of any matters collected by them in pursuance of this part of this act." the act also gives the power to local authorities to make bye-laws with respect to the cleansing of footpaths and pavements, the removal of house refuse and the cleansing of earth closets, privies, ashpits, and cesspools, and the prevention of nuisances arising from snow, filth, dust, ashes, and refuse. it will thus be seen that the legislature find it necessary to frame laws for the proper execution of scavenging by every local authority, and we shall see in the following chapters how further clauses in the public health act, as well as in many private improvement acts and also in bye-laws, detail the manner in which this work ought to be properly carried out. i shall further endeavour to show where errors in the working now exist, and give some suggestions that would, in my opinion, be, if carried out, improvements upon the present systems. chapter ii. house refuse. now the first question that presents itself to us is: what is house refuse? and how is it to be defined? for unless this point is satisfactorily settled, great onus and expense will be put on the local authority if they are to be compelled to remove all trade, garden, and other refuse in addition to what may be legally entitled house refuse. section 4, part i., public health act, 1875, contains the following definition of the word house: "house" includes schools, also factories and other buildings in which more than twenty persons are employed at one time. but all that is apparently said in reference to the definition of refuse is to be found in "glenn's public health act," 1875, where in a foot note to section 44, part iii. of the before named act, is the negative argument "what is not refuse:" and describes one or two cases in which it was held that certain ashes from furnaces, etc., were to be designated as "trade refuse," and further says "that the intention of the act was that only the rubbish arising from the domestic use of houses should be removed." on reference, however, to some local improvement acts, it appears that the definition is given more in detail, for we find that house refuse is there described as "all dirt, dust, dung, offal, cinders, ashes, rubbish, filth, and soil." we may thus, we imagine, be fairly content with these definitions, and may assume that all house refuse legally so designated, and which it is the duty of the scavenger to remove, is really so removed by the direction of the local authority without dispute, but that the following articles, which frequently find their way into a domestic dustbin, are not in the strict terms of the act expected to be removed by the scavenger, viz., (1) plaster from walls and brick bats, (2) large quantities of broken bottles and flower pots, (3) clinkers and ashes from foundries and greenhouses, (4) wall papers torn from the rooms of a house, (5) scrap tin (but not old tins which have contained tinned meats and which, although very objectionable and bulky, may be fairly assumed to be house refuse), and (6) all garden refuse such as grass cuttings, dead leaves, and the loppings from trees and shrubs. the bromley local board issue a card on which is printed, amongst other information with reference to the contract for the removal of house refuse, the following:--"it is hoped that householders will as far as possible facilitate the systematic removal of refuse by providing suitable dustbins, and directing their servants that ordinary house refuse only shall be deposited in such receptacles. the following are some of the items of refuse which the contractors are bound to remove, viz.:--cinder ashes, potatoe peelings, cabbage leaves, and kitchen refuse generally. but the contractors are not required to remove the refuse of any trade, manufacture, or business, or of any building materials or any garden cuttings or sweepings." some valuable statistics have recently been prepared by me from answers obtained from upwards of ninety of the principal cities, and towns in england, in reply to a series of questions which i addressed to the local surveyors on the subject of scavenging, and on referring to these statistics it is found that out of these ninety towns, the authorities of only thirteen of them direct the removal of both trade and garden refuse without any special extra payment being made by the householder, but that this is only done when these materials are placed in the ordinary dustbin or ashpit attached to a house. several towns, however, it appears remove such materials on special payments being made of sums varying from 1s. 6d. to 3s. per load. disputes frequently arise between the men employed in scavenging and the householder on these vexed questions as to the difference between house, trade, or garden refuse, a dispute often raised by the scavengers themselves, in the hope of obtaining a gratuity or reward for the clearance of a dustbin which no doubt, legally, they are perfectly justified in refusing to empty, and in order to lessen the chance of such disputes and to attempt to settle this question the following suggestions may be of value. it would no doubt be vexatious if any sanitary authority were to absolutely refuse to remove the "garden" refuse from those houses to which a small flower garden was attached, whilst it would on the contrary be an unfair tax upon the general community if the refuse of large gardens was removed without payment. a good rule would therefore be to remove only such _garden_ refuse as was contained in the ordinary dustbin or ashpit attached to a house, and that as the removal of any kind of _trade_ refuse would no doubt lead to abuses if done gratuitously by the sanitary authority, that this material should only be removed on payment of some sum, which should be previously fixed by the local authority, and each case should be reported to the officer superintending the work before it was removed. there are, of course, in addition to the ordinary house refuse the waste materials from the surface of the streets, and from markets and slaughter-houses, which have to be collected and disposed of by the local authority, but these materials should be collected in a special manner, independently of the ordinary removal of the house refuse. chapter iii. the dustbin. the next question that we have to consider, having thus far discussed the subject of "what is house refuse," is the important one of the manner and place in which it shall be temporarily stored pending the visit of the scavenger. i will begin as i did in the former case by turning to the law on the subject, and find out if it can help us. section 40, part iii., of the public health act of 1875 enacts that: "every local authority shall provide that all drains, water-closets, earth-closets, privies, _ashpits_, and cesspools within their district be constructed and kept so as not to be a nuisance or injurious to health." and section 35 of the above act states, "it shall not be lawful newly to erect any house or to rebuild any house pulled down to or below the ground floor without a sufficient water-closet, earth-closet, or privy, and an ashpit furnished with proper doors and coverings. any person who causes any house to be erected or rebuilt in contravention of this enactment shall be liable to a penalty not exceeding twenty pounds." the act also gives power to local authorities to enforce provision of ashpit accommodation for houses where such accommodation does not already exist, and to frame bye-laws with respect to ashpits. in the year 1877 the local government board issued a series of model bye-laws for the use of sanitary authorities, and no. iv. of this series, which is upon "new streets and buildings," contains the following six lengthy clauses, regulating the position of an ashpit with reference to a dwelling-house or public-building, or to any water supply, and for the purpose of removing its contents without carrying them through any dwelling-house, &c.:-"80. every person who shall construct an ashpit in connection with a building shall construct such ashpit at a distance of _six feet_ at the least from a dwelling-house or public building, or any building in which any person may be, or may be intended to be employed in any manufacture, trade, or business. "81. a person who shall construct an ashpit in connexion with a building shall not construct such ashpit within the distance of __ _feet_ from any water supplied for use, or used or likely to be used by man for drinking or domestic purposes, or for manufacturing drinks for the use of man, or otherwise in such a position as to endanger the pollution of any such water. "82. every person who shall construct an ashpit in connexion with a building shall construct such ashpit in such a manner and in such a position as to afford ready means of access to such ashpit for the purpose of cleansing such ashpit, and of removing the contents thereof, and, so far as may be practicable, in such a manner and in such a position as to admit of the contents of such ashpit being removed therefrom, and from the premises to which such ashpit may belong, without being carried through any dwelling-house or public building, or any building in which any person may be, or may be intended to be employed in any manufacture, trade, or business. "83. every person who shall construct an ashpit in connection with a building shall construct such ashpit of a capacity not exceeding in any case _six cubic feet_, or of such less capacity as may be sufficient to contain all dust, ashes, rubbish, and dry refuse which may accumulate during a period not exceeding _one week_ upon the premises to which such ashpit may belong. "84. every person who shall construct an ashpit in connection with a building shall construct such ashpit of flagging, or of slate, or of good brickwork, at least _nine inches_ thick, and rendered inside with good cement or properly asphalted. "he shall construct such ashpit so that the floor thereof shall be at a height of not less than _three inches_ above the surface of the ground adjoining such ashpit, and he shall cause such floor to be properly flagged or asphalted. "he shall cause such ashpit to be properly roofed over and ventilated, and to be furnished with a suitable door in such a position and so constructed and fitted as to admit of the convenient removal of the contents of such ashpit, and to admit of being securely closed and fastened for the effectual prevention of the escape of any of the contents of such ashpit. "85. a person who shall construct an ashpit in connexion with a building shall not cause or suffer any part of such ashpit to communicate with any drain." there can be no doubt that the position of the dustbin or ashpit, as regards its site with reference to the main dwelling-house, is of primary sanitary importance, for if the garbage and domestic accumulations therein are allowed to remain for a few days, especially when the weather is close, damp, and warm, they become very offensive, and the emanations therefrom may even be highly deleterious and dangerous to health; this effect is aggravated by persons emptying vegetable refuse and other matters which are _wet_ into the dustbin, as decomposition of these matters is greatly assisted by this addition, and it would be well that all such matters should be burnt on the kitchen or scullery fire along with a large percentage of the ashes which could be sifted and saved from those which too readily find their way into the dustbin, and are thus wasted. care would of course have to be taken in this process that no smell or nuisance was caused by burning this refuse, but the greatest difficulty would arise in overcoming the time-honoured prejudices of the domestic servant who usually finds the dustbin or ashpit the most convenient and least troublesome place to dispose of nearly everything that to her may be entitled rubbish. now with all due respect to those who framed section 35 of the public health act of 1875, it is open to considerable doubt whether the _fixed_ dustbin or ashpit, as it is there styled, is the best and most sanitary receptacle for the house refuse. they may be necessary and suitable for public institutions, or for large isolated private dwellings, or for schools or any places where excessive quantities of refuse may accumulate, but where this refuse is systematically and properly removed by the order of the local authority, at such times and in such manner as will be hereafter pointed out, a movable or portable dustbin, box, or basket, is far preferable to the large immoveable inconvenient fixed ashpit, recommended and enforced under the act. this portable dustbox should be of such dimensions that the men employed in removing the refuse could easily carry it out and empty its contents into the cart, and there is nothing to prevent more than one being provided, if it is found insufficient for the requirements of the household. the box should be made of iron, or wood or basket lined with tin, or some equally impervious material, so that it can easily be washed out and thoroughly cleansed and disinfected when found necessary to do so, a matter very difficult to accomplish with the fixed ashpit. the _whole_ of its contents could be quickly emptied, which is more than can be easily effected with the fixed ashpit, and then only when very special arrangements are made for its drainage. the movable dustbox can, in addition to these advantages, be placed in any part of the premises, and may be covered or not as may be deemed desirable, and need not, like many of the existing ashpits, be fixed in such a position as to appear to have been thus placed for the express purpose of poisoning with its foul smell the whole of the inhabitants in its vicinity. the movable box can also be readily taken out to the scavenging cart by the householder himself, a very essential requisite, as will be shown in the next chapter. chapter iv. the collection of house refuse. the collection of house refuse should be done satisfactorily, expeditiously, and economically. at the present time there seem to be only three methods by which this is attempted to be effected; they are as follows:-(1.) by a house to house call at intermittent periods. (2.) by the scavengers giving notice of their approach by ringing a bell or by other signal, and requiring the householder to bring out the refuse to the cart, and (3.) by placing public dustbins in different localities, and expecting householders in their vicinity to place the house refuse in these dustbins, which would then be cleared from time to time by the local authority. the law is silent on the subject of what may be considered as an efficient collection and removal of house refuse, and experience only can teach us the best manner of thoroughly effecting this work without losing sight of the economical side of the question; but it appears, on again referring to the table of statistics which have been previously mentioned, that nearly all the towns adopt the two first methods mentioned above for the removal of the house refuse, but that very few of them are able to adopt any public dustbins or "lay stall" accommodation for the temporary reception of the refuse, not only on account of their first cost, but also from the difficulty of finding suitable positions for them. this latter objection to the adoption of public dustbins arises in great measure from the fact that they are usually constructed of galvanised iron in the form of open boxes or troughs, which are readily accessible to young children and poultry, who often scatter their contents in every direction, and they are also generally open to the view of the inhabitants of the courts, and to passers by, whose "morale" it is found is certainly not improved by constant familiarity with the sight of filth. if these dustbins were constructed with properly balanced self-closing lids, these objections would be overcome, and their first cost would be but trifling when compared with the benefit to be derived by placing them in some of the thickly populated courts and alleys which are unfortunately to be found in nearly every town. where there are no public dustbins the inhabitants of these courts throw their waste products upon the surface of the streets or courts, from time to time throughout the day, as it cannot be expected nor desired that such materials should remain, even for twenty-four hours, in their one living room, which is frequently over crowded, and has but little spare space even for the common necessities of life; but that these waste products should be thus strewn over the surface of the street or court is almost equally objectionable, and points to the enormous advantage to be gained by placing in convenient situations the covered dustbins that are described above, the contents of which could be easily emptied once a day. the greatest difficulty would be found to be that of inducing the inhabitants to take the trouble to carry their house refuse to the dustbin, but they might be gradually educated up to this standard of cleanliness, and a few persons judiciously summoned and punished "pour encourager les autres," when detected in throwing any of their waste products on to the surface of the street or court, would no doubt have a very beneficial effect in assisting their education. with reference to the question of a house to house call or visitation by the scavengers for the purpose of removing the refuse. this is no doubt the method "par excellence" of all the systems for its effectual removal without much trouble to the householder, but except in suburban districts and for the collection of refuse from the better class of dwelling-houses and public institutions, the expense, delay, and difficulty which would be incurred in calling at every house throughout a town, would make it almost impracticable, and consequently this system is universally combined with that which is known as the bell or signal system, which simply means that the scavenging cart in going its rounds has a bell attached to it, or the horse, which bell rings automatically as the cart proceeds on its way; or the man in charge blows a trumpet, or calls in stentorian tones, "dust oh!" on hearing this signal, _but not before_, the householder is expected to bring out the refuse in some convenient receptacle, which is then emptied into the cart by the scavenger. as a matter of fact, the receptacles containing all the waste products of these householders are brought out and are placed in the gutter of the street close to the kerb, long before the cart makes its appearance or can be reasonably expected to do so. these temporary receptacles are, as may be easily imagined of various sizes and shapes, and are composed of various materials. on one side you may see a well and suitably constructed galvanized iron box, with handles and cover complete, on the other an old band box, cigar box, or tin saucepan. the result of these inappropriate receptacles filled with heterogeneous collections of house refuse being left unprotected in the public streets, is that their contents are quickly strewn about the surface of the street, either by their being upset accidentally, or purposely, by persons who gain a precarious livelihood by abstracting therefrom, and selling rags, bones, and similar articles, or by the dogs, ever on the alert for a hasty and disgusting meal, and the appearance of the street which has probably been carefully swept and garnished during the night or early in the morning, quickly assumes, especially in a high wind, a very offensive character, and probably has to be entirely re-swept and cleansed before the ordinary traffic of the day commences. to obviate these evils arising from this practice almost universally adopted, i suggest the following plan:-a specially designed frame or carriage must be constructed somewhat similar in appearance to a timber waggon; this must be furnished with a number of strong iron hooks, with or without simple lifting gear, according to the strength and sizes of the receptacles hereafter described. upon these hooks are to be hung cylindrical shaped galvanized iron boxes with balanced covers, and hopper-shaped mouths, and of such cubical capacity as may be found to meet the requirements of any district choosing to adopt my system. the _modus operandi_ would be as follows:--the waggon should be drawn through certain selected streets at about 6.30 a.m.; the boxes or cylinders unhung from it, and placed in such suitable and convenient positions as may be found necessary; their distance apart may be about that of the ordinary street lamp posts, and their position may be in the street channel gutter close to the kerb of the footpath; they should be allowed to remain about a couple of hours, during which time the householders in the vicinity of the boxes would be expected to empty into them all the sweepings, garbage, and house refuse from their premises; at the end of this time the waggon would again appear, and the boxes or cylinders would be attached to the hooks, and be taken to the nearest refuse depôt. there are many advantages to be gained by adopting my proposed system, the principal one being that of preventing the disgusting practice of allowing the foul refuse from houses, to be openly displayed in the public streets, in the manner previously described, and in preventing the possibility of such refuse being allowed to stay for a single instant upon the surface of the street, where even if it is afterwards carefully removed, an ugly stain is almost sure to remain for many hours afterwards. another advantage would be the great convenience to householders of that of having a ready receptacle for their refuse, only a few yards at the most from their doors. the saving of time also in the collection would be considerable, as the scavengers need not wait one single moment beyond the time required to attach the cylinder to the waggon, and there is in addition the cleanliness with which this operation could be performed, thus conferring a great boon on the foot passengers in the streets, who, under the present system, are often half smothered by the dust when the scavengers are engaged in emptying the contents of the usual inappropriate receptacles into the ordinary dust cart. the facilities also for cleansing or disinfecting the cylinders would be undoubted, and the economy, not only in time but in actual expense over the existing system, would be considerable, for the cylinders would last a long time without repairs being needed; not so the ordinary dust cart, which speedily wears out, principally from the fact that the "tipping" necessary to empty it of its contents, is highly detrimental to its stability. having thus shown a method by which the collection of house refuse in crowded streets, where a house-to-house visit is impracticable, can be materially improved, i will pass on to the present system of the collection of refuse in the suburban and rural districts of a town by a house-to-house call. a great improvement in this system would no doubt be effected by adopting the movable dust boxes i suggest in the chapter on "the dustbin," as great delay and consequent expense would be saved thereby, and the work would be altogether more effectually and properly performed, but it is also found that very frequently the scavengers on calling at a house for the purpose of removing the accumulated refuse, are told by the servant that they cannot be admitted, either because it is an inconvenient hour, or that it is washing day, or that being a wet day the scavengers' boots are too dirty to walk over their clean passages or floor, or that the dustbin is not full, and that they must call another day, or some other equally plausible excuse, so that the visit is a useless one, and time is lost. another evil arising out of this is also the fact that as the scavenger's cart has usually a regular round, a fruitless visit as described, results in the dustbin remaining uncleared for perhaps another week, or even more, a state of things not at all to be desired. in order to assist in obviating the chances of such useless visits by the scavengers, i would suggest a very simple remedy, which has already been tried in some towns with considerable success. it consists in the householder placing a card bearing the letter d, or some other distinguishing mark, in a conspicuous place in a window, when the services of the scavengers are required; these cards should be printed and circulated by the sanitary authority of the district, who should state on the back of the card the days on which the scavengers would visit each neighbourhood, with the approximate hour of the day in which they would appear, in each road or street if practicable, in order that the householder may not be unnecessarily inconvenienced by being obliged to keep the card for any length of time in his window. the scavengers in passing, observe the signal, and call at the house, otherwise they pass on, unless specially called in by the occupants, thus avoiding any unnecessary delay in their rounds. a visit from the scavengers either before seven or after ten in the morning is generally very inconvenient for households of a superior class, and should be, if possible, carefully avoided by the sanitary authority. chapter v. the scavenger's cart. the next question that presents itself to our notice is that of the form, style, and construction of the cart usually employed in this work of house refuse collection, and whether it is well suited for the requirements of the work or otherwise. the cart usually employed is that known as the ordinary "tip cart," strongly, if not clumsily, constructed of an oak frame, with elm or deal sides of considerable height; it holds about a couple of cubic yards of materials, and generally costs from sixteen to twenty pounds. these carts are not only clumsy and heavy, but they give an overweighted diminutive appearance to the horse between the shafts, especially as the quality of horse employed for work of this character is frequently none of the best, and as a matter of fact the cart is so ill-balanced that the bulk of its weight is thrown upon the back of the horse. the height, too, of the cart is often so great as to necessitate the use of a short ladder, up which the scavenger has to climb, before he can discharge the contents of his basket into the cart, sending in the process a shower of offensive dust in every direction, far from pleasant for those unfortunate persons who happen to be passing near the spot at the time. when used as "slop" carts the same objections arise, as in this case the liquid mud is splashed in every direction, owing to the height to which it has to be thrown by the shovel of the scavenger. some difficulty is also experienced in thoroughly covering over the contents of the cart, so that not only shall it be hidden from the eye, but that it shall prevent either the liquid mud from being spilled on the ground, or if the cart is being used to convey either dust or house refuse, to prevent the contents being blown about, or dropped upon the surface of the street. the imperfect mode at present adopted is to cover the cart with a tarpaulin, which is tied down as tightly as the circumstances of the case will admit, but which as a rule does not effectually answer the purpose for which it is intended. in towns where the house refuse is not collected separately from the road scrapings, a judicious mixture of the two in the cart considerably assists in preventing any mud slopping or dust blowing. the material being wood of which these carts are constructed, it becomes a difficult matter either to effectually cleanse them after use, or to properly disinfect them, which in times of any serious outbreak of an epidemic is essential to the sanitary well-being of a community. the employment also of wooden carts for this work is bad economy, their rough usage, and the mode adopted for emptying them by "tipping," rendering their life but a short one, a cart in constant work frequently costing from four to five pounds per annum in repairs, and having but very little of the original material of which it was constructed left in it at the end of six years. with a view to obviate these and other objections, several improved carts and waggons have been introduced by different makers, who have styled them by a variety of names, in order to recommend them to the notice of the public. amongst other names they are called dust carts, general purpose carts, sanitary carts, slush carts, tumbler carts, mud waggons, tip waggons, slop waggons, &c. they are generally constructed with iron bodies fixed upon wooden frames on wheels; they are of various forms and designs, the principal objects aimed at being lightness of construction combined with strength, so balanced as to bear with a minimum of weight upon the horse; economy in their cost has not been lost sight of, and they are usually provided with some special means for emptying, either by being completely inverted by a chain and windlass, or by some mechanical arrangement of the tailboard; they are built very low upon their axles, so as to be easily filled, are either completely covered over with a moveable lid, or are fitted with hinged side boards, so as to prevent any splashing over of their contents, and as they are nearly all constructed with iron, they are easily cleansed and disinfected whenever it is thought necessary to do so. amongst others i may mention the following firms who have made the construction of these sanitary carts and waggons a speciality:--messrs. bayley & co., newington causeway, london; messrs. cocksedge & co., of stowmarket; the bristol waggon works company; and messrs. smith & son, of barnard castle, yorkshire. chapter vi. disposal of house refuse. having proceeded thus far with my subject, the very important question next arises as to the manner of the disposal of the house refuse after it has been collected by the local authority, both with regard to its sanitary aspect and also to that of economy. so much depends upon the position of every town and the character of the district in which it is situated, that no hard and fast lines can be laid down in reply to this question, if, however, the town is fortunate enough to be the centre of an agricultural district, or there are ready and economical means of conveying the refuse there, no difficulty should be experienced in disposing of it, if not altogether at a profit, at least at a small loss upon the cost of collection, as farmers and market gardeners will readily buy house refuse at prices varying from sixpence to three shillings a load to use as a top dressing or manure upon their land, and a very rich and fertilizing manure it makes, notwithstanding the outcry that is sometimes raised against it that it produces rank weeds, owing to the seeds of such vegetation being found in every domestic dustbin, the fact really being that all manures will foster and help the growth of weeds, as well as cereals or roots, and the appearance of a prolific crop of weeds points rather to bad and careless farming than to the use of inferior manure. in order to suit the convenience of the customers for refuse, and in order to prevent any delay in its collection from the houses, it is necessary for every town to provide one or more depôts in which the refuse may be so deposited from day to day as it is collected. the site of each depôt should be very carefully selected, bearing the following requisitions in mind:-they should not be at greater distances from the town than would allow the carts to make from three to four journeys a day, and it is evident that their position should, so much as possible, avoid the necessity for the carts to pass _through_ the town when full; they must also be placed so as to be readily accessible to the carts and waggons of the farmers, the customers, and above all, they must be so situated with regard to any dwelling-houses or public roads as not to cause any nuisance, or be injurious to health in any possible manner, and for this purpose a knowledge of the prevailing wind in that neighbourhood would be useful, and care must also be taken that no stream or water-course from which the supply of any drinking water is obtained is likely to become polluted by having such an unpleasant neighbour as a "refuse depôt." the depôt need only be an open field securely railed off against trespassers or pilferers, but as it generally swarms with countless numbers of rats, it is just as well that no stacks or barns should be erected in its vicinity, if their owner has any wish to preserve his corn. in this depôt, the site of which has been selected with all due care, the refuse should be made up into measured heaps, a convenient size for them being found to be twelve feet square by six feet high; these heaps are then sold as they stand to farmers and others who send their carts and waggons to remove them, thus preventing any possibility of mistake or dispute arising as to the number of loads each customer pays for and receives. the refuse, when first brought into the depôt, is far more bulky than it afterwards becomes, and it shrinks nearly twelve per cent. after a few months' exposure to wind and rain; it is therefore necessary to unload each cart as it arrives from the town on to an enormous heap or mound, from the other end of which the measured heaps are made up after the material has become stale and sunken. another cause for the shrinkage and reduction of bulk of house refuse after reception at the depôt is the necessary removal of all the old tins, broken crockery, broken flower pots, &c., before it can be sold to the farmer, and a very difficult matter it is to know how to deal with this heterogeneous mass of absolutely useless articles thus left behind, unless they can be used for bottoming roads, or for agricultural or for deep land drainage, or for filling up hollows of land not afterwards intended to be built upon, when these materials would be very useful and acceptable for such purposes, otherwise they must be kept and allowed to cumber the ground until some such use can be assigned to them. all towns are not so conveniently situated with regard to their surrounding neighbourhood, as will permit their authorities to sell the collected house refuse to farmers, market-gardeners, or others, for use as manure, and in such cases, where they cannot do so, other measures must be resorted to, in order to dispose of it in the most economical and sanitary manner. among the numerous questions that i addressed to the various towns of england when engaged in preparing the returns to which reference has already been made, was one to the following effect:--"how is the refuse disposed of after collection?" many and various were the replies to this. amongst them were the following:-in many towns it is stated that the whole of the refuse is used by brick makers, in others it is simply "tipped to waste." in one case the answer is, "sold by auction twice a year," but to whom it is sold, and for what purpose, does not transpire. in some towns it appears to be mixed with lime and used as manure upon the fields, and in others it is mixed with the sludge of the sewage farms, and is then ploughed or dug into the soil of the farm. this seems a better plan than that of another town, where it is "given or thrown away," although the difficulty of disposing of the old iron, tins, &c., is not touched upon in any of the foregoing answers. the next reply states that "it is riddled, and the cinders and vegetable refuse are burnt to generate steam, the fine dust is used with the manure manufactory (tub system), the old iron is sold, and the pots, &c., used for the foundations of roads." in one case the whole of the refuse is taken out to sea in hopper barges, and sunk in deep water. in a great number of towns it is sold by tender for the year, but what eventually becomes of it does not transpire. but the most favoured methods, where it cannot be sold as manure to farmers, seem to be either that of carting it away to some spot outside the town, and there using it for the purpose of filling up hollows and depressions, or that of giving or selling it to brick-makers. the practice of filling up hollow places with either house refuse or street sweepings cannot be too strongly deprecated, as it stands to reason that some object is in view when these hollows are thus filled up, and we may be sure that the object is that of transforming inconvenient and impracticable pieces of ground into convenient building sites, whereon, sooner or later, eligible villas make their sudden appearance, almost with the rapidity of aladdin's palace, under the magic hand of a jerry builder, and woe betide the unfortunate being who, struck with the pretentious appearance and low rent of one of these eligible family residences, takes up his abode therein, for so surely will disease, and perhaps death, be his visitor. i will not here enter into the details, or describe the medical reasons why such sites are unhealthy for dwelling-houses, as the fact is almost self-evident, and the practise of using either house refuse or street sweepings for such a purpose has been condemned by sanitary experts over and over again. but i will pass on to describe a method of disposal of town refuse which is now gaining some popularity in localities where difficulties are experienced in getting rid of the refuse by any of the means to which reference has been made, and which up to the present time seems to be the best solution of the difficulty. i allude to the process of the destruction of the refuse by fire. with this object in view a mr. fryer has invented an apparatus which he styles a "patent carboniser, for the conversion of garbage, street, and market sweepings, also other vegetable refuse into charcoal." this apparatus consists of a structure somewhat resembling, externally, a brick kiln. it is divided into hopper-shaped compartments, which at the bottom are furnished with a furnace, fitted with a reverbatory arch. a fire is lighted in this furnace, the necessary combustion being obtained, and the heat maintained, by burning the cinders, which are sifted out of the house refuse for this purpose. all the street sweepings, refuse, garbage, &c., is then thrown in at the top of the kiln, and it is there and then completely destroyed by the action of the fire, and converted into charcoal, which is withdrawn through a sliding door fixed at the bottom of the kiln. the inventor further contends that his carboniser not only burns everything within it so thoroughly and completely as to produce effectual deodorisation, but also that in the process all noxious gases which may be driven off the burning organic matters contained in the refuse are themselves burnt and destroyed. mr. fryer has also patented another apparatus which he calls a "destructor for reducing the bulk for purifying and fusing mineral refuse of towns, the residue to be converted into concrete or mortar." this apparatus is somewhat similar in construction and mode of action to the "carboniser," except that it has no tall kiln containing the hopper-shaped compartments. great heat is, however, necessary in order to fuse the mass of heterogeneous articles that are thrown into it, and its success is greatly dependant upon such heat being constantly and efficiently maintained. it is said that the cost of an establishment to dispose of the refuse by this means, consisting of one six celled destructor and an eight-celled carboniser, boiler, steam engine, mortar pans, cooler, chimney, shaft, and buildings, is about £4,500. each cell is stated to deal with about 50 cwt. of refuse in every twenty-four hours, and that no nuisance is experienced in the vicinity of the depôts. this apparatus has, i understand, been adopted in kralingen, leeds, blackburn, bradford, warrington, and derby, and is about to be adopted in other important places. it is not my intention here to describe or to discuss the question of the collection and disposal of night soil, which in many towns is intimately connected and amalgamated with the collection of house refuse and the cleansing of streets. it is a subject of sufficient importance to be dealt with separately. the following particulars, however, with reference to the collection of house refuse in connection with the pail system at manchester will not be out of place, especially with regard to the reference which is made to fryer's carbonisers and destructors, and it must be borne in mind that the refuse here spoken of is _wet_, which makes the difficulties connected with its destruction by fire greater than it would be if only dry, or comparatively dry, house refuse had to be destroyed. these particulars are gleaned from a report contained in a copy of the _british architect_, of 1876, of a visit by the members of the manchester scientific and mechanical society to the works of the manchester corporation health committee, the figures being altered so as to conform more closely with the growth of the work since that year. there are about 56,000 closets in manchester, 44,000 of which have been constructed on the cinder sifter principle, and are emptied during the day, the remainder are emptied during the night. the contents of the new closets are brought away by vans specially constructed for the purpose, having five compartments, one of which is open and uncovered, and this receives the dry refuse; the other four compartments are covered and enclosed with tightly fitting doors. each of these compartments holds six galvanised iron pails, which are also covered with closely fitting lids. the van bottoms are panelled, and the inside of each panel is filled with a layer of carbolic acid powder, one inch thick, and they are thoroughly cleansed after each journey. the health committee employ 100 of these vehicles, each one making four journeys per day. the contents of the closets which are emptied during the night are taken away in open carts, two-thirds to the tips and the remainder along with the refuse brought into the yard by the vans, is sent each night into the country. the amount of material dealt with each week by the health committee is about 3,000 tons, and may be described as follows:--paper, 1 ton; rags, 3 tons; dead animals, dogs, cats, rats, mice, guinea pigs, &c., 2 tons; stable manure, 17 tons; meat tins, old tin and iron, 33 tons; refuse from slaughter-houses and fish shops, &c., 60 tons; broken pots, bottles, and glasses, 80 tons; vegetable refuse, door mats, table covers, floorcloths, old straw mattresses, 100 tons; fine ashes, 1,230 tons; cinders, 1,400 tons. the committee employ in this department over 500 men, including clerks, inspectors, wheelwrights, smiths, saddlers, tinmen, engineers, mechanics, manure and mortar makers, stablemen, and labourers. they have 156 horses, and about the same number of vehicles of various descriptions. when the loaded vans reach the yard, they are first weighed, afterwards they are taken on to the first floor of a two-storey building, where the dry refuse from the open part of each van is unloaded and shovelled on to sieves worked by steam power. by this arrangement the fine dust widely diffusing itself in its descent, falls on to the floor below, covering the contents of the pails, which are, at the same time, being emptied on to grids fixed in the floor. at one end of these grids the bars are set much more closely together than at the other, and serve to convey the liquid portion of the contents of the pails by means of troughs to a tank where it is further dealt with. the solid portion of the excreta falls through the wide-barred portion of the grid into suitable receptacles. the rough portion of the dry refuse, after being separated from the fine, is carried along a movable and endless table to the mortar mills, the boiler, or to one of the various furnaces, of which there are several in the yard. this dry refuse is of such a heterogeneous character as to require various modes of treatment. it is made up of paper, rats, meat tins, straw, cabbage leaves, onions, apples, turnips, fish bones, dead cats, rabbits, guinea pigs, fowls, brush heads, old boots, old books, knives, forks, spoons, children's toys, old hats, old bonnets, crinoline wires, umbrella frames, broken pots, broken bottles, preserve jars, medicine bottles, old mattresses, cinders, bits of coal, firewood, bass, broken bricks, and a host of other articles too numerous to mention. when this mass of rubbish is somewhat assorted, the cinders are separated and used for fuel for the boilers and furnaces (no coal whatever is allowed in the yard), the remaining portion of the rubbish along with some most vile and abominable matter which occasionally comes to the yard in the pails, is taken to the carbonisers (of which there is a nest of eight in the yard), and the obnoxious material is therein carbonised and is resolved into a perfectly harmless material. in another part of the yard is a second set of furnaces which are called destructors, and are used for the purpose of destroying rubbish, which before-time, for many years past, has been deposited in large heaps in every suburb of the city, to the great annoyance of the inhabitants whose fate it was to live in the vicinities of these deposits. these destructors not only consume this objectionable material, but they furnish heat to a concretor which is placed in close contiguity. the spent fuel is carted to the mills, and is there converted into mortar--a mortar, too, of the best description--as the samples of brickwork built with it and exhibited abundantly testify. this concretor, which is driven by steam power, is a large cylinder of a peculiar internal construction, which exposes an extensive evaporating surface to the heat from the destructor, which passes through the cylinder from end to end. the work of this concretor is to subject the urine or liquid portion of the contents of the pails fed by means of the troughs already spoken of in connection with the tank. the urine is pumped from this tank into the concretor at the rate of about 150 gallons per hour. the concentrated urine, which contains a large quantity of ammonia, is mixed with two-thirds its weight of charcoal, and the composition forms a most valuable manure. the carboniser, the destructor, and the concretor have all been invented and patented by mr. alfred fryer, of the firm of manlove, alliot & co., engineers, nottingham. the process of carbonising is patented by the universal charcoal company, limited, who are to receive a royalty, we understand, from the health committee for the use of their patent. there is a tall and noble-looking chimney in the centre of the yard surrounded by many new buildings and sheds, and this has been built with the concrete mortar manufactured by the health committee. such is the gigantic scale upon which these matters are dealt with in the city of manchester. the other methods, to which reference has been made, for the disposal of town refuse require no further comment, as it is evident that unless a ready sale for the refuse can be effected, by far the best method of disposing of it seems to be that by which it is completely annihilated by fire in the manner that has been described, or in some other similar manner. having thus far followed the house refuse from its first appearance in its cradle, the dustbin, through its chequered career after collection down to its decease, either by burial, or by cremation, the question of the cost of the whole of this work must be deferred until the final chapter, after i have dealt with the subject of street sweeping and cleansing, the removal of snow, and a short chapter upon street watering, which is somewhat analagous to scavenging, and is frequently included in the accounts of that work in the estimates which are prepared by a local authority. chapter vii. "street cleansing." clean well-swept streets not only add materially to the prosperous appearance of a town, but they also have a very marked influence upon its health and upon the morale of its inhabitants; wet, and muddy, badly formed, ill-drained streets, cause dampness in the subsoil of the dwelling-houses in the vicinity, and a humidity in the atmosphere, both of which tend to produce a low standard of health in their neighbourhood, irrespective of the wet surface through which pedestrians have to wade whenever they are obliged to cross such streets. dusty streets, too, are very injurious from the fact of persons inhaling the gritty silicate loaded air arising from them; such an atmosphere is known to produce disease of the lungs, even when it is free from the dust arising from horse droppings or other organic impurities. professor tyndall, in his beautiful experiments, has proved that dusty air is alive with the germs of the bacteria of putrefaction, whilst the pure fresh air which he gathered on a mountain peak in the alps is innocent of such germs, and is absolutely powerless to produce any organisms. persons living in streets that are improperly swept or watered are unable to open the doors or windows of their houses with impunity by reason of the dust. the definition of the word _street_, as given in the public health act, 1875, is as follows:--"street includes any highway (not being a turnpike road), and any public bridge (not being a county bridge), and any road, lane, footway, square, court, alley, or passage, whether a thoroughfare or not." with reference to turnpike roads the act further states that any urban authority may by agreement with the trustees of any turnpike road, or with the surveyor of any county bridge, take on themselves the maintenance, repair, cleansing, or watering of such street or road. it is very questionable, however, whether the onus of cleansing private courts and alleys which are not repairable by the urban authority should be borne by them, although for the sake of the public health it is highly desirable that such work should be so undertaken. the great difficulty attached to this duty arises from the fact that as a rule these private courts and alleys are very badly paved, if paved at all, full of pits, where pools of stagnant mud and water collect, and even in the best cases, the interstices between the pebbles, or other paving, are filled with filth arising in great measure from the dirty habits of the people, and this filth it is found exceedingly difficult to dislodge. the remedy for this is to compel the owners of the abutting properties to have the courts and alleys properly paved with asphalte, or other equally impervious material, after which it would be easy for the urban authority to cause them to be swept at least once a day, and flushed with water in the hot weather once a week, but in order to compel the owners to execute this very desirable work it would be necessary to put the complicated machinery of section 150 of the public health act, 1875, in force, and the expense to the landlords would be in many cases very disproportionate to the value of their property. out of the ninety towns to which reference has before been made, the authorities of only nineteen of them cleanse the private courts and alleys in their jurisdiction. the sweeping and cleansing of streets should be effected either at night or very early in the morning; if, however, the bad practice of bringing the house refuse out into the streets in inappropriate receptacles is in vogue, it becomes necessary to sweep the street later in the day, after the contents of these receptacles has been removed. in most cases it is necessary to cleanse the principal streets of a town at least once a day, and this appears to be the practice of nearly all the ninety towns referred to, but only seven of them appear to have this operation repeated more frequently; in several cases, however, the horse droppings, &c., are removed at once, under what is called the "orderly" system, and this is especially necessary in streets that are paved with such materials as wood paving, asphalte, or granite setts. the suburban streets of a town need only be cleansed once or twice a week, except in special cases of extremes of mud or snow. it is important, however, that the gully pits in all parts of the town should be cleared out constantly, and men should be employed for this purpose, as well as to cleanse and disinfect all the cabstands and public urinals at least once every day. street cleansing is effected either by hand-sweeping and hand-scraping, or by machinery. as to which is the most economical much depends upon the value of labour, and also upon the condition of the roads to be dealt with, but in point of time and as a general rule the value of a horse rotary brush-sweeping machine is undoubted, the only time at which such a machine fails to do effective work is on the occasions when the mud to be removed (owing to a peculiar condition of the atmosphere), has attained a semi-solidity, and is of a stiff and sticky consistency, when it either adheres to and clogs the brushes of the machine, or is flattened by them on to the road instead of being removed. the simplest and best of these machines, in my opinion, is that manufactured by messrs. smith & sons, of barnard castle. it sweeps a clear width of six feet, the rotary brush, which is divided into four or more parts, works diagonally, it is drawn easily by one horse, clearing itself of mud or dust in its progress, and the makers say that it can sweep 15,000 square yards of road surface in one hour, this being equivalent to the ordinary work of about 50 men in the same time! the price of this machine is £30, and being of very simple construction it costs little or nothing in repairs, except for the brushes, which last for about 180 hours when in constant work. these can, however, be replaced at a cost of £2 15s. per set, or the old stocks can be refilled with bass, at a more moderate figure. it is, of course, necessary to sweep the ridge of dust or mud which is left by the machine at the side of the street into heaps by hand labour, and to remove it by carts; other machines have been invented for cleansing streets, which by means of elevators, or other gear, profess to raise the mud or dust direct into the carts, which are to be attached at the back of the machine, but hitherto these machines have been found to be too cumbersome, costly, and complicated for the purpose, and they have not consequently found much favour with sanitary authorities. messrs. smith & sons also construct a patent road scraping machine, which is drawn by one horse, and which will, they say, scrape upwards of 10,000 square yards of road surface in an hour. the strength and durability of the hand brooms purchased by an urban authority for the work of sweeping the streets is of some importance, as affecting the ultimate cost of the work, and some care and skill is required in their selection. bass brooms are better than birch brooms for this purpose, and the bass of which the brooms are made should be sufficiently stout and of regular thickness; it should be tough and elastic, not old, dry, and brittle, each knot should be of uniform size and be firmly set, and the number of knots in each broom head is also a matter of choice. a convenient and fair test of the soundness of a broom is to soak it for a few days in water before issuing it to the sweeper, and then note the time it will last. the handles of the brooms should be made of alder wood. the mode of construction of streets, and the materials of which they are formed, makes a considerable difference in the amount of cleansing necessary, and upon the quantity of mud or dust that has to be removed from their surface. in making any investigations for the purpose of deciding what difference exists in the question of cleansing various forms and descriptions of pavements, climatic influence introduces a rather disturbing element, which may seriously affect any conclusions that may be drawn; it may, however, be taken for granted that a street, the surface of which is metalled on the macadam principle with stones of a soft or gritty character, will require more cleansing and be more costly to scavenge (under the same conditions of climate and traffic), than a street paved with the hardest granite setts or with blocks of wood, or with asphalte, and at the same time much care will have to be taken not to _over_ sweep or _over_ scrape a road with a macadamised surface, or much injury will be done to it. amongst the influences that disturb the results of any investigations made with respect to street cleansing, that of the amount and character of the traffic over it must not be lost sight of, and the state of repair and gradient of the street are both of considerable importance in affecting the results, the practice too, of bringing out the house refuse into the streets in improper receptacles pending the arrival of the scavengers' cart, must also cause a varying amount of refuse to be swept from its surface, depending upon the habits of the persons living in the street. the superintendent of the scavenging department at liverpool has made some observations and obtained some valuable information on these points, which he has detailed in a report he presented to the health committee of that borough in the year 1877, an abstract of which is as follows:-gross cost for each time of cleansing 10,000 yards superficial of different descriptions of roadway in the borough of liverpool. [part 1 of 2] +----------------+-------------------+-----------------+---------+ | | | | | | | | |condition| | | | |of repair| | street. | description of | when paved. | of | | | pavement. | |roadway. | | | | | | +----------------+-------------------+-----------------+---------+ | | | | | |lord st. |{ granite setts, }| 1877 |very good| | |{ asphalte joints }| | | | | | | | |north john st. | ditto | 1872 | good | | | | | | |tithebarn st. |{ granite setts, }| 1872 and 1874 | bad | | |{ ordinary joints }| | | | | | | | |west derby rd. |{ ditto, asphalte }| 1876 |very good| | |{ joints }| | | | | | | | |great howard st.| ditto | 1877 | good | | | | | | |great homer st. |{ ditto, ordinary }|not ascertainable|moderate | | |{ joints }| | | | | | | | |kensington st. |{ macadam breasted}| ditto | good | | |{ with setts }| | | | | | | | |stanley rd. | ditto | ditto | bad | +----------------+-------------------+-----------------+---------+ [part 2 of 2] +----------------+--------------+-------+--------+--------------+ | | | | | gross cost | | | area | loads | times | per 10,000 | | | of |removed| swept | yards | | street. | carriage |in one | in one | superficial | | | way. | month.| month. | for each | | | | | | cleansing. | +----------------+--------------+-------+--------+--------------+ | | yds. supr. | | | £ s. d. | |lord st. | 4,503 | 15 | 26 | 0 6 5½ | | | | | | | | | | | | | |north john st. | 3,287 | 17½ | 26 | 0 8 10½ | | | | | | | |tithebarn st. | 5,150 | 38 | 26 | 0 11 2 | | | | | | | | | | | | | |west derby rd. | 11,980 | 35 | 13 | 0 9 4¾ | | | | | | | | | | | | | |great howard st.| 16,860 | 85 | 13 | 0 14 4½ | | | | | | | |great homer st. | 15,900 | 85 | 13 | 0 14 1 | | | | | | | | | | | | | |kensington st. | 14,540 | 76 | 13 | 0 14 3¾ | | | | | | | | | | | | | |stanley rd. | 16,534 | 186 | 13 | 1 8 9¼ | +----------------+--------------+-------+--------+--------------+ he adds that the full benefit of the impervious pavements as regards the cost of scavenging has not yet been felt, for almost all the lines of streets so paved are intersected at short distances by streets of ordinary jointed granite setts or macadam, whence a quantity of mud and refuse is dragged by the traffic on to the asphalted jointed roadways, which are consequently debited with the cost of removal of some effete material not intrinsically belonging to them. he further adds that the credit reductions to be made in respect of the value of manure obtained from each description of carriageway is not readily ascertainable. in dry weather the value of manure collected from granite setts, with or without impervious joints, is about equal, but when the sweepings are wet, and consequently of little value for sale, the quantity yielded by the ordinary pervious jointed pavement is greater than from the impervious, and therefore the total value is relatively favourable to the latter class, whilst to get rid of the sweepings from macadamised streets is a source of additional expense. he concludes this portion of his valuable report by observing that the advantages of the new impervious pavements over the old kinds are especially shown after frost and snowfall, the results of which cause the setts of ordinarily jointed roadways to become loose, and allow a vast amount of mud to ooze up between the softened joints. the comparison is still more apparent in regard to macadam, which, unless a heavy rainfall succeeds the thaw, cannot be swept for some days without great destruction being caused to the metalling of the roadway. the ultimate disposal of the material removed from the surface of a macadamised roadway, being principally composed of silicate, and consequently valueless as a manure, is a difficult matter. in small towns, except during abnormally muddy weather, it may be mixed with the house refuse and sold to farmers, or the road scrapings themselves may be used as an excellent sand, if thoroughly washed, to mix with lime or cement to form mortar for public works; excessive accumulations of mud, however, must be got rid of in the most economical and speedy manner, and this is effected either by filling up old disused quarries with it, or depositing it upon waste lands, or forming embankments for new roads, but in no case should it be used, as i have before stated, upon building sites; it is difficult and expensive to destroy it or partially convert it into other matters by fire, so that if these methods which i have enumerated are impracticable, the only other method left for the disposal of the sweepings or scrapings from the streets is to take them out to sea in hopper barges and sink them in deep water. in the city of paris an area of about 13,000,000 square yards of streets are cleansed between three and six a.m. in the summer months and four and seven in the winter. this work in connection with the collection of the house refuse employs 2,200 men, 950 women, and 30 boys, besides 190 mechanical sweepers. the paris mud is said to no longer possess the manurial strength of former times, and in consequence the receipts derived by the municipality from this source have greatly diminished. at the present time it is disposed of by public tender to responsible contractors, who manage to take between them some 2,500 cubic yards daily. the following additional particulars of the manner in which this work is carried out in paris will, i think, prove of interest, especially with regard to the use of disinfectants, which are largely used in that city in connection with the cleansing of the streets, a practice which might be followed with advantage by the sanitary authorities of this country. the cleansing of the public thoroughfares in paris, which was formerly undertaken by the prefect of police, is now a function of the prefect of the seine. the staff consists of two chief engineers, one for each group of arrondissements, one group being sub-divided into three sections, each under the charge of an executive engineer, and the other into five sections similarly supervised. these sectional engineers have under them 51 superintendents and 61 overseers, whose employment costs annually £10,400. the scavenging plant is kept in a central depôt, where materials of every description are stored and classified for ordinary and extraordinary service, when snow and ice render additional assistants necessary. the depôts contain supplies of chloride of lime, sulphate of zinc, sulphate of iron, and carbolic acid, as disinfectants; and hydrochloric acid and nitrobenzide, as cleansing agents. the chloride of lime, of a strength of 100° to 105°, is successfully employed for the disinfecting of places tainted with urine or faecal matter, also for cleansing gutters carrying any sewage water. sulphate of iron and sulphate of zinc are both used under the same conditions. sulphate of iron has the disadvantage of rusting objects to which it is applied, sulphate of zinc is stronger in its action, but it costs a little more; it produces no smell, nor does it leave any stain; it is much employed in summer for washing and watering the basements of the "halles centrales," which are used for fish, poultry, and offal. at a strength of one-eighth, and mixed with three per cent. of sulphate of copper, sulphate of zinc makes a good disinfecting liquor, which preserves its qualities a long time, and is of great use in private houses. carbolic acid is not, strictly speaking, a disinfectant; it does not act like chloride on putrid matter, but it arrests and prevents fermentation, doubtless by destroying the spores, it is, therefore, always employed when it is desired to destroy the germs of putrid fermentation. it is used at a strength of about one-fortieth, say a gallon of acid to 40 gallons of water. at strengths of one-one hundredth and one-two hundredth it gives good results for watering once or twice a week in summer those parts of the "halles centrales" liable to infection; it is even used as low as one-one thousandth for watering streets and gutters. hydrochloric acid is applied to urinals and slaughter-houses, in places much encrusted with tartar; it is used at a strength of one-sixth, lowered to one-tenth, it cleans smooth walls and flags efficiently, in ordinary rinsings a strength of one-fifteenth suffices; it leaves a disagreeable odour behind, which is, however, quickly dissipated. nitrobenzide is more energetic than the foregoing, but it produces a disagreeable smell of bitter almonds and leaves a white film, which has to be washed off; it is used at the same strengths as hydrochloric acid. the annual cost for plant and disinfecting materials of all descriptions is £8,800. chapter viii. "snow." the unthinking ratepayer frequently exclaims, "why cannot the authorities order this abominable snow to be immediately carted away?" when the footpath and roadway in front of his domicile lie hidden under a thick coating of snow crystals. signor e. bignami sormani, assisted by professor clericetti, have made several most interesting investigations and observations upon the density of fresh fallen snow in milan by means of a simple balance and compressing box. the range of weight of the snow was found to vary as much as eleven times the minimum. a cubic yard from one snowstorm, weighing as much as 814 pounds, while an equal bulk from another fall only weighed 71 pounds. the weight consequently of a cubic foot of the densest snow is 30.14 pounds, whilst a cubic foot of water weighs 62.5 pounds, or only about double the weight of this dense snow, but which was in all probability little different from ice. for my purposes, however, i will take a mean between these extreme weights, and assume that the weight of a cubic foot of snow is 16.38 pounds, and that a fall of three inches of snow during the night has caused the ejaculation with which i commenced this chapter to proceed from the aforesaid ratepayer. the ordinary width of an english street may be taken at thirty-six feet, including the footpaths, so that on every one hundred yards in length of every street of that width 2,700 cubic feet of snow have fallen, the total weight of which amounts to 44,226 pounds, or very nearly 20 tons, which in actual bulk would represent 100 cubic yards. but as the snow would soon become compressed after falling, i assume that this bulk would be diminished by one-half, and that consequently (without reckoning the snow which has fallen upon roofs and into courts, passages, and alleys, and which has been quickly shovelled therefrom to the street by the occupiers) about 40 ordinary cartloads, weighing half a ton each, would have to be removed from this length of street. assuming that there are 30 miles of street in a town from which the snow must be _immediately_ removed, 21,144 loads must be carted somewhere, at a cost of at least £1,500, assuming that each cart could make ten trips a day, and even then it would take 352 carts a whole week to effect it. it may be contended that i have taken an extreme case, and that, of course, the snow does not lie for very long upon the ground in the condition in which it fell, and that hourly it is reducing in bulk and weight by being ground up by the traffic, and finding its way in the form of water into the sewers, but i have simply advanced the few facts which i have stated in order to give some idea of the labour and cost of snow clearing in a city or town, and i think i cannot do better than at once describe how this important work is carried out in the city of milan, where the organization and arrangements by which it is accomplished with marvellous despatch, and efficiency, could with advantage be copied by the authorities of any of our towns which are occasionally visited by excessive falls of snow. in milan the snow carts are emptied into the navigable canals and numerous watercourses by which the city is intersected; and latterly also into the new sewers in the central portion of the city, which are promptly flushed whenever it snows. during the winter of 1879-80 the cost of clearing the 1,656,200 square yards total area of squares, streets, and lanes within the city walls, averaged £200 per inch depth of snow fallen, and for the 502,800 square yards outside the walls the average cost was £62 per inch depth, equivalent in each case to about 1.05d. per cubic yard. ordinarily the clearing of the more frequented streets is completed within eight or ten hours after it has stopped snowing; and of the rest within 24 hours, not reckoning night. the city is parcelled out into small districts, numbering 112 for last winter, of varying extent according to the importance of the work in each. an average rate of pay per inch depth of snow fallen is settled for the whole area of each separate district, according to its extent and the particular conditions affecting the several streets and squares comprised within it. each district is allotted to a contractor, who usually associates with himself six to ten partners, besides the labourers whom he employs. he has to find carts, horses, and carters; the necessary implements--spades, shovels, brooms, scrapers, mattocks, barrows, &c.--are furnished by the city, under suitable stipulations for ensuring proper care in their use. the contracts are made annually, and the same persons almost always apply for them again year after year. the contractors come principally from the trades that are interrupted by winter, viz.:--paviors, bricklayers and masons, and gravel quarrymen. for the direction and supervision of the work the whole city is divided into four sections, over each of which is appointed an engineer, with an assistant, who are aided in the general arrangements by the police surveillance. payment is made only for work effectually done. in each snowstorm the depth of snow falling, which is the basis of pay, is ascertained by means of a number of stone posts, fixed in suitable open spaces, clear of shelter from buildings, and each capped with a flat horizontal slab of stone. as soon as it stops snowing, or two or three times during a storm of several hours, the depth of snow caught on the slabs is measured by the engineer in the presence of two of the contractors in his section. the number of men ordinarily engaged in snow clearing on a winter's day is not less than two thousand, and has sometimes risen to three thousand. the stock of implements found by the city, representing a capital of about £1,600, is housed in two stores in opposite quarters of the city. in the winter of 1874-75 the total fall of snow amounted to 40¾ inches, and the whole expenditure for clearing it within the city walls exceeded £8,400; while in 1877-78 the fall was only 5¼ inches, involving an expenditure of less than £1,040 for a slightly larger area. the small cost at which this work is carried out in milan is accounted for by the low rate of wages and cart hire, and the perfect organization of the system. when a fall of snow occurs in paris, attention is first directed to clearing the footpaths and crossings, so as to ensure uninterrupted foot passenger traffic. the town scavengers sand the roads whenever it is necessary for the carriage traffic, at the same time numerous auxiliaries are organised to remove the snow from the principal thoroughfares in the order of their relative importance. to assist in removing the snow the general omnibus company are bound by their concession to furnish 50 waggons, and carts are specially arranged for with the providers of sand and gravel at the beginning of winter, the contractors for maintaining the public roads being also bound to hold their carts at the disposition of the sectional engineers. in certain cases the half-melted snow is swept into the sewers, especially into those carrying warm water. melting by steam has been tried, when a continuous jet was turned on to a mass of banked snow, but it melted very slowly at first, and the melting ceased after the cavity had increased to a certain size. two descriptions of snow ploughs are kept in store, one for manual, the other for horse power, but they have never been used, as the coating of snow seldom attains sufficient thickness, and it is too quickly compressed and hardened by the traffic. as a rule, the sum allowed in the budget, about £7,000, suffices for the extra labour incurred, but occasionally severe winters cause this to be greatly exceeded, as in 1875-76, when the increase amounted to £8,000, and no doubt in the winter that has just passed, 1880-81, the estimate must also have been largely exceeded. in england one of the greatest difficulties we have to contend against is the disposal of the snow after it has been placed in the cart. if there is a river close by, it can be taken there and tipped, but this is objectionable if it is a navigable river where dredging has to be done, as it is surprising what a quantity of road scrapings and other matters are always removed with the snow, and these materials naturally sink to the bottom, and add considerably to the cost of dredging. if there are public parks the snow may be heaped in them, provided no damage is done to the grass or paths, as the snow thus heaped takes a considerable time to melt, the first effect of a thaw being to consolidate it, but a better plan is to deposit it upon any waste spots, if these are not too far from the streets which have to be cleared. tipping the snow down the manholes into the sewers has been tried in london and other cities, but has failed through the snow consolidating, and although lighted gas jets have been turned on to the snow, it has still melted too slowly to be of any practical utility. it has been suggested that a steam jet should be turned on the snow as it lies in the streets, or after it has been heaped, but i very much doubt the efficacy of this plan, although messrs. merryweather & co., of london, have, i understand, melted a cartload of snow in seven minutes. it might, however, be possible to melt the snow by the heat generated in the furnaces that are destroying the house refuse by fire, and this could be effected without any large expense beyond the cost of cartage of the snow to the depôts, which would, of course, be necessary. failing an organization such as that of milan, the following suggestions may be of use to those who have sometimes to grapple with this unproductive work:-do not attempt to cart away the snow while it is yet falling, but try to make clear crossings for the foot passengers and to keep the traffic open. if there should be a high wind at the time, and the snow drifts in consequence, cut through the drifts so as to allow the vehicular traffic to continue. directly the snow ceases to fall put on all available hands to clear the channel gutters and street gratings, in preparation for a sudden thaw, when, if these precautions were not taken, serious flooding and great damage to property might ensue; for the same reason cart away all the snow you can at the bottom of gradients and in the valleys, and also from very narrow streets and passages, &c. in the wider streets use the snow plough, or with gangs of men (in the snow season there is generally plenty of labour obtainable), shovel the snow into a long narrow heap on each side of the street, taking care to leave the channel gutters and gratings quite clear, and a sufficient space between the heaps for at least two lines of traffic. passages must also be cut at frequent intervals through the heaps, in order to allow foot passengers to cross the street, and also to let the water reach the channel gutters as soon as the snow begins to melt. with regard to the question of clearing the snow from the footpaths irrespective of the larger duty of clearing it from the streets, it is often a disputed point in a town as to whether this should be done by the urban authority at the expense of the rates, or by the householders themselves, and this can only be settled where the town has a private improvement act, in which a clause or clauses may be inserted throwing the onus of such cleansing and sweeping of the footpaths upon the several and respective occupiers of houses and buildings. but on whoever the duty rests there is no doubt that the easiest and quickest method of effecting a thorough cleansing of a footpath from snow is by an application of salt, and then to sweep off the slush that is engendered with a broom. medical men and others, however, assert that the practice of putting salt with the snow is to make a freezing mixture, which is detrimental to the health of persons walking on such a mixture, and there can be no doubt that excessive cold is caused by this practice, often sufficiently severe to crack the flagstones of the foot pavement. in the city of london the footways are swept once daily by men in the employment of the commissioners of sewers, and in wet weather those in the main streets are cleansed repeatedly during the day, and this has been done, i believe, since the year 1872, although the occupiers are legally liable for the execution of this work. in liverpool, also, this is done after a fall of snow, as will appear from the following interesting remarks on the subject, contained in a report by the superintendent of the scavenging department in that borough:-"the only way to compass the removal of snow from the footwalks of the principal thoroughfares within a comparatively short time is by sprinkling them with salt such as is commonly used for agricultural purposes. it is certain that, unaided by the salt, a sufficient number of men cannot be procured for the emergency of clearing snow from the footways of the most important thoroughfares. it has been stated by medical authorities that the application of salt to snow is detrimental to the health of people who have to walk through the 'slush' produced by the mixture, and that the excessive cooling of the air surrounding the places where the application has been made is injurious to delicate persons. it, therefore, seems that the application of salt to snow should not be undertaken during the day time, but should be commenced not before 11 p.m., nor continued after 6 a.m., and that only such an area of footwalks should be so treated on any one night as the available staff of men can clear by an early hour the following morning. "to sweep snow from the footwalks whilst the fall of snow continues, and especially during business hours, appears to be wasteful and futile, and to apply salt during the same periods may be held to be injurious to health. "that the snow of an ordinary fall can be removed from the footwalks by an application of salt an hour or so before they are scraped is an ascertained fact, except at least when a moderately severe frost has preceded, accompanied, or followed the snow fall, or when the snow has drifted into extensive accumulations. were it not for the danger to health by excessive cooling of the air, and for the expense attending the operation, all the impervious pavements could be cleared of snow (unless the fall was a heavy one) in a comparatively short time by a liberal application of salt and the employment of the horse sweeping machines as soon as the snow had become sufficiently softened to admit of their use." to these remarks i have nothing to add, except to suggest that in addition to clearing the snow from the footpaths care should also be taken to scrape out and thoroughly clear the roof water trunks, which are frequently found crossing the footpavements; if these remain choked damage may ensue to the adjoining property when a thaw commences. chapter ix. "street watering." the effective watering of streets and roads in any town during the summer months is an important matter, not only on sanitary grounds, but also from the fact that considerable damage may be caused in the neighbouring shops, warehouses, and dwellings, if something is not done to prevent the clouds of detritus and decaying refuse, of which the dust is composed, from being blown about. in the metropolis of london alone, the watering of the streets and roads employs, in addition to a staff of surveyors, inspectors, and foremen, about 1,500 men, and an equal number of horses and carts; and in order to lay the dust effectually, about 30,000 tons of water must be spread upon the streets every dry day, the cost of this gigantic work being nearly £200,000 per annum upon an average of 120 days, when watering becomes necessary. the most commonly known method in this country for watering the streets and roads of our towns is that of carrying the water in wheeled barrels, carts, or vans, and distributing it therefrom through a perforated pipe upon the surface of the road as the vehicle is drawn along by a horse attached to the shafts. the points of importance to be considered under this system are as follows:-(1.) the number and position of the stand posts or hydrants, from which the water carts are to be filled, and whether they shall be "swan neck" stand posts or "valve" hydrants. (2.) the size and form of the body of the water carts, as regards its cubical capacity, its weight, strength, lightness of draught, durability, width of spread, and shape of jet, so as to ensure evenness of supply without leaving pools of water or dry patches after it has passed, or causing that unpleasant cloud of dust which so often follows the cart. a wonderful improvement in all these respects has been lately effected by the introduction of mr. e. h. bayley's patent hydrostatic van, of which i shall speak more in detail hereafter. (3.) another point of some importance is the material of which the hose shall be constructed, if valve hydrants and not swan necks are existing. my opinion is that it should be of leather, as being roughly handled and little cared for; canvass hose, although the cheapest, is not sufficiently durable, and is consequently the dearest in the end; and (4), lastly, the driver and horse should both be of some intelligence. a check should also, if possible, be kept upon the former to see that he performs his allotted task, and does his proper number of rounds. mr. bayley has also introduced for this purpose a "tell tale indicator," which records automatically the quantity of water used; it cannot be tampered with, and registers on a dial outside the van each load of water delivered, so that the surveyor or other officer can see at a glance whether the driver is attending to his work, or whether the hot weather has made him find his throat drier than the roads, and he has been spending some of his time in moistening it. in the year 1856, mr. scott, c.e., the chief surveyor of the parish of st. pancras, kept an account of the daily round of an ordinary water cart, when he found that through an average working day of 10¼ hours, exclusive of the breakfast and dinner hours, the cart took one hour and twenty minutes filling, fifty minutes only in distributing the water on the roads, and eight hours and seven minutes in travelling to spread the water and back to the stand posts. it was obvious that these were placed too far apart, and by the subsequent introduction of additional standposts mr. scott found, in the year 1867, that the filling occupied two hours, the distribution one hour and thirty minutes, and the travelling to and fro six hours and thirty minutes, so that it may be assumed, with an ordinary two-wheeled water cart, that two-thirds of the day is spent in travelling, one-fifth in filling, and about one-seventh in the actual spreading. to many of my readers bayley's van is probably as familiar as it is to me, but it may notwithstanding be well to describe it. it is a handsome vehicle in appearance, the body being made of wrought iron plates, and measures 8 ft. in length by 4 ft. 8 in. in breadth, and 2 ft. in depth, holding 450 gallons. it is mounted on springs upon four wheels hung upon bayley's patent axles, and has a pair of light shafts; it can easily be fitted with a break for hilly roads, and there being no weight at any time upon the horse's back, he is relieved from any severe strains. by means of an adjustable valve the flow of water can be regulated according to the state of the roads, and, if necessary, a double valve can be inserted, so that either side of the distributor can be at work when only half the width is required, or when passing a carriage or narrow spaces. the branch pipe is of uniform size, except close to the spreader, where it enlarges in order to avoid friction, and this is assisted by the branch pipe being shaped into a cycloidal curve on each side. in order to obtain as great a pressure as possible upon the jets of the distributing pipe, and thus to give the side jets a greater trajectory than they otherwise would have, the tank is elevated as high as is consistent with the conditions of draught. at the same time, the distributing pipes are placed as near to the ground as convenient, so that the maximum extent of distribution is obtained, and that with less dust and splashing than in the ordinary system. the holes in the distributing pipe instead of being drilled in straight lines, are on a curved line, which rises along the length of the pipe from the centre towards the ends. this has been found necessary, in order that the distributing pipe may be placed low, and at the same time advantage be taken of the width of the trajectory of the jets. comparing the work of one of these vans with that reported upon by mr. scott, it is found that the van occupies nine minutes in filling, six minutes in spreading the water, and only three hours and fifteen minutes in travelling to and fro, so that in seven hours it accomplishes as much work as the ordinary water cart effects in ten hours. in edinburgh, where a trial of one of these vans took place against one of the old carts, it was found that the van spread the water a width of 20 feet, while the old cart only covered 14 feet; the van conveyed the water 1,731 feet, and the cart only 951 feet. the superficial area watered by one load of the van was 34,620 feet, and by the old system only 13,314 feet. when we consider the time that is lost in travelling to and from the stand pipe, what a large saving this represents in the cost of this work. mr. tomkins, c.e., the surveyor of the important metropolitan parish of st. george, hanover square, has made the following comparative experiments with one of bayley's vans as against an ordinary cart:- +-----------+--------+--------+---------+----------+-----------+------+ | |contents| no. of | total | | | gain | | | in |loads to|quantity | time. |difference.| per | | |gallons.| cover |of water.| | | cent.| | | | beat. | | | | | +-----------+--------+--------+---------+----------+-----------+------+ | | | | |hrs. mnts.| hrs. mnts.| | |van | 450 | 5½ | 2475 | 1 23 | - | - | |no. 4 cart | 225 | 11 | 2475 | 1 50 | 0 27 | 24½ | | | | | | | | | |van | 450 | 5½ | 2475 | 1 38 | - | - | |no. 9 cart | 237 | 11 | 2607 | 2 10 | 0 32 | 25 | | | | | | | | | |van | 450 | 6 | 2700 | 1 45 | - | - | |no. 15 cart| 290 | 11 | 3190 | 2 10 | 0 25 | 19¼ | | | | | | | | | |van | 450 | 8 | 3600 | 2 15 | - | - | |no. 19 cart| 260 | 17 | 4420 | 3 30 | 1 15 | 36 | +-----------+--------+--------+---------+----------+-----------+------+ this shows a mean gain of 26 per cent. in favour of the van, and the following tables made by an inspector in 1873, showing the actual occupation of the ordinary carts and bayley's vans during a day's work, are extremely interesting, as showing that while the van is engaged in spreading the water the time of the cart is wasted in travelling to and from the stand posts, and when it is borne in mind also that the van spreads water more widely than the cart, there can be no doubt that a saving of at least 30 per cent. can be effected by the substitution of these vans for the old-fashioned cart. carts. +--------------+--------+----------+----------+------------+----------+ | | |travelling|travelling| | | | |filling.| full. | empty. |waiting, &c.|spreading.| +--------------+--------+----------+----------+------------+----------+ | | h. m. | h. m. | h. m. | h. m. | h. m. | | paddington | 1 45 | 2 9 | 1 58 | 0 20 | 1 30 | | st. saviour's| 1 29 | 2 16 | 2 4 | 0 26 | 1 29 | | strand | 1 11 | 2 30 | 2 18 | 0 17 | 1 3 | | kensington | 4 40 | 2 2 | 1 57 | 0 0 | 1 54 | | chelsea | 2 44 | 1 15 | 2 14 | 0 35 | 1 6 | +--------------+--------+----------+----------+------------+----------+ vans. +--------------+--------+----------+----------+------------+----------+ | paddington | 3 33 | 1 9 | 1 3 | 0 0 | 3 0 | | st. saviour's| 2 20 | 1 4 | 1 21 | 0 23 | 2 58 | | strand | 2 30 | 1 25 | 1 14 | 0 20 | 2 23 | +--------------+--------+----------+----------+------------+----------+ one of the earliest methods for watering streets, but one which has, i think, almost entirely died out on account principally of the large quantity of water used in the process, was that of allowing the water to run down the channel gutters, ponding it back by means of canvass or leather aprons placed across the gutter, and then spreading the water on to the surface of the street by throwing it with wooden shovels. this method, although at first sight may appear clumsy, is an exceedingly good one upon sanitary grounds. it not only lays the dust, but it washes the surface of the streets, and it most effectually scours out the gutters and at the same time flushes the sewers, which at the season that watering is necessary is also of great importance to any town. by this process a delightful freshness is given to the air, and the appearance of the cool and limpid water rushing along on each side of the street acts favorably upon the inhabitants. the great objections to this system are the enormous quantity of water that is used in the process, and the difficulty of doing the work after the traffic of the day has commenced. somewhat of a modification of this process is what is known as "brown's system of street watering," which may be described as follows:--a lead pipe is laid in the footpath at the back of the kerb on each side of the street to be watered, small gratings or shields being fixed in the pipe at intervals of twelve inches, and the remaining space filled with asphalte; small holes are then bored in the pipe through the openings in the shields. the pipe is connected with the water main in the street, and is provided with the necessary stopcocks, &c. on the water being turned on, fine jets are thrown in different directions upon the surface of the street. the width of roadway that can be watered by this process depends upon the pressure of the water, but it may be fairly assumed that in most towns streets of fifty feet width could be effectually watered in a few minutes by a pipe on each side of the street. this process has not gained much favour hitherto, principally on account of the large first cost involved, which would amount to upwards of £800 per mile of street, but the expense afterwards should not much exceed the wages of one man at about 3s. 6d. per day to manipulate the necessary work, and the interest on the outlay and depreciation of the pipes, &c. the other objections to this system are:-(1.) the liability of the pipes and perforations to get out of order, especially when allowed to lie idle for so many months in each year. (2.) the unpleasantness to pedestrians which must be caused whilst the watering is proceeding. (3.) the inconvenience to the traffic during the process. (4.) the effect upon the water by high winds, when in all probability it would be blown back across the foot pavements. (5.) in very broad streets it would be inoperative. in paris and other continental cities, and also in several towns in this country, the watering is effected by hose and reels, or by portable iron tubes. mr. parry, c.e., the borough surveyor of reading, has given the following particulars of the system of hand watering adopted in that borough, in which he gives the cost, and describes the utility of that method as compared with the use of water carts:-a water cart (he states) will water twice a day a superficial area of 23,849 yards, and for a length watered one width that means 5,962 lineal yards, or for a double width 2,981 yards, the cost per day of laying on being as follows:--horse, cart, and man, 8s.; cost of maintenance of cart, harness, shoeing, &c., 1s. 5d., making 9s. 5d. per day. with respect to the hand machines he states that he has one of headley's drum machines, and three of special make, somewhat similar to those used in paris. they are equal in point of work; and one machine will water 23,740 square yards twice a day, which, it will be observed, is very close to the amount of work performed by a cart. "headley's machine cost us (he continues), five years ago when new, £31 7s. 3d., and the repairs and maintenance since that date have been £22, or an average of £4 8s. per annum, and is just now almost past repair. the other description of hand machine cost each when new £20, and the repairs and maintenance have amounted to an average of £3 18s. each year. they were in use sometime before headley's was obtained, and they will be of use for a long time yet. the cost of labour per day by the hand machines is for two men at 2s. 10d. each--5s. 8d.--as it requires two men to work the machine properly, one to distribute the water, and the other to move the machine and to attach and detach the apparatus to and from the hydrants; add to this 7d. per day for maintenance and repairs, will make 6s. 3d. per day. the quantity of water delivered by the water carts is 0.51 gallon per square yard, and by the hand machine 1.30 gallons." it will thus be seen that in the case of the cart 24,324 gallons of water are used per diem, and 61,724 gallons by the hand machines, the surface watered being very nearly the same in both cases. assuming that the water has a commercial value of 6d. per 1,000 gallons, and adding this to the cost per diem in each case, the total cost stands thus:- hand machines £1 10s. 10d. carts £1 1s. 7d. the advantage in point of cost being in favour of the carts, but the hand machine may water better, especially in broad streets, although in narrow streets or where there is much traffic, this method would be impracticable. in paris both hose and carts are used for watering the thoroughfares, the former for the boulevards, the avenues, and a certain number of first-class streets. the watering plant belongs to the municipality, and they have various forms of carts, containing 220, 242 and 286 gallons respectively, and will water from 2,400 to 3,350 square yards. the watering by hose is attended to by the ordinary street cleaners, who can easily water 24,000 square yards in about thirty-five minutes, deducting the time necessary to connect the apparatus with the mains, but this requires a gymnastic performance, which, if once seen, is not easily forgotten. watering the streets with sea water should be adopted whenever it is feasible, as it not only gives a delightful freshness to the air and dispels iodine, but it also causes the surface of the street to maintain its humidity for a longer period than when fresh water is used, as it impregnates the soil with hygrometric matter. this has been often attempted artificially, not only by adding common salt to the water used for watering, but also by adding chloride of calcium, notably in rouen, where this material is obtained from the manufactories of pyroligenous acid in the neighbourhood. it is stated that on a mile of road, 16 feet in width, 5,630 gallons of water were necessary daily, but that the same result was attained with 1,480 gallons of chloride solution, marking 30° beaumé, and costing about ½d. per gallon, the humectation remaining good for five or six days with the solution of chloride. with water only in 1,093 yards, in four rounds daily, 3,520 gallons were used, the cost being 48s.; with chloride of calcium the cost was 32s. per day. watering the roads with a largely diluted disinfectant, such as "sanitas" in the liquid form, is frequently of great benefit, and where it can be afforded, it should be occasionally done, especially in the narrower streets and more crowded districts of a city or town. chapter x. contracts _v._ administration by local authority. amongst the questions which i addressed to the surveyors of the principal towns of england was the following:--"is the house refuse collected by the sanitary authority or by a contractor?" and out of the ninety towns from which i received replies, only thirty were found to employ contractors for this purpose, and of these the authorities of two of them proposed to dispense with the services of the contractor, and to administrate the work with their own staff, as they found the existing state of things was thoroughly unsatisfactory. this is hardly to be wondered at when the nature of such contracts comes to be considered. the "dust" or "slopping" contractor, or whatever he may be designated, can hardly be expected to be a philanthropist, whose principal object in carrying out his contract is that of benefiting his fellow creatures and not himself; on the contrary, it may fairly be assumed that the contractor's object is to serve his own interests, and to make his contract pay. it is but natural, although the result may not be eminently satisfactory either to the ratepayers, who require a careful and systematic cleansing of their dustbins and streets, or to the sanitary authority and their officers who have to look after him. the officers, if they do their strict duty, will probably be engaged in constant disputes and litigation with the contractor as to the due and proper observance of the terms of his contract, and the consequence of their time being thus occupied instead of in other more important matters, is naturally detrimental to the interests of the ratepayers. if we turn to the articles of agreement or contract usually drawn up between a sanitary authority and a contractor for scavenging, we find that they are generally very binding in their phraseology, and enter fully into the details of the work; they should state very clearly the number of times in every week that the contractor shall cause all the ashpits in the districts enumerated to be emptied and cleansed, the manner in which this work shall be performed, and how the materials thus removed shall be disposed of and the place of their ultimate destination. the conditions should further specify what amount of manual, team labour, and carts, are necessary for the work, and also what plant the contractor must keep in the way of ladders, baskets, shovels, and brooms, &c. the conditions should also contain a carefully prepared list of the streets to be swept, and the manner and number of times this work must be executed, and arrange for the disposal of the materials thus removed. in many such contracts it is found necessary to insert clauses binding the contractor under all sorts of fearful penalties, to be always at the disposal and under the commands of the inspector of nuisances, or such other officer or officers as the sanitary authority may appoint. the contractor's men also are forbidden to refuse gratuities (an order which they no doubt fully carry out?) and are directed on no account to remove either trade or garden refuse, and they are also enjoined to be "careful to consult the convenience of the householders in their visits, and to thoroughly clean up all dirt and litter that they may cause in the discharge of their duties." if they fail in any or either of these injunctions and commands, or for any other dereliction of duty, the inspector of nuisances, or such other officer as the sanitary authority shall appoint, may summarily dismiss them, without any reference being made on the subject to their employer the contractor, and in fact the conditions have necessarily to be made so stringent and binding as to be either totally inoperative or open to grave abuses, or, on the other hand, the work can be carelessly and improperly executed by the contractor. i am, therefore, strongly of opinion that the work of the collection of house refuse and cleansing the streets should be carried out by the local authority with their own officers and staff, and that executing this work by contract is a mistake and a false economy. it is, perhaps, true that it may be done in the latter manner at less actual cost to the ratepayers, but all public work should be done in the best manner possible, irrespective of cost, thoroughly, but without extravagance, and the result of such work, especially where it affects the cleanliness and the appearance of a town, soon fully repays any moderate extra cost that may thus have been incurred, irrespective of the enormous benefit that is conferred upon any community by the reduction of disease and the death-rate by a proper attention to such necessary sanitary work. chapter xi. "_£ s. d._" a question of the greatest importance to the ratepayers, and one in which they often take the most lively interest, is that of the cost of maintaining the necessary staff for the purpose of carrying out the scavenging of the town, or for paying the contracts for a similar work. it is, of course, not possible to lay down any hard and fast line as to the cost of scavenging in any city or town, as it must necessarily vary considerably according to circumstances; much depends upon whether the district to be scavenged is an urban one, consisting of houses closely packed together, or whether it is suburban, with scattered villas and mansions standing in their own grounds; the question, also, of the distance of the depôts to which the material has to be carted, considerably affects the result of any estimate, as also does the cost of horse hire, the rate of wages, and whether the district is of a hilly or flat nature, and, as i have before shown, the manner in which the streets are formed and paved, the habits of the people, and last, but not least, the manner of the eventual disposal of the rubbish after removal; all these points must bear with great weight upon any question of cost, and make the results widely different. on referring to the returns to which i have more than once alluded, it is found that the cost of removing the house refuse and cleansing and sweeping the streets combined, varies considerably in different localities, in one case the sum amounts only to the rate of one half-penny per annum per head of the population of the town, whereas in another case the amount is at the rate of three shillings and sixpence per head. on calculating the average cost per head of population per annum of the ninety towns from which i received replies on this point, i find that it amounts to about tenpence half-penny, after giving credit for any sum of money realised by the sale of the refuse to farmers and others; so that if this work is costing the ratepayers of a town or city anything under a shilling per head of the whole population every year they have no cause to grumble, as they are so frequently found to do that their rates are higher, and what they have to show for them less than any other town in england. i have discussed the question of "contracts" or "administration" in a former chapter, but there is still another question which is also closely connected and intermingled with the question of cost, and that is when the sanitary authority carry out the collection and removal of the house refuse and cleanse the streets with their own staff, whether it is better and more economical for them to keep their own stud of horses or to hire them. to do thorough justice to the work i am of opinion that both the horses and carts should be the property of the sanitary authority for the following reasons:-(1.) the horses and their drivers should be under the control of the town surveyor or superintendent, in the same manner as the scavengers who accompany the cart. this is not the case if the horses are hired. (2.) the carts can be started on their rounds and leave work at such time as may be found most convenient, and all the horses being kept in one stable greatly facilitates this arrangement. (3.) the horses hired for this kind of service are frequently quite unfit to draw the bulky loads in the lofty carts behind them, and opprobrium is thrown upon the sanitary authority and the officials in consequence. (4.) economy in working is secured, for not only will good horses properly kept do a much better day's work than bad ones ill kept, but there is no one making a profit out of them as is the case when the horses are hired. with regard to the question as to the comparative cost of scavenging where a stud of horses is kept and where they are hired, the figures that i am about to give can only be speculative, as the conditions of each town are so widely different, but the figures may serve as a guide for forming an estimate of the kind, and they may be altered to suit the requirements of any city or town. i will, therefore, assume that a town with a population of about 35,000 inhabitants will require at least seven scavengers' carts constantly at work, without reckoning those which will be required after a fall of snow or in exceptionally muddy weather, and for which purposes auxiliary horses and carts must be hired, as also those which are engaged in hauling stones and other materials used for roads or public works. i have already stated that the value of an ordinary dust cart is about £18, so i will retain that figure for my estimate. the value of a new set of cart harness, including a loin cloth, should not exceed £7. to work seven carts properly, eight horses will be required, which may be estimated to cost about £50 each. the first cost of the necessary stabling for eight horses, including purchase of land, erection of buildings with a foreman's house, corn and hay lofts and machinery and tools, may be reckoned at about £1,500. with regard to the wages to be paid to the scavengers and the carters, it may be reasonably assumed that their rate of wages may be much lower than that paid to navvies, or what are known as "pick and shovel" men, for the following reasons:-in all house refuse there is always present a quantity of such materials as rags, bones, pieces of iron, and other articles, which have a commercial value, and behind each scavenger's cart hangs a sack, into which all such articles are placed by the men engaged in the removal of the house refuse, and are subsequently sold, and the spoil divided between them as perquisites. i have been credibly informed that in some localities the amount thus realised averages more than four shillings a week throughout the year. it is also a notable fact that although the householders are most particularly requested not to give gratuities to the men employed by the sanitary authority in this work, yet a considerable number of them constantly give the men a gratuity or bribe to ensure the dustbin being regularly and properly cleared, although the less generous, or poorer members of the community probably suffer in consequence; again at christmas the scavenger feels himself entitled to demand and receive a handsome present in the form of a christmas-box, which, in a rich neighbourhood, amounts in the aggregate to no inconsiderable sum. for these reasons i put the wages both of the scavenger and the carter at 16s. each per week, and adding a guinea a week for the foreman, who has in addition to this a house to live in rent free, and a stableman at 18s. a week, the total expenses are accounted for except those of the keep of the horses, shoeing, veterinary attendance, lighting the stable, &c. this also is a sum very difficult to estimate, as fodder, bedding, &c., varies so widely in different districts, but for the purposes of this calculation it may be estimated that 17s. per horse per week should be sufficient to cover all expenses under these heads. for the purposes of this calculation it will be necessary to assume that the £1,500 has been borrowed at 4½ per cent. in perpetuity, although as a matter of fact any monies borrowed for such a purpose as this would probably carry a sinking fund, so as to liberate the debt at the end of thirty or perhaps fifty years, but if i were to reckon the interest in this way in my estimate, it would complicate it unnecessarily. i have assumed that to meet the depreciation of horse flesh it will be necessary to put aside the value of one horse each year, without reckoning anything per contra for the sale of those worn out or injured in the work, as i think this will be found to be what would be necessary. i have allowed £50 per annum for repairs and depreciation of the buildings and machinery, as i consider this should be quite sufficient for a well-managed and cared-for property. i have allowed 15 per cent. per annum for repairs and depreciation of the harness, and 12 per cent. for the carts. the estimate will consequently stand thus:- specimen estimate of the cost per annum involved by any urban sanitary authority of a town of 35,000 inhabitants, in executing the work of collection of house refuse and the cleansing of streets, with their own staff of men and horses and carts. annual cost. £ s. d. capital borrowed £1,500, yearly interest at 4½ per cent 67 10 0 do. do. for 8 horses at £50 £400 do. do. for 7 carts at £18 £126 do. do. for 7 sets of harness at £7 £49 --- £575 at 4½ per cent. 25 17 6 repairs to buildings, machinery, &c. 50 0 0 depreciation of horse flesh, say 50 0 0 do. of 7 carts, costing £126, at 12 per cent. 15 2 2 do. of 7 sets of harness, costing £49, at 15 per cent. 7 7 0 wages of 7 carters at 16s. each per week 291 4 0 do. of 7 scavengers at do. do. 291 4 0 do. of 7 sweepers of roads at do. do. 291 4 0 do. of 1 foreman at 21s. per week 54 12 0 do. of 1 stablekeeper at 18s. do. 46 16 0 keep, &c., of 8 horses at 17s. per week each 353 12 0 ------------- total estimated cost £1,544 8 11 ============== if the foregoing estimate is compared with the standard of one shilling per head of the population per annum, which i have fixed as a fair average cost of such work, it is found to be less by £205 than that of a town of 35,000 inhabitants, for this latter case amounts to £1,750, and nothing has been allowed for the possible sale of the house refuse thus collected, but, on the other hand, i have allowed nothing for any emergency, such as a very rainy season or a deep fall of snow. if the horses and drivers had been hired the estimate might stand thus:- annual cost. £ s. d. hire of 7 horses and drivers at 8s. per diem for six days a week 873 12 0 hire of 4 horses and drivers on sunday, half-a-day each 41 12 0 foreman to superintend (no free house rent as in former case) 65 0 0 wages of scavengers as before 291 4 0 do. of sweepers do. 291 4 0 ------------- £1,562 12 0 ============== this shows that the cost of hiring would be slightly in excess of that of keeping a stud of horses, and when we consider the unquestionable benefit to be derived by adopting this method, i think most urban authorities who are now hiring their team labour would do well to consider the question of purchasing and keeping their own stud. great care, however, would have to be exercised in the supervision, or the expenditure would speedily increase, as in all stable establishments without such supervision, grave abuses, and even fraud, may go undetected for a considerable period. the figures that i have given in my estimates must not be criticised, for they are not intended to fix the value of such work, but simply to act as a guide to anyone interested in making an estimate of the kind, in which case prices more in accordance with the district could be inserted. the following table, however, gives the actual cost of collecting house refuse and cleansing and watering streets in fourteen large english towns:- +-------------+----------------------+----------------------------+ | | annual cost of col | this amounts to the | | | lecting house refuse | following:- | |name of town.| and cleansing and +--------------+-------------+ | | watering streets and | per 1,000 of | per mile of | | | courts. | population. | streets. | +-------------+----------------------+--------------+-------------+ | | £ | £ | £ | | bedford | 900 | 45.0 | 45.9 | | bristol | 13,005 | 63.1 | 108.3 | | cambridge | 2,350 | 67.1 | 83.9 | | cardiff | 5,545 | 65.2 | 95.6 | | carlisle | 2,261 | 64.6 | 113.0 | | exeter | 2,100 | 52.5 | 60.0 | | gloucester | 1,478 | 36.9 | 49.3 | | liverpool | 82,284 | 151.2 | 316.2 | | northampton | 2,820 | 51.3 | 104.4 | | oxford | 2,750 | 63.9 | 85.9 | | portsmouth | 5,276 | 39.0 | 101.4 | | southampton | 1,999 | 33.3 | 45.4 | | southport | 4,077 | 119.9 | 97.0 | | swansea | 4,200 | 60.0 | 76.3 | +-------------+----------------------+--------------+-------------+ _these figures are taken from a return prepared by mr. williams, c.e., engineer to the borough of cardiff._ i have frequently referred to some returns which i have obtained on the subject of the collection of house refuse and cleansing of streets, and it may be interesting and of use to others who wish to obtain information on these subjects if before closing this book i give a list of the questions that were asked. they were as follows:- (1.) name of city or town. (2.) number of inhabitants. (3.) area of district scavenged. (4.) is the house refuse collected by the urban authority. (5.) or by a contractor. (6.) how often is the house refuse removed. (7.) do the scavengers make a house to house call. (8.) or do they give notice of their approach by ringing a bell or otherwise, and require the householder to bring out the refuse to the cart. (9.) do the scavengers remove garden or trade refuse, and, if so, under what conditions. (10.) are the house dustbins, as a rule, fixed or movable. (11.) have you any public dustbins, and, if so, are they merely isolated instances, or have you a regular system. (12.) number of depôts for the refuse collected, and the distance they are from the town. (13.) how is the refuse disposed of. (14.) approximate mileage of streets cleansed. (15.) are all the streets swept daily, or only the principal ones. (16.) have you any provision for sweeping streets oftener than once a day, or for the frequent removal of horse dung, &c. (17.) are private courts and alleys swept and cleansed by the urban authority, and, if so, how frequently. (18.) what number of men, horses, and carts respectively, do you employ. (19.) net cost of your system after giving credit for any money realised by sale of refuse. in concluding this little book on "dirty dustbins and sloppy streets," i hope that what has been said may be of some use to my readers, and that they will themselves supply any omissions that they have found, and kindly correct all the errors, which are only too ready to creep into a work of this description. finis. transcriber's note obvious typographical errors and punctuation errors have been corrected after careful comparison with other occurrences within the text and consultation of external sources. the table on page 54 entitled 'gross cost for ...' was large in width, and has been split into two parts. the first column (street.) is repeated in the second part. except for those changes noted below, all misspellings in the text, and inconsistent or archaic usage, have been retained. for example, brick makers, brick-makers; pervious; potatoe; unhung; rinsings. pg 7, 'ash pit attached' replaced by 'ashpit attached'. pg 11, 'distance of ' replaced by 'distance of __. pg 30, 'a specialite' replaced by 'a speciality'. pg 56, 'of sillicate' replaced by 'of silicate'. pg 66, 'clearing the foothpaths' replaced by 'clearing the footpaths'. the sewerage of sea coast towns by henry c. adams contents chapter i. the formation of tides and currents ii. observations of the rise and fall of tides iii. current observations iv. selection of site for outfall sewer. v. volume of sewage vi. gauging flow in sewers vii. rainfall viii. storm water in sewers ix. wind and windmills x. the design of sea outfalls xi action of sea water on cement xii. diving xiii. the discharge of sea outfall sewers xiv. trigonometrical surveying xv. hydrographical surveying preface. these notes are internal primarily for those engineers who, having a general knowledge of sewerage, are called upon to prepare a scheme for a sea coast town, or are desirous of being able to meet such a call when made. although many details of the subject have been dealt with separately in other volumes, the writer has a very vivid recollection of the difficulties he experienced in collecting the knowledge he required when he was first called on to prepare such a scheme, particularly with regard to taking and recording current and tidal observations, and it is in the hope that it might be helpful to others in a similar difficulty to have all the information then obtained, and that subsequently gained on other schemes, brought together within a small compass that this book has written. 60, queen victoria st, london, e.c. chapter i. the formation of tides and currents. it has often been stated that no two well-designed sewerage schemes are alike, and although this truism is usually applied to inland towns, it applies with far greater force to schemes for coastal towns and towns situated on the banks of our large rivers where the sewage is discharged into tidal waters. the essence of good designing is that every detail shall be carefully thought out with a view to meeting the special conditions of the case to the best advantage, and at the least possible expense, so that the maximum efficiency is combined with the minimum cost. it will therefore be desirable to consider the main conditions governing the design of schemes for sea-coast towns before describing a few typical cases of sea outfalls. starting with the postulate that it is essential for the sewage to be effectually and permanently disposed of when it is discharged into tidal waters, we find that this result is largely dependent on the nature of the currents, which in their turn depend upon the rise and fall of the tide, caused chiefly by the attraction of the moon, but also to a less extent by the attraction of the sun. the subject of sewage disposal in tidal waters, therefore, divides itself naturally into two parts: first, the consideration of the tides and currents; and, secondly, the design of the works. the tidal attraction is primarily due to the natural effect of gravity, whereby the attraction between two bodies is in direct proportion to the product of their respective masses and in inverse proportion to the square of their distance apart; but as the tide-producing effect of the sun and moon is a differential attraction, and not a direct one, their relative effect is inversely as the cube of their distances. the mass of the sun is about 324,000 times as great as that of the earth, and it is about 93 millions of miles away, while the mass of the moon is about 1-80th of that of the earth, but it averages only 240,000 miles away, varying between 220,000 miles when it is said to be in perigee, and 260,000 when in apogee. the resultant effect of each of these bodies is a strong "pull" of the earth towards them, that of the moon being in excess of that of the sun as 1 is to 0.445, because, although its mass is much less than that of the sun, it is considerably nearer to the earth. about one-third of the surface of the globe is occupied by land, and the remaining two-thirds by water. the latter, being a mobile substance, is affected by this pull, which results in a banking up of the water in the form of the crest of a tidal wave. it has been asserted in recent years that this tidal action also takes place in a similar manner in the crust of the earth, though in a lesser degree, resulting in a heaving up and down amounting to one foot; but we are only concerned with the action of the sea at present. now, although this pull is felt in all seas, it is only in the southern ocean that a sufficient expanse of water exists for the tidal action to be fully developed. this ocean has an average width of 1,500 miles, and completely encircles the earth on a circumferential line 13,500 miles long; in it the attraction of the sun and moon raises the water nearest to the centre of attraction into a crest which forms high water at that place. at the same time, the water is acted on by the centripetal effect of gravity, which, tending to draw it as near as possible to the centre of the earth, acts in opposition to the attraction of the sun and moon, so that at the sides of the earth 90 degrees away, where the attraction of the sun and moon is less, the centripetal force has more effect, and the water is drawn so as to form the trough of the wave, or low water, at those points. there is also the centrifugal force contained in the revolving globe, which has an equatorial diameter of about 8,000 miles and a circumference of 25,132 miles. as it takes 23 hr. 56 min 4 sec, or, say, twenty-four hours, to make a complete revolution, the surface at the equator travels at a speed of approximately 25,132/24 = 1,047 miles per hour. this centrifugal force is always constant, and tends to throw the water off from the surface of the globe in opposition to the centripetal force, which tends to retain the water in an even layer around the earth. it is asserted, however, as an explanation of the phenomenon which occurs, that the centripetal force acting at any point on the surface of the earth varies inversely as the square of the distance from that point to the moon, so that the centripetal force acting on the water at the side of the earth furthest removed from the moon is less effective than that on the side nearest to the moon, to the extent due to the length of the diameter of the earth. the result of this is that the centrifugal force overbalances the centripetal force, and the water tends to fly off, forming an anti-lunar wave crest at that point approximately equal, and opposite, to the wave crest at the point nearest to the moon. as the earth revolves, the crest of high water of the lunar tide remains opposite the centre of attraction of the sun and moon, so that a point on the surface will be carried from high water towards and past the trough of the wave, or low water, then past the crest of the anti-lunar tide, or high water again, and back to its original position under the moon. but while the earth is revolving the moon has traveled 13 degrees along the elliptical orbit in which she revolves around the earth, from west to east, once in 27 days 7 hr. 43 min, so that the earth has to make a fraction over a complete revolution before the same point is brought under the centre of attraction again this occupies on an average 52 min, so that, although we are taught that the tide regularly ebbs and flows twice in twenty-four hours, it will be seen that the tidal day averages 24 hr. 52 min, the high water of each tide in the southern ocean being at 12 hr. 26 min intervals. as a matter of fact, the tidal day varies from 24 hr. 35 min at new and full moon to 25 hr. 25 min at the quarters. although the moon revolves around the earth in approximately 27-1/3 days, the earth has moved 27 degrees on its elliptical orbit around the sun, which it completes once in 365± days, so that the period which elapses before the moon again occupies the same relative position to the sun is 29 days 12 hr. 43 min, which is the time occupied by the moon in completing her phases, and is known as a lunar month or a lunation. considered from the point of view of a person on the earth, this primary tidal wave constantly travels round the southern ocean at a speed of 13,500 miles in 24 hr. 52 min, thus having a velocity of 543 miles per hour, and measuring a length of 13,500/2 = 6,750 miles from crest to crest. if a map of the world be examined it will be noticed that there are three large oceans branching off the southern ocean, namely, the atlantic, pacific, and indian oceans; and although there is the same tendency for the formation of tides in these oceans, they are too restricted for any very material tidal action to take place. as the crest of the primary tidal wave in its journey round the world passes these oceans, the surface of the water is raised in them, which results in secondary or derivative tidal waves being sent through each ocean to the furthermost parts of the globe; and as the trough of the primary wave passes the same points the surface of the water is lowered, and a reverse action takes place, so that the derivative waves oscillate backwards and forwards in the branch oceans, the complete cycle occupying on the average 12 hr. 26 min every variation of the tides in the southern ocean is accurately reproduced in every sea connected with it. wave motion consists only in a vertical movement of the particles of water by which a crest and trough is formed alternately, the crest being as much above the normal horizontal line as the trough is below it; and in the tidal waves this motion extends through the whole depth of the water from the surface to the bottom, but there is no horizontal movement except of form. the late mr. j. scott russell described it as the transference of motion without the transference of matter; of form without the substance; of force without the agent. the action produced by the sun and moon jointly is practically the resultant of the effects which each would produce separately, and as the net tide-producing effect of the moon is to raise a crest of water 1.4 ft above the trough, and that of the sun is 0.6 ft (being in the proportion of i to 0.445), when the two forces are acting in conjunction a wave 1.4 + 0.6 = 2 ft high is produced in the southern ocean, and when acting in opposition a wave 1.4 0.6 = 0.8 ft high is formed. as the derivative wave, consisting of the large mass of water set in motion by the comparatively small rise and fall of the primary wave, is propagated through the branch oceans, it is affected by many circumstances, such as the continual variation in width between the opposite shores, the alterations in the depth of the channels, and the irregularity of the coast line. when obstruction occurs, as, for example, in the bristol channel, where there is a gradually rising bed with a converging channel, the velocity, and/or the amount of rise and fall of the derivative wave is increased to an enormous extent; in other places where the oceans widen out, the rise and/or velocity is diminished, and similarly where a narrow channel occurs between two pieces of land an increase in the velocity of the wave will take place, forming a race in that locality. although the laws governing the production of tides are well understood, the irregularities in the depths of the oceans and the outlines of the coast, the geographical distribution of the water over the face of the globe and the position and declivity of the shores greatly modify the movements of the tides and give rise to so many complications that no general formulae can be used to give the time or height of the tides at any place by calculation alone. the average rate of travel and the course of the flood tide of the derivative waves around the shores of great britain are as follows:--150 miles per hour from land's end to lundy island; 90 miles per hour from lundy to st. david's head; 22 miles per hour from st. david's head to holy head; 45-1/2 miles per hour from holyhead to solway firth; 194 miles per hour from the north of ireland to the north of scotland; 52 miles per hour from the north of scotland to the wash; 20 miles per hour from the wash to yarmouth; 10 miles per hour from yarmouth to harwich. along the south coast from land's end to beachy head the average velocity is 40 miles per hour, the rate reducing as the wave approaches dover, in the vicinity of which the tidal waves from the two different directions meet, one arriving approximately twelve hours later than the other, thus forming tides which are a result of the amalgamation of the two waves. on the ebb tide the direction of the waves is reversed. the mobility of the water around the earth causes it to be very sensitive to the varying attraction of the sun and moon, due to the alterations from time to time in the relative positions of the three bodies. fig. [footnote: plate i] shows diagrammatically the condition of the water in the southern ocean when the sun and moon are in the positions occupied at the time of new moon. the tide at a is due to the sum of the attractions of the sun and moon less the effect due to the excess of the centripetal force over centrifugal force. the tide at c is due to the excess of the centrifugal force over the centripetal force. these tides are known as "spring" tides. fig. 2 [footnote: plate i] shows the positions occupied at the time of full moon. the tide at a is due to the attraction of the sun plus the effect due to the excess of the centrifugal force over the centripetal force. the tide at c is due to the attraction of the moon less the effect due to the excess of the centripetal force over centrifugal force. these tides are also known as "spring" tides. fig. 3 [footnote: plate i] shows the positions occupied when the moon is in the first quarter; the position at the third quarter being similar, except that the moon would then be on the side of the earth nearest to b, the tide at a is compounded of high water of the solar tide superimposed upon low water of the lunar tide, so that the sea is at a higher level than in the case of the low water of spring tides. the tide at d is due to the attraction of the moon less the excess of centripetal force over centrifugal force, and the tide at b is due to the excess of centrifugal force over centripetal force. these are known as "neap" tides, and, as the sun is acting in opposition to the moon, the height of high water is considerably less than at the time of spring tides. the tides are continually varying between these extremes according to the alterations in the attracting forces, but the joint high tide lies nearer to the crest of the lunar than of the solar tide. it is obvious that, if the attracting force of the sun and moon were equal, the height of spring tides would be double that due to each body separately, and that there would be no variation in the height of the sea at the time of neap tides. it will now be of interest to consider the minor movements of the sun and moon, as they also affect the tides by reason of the alterations they cause in the attractive force. during the revolution of the earth round the sun the successive positions of the point on the earth which is nearest to the sun will form a diagonal line across the equator. at the vernal equinox (march 20) the equator is vertically under the sun, which then declines to the south until the summer solstice (june 21), when it reaches its maximum south declination. it then moves northwards, passing vertically over the equator again at the autumnal equinox (september 21), and reaches its maximum northern declination on the winter solstice (december 21). the declination varies from about 24 degrees above to 24 degrees below the equator. the sun is nearest to the southern ocean, where the tides are generated, when it is in its southern declination, and furthest away when in the north, but the sun is actually nearest to the earth on december 31 (perihelion) and furthest away on july i (aphelion), the difference between the maximum and minimum distance being one-thirtieth of the whole. the moon travels in a similar diagonal direction around the earth, varying between 18-1/2 degrees and 28-1/2 degreed above and below the equator. the change from north to south declination takes place every fourteen days, but these changes do not necessarily take place at the change in the phases of the moon. when the moon is south of the equator, she is nearer to the southern ocean, where the tides are generated. the new moon is nearest to the sun, and crosses the meridian at midday, while the full moon crosses it at midnight. the height of the afternoon tide varies from that of the morning tide; sometimes one is the higher and sometimes the other, according to the declination of the sun and moon. this is called the "diurnal inequality." the average difference between the night and morning tides is about 5 in on the east coast and about 8in on the west coast. when there is a considerable difference in the height of high water of two consecutive tides, the ebb which follows the higher tide is lower than that following the lower high water, and as a general rule the higher the tide rises the lower it will fall. the height of spring tides varies throughout the year, being at a maximum when the sun is over the equator at the equinoxes and at a minimum in june at the summer solstice when the sun is furthest away from the equator. in the southern ocean high water of spring tides occurs at mid-day on the meridian of greenwich and at midnight on the 180° meridian, and is later on the coasts of other seas in proportion to the time taken for the derivative waves to reach them, the tide being about threefourths of a day later at land's end and one day and a half later at the mouth of the thames. the spring tides around the coast of england are four inches higher on the average at the time of new moon than at full moon, the average rise being about 15 ft, while the average rise at neaps is 11 ft 6 in. the height from high to low water of spring tides is approximately double that of neap tides, while the maximum height to which spring tides rise is about 33 per cent. more than neaps, taking mean low water of spring tides as the datum. extraordinarily high tides may be expected when the moon is new or full, and in her position nearest to the earth at the same time as her declination is near the equator, and they will be still further augmented if a strong gale has been blowing for some time in the same direction as the flood tide in the open sea, and then changes when the tide starts to rise, so as to blow straight on to the shore. the pressure of the air also affects the height of tides in so far as an increase will tend to depress the water in one place, and a reduction of pressure will facilitate its rising elsewhere, so that if there is a steep gradient in the barometrical pressure falling in the same direction as the flood tide the tides will be higher. as exemplifying the effect of violent gales in the atlantic on the tides of the bristol channel, the following extract from "the surveyor, engineer, and architect" of 1840, dealing with observations taken on mr. bunt's self-registering tide gauge at hotwell house, clifton, may be of interest. date: times of high water. difference in jan 1840. tide gauge. tide table. tide table. h.m. h.m. 27th, p.m....... 0. 8 ....... 0. 7 ..... 1 min earlier. 28th, a.m....... 0.47 ....... 0.34 ..... 13 min earlier. 28th, p.m....... 11.41 ....... 1. 7 ..... 86 min later. 29th, a.m....... 1.29 ....... 1.47 ..... 18 min later. 29th, p.m....... 2.32 ....... 2.30 ..... 2 min earlier. although the times of the tides varied so considerably, their heights were exactly as predicted in the tide-table. the records during a storm on october 29, 1838, gave an entirely different result, as the time was retarded only ten or twelve minutes, but the height was increased by 8 ft on another occasion the tide at liverpool was increased 7 ft by a gale. the bristol channel holds the record for the greatest tide experienced around the shores of great britain, which occurred at chepstow in 1883, and had a rise of 48 ft 6 in the configuration of the bristol channel is, of course, conducive to large tides, but abnormally high tides do not generally occur on our shores more frequently than perhaps once in ten years, the last one occurring in the early part of 1904, although there may foe many extra high ones during this period of ten years from on-shore gales. where tides approach a place from different directions there may be an interval between the times of arrival, which results in there being two periods of high and low water, as at southampton, where the tides approach from each side of the isle of wight. the hour at which high water occurs at any place on the coast at the time of new or full moon is known as the establishment of that place, and when this, together with the height to which the tide rises above low water is ascertained by actual observation, it is possible with the aid of the nautical almanack to make calculations which will foretell the time and height of the daily tides at that place for all future time. by means of a tide-predicting machine, invented by lord kelvin, the tides for a whole year can be calculated in from three to four hours. this machine is fully described in the minutes of proceedings, inst.c.e., vol. lxv. the age of the tide at any place is the period of time between new or full moon and the occurrence of spring tides at that place. the range of a tide is the height between high and low water of that tide, and the rise of a tide is the height between high water of that tide and the mean low water level of spring tides. it follows, therefore, that for spring tides the range and rise are synonymous terms, but at neap tides the range is the total height between high and low water, while the rise is the difference between high water of the neap tide and the mean low water level of spring tides. neither the total time occupied by the flood and ebb tides nor the rate of the rise and fall are equal, except in the open sea, where there are fewer disturbing conditions. in restricted areas of water the ebb lasts longer than the flood. although the published tide-tables give much detailed information, it only applies to certain representative ports, and even then it is only correct in calm weather and with a very steady wind, so that in the majority of cases the engineer must take his own observations to obtain the necessary local information to guide him in the design of the works. it is impracticable for these observations to be continued over the lengthy period necessary to obtain the fullest and most accurate results, but, premising a general knowledge of the natural phenomena which affect the tides, as briefly described herein, he will be able to gauge the effect of the various disturbing causes, and interpret the records he obtains so as to arrive at a tolerably accurate estimate of what may be expected under any particular circumstances. generally about 25 per cent. of the tides in a year are directly affected by the wind, etc., the majority varying from 6 in to 12 in in height and from five to fifteen minutes in time. the effect of a moderately stiff gale is approximately to raise a tide as many inches as it might be expected to rise in feet under normal conditions. the liverpool tide-tables are based on observations spread over ten years, and even longer periods have been adopted in other places. much valuable information on this subject is contained in the following books, among others--and the writer is indebted to the various authors for some of the data contained in this and subsequent chapters--"the tides," by g. h. darwin, 1886; baird's manual of tidal observations, 1886; and "tides and waves," by w. h. wheeler, 1906, together with the articles in the "encyclopaedia britannica" and "chambers's encyclopaedia." chapter ii observations of the rise and fall of tides. the first step in the practical design of the sewage works is to ascertain the level of high and low water of ordinary spring and neap tides and of equinoctial tides, as well as the rate of rise and fall of the various tides. this is done by means of a tide recording instrument similar to fig. 4, which represents one made by mr. j. h. steward, of 457, west strand, london, w.c. it consists of a drum about 5 in diameter and 10 in high, which revolves by clockwork once in twenty-four hours, the same mechanism also driving a small clock. a diagram paper divided with vertical lines into twenty-four primary spaces for the hours is fastened round the drum and a pen or pencil attached to a slide actuated by a rack or toothed wheel is free to work vertically up and down against the drum. a pinion working in this rack or wheel is connected with a pulley over which a flexible copper wire passes through the bottom of the case containing the gauge to a spherical copper float, 8 inches diameter, which rises and falls with the tide, so that every movement of the tide is reproduced moment by moment upon the chart as it revokes. the instrument is enclosed in an ebonized cabinet, having glazed doors in front and at both sides, giving convenient access to all parts. inasmuch as the height and the time of the tide vary every day, it is practicable to read three days' tides on one chart, instead changing it every day. when the diagrams are taken of, the lines representing the water levels should be traced on to a continuous strip of tracing linen, so that the variations can be seen at a glance extra lines should be drawn, on the tracing showing the time at which the changes of the moon occur. fig. 5 is a reproduction to a small scale of actual records taken over a period of eighteen days, which shows true appearance of the diagrams when traced on the continuous strip. these observations show very little difference between the spring and neap tides, and are interesting as indicating the unreliability of basing general deductions upon data obtained during a limited period only. at the time of the spring tides at the beginning of june the conditions were not favourable to big tides, as although the moon was approaching her perigee, her declination had nearly reached its northern limit and the declination of the sun was 22° in the first quarter of the moon coincided very closely with the moon's passage over the equator, so that the neaps would be bigger than usual. at the period of the spring: tides, about the middle of june, although the time of full moon corresponded with her southernmost declination, she was approaching her apogee, and the declination of the sun was 23° 16' n., so that the tides would be lower than usual. in order to ensure accurate observations, the position chosen for the tide gauge should be in deep water in the immediate vicinity of the locus in quo, but so that it is not affected by the waves from passing vessels. wave motion is most felt where the float is in shallow water. a pier or quay wall will probably be most convenient, but in order to obtain records of the whole range of the tides it is of course necessary that the float should not be left dry at low water. in some instances the float is fixed in a well sunk above high water mark to such a depth that the bottom of it is below the lowest low water level, and a small pipe is then laid under the beach from the well to, and below, low water, so that the water stands continuously in the well at the same level as the sea. the gauge should be fixed on bearers, about 3 ft 6 in from the floor, in a wooden shed, similar to a watchman's box, but provided with a door, erected on the pier or other site fixed upon for the observations. a hole must be formed in the floor and a galvanized iron or timber tube about 10 in square reaching to below low water level fixed underneath, so that when the float is suspended from the recording instrument it shall hang vertically down the centre of the tube. the shed and tube must of course be fixed securely to withstand wind and waves. the inside of the tube must be free from all projections or floating matter which would interfere with the movements of the float, the bottom should be closed, and about four lin diameter holes should be cleanly formed in the sides near to the bottom for the ingress and egress of the water. with a larger number of holes the wave action will cause the diagram to be very indistinct, and probably lead to incorrectness in determining the actual levels of the tides; and if the tube is considerably larger than the float, the latter will swing laterally and give incorrect readings. a bench mark at some known height above ordnance datum should be set up in the hut, preferably on the top of the tube. at each visit the observer should pull the float wire down a short distance, and allow it to return slowly, thus making a vertical mark on the diagram, and should then measure the actual level of the surface of the water below the bench mark in the hut, so that the water line on the chart can be referred to ordnance datum. he should also note the correct time from his watch, so as to subsequently rectify any inaccuracy in the rate of revolution of the drum. the most suitable period for taking these observations is from about the middle of march to near the end of june, as this will include records of the high spring equinoctial tides and the low "bird" tides of june. a chart similar to fig. 6 should be prepared from the diagrams, showing the rise and fall of the highest spring tides, the average spring tides, the average neap tides, and the lowest neap tides, which will be found extremely useful in considering the levels of, and the discharge from, the sea outfall pipe. the levels adopted for tide work vary in different ports. trinity high-water mark is the datum adopted for the port of london by the thames conservancy; it is the level of the lower edge of a stone fixed in the face of the river wall upon the east side of the hermitage entrance of the london docks, and is 12 48 ft above ordnance datum. the liverpool tide tables give the heights above the old dock sill, which is now non-existent, but the level of it has been carefully preserved near the same position, on a stone built into the western wall of the canning half tide dock. this level is 40 ft below ordnance datum. at bristol the levels are referred to the old cumberland basin (o.c.b.), which is an imaginary line 58 ft below ordnance datum. it is very desirable that for sewage work all tide levels should be reduced to ordnance datum. a critical examination of the charts obtained from the tiderecording instruments will show that the mean level of the sea does not agree with the level of ordnance datum. ordnance datum is officially described as the assumed mean water level at liverpool, which was ascertained from observations made by the ordnance survey department in march, 1844, but subsequent records taken in may and june, 1859, by a self-recording gauge on st. george's pier, showed that the true mean level of the sea at liverpool is 0.068 ft below the assumed level. the general mean level of the sea around the coast of england, as determined by elaborate records taken at 29 places during the years 1859-60, was originally said to be, and is still, officially recognised by the ordnance survey department to be 0.65 ft, or 7.8 in, above ordnance datum, but included in these 29 stations were 8 at which the records were admitted to be imperfectly taken. if these 8 stations are omitted from the calculations, the true general mean level of the sea would be 0.623 ft, or 7.476 in, above ordnance datum, or 0.691 ft above the true mean level of the sea at liverpool. the local mean seal level at various stations around the coast varies from 0.982 ft below the general mean sea level at plymouth, to 1.260 ft above it at harwich, the places nearest to the mean being weymouth (.089 ft below) and hull (.038 ft above). it may be of interest to mention that ordnance datum for ireland is the level of low water of spring tides in dublin bay, which is 21 ft below a mark on the base of poolbeg lighthouse, and 7.46 ft below english ordnance datum. the lines of "high and low water mark of ordinary tides" shown upon ordnance maps represent mean tides; that is, tides halfway between the spring and the neap tides, and are generally surveyed at the fourth tide before new and full moon. the foreshore of tidal water below "mean high water" belongs to the crown, except in those cases where the rights have been waived by special grants. mean high water is, strictly speaking, the average height of all high waters, spring and neap, as ascertained over a long period. mean low water of ordinary spring tides is the datum generally adopted for the soundings on the admiralty charts, although it is not universally adhered to; as, for instance, the soundings in liverpool bay and the river mersey are reduced to a datum 20 ft below the old dock sill, which is 125 ft below the level of low water of ordinary spring tides. the datum of each chart varies as regards ordnance datum, and in the case of charts embracing a large area the datum varies along the coast. the following table gives the fall during each half-hour of the typical tides shown in fig, 6 (see page 15), from which it will be seen that the maximum rate occurs at about half-tide, while very little movement takes place during the half-hour before and the half-hour after the turn of the tide:-table i. rate of fall of tides. state of eqionoctial ordinary ordinary lowest tide. tides. spring tides. neap tides. neap tides. high water - - - -1/2 hour after 0.44 0.40 0.22 0.19 1 " " 0.96 0.80 0.40 0.31 1-1/2 " " 1.39 1.14 0.68 0.53 2 " " 1.85 1.56 0.72 0.59 2-1/2 " " 1.91 1.64 0.84 0.68 3 " " 1.94 1.66 0.86 0.70 3-1/2 " " 1.94 1.66 0.86 0.70 4 " " 1.91 1.64 0.84 0.68 4-1/2 " " 1.35 1.16 0.59 0.48 5 " " 1.27 1.09 0.57 0.46 5-1/2 " " 1.06 0.91 0.47 0.38 6 " " 1.04 0.89 0.46 0.37 6-1/2 " " 0.53 0.45 0.24 0.18 totals.... 17 ft 6 in 15 ft 0 in 7 ft 9 in 6 ft 3 in the extent to which the level of high water varies from tide to tide is shown in fig. 7 [footnote: plate iii.], which embraces a period of six months, and is compiled from calculated heights without taking account of possible wind disturbances. the varying differences between the night and morning tides are shown very clearly on this diagram; in some cases the night tide is the higher one, and in others the morning tide; and while at one time each successive tide is higher than the preceding one, at another time the steps showing: the set-back of the tide are very marked. during the earlier part of the year the spring-tides at new moon were higher than those at full moon, but towards june the condition became reversed. the influence of the position of the sun and moon on the height of the tide is apparent throughout, but is particularly marked during the exceptionally low spring tides in the early part of june, when the time of new moon practically coincides with the moon in apogee and in its most northerly position furthest removed from the equator. inasmuch as the tidal waves themselves have no horizontal motion, it is now necessary to consider by what means the movement of water along the shores is caused. the sea is, of course, subject to the usual law governing the flow of water, whereby it is constantly trying to find its own level. in a tidal wave the height of the crest is so small compared with the length that the surface gradient from crest to trough is practically flat, and does not lead to any appreciable movement; but as the tidal wave approaches within a few miles of the shore, it runs into shallow water, where its progress is checked, but as it is being pushed on from behind it banks up and forms a crest of sufficient height to form a more or less steep gradient, and to induce a horizontal movement of the particles of water throughout the whole depth in the form of a tidal current running parallel with the shore. the rate of this current depends upon the steepness of the gradient, and the momentum acquired will, in some instances, cause the current to continue to run in the same direction for some time after the tide has turned, i.e., after the direction of the gradient has been reversed; so that the tide may be making--or falling--in one direction, while the current is running the opposite way. it will be readily seen, then, that the flow of the current will be slack about the time of high and low water, so that its maximum rate will be at half-ebb and half-flood. if the tide were flowing into an enclosed or semienclosed space, the current could not run after the tide turned, and the reversal of both would be simultaneous, unless, indeed, the current turned before the tide. wind waves are only movements of the surface of the water, and do not generally extend for a greater depth below the trough of the wave than the crest is above it, but as they may affect the movement of the floating particles of sewage to a considerable extent it is necessary to record the direction and strength of the wind. the strength of the wind is sometimes indicated wind at the time of making any tidal observations. by reference to the beaufort scale, which is a graduated classification adopted by admiral beaufort about the year 1805. the following table gives the general description, velocity, and pressure of the wind corresponding to the tabular numbers on the scale:-[illustration: plate iii period of six months. to face page 20] the figures indicating the pressure of the wind in the foregoing table are low compared with those given by other authorities. from mutton's formula, the pressure against a plane surface normal to the wind would be 0.97 lb per sq. foot, with an average velocity of 15 miles per hour (22 ft per sec.), compared with o.67 lb given by admiral beaufort, and for a velocity of 50 miles per hour (73.3 ft per sec.) 10.75 lb, compared with 7.7lb semitone's formula, which is frequently used, gives the pressure as 0.005v^2 (miles per hour), so that for 15 miles per hour velocity the pressure would be 1.125 lb, and for 50 miles it would be l2.5 lb it must not be forgotten, however, that, although over a period of one hour the wind may _average_ this velocity or pressure, it will vary considerably from moment to moment, being far in excess at one time, and practically calm at another. the velocity of the wind is usually taken by a cup anemometer having four 9 in cups on arms 2 ft long. the factor for reducing the records varies from 2 to 3, according to the friction and lubrication, the average being 2.2. the pressure is obtained by multiplying the beaufort number cubed by 0.0105; and the velocity is found by multiplying the square root of the beaufort number cubed by 1.87. a tidal wave will traverse the open sea in a straight line, but as it passes along the coast the progress of the line nearest the shore is retarded while the centre part continues at the same velocity, so that on plan the wave assumes a convex shape and the branch waves reaching the shore form an acute angle with the coast line. chapter iii. current observations. there is considerable diversity in the design of floats employed in current observations, dependant to some extent upon whether it is desired to ascertain the direction of the surface drift or of a deep current, it does not by any means follow that they run in simultaneous directions. there is also sometimes considerable difference in the velocity of the current at different depths--the surface current being more susceptible to influence of wind. a good form of deep float is seen in fig. 8. it consists of a rod 2 in by 2 in, or 4 sq in the lower end of which a hollow wooden box about 6 in by 6 in is fixed, into which pebbles are placed to overcome the buoyancy of the float and cause it to take and maintain an upright position in the water with a length of 9in of the rod exposed above the surface. a small hole is formed in the top of the box for the insertion the pebbles, which is stopped up with a cork when the float is adjusted. the length of the rod will vary according to the depth of water, but it will generally be found convenient to employ a float about 10 ft and to have a spare one about 6 ft deep, but otherwise it is similar in all respects, for use in shallow water. a cheap float for gauging the surface drift can be made from an empty champagne bottle weighted with stones and partly filled with water. the top 12 in of rods and the cord and neck of the bottle, as the case may be, should be painted red, as this colour renders floats more conspicuous when in the water and gives considerable assistance in locating their position, especially when they are at some distance from the observer. a deep-sea float designed by mr. g. p. bidden for ascertaining the set of the currents along the base of the ocean has recently been used by the north sea fisheries investigation committee. it consists of a bottle shaped like a soda-water bottle, made of strong glass to resist the pressure of the water, and partly filled with water, so that just sufficient air is left in it to cause it to float. a length of copper wire heavy enough to cause it to sink is then attached to the bottle, which is then dropped into the sea at a defined place. when the end of the wire touches the bottom the bottle is relieved of some of its weight and travels along with the currents a short distance above the bed of the sea. about 20 per cent. of the bottles were recovered, either by being thrown up on the beach or by being fished up in trawl nets. [illustration: fig. 8.--detail of wood tidal float 10 feet deep.] a double float, weighing about 10 lb complete, was used for the tidal observations for the girdleness outfall sewer, aberdeen. the surface portion consisted of two sheet-iron cups soldered together, making a float 9 in in diameter and 6 in deep. the lower or submerged portion was made of zinc, cylindrical in shape, 16 in diameter and 16 in long, perforated at intervals with lin diameter holes and suspended by means of a brass chain from a swivel formed on the underside of the surface float. in gauging the currents the float is placed in the water at a defined point and allowed to drift, its course being noted and afterwards transferred to a plan. the time of starting should be recorded and observations of its exact position taken regularly at every quarter of an hour, so that the time taken in covering any particular distance is known and the length of travel during any quarter-hour period multiplied by four gives the speed of the current at that time in miles per hour. the method to be employed in ascertaining the exact position of the float from time to time is a matter which requires careful consideration, and is dependent upon the degree of accuracy required according to the importance of the scheme and the situation of neighbouring towns, frequented shores, oyster beds, and other circumstances likely to be injuriously affected by any possible or probable pollution by sewage. one method is to follow the float in a small boat carrying a marine compass which has the card balanced to remain in a horizontal position, irrespective of the tipping and rolling of the boat, and to observe simultaneously the bearing of two prominent landmarks, the position of which on the plan is known, at each of the quarter-hour periods at which the observations are to be taken. this method only gives very approximate results, and after checking the value of the observations made by its use, with contemporary observations taken by means of theodolites on the shore, the writer abandoned the system in favour of the theodolite method, which, however, requires a larger staff, and is therefore more expensive. in every case it is necessary to employ a boat to follow the float, not only so as to recover it at the end of each day's work, but principally to assist in approximately locating the float, which can then be found more readily when searching through the telescope of the theodolite. the boat should be kept about 10 ft to 20 ft from the float on the side further removed from the observers, except when surface floats are being used to ascertain the effect of the wind, when the boat should be kept to leeward of the float. although obviously with a large boat the observations can be pursued through rougher weather, which is an important point, still the difficulty of maintaining a large boat propelled by mechanical power, or sail, sufficiently near the float to assist the observers, prevents its use, and the best result will be obtained by employing a substantial, seaworthy rowing boat with a broad beam. the boatmen appreciate the inclusion of a mast, sails, and plenty of ballast in the equipment to facilitate their return home when the day's work is done, which may happen eight or nine miles away, with twilight fast passing into darkness. there should be two boatmen, or a man and a strong youth. in working with theodolites, it is as well before starting to select observation stations at intervals along the coast, drive pegs in the ground so that they can easily be found afterwards, and fix their position upon a 1/2500 ordnance map in the usual manner. it may, however, be found in practice that after leaving one station it is not possible to reach the next one before the time arrives for another sight to be taken. in this case the theodolite must be set up on magnetic north at an intermediate position, and sights taken to at least two landmarks, the positions of which are shown on the map, and the point of observation subsequently plotted as near as possible by the use of these readings. inasmuch as the sights will be taken from points on the edge of the shore, which is, of course, shown on the map, it is possible, after setting up to magnetic north, to fix the position with approximate accuracy by a sight to one landmark only, but this should only be done in exceptional circumstances. the method of taking the observations with two theodolites, as adopted by the writer, can best be explained by a reference to fig. 9, which represents an indented piece of the coast. the end of the proposed sea outfall sewer, from which point the observations would naturally start, is marked 1, the numerals 2, 3, 4, etc., indicating the positions of the float as observed from time to time. many intermediate observations would be taken, but in order to render the diagram more clear, these have not been shown. the lines of sight are marked 1a, 1b, etc. the points marked a1, a2, etc., indicate the first, second, etc., and subsequent positions of observer a; the points b1, b2, etc., referring to observer b. the dot-and-dash line shows the course taken by the float, which is ascertained after plotting the various observations recorded. it is very desirable to have a horse and trap in waiting to move the observers and their instruments from place to place as required, and each observer should be provided with small flags about 2 ft square, one white and one blue, for signalling purposes. the instruments are first set up at a1 and b1 respectively, and adjusted to read on to the predetermined point 1 where the float is to be put in then as soon as the boatmen have reached the vicinity of this point, the observers can, by means of the flags, direct them which way to row so as to bring the boat to the exact position required, and when this is done the anchor is dropped until it is time to start, which is signalled by the observers holding the flags straight above their heads. this is also the signal used to indicate to the men that the day's work is finished, and they can pick up the float and start for home. [illustration: fig. 9.--plan of indented coast-line llustrating method of taking current observations with two theodolites.] directly the float is put in the water, and at every even quarter of an hour afterwards, each observer takes a reading of its exact position, and notes the time. as soon as the readings are taken to the float in position 2, the observer a should take up his instrument and drive to a2, where he must set up ready to take reading 3 a quarter of an hour after reading 2. it will be noticed that he might possibly have been able to take the reading 3 from the position a1, but the angle made by the lines of sight from the two instruments would have been too acute for accurate work, and very probably the float would have been hidden by the headland, so that he could not take the reading at all. in order to be on the headland a4 at the proper time, a must be working towards it by getting to position a3 by the time reading 4 is due. although the remainder of the course of the float can be followed from b1 and a4, the instruments would be reading too much in the same line, so that b must move to b2 and then after reading 5 and 6 he should move to b3. as the float returns towards the starting point, a can remain in the position a4 while b goes to b4 and then moves back along the shore as the float progresses. the foregoing description is sufficient to indicate the general method of working, but the details will of course vary according to the configuration of the shore and the course taken by the float. good judgment is necessary in deciding when to move from one station to the next, and celerity in setting up, adjusting the instrument, and taking readings is essential. if the boatmen can be relied upon to keep their position near the float, very long sights can be taken with sufficient accuracy by observing the position of the boat, long after the float has ceased to be visible through the telescope. the lines of sight from each station should be subsequently plotted on the 1/2500 ordnance map; the intersection of each two corresponding sight lines giving the position of the float at that time. then if a continuous line is drawn passing through all the points of intersection it will indicate the course taken by the float. it is very desirable that the observers should be able to convey information to each other by signalling with the flags according to the morse code, as follows. the dashes represent a movement of the flag from a position in front of the left shoulder to near the ground on the right side and the dots a movement from the left shoulder to the right shoulder. table 3. morse alphabet. e . a .r .-. l .-.. w .-p .--. j .--i .. u ..f ..-. s ... v ...h .... t n -. k -.c -.-. y -.-d -.. x -..b -... m -g --. q --.z --.. o --the signal to attract attention at starting and to signify the end of the message is .. .. .. continued until it is acknowledged with a similar sign by the other observer; that for a repetition is .. -.. which is signalled when any part of the message is not understood, otherwise after each word is signalled the receiver waves to indicate he understands it. until proficiency is attained, two copies of the alphabet should be kept by each observer for reference, one for dispatching a message arranged in alphabetical order and the other far reading a message arranged as set out above. the white flag should be used when standing against a dark background, and the blue one when on the skyline or against a light background. the conditions in tidal rivers vary somewhat from those occurring on the coast. as the crest of the tidal wave passes the mouth of the river a branch wave is sent up the river. this wave has first to overcome the water flowing down the river, which is acting in opposition to it, and in so doing causes a banking up of the water to such a height that the inclination of the surface is reversed to an extent sufficient to cause a tidal current to run up the river. the momentum acquired by the water passing up-stream carries it to a higher level towards the head of the river than at the mouth, and, similarly, in returning, the water flowing down the river gains sufficient impetus to scoop out the water at the mouth and form a low water below that in the sea adjoining. owing to a flow of upland water down a river the ebb lasts longer than the flood tide by a period, increasing in length as the distance from the mouth of the river increases; and, similarly to the sea, the current may continue to run down a river after the tide has turned and the level of the water is rising. the momentum of the tide running up the centre of the river is in excess of that along the banks, so that the current changes near the shore before it does in the middle, and, as the sea water is of greater specific gravity than the fresh, weighing 64 lb per cubic foot against 62-1/2 lb, it flows up the bed of the river at the commencement of the tide, while the fresh water on the surface is running in the opposite direction. after a time the salt water becomes diffused in the fresh, so that the density of the water in a river decreases as the distance from the sea increases. the disposal of sewage discharged into a river is due primarily to the mixing action which is taking place; inasmuch as the tidal current which is the transporting agent rarely flows more rapidly than from two to four miles per hour, or, say, twelve to fifteen miles per tide. the extent to which the suspended matter is carried back again up stream when the current turns depends upon the quantity of upland water which has flowed into the upper tidal part of the river during the ebb tide, as this water occupies a certain amount of space, according to the depth and width of the river, and thus prevents the sea water flowing back to the position it occupied on the previous tide, and carrying with it the matter in suspension. the permanent seaward movement of sewage discharged into the thames at barking when there is only a small quantity of upland water is at the rate of about one mile per day, taking thirty days to travel the thirty-one miles to the sea, while at the mouth of the river the rate does not exceed onethird of a mile per day. chapter iv. selection of site for outfall sewer. the selection of the site for the sea outfall sewer is a matter requiring a most careful consideration of the many factors bearing on the point, and the permanent success of any scheme of sewage disposal depends primarily upon the skill shown in this matter. the first step is to obtain a general idea of the tidal conditions, and to examine the admiralty charts of the locality, which will show the general set of the main currents into which it is desirable the sewage should get as quickly as possible. the main currents may be at some considerable distance from the shore, especially if the town is situated in a bay, when the main current will probably be found running across the mouth of it from headland to headland. the sea outfall should not be in the vicinity of the bathing grounds, the pier, or parts of the shore where visitors mostly congregate; it should not be near oyster beds or lobster grounds. the prosperity--in fact, the very existence--of most seaside towns depends upon their capability of attracting visitors, whose susceptibilities must be studied before economic or engineering questions, and there are always sentimental objections to sewage works, however well designed and conducted they may be. it is desirable that the sea outfall should be buried in the shore for the greater part of its length, not only on account of these sentimental feelings, but as a protection from the force of the waves, and so that it should not interfere with boating; and, further, where any part of the outfall between high and low water mark is above the shore, scouring of the beach will inevitably take place on each side of it. the extreme end of the outfall should be below low-water mark of equinoctial tides, as it is very objectionable to have sewage running across the beach from the pipe to the water, and if the foul matter is deposited at the edge of the water it will probably be brought inland by the rising tide. several possible positions may present themselves for the sea outfall, and a few trial current observations should be made in these localities at various states of the tides and plotted on to a 1:2500 ordnance map. the results of these observations will probably reduce the choice of sites very considerably. levels should be taken of the existing subsidiary sewers in the town, or, if there are none, the proposed arrangement of internal sewers should be sketched out with a view to their discharging their contents at one or other of the points under consideration. it may be that the levels of the sewers are such that by the time they reach the shore they are below the level of low water, when, obviously, pumping or other methods of raising the sewage must be resorted to; if they are above low water, but below high water, the sewage could be stored during high water and run off at or near low water; or, if they are above high water, the sewage could run off continuously, or at any particular time that might be decided. observations of the currents should now be made from the selected points, giving special attention to those periods during which it is possible to discharge the sewage having regard to the levels of the sewers. these should be made with the greatest care and accuracy, as the final selection of the type of scheme to be adopted will depend very largely on the results obtained and the proper interpretation of them, by estimating, and mentally eliminating, any disturbing influences, such as wind, etc. care must also be taken in noting the height of the tide and the relative positions of the sun, moon, and earth at the time of making the observations, and in estimating from such information the extent to which the tides and currents may vary at other times when those bodies are differently situated. it is obvious that if the levels of the sewers and other circumstances are such that the sewage can safely be discharged at low water, and the works are to be constructed accordingly, it is most important to have accurate information as to the level of the highest low water which may occur in any ordinary circumstances. if the level of a single low water, given by a casual observation, is adopted without consideration of the governing conditions, it may easily be that the tide in question is a low one, that may not be repeated for several years, and the result would be that, instead of having a free outlet at low water, the pipe would generally be submerged, and its discharging capacity very greatly reduced. the run of the currents will probably differ at each of the points under consideration, so that if one point were selected the best result would be obtained by discharging the sewage at high water and at another point at low water, whereas at a third point the results would show that to discharge there would not be satisfactory at any stage of the tide unless the sewage were first partially or even wholly purified. if these results are considered in conjunction with the levels of the sewers definite alternative schemes, each of which would work satisfactory may be evolved, and after settling them in rough outline, comparative approximate estimates should be prepared, when a final scheme may be decided upon which, while giving the most efficient result at the minimum cost, will not arouse sentimental objections to a greater extent than is inherent to all schemes of sewage disposal. having thus selected the exact position of the outfall, the current observations from that point should be completed, so that the engineer may be in a position to state definitely the course which would be taken by sewage if discharged under any conditions of time or tide. this information is not particularly wanted by the engineer, but the scheme will have to receive the sanction of the local government board or of parliament, and probably considerable opposition will be raised by interested parties, which must be met at all points and overcome. in addition to this, it may be possible, and necessary, when heavy rain occurs, to allow the diluted sewage to escape into the sea at any stage of the tide; and, while it is easy to contend that it will not then be more impure than storm water which is permitted to be discharged into inland streams during heavy rainfall, the aforesaid sentimentalists may conjure up many possibilities of serious results. as far as possible the records should indicate the course taken by floats starting from the outfall, at high water, and at each regular hour afterwards on the ebb tide, as well as at low water and every hour on the flood tide. it is not, however, by any means necessary that they should be taken in this or any particular order, because as the height of the tide varies each day an observation taken at high water one day is not directly comparable with one taken an hour after high water the next day, and while perhaps relatively the greatest amount of information can be gleaned from a series of observations taken at the same state of the tide, but on tides of differing heights, still, every observation tells its own story and serves a useful purpose. deep floats and surface floats should be used concurrently to show the effect of the wind, the direction and force of which should be noted. if it appears that with an on-shore wind floating particles would drift to the shore, screening will be necessary before the sewage is discharged. the floats should be followed as long as possible, but at least until the turn of the current--that is to say, a float put in at or near high water should be followed until the current has turned at or near low water, and one put in at low water should be followed until after high water. in all references to low water the height of the tide given is that of the preceding high water. the time at which the current turns relative to high and low water at any place will be found to vary with the height of the tide, and all the information obtained on this point should be plotted on squared paper as shown on fig. 10, which represents the result of observations taken near the estuary of a large river where the conditions would be somewhat different from those holding in the open sea. the vertical lines represent the time before high or low water at which the current turned, and the horizontal lines the height of the tide, but the data will, of course, vary in different localities. [illustration: hours before turn of tide. fig 10] it will be noticed that certain of the points thus obtained can be joined up by a regular curve which can be utilised for ascertaining the probable time at which the current will turn on tides of height intermediate to those at which observations were actually taken. for instance, from the diagram given it can be seen that on a 20 ft tide the current will turn thirty minutes before the tide, or on a 15 ft tide the current will turn one hour before the tide. some of the points lie at a considerable distance from the regular curve, showing that the currents on those occasions were affected by some disturbing influence which the observer will probably be able to explain by a reference to his notes, and therefore those particular observations must be used with caution. the rate of travel of the currents varies in accordance with the time they have been running. directly after the turn there is scarcely any movement, but the speed increases until it reaches a maximum about three hours later and then it decreases until the next turn, when dead water occurs again. those observations which were started at the turn of the current and continued through the whole tide should be plotted as shown in fig. 11, which gives the curves relating to three different tides, but, provided a sufficiently large scale is adopted, there is no reason why curves relating to the whole range of the tides should not be plotted on one diagram. this chart shows the total distance that would be covered by a float according to the height of the tide; it also indicates the velocity of the current from time to time. it can be used in several ways, but as this necessitates the assumption that with tides of the same height the flow of the currents is absolutely identical along the coast in the vicinity of the outfall, the diagram should be checked as far as possible by any observations that may be taken at other states of tides of the same heights. suppose we require to know how far a float will travel if started at two hours after high water on a 12 ft tide. from fig. 10 we see that on a tide of this height the current turns two hours and a quarter before the tide; therefore two hours after high water will be four hours and a quarter after the turn of the current. if the float were started with the current, we see from fig. 11 that it would have travelled three miles in four hours and a quarter; and subtracting this from four miles, which is its full travel on a whole tide, we see that it will only cover one mile in the two hours and a quarter remaining before the current turns to run back again. although sewage discharged into the sea rapidly becomes so diffused as to lose its identity, still occasionally the extraneous substances in it, such as wooden matches, banana skins, etc., may be traced for a considerable distance; so that, as the sewage continues to be discharged into the sea moving past the outfall, there is formed what may be described as a body or column of water having possibilities of sewage contamination. if the time during which sewage is discharged is limited to two hours, and starts, say, at the turn of the current on a 12 ft tide, we see from fig. 11 that the front of this body of water will have reached a point five-eighths of a mile away when the discharge ceases; so that there will be a virtual column of water of a total length of five-eighths of a mile, in which is contained all that remains of the noxious matters, travelling through the sea along the course of the current. we see, further, that at a distance of three miles away this column would only take thirty minutes to pass a given point. the extent of this column of water will vary considerably according to the tide and the time of discharge; for instance, on a 22 ft tide, if the discharge starts one hour after the turn of the current and continues for two hours, as in the previous example, it will form a column four miles long, whereas if it started two hours after the current, and continued for the same length of time, the column would be six miles and a half long, but the percentage of sewage in the water would be infinitesimal. [illustration: hours after turn of current fig. 11] in some cases it may be essential that the sewage should be borne past a certain point before the current turns in order to ensure that it shall not be brought back on the return tide to the shore near the starting point. in other words, the sewage travelling along the line of a branch current must reach the junction on the line of the main current by a certain time in order to catch the connection. assuming the period of discharge will be two hours, and that the point which it is necessary to clear is situated three miles and a half from the outfall, the permissible time to discharge the sewage according to the height of the tide can be obtained from fig. 11. taking the 22 ft tide first, it will be seen that if the float started with the current it would travel twelve miles in the tide; three and a half from twelve leaves eight and a half miles. a vertical line dropped from the intersection of the eight miles and a half line with the curve of the current gives the time two hours and a half before the end, or four hours after the start of the current at which the discharge of the sewage must cease at the outfall in order that the rear part of the column can reach the required point before the current turns. as on this tide high water is about fifteen minutes after the current, the latest time for the two hours of discharge must be from one hour and three-quarters to three hours and three-quarters after high water. similarly with the 12 ft tide having a total travel of four miles: three and a half from four leaves half a mile, and a vertical line from the half-mile intersection gives one hour and three-quarters after the start of the current as the time for discharge to cease. high water is two hours and a quarter after the current; therefore the latest time for the period of discharge would be from two hours and a half to half an hour before high water, but, as during the first quarter of an hour the movement of the current, though slight, would be in the opposite direction, it would be advisable to curtail the time of discharge, and say that it should be limited to between two hours and a quarter and half an hour before high water. it is obvious that if sewage is discharged about two hours after high water the current will be nearing its maximum speed, but it will only have about three hours to run before it turns; so that, although the sewage may be removed with the maximum rapidity from the vicinity of the sea outfall, it will not be carried to any very great distance, and, of course, the greater the distance it is carried the more it will be diffused. it must be remembered that the foregoing data are only applicable to the locality they relate to, although after obtaining the necessary information similar diagrams can be made and used for other places; but enough has been said to show that when it is necessary to utilise the full effect of the currents the sewage should be discharged at a varying time before high or low water, as the case may be, according to the height of the tide. chapter v. volume of sewage. the total quantity of sewage to be dealt with per day can be ascertained by gauging the flow in those cases where the sewers are already constructed, but where the scheme is an entirely new one the quantity must be estimated. if there is a water supply system the amount of water consumed per day, after making due allowance for the quantity used for trade purposes and street watering, will be a useful guide. the average amount of water used per head per day for domestic purposes only may be taken as follows:-daily water supply (gallons per head per day.) dietetic purposes (cooking, drinking, &c.) 1 cleansing purposes (washing house utensils, clothes, &c.) 6 if water-closets are in general use, add 3 if baths are in general use, add 5 total 15 it therefore follows that the quantity of domestic sewage to be expected will vary from 7 to 15 gallons per head per day, according to the extent of the sanitary conveniences installed in the town; but with the advent of an up-to-date sewage scheme, probably accompanied by a proper water supply, a very large increase in the number of water-closets and baths may confidently be anticipated, and it will rarely be advisable to provide for a less quantity of domestic sewage than 15 gallons per head per day for each of the resident inhabitants. the problem is complicated in sea coast towns by the large influx of visitors during certain short periods of the year, for whom the sewerage system must be sufficient, and yet it must not be so large compared with the requirements of the residential population that it cannot be kept in an efficient state during that part of the year when the visitors are absent. the visitors are of two types--the daily trippers and those who spend several days or weeks in the town. the daily tripper may not directly contribute much sewage to the sewers, but he does indirectly through those who cater for his wants. the resident visitor will spend most of the day out of doors, and therefore cause less than the average quantity of water to be used for house-cleansing purposes, in addition to which the bulk of the soiled linen will not be washed in the town. an allowance of 10 gallons per head per day for the resident visitor and 5 gallons per head per day for the trippers will usually be found a sufficient provision. it is, of course, well known that the flow of sewage varies from day to day as well as from hour to hour, and while there is no necessity to consider the daily variation--calculations being based on the flow of the maximum day--the hourly variation plays a most important part where storage of the sewage for any length of time is an integral part of the scheme. there are many important factors governing this variation, and even if the most elaborate calculations are made they are liable to be upset at any time by the unexpected discharge of large quantities of trade wastes. with a small population the hourly fluctuation in the quantity of sewage flowing into the sewers is very great, but it reduces as the population increases, owing to the diversity of the occupations and habits of the inhabitants. in all cases where the residential portions of the district are straggling, and the outfall works are situated at a long distance from the centre of the town, the flow becomes steadier, and the inequalities are not so prominently marked at the outlet end of the sewer. the rate of flow increases more or less gradually to the maximum about midday, and falls off in the afternoon in the same gradual manner. the following table, based on numerous gaugings, represents approximately the hourly variations in the dry weather flow of the sewage proper from populations numbering from 1,000 to 10,000, and is prepared after deducting all water which may be present in the sewers resulting from the infiltration of subsoil water through leaky joints in the pipes, and from defective water supply fittings as ascertained from the night gaugings. larger towns have not been included in the table because the hourly rates of flow are generally complicated by the discharge of the trade wastes previously referred to, which must be the subject of special investigation in each case. [table no. 4. approximate hourly variation in the flow of sewage. percentage of total flow passing off in each hour. -----------+----------------------------------------------- | population. hour. +-----+-----+-----+-----+-----+-----+-----+----- |1,000|2,000|3,000|4,000|5,000|6,000|8,000|10,000 -----------+-----+-----+-----+-----+-----+-----+-----+----- midnight | 1.0 | 1.0 | 1.2 | 1.3 | 1.5 | 1.5 | 1.8 | 2.0 1.0 a.m. | 0.7 | 0.7 | 0.7 | 0.8 | 0.8 | 1.0 | 1.0 | 1.0 2.0 " | nil | nil | nil | nil | 0.2 | 0.2 | 0.3 | 0.5 3.0 " | nil | nil | nil | nil | nil | nil | nil | 0.2 4.0 " | nil | nil | nil | nil | nil | nil | nil | nil 5.0 " | nil | nil | nil | nil | nil | nil | nil | 0.2 6.0 " | 0.2 | 0.2 | 0.3 | 0.5 | 0.6 | 0.5 | 0.7 | 0.8 7.0 " | 0.5 | 0.5 | 1.0 | 1.5 | 1.6 | 1.7 | 2.0 | 2.5 8.0 " | 1.0 | 1.5 | 2.0 | 2.5 | 3.0 | 3.5 | 4.0 | 5.0 9.0 " | 3.5 | 4.5 | 4.5 | 4.8 | 5.5 | 5.8 | 6.0 | 6.5 10.0 " | 6.5 | 6.5 | 6.8 | 7.0 | 7.5 | 7.7 | 8.0 | 8.0 11.0 " |10.5 |11.0 |10.5 |10.0 | 9.6 | 9.3 | 9.0 | 8.8 noon |11.0 |11.3 |10.8 |10.3 | 9.3 | 9.5 | 9.2 | 9.0 1.0 p.m. | 6.0 | 5.5 | 6.0 | 6.7 | 7.0 | 7.2 | 7.3 | 7.5 2.0 " | 7.0 | 7.3 | 7.0 | 7.0 | 6.5 | 6.5 | 6.2 | 6.0 3.0 " | 6.8 | 6.5 | 6.5 | 6.5 | 6.5 | 6.3 | 6.3 | 6.0 4.0 " | 7.5 | 7.5 | 7.3 | 7.0 | 6.7 | 6.5 | 6.2 | 6.7 5.0 " | 6.5 | 6.5 | 6.5 | 6.3 | 6.0 | 6.0 | 6.0 | 5.8 6.0 " | 4.5 | 4.5 | 4.7 | 4.8 | 5.0 | 5.0 | 5.0 | 5.2 7.0 " | 6.5 | 6.2 | 6.0 | 5.8 | 5.5 | 5.5 | 5.5 | 4.7 8.0 " | 6.2 | 6.0 | 5.8 | 5.5 | 5.5 | 5.3 | 5.0 | 4.8 9.0 " | 5.0 | 4.8 | 4.7 | 4.5 | 4.5 | 4.5 | 4.5 | 4.0 10.0 " | 4.8 | 4.6 | 4.2 | 4.0 | 3.8 | 3.5 | 3.0 | 3.0 11.0 " | 4.3 | 3.5 | 3.5 | 3.2 | 3.2 | 3.0 | 3.0 | 2.8 -----------+-----+-----+-----+-----+-----+-----+-----+----- total |100.0|100.0|100.0|100.0|100.0|100.0|100.0|100.0 -----------+-----+-----+-----+-----+-----+-----+-----+-----analysis of flow] percentage of total flow passing off during period named. ---------------------+----------------------------------------------------------------+ | population. | +-------+-------+-------+-------+-------+-------+-------+--------+ | 1,000 | 2,000 | 3,000 | 4,000 | 5,000 | 6,000 | 8,000 | 10,000 | ---------------------+-------+-------+-------+-------+-------+-------+-------+--------+ 7.0 a.m. to 7.0 p.m | 77.3 | 78.8 | 78.6 | 78.7 | 78.5 | 78.8 | 78.7 | 75.2 | 7.0 p.m. to 7.0 a.m | 22.7 | 21.2 | 21.4 | 21.3 | 21.5 | 21.2 | 21.3 | 21.8 | maximum 12 hrs. | 84.0 | 83.6 | 82.6 | 81.7 | 81.0 | 80.6 | 79.7 | 78.2 | " 10 " | 72.8 | 72.8 | 72.1 | 71.4 | 70.0 | 69.8 | 69.2 | 68.5 | " 9 " | 66.3 | 66.6 | 66.1 | 65.6 | 64.5 | 64.8 | 64.2 | 63.3 | " 8 " | 61.8 | 62.1 | 61.4 | 60.8 | 59.5 | 59.0 | 58.2 | 57.5 | " 6 " | 48.8 | 49.1 | 43.1 | 47.5 | 46.8 | 46.5 | 46.0 | 45.8 | " 3 " | 23.0 | 28.8 | 27.11| 27.3 | 26.8 | 26.5 | 26.2 | 25.8 | " 2 " | 21.5 | 22.3 | 21.3 | 20.3 | 19.3 | 18.5 | 18.2 | 17.3 | " 1 " | 11.0 | 11.3 | 10.8 | 10.3 | 9.8 | 9.5 | 9.2 | 9.0 | minimum 9 " | 3.4 | 3.9 | 5.2 | 6.6 | 7.5 | 6.9 | 8.8 | 10.0 | " 10 " | 6.9 | 7.4 | 8.7 | 9.8 | 10.7 | 10.4 | 11.8 | 13.0 | ---------------------+-------+-------+-------+-------+-------+-------+-------+--------+ the data in the foregoing table, so far as they relate to populations of one, five, and ten thousand respectively, are reproduced graphically in fig. 12. this table and diagram relate only to the flow of sewage--that is, water which is intentionally fouled; but unfortunately it is almost invariably found that the flow in the sewers is greater than is thus indicated, and due allowance must be made accordingly. the greater the amount of extra liquid flowing in the sewers as a permanent constant stream, the less marked will be the hourly variations; and in one set of gaugings which came under the writer's notice the quantity of extraneous liquid in the sewers was so greatly in excess of the ordinary sewage flow that, taken as a percentage of the total daily flow, the hourly variation was almost imperceptible. [illustration: fig 12 hourly variation in flow of sewage.] provision must be made in the scheme for the leakage from the water fittings, and for the subsoil water, which will inevitably find its way into the sewers. the quantity will vary very considerably, and is difficult of estimation. if the water is cheap, and the supply plentiful, the water authority may not seriously attempt to curtail the leakage; but in other cases it will be reduced to a minimum by frequent house to house inspection; some authorities going so far as to gratuitously fix new washers to taps when they are required. theoretically, there should be no infiltration of subsoil water, as in nearly all modern sewerage schemes the pipes are tested and proved to be watertight before the trenches are filled in; but in practice this happy state is not obtainable. the pipes may not all be bedded as solidly as they should be, and when the pressure of the earth comes upon them settlement takes place and the joints are broken. joints may also be broken by careless filling of trenches, or by men walking upon the pipes before they are sufficiently covered. some engineers specify that all sewers shall be tested and proved to be absolutely water-tight before they are "passed" and covered in, but make a proviso that if, after the completion of the works, the leakage into any section exceeds 1/2 cubic foot per minute per mile of sewer, that length shall be taken up and relaid. even if the greatest vigilance is exercised to obtain water-tight sewers, the numerous house connections are each potential sources of leakage, and when the scheme is complete there may be a large quantity of infiltration water to be dealt with. where there are existing systems of old sewers the quantity of infiltration water can be ascertained by gauging the night flow; and if it is proved to be excessive, a careful examination of the course of the sewers should be made with a view to locating the places where the greater part of the leakage occurs, and then to take such steps as may be practicable to reduce the quantity. chapter vi. gauging flow in sewers. a method frequently adopted to gauge the flow of the sewage is to fix a weir board with a single rectangular notch across the sewer in a convenient manhole, which will pond up the sewage; and then to ascertain the depth of water passing over the notch by measurements from the surface of the water to a peg fixed level with the bottom of the notch and at a distance of two or three feet away on the upstream side. the extreme variation in the flow of the sewage is so great, however, that if the notch is of a convenient width to take the maximum flow, the hourly variation at the time of minimum flow will affect the depth of the sewage on the notch to such a small extent that difficulty may be experienced in taking the readings with sufficient accuracy to show such variations in the flow, and there will be great probability of incorrect results being obtained by reason of solid sewage matter lodging on the notch. when the depth on a l2 in notch is about 6 in, a variation of only 1-16th inch in the vertical measurement will represent a difference in the rate of the flow of approximately 405 gallons per hour, or about 9,700 gallons per day. when the flow is about lin deep the same variation of 1-16th in will represent about 162 gallons per hour, or 3,900 gallons per day. greater accuracy will be obtained if a properly-formed gauging pond is constructed independently of the manhole and a double rectangular notch, similar to fig. 13, or a triangular or vshaped notch, as shown in fig. 14, used in lieu of the simpler form. in calculating the discharge of weirs there are several formulæ to choose from, all of which will give different results, though comparative accuracy has been claimed for each. taking first a single rectangular notch and reducing the formulae to the common form: ____ discharge per foot in width of weir = c \/ h^3 where h = depth from the surface of still water above the weir to the level of the bottom of the notch, the value of c will be as set out in the following table:- table no. 5. rectangular notches. _____ discharge per foot in width of notch = c \/ h^3 ----------------------------------------------------------------- values of c. --------------------------------------+-------------------------- h measured in | feet. | inches. ---------------+-----------+----------+-----------+-------------- | gallons | c. ft | gallons | c. ft discharge in | per hour. | per min | per hour. | per min ---------------+-----------+----------+-----------+-------------- authority. | | | | box | 79,895 | 213.6 | 1,922 | 5.13 cotterill | 74,296 | 198.6 | 1,787 | 4.78 francis | 74,820 | 200.0 | 1,800 | 4.81 mo'esworth | 80,057 | 214.0 | 1,926 | 5.15 santo crimp | 72,949 | 195.0 | 1,755 | 4.69 ---------------+-----------+----------+-----------+--------------in the foregoing table francis' short formula is used, which does not take into account the end contractions and therefore gives a slightly higher result than would otherwise be the case, and in cotterill's formula the notch is taken as being half the width of the weir, or of the stream above the weir. if a cubic foot is taken as being equal to 6-1/4 gallons instead of 6.235 gallons, then, cubic feet per minute multiplied by 9,000 equals gallons per day. this table can be applied to ascertain the flow through the notch shown in fig. 13 in the following way. suppose it is required to find the discharge in cubic feet per minute when the depth of water measured in the middle of the notch is 4 in using santo crimp's formula the result will be c\/h^3 = 4.69 \/4^3 = 4.69 x 8 = 37.52 cubic feet per foot in width of weir, but as the weir is only 6 in wide, we must divide this figure by 2, then 37.52/2 = 18.76 cubic feet, which is the discharge per minute. +------+ +------+ | | fig. 13 | | | | | | | | | | | +------+ +------+ | | | | | | | | | | | | | | +------+ | | | | | | | | | +----------------------------------+ fig. 13.-elevation of double rectangular notched gauging weir. +------+ +------+ | \ fig. 13 / | | \ / | | \ / | | \ / | | \ / | | \ / | | \ / | | \ / | | \ / | | \/ | | | | | | | | | | | +----------------------------------+ fig. 14.-elevation of triangular notched gauging weir. fig. 15.-longitudinal section, showing weir, gauge-peg, and hook-gauge if it is required to find the discharge in similar terms with a depth of water of 20 in, two sets of calculations are required. first 20 in depth on the notch 6 in wide, and then 4 in depth on the notch, 28 in minus 6 in, or 1 ft wide. ____ _____ (1) c\/ h^3 = 4.69/2 \/ 10^3 = 2.345 x 31.62 = 74.15 ____ ____ (2) c\/ h^3 = 1.0 x 4.69 \/ 4^3 = 1.0 x 4.69 x 8 = 37.52 total in c. ft per min = 111.67 the actual discharge would be slightly in excess of this. in addition to the circumstances already enumerated which affect the accuracy of gaugings taken by means of a weir fixed in a sewer there is also the fact that the sewage approaches the weir with a velocity which varies considerably from time to time. in order to make allowance for this, the head calculated to produce the velocity must be added to the actual head. this can be embodied in the formula, as, for example, santo crimp's formula for discharge in cubic feet per minute, with h measured in feet, is written __________________ 195\/(11^3 + .035v h^2 instead of the usual form of ____ 195\/ h^3, which is used when there is no velocity to take into account. the v represents the velocity in feet per second. triangular or v notches are usually formed so that the angle between the two sides is 90°, when the breadth at any point will always be twice the vertical height measured at the centre. the discharge in this case varies as the square root of the fifth power of the height instead of the third power as with the rectangular notch. the reason for the alteration of the power is that _approximately_ the discharge over a notch with any given head varies as the cross-sectional area of the body of water passing over it. the area of the 90° notch is half that of a circumscribing rectangular notch, so that the discharge of a v notch is approximately equal to that of a rectangular notch having a width equal to half the width of the v notch at water level, and as the total width is equal to double the depth of water passing over the notch the half width is equal to the full depth and the discharge is equal to that of a rectangular notch having a width equal to the depth of water flowing over the v notch from time to time, both being measured in the same unit, therefore ____ ____ ____ c \/ h^3 becomes c x h x \/ h^3 which equals c \/ h^5. the constant c will, however, vary from that for the rectangular notch to give an accurate result. table no. 6. triangular or v notches. ____ discharge = c x \/ h^5. values of c. --------------+-----------------------+----------------------- h measured in | feet. | inches. --------------+----------+------------+-----------+----------- discharge in | gallons | c. ft per | gallons | c. ft per | per hour | min | per hour. | min --------------+----------+------------+-----------+----------- alexander | 59,856 | 160 | 120.0 | 0.321 cotterill | 57,013 | 152.4 | 114.3 | 0.306 molesworth | 59,201 | 158.2 | 118.7 | 0.317 thomson | 57,166 | 152.8 | 114.6 | 0.306 --------------+----------+------------+-----------+-----------cotterill's formula for the discharge in cubic feet per minute is _______ 16 x c x b \/ 2g h^3 when b = breadth of notch in feet and h = height of water in feet and can be applied to any proportion of notch. when b = 2h, that is, a 90° notch, c = .595 and the formula becomes ____ 152.4 \/ h^5, and when b = 4h, that is, a notch containing an angle of 126° 51' 36", c = .62 and the formula is then written ____ 318 \/ h^5. the measurements of the depth of the water above the notch should be taken by a hook-gauge, as when a rule or gauge-slate is used the velocity of the water causes the latter to rise as it comes in contact with the edge of the measuring instrument and an accurate reading is not easily obtainable, and, further, capillary attraction causes the water to rise up the rule above the actual surface, and thus to show a still greater depth. when using a hook-gauge the top of the weir, as well as the notch, should be fixed level and a peg or stake fixed as far back as possible on the upstream side of the weir, so that the top of the peg is level with the top of the weir, instead of with the notch, as is the case when a rule or gauge-slate is used. the hook-gauge consists of a square rod of, say, lin side, with a metal hook at the bottom, as shown in fig. 15, and is so proportioned that the distance from the top of the hook to the top of the rod is equal to the difference in level of the top of the weir and the sill of the notch. in using it the rod of the hook-gauge is held against the side of the gauge-peg and lowered into the water until the point of the hook is submerged. the gauge is then gently raised until the point of the hook breaks the surface of the water, when the distance from the top of the gauge-peg to the top of the rod of the hook-gauge will correspond with the depth of the water flowing over the weir. chapter vii. rainfall. the next consideration is the amount of rain-water for which provision should be made. this depends on two factors: first, the amount of rain which may be expected to fall; and, secondly, the proportion of this rainfall which will reach the sewers. the maximum rate at which the rain-water will reach the outfall sewer will determine the size of the sewer and capacity of the pumping plant, if any, while if the sewage is to be stored during certain periods of the tide the capacity of the reservoir will depend upon the total quantity of rain-water entering it during such periods, irrespective of the rate of flow. some very complete and valuable investigations of the flow of rain-water in the birmingham sewers were carried out between 1900 and 1904 by mr. d. e. lloyd-davies, m.inst.c. e., the results of which are published in vol. clxiv., min proc. inst.c.e. he showed that the quantity reaching the sewer at any point was proportional to the time of concentration at that point and the percentage of impermeable area in the district. the time of concentration was arrived at by calculating the time which the rain-water would take to flow through the longest line of sewers from the extreme boundaries of the district to the point of observation, assuming the sewers to be flowing half full; and adding to the time so obtained the period required for the rain to get into the sewers, which varied from one minute where the roofs were connected directly with the sewers to three minutes where the rain had first to flow along the road gutters. with an average velocity of 3 ft per second the time of concentration will be thirty minutes for each mile of sewer. the total volume of rain-water passing into the sewers was found to bear the same relation to the total volume of rain falling as the maximum flow in the sewers bore to the maximum intensity of rainfall during a period equal to the time of concentration. he stated further that while the flow in the sewers was proportional to the aggregate rainfall during the time of concentration, it was also directly proportional to the impermeable area. putting this into figures, we see that in a district where the whole area is impermeable, if a point is taken on the main sewers which is so placed that rain falling at the head of the branch sewer furthest removed takes ten minutes to reach it, then the maximum flow of storm water past that point will be approximately equal to the total quantity of rain falling over the whole drainage area during a period of ten minutes, and further, that the total quantity of rainfall reaching the sewers will approximately equal the total quantity falling. if, however, the impermeable area is 25 per cent. of the whole, then the maximum flow of storm water will be 25 per cent. of the rain falling during the time of concentration, viz., ten minutes, and the total quantity of storm water will be 25 per cent. of the total rainfall. if the quantity of storm water is gauged throughout the year it will probably be found that, on the average, only from 70 per cent. to 80 per cent. of the rain falling on the impermeable areas will reach the sewers instead of 100 per cent., as suggested by mr. lloyd-davies, the difference being accounted for by the rain which is required to wet the surfaces before any flow off can take place, in addition to the rain-water collected in tanks for domestic use, rain required to fill up gullies the water level of which has been lowered by evaporation, and rain-water absorbed in the joints of the paving. the intensity of the rainfall decreases as the period over which the rainfall is taken is increased. for instance, a rainfall of lin may occur in a period of twenty minutes, being at the rate of 3 in per hour, but if a period of one hour is taken the fall during such lengthened time will be considerably less than 3 in in towns where automatic rain gauges are installed and records kept, the required data can be abstracted, but in other cases it is necessary to estimate the quantity of rain which may have to be dealt with. it is impracticable to provide sewers to deal with the maximum quantity of rain which may possibly fall either in the form of waterspouts or abnormally heavy torrential rains, and the amount of risk which it is desirable to run must be settled after consideration of the details of each particular case. the following table, based principally upon observations taken at the birmingham observatory, shows the approximate rainfall which may be taken according to the time of concentration. table no. 7. intensity of rainfall during limited periods. equivalent rate in inches per hour of aggregate rainfall during time of concentration, period of concentration a b c d e 5 minutes ............... 1.75 2.00 3.00 - -10 " ............... 1.25 1.50 2.00 - -15 " ............... 1.05 1.25 1.50 - -20 " ............... 0.95 1.05 1.30 1.20 3.00 25 " ............... 0.85 0.95 1.15 - -30 " ............... 0.80 0.90 1.05 1.00 2.50 35 " ............... 0.75 0.85 0.95 - -40 " ............... 0.70 0.80 0.90 - -45 " ............... 0.65 0.75 0.85 - - 1 hour .................. 0.50 0.60 0.70 0.75 1.80 1-1/2 " .................. 0.40 0.50 0.60 - 1.40 2 " .................. 0.30 0.40 0.50 0.50 1.10 the figures in column a will not probably be exceeded more than once in each year, those in column b will not probably be exceeded more than once in three years, while those in column c will rarely be exceeded at all. columns d and e refer to the records tabulated by the meteorological office, the rainfall given in column d being described in their publication as "falls too numerous to require insertion," and those in column e as "extreme falls rarely exceeded." it must, however, be borne in mind that the meteorological office figures relate to records derived from all parts of the country, and although the falls mentioned may occur at several towns in any one year it may be many years before the same towns are again visited by storms of equal magnitude. while it is convenient to consider the quantity of rainfall for which provision is to be made in terms of the rate of fall in inches per hour, it will be useful for the practical application of the figures to know the actual rate of flow of the storm water in the sewers at the point of concentration in cubic feet per minute per acre. this information is given in the following table no. 8, which is prepared from the figures given in table no. 7, and is applicable in the same manner. table no. 8. maximum flows of storm water. --------------------------+--------------------------------- | maximum storm water flow in | cubic feet per min per acre | of impervious area. time of concentration. +------+------+------+------+----- | a | b | c | d | e --------------------------+------+------+------+------+----- 5 minutes | 106 | 121 | 181 | -| - 10 " | 75 | 91 | 121 | -| - 15 " | 64 | 75 | 91 | -| - 20 " | 57 | 64 | 79 | 73 | 181 25 " | 51 | 57 | 70 | -| - 30 " | 48 | 54 | 64 | 61 | 151 35 " | 45 | 51 | 57 | -| - 40 " | 42 | 48 | 54 | -| - 45 " | 39 | 45 | 51 | -| - 1 hour | 30 | 36 | 42 | 45 | 109 1-1/2 " | 24 | 30 | 36 | -| 85 2 " | 18 | 24 | 30 | 30 | 67 --------------------------+------+------+------+------+------ l inch of rain = 3,630 cub. feet per acre. the amount of rainfall for which storage has to be provided is a difficult matter to determine; it depends on the frequency and efficiency of the overflows and the length of time during which the storm water has to be held up for tidal reasons. it is found that on the average the whole of the rain on a rainy day falls within a period of 2-1/2 hours; therefore, ignoring the relief which may be afforded by overflows, if the sewers are tide-locked for a period of 2-1/2 hours or over it would appear to be necessary to provide storage for the rainfall of a whole day; but in this case again it is permissible to run a certain amount of risk, varying with the length of time the sewers are tide-locked, because, first of all, it only rains on the average on about 160 days in the year, and, secondly, when it does rain, it may not be at the time when the sewers are tide-locked, although it is frequently found that the heaviest storms occur just at the most inconvenient time, namely, about high water. table no. 9 shows the frequency of heavy rain recorded during a period of ten years at the birmingham observatory, which, being in the centre of england, may be taken as an approximate average of the country. table no. 9. frequency of heavy rain ------------------------------------------------------total daily rainfall. average frequency of rainfall ------------------------------------------------------0.4 inches and over 155 times each year 0.5 " 93 " 0.6 " 68 " 0.7 " 50 " 0.8 " 33 " 0.9 " 22 " 1.0 " 17 " 1.1 " once each year 1.2 " once in 17 months 1.25 " " 2 years 1.3 " " 2-1/2 1.4 " " 3-1/3 1.5 " " 5 years 1.6 " " 5 years 1.7 " " 5 years 1.8 " " 10 years 1.9 " " 10 years 2.0 " " 10 years -------------------------------------------------it will be interesting and useful to consider the records for the year 1903, which was one of the wettest years on record, and to compare those taken in birmingham with the mean of those given in "symons' rainfall," taken at thirty-seven different stations distributed over the rest of the country. table no. 10. rainfall for 1903. mean of 37 stations in birmingham england and wales. daily rainfall of 2 in and over ...... none 1 day daily rainfall of 1 in and over ...... 3 days 6 days daily rainfall of 1/2 in and over .... 17 days 25 days number of rainy days.................. 177 days 211 days total rainfall ...................... 33.86 in 44.89 in amount per rainy day ................ 0.19 in 0.21 in the year 1903 was an exceptional one, but the difference existing between the figures in the above table and the average figures in table 9 are very marked, and serve to emphasise the necessity for close investigation in each individual case. it must be further remembered that the wettest year is not necessarily the year of the heaviest rainfalls, and it is the heavy rainfalls only which affect the design of sewerage works. chapter viii. storm water in sewers. if the whole area of the district is not impermeable the percentage which is so must be carefully estimated, and will naturally vary in each case. the means of arriving at an estimate will also probably vary considerably according to circumstances, but the following figures, which relate to investigations recently made by the writer, may be of interest. in the town, which has a population of 10,000 and an area of 2,037 acres, the total length of roads constructed was 74,550 lineal feet, and their average width was 36 ft, including two footpaths. the average density of the population was 4.9 people per acre. houses were erected adjoining a length of 43,784 lineal feet of roads, leaving 30,766 lineal feet, which for distinction may be called "undeveloped"--that is, the land adjoining them was not built over. dividing the length of road occupied by houses by the total number of the inhabitants of the town, the average length of road per head was 4.37 ft, and assuming five people per house and one house on each side of the road we get ten people per two houses opposite each other. then 10 x 4.37 = 43.7 lineal feet of road frontage to each pair of opposite houses. after a very careful inspection of the whole town, the average area of the impermeable surfaces appertaining to each house was estimated at 675 sq. ft, of which 300 sq. ft was apportioned to the front roof and garden paths and 375 sq. ft to the back roof and paved yards. dividing these figures by 43.71 in ft of road frontage per house, we find that the effective width of the impermeable roadway is increased by 6 ft 10 in for the front portions of each house, and by a width of 8 ft 7 in, for the back portions, making a total width of 36 ft + 2(6 ft 10 in) + 2(8 ft 7 in) = 66 ft 10 in, say 67 ft on this basis the impermeable area in the town therefore equals: 43,7841 in ft x 67 ft =2,933,528; and 30,766 lin ft x 36 ft = 1,107,576. total, 4,041,104 sq. ft, or 92.77 acres. as the population is 10,000 the impermeable area equals 404, say, 400 sq. ft per head, or ~ (92.77 x 100) / 2037 = 4.5 per cent, of the whole area of the town. it must be remembered that when rain continues for long periods, ground which in the ordinary way would generally be considered permeable becomes soaked and eventually becomes more or less impermeable. mr. d. e. lloyd-davies, m.inst.c.e., gives two very interesting diagrams in the paper previously referred to, which show the average percentage of effective impermeable area according to the population per acre. this information, which is applicable more to large towns, has been embodied in fig. 16, from which it will be seen that, for storms of short duration, the proportion of impervious areas equals 5 per cent. with a population of 4.9 per acre, which is a very close approximation to the 4.5 per cent. obtained in the example just described. where the houses are scattered at long intervals along a road the better way to arrive at an estimate of the quantity of storm water which may be expected is to ascertain the average impervious area of, or appertaining to, each house, and divide it by five, so as to get the area per head. then the flow off from any section of road is directly obtained from the sum of the impervious area due to the length of the road, and that due to the population distributed along it. [illustration: fig. 16.--variation in average percentage of effective impermeable area according to density of population.] in addition to being undesirable from a sanitary point of view, it is rarely economical to construct special storm water drains, but in all cases where they exist, allowance must be made for any rain that may be intercepted by them. short branch sewers constructed for the conveyance of foul water alone are usually 9in or 12 in in diameter, not because those sizes are necessary to convey the quantity of liquid which may be expected, but because it is frequently undesirable to provide smaller public sewers, and there is generally sufficient room for the storm water without increasing the size of the sewer. if this storm water were conveyed in separate sewers the cost would be double, as two sewers would be required in the place of one. in the main sewers the difference is not so great, but generally one large sewer will be more economical than two smaller ones. where duplicate sewers are provided and arranged, so that the storm water sewer takes the rain-water from the roads, front roofs and gardens of the houses, and the foul water sewer takes the rain-water from the back roofs and paved yards, it was found in the case previously worked out in detail that in built-up roads a width of 36 ft + 2 (8 ft 7 in) = 53 ft 2 in, or, say, 160 sq. ft per lineal yard of road would drain to the storm water sewer, and a width of 2 (6 ft 10 in) = 13 ft 8 in, or, say, 41 sq. ft per lineal yard of road to the foul water sewer. this shows that even if the whole of the rain which falls on the impervious areas flows off, only just under 80 per cent. of it would be intercepted by the special storm water sewers. taking an average annual rainfall of 30 in, of which 75 per cent. flows off, the quantity reaching the storm water sewer in the course of a year from each lineal 30 75 yard of road would be --x 160 x --= 300 cubic 12 100 feet = 1,875 gallons. [illustration: fig. 17.--section of "leap weir" overflow] the cost of constructing a separate surface water system will vary, but may be taken at an average of, approximately, l5s. 0d. per lineal yard of road. to repay this amount in thirty years at 4 per cent, would require a sum of 10.42d., say 10-1/2d. per annum; that is to say, the cost of taking the surface water into special 10-1/2 d. x 1000 sewers is ---------------= 5.6, say 6d. per 1,000 1875 gallons. if the sewage has to be pumped, the extra cost of pumping by reason of the increased quantity of surface water can be looked at from two different points of view:-1. the net cost of the gas or other fuel or electric current consumed in lifting the water. 2. the cost of the fuel consumed plus wages, stores, etc., and a proportion of the sum required to repay the capital cost of the pumping station and machinery. the extra cost of the sewers to carry the additional quantity of storm water might also be taken into account by working out and preparing estimates for the alternative schemes. the actual cost of the fuel may be taken at approximately 1/4 d. per 1,000 gallons. the annual works and capital charges, exclusive of fuel, should be divided by the normal quantity of sewage pumped per annum, rather than by the maximum quantity which the pumps would lift if they were able to run continuously during the whole time. for a town of about 10,000 inhabitants these charges may be taken at 1-1/4 d. per 1,000 gallons, which makes the total cost of pumping, inclusive of capital charges, 1-1/2 d. per 1,000 gallons. even if the extra cost of enlarging the sewers is added to this sum it will still be considerably below the sum of 6 d., which represents the cost of providing a separate system for the surface water. unless it is permissible for the sewage to have a free outlet to the sea at all states of the tide, the provision of effective storm overflows is a matter of supreme importance. not only is it necessary for them to be constructed in wellconsidered positions, but they must be effective in action. a weir constructed along one side of a manhole and parallel to the sewer is rarely efficient, as in times of storm the liquid in the sewer travels at a considerable velocity, and the greater portion of it, which should be diverted, rushes past the weir and continues to flow in the sewer; and if, as is frequently the case, it is desirable that the overflowing liquid should be screened, and vertical bars are fixed on the weir for the purpose, they block the outlet and render the overflow practically useless. leap weir overflows are theoretically most suitable for separating the excess flow during times of storm, but in practice they rarely prove satisfactory. this is not the fault of the system, but is, in the majority of the cases, if not all, due to defective designing. the general arrangement of a leap weir overflow is shown in fig. 17. in normal circumstances the sewage flowing along the pipe a falls down the ramp, and thence along the sewer b; when the flow is increased during storms the sewage from a shoots out from the end of the pipe into the trough c, and thence along the storm-water sewer d. in order that it should be effective the first step is to ascertain accurately the gradient of the sewer above the proposed overflow, then, the size being known, it is easy to calculate the velocity of flow for the varying depths of sewage corresponding with minimum flow, average dry weather flow, maximum dry weather flow, and six times the dry weather flow. the natural curve which the sewage would follow in its downward path as it flowed out from the end of the sewer can then be drawn out for the various depths, taking into account the fact that the velocity at the invert and sides of the sewer is less than the average velocity of flow. the ramp should be built in accordance with the calculated curves so as to avoid splashing as far as possible, and the level of the trough c fixed so that when it is placed sufficiently far from a to allow the dry weather flow to pass down the ramp it will at the same time catch the storm water when the required dilution has taken place. due regard must be had to the altered circumstances which will arise when the growth of population occurs, for which provision is made in the scheme, so that the overflow will remain efficient. the trough c is movable, so that the width of the leap weir may be adjusted from time to time as required. the overflow should be frequently inspected, and the accumulated rubbish removed from the trough, because sticks and similar matters brought down by the sewer will probably leap the weir instead of flowing down the ramp with the sewage. it is undesirable to fix a screen in conjunction with this overflow, but if screening is essential the operation should be carried out in a special manhole built lower down the course of the storm-water sewer. considerable wear takes place on the ramp, which should, therefore, be constructed of blue staffordshire or other hard bricks. the ramp should terminate in a stone block to resist the impact of the falling water, and the stones which may be brought with it, which would crack stoneware pipes if such were used. in cases where it is not convenient to arrange a sudden drop in the invert of the sewer as is required for a leap weir overflow, the excess flow of storm-water may be diverted by an arrangement similar to that shown in fig. 18. [footnote: plate iv] in this case calculations must be made to ascertain the depth at which the sewage will flow in the pipes at the time it is diluted to the required extent; this gives the level of the lip of the diverting plate. the ordinary sewage flow will pass steadily along the invert of the sewer under the plate until it rises up to that height, when the opening becomes a submerged orifice, and its discharging capacity becomes less than when the sewage was flowing freely. this restricts the flow of the sewage, and causes it to head up on the upper side of the overflow in an endeavour to force through the orifice the same quantity as is flowing in the sewer, but as it rises the velocity carries the upper layer of the water forward up the diverting plate and thence into the storm overflow drain a deep channel is desirable, so as to govern the direction of flow at the time the overflow is in action. the diverting trough is movable, and its height above the invert can be increased easily, as may be necessary from time to time. with this arrangement the storm-water can easily be screened before it is allowed to pass out by fixing an inclined screen in the position shown in fig. 18. [footnote: plate iv] it is loose, as is the trough, and both can be lifted out when it is desired to have access to the invert of the sewer. the screen is selfcleansing, as any floating matter which may be washed against it does not stop on it and reduce its discharging capacity, but is gradually drawn down by the flow of the sewage towards the diverting plate under which it will be carried. the heavier matter in the sewage which flows along the invert will pass under the plate and be carried through to the outfall works, instead of escaping by the overflow, and perhaps creating a nuisance at that point. chapter ix. wind and windmills. in small sewerage schemes where pumping is necessary the amount expended in the wages of an attendant who must give his whole attention to the pumping station is so much in excess of the cost of power and the sum required for the repayment of the loan for the plant and buildings that it is desirable for the economical working of the scheme to curtail the wages bill as far as possible. if oil or gas engines are employed the man cannot be absent for many minutes together while the machinery is running, and when it is not running, as for instance during the night, he must be prepared to start the pumps at very short notice, should a heavy rain storm increase the flow in the sewers to such an extent that the pump well or storage tank becomes filled up. it is a simple matter to arrange floats whereby the pump may be connected to or disconnected from a running engine by means of a friction clutch, so that when the level of the sewage in the pump well reaches the highest point desired the pump may be started, and when it is lowered to a predetermined low water level the pump will stop; but it is impracticable to control the engine in the same way, so that although the floats are a useful accessory to the plant during the temporary absence of the man in charge they will not obviate his more or less constant attendance. an electric motor may be controlled by a float, but in many cases trouble is experienced with the switch gear, probably caused by its exposure to the damp air. in all cases an alarm float should be fixed, which would rise as the depth of the sewage in the pump well increased, until the top water level was reached, when the float would make an electrical contact and start a continuous ringing warning bell, which could be placed either at the pumping station or at the man's residence. on hearing the bell the man would know the pump well was full, and that he must immediately repair to the pumping-station and start the pumps, otherwise the building would be flooded. if compressed air is available a hooter could be fixed, which would be heard for a considerable distance from the station. [illustration: plate iv. "diverting plate" overflow. to face page 66.] it is apparent, therefore, that a pumping machine is wanted which will work continuously without attention, and will not waste money when there is nothing to pump. there are two sources of power in nature which might be harnessed to give this result--water and wind. the use of water on such a small scale is rarely economically practicable, as even if the water is available in the vicinity of the pumping-station, considerable work has generally to be executed at the point of supply, not only to store the water in sufficient bulk at such a level that it can be usefully employed, but also to lead it to the power-house, and then to provide for its escape after it has done its work. the power-house, with its turbines and other machinery, involves a comparatively large outlay, but if the pump can be directly driven from the turbines, so that the cost of attendance is reduced to a minimum, the system should certainly receive consideration. although the wind is always available in every district, it is more frequent and powerful on the coast than inland. the velocity of the wind is ever varying within wide limits, and although the records usually give the average hourly velocity, it is not constant even for one minute. windmills of the modern type, consisting of a wheel composed of a number of short sails fixed to a steel framework upon a braced steel tower, have been used for many years for driving machinery on farms, and less frequently for pumping water for domestic use. in a very few cases it has been utilised for pumping sewage, but there is no reason why, under proper conditions, it should not be employed to a greater extent. the reliability of the wind for pumping purposes may be gauged from the figures in the following table, no. 11, which were observed in birmingham, and comprise a period of ten years; they are arranged in order corresponding with the magnitude of the annual rainfall:-table no. 11. mean hourly velocity of wind reference | rainfall |number of days in year during which the mean | number | for |hourly velocity of the wind was below | | year | 6 m.p.h. | 10 m.p.h. | 15 m.p.h. | 20 m.p.h. | ----------+----------+----------+-----------+-----------+-----------+ 1... 33·86 16 88 220 314 2... 29·12 15 120 260 334 3... 28·86 39 133 263 336 4... 26·56 36 126 247 323 5... 26·51 34 149 258 330 6... 26·02 34 132 262 333 7... 25·16 33 151 276 332 8... 22·67 46 155 272 329 9... 22·30 26 130 253 337 10... 21·94 37 133 276 330 ----------+----------+----------+-----------+-----------+-----------+ average 31·4 131·7 250·7 330·8 it may be of interest to examine the monthly figures for the two years included in the foregoing table, which had the least and the most wind respectively, such figures being set out in the following table: table no. 12 monthly analysis of wind number of days in each month during which the mean velocity of the wind was respectively below the value mentioned hereunder. month | year of least wind (no. 8) | year of most wind (no. *8*) | | 5 10 15 20 | 5 10 15 20 | | m.p.h. m.p.h. m.p.h. m.p.h. | m.p.h. m.p.h. m.p.h. m.p.h. | ------+-------+-----+-------+-------+-------+------+------+-------+ jan. 5 11 23 27 3 6 15 23 feb. 5 19 23 28 0 2 8 16 mar. 5 10 20 23 0 1 11 18 april 6 16 23 28 1 7 16 26 may 1 14 24 30 3 11 24 31 june 1 12 22 26 1 10 21 27 july 8 18 29 31 1 12 25 29 aug. 2 9 23 30 1 9 18 30 sept. 1 13 25 30 1 12 24 28 oct. 5 17 21 26 0 4 16 29 nov. 6 11 20 26 3 7 19 28 dec. 1 5 19 24 2 7 23 29 ------+-------+-----+-------+-------+-------+------+------+-------+ total 46 155 272 329 16 88 220 314 during the year of least wind there were only eight separate occasions upon which the average hourly velocity of the wind was less than six miles per hour for two consecutive days, and on two occasions only was it less than six miles per hour on three consecutive days. it must be remembered, however, that this does not by any means imply that during such days the wind did not rise above six miles per hour, and the probability is that a mill which could be actuated by a six-mile wind would have been at work during part of the time. it will further be observed that the greatest differences between these two years occur in the figures relating to the light winds. the number of days upon which the mean hourly velocity of the wind exceeds twenty miles per hour remains fairly constant year after year. as the greatest difficulty in connection with pumping sewage is the influx of storm water in times of rain, it will be useful to notice the rainfall at those times when the wind is at a minimum. from the following figures (table no. 13) it will be seen that, generally speaking, when there is very little wind there is very little rain taking the ten years enumerated in table no. 11, we find that out of the 314 days on which the wind averaged less than six miles per hour only forty-eight of them were wet, and then the rainfall only averaged .l3 in on those days. table no. 13. wind less than 6 m.p.h. -----------+-------------+------------+--------+--------------------------------- ref. no. | total no. | days on | | rainfall on each from table | of days in | which no | rainy | rainy day in no. 11. | each year. | rain fell. | days. | inches. -----------+-------------+------------+--------+--------------------------------- 1 | 16 | 14 | 2 | .63 and .245 2 | 15 | 13 | 2 | .02 and .02 3 | 39 | 34 | 5 | .025, .01, .26, .02 and .03 4 | 36 | 29 | 7 | / .02, .08, .135, .10, .345, .18 | | | | \ and .02 5 | 34 | 28 | 6 | .10, .43, .01, .07, .175 and .07 6 | 32 | 27 | 5 | .10, .11, .085, .04 and .135 7 | 33 | 21 | 2 | .415 and .70 8 | 46 | 40 | 6 | .07, .035, .02, .06, .13 and .02 9 | 26 | 20 | 6 | .145, .20, .33, .125, .015 & .075 10 | 37 | 30 | 7 | / .03, .23, .165, .02, .095 | | | | \ .045 and .02 -----------+-------------+------------+--------+---------------------------------total | 314 | 266 | 48 | average rainfall on each of | | | | the 48 days = .13 in the greater the height of the tower which carries the mill the greater will be the amount of effective wind obtained to drive the mill, but at the same time there are practical considerations which limit the height. in america many towers are as much as 100 ft high, but ordinary workmen do not voluntarily climb to such a height, with the result that the mill is not properly oiled. about 40 ft is the usual height in this country, and 60 ft should be used as a maximum. mr. george phelps, in a paper read by him in 1906 before the association of water engineers, stated that it was safe to assume that on an average a fifteen miles per hour wind was available for eight hours per day, and from this he gave the following figures as representing the approximate average duty with, a lift of l00 ft, including friction:-table no. 14 duty of wintdmilu diameter of wheel. 10 12 14 16 18 20 25 30 35 40 the following table gives the result of tests carried out by the united states department of agriculture at cheyenne, wyo., with a l4 ft diameter windmill under differing wind velocities:-table no. 15. power or l4-rx windmill in varying winds. velocity of wind (miles per hour). 0--5 6-10 11-15 16-20 21-25 26-30 31-35 it will be apparent from the foregoing figures that practically the whole of the pumping for a small sewerage works may be done by means of a windmill, but it is undesirable to rely entirely upon such a system, even if two mills are erected so that the plant will be in duplicate, because there is always the possibility, although it may be remote, of a lengthened period of calm, when the sewage would accumulate; and, further, the local government board would not approve the scheme unless it included an engine, driven by gas, oil, or other mechanical power, for emergencies. in the case of water supply the difficulty may be overcome by providing large storage capacity, but this cannot be done for sewage without creating an intolerable nuisance. in the latter case the storage should not be less than twelve hours dry weather flow, nor more than twenty-four. with a well-designed mill, as has already been indicated, the wind will, for the greater part of the year, be sufficient to lift the whole of the sewage and storm-water, but, if it is allowed to do so, the standby engine will deteriorate for want of use to such an extent that when urgently needed it will not be effective. it is, therefore, desirable that the attendant should run the engine at least once in every three days to keep it in working order. if it can be conveniently arranged, it is a good plan for the attendant to run the engine for a few minutes to entirely empty the pump well about six o'clock each evening. the bulk of the day's sewage will then have been delivered, and can be disposed of when it is fresh, while at the same time the whole storage capacity is available for the night flow, and any rainfall which may occur, thus reducing the chances of the man being called up during the night. about 22 per cent, of the total daily dry weather flow of sewage is delivered between 7 p.m. and 7 a.m. the first cost of installing a small windmill is practically the same as for an equivalent gas or oil engine plant, so that the only advantage to be looked for will be in the maintenance, which in the case of a windmill is a very small matter, and the saving which may be obtained by the reduction of the amount of attendance necessary. generally speaking, a mill 20 ft in diameter is the largest which should be used, as when this size is exceeded it will be found that the capital cost involved is incompatible with the value of the work done by the mill, as compared with that done by a modern internal combustion engine. mills smaller than 8 ft in diameter are rarely employed, and then only for small work, such as a 2 1/2 in pump and a 3-ft lift the efficiency of a windmill, measured by the number of square feet of annular sail area, decreases with the size of the mill, the 8 ft, 10 ft, and l2 ft mills being the most efficient sizes. when the diameter exceeds l2 ft, the efficiency rapidly falls off, because the peripheral velocity remains constant for any particular velocity or pressure of the wind, and as every foot increase in the diameter of the wheel makes an increase of over 3 ft in the length of the circumference, the greater the diameter the less the number of revolutions in any given time; and consequently the kinetic flywheel action which is so valuable in the smaller sizes is to a great extent lost in the larger mills. any type of pump can be used, but the greatest efficiency will be obtained by adopting a single acting pump with a short stroke, thus avoiding the liability, inherent in a long pump rod, to buckle under compression, and obviating the use of a large number of guides which absorb a large part of the power given out by the mill. although some of the older mills in this country are of foreign origin, there are several british manufacturers turning out well-designed and strongly-built machines in large numbers. fig. 19 represents the general appearance and fig. 20 the details of the type of mill made by the well-known firm of duke and ockenden, of ferry wharf, littlehampton, sussex. this firm has erected over 400 windmills, which, after the test of time, have proved thoroughly efficient. from fig. 20 it will be seen that the power applied by the wheel is transmitted through spur and pinion gearing of 2 1/2 ratio to a crank shaft, the gear wheel having internal annular teeth of the involute type, giving a greater number of teeth always in contact than is the case with external gears. this minimises wear, which is an important matter, as it is difficult to properly lubricate these appliances, and they are exposed to and have to work in all sorts of weather. [illustration: fig. l9.--general view of modern windmill.] [illustration: fig. 20.--details of windmill manufactured by messrs. duke and ockenden, littlehampton.] it will be seen that the strain on the crank shaft is taken by a bent crank which disposes the load centrally on the casting, and avoids an overhanging crank disc, which has been an objectionable feature in some other types. the position of the crank shaft relative to the rocker pin holes is studied to give a slow upward motion to the rocker with a more rapid downward stroke, the difference in speed being most marked in the longest stroke, where it is most required. in order to transmit the circular internal motion a vertical connecting rod in compression is used, which permits of a simple method of changing the length of stroke by merely altering the pin in the rocking lever, the result being that the pump rod travels in a vertical line. the governing is entirely automatic. if the pressure on the wind wheel, which it will be seen is set off the centre line of the mill and tower, exceeds that found desirable--and this can be regulated by means of a spring on the fantail--the windmill automatically turns on the turn-table and presents an ellipse to the wind instead of a circular face, thus decreasing the area exposed to the wind gradually until the wheel reaches its final position, or is hauled out of gear, when the edges only are opposed to the full force of the wind. the whole weight of the mill is taken upon a ball-bearing turn-table to facilitate instant "hunting" of the mill to the wind to enable it to take advantage of all changes of direction. the pump rod in the windmill tower is provided with a swivel coupling, enabling the mill head to turn completely round without altering the position of the rod. chapter x. the design of see outfalls. the detail design of a sea outfall will depend upon the level of the conduit with reference to present surface of the shore, whether the beach is being eroded or made up, and, if any part of the structure is to be constructed above the level of the shore, whether it is likely to be subject to serious attack by waves in times of heavy gales. if there is probability of the direction of currents being affected by the construction of a solid structure or of any serious scour being caused, the design must be prepared accordingly. while there are examples of outfalls constructed of glazed stoneware socketed pipes surrounded with concrete, as shown in fig. 21, cast iron pipes are used in the majority of cases. there is considerable variation in the design of the joints for the latter class of pipes, some of which are shown in figs. 22, 23, and 24. spigot and socket joints (fig. 22), with lead run in, or even with rod lead or any of the patent forms caulked in cold, are unsuitable for use below high-water mark on account of the water which will most probably be found in the trench. pipes having plain turned and bored joints are liable to be displaced if exposed to the action of the waves, but if such joints are also flanged, as fig. 24, or provided with lugs, as fig. 23, great rigidity is obtained when they are bolted up; in addition to which the joints are easily made watertight. when a flange is formed all round the joint, it is necessary, in order that its thickness may be kept within reasonable limits, to provide bolts at frequent intervals. a gusset piece to stiffen the flange should be formed between each hole and the next, and the bolt holes should be arranged so that when the pipes are laid there will not be a hole at the bottom on the vertical axis of the pipe, as when the pipes are laid in a trench below water level it is not only difficult to insert the bolt, but almost impracticable to tighten up the nut afterwards. the pipes should be laid so that the two lowest bolt holes are placed equidistant on each side of the centre line, as shown in the end views of figs. nos. 23 and 24. [illustration: fig. 2l.-stoneware pipe and concrete sea outfall.] with lug pipes, fewer bolts are used, and the lugs are made specially strong to withstand the strain put upon them in bolting up the pipes. these pipes are easier and quicker to joint under water than are the flanged pipes, so that their use is a distinct advantage when the hours of working are limited. in some cases gun-metal bolts are used, as they resist the action of sea water better than steel, but they add considerably to the cost of the outfall sewer, and the principal advantage appears to be that they are possibly easier to remove than iron or steel ones would be if at any time it was required to take out any pipe which may have been accidentally broken. on the other hand, there is a liability of severe corrosion of the metal taking place by reason of galvanic action between the gun-metal and the iron, set up by the sea water in which they are immersed. if the pipes are not to be covered with concrete, and are thus exposed to the action of the sea water, particular care should be taken to see that the coating by dr. angus smith's process is perfectly applied to them. [illustration: fig. 22.--spigot and socket joint for cast iron pipes.] [illustration: fig. 23.--lug joint for cast iron pipes.] [illustration: fig. 24.--turned, board, and flanged joint for cast iron pipes.] steel pipes are, on the whole, not so suitable as cast iron. they are, of course, obtainable in long lengths and are easily jointed, but their lightness compared with cast iron pipes, which is their great advantage in transport, is a disadvantage in a sea outfall, where the weight of the structure adds to its stability. the extra length of steel pipes necessitates a greater extent of trench being excavated at one time, which must be well timbered to prevent the sides falling in on the other hand, cast iron pipes are more liable to fracture by heavy stones being thrown upon them by the waves, but this is a contingency which does not frequently occur in practice. according to trautwine, the cast iron for pipes to resist sea water should be close-grained, hard, white metal. in such metal the small quantity of contained carbon is chemically combined with the iron, but in the darker or mottled metals it is mechanically combined, and such iron soon becomes soft, like plumbago, under the influence of sea water. hard white iron has been proved to resist sea water for forty years without deterioration, whether it is continually under water or alternately wet and dry. several types of sea outfalls are shown in figs. 25 to 31.[1] in the example shown in fig. 25 a solid rock bed occurred a short distance below the sand, which was excavated so as to allow the outfall to be constructed on the rock. anchor bolts with clevis heads were fixed into the rock, and then, after a portion of the concrete was laid, iron bands, passing around the cast iron pipes, were fastened to the anchors. this construction would not be suitable below low-water mark. fig. 26 represents the aberdeen sea outfall, consisting of cast iron pipes 7 ft in diameter, which are embedded in a heavy concrete breakwater 24 ft in width, except at the extreme end, where it is 30 ft wide. the 4 in wrought iron rods are only used to the last few pipes, which were in 6 ft lengths instead of 9 ft, as were the remainder. fig. 27 shows an inexpensive method of carrying small pipes, the slotted holes in the head of the pile allowing the pipes to be laid in a straight line, even if the pile is not driven quite true, and if the level of the latter is not correct it can be adjusted by inserting a packing piece between the cradle and the head. great crosby outfall sewer into the mersey is illustrated in fig. 28. the piles are of greenheart, and were driven to a solid foundation. the 1 3/4 in sheeting was driven to support the sides of the excavation, and was left in when the concrete was laid. light steel rails were laid under the sewer, in continuous lengths, on steel sleepers and to 2 ft gauge. the invert blocks were of concrete, and the pipes were made of the same material, but were reinforced with steel ribs. the waterloo (near liverpool) sea outfall is shown in fig. 31. [footnote 1: plate v.] piling may be necessary either to support the pipes or to keep them secure in their proper position, but where there is a substratum of rock the pipes may be anchored, as shown in figs. 25 and 26. the nature of the piling to be adopted will vary according to the character of the beach. figs. 27, 29, 30, and 31 show various types. with steel piling and bearers, as shown in fig. 29, it is generally difficult to drive the piles with such accuracy that the bearers may be easily bolted up through the holes provided in the piles, and, if the holes are not drilled in the piles until after they are driven to their final position, considerable time is occupied, and perhaps a tide lost in the attempt to drill them below water. there is also the difficulty of tightening up the bolts when the sewer is partly below the surface of the shore, as shown. in both the types shown in figs. 29 and 30 it is essential that the piles and the bearers should abut closely against the pipes; otherwise the shock of the waves will cause the pipes to move and hammer against the framing, and thus lead to failure of the structure. piles similar to fig. 31 can only be fixed in sand, as was the case at waterloo, because they must be absolutely true to line and level, otherwise the pipes cannot be laid in the cradles. the method of fixing these piles is described by mr. ben howarth (minutes of proceedings of inst.c.e., vol. clxxv.) as follows:--"the pile was slung vertically into position from a four-legged derrick, two legs of which were on each side of the trench; a small winch attached to one pair of the legs lifted and lowered the pile, through a block and tackle. when the pile was ready to be sunk, a 2 in iron pipe was let down the centre, and coupled to a force-pump by means of a hose; a jet of water was then forced down this pipe, driving the sand and silt away from below the pile. the pile was then rotated backwards and forwards about a quarter of a turn, by men pulling on the arms; the pile, of course, sank by its own weight, the water-jet driving the sand up through the hollow centre and into the trench, and it was always kept vertical by the sling from the derrick. as soon as the pile was down to its final level the ground was filled in round the arms, and in this running sand the pile became perfectly fast and immovable a few minutes after the sinking was completed. the whole process, from the first slinging of the pile to the final setting, did not take more than 20 or 25 minutes." [illustration: plate v. rock bed. fig. 26--aberdeen sea outfall. fig. 27--small great crosby sea outfall. fig. 29--cast iron pipe on steel cast and bearers. fig. 31--waterloo (liverpool) sea outfall.] (_to face page 80_.) screw piles may be used if the ground is suitable, but, if it is boulder clay or similar material, the best results will probably be obtained by employing rolled steel joists as piles. chapter xi. the action of sea water on cement. questions are frequently raised in connection with sea-coast works as to whether any deleterious effect will result from using sea-water for mixing the concrete or from using sand and shingle off the beach; and, further, whether the concrete, after it is mixed, will withstand the action of the elements, exposed, as it will be, to air and sea-water, rain, hot sun, and frosts. some concrete structures have failed by decay of the material, principally between high and low water mark, and in order to ascertain the probable causes and to learn the precautions which it is necessary to take, some elaborate experiments have been carried out. to appreciate the chemical actions which may occur, it will be as well to examine analyses of sea-water and cement. the water of the irish channel is composed of sodium chloride.................... 2.6439 per cent. magnesium chloride................. 0.3150 " " magnesium sulphate................. 0.2066 " " calcium sulphate................... 0.1331 " " potassium chloride................. 0.0746 " " magnesium bromide.................. 0.0070 " " calcium carbonate.................. 0.0047 " " iron carbonate..................... 0.0005 " " magnesium nitrate.................. 0.0002 " " lithium chloride................... traces. ammonium chloride.................. traces. silica chloride.................... traces. water.............................. 96.6144 ------- 100.0000 an average analysis of a thames cement may be taken to be as follows:-silica................................ 23.54 per cent. insoluble residue (sand, clay, etc.)............................ 0.40 " alumina and ferric oxide............... 9.86 " lime.................................. 62.08 " magnesia............................... 1.20 " sulphuric anhydride.................... 1.08 " carbonic anhydride and water........... 1.34 " alkalies and loss on analysis.......... 0.50 " ---- 100.00 the following figures give the analysis of a sample of cement expressed in terms of the complex compounds that are found:-sodium silicate (na2sio3)........ 3.43 per cent. calcium sulphate (caso4)......... 2.45 " dicalcium silicate (ca2sio4).... 61.89 " dicalcium aluminate (ca2al2o5).. 12.14 " dicalcium ferrate (ca2fe2o5)..... 4.35 " magnesium oxide (mgo)............ 0.97 " calcium oxide (cao)............. 14.22 " loss on analysis, &c............. 0.55 " ---- 100.00 dr. w. michaelis, the german cement specialist, gave much consideration to this matter in 1906, and formed the opinion that the free lime in the portland cement, or the lime freed in hardening, combines with the sulphuric acid of the sea-water, which causes the mortar or cement to expand, resulting in its destruction. he proposed to neutralise this action by adding to the mortar materials rich in silica, such as trass, which would combine with the lime. mr. j. m. o'hara, of the southern pacific laboratory, san francisco, cal., made a series of tests with sets of pats 4 in diameter and 1/2 in thick at the centre, tapering to a thin edge on the circumference, and also with briquettes for ascertaining the tensile strength, all of which were placed in water twenty-four hours after mixing. at first some of the pats were immersed in a "five-strength solution" of sea-water having a chemical analysis as follows:-sodium chloride.................... 11.5 per cent. magnesium chloride................. 1.4 " " magnesium sulphate................. 0.9 " " calcium sulphate................... 0.6 " " water.............................. 85.6 " " 100.0 this strong solution was employed in order that the probable effect of immersing the cement in sea-water might be ascertained very much quicker than could be done by observing samples actually placed in ordinary sea-water, and it is worthy of note that the various mixtures which failed in this accelerated test also subsequently failed in ordinary sea-water within a period of twelve months. strong solutions were next made of the individual salts contained in sea-water, and pats were immersed as before, when it was found that the magnesium sulphate present in the water acted upon the calcium hydrate in the cement, forming calcium sulphate, and leaving the magnesium hydrate free. the calcium sulphate combines with the alumina of the cement, forming calcium sulpho-aluminate, which causes swelling and cracking of the concrete, and in cements containing a high proportion of alumina, leads to total destruction of all cohesion. the magnesium hydrate has a tendency to fill the pores of the concrete so as to make it more impervious to the destructive action of the sea-water, and disintegration may be retarded or checked. a high proportion of magnesia has been found in samples of cement which have failed under the action of sea water, but the disastrous result cannot be attributed to this substance having been in excess in the original cement, as it was probably due to the deposition of the magnesia salts from the sea-water; although, if magnesia were present in the cement in large quantities, it would cause it to expand and crack, still with the small proportion in which it occurs in ordinary cements it is probably inert. the setting of cement under the action of water always frees a portion of the lime which was combined, but over twice as much is freed when the cement sets in sea-water as in fresh water. the setting qualities of cement are due to the iron and alumina combined with calcium, so that for sea-coast work it is desirable for the alumina to be replaced by iron as far as possible. the final hardening and strength of cement is due in a great degree to the tri-calcium silicate (3cao, sio2) which is soluble by the sodium chloride found in sea-water, so that the resultant effect of the action of these two compounds is to enable the sea-water to gradually penetrate the mortar and rot the concrete. the concrete is softened, when there is an abnormal amount of sulphuric acid present, as a result of the reaction of the sulphuric acid of the salt dissolved by the water upon a part of the lime in the cement. the ferric oxide of the cement is unaffected by seawater. the neat cement briquette tests showed that those immersed in sea-water attained a high degree of strength at a much quicker rate than those immersed in fresh water, but the 1 to 3 cement and sand briquette tests gave an opposite result. at the end of twelve months, however, practically all the cements set in fresh water showed greater strength than those set in seawater. when briquettes which have been immersed in fresh water and have thoroughly hardened are broken, the cores are found to be quite dry, and if briquettes immersed in sea-water show a similar dryness there need be no hesitation in using the cement; but if, on the other hand, the briquette shows that the sea-water has permeated to the interior, the cement will lose strength by rotting until it has no cohesion at all. it must be remembered that it is only necessary for the water to penetrate to a depth of 1/2 in on each side of a briquette to render it damp all through, whereas in practical work, if the water only penetrated to the same depth, very little ill-effect would be experienced, although by successive removals of a skin 1/2 in deep the structure might in time be imperilled. the average strength in pounds per square inch of six different well-known brands of cement tested by mr. o'hara was as follows:-table no. 16. effect of sea water on strength of cement. neat cement 1 cement to 3 sand set in set in sea water fresh water sea water fresh water 7 days 682 548 214 224 28 days 836 643 293 319 2 months 913 668 313 359 3 months 861 667 301 387 6 months 634 654 309 428 9 months 542 687 317 417 12 months 372 706 325 432 some tests were also made by messrs. westinghouse, church, kerr, and co., of new york, to ascertain the effect of seawater on the tensile strength of cement mortar. three sets of briquettes were made, having a minimum section of one square inch. the first were mixed with fresh water and kept in fresh water; the second were mixed with fresh water, but kept immersed in pans containing salt water; while the third were mixed with sea-water and kept in sea-water. in the experiments the proportion of cement and sand varied from 1 to 1 to 1 to 6. the results of the tests on the stronger mixtures are shown in fig. 32. the scandinavian portland cement manufacturers have in hand tests on cubes of cement mortar and cement concrete, which were started in 1896, and are to extend over a period of twenty years. a report upon the tests of the first ten years was submitted at the end of 1909 to the international association of testing materials at copenhagen, and particulars of them are published in "cement and sea-water," by a. poulsen (chairman of the committee), j. jorsen and co., copenhagen, 1909, price 3s. [illustration: fig. 32.--tests of the tensile strength of cement and sand briquettes, showing the effect of sea water.] cements from representative firms in different countries were obtained for use in making the blocks, which had coloured glass beads and coloured crushed glass incorporated to facilitate identification. each block of concrete was provided with a number plate and a lifting bolt, and was kept moist for one month before being placed in position. the sand and gravel were obtained from the beach on the west coast of jutland. the mortar blocks were mixed in the proportion of 1 to 1, 1 to 2, and 1 to 3, and were placed in various positions, some between high and low water, so as to be exposed twice in every twentyfour hours, and others below low water, so as to be always submerged. the blocks were also deposited under these conditions in various localities, the mortar ones being placed at esbjerb at the south of denmark, at vardo in the arctic ocean, and at degerhamm on the baltic, where the water is only one-seventh as salt as the north sea, while the concrete blocks were built up in the form of a breakwater or groyne at thyboron on the west coast of jutland. at intervals of three, six, and twelve months, and two, four, six, ten, and twenty years, some of the blocks have, or will be, taken up and subjected to chemical tests, the material being also examined to ascertain the effect of exposure upon them. the blocks tested at intervals of less than one year after being placed in position gave very variable results, and the tests were not of much value. the mortar blocks between high and low water mark of the arctic ocean at vardo suffered the worst, and only those made with the strongest mixture of cement, 1 to 1, withstood the severe frost experienced. the best results were obtained when the mortar was made compact, as such a mixture only allowed diffusion to take place so slowly that its effect was negligible; but when, on the other hand, the mortar was loose, the salts rapidly penetrated to the interior of the mass, where chemical changes took place, and caused it to disintegrate. the concrete blocks made with 1 to 3 mortar disintegrated in nearly every case, while the stronger ones remained in fairly good condition. the best results were given by concrete containing an excess of very fine sand. mixing very finely-ground silica, or trass, with the cement proved an advantage where a weak mixture was employed, but in the other cases no benefit was observed. the association of german portland cement manufacturers carried out a series of tests, extending over ten years, at their testing station at gross lichterfeld, near berlin, the results of which were tabulated by mr. c. schneider and professor gary. in these tests the mortar blocks were made 3 in cube and the concrete blocks l2 in cube; they were deposited in two tanks, one containing fresh water and the other sea-water, so that the effect under both conditions might be noted. in addition, concrete blocks were made, allowed to remain in moist sand for three months, and were then placed in the form of a groyne in the sea between high and low-water mark. some of the blocks were allowed to harden for twelve months in sand before being placed, and these gave better results than the others. two brands of german portland cement were used in these tests, one, from which the best results were obtained, containing 65.9 per cent. of lime, and the other 62.0 per cent. of lime, together with a high percentage of alumina. in this case, also, the addition of finely-ground silica, or trass, improved the resisting power of blocks made with poor mortars, but did not have any appreciable effect on the stronger mixtures. professor m. möller, of brunswick, germany, reported to the international association for testing materials, at the copenhagen congress previously referred to, the result of his tests on a small hollow, trapezium shape, reinforced concrete structure, which was erected in the north sea, the interior being filled with sandy mud, which would be easily removable by flowing water. the sides were 7 cm. thick, formed of cement concrete 1:2 1/2:2, moulded elsewhere, and placed in the structure forty days after they were made, while the top and bottom were 5 cm. thick, and consisted of concrete 1:3:3, moulded _in situ_ and covered by the tide within twenty-four hours of being laid. the concrete moulded _in situ_ hardened a little at first, and then became soft when damp, and friable when dry, and white efflorescence appeared on the surface. in a short time the waves broke this concrete away, and exposed the reinforcement, which rusted and disappeared, with the result that in less than four years holes were made right through the concrete. the sides, which were formed of slabs allowed to harden before being placed in the structure, were unaffected except for a slight roughening of the surface after being exposed alternately to the sea and air for a period, of thirteen years. professor möller referred also to several cases which had come under his notice where cement mortar or concrete became soft and showed white efflorescence when it had been brought into contact with sea-water shortly after being made. in experiments in atlantic city samples of dry cement in powder form were put with sea-water in a vessel which was rapidly rotated for a short time, after which the cement and the seawater were analysed, and it was found that the sea-water had taken up the lime from the cement, and the cement had absorbed the magnesia salts from the sea-water. some tests were carried out in 1908-9 at the navy yard, charlestown, mass., by the aberthaw construction company of boston, in conjunction with the navy department. the cement concrete was placed so that the lower portions of the surfaces of the specimens were always below water, the upper portions were always exposed to the air, and the middle portions were alternately exposed to each. although the specimens were exposed to several months of winter frost as well as to the heat of the summer, no change was visible in any part of the concrete at the end of six months. mons. r. feret, chief of the laboratory of bridges and roads, boulogne-sur-mer, france, has given expression to the following opinions:-1. no cement or other hydraulic product has yet been found which presents absolute security against the decomposing action of sea-water. 2. the most injurious compound of sea-water is the acid of the dissolved sulphates, sulphuric acid being the principal agent in the decomposition of cement. 3. portland cement for sea-water should be low in aluminium and as low as possible in lime. 4. puzzolanic material is a valuable addition to cement for sea-water construction, 5. as little gypsum as possible should be added for regulating the time of setting to cements which are to be used in seawater. 6. sand containing a large proportion of fine grains must never be used in concrete or mortar for sea-water construction. 7. the proportions of the cement and aggregate for sea-water construction must be such as will produce a dense and impervious concrete. on the whole, sea-water has very little chemical effect on good portland cements, such as are now easily obtainable, and, provided the proportion of aluminates is not too high, the varying composition of the several well-known commercial cements is of little moment. for this reason tests on blocks immersed in still salt water are of very little use in determining the probable behaviour of concrete when exposed to damage by physical and mechanical means, such as occurs in practical work. the destruction of concrete works on the sea coast is due to the alternate exposure to air and water, frost, and heat, and takes the form of cracking or scaling, the latter being the most usual when severe frosts are experienced. when concrete blocks are employed in the construction of works, they should be made as long as possible before they are required to be built in the structure, and allowed to harden in moist sand, or, if this is impracticable, the blocks should be kept in the air and thoroughly wetted each day. on placing cement or concrete blocks in sea water a white precipitate is formed on their surfaces, which shows that there is some slight chemical action, but if the mixture is dense this action is restricted to the outside, and does not harm the block. cement mixed with sea water takes longer to harden than if mixed with fresh water, the time varying in proportion to the amount of salinity in the water. sand and gravel from the beach, even though dry, have their surfaces covered with saline matters, which retard the setting of the cement, even when fresh water is used, as they become mixed with such water, and thus permeate the whole mass. if sea water and aggregate from the shore are used, care must be taken to see that no decaying seaweed or other organic matter is mixed with it, as every such piece will cause a weak place in the concrete. if loam, clay, or other earthy matters from the cliffs have fallen down on to the beach, the shingle must be washed before it is used in concrete. exposure to damp air, such as is unavoidable on the coast, considerably retards the setting of cement, so that it is desirable that it should not be further retarded by the addition of gypsum, or calcium sulphate, especially if it is to be used with sea water or sea-washed sand and gravel. the percentage of gypsum found in cement is, however, generally considerably below the maximum allowed by the british standard specification, viz., 2 per cent., and is so small that, for practical purposes, it makes very little difference in sea coast work, although of course, within reasonable limits, the quicker the cement sets the better. when cement is used to joint stoneware pipe sewers near the coast, allowance must be made for this retardation of the setting, and any internal water tests which may be specified to be applied must not be made until a longer period has elapsed after the laying of the pipes than would otherwise be necessary. a high proportion of aluminates tends to cause disintegration when exposed to sea water. the most appreciable change which takes place in a good sound cement after exposure to the sea is an increase in the chlorides, while a slight increase in the magnesia and the sulphates also takes place, so that the proportion of sulphates and magnesia in the cement should be kept fairly low. hydraulic lime exposed to the sea rapidly loses the lime and takes up magnesia and sulphates. to summarise the information upon this point, it appears that it is better to use fresh water for all purposes, but if, for the sake of economy, saline matters are introduced into the concrete, either by using sea water for mixing or by using sand and shingle from the beach, the principal effect will be to delay the time of setting to some extent, but the ultimate strength of the concrete will probably not be seriously affected. when the concrete is placed in position the portion most liable to be destroyed is that between high and low water mark, which is alternately exposed to the action of the sea and the air, but if the concrete has a well-graded aggregate, is densely mixed, and contains not more than two parts of sand to one part of cement, no ill-effect need be anticipated. chapter xii diving. the engineer is not directly concerned with the various methods employed in constructing a sea outfall, such matters being left to the discretion of the contractor. it may, however, be briefly stated that the work frequently involves the erection of temporary steel gantries, which must be very carefully designed and solidly built if they are to escape destruction by the heavy seas. it is amazing to observe the ease with which a rough sea will twist into most fantastic shapes steel joists 10 in by 8in, or even larger in size. any extra cost incurred in strengthening the gantries is well repaid if it avoids damage, because otherwise there is not only the expense of rebuilding the structure to be faced, but the construction of the work will be delayed possibly into another season. in order to ensure that the works below water are constructed in a substantial manner, it is absolutely necessary that the resident engineer, at least, should be able to don a diving dress and inspect the work personally. the particular points to which attention must be given include the proper laying of the pipes, so that the spigot of one is forced home into the socket of the other, the provision and tightening up of all the bolts required to be fixed, the proper driving of the piles and fixing the bracing, the dredging of a clear space in the bed of the sea in front of the outlet pipe, and other matters dependent upon the special form of construction adopted. if a plug is inserted in the open end of the pipes as laid, the rising of the tide will press on the plugged end and be of considerable assistance in pushing the pipes home; it will therefore be necessary to re-examine the joints to see if the bolts can be tightened up any more. messrs. siebe, gorman, and co., the well-known makers of submarine appliances, have fitted up at their works at westminster bridge-road, london, s.e., an experimental tank, in which engineers may make a few preliminary descents and be instructed in the art of diving; and it is distinctly more advantageous to acquire the knowledge in this way from experts than to depend solely upon the guidance of the divers engaged upon the work which the engineer desires to inspect. only a nominal charge of one guinea for two descents is made, which sum, less out-of-pocket expenses, is remitted to the benevolent fund of the institution of civil engineers. it is generally desirable that a complete outfit, including the air pump, should be provided for the sole use of the resident engineer, and special men should be told off to assist him in dressing and to attend to his wants while he is below water. he is then able to inspect the work while it is actually in progress, and he will not hinder or delay the divers. it is a wise precaution to be medically examined before undertaking diving work, although, with the short time which will generally be spent below water, and the shallow depths usual in this class of work, there is practically no danger; but, generally speaking, a diver should be of good physique, not unduly stout, free from heart or lung trouble and varicose veins, and should not drink or smoke to excess. it is necessary, however, to have acquaintance with the physical principles involved, and to know what to do in emergencies. a considerable amount of useful information is given by mr. r. h. davis in his "diving manual" (siebe, gorman, and co., 5s.), from which many of the following notes are taken. a diving dress and equipment weighs about l75 lb, including a 40 lb lead weight carried by the diver on his chest, a similar weight on his back, and l6lb of lead on each boot. upon entering the water the superfluous air in the dress is driven out through the outlet valve in the helmet by the pressure of the water on the legs and body, and by the time the top of the diver's head reaches the surface his breathing becomes laboured, because the pressure of air in his lungs equals the atmospheric pressure, while the pressure upon his chest and abdomen is greater by the weight of the water thereon. he is thus breathing against a pressure, and if he has to breathe deeply, as during exertion, the effect becomes serious; so that the first thing he has to learn is to adjust the pressure of the spring on the outlet valve, so that the amount of air pumped in under pressure and retained in the diving dress counterbalances the pressure of the water outside, which is equal to a little under 1/2lb per square inch for every foot in depth. if the diver be 6 ft tall, and stands in an upright position, the pressure on his helmet will be about 3lb per square inch less than on his boots. the breathing is easier if the dress is kept inflated down to the abdomen, but in this case there is danger of the diver being capsized and floating feet upwards, in which position he is helpless, and the air cannot escape by the outlet valve. air is supplied to the diver under pressure by an air pump through a flexible tube called the air pipe; and a light rope called a life line, which is used for signalling, connects the man with the surface. the descent is made by a 3 in "shot-rope," which has a heavy sinker weighing about 50 lb attached, and is previously lowered to the bottom. a 1-1/4 in rope about 15 ft long, called a "distanceline," is attached to the shot-rope about 3 ft above the sinker, and on reaching the bottom the diver takes this line with him to enable him to find his way back to the shot-rope, and thus reach the surface comfortably, instead of being hauled up by his life line. the diver must be careful in his movements that he does not fall so as suddenly to increase the depth of water in which he is immersed, because at the normal higher level the air pressure in the dress will be properly balanced against the water pressure; but if he falls, say 30 ft, the pressure of the water on his body will be increased by about 15 lb per square inch, and as the air pump cannot immediately increase the pressure in the dress to a corresponding extent, the man's body in the unresisting dress will be forced into the rigid helmet, and he will certainly be severely injured, and perhaps even killed. when descending under water the air pressure in the dress is increased, and acts upon the outside of the drum of the ear, causing pain, until the air passing through the nose and up the eustachian tube inside the head reaches the back of the drum and balances the pressure. this may be delayed, or prevented, if the tube is partially stopped up by reason of a cold or other cause, but the balance can generally be brought about if the diver pauses in his descent and swallows his saliva; or blocks up his nose as much as possible by pressing it against the front of the helmet, closing the mouth and then making a strong effort at expiration so as to produce temporarily an extra pressure inside the throat, and so blow open the tubes; or by yawning or going through the motions thereof. if this does not act he must come up again provided his ears are "open," and the air pumps can keep the pressure of air equal to that of the depth of the water in which the diver may be, there is nothing to limit the rate of his descent. now in breathing, carbonic acid gas is exhaled, the quality varying in accordance with the amount of work done, from .014 cubic feet per minute when at rest to a maximum of about .045, and this gas must be removed by dilution with fresh air so as not to inconvenience the diver. this is not a matter of much difficulty as the proportion in fresh air is about .03 per cent., and no effect is felt until the proportion is increased to about 0.3 per cent., which causes one to breathe twice as deeply as usual; at 0.6 per cent. there is severe panting; and at a little over 1.0 per cent. unconsciousness occurs. the effect of the carbonic acid on the diver, however, increases the deeper he descends; and at a depth of 33 ft 1 per cent. of carbonic acid will have the same effect as 2 per cent. at the surface. if the diver feels bad while under water he should signal for more air, stop moving about, and rest quietly for a minute or two, when the fresh air will revive him. the volume of air required by the diver for respiration is about 1.5 cubic feet per minute, and there is a non-return valve on the air inlet, so that in the event of the air pipe being broken, or the pump failing, the air would not escape backwards, but by closing the outlet valve the diver could retain sufficient air to enable him to reach the surface. during the time that a diver is under pressure nitrogen gas from the air is absorbed by his blood and the tissues of his body. this does not inconvenience him at the time, but when he rises the gas is given off, so that if he has been at a great depth for some considerable time, and comes up quickly, bubbles form in the blood and fill the right side of the heart with air, causing death in a few minutes. in less sudden cases the bubbles form in the brain or spinal cord, causing paralysis of the legs, which is called divers' palsy, or the only trouble which is experienced may be severe pains in the joints and muscles. it is necessary, therefore, that he shall come up by stages so as to decompress himself gradually and avoid danger. the blood can hold about twice as much gas in solution as an equal quantity of water, and when the diver is working in shallow depths, up to, say, 30 ft, the amount of nitrogen absorbed is so small that he can stop down as long as is necessary for the purposes of the work, and can come up to the surface as quickly as he likes without any danger. at greater depths approximately the first half of the upward journey may be done in one stage, and the remainder done by degrees, the longest rest being made at a few feet below the surface. the following table shows the time limits in accordance with the latest british admiralty practice; the time under the water being that from leaving the surface to the beginning of the ascent:-table no. l7.--diving data. stoppages in total time minutes at for ascent depth in feet. time under water. different depths in minutes. at 20 ft 10 ft up to 36 no limit 0 to 1 36 to 42 up to 3 hours 1 to 1-1/2 over 3 hours 5 6 42 to 48 up to 1 hour 1-1/2 1 to 3 hours 5 6-1/2 over 3 hours 10 11-1/2 48 to 54 up to 1/2 hour 2 1/2 to 1-1/2 hour 5 7 1-1/2 to 3 hours 10 12 over 3 hours 20 22 54 to 60 up to 20 minutes 2 20 to 45 minutes 5 7 3/4 to 1-1/2 hour 10 12 1-1/2 to 3 hours 5 15 22 over 3 hours 10 20 32 when preparing to ascend the diver must tighten the air valve in his helmet to increase his buoyancy; if the valve is closed too much to allow the excess air to escape, his ascent will at first be gradual, but the pressure of the water reduces, the air in the dress expands, making it so stiff that he cannot move his arms to reach the valve, and he is blown up, with ever-increasing velocity, to the surface. while ascending he should exercise his muscles freely during the period of waiting at each stopping place, so as to increase the circulation, and consequently the rate of deceleration. during the progress of the works the location of the sea outfall will be clearly indicated by temporary features visible by day and lighted by night; but when completed its position must be marked in a permanent manner. the extreme end of the outfall should be indicated by a can buoy similar to that shown in fig. 33, made by messrs. brown, lenox, and co. (limited), milwall, london, e., which costs about £75, including a 20 cwt. sinker and 10 fathoms of chain, and is approved for the purpose by the board of trade. [illustration: fig 33 can buoy for marking outfall sewer.] it is not desirable to fasten the chain to any part of the outfall instead of using a sinker, because at low water the slack of the chain may become entangled, which by preventing the buoy from rising with the tide, will lead to damage; but a special pile may be driven for the purpose of securing the buoy, at such a distance from the outlet that the chain will not foul it. the buoy should be painted with alternate vertical stripes of yellow and green, and lettered "sewer outfall" in white letters 12 in deep. it must be remembered that it is necessary for the plans and sections of outfall sewers and other obstructions proposed to be placed in tidal waters to be submitted to the harbour and fisheries department of the board of trade for their approval, and no subsequent alteration in the works may be made without their consent being first obtained. chapter xiii. the discharge of sea outfall sewers. the head which governs the discharge of a sea outfall pipe is measured from the surface of the sewage in the tank, sewer, or reservoir at the head of the outfall to the level of the sea. as the sewage is run off the level of its surface is lowered, and at the same time the level of the sea is constantly varying as the tide rises and falls, so that the head is a variable factor, and consequently the rate of discharge varies. a curve of discharge may be plotted from calculations according to these varying conditions, but it is not necessary; and all requirements will be met if the discharges under certain stated conditions are ascertained. the most important condition, because it is the worst, is that when the level of the sea is at high water of equinoctial spring tides and the reservoir is practically empty. sea water has a specific gravity of 1.027, and is usually taken as weighing 64.14 lb per cubic foot, while sewage may be taken as weighing 62.45 lb per cubic foot, which is the weight of fresh water at its maximum density. now the ratio of weight between sewage and sea water is as 1 to 1.027, so that a column of sea water l2 inches in height requires a column of fresh water 12.324, or say 12-1/3 in, to balance it; therefore, in order to ascertain the effective head producing discharge it will be necessary to add on 1/3 in for every foot in depth of the sea water over the centre of the outlet. the sea outfall should be of such diameter that the contents of the reservoir can be emptied in the specified time--say, three hours--while the pumps are working to their greatest power in pouring sewage into the reservoir during the whole of the period; so that when the valves are closed the reservoir will be empty, and its entire capacity available for storage until the valves are again opened. to take a concrete example, assume that the reservoir and outfall are constructed as shown in fig. 34, and that it is required to know the diameter of outfall pipe when the reservoir holds 1,000,000 gallons and the whole of the pumps together, including any that may be laid down to cope with any increase of the population in the future, can deliver 600,000 gallons per hour. when the reservoir is full the top water level will be 43.00 o.d., but in order to have a margin for contingencies and to allow for the loss in head due to entry of sewage into the pipe, for friction in passing around bends, and for a slight reduction in discharging capacity of the pipe by reason of incrustation, it will be desirable to take the reservoir as full, but assume that the sewage is at the level 31.00. the head of water in the sea measured above the centre of the pipe will be 21 ft, so that [*math: $21 \times 1/3$], or 7 in--say, 0.58 ft--must be added to the height of high water, thus reducing the effective head from 31.00 10.00 = 21.00 to 20.42 ft the quantity to be discharged will be [*math: $\frac{1,000,000 + (3 * 600,000)}{3}$] = 933,333 gallons per hour = 15,555 gallons per minute, or, taking 6.23 gallons equal to 1 cubic foot, the quantity equals 2,497 cubic feet per min assume the required diameter to be 30 in, then, by hawksley's formula, the head necessary to produce velocity = [*math: $\frac{gals. per min^2}{215 \times diameter in inches^4} = \frac{15,555^2}{215 * 30^4}$] = 1.389 ft, and the head to overcome friction = [*math: $\frac{gals. per min^2 \times length in yards}{240 * diameter in inches^5} = \frac{15,555^2 * 2042}{240 * 30^5}] = 84.719. then 1.389 + 84.719 = 86.108--say, 86.11 ft; but the acutal head is 20.42 ft, and the flow varies approximately as the square root of the head, so that the true flow will be about [*math: $15,555 * \sqrt{\frac{20.42}{86.11} = 7574.8$] [illustration: fig 34 diagram illustrating calculations for the discharge of sea outfalls] --say 7,575 gallons. but a flow of 15,555 gallons per minute is required, as it varies approximately as the fifth power of the diameter, the requisite diameter will be about [*math: \sqrt[5]{\frac{30^5 \times 15,555}{7575}] = 34.64 inches. now assume a diameter of 40 in, and repeat the calculations. then head necessary to produce velocity [*math: = \frac{15,555^2}{215 \times 40^4}] = 0.044 ft, and head to overcome friction = [*math: \frac{15,555^2 \times 2042}{240 \times 40^5}] = 20.104 ft then 0.044 + 20.104 = 20.148, say 20.15 ft, and the true flow will therefore be about [*math: 15,555 * \sqrt{\frac{20.42}{20.15}}] = 15,659 gallons, and the requisite diameter about [*math: \sqrt[5]{\frac{40^5 * 15,555}{15,659}}] = 39.94 inches. when, therefore, a 30 in diameter pipe is assumed, a diameter of 34.64 in is shown to be required, and when 40 in is assumed 39.94 in is indicated. let _a_ = difference between the two assumed diameters. _b_ = increase found over lower diameter. _c_ = decrease found under greater diameter. _d_ = lower assumed diameter. then true diameter = [*math: d + \frac{ab}{b+c} = 30 + \frac{10 \times 4.64}{4.64+0.06} = 30 + \frac{46.4}{4.7} = 39.872], or, say, 40 in, which equals the required diameter. a simpler way of arriving at the size would be to calculate it by santo crimp's formula for sewer discharge, namely, velocity in feet per second = [*math: 124 \sqrt[3]{r^2} \sqrt{s}], where r equals hydraulic mean depth in feet, and s = the ratio of fall to length; the fall being taken as the difference in level between the sewage and the sea after allowance has been made for the differing densities. in this case the fall is 20.42 ft in a length of 6,126 ft, which gives a gradient of 1 in 300. the hydraulic mean depth equals [*math: \frac{d}{4}]; the required discharge, 2,497 cubic feet per min, equals the area, [*math: (\frac{\pi d^2}{4})] multiplied by the velocity, therefore the velocity in feet per second = 4/(pi d^2) x 2497/60 = 2497/(15 pi d^2) and the formula then becomes 2497/(15 pi d^2) = 124 x * 3rd_root(d^2)/3rd_root(4^3*) x sqrt(1)/sqrt(300) or d^2 x 3rd_root(d^2) = 3rd_root(d^6) = (2497 x 3rd_root(16) x sqrt(300)) / (124 x 15 x 3.14159*) or (8 x log d)/3 = log 2497 + (1/3 x log 16) + (* x log 300) log 124 log 15 log 3.14159; or log d = 3/8 (3.397419 + 0.401373 + 1.238561 2.093422 1.176091 0.497150) = 3/8 (1.270690) = 0.476509. * d = 2.9958* feet = 35.9496, say 36 inches. as it happens, this could have been obtained direct from the tables where the discharge of a 36 in pipe at a gradient of 1 in 300 = 2,506 cubic feet per minute, as against 2,497 cubic feet required, but the above shows the method of working when the figures in the tables do not agree with those relating to the particular case in hand. this result differs somewhat from the one previously obtained, but there remains a third method, which we can now make trial of--namely, saph and schoder's formula for the discharge of water mains, v = 174 3rd_root(r^2) x s^.51*. substituting values similar to those taken previously, this formula can be written 2497/(15 pi d^2) = 174 x 3rd_root(d_2)/3rd_root(4^2) x 1^.51/300^.51 or d^2 x 3rd_root(d^2) = 3rd_root(d^6) = (2497 x 3rd_root(16) x 300^.51) / (174 x 15 x 3.14159) or* log d = 3/8 (3.397419 + 0.401373 + (54 x 2.477121) 2.240549 1.176091 0.497150) = 3/8 (1.222647) = 0.458493 * d = 2.874* feet = 34.388 say 34 1/2 inches. by neville's general formula the velocity in feet per second = 140 sqrt(rs)-11(rs)^(1/3) or, assuming a diameter of 37 inches, v = 140 x sqrt(37/(12 x 4) x 1/300) 11 (37/(12x4x300))^(1/3) = 140 x sqrt(37/14400) 11 (37/1440)^(1/3) = 7.09660 1.50656 = 5.59 feet per second. discharge = area x velocity; therefore, the discharge in cubic feet per minute = 5.59 x 60 x (3.14159 x 37^2)/(4*12^2) = 2504 compared with 2,497 c.f.m, required, showing that if this formula is used the pipe should be 37 in diameter. the four formulæ, therefore, give different results, as follows:-hawksley = 40 in neville = 37 in santo crimp = 36 in saph and schoder = 34-1/2 in the circumstances of the case would probably be met by constructing the outfall 36 in in diameter. it is very rarely desirable to fix a flap-valve at the end of a sea outfall pipe, as it forms a serious obstruction to the flow of the sewage, amounting, in one case the writer investigated, to a loss of eight-ninths of the available head; the head was exceptionally small, and the flap valve practically absorbed it all. the only advantage in using a flap valve occurs when the pipe is directly connected with a tank sewer below the level of high water, in which case, if the sea water were allowed to enter, it would not only occupy space required for storing sewage, but it would act on the sewage and speedily start decomposition, with the consequent emission of objectionable odours. if there is any probability of sand drifting over the mouth of the outfall pipe, the latter will keep free much better if there is no valve. schemes have been suggested in which it was proposed to utilise a flap valve on the outlet so as to render the discharge of the sewage automatic. that is to say, the sewage was proposed to be collected in a reservoir at the head of, and directly connected to, the outfall pipe, at the outlet end of which a flap valve was to be fixed. during high water the mouth of the outfall would be closed, so that sewage would collect in the pipes, and in the reservoir beyond; then when the tide had fallen such a distance that its level was below the level of the sewage, the flap valve would open, and the sewage flow out until the tide rose and closed the valve. there are several objections to this arrangement. first of all, a flap valve under such conditions would not remain watertight, unless it were attended to almost every day, which is, of course, impracticable when the outlet is below water. as the valve would open when the sea fell to a certain level and remain open during the time it was below that level, the period of discharge would vary from, say, two hours at neap tides to about four hours at springs; and if the two hours were sufficient, the four hours would be unnecessary. then the sewage would not only be running out and hanging about during dead water at low tide, but before that time it would be carried in one direction, and after that time in the other direction; so that it would be spread out in all quarters around the outfall, instead of being carried direct out to sea beyond chance of return, as would be the case in a welldesigned scheme. when opening the valve in the reservoir, or other chamber, to allow the sewage to flow through the outfall pipe, care should be taken to open it at a slow rate so as to prevent damage by concussion when the escaping sewage meets the sea water standing in the lower portion of the pipes. when there is considerable difference of level between the reservoir and the sea, and the valve is opened somewhat quickly, the sewage as it enters the sea will create a "water-spout," which may reach to a considerable height, and which draws undesirable attention to the fact that the sewage is then being turned into the sea. chapter xiv trigonometrical surveying. in the surveying work necessary to fix the positions of the various stations, and of the float, a few elementary trigonometrical problems are involved which can be advantageously explained by taking practical examples. having selected the main station a, as shown in fig. 35, and measured the length of any line a b on a convenient piece of level ground, the next step will be to fix its position upon the plan. two prominent landmarks, c and d, such as church steeples, flag-staffs, etc., the positions of which are shown upon the ordnance map, are selected and the angles read from each of the stations a and b. assume the line a b measures ll7 ft, and the angular measurements reading from zero on that line are, from a to point c, 29° 23' and to point d 88° 43', and from b to point c 212° 43', and to point d 272° 18' 30". the actual readings can be noted, and then the arrangement of the lines and angles sketched out as shown in fig. 35, from which it will be necessary to find the lengths ac and ad. as the three angles of a triangle equal 180°, the angle b c a = 180°147° 17'-29° 23'= 3° 20', the angle b d a = 180°-87° 41' 30"88° 43'= 3° 35' 30". in any triangle the sides are proportionate to the sines of the opposite angles, and vice versa; therefore, a b : a c :: sin b c a : sin a b c, or sin b c a : a b :: sin abc : a c, nr a c = (a b sin a b c) / (sin b c a) = (117 x sin 147° 17') / (sin 3° 20') or log a c = log 117 + l sin 147° 17' l sin 3° 20'. the sine of an angle is equal to the sine of its supplement, so that sin 147° 17' = sin 32° 43', whence log a c = 2.0681859 + 9.7327837-8.7645111 = 3.0364585 therefore a c = 1087.6 feet. similarly sin b d a: a b :: sin a b d: a d a b sin a b d 117 x sin 87° 41' 30" therefore a d = --------------= ---------------------- sin b d a sin 3° 35' 30" whence log a d = log ll7 + l sin 87° 41' 30" l sin 3° 35' 30" = 2.0681859 + 9.99964745 8.79688775 = 3.2709456 therefore ad = 1866.15 feet. the length of two of the sides and all three angles of each of the two triangles a c b and a d b are now known, so that the triangles can be drawn upon the base a b by setting off the sides at the known angles, and the draughtsmanship can be checked by measuring the other known side of each triangle. the points c and d will then represent the positions of the two landmarks to which the observations were taken, and if the triangles are drawn upon a piece of tracing paper, and then superimposed upon the ordnance map so that the points c and d correspond with the landmarks, the points a and b can be pricked through on to the map, and the base line a b drawn in its correct position. if it is desired to draw the base line on the map direct from the two known points, it will be necessary to ascertain the magnitude of the angle a d c. now, in any triangle the tangent of half the difference of two angles is to the tangent of half their sum as the difference of the two opposite sides is to their sum; that is:- tan 1/2 (acd adc): tan 1/2 (acd + adc):: ad ac : ad + ac, but acd + adc = l80° cad = 120° 40', therefore, tan 1/2 (acd adc): tan 1/2 (120° 40'):: (1866.15 1087.6): (1866.15 + 1087.6), 778.55 tan 60° 20' therefore, tan 1/2 (acd adc) = ------------------- 2953.75 or l tan 1/2 (acd adc) = log 778.55 + l tan 60° 20' log 2953.75 . = 2.8912865 + 10.2444l54 3.4703738 = 9.6653281 .�. 1/2 (acd adc) = 24° 49' 53" .�. acd adc = 49° 39' 46". then algebraically (acd + adc) (acd adc) adc = -------------------------- 2 120° 40' 49° 39' 46" 71° 0' 14" .�. adc = ------------------------= -----------= 35° 30' 7", 2 2 acd = 180° 35° 30' 7" 59° 20' = 85° 9' 53". [illustration: fig. 35.--arrangement of lines and angles showing theodolite readings and dimensions.] now join up points c and d on the plan, and from point d set off the line d a, making an angle of 35° 30' 7" with c d, and having a length of l866.15 ft, and from point c set off the angle a c d equal to 85° 9' 53". then the line a c should measure l087.6 ft long, and meet the line a d at the point a, making an angle of 59° 20'. from point a draw a line a b, ll7 ft long, making an angle of 29° 23' with the line a c; join b c, then the angle abc should measure 147° 17', and the angle b c a 3° 20'. if the lines and angles are accurately drawn, which can be proved by checking as indicated, the line a b will represent the base line in its correct position on the plan. the positions of the other stations can be calculated from the readings of the angles taken from such stations. take stations e, f, g, and h as shown in fig. 36*, the angles which are observed being marked with an arc. it will be observed that two of the angles of each triangle are recorded, so that the third is always known. the full lines represent those sides, the lengths of which are calculated, so that the dimensions of two sides and the three angles of each triangle are known. starting with station e, sin a e d: a d:: sin d a e: d e a d sin d a e d e = ------------- sin a e d or log d e = log a d + l sin d a e-l sin a e d. from station f, e and g are visible, but the landmark d cannot be seen; therefore, as the latter can be seen from g, it will be necessary to fix the position of g first. then, sin e g d: d e :: sin e d g : e g, d e sin e d g or eg= -------------- sin e g d now, sin e f g: e g :: sin f e g : f g e g sin f e g f g = ------------ sin e f g thus allowing the position of f to be fixed, and then sin f h g : f g :: sin f g h : f h f g sin f g h f h= ------------ sin f h g [illustration: fig 36.--diagram illustrating trigonometrical survey of observation stations.] in triangles such as e f g and f g h all three angles can be directly read, so that any inaccuracy in the readings is at once apparent. the station h and further stations along the coast being: out of sight of landmark d, it will be as well to connect the survey up with another landmark k, which can be utilised in the forward work; the line k h being equal to f h sin k f h ------------sin f k h the distance between c and d in fig. 35 is calculated in a similar manner, because sin a c d : a d:: sin cad : cd, ad sin cad 1866.15 sin 59° 20' or cd = --------- = ------------------ sin scd sin 85° 9' 53" or log cd = log 1866.15 + l sin 59° 20' l sin 85° 9' 53" = 3.2709456 + 9.9345738 9.9984516 = 3.2070678. ' . cd = 1610.90 ft the distance between any two positions of the float can be obtained by calculation in a similar way to that in which the length c d was obtained, but this is a lengthy process, and is not necessary in practical work. it is desirable, of course, that the positions of all the stations be fixed with the greatest accuracy and plotted on the map, then the position of the float can be located with sufficient correctness, if the lines of sight obtained from the angles read with the theodolites are plotted, and their point of intersection marked on the plan. the distance between any two positions of the float can be scaled from the plan. the reason why close measurement is unnecessary in connection with the positions of the float is that it represents a single point, whereas the sewage escaping with considerable velocity from the outfall sewer spreads itself over a wide expanse of sea in front of the outlet, and thus has a tangible area. the velocity of any current is greatest in the centre, and reduces as the distance from the centre increases, until the edges of the current are lost in comparative still water; so that observations taken of the course of one particle, such as the float represents, only approximately indicate the travel of the sewage through the sea. another point to bear in mind is that the dilution of the sewage in the sea is so great that it is generally only by reason of the unbroken fæcal, or other matter, that it can be traced for any considerable distance beyond the outfall. it is unlikely that such matters would reach the outlet, except in a very finely divided state, when they would be rapidly acted upon by the sea water, which is a strong oxidising agent. chapter xv. hydrographical surveying. hydrographical surveying is that branch of surveying which deals with the complete preparation of charts, the survey of coast lines, currents, soundings, etc., and it is applied in connection with the sewerage of sea coast towns when it is necessary to determine the course of the currents, or a float, by observations taken from a boat to fixed points on shore, the boat closely following the float. it has already been pointed out that it is preferable to take the observations from the shore rather than the boat, but circumstances may arise which render it necessary to adopt the latter course. in the simplest case the position of the boat may be found by taking the compass bearings of two known objects on shore. for example, a and b in fig. 37 may represent the positions of two prominent objects whose position is marked upon an ordnance map of the neighbourhood, or they may be flagstaffs specially set up and noted on the map; and let c represent the boat from which the bearings of a and b are taken by a prismatic compass, which is marked from 0 to 360°. let the magnetic variation be n. 15° w., and the observed bearings a 290, b 320, then the position stands as in fig. 38, or, correcting for magnetic variation, as in fig. 39, from which it will be seen that the true bearing of c from a will be 275-180=95° east of north, or 5° below the horizontal, and the true bearing of c from b will be 305-180=120° east of north, or 35° below the horizontal. these directions being plotted will give the position of c by their intersection. fig. 40 shows the prismatic compass in plan and section. it consists practically of an ordinary compass box with a prism and sight-hole at one side, and a corresponding sight-vane on the opposite side. when being used it is held horizontally in the left hand with the prism turned up in the position shown, and the sight-vane raised. when looking through the sight-hole the face of the compass-card can be seen by reflection from the back of the prism, and at the same time the direction of any required point may be sighted with the wire in the opposite sight vane, so that the bearing of the line between the boat and the required point may be read. if necessary, the compass-card may be steadied by pressing the stop at the base of the sight vane. in recording the bearings allowance must in all cases be made for the magnetic pole. the magnetic variation for the year 1910 was about l5 1/2° west of north, and it is moving nearer to true north at the rate of about seven minutes per annum. [illustration: fig. 37.--position of boat found by compass bearings.] [illustration: fig. 38.--reduction of bearings to magnetic north.] [illustration: fig. 39.--reduction of bearings to true north.] there are three of euclid's propositions that bear very closely upon the problems involved in locating the position of a floating object with regard to the coast, by observations taken from the object. they are euclid i. (32), "the three interior angles of every triangle are together equal to two right angles"; euclid iii. (20), "the angle at the centre of a circle is double that of the angle at the circumference upon the same base--that is, upon the same part of the circumference," or in other words, on a given chord the angle subtended by it at the centre of the circle is double the angle subtended by it at the circumference; and euclid iii. (21), "the angles in the same segment of a circle are equal to one another." [illustration: fig. 40.--section and plan of prismatic compass.] having regard to this last proposition (euclid iii., 21), it will be observed that in the case of fig. 37 it would not have been possible to locate the point c by reading the angle a c b alone, as such point might be amywhere on the circumference of a circle of which a b was the chord. the usual and more accurate method of determining the position of a floating object from the object, itself, or from a boat alongside, is by taking angles with a sextant, or box-sextant, between three fixed points on shore in two operations. let a b c, fig. 41, be the three fixed points on shore, the positions of which are measured and recorded upon an ordnance map, or checked if they are already there. let d be the floating object, the position of which is required to be located, and let the observed angles from the object be a d b 30° and b d c 45°. then on the map join a b and b c, from a and b set off angles = 90 30 = 60°, and they will intersect at point e, which will be the centre of a circle, which must be drawn, with radius e a. the circle will pass through a b, and the point d will be somewhere on its circumference. then from b and c set off angles = 90-45 = 45°, which will intersect at point f, which will be the centre of a circle of radius f b, which will pass through points b c, and point d will be somewhere on the circumference of this circle also; therefore the intersection of the two circles at d fixes that point on the map. it will be observed that the three interior angles in the triangle a b e are together equal to two right angles (euclid i. 32), therefore the angle a e b = 180 2 x (90 30) = 600, so that the angle a e b is double the angle a d b (euclid iii., 20), and that as the angles subtending a given chord from any point of the circumference are equal (euclid iii, 21), the point that is common to the two circumferences is the required point. when point d is inked in, the construction lines are rubbed out ready for plotting the observations from the next position. when the floating point is out of range of a, a new fixed point will be required on shore beyond c, so that b, c, and the new point will be used together. another approximate method which may sometimes be employed is to take a point on a piece of tracing paper and draw from it three lines of unlimited length, which shall form the two observed angles. if, now, this piece of paper is moved about on top of the ordnance map until each of the three lines passes through the corresponding fixed points on shore, then the point from which the lines radiate will represent the position of the boat. [illustration: fig. 41. geometrical diagram for locating observation point afloat.] the general appearance of a box-sextant is as shown in fig. 42, and an enlarged diagrammatic plan of it is shown in fig. 43. it is about 3 in in diameter, and is made with or without the telescope; it is used for measuring approximately the angle between any two lines by observing poles at their extremities from the point of intersection. in fig. 43, a is the sighthole, b is a fixed mirror having one-half silvered and the other half plain; c is a mirror attached to the same pivot as the vernier arm d. the side of the case is open to admit rays of light from the observed objects. in making an observation of the angle formed by lines to two poles, one pole would be seen through the clear part of mirror b, and at the same time rays of light from the other pole would fall on to mirror c, which should be moved until the pole is reflected on the silvered part of mirror b, exactly in line, vertically, with the pole seen by direct vision, then the angle between the two poles would be indicated on the vernier. take the case of a single pole, then the angle indicated should be zero, but whether it would actually be so depends upon circumstances which may be explained as follows: suppose the pole to be fixed at e, which is extremely close, it will be found that the arrow on the vernier arm falls short of the zero of the scale owing to what may be called the width of the base line of the instrument. if the pole is placed farther off, as at f, the rays of light from the pole will take the course of the stroke-and-dot line, and the vernier arm will require to be shifted nearer the zero of the scale. after a distance of two chains between the pole and sextant is reached, the rays of light from the pole to b and c are so nearly parallel that the error is under one minute, and the instrument can be used under such conditions without difficulty occurring by reason of error. to adjust the box-sextant the smoked glass slide should be drawn over the eyepiece, and then, if the sun is sighted, it should appear as a perfect sphere when the vernier is at zero, in whatever position the sextant may be held. when reading the angle formed by the lines from two stations, the nearer station should be sighted through the plain glass, which may necessitate holding the instrument upside down. when the angle to be read between two stations exceeds 90°, an intermediate station should be fixed, and the angle taken in two parts, as in viewing large angles the mirror c is turned round to such an extent that its own reflection, and that of the image upon it, is viewed almost edgeways in the mirror b. [illustration: fig. 42.--box-sextant.] it should be noted that the box-sextant only reads angles in the plane of the instrument, so that if one object sighted is lower than the other, the angle read will be the direct angle between them, and not the horizontal angle, as given by a theodolite. the same principles may be adopted for locating the position of an object in the water when the observations have to be taken at some distance from it. to illustrate this, use may be made of an examination question in hydrographical surveying given at the royal naval college, incidentally, it shows one method of recording the observations. the question was as follows:-[illustration: fig. 43.--diagram showing principle of boxsextant] "from coastguard, mound bore n. 77° w. (true) 0.45 of a mile, and mill bore, n. 88° e, 0.56 of a mile, the following stations were taken to fix a shoal on which the sea breaks too heavily to risk the boat near:-mound 60° c.g. 47° mill. [greek: phi] centre of shoal mound 55° c.g. 57° 30' mill. [greek: phi] centre of shoal. project the positions on a scale of 5 in = a mile, giving the centre of the shoal." it should be noted that the sign [greek: phi] signifies stations in one line or "in transit," and c g indicates coastguard station. the order of lettering in fig. 44 shows the order of working. [illustration: fig. 44.--method of locating point in water when observations have to be taken beyond it.] the base lines a b and a c are set out from the lengths and directions given; then, when the boat at d is "in transit" with the centre of the shoal and the coastguard station, the angle formed at d by lines from that point to b and a is 60°, and the angle formed by lines to a and c is 47°. if angles of 90° 60° are set up at a and b, their intersection at e will, as has already been explained, give the centre of a circle which will pass through points a, b, and d. similarly, by setting up angles of 90°-47° at a and c, a circle is found which will pass through a c and d. the intersection of these circles gives the position of the boat d, and it is known that the shoal is situated somewhere in the straight line from d to a. the boat was then moved to g, so as to be "in transit" with the centre of the shoal and the mound, and the angle b g a was found to be 55°, and the angle a g c 57° 30'. by a similar construction to that just described, the intersection of the circles will give the position of g, and as the shoal is situated somewhere in the line g b and also in the line a d, the intersection of these two lines at k will give its exact position. aberdeen sea outfall admiralty, diving regulations of --charts, datums for soundings on --main currents shown on age of tide air pressure on tides, effect of almanac, nautical analysis of cement --sea water anchor bolts for sea outfalls anemometer for measuring wind aphelion apogee atlantic ocean, tides in autumnal equinox barometric pressure, effect on tides of beach material, use in concrete of beaufort scale for wind bench mark for tide gauge "bird" tides board of trade, approval of outfall by bolts for sea outfall pipes box sextant bristol channel --datum for tides at buoy for marking position of outfall can buoy to mark position of outfall cast iron, resistance to sea water of cement, action of sea water on --analysis of --characteristics causing hardening of --setting of --effect of saline matters on strength of --sea water on setting time of --physical changes due to action of sea water on --precautions in marine use of --retardation of setting time of --tests for marine use of centrifugal force, effect on tides of centripetal force, effect on tides of --variations in intensity of charts, datum for soundings on --main currents shown on chepstow, greatest tide at clifton, tides at compass, magnetic variation --marine --prismatic concentration of storm water in sewers concrete, action of sea water on --composition to withstand sea water --destruction in sea water of crown, foreshore owned by currents and tides. lack of co-ordination in change of --formation of --in rivers, 30 --observations of --variation of surface and deep --variations in velocity of current observations by marine compass --theodolites --floats for --hydrographical surveying for --method of making --plotting on plans, the --selecting stations for --special points for consideration in making --suitable boat for --trigonometrical surveying for datum levels for tides declination of sun and moon decompression after diving density of sea water derivative waves design of schemes, conditions governing diffusion of sewage in sea discharge from sea outfalls, calculations for --precautions necessary for --time of disposal of sewage by diffusion --dependent on time of discharge diurnal inequality of tides diverting-plate storm overflow diving --illnesses caused by --instruction in --medical examination previous to --physical principles involved in --equipment diving equipment, weight of dublin, datum for tides at earth, distance from moon --sun --orbit around sun of --size of --time and speed of revolution of equinox erosion of shore caused by sea outfalls establishment flap valves on sea outfall pipes floats, deep and surface --to govern pumping plant foreshore owned by crown gauges, measuring flow over weirs by gauging flow of sewage --, formula: for gradient, effect on currents of surface --tides of barometric gravity, specific, of sea water --tides caused by great crosby sea outfall harbour and fisheries dept., approval of outfall by harwich, mean level of sea at high water mark of ordinary tides hook-gauge, for measuring flow over weirs hull, mean level of sea at hydrographical surveying problems in current observations impermeable areas, flow of rain off --percentage of --per head of population indian ocean, tides in infiltration water irish channel, analysis of water in iron, effect of sea water on cast june, low spring: tides in kelvin's tide predicting machine land, area of globe occupied by leap-weir storm overflow liverpool, datum for tides at --soundings on charts of --tide tables lloyd-davies, investigations by local government board, current observations required for london, datum for port of low water mark of ordinary tides lunar month lunation magnetic variation of compass marine compass mean high water mersey, soundings on charts of mixing action of sewage and water moon, declination of --distance from earth of --effect on tides of --mass of --minor movements of --orbit around earth of --perigee and apogee morse code for signalling nautical almanac neap tides --average rise of orbit of earth around sun --moon around earth ordinary tides, lines on ordnance maps of ordnance datum for england --ireland, 17 --records made to fix --maps, lines of high and low water on outfall sewers, approval by board of trade of --calculations for discharge of --construction of --detail designs for --details of cast-iron pipe joints for --flap valves on end of --inspection during construction of --marking position by buoy of --selection of site for overflows for storm water pacific ocean, tides in parliament, current observations required for perigee perihelion piling for sea outfalls pipes, joints of cast iron --steel plymouth, mean sea level at predicting tides primary waves prismatic compass pumping --cost of --plant --management of --utilisation of windmills for pumps for use with windmills quantity of rainfall to provide for --sewage to provide for rainfall --at times of light winds --frequency of heavy --in sewers --intensity of --storage capacity to be provided for --to provide for range of tides rise of tides screening sewage before discharge --storm water before overflow sea, mean level of sea outfalls, calculations for discharge of --construction of --design of --lights and buoy to mark position of --selection of site for seashore material used in concrete sea, variation around coast in level of --water, analysis of --effect on cast-iron of --effect on cement --galvanic action in --weight of secondary waves separate system of sewerage sewage, effect of sea water on --gauging flow of --calculations for --hourly and daily variation in flow of, 42 --quantity to provide for sewers, economic considerations in provision of surface water --effect on design of scheme of subsidiary --storm water in sextant, box signalling, flags for --morse code for solstice, summer and winter soundings on charts, datum for southampton, tides at southern ocean, high water in --origin of tides in --width and length of specific gravity of sea water spring tides --average rise of --variation in height of storage tanks, automatic high water alarms for --determination of capacity of --for windmill pumps storm water in sewers --overflows subsidiary sewers, effect on design of scheme of summer solstice sun, aphelion and perihelion --declination of --distance from earth --effect on tides of --mass of --minor movements of surface water sewers, average cost of --economic considerations in provision of surveying, problems in hydrographical --trigonometrical thames conservancy datum --flow of sewage in tidal action in crust of earth --attraction --day, length of --flap valves on sea outfall pipes --observations, best time to make --records, diagram of --rivers, tides and currents in --waves, length of primary --secondary or derivative --speed of primary --velocity of tide gauge, method of erecting --selecting position of tide, observations of rise and fall of tide-predicting machine --recording instrument --tables tides, abnormally high --age of tides and currents, lack of co-ordination in change of --diagrammatic representation of principal --diurnal inequality --double, 9 --effect of barometric pressure on --centripetal and centrifugal force --storms on, --extraordinary high --formation of --in rivers --lines on ordnance maps of high and low water of --propagation to branch oceans of --proportionate effect of sun and moon on --range of --rate of rise and fall of --rise of --spring and neap --variations in height of towers for windmills trade wastes, effect on flow of sewage of trass in cement for marine vork trigonometrical surveying for cuirent observations trinity high water mark upland water, effect on rivers of valves on sea outfall pipes velocity of currents vernal equinox visitors, quantity of sewage from volume of sewage water, area of globe occupied by --fittings, leakage from --power for pumping --supply, quantity per head for --weight of waterloo sea outfall waves, horizontal movement of --motion of --primary and secondary --tidal --wind weight of fresh water --sea water --sewage weirs for gauging sewage, design of --storm overflow by parallel weymouth, mean level of sea at wind --beaufort scale for wind, mean hourly velocity of --measuring velocity of --monthly analysis of --power of windmills according to velocity of --rainfall at time of light --velocity and pressure of --waves windmills --comparative cost of --details of construction of --effective duty of --efficient sizes of --for pumping sewage --height of towers for --power in varying winds of winter solstice +---------------------------------------------------------------------+ | transcriber's notes: | | | | * text in italics in the original document is presented here | | between underscores, as in _text_. | | * bold-face text in the original document is presented here between | | equal signs, as in =text=. | | * old-english font is presented here by enclosing the text between | | ~, as in ~text~. | | * superscript and subscript are presented as ^{text} and _{text}, | | respectively. | | * the oe-ligature is presented as [oe] as in diarrh[oe]a. | | * small-caps text in the original document is presented as all-caps | | here. | | * the equilibrium arrow in chemical reactions is presented here as | | <=>. | | * footnotes (indicated by [a], [b], etc.) have been moved to | | directly below the paragraph or table they refer to, references | | (indicated by [1], [2], etc.) are collected at the end of each | | chapter. | | * greek in the original document has been transcribed as for example| | [alpha] for individual letters and as [greek: chlôros] for | | complete words. | | * positive and negative ions are presented as for example h^{.} and | | oh', as in the original document. | | | | see additional transcriber's notes at the end of this e-text. | +---------------------------------------------------------------------+ works of joseph race published by john wiley & sons, inc. =examination of milk for public health purposes.= a practical handbook for those engaged in the chemical and bacteriological examination of milk for public health purposes. vi + 224 pages, 5-1/4 × 8, 4 diagrams. cloth, $1.75 net. =chlorination of water.= in this book the various aspects and methods of chlorination are discussed with a view to stimulating research work in this field of science. viii + 158 pages, 5-1/4 × 8, 12 figures and 16 diagrams. cloth, $1.50 net. chlorination of water by joseph race, f.i.c. _city bacteriologist and chemist, ottawa; capt. canadian army hydrological corps; associate member of committee on water supplies, american public health association; member of committee on water standards and standard methods of analysis, american water works association; chairman of committee on standard methods of analysis, canadian public health association_ _first edition_ new york john wiley & sons, inc. london: chapman & hall, limited 1918 copyright, 1918 by joseph race, f.i.c. press of braunworth & co. book manufacturers brooklyn, n. y. dedicated to ~sir alexander houston, k.b.e., d.sc., m.b., c.m.~ preface no apology is necessary for the publication of a book on the chlorination of water. this method of treatment, practically unknown fifteen years ago, has advanced in popularity during the last decade in a most remarkable manner, and in 1918 over forty millions of people are being supplied with chlorinated water. it may justifiably be said that no other sanitary measure has accomplished so much at so small a cost; and that civilization owes a deep debt of gratitude to the pioneers in municipal water chlorination: dr. a. c. houston in england, and mr. g. a. johnson and dr. leal in america. in this volume i have endeavoured to collect and correlate the information hitherto scattered in various journals and treatises and to present it in a comprehensible manner. the various aspects and methods of chlorination are discussed and suggestions have been made which, i hope, will stimulate research work in this fertile field of science. i wish to acknowledge my indebtedness to the engineering staff of the ottawa water works department and to lieut. w. m. bryce for the preparation of diagrams. joseph race. ottawa, ont., april, 1918. contents chapter page i. historical 1 sodium chloride. chlorine. bleach. eau de javelle. antiseptics. hermite fluid. webster's process. electrozone. chlorination of sewage in germany, u. s. a., and england. chlorination of water. lincoln installation. oxychloride. german experiments. european practice. inception of chlorination in america. ii. modus operandi 14 composition of bleach. bleaching action. nascent oxygen hypothesis. hydrolysis of bleach. effect of acids and salts on hydrolysis and germicidal action. effect of ammonia. direct toxic action. hypochlorous acid. sodium hypochlorite. chlorine water. nature of action. iii. dosage 30 organic matter. initial count. viability of organisms. mineral matter. colour. temperature. admixture. contact period. turbidity. light. determination of dosage. iv. bacteria surviving chlorination 50 disinfectants. antiseptics. viability of bacteria. new york results. reversed ratio of counts. coliform organisms. aftergrowths in water and sand. v. complaints 62 auto-suggestion. tastes and odours. sludge problem. colic. effect on fish and birds. effect on plants and flowers. corrosion of iron and lead pipes. vi. bleach treatment 72 storage of bleach. mixing tanks. storage tanks. dosing apparatus. control. analysis of liquor. detection and estimation of free chlorine. chlorometer. cost of construction and operation. antichlors. dechlor filters. vii. liquid chlorine 89 historical. leavitt-jackson machine. electro bleaching gas co.'s types. wallace and tiernan's manual control types. effect of temperature on gas pressure. impurities in gas. advantages. comparison of liquid chlorine and bleach. cost of treatment. popularity. chlorine water. viii. electrolytic hypochlorites and chlorine 105 hermite fluid. eau de javelle. chloros. non-diaphragm cells: dayton, hermite, mather and platt, haas and oettel. diaphragm cells: hargreaves-bird, nelson, allen-moore. montreal installation. costs. ix. chloramine 115 preparation. absorption by water. experimental results. works results. ratio of chlorine to ammonia. economics. advantages. operation. other chloramines. halazone. x. results obtained 132 object of chlorination. effect on filter rates and algæ. hygienic results. typhoid rates. typhoid reduction at philadelphia, chicago, and ottawa. abortive epidemics. use and abuse of chlorination. appendix 147 estimation of free chlorine in water. name index 151 subject index 155 chlorination of water chapter i historical chlorine, although one of the most widely distributed elements known to chemists, is never found in the free condition in nature; it exists in enormous quantities in combination with sodium, potassium, calcium, magnesium, etc. as sodium chloride, common salt, it occurs in practically inexhaustible quantities in sea water together with smaller quantities of other chlorides. in mineral form, enormous deposits of sodium chloride are found in galicia, transylvania, spain, in england (particularly in cheshire), and in sections of north america. the most important deposits of potassium chloride are those at stassfurt, germany, where it occurs either in the crystalline condition as sylvine or combined with magnesium chloride as carnallite. chlorine was discovered by the swedish chemist scheele in 1774, but he, like lavoisier and his pupil berthollet, who declared it an oxygenated muriatic acid, was unaware of the elemental nature of the new substance. sir humphrey davy investigated this body in 1810 and definitely proved it to be an element; davy designated the element chlorine from the greek [greek: chlôros] = green. the first attempt to utilise chlorine, or its compounds, for bleaching purposes, appears to have been due to james watt, who noticed the decolourising properties of chlorine during a visit to berthollet. this attempt ended in failure because of the destructive effect on the fibres, but, in later trials, this was prevented by first absorbing the gas in a solution of fixed alkali. these experiments proved the possibility of bleaching by means of chlorine compounds but the high cost of soda made the process unprofitable, and it was not until henry succeeded in preparing a combination with lime that could be reduced to a dry powder that this mode of chemical bleaching became a commercial success. the manufacture of chloride of lime (hypochlorite of lime, bleaching powder, bleach) was taken up by charles tennant in 1799 at st. rollox near glasgow, and in 1800 about 50 tons were sold at a price of $680 (£139) per ton. chlorine is produced as a by-product in the manufacture of soda by the leblanc process, but until 1865, when the british alkali act stopped the discharge of hydrochloric acid vapours into the atmosphere, the development of the bleaching powder industry was not rapid. the hydrochloric acid that was formerly discharged into the air as a waste product afterwards became a valuable asset that enabled the leblanc process to successfully compete with the newer ammonia-soda process. in 1890 another competitor to the leblanc process was introduced when caustic and chlorine were produced in germany by electrolytic methods. after the successful development of this method in germany, it was taken up in the united states of america and in 1912 more than 30,000 electrical horse-power were daily used in this industry. in 1914 the almost complete cessation of exports of bleach from europe raised the price, which attained phenomenal heights in 1916 (cf. page 125), and stimulated the production of bleach both in the u. s. a. and canada. table i.--bleach statistics. north america -------------+----------------------------+-------------------- year. | bleach manufactured, | selling price | short tons. | per 100 lbs. -------------+----------------------------+-------------------- 1904 | 19,000 | 1909 | 58,000 | 1914 | 155,000 | $1.63 1915 | 180,000[a] | 2.63 1916 | 230,000[a] | 6.56 1917 | 260,000[a] | 2.44 -------------+----------------------------+-------------------- [a] estimated. as a disinfectant, chlorine was first used about the year 1800 by de morveau, in france, and by cruikshank, in england, who prepared the gas by heating a mixture of hydrochloric acid and potassium bichromate or pyrolusite; this is essentially the same as the original mixture used by scheele. during the early part of the last century the efficacy of chlorine of lime as a disinfectant, and particularly as a deodourant, was well recognised and as early as 1854 an english royal commission used this substance for deodourising the sewage of london. a committee of the american public health association reported in 1885 that chloride of lime was the best disinfectant available when cost and efficiency were considered. eau de javelle, first made by percy at the javelle works near paris in 1792, is another chlorine compound that has enjoyed a considerable reputation as a disinfectant and deodouriser for over a century; it is essentially a mixture of sodium chloride and sodium hypochlorite. the discovery of electrolytic hypochlorites dates back to 1859, when watt found that chlorides of the fixed alkalies and alkaline earths yielded hypochlorites on being submitted to the action of an electrical current. until the middle of the last century disinfection was regarded as a process that arrested or prevented putrefactive changes but the nature of these changes was imperfectly comprehended and micro-organisms were not associated with them. in 1839 theodor schwann,[1] who might be regarded as the founder of the school of antiseptics, reported that "fermentation is arrested by any influence capable of killing fungi, especially by heat, potassium arseniate, etc...."; but his results were not accepted by the adherents of the theory of spontaneous generation and it was not until the publication of the work of schroder and dusch[2] that schwann's views were even partially accepted. the final refutation to the spontaneous generation theory was given by the monumental researches of pasteur who, in 1862, proved the possibility of preparing sterile culture media and demonstrated the manner in which they could be protected from contamination. bacteria and other micro-organisms were shown to be responsible for the phenomena that had been attributed previously to the "oxygen of the air," and from this period the development of bacteriology as a science proceeded rapidly. the next important step, from the public health standpoint, was the discovery by koch, in 1876, that a specific bacterium (_b. anthracis_) was the cause of a specific disease in cattle (anthrax or splenic fever). in 1882 koch made a further advance by developing a solid culture medium which permitted disinfectants and antiseptics to be studied quantitatively with a greater degree of accuracy than had been possible previously. since 1845, when semmelweiss succeeded in stamping out puerperal fever in vienna, where it had been so long established as to be endemic, chlorine has been very generally employed in sanitary work and the conditions necessary for obtaining successful results have been partially elucidated. baxter was the first to state that the disinfecting action depended more upon the nature of the pabulum than upon the specific organism present and this was confirmed later by kuhn, bucholtz, and haberkorn. the latter found that urine consumed large quantities of chlorine before any disinfection occurred. one of the earliest preparations used in sanitary work was an electrolysed sea water, usually known as hermite fluid. this was introduced by m. hermite in 1889 and was employed for domestic purposes and for flushing sewers and latrines. it was used at brest for the dissolution of fæcal matter and a prolonged trial was given to it at worthing in 1894. the report of dupré and klein, who conducted the bacteriological examinations, was against the process, but ruffer and roscoe reported more favourably and further trials were carried out at havre, l'orient, and nice. the _lancet_ (may 26, 1894) reported at length upon the worthing experiments: it was found that during the electrolysis of the sea water, the magnesium chloride was also partially converted into hypochlorite, which then dissociated into magnesium hydrate and hypochlorous acid; the former deposited in the electrolyser and left the solution acid and unstable; urine was found to act upon it at once with a consequent loss in strength of over 50 per cent. another electrolytic method was that of webster,[3] who installed an experimental plant at crossness, near london, in 1889. a low-tension direct current was passed between iron electrodes placed in the sewage and although the process was largely one of chemical precipitation, webster noted the disinfecting value of the hypochlorite formed from the chlorides normally present in the sewage. he also directed the attention of sanitarians to the possibility of using sea water as a cheap source of chlorides and a plant based on this principle was erected in bradford in 1890 and reported upon by mclintock.[4] strong salt solutions were substituted for sea water by woolf and the product was commercially known as "electrozone." a plant of this description was installed at brewster, n. y., in 1893[5] for chlorinating the sewage from a small group of houses. the sewage was discharged into a small creek which polluted croton lake. successful results led to a similar treatment near tonetta creek.[6] this was apparently the first occasion on which the specific object was the destruction of bacteria. electrozone was used at maidenhead, on the thames, in 1897 and the installation was reported upon by robinson, kanthack, and rideal in 1898. kanthack found that a dosage 3-3.6 p.p.m. reduced the organisms in a sewage effluent to 10-50 per c.cm. whilst rideal found that about 18 p.p.m. of chlorine produced a condition of sterility in 1 c.cm. chloride of lime had previously been used in the london sewage as a deodourant by dibden in 1884 but the treatment was not successful and was abandoned in favour of other oxidisers. during the last decade of the twentieth century the use of bleach for the disinfection of both sewage and water received the attention of many well-known german sanitarians and many important results were obtained. in the earlier experiments made at hamburg, proskauer and elsner[7] obtained satisfactory results with 3-4 p.p.m. of chlorine on a clarified sewage with 10 minutes contact. dunbar and zirn (_ibid._) used crude sewage and found that 17 p.p.m. of available chlorine were required to remove _b. typhosus_ and cholera vibria with a contact period of two hours. a striking feature of all the german work on chlorination is the very high degree of purification aimed at: quantities as large as one litre were tested for specific organisms and in many of the experiments with sewage _b. coli_ was found to be absent from a considerable percentage of the samples. the importance of previously removing suspended matter, which could not be penetrated by the germicide, was emphasised by schwartz[8] although it had been previously noted by schumacher. at the royal testing station in berlin, numerous experiments on sewage chlorination were made by kranejuhl and kurpjuivut.[9] the results were judged by the _b. coli_ content, which was taken as an index of pathogenicity because this typical intestinal bacillus was found to be more frequent and less viable than the majority of the pathogenic organisms. other important work on this subject was carried out, in connection with the pollution of the hooghly river, by a bengal government commission in 1904; and by the state board of health of ohio in co-operation with the bureau of plant industry of the united states department of agriculture in 1907. the chlorination experiments of the latter were reported by kellerman, pratt, and kimberly.[10] the most valuable contribution to the disinfection of sewage was that of phelps,[11] who critically examined the work of previous experimenters and directed attention to the unnecessary stringent standards adopted in european practice. his work at boston in 1906, at red bank, n. j., and at baltimore in 1907, demonstrated in an indubitable manner the economic possibilities of sewage chlorination. the dosages necessary for crude sewage and filter effluents were indicated and also the necessary contact periods. this work marks the commencement of a new era in sanitary science. the first occasion on which chlorine compounds were first used for the disinfection of water cannot be definitely ascertained. it has been stated to the author that bleach was used for treating wells as early as 1850 but this treatment was apparently made without definite knowledge of the destruction of micro-organisms. in 1897, sims woodhead employed bleach solutions for the sterilisation of the distribution mains at maidstone, kent, subsequent to an epidemic of typhoid fever. the credit for the first systematic use of chlorine in water disinfection is due to a. c. houston with whom mcgowan was associated in the work carried out at lincoln in 1904-1905.[12] the reservoirs, filters, and distribution system, owing to flood conditions, became infected with typhoid bacilli which caused a severe epidemic amongst the consumers. the storage and purifications works were thoroughly treated with a solution of "chloros" (sodium hypochlorite containing approximately 10 per cent of available chlorine) which was regulated to give an approximate dosage of 1 part per million. the bacteriological results were entirely satisfactory but many complaints were received that the treatment had imparted a mawkish taste to the water. this was attributed to the action of the alkaline chloros on the organic impurities in the water. it was also stated that the water injured plants, fish, and birds and extracted abnormal amounts of tannin from tea but no substantiating evidence was produced in support of these complaints. houston made a continuous physiological test of the effect of the chlorinated water on small fish by suspending a cage of gold fish in the filter effluent chamber and also proved that the treatment had no appreciable effect on the plumbo-solvency of the supply. nesfield, of the indian army medical service,[13] reported in 1903 the results of numerous experiments on the destruction of pathogenic organisms by chlorine compounds and suggested their use in military work to prevent a recurrence of the appalling loss of life from water-borne diseases (especially enteric fever) such as took place during the boer war. nesfield proposed to use about 100 p.p.m. of available chlorine and to remove the excess after a contact period of 10 minutes. this work is especially interesting from the historical standpoint because it contains the first suggestion of the possibilities of compressed chlorine gas in steel cylinders. a few years later, electrolytic hypochlorite (oxychloride) was used at guildford by rideal and various chlorine compounds were tried on the water of the seine and vanne, in france, and at middlekerke and ostend, in belgium. experimental work on water chlorination was also reported by thresh and by moor and hewlett.[14] during the nineties many experiments on water chlorination were made by traube, sickenberger, kauffman, berge, bassenge, and others. traube[15] was able to completely sterilise water rich in bacteria in 2 hours by the addition of bleach equal to 1.06 p.p.m. of available chlorine. at the end of the contact period about 90 per cent of the added chlorine was unabsorbed and was destroyed by the addition of sodium bisulphite. bassenge[16] followed up the work of traube and that of sickenberger and kauffman, who had shown that it was possible to destroy cholera vibrio in nile water by means of sodium hypochlorite. bassenge used higher concentrations than traube and found it possible to destroy _b. typhosus_ and _b. coli_ in ten minutes with 60-90 p.p.m. of available chlorine. the excess was destroyed by adding calcium bisulphite. lode[17] experimented with waters seeded with _b. coli_, _b. typhosus_, and _b. tetani_ and found, contrary to traube, that 1-2 p.p.m. of chlorine did not sterilise in two hours. _b. coli_ was usually destroyed by 4 p.p.m. of chlorine in ten minutes and even better results were obtained with _b. typhosus_ and cholera vibrio: the former was destroyed in one hour by 1 p.p.m. and in ten minutes by 2 p.p.m.; the latter organism required 1-2 p.p.m. with a twenty-minute contact period. lode noted that organic matter lowered the bactericidal activity of chlorine and recommended the use of 30 p.p.m. of chlorine to ensure rapid and complete sterilisation. berge[18] used chlorine peroxide, generated by the action of hydrochloric acid on potassium chlorate, for the sterilisation of water and this process was afterwards used at ostend at a plant having a capacity of about 1,300,000 gallons per day. the dosage was equal to 0.53 p.p.m. of available chlorine and coke filters were used to destroy the excess although they were not found to be indispensable as the free chlorine disappeared spontaneously. this process appears to have been tried on the brussels supply and also for the treatment of a hospital supply at petrograd. the object of german sanitarians seems to have been to obtain practically instantaneous sterilisation of water for the use of travellers and troops in the field. until the commencement of the european war they did not have a high opinion of chlorination and generally regarded it as inefficient. schumberg[19] expressed the opinion that no chemical method of disinfection could be absolutely relied upon, under all circumstances, to prove fatal to bacteria. plucker[20] stated that several investigators, particularly schuder, had shown that chlorine, even in the proportion of 40 p.p.m. did not invariably destroy cholera vibrio and _b. typhosus_; and that with smaller doses the destruction was still less complete. he also stated that the bacteriological experiments of american workers were open to criticism and that they employed antiquated methods. by 1916 the german sanitarians appeared to have realised that their bacteriological standards were too stringent (langer[21]) and that the process had proved its value in an indisputable manner. european practice, in the comparatively few instances in which it has been used, has been to employ large doses of chlorine and to remove the excess by chemicals or by filtration through special media. in 1916, however, london commenced to chlorinate a portion of its supply and the following year practically the whole supply was chlorinated. a dosage of approximately 0.5 p.p.m. is used and the bleach solution is added to the pre-filtered water. worcester is also proposing to chlorinate the supply to maintain the purity of the water without extending the slow sand filtration plant. in north america, hypochlorite of soda and chlorine were used on the jewell filter at the louisville experimental station in about 1896 by george w. fuller and a year later they were used at adrian by jewell. the first commercial successful attempt was made by g. a. johnson. in 1908 the union stock yards company of chicago were proceeded against by the city of chicago regarding the condition of the effluent of the bubbly creek filter plant. copper sulphate had been previously used in conjunction with the filters but stock shippers complained that the water had a deleterious effect upon the animals consuming it. johnson eliminated the copper treatment and substituted bleach which was added seven and a half hours previous to filtration, with a dosage of 1.5 p.p.m. the results were very satisfactory. about the same time, johnson and leal commenced the treatment of the boonton supply of jersey city, n. j., consumed about 40 million gallons per day. the water was first treated with 36 pounds of bleach per million gallons (1.4 p.p.m. of available chlorine) but this quantity was gradually reduced until only 5 pounds per million gallons (0.2 p.p.m. of chlorine) were being used in april, 1909. the ability of the process to adequately purify water became the cause of a lawsuit and the decision of the court was: "from the proofs taken before me, of the constant observation of the effect of this device, i am of the opinion and find that it is an effective process which destroys in the water the germs, the presence of which is deemed to indicate danger, including the pathogenic germs, so that the water after this treatment attains a purity much beyond that attained in water supplies of other municipalities. the reduction and practical elimination of such germs from the water was shown to be substantially continuous. "upon the proofs before me, i find that the solution described leaves no deleterious substances in the water. it does produce a slight increase in the hardness but the increase is so slight as in my judgment to be negligible. "i do therefore find and report that this device is capable of rendering the water delivered in jersey city pure and wholesome, for the purposes for which it is intended and is effective in removing from the water those dangerous germs which were deemed by the decree to possibly exist therein at certain times."[22] during the next few years the use of hypochlorite in water purification, both alone and in conjunction with filtration, became very popular and in 1911 over 800 million gallons per day were treated in this manner. amongst the users were some of the largest cities in north america, including brooklyn, albany, and new york city, n. y., cincinnati and columbus, ohio, harrisburg, philadelphia, pittsburg, and erie, pa., hartford, conn., nashville, tenn., st. louis and kansas city, mo., montreal, p. q., toronto and ottawa, ont., baltimore, md., and minneapolis, minn. at present (1918) over 3,000 million gallons per day are being chlorinated in north america and more than 1,000 cities and towns are employing this process. bibliography [1] schwann. microskopische untersuchungen über die übereinstimmung in der textur und dem wachstum der tiere und pflanzen. berlin. 1839 [2] schroder and dusch. ann. der chem. u. pharm., 1854, 89, 232. [3] webster. the engineer. 1889, 67, 261. [4] mclintock. brit. med. jour., 1890, 11, 498. [5] eng. news. 1893, 30, 41. [6] eng. record. 1894, 29, 110. [7] proskauer and elsner. vierteljahresschr. ger. med. u. öff. sanitätswesen. 1898, 16, supp. heft. [8] schwartz. gas. eng., 1906, 29, 773. [9] kranejuhl and kurjuivut. mitteilungen aus der königlichen prüfungsanstalt für wasserversorgung und abwässerbeseitigung zu berlin, 1907, 9, 149. [10] kellerman, pratt, and kimberly. bull. 115, bur. plant ind., u. s. dept. of agr., 1907. [11] phelps. water supply paper 229, dept. of int., u. s. geo. survey. [12] houston and mcgowan. 5th rpt. royal commission on sewage disposal. [13] nesfield. public health. 1903, 15, 601. [14] moor and hewlett. rpt. of m. o. to l. g. b., 1909-10. [15] traube. zeit. f. hyg., 1894, 16, 149. [16] bassenge. zeit. f. hyg., 1895, 20, 227. [17] lode. archiv. f. hyg., 1895, 24, 236. [18] berge. rev. d'hyg., 1900, 22, 905. [19] schumburg. zeit. f. hyg., 1903, 45, 125. [20] plucker. j. gasbeleucht., 1911, 54, 385. [21] langer. zeit. f. hyg., 1916, 81, 296. [22] johnson. jour. amer. pub. health assoc., 1911, 1, 566. chapter ii modus operandi before considering the "modus operandi" of chlorine and hypochlorites, it will be advisable to take up the composition of the latter substances and particularly that of "bleach." bleach is manufactured by passing chlorine gas over slaked lime and the ensuing reactions are often represented by the equation ca(oh)_{2} + cl_{2} = caocl_{2} + h_{2}o. this represents the substance formed as a pure oxychloride of calcium which contains approximately 50 per cent of chlorine, but the article commercially produced never contains this amount of chlorine, the usual percentage being from 35-37. the general composition of commercial bleach is fairly uniform. this is shown in the following analyses of which two are of german bleach examined by lunge and one of canadian manufacture analysed by the author. -------------------------------+----------------+------- | lunge. | race. -------------------------------+--------+-------+------- | % | % | % available chlorine | 37.00 | 38.30 | 37.50 chlorine as chlorides | 0.35 | 0.59 | 0.52 chlorine as chlorates | 0.25 | 0.08 | 0.18 lime | 44.49 | 43.34 | 44.12 magnesia | 0.40 | 0.31 | 1.28 iron oxide | 0.05 | 0.04 | 0.11 alumina | 0.43 | 0.41 | 0.46 carbon dioxide | 0.18 | 0.31 | 0.22 silica | 0.40 | 0.30 | 0.52 water and undetermined | 16.45 | 16.32 | 15.09 -------------------------------+--------+-------+-------from these analyses the constitutional of commercial bleach might be represented by the formula 4caocl_{2}·2ca(oh)_{2}·5h_{2}o which assumes it to contain: 68.0 per cent of calcium hypochlorite, 20.0 per cent of calcium hydroxide, and 12.0 per cent of water. in this formula calcium hypochlorite has been written caocl_{2}, but this substance actually contains one atom of oxygen less than the true hypochlorite, which has the constitutional formula clo-ca-ocl. this difference led some of the earlier chemists to regard caocl_{2} as a mixture of equal molecules of calcium chloride and calcium hypochlorite (cacl_{2} + ca(ocl)_{2} = 2caocl_{2}), but it has been definitely established that no calcium chloride exists in the free state in dry commercial bleach. since the very earliest days when the process of bleaching was investigated it was considered to be a process of oxidation and it is not surprising that lavoisier and his pupils, who had noted the strong decolourising action of the gas discovered previously by scheele, should regard it as a compound that contained oxygen. they were confirmed in this view by the fact that an aqueous solution of the gas slowly evolved oxygen when placed in bright sunlight, and lost its bleaching properties. watt disproved this and showed that the evolution of oxygen was due to the action of the chlorine on water. cl_{2} + h_{2}o = 2hcl + o. the bleaching action was not due to the chlorine "per se" but to the nascent oxygen produced in the presence of moisture. later, when bleach and other chlorine compounds came into use as deodourisers, their action was attributed to the oxygen produced and when their germicidal properties became known it was natural to assume that the destruction of bacteria was due to the same cause. some of the earlier experimental work supported this view. fischer and proskauer[1] found that humidity played an important part in chlorine disinfection, probably because it favoured oxidation. in air saturated with moisture micro-organisms were killed by 0.3 per cent of chlorine in three hours but when the air was dry practically no action occurred. they concluded that chlorine was not directly toxic. warouzoff, winogradoff, and kolessnikoff[2] were unable to confirm the results of fischer and proskauer and found that a mixture of chlorine gas and air killed tetanus spores in one minute. the nascent oxygen hypothesis was clearly and succinctly expressed by prof. leal during the hearing of the boonton, n. j., case and the following abstracts have been taken from his evidence: "... that on the addition of bleach to water the loosely formed combination forming the bleach splits up into chloride of calcium and hypochlorite of calcium. the chloride of calcium being inert, the hypochlorite acted upon by the carbonic acid in the water either free or half bound, splits up into carbonate of calcium and hypochlorous acid. the hypochlorous acid in the presence of oxidisable matter gives off its oxygen; hydrochloric acid being left. the hydrochloric acid then drives off the weaker carbonic acid and unites with the calcium forming chloride of calcium. "that the process was wholly an oxidising one, the work being done entirely by the oxygen set free from the hypochlorous acids in the presence of oxidizable matter.... "we have used during our investigations, the term 'potential oxygen' as expressing its factor of power. when set free, it is really nascent or atomic oxygen and is, in its most active state, entirely different from the oxygen normally in water...." the reactions suggested are expressed in the following equations: (i). 2caocl_{2} = cacl_{2} + ca(ocl)_{2} (ii). ca(ocl)_{2} + co_{2} + h_{2}o = caco_{3} + 2hclo (iii). 2hclo = 2hcl + o_{2} (iv). caco_{3} + 2hcl = cacl_{2} + co_{2} + h_{2}o. phelps, during the hearing of this case, suggested that hypochlorites were directly toxic to micro-organisms but this view was not supported by any definite evidence and the nascent oxygen hypothesis met with almost universal acceptance. investigations made by the author in 1915, 1916 and 1917 have produced data which cannot be adequately explained by the nascent oxygen hypothesis.[3] the disinfecting action of bleach can be most conveniently considered by regarding it as a heterogeneous mixture of the reactants and resultants of the reaction cao + h_{2}o + cl_{2} <=> caocl_{2} + h_{2}o which is in equilibrium for the temperature and pressure obtaining during the process of manufacture. under suitable physical conditions the chlorine content can be increased to 40-42 per cent but such a product is not so stable as those represented by the analyses on page 14 and which contain approximately 20 per cent of excess hydrate of lime. the stability of bleach depends upon this excess of base (griffen and hedallen[4]) and although magnesia can be partially substituted for this excess of lime, a minimum of 5 per cent of free hydrate of lime is required to ensure stability. on dissolving bleach in water the first action is the decomposition of calcium oxychloride into an equal number of molecules of calcium hypochlorite and calcium chloride. 2caocl_{2} = ca(ocl)_{2} + cacl_{2}. in dilute solution these salts are dissociated and hydrolysis tends to occur in accordance with the equations 2ca(ocl)_{2} + 4h_{2}o <=> 2ca(oh)_{2} + hocl + hcl and cacl_{2} + 2h_{2}o <=> ca(oh)_{2} + 2hcl. calcium hydrate and hydrochloric acid are both practically completely dissociated, i.e. there is a large and equal quantity of h^{.} and oh', and the product is much greater than k_{_w_} (ionic product of water), and hence there is a combination of these ions, leaving the solution neutral and no undissociated acid or base exists. this statement is only approximately correct as hydrochloric acid is slightly more dissociated than calcium hydroxide (ratio 9:8) and the solution is consequently slightly acid, i.e. the h^{.} concentration is greater than 1 × 10^{-7}. hypochlorous acid is only very slightly dissociated, especially in the presence of the ocl' ion due to the dissociation of the ca(ocl)_{2}, as compared with ca(oh)_{2} and hydrolysis of the ca(ocl)_{2} proceeds with increased dilution. the action is best represented by the equation 2ca(ocl)_{2} + 2h_{2}o <=> cacl_{2} + ca(oh)_{2} + 2hocl the hydrolytic constant of hypochlorous acid has apparently not been determined but as the acid is weaker than carbonic acid, which has a hydrolytic constant of 1 × 10^{-4}, the value is probably between 1 × 10^{-3} and 1 × 10^{-4}. from the formula _x_^{2}/(1 _x_)_v_ = _k__{_wv_} in which 1 mole of pure ca(ocl)_{2} is dissolved in _v_ litres, _x_ is the fraction hydrolysed, and _k__{_wv_} is the hydrolytic constant, complete hydrolysis occurs (_x_ = 1) when _v_ is not greater than 1 × 10^{4} litres. this is equivalent to a concentration of not less than 7.1 p.p.m. of available chlorine. solutions of pure hypochlorites are alkaline in reaction because of the excess of hydroxyl ions (minimum concentration 1 × 10^{-4}). in solutions of bleach the hydrolytic action is retarded by the oh' due to the free base, and accelerated by the excess of h^{.} caused by the dissociation and partial hydrolysis of cacl_{2}; the final result is determined by the relative proportions and the effect of the free base usually preponderates. the addition of any substance that reduces the oh' concentration enables hydrolysis to proceed to completion and affords a rational explanation of the fact that solutions of bleach, on distillation with such weak acids as boric acid, yield a solution of hypochlorous acid. it also explains why the addition of an acid is necessary in bunsen's method (_vide_ p. 79) of analysing hypochlorite solutions. it has been stated that when hydrochloric acid is employed the increase in the oxidising power is due to the action of the acid upon calcium chloride but this never occurs under ordinary conditions; weak acids such as carbonic or acetic will give practically the same result as hydrochloric acid in solutions of bleach of the strength used in water treatment. the slightly higher result obtained with strong acids is due to the decomposition of chlorates. the effect of dilution alone is shown by the data given below. a 2 per cent bleach solution, containing very little excess base, was diluted with distilled water and the various dilutions titrated with thiosulphate after the addition of potassium iodide. in one series the solutions were titrated directly, and after acidification in the other. the results[a] were as follows: hydrolysis of bleach solution -----------------------------------+---------------------- strength of solution. grams bleach | direct titration × 100 per 100 c.cms. | --------------------. | acid titration -----------------------------------+---------------------- 2.0 | 30.8 0.2 | 34.3 0.1 | 41.8 0.02 | 67.5 0.002 | 100.0 -----------------------------------+---------------------- [a] corrected for the alkali produced by hclo + 2ki = kcl + koh + i_{2}. although every precaution was taken to exclude carbonic acid, a portion of the hydrolysis was probably due to this acid, which would remove calcium hydrate from the sphere of action and consequently alter the equilibrium. the above figures are only applicable to the particular sample used; other samples containing different excesses of base would yield different hydrolytic values. the results are in agreement with the hypothesis presented and confirm the theoretical deduction that very dilute bleach solutions are completely hydrolysed if no salts are present that will dissociate and increase the oh' concentration. hydrolysis is reduced by caustic alkalies and alkaline carbonates, and increased by acids and acid carbonates that reduce the oh' concentration. the effect of chlorides is anomalous and no adequate explanation for their action can be given at present. the addition of small quantities of sodium chloride (0.1 per cent) increases the hydrolysis of bleach solutions but much larger quantities tend to the opposite direction. the effect of these substances upon the velocity of the germicidal action of bleach solutions is in the same direction as the hydrolysing effect.[4] sodium chloride in quantities up to 10 parts per million has a very limited effect but larger quantities (90 p.p.m.) increase the velocity of the reaction. sodium chloride, in the absence of hypochlorites, was found to have no influence upon the viability of _b. coli_ in water. in quantities up to approximately 5 p.p.m., sodium hydroxide has but little influence; 5-10 p.p.m. reduce the velocity to a marked degree, but when the quantity of caustic is still further increased the germicidal action of the alkali commences to be appreciable and may nullify the retarding action on the hypochlorite. normal carbonates tend to reduce the velocity of the germicidal action and bicarbonates to increase it. sulphuric acid, even in very small quantities (5 p.p.m.), has a marked accelerating effect and the total effect produced is much greater than can be accounted for by the germicidal activity of the acid alone. weak acids such as carbonic acid and acetic acid are also effective accelerators. in one experiment a 0.01 per cent solution of bleach was found to be 40 per cent hydrolysed. by passing carbonic acid gas this was increased to 95 per cent and the velocity of the germicidal action of this solution was found to be approximately 100 per cent greater than that of the uncarbonated one. norton and hsu[5] have shown that the germicidal activity of some disinfectants is a function of the hydrogen ion concentration, but this factor is insufficient to account for the effect of acids on bleach solutions. the effect of sodium chloride on the bacteriological results, like that on the hydrolytic constant, is anomalous. similar effects have been observed on the addition of this salt to phenol and other disinfectants. the _raison d'être_ of the increased activity is obscure but it is possible that the salt renders the organisms more susceptible to the action of the germicide. ammonia, though decreasing the hydrogen ion concentration of bleach and other hypochlorite solutions, markedly increases the velocity of the reaction; chlorinated derivatives of ammonia (chloramines), which have a specific germicidal action, are formed. these will be discussed at length in chapter ix, p. 115. rideal[6] has shown that the addition of ammonia to sodium hypochlorite destroys the bleaching activity in acid solution. this has been found by the author to be also true for calcium hypochlorite (bleach). if the bleaching effect is due to oxidation, the oxidising power of hypochlorites must be considered to be destroyed by the addition of ammonia. the property of oxidising organic matter in water is also destroyed; this is well illustrated in table ii which shows the rate of absorption of chlorine and chloramine by the ottawa river water. the water used in this experiment contained 40 p.p.m. of colour and absorbed 9.5 p.p.m. of oxygen (30 mins. at 100° c.). table ii.[a] ------------------+------------------------------------------------ | absorption of available chlorine at 63° f. time of contact +----------------------+------------------------- minutes. | chlorine as bleach. | chlorine as chloramine. ------------------+----------------------+------------------------- nil. | 10.00 | 9.98 5 | 6.50 | 9.98 10 | 5.91 | 9.90 20 | 5.18 | 9.90 40 | 4.47 | 9.84 60 | 3.90 | 9.84 80 | 3.65 | 9.84 20 hours | .... | 9.68 ------------------+----------------------+------------------------- [a] results are parts per million. from a consideration of these and other experiments made by the author in january, 1916, it became apparent that the nascent oxygen hypothesis entirely failed to explain the results obtained, and that they must be attributed to a direct toxic action of the chlorine or chloramine. dakin et al.[7] arrived at a similar conclusion from a consideration of the results obtained during the use of hypochlorite solutions in the treatment of wounds by carrel's method of irrigation. they attributed the marked beneficial action to the formation of chloramines _in situ_ by the action of hypochlorous acid upon amino acids and proteid bodies. compound chloramines (chlorinated aminobenzoic acids) were prepared in the laboratory and found to give excellent results in reducing wound infection. later, other compounds were prepared for the purpose of sterilising small quantities of water for the use of mobile troops (see p. 128). rideal[6] was the first to note the strong germicidal power of chloramine and attributed the persistent germicidal activity of hypochlorites in sewage to the formation of chloramine and chloramine derivatives. further evidence against the nascent oxygen theory of chlorine disinfection is to be found in the fact that such active oxidising agents as sodium, potassium, and hydrogen peroxides have a much lower germicidal activity than chlorine when compared on the basis of their oxygen equivalents. table iii shows chlorine to be approximately five times as active as potassium permanganate when compared on this basis. table iii.[a]--comparison of bleach and potassium permanganate -----------+------------------+------------------ | bleach | |available chlorine| potassium contact | 0.35 p.p.m. | permanganate. period. +------------------+------------------ |oxygen equivalent. parts per million. +--------+---------+---------+-------- | 0.08 | 0.133 | 0.266 | 0.400 -----------+--------+---------+---------+-------- nil | 140 | ... | ... | ... 30 mins | 90 | 122 | 115 | 110 1 hour | 68 | 115 | 100 | 80 1-1/2 hours| 63 | 108 | 95 | 75 4 hours | 50 | 95 | 80 | 50 -----------+--------+---------+---------+-------- [a] results are _b. coli_ per 10 c.cms. the germicidal activity of oxidising agents has been shown by novey and others to be somewhat proportional to the energy liberated during the reaction but even when this factor is taken into consideration chlorine compounds are more active than other oxidising agents. hypochlorous acid is far superior to hydrogen peroxide as a germicidal agent and is as active as ozone, which liberates a greater amount of energy. 2hclo = 2hcl + o_{2} + 18,770 calories 2h_{2}o_{2} = 2h_{2}o + o_{2} + 46,120 calories 2o_{3} = 3o_{2} + 60,000 calories. again, solutions of chlorine gas and hypochlorites having the same oxidising activity, as determined by titration with thiosulphate after the addition of potassium iodide and acid, i.e. contain equal amounts of available chlorine, show approximately the same germicidal activity in water. on the addition of ammonia, the hypochlorite solutions retain their ability to liberate iodine from potassium iodide (wagner test) but the property of oxidising such dyestuffs as indigo is destroyed and the germicidal activity is increased. ammonia, when added to solutions of chlorine gas, diminishes the property of liberating iodine from potassium iodide, the bleaching effect on dyestuffs, and the germicidal action. it is often assumed that chlorine forms hypochlorous acid on solution in water cl_{2} + h_{2}o = hclo + hcl but the results obtained on the addition of ammonia indicate that either very little hypochlorous acid is formed or that ammonia and hypochlorous acid do not form chloramine in the presence of hydrochloric acid. when chlorine gas was treated with a 0.5 per cent solution of ammonia in the proportion of 1 molecule of chlorine to 1.90-1.95 molecules of ammonia, noyes and lyon[8] found that nitrogen and nitrogen-trichloride were formed in equimolar quantities. 12nh_{3} + 6cl_{2} = n_{2} + ncl_{3} + 9nh_{4}cl. bray and dowell[9] showed that this reaction depended upon the hydrogen ion concentration and proceeded in accordance with the following equations: (i). acid solution 4nh_{3} + 3cl_{2} = ncl_{3} + 3nh_{4}cl (ii). alkaline solution 8nh_{3} + 3cl_{2} = n_{2} + 6nh_{4}cl. in (i) with a ratio of chlorine to ammonia of 3:1 by weight, one-half of the chlorine is lost as ammonium chloride and one-half forms nitrogen trichloride, concerning which comparatively little is known; in (ii) the whole of the chlorine forms ammonium chloride, which has no germicidal value. the effect of ammonia on the germicidal action of a solution of chlorine gas is shown in the table iv. table iv.[a]--effect of ammonia on chlorine gas solution _conditions._ colour of water 40 p.p.m. turbidity, 5 p.p.m. ---------+--------------------------------------- |available chlorine 0.20 p.p.m., ammonia. contact | parts per million. period. +---------+---------+----------+-------- | nil. | 0.05 | 0.10 | 0.20 ---------+---------+---------+----------+-------- nil. | 130 | ... | ... | ... 10 mins. | 135 | 140 | 130 | 135 1 hour | 130 | 130 | 128 | 120 4 hours | 120 | 112 | 110 | 105 24 hours | 120 | 145 | 160 | 170 ---------+---------+---------+----------+-------- [a] results are _b. coli_ per 10 c.cms. even when the ratio of cl:nh_{3} was 4:1 by weight, practically the same as was used in the experiments of noyes and lyon, and bray and dowell, quoted above, the germicidal action was totally destroyed and the 24-hour results showed aftergrowths which were somewhat proportional to the amount of ammonia added. this was probably due to the formation of ammonium chloride, which provided additional nutriment for the organisms. it has often been assumed that hypochlorite solutions are decomposed on addition to water containing free or half-bound carbonic acid with the production of free chlorine, but no evidence has been adduced in support. free chlorine can be separated from hypochlorous acid in aqueous solution by extraction with carbon tetrachloride and when this solvent is shaken with a carbonated hypochlorite solution it is found that only traces of chlorine are removed. hypochlorous acid reacts with hydrochloric acid with the evolution of free chlorine hclo + hcl = cl_{2} + h_{2}o but in very dilute solution the amount of free chlorine formed is exceedingly minute. jakowkin[10] has shown that this reaction does not proceed to completion and that the concentration of free chlorine can be calculated from the equation hclo × h^{.} × cl' = 320cl_{2} in which the reactions are expressed in gram molecules per litre. the hydrogen ions and chlorine ions are obtained from the dissociation of carbonic acid (h_{2}co_{3} <=> h^{.} + hco_{3}') and chlorides (nacl <=> na^{.} + cl') and also by the dissociation of hydrochloric acid produced by the interaction of hypochlorous acid and organic matter. hclo = o + hcl <=> h^{.} + cl'. if the formula of jakowkin can be correctly applied to solutions containing fractions of a part per million of hypochlorous acid the free chlorine liberated by the addition of 1 p.p.m. of bleach to a water low in chlorides would be of the order 10^{-7}-10^{-8} p.p.m. _sodium hypochlorite_ is probably hydrolysed in dilute solution in a manner similar to that of bleach. 2naocl = nacl + naoh + hclo. for solutions containing equal amounts of available chlorine, electrolytic sodium hypochlorite is more dissociated than bleach because of the absence of an excess of base, and this, together with the presence of sodium chloride, accounts for the slightly higher germicidal velocity obtained. the experience of pulp mills, with bleach and electrolytic hypochlorites, confirms this: the latter is a much quicker bleaching agent than bleach and it is often so rapid as to make it desirable to reduce the velocity by the addition of soda ash. regarding hypochlorite solutions a phenomenon of more scientific interest than of practical importance has been noted by breteau[12] who found that alkaline solutions of sodium hypochlorite containing 0.94 per cent of available chlorine lost 3.6 per cent of their titer on dilution with 80 volumes of water; also that this loss was increased by the addition of small quantities of salt (sodium chloride) and more so by carbonates and bicarbonates. the author has noted similar losses on diluting bleach solutions and that the loss increased on standing. the loss can be explained by the decomposition of hypochlorous acid, in the presence of light, into hydrochloric acid and oxygen. 2hclo = 2hcl + o_{2} chlorine water. when a solution of chlorine in water is used as a germicide the chemical reactions that occur differ materially from those of hypochlorite solutions. on solution in water, hydration or solvation probably takes place with the production of heat. cl_{2}·aq. = 2,600 calories. chlorine water is comparatively stable but decomposes under the influence of light in accordance with the equation cl_{2} + h_{2}o = 2hcl + o; a similar reaction occurs in the presence of organic matter or any substance capable of oxidation. chlorine water contains only minute traces of hypochlorous acid and there is no evidence that the endothermic reaction cl_{2}·aq + h_{2}o = hclo·aq + hcl·aq -2600 68,460 = -29,930 39,315 1815 occurs in a measurable degree. from thermochemical considerations hypochlorous acid and chlorine water should be about equally active as oxidising agents. 2hclo·aq = 2hcl + o_{2} + 18,770 calories 2cl_{2}·aq + 2h_{2}o = 2hcl + o_{2} + 15,340 calories 2cl_{2}· + aq + 2h_{2}o = 2hcl + o_{2} + 20,540 calories when a solution of chlorine or hypochlorite is added to water as a germicidal agent, a variety of reactions occur the character of which is determined by the nature of the mineral and organic matter in the water and the type of chlorine compound added. the general reactions are of three types (1) oxidation of the organic matter, (2) direct chlorination of the organic matter, and (3) a bactericidal action. in the treatment of waters that contain appreciable amounts of organic matter almost all the chlorine is consumed in reaction (1) and even with filter effluents it is probably true that oxidation accounts for the greater portion of the chlorine consumed. the author has found that a dosage of 0.02 part per million of available chlorine was more effective in destroying _b. coli_ in distilled water than 0.40 p.p.m. in a water absorbing 9.5 p.p.m. of oxygen (30 mins. at 100° c.). reaction (1) can be adequately explained by the nascent oxygen hypothesis and it is this reaction that determines the dosage required for effective sterilisation. (see chap. iii.) very little information is available regarding reaction (2) but there is little doubt that a direct chlorination of the organic matter does occur and it is more than probable that these chlorinated derivatives are largely responsible for the obnoxious tastes and odours produced in some waters. it has been suggested that these were due to the formation of chloramines. this view was formerly supported by the author but the chloramine treatment at ottawa and other places has demonstrated the inadequacy of this explanation. it is true that the odour of chloramine is stronger and more pungent than that of chlorine, but chloramine in the ottawa supply, even with doses as high as 0.5 part per million of available chlorine, has caused no complaints. the odour of some of the organo-chloro compounds is more penetrating and obnoxious than those of chlorine and chloramine, and it is quite possible that some of the higher homologues of chloramine are in this class. it should be noted, however, that some of the chloro-amido compounds prepared by dakin are white, odourless, crystalline substances. practically nothing is known regarding the specific nature of the mechanism involved in reaction (3). the hypothesis that chlorine, and chlorine compounds, exert a direct toxic action on the micro-organisms marks an advance in the science of water treatment but does not indicate the physiological processes involved. cross and bevan[11] have shown that chloro-amines have a tendency to combine with nitrogenous molecules and to become fixed on cellulose; it is therefore possible that reaction is a cytolytic one in which the chlorine attacks and partially or wholly destroys the membranous envelope of the organisms. a portion of the chlorine or chlorine-compound may also penetrate the membrane and produce changes that result in the death of the organism. bibliography [1] fischer and proskauer, rev. d'hyg., 1884, 6, 515. [2] warouzoff, winogradoff, and kolessnikoff. russkaia medicina, 1886, nos. 3 and 32. [3] race. jour. amer. water works assoc., 1918, 5, 63. [4] griffen and hedallen. jour. soc. chem. ind., 1915, 34, 530. [5] norton and hsu. jour. inf. dis., 1916, 18, 180. [6] rideal, s. jour. roy. san. inst., 1910, 31, 33. [7] dakin, cohen, duafresne, and kenyon. proc. roy. soc., 1916, 89b, 232. [8] noyes and lyon. jour. amer. chem. soc., 1901, 23, 460. [9] bray and dowell. jour. amer. chem. soc., 1917, 39, 905. [10] jakowkin. zeit. f. phys. chim., 1899, 19, 613. [11] cross and bevan. jour. soc. chem. ind., 1898, 28, 260. [12] breteau. jour. pharm. chim., 1915, 12, 248. chapter iii dosage the amount of chlorine required for efficient treatment is very largely determined by the amount required to satisfy the oxidisable matter present in the water. many experimenters have reported results that would indicate that appreciable concentrations of chlorine are required for bactericidal action but the details of the technique, as published, show that the effect of the organic matter added with the test organism was not thoroughly appreciated. one cubic centimetre of a culture in ordinary peptone water, added to one litre of water, would increase the organic content by approximately 10 parts per million, an amount that would absorb appreciable amounts of chlorine. other conditions also make it very difficult to compare the results obtained in the past: one of these is the degree of purity set as the objective. german bacteriologists added enormous numbers of the test organism and endeavoured to obtain the complete removal of the organism from such quantities as one litre of water with a contact period often as short as 10 minutes. nissen,[1] of the hygienic institute of berlin, found that a 1: 800 dilution of bleach (420 p.p.m. of chlorine) was required to destroy _b. typhosus_ in one minute and a 1:1600 dilution (210 p.p.m. of chlorine) in 10 minutes. delépine[2] obtained somewhat similar results by means of the thread method for testing disinfectants. phelps,[3] using gelatine plates for enumeration of the bacteria, obtained a 90 per cent reduction of _b. typhosus_ in twenty minutes with 5 p.p.m. of available chlorine; over 99 per cent reduction in one hour, and over 99.99 per cent reduction in 18 hours. wesbrook, whittaker, and mohler[4] tested bleach solutions with various strains of _b. typhosus_ by means of the plate method and found that the most resistant one was reduced from 20,000 per c.cm. to sterility (in 1 c.cm.) by 3 p.p.m. of available chlorine in fifty minutes and that the least resistant one only required 1.0 p.p.m. with a thirty minutes' contact. lederer and bachmann[5] have reported the following results: table v percentage reduction, 15 minutes' contact ----------+------------------------------------------------------ | nature of test organism. +-------+-------+-------+-------+-------+-------+------ available | | b. | | | | b. | chlorine | b. |fæcalis| b. |proteus| b. |lactis | b. p.p.m. |cloacæ.|alkali-|paraty-| mira|enter| aero|choler[oe] | |genes. |phosus.|bilis. |itidis.| genes |suis. ----------+-------+-------+-------+-------+-------+-------+------ 0.1 | .....| 99.98| .....| 27.3 | .....| .....| ..... 0.2 | 99.69| 99.99| 99.97| 45.5 | 99.83| 99.17| 95.8 0.3 | 99.75| 100.00| 100.00| 63.7 | 99.98| 99.98| 100.0 0.5 | 100.00| .....| .....| 72.7 | 100.00| 100.00| ..... 0.7 | .....| .....| .....| 63.7 | .....| .....| ..... 1.0 | .....| .....| .....| 63.7 | .....| .....| ..... 3.0 | .....| .....| .....| 90.9 | .....| .....| ..... 5.0 | .....| .....| .....| 90.0 | .....| .....| ..... original }| | | | | | | number of}| | | | | | | organisms}|160,000| 9,500| 3,000| 8,000 |180,000|180,000| 500 per c.cm.}| | | | | | | ----------+-------+-------+-------+-------+-------+-------+------with the exception of _p. mirabilis_, which forms endospores, all the organisms were killed (less than 1 per c.cm.) by 0.5 p.p.m. of available chlorine in fifteen minutes. all these observers found that _b. coli_, the organism usually employed as an index of contamination, had approximately the same degree of resistance to chlorine as _b. typhosus_, though wesbrook et al. directed attention to the varying viability of organisms derived from different sources. these experiments merely indicate the dosage required for exceptional conditions such as it is inconceivable would ever occur in water-works practice. no information is available regarding the actual _b. typhosus_ content of waters that have caused epidemics of typhoid fever, but for the present purpose it may be assumed that the extreme condition would be a pollution by fresh sewage giving a _b. coli_ content of 1,000 per c.cm. or 200 times worse than the average condition that can be satisfactorily purified without overloading a filter plant (500 _b. coli_ per 100 c.cms.). experiments made by the author indicate that a suspension of 1,000 _b. coli_ per c.cm. in water, in the absence of organic matter, can be reduced to a 2 _b. coli_ per 100 c.cms. standard (the u.s. treasury standard) by 0.1 p.p.m. of available chlorine in ten minutes at 65° f. this experiment indicates the amount of chlorine that is required for the bactericidal action only; such a dosage could never be used in practice to meet a pollution of this degree because of the accompanying organic matter. in actual practice the author has experienced the above condition but once, and on that occasion the _b. coli_ were derived from soil washings and not from fresh sewage. the amount of chlorine required for germicidal action is small, and the main factors that determine the dosage necessary to obtain this action are (1) the content of readily oxidisable organic matter, (2) the temperature of the water, (3) the method of application of the chlorine and (4) the contact period. =oxidisable matter.= the oxidisable matter may be divided into two classes (_a_) inorganic and (_b_) organic. the inorganic constituents naturally found in water, that are readily oxidisable, are ferrous salts (usually carbonates), nitrites, and sulphuretted hydrogen, and these react quantitatively with chlorine until fully oxidised. the oxygen value of chlorine is approximately one-quarter (actually 16: 71) the available chlorine content in accordance with the equation cl_{2}/71 + h_{2}o = 2hcl + o/16. one part per million of available chlorine will oxidise 1.58 p.p.m. of ferrous iron; 0.197 p.p.m. of nitrous nitrogen; and 0.479 p.p.m. of sulphuretted hydrogen. table vi.[a]--effect of colour temperature 63° f. ----------------+--------------------+-------------------- | water "a" colour 3 | water "b" colour 40 | available chlorine | available chlorine contact period. | p.p.m. | p.p.m. +--------------------+------+------+------ | 0.2 | 0.2 | 0.4 | 0.5 ----------------+--------------------+------+------+------ nil | 194 | 194 | 194 | 194 5 minutes | 121 | 165 | 129 | 66 1 hour | 7 | 95 | 20 | 1 5 hours | 0 | 4 | 0 | 0 24 hours | 0 | 1 | 1 | 0 48 hours | 0 | 0 | 0 | 0 ----------------+--------------------+------+------+------ [a] results are _b. coli_ per 10 c.cms. of water. the organic matter found in water may be derived from various substances such as urea, amido compounds, and cellulose; humus bodies derived from soil washings and swamps may also be present. the humus compounds of swamps and muskeg are usually associated with the characteristic colour of the water derived from these sources. the effect of this coloured organic matter upon the chlorine dosage is well illustrated in table vi. in this experiment _b. coli_ was used as the test organism and the only varying factor was the organic matter. to obtain the same result with a contact period of one hour at 63° f. it was necessary to use about two and one-half times the amount of chlorine with a water containing 40 p.p.m. of colour as with one practically free from colour. it will be noted that water "a," in which the colour had been reduced to 3 p.p.m. by coagulation with aluminium sulphate, required a greater dosage of chlorine than was necessary for bactericidal action only. this was due to a residual organic content which produced none or but a trace of colour, for although the colour had been reduced by 92 per cent the organic matter, as measured by the oxygen absorbed test, had only been reduced by 70 per cent. the results obtained by harrington[6] at montreal are in the same direction. during the greater part of the year the water is obtained from the st. lawrence river, which is colourless and low in organic matter; in the spring months the flood waters of the ottawa, a highly coloured river, enter the intake and necessitated a much higher dosage. chlorine treatment at montreal -------------+--------+-------+--------+---------+----------+-------- | | | oxygen | chlorine| | source of | alkali-|colour.|absorbed| required| bacteria | per cent supply. | nity. | | (30 | p.p.m. | per c.cm.| removed. | | | mins.) | | | -------------+--------+-------+--------+---------+----------+------- ottawa river | 15-20 | 50-70 | 14.0 | 1.50 | 3,000 | over 98 st. lawrence | | | | | | river | 90-100 | nil. | 0.30 | 0.30 | 500 | over 99 -------------+--------+-------+--------+---------+----------+--------ellms[7] obtained similar results and reported "that the rate at which sterilisation proceeds varies, in a general way, directly with the concentration of the applied available chlorine and the temperature, and inversely as the amount of easily oxidisable matter present." experience with filter plants shows the same facts, the amount of chlorine required for the sterilisation of a filter effluent being invariably less than that necessary to purify the raw water to the same extent. the effect of coloured organic matter upon the absorption of chlorine, in the form of hypochlorite, is shown on diagram i. [illustration: diagram i effect of colour on absorption of chlorine by water +-------------------------------+----------------------------+ | | value of k calculated from | | | | | absorption of chlorine | log(n_{1}/n_{2}) | | by water at 63° f. | k = ---------------- | | | _t__{2} _t__{1} | | | | +-------+ +-------+ when _t__{1} = 0 | |time of+-----------------------+time of+--------------------+ |contact| colour of water |contact| colour | | in +-------+-------+-------+ in +------+------+------+ |minutes| 3 | 25 | 40 |minutes| 3 | 25 | 40 | +-------+-------+-------+-------+-------+------+------+------+ | nil | 10.00 | 10.00 | 10.00 | | | | | | 5 | 9.62 | 7.70 | 6.50 | 5 |0.0033|0.0227|0.0374| | 10 | 9.41 | 7.03 | 5.91 | 10 |0.0026|0.0153|0.0228| | 20 | 9.17 | 6.40 | 5.18 | 20 |0.0018|0.0096|0.0190| | 40 | 8.95 | 5.82 | 4.47 | 40 |0.0012|0.0057|0.0087| | 60 | 8.85 | 5.63 | 3.90 | 60 |0.0008|0.0041|0.0068| | 80 | 8.80 | 5.58 | 3.65 | 80 |0.0007|0.0032|0.0056| +-------+-------+-------+-------+-------+------+------+------+] the shape of the curve obtained with a colour of 40 p.p.m. somewhat resembled that of a mono-molecular reaction and the results were calculated accordingly. the mathematical expression of this law is _dn_/_dt_ = _kn_ where _n_ is the concentration of the available chlorine in parts per million. integrating between _t__{1} and _t__{2} the formula _k_ = log(_n__{1}/_n__{2})/(_t__{2} _t__{1}) is obtained. if the compound absorbing the chlorine were simple in character, and the chlorine were present in large excess, the value of _k_ would be constant. in the experiments recorded, _k_ constantly decreases, due to the decreasing concentrations of the reacting substances and the complex nature of the organic matter. the results show the effect of organic matter on the reduction of the chlorine concentration available for germicidal action and also the importance of avoiding a local excess of chlorine (_vide_ p. 41). an effort has been made by some observers to find a quantitative relation between the organic matter, expressed as oxygen absorbed in parts per million, and the chlorine required for oxidation, but without definite result. some of the results obtained are given in table vii. table vii.--oxygen to chlorine ratio -------------------------+------------------------ | oxygen absorbed observer. | ratio -----------------. | chlorine absorbed -------------------------+------------------------ rouquette | 1 bonjean | 0.5 orticoni | less than 1 valeski and elmanovitsch | 0.4 race | 0.4 theoretical | 0.22 -------------------------+------------------------the value of 0.4 (0.39) obtained by the author is the average of over one hundred determinations covering a period of two years. the experiments of zaleski and elmanovitsch were made with the water of the neva river. the divergence in the ratios affords additional evidence in favor of reaction (2) mentioned on page 28 and also shows that the chlorinated compounds are less readily oxidized than those from which they are produced. heise[8] has found that the amount of chlorine consumed is usually proportional to the concentration in which it is added though not necessarily a function of the concentration of the organic matter. =temperature.= the evidence regarding the effect of temperature upon the dosage required is somewhat conflicting. ellms (_vide supra_) found that the velocity of the germicidal action varied directly with the temperature and this has also been the author's experience with laboratory experiments. typical examples of these are given in tables viii and ix. table viii.[a]--effect of temperature available chlorine 0.4 part per million ---------------+-------------------------------- |temperature, degrees, fahrenheit. contact period.+-----------+----------+--------- | 36 | 70 | 98 ---------------+-----------+----------+--------- nil | 424 | 424 | 424 5 minutes | 320 | 280 | 240 1.5 hours | 148 | 76 | 12 4.5 hours | 38 | 14 | 3 24 hours | 2 | 0 | 0 48 hours | 2 | 0 | 0 ---------------+-----------+----------+--------- [a] results are _b. coli_ per 10 c.cms. table ix.[b]--effect of temperature available chlorine 0.2 parts per million ---------------+-------------------------------- |temperature, degrees, fahrenheit. contact period.+-----------+----------+--------- | 36 | 70 | 98 ---------------+-----------+----------+--------- nil | 240 | 240 | 240 5 minutes | 240 | 250 | 235 1 hour | 245 | 235 | 195 4 hours | 215 | 190 | 170 24 hours | 143 | 130 | 115 48 hours | 130 | 59 | 19 72 hours | ... | 28 | ... 96 hours | ... | 16 | ... 120 hours | ... | 6 | ... ---------------+-----------+----------+--------- [b] results are _b. coli_ per 10 c.cms. the reaction velocity of a germicide is proportional to the temperature[9] and the influence of temperature may be mathematically expressed by the formula _k__{1}/_k__{2} = _[theta]_(_t__{2} _t__{1}), in which _k__{1} and _k__{2} are the constants of the reaction at temperatures _t__{2} and _t__{1}, respectively, and _[theta]_ is the temperature coefficient. from the value of _[theta]_, the velocity constant of a germicide for any temperature may be calculated from the equation _k__{_t_} = _k__{20}° × _[theta]_^{(_t_ _t__{20}°)}. _k__{1} and _k__{2} are obtained from the formula _k__{_t_} = log(_n__{1}/_n__{2})/(_t__{2} _t__{1}) in which _n__{1} _n__{2} is the number of bacteria destroyed in the interval _t__{2} _t__{1}. a reduction of temperature also lowers the oxidizing activity of the chlorine so that a greater concentration is available for germicidal action. this is shown by the results plotted in diagram ii. [illustration: diagram ii effect of temperature on absorption of chlorine by water +----------------------------+----------------------------------+ | | value of k calculated from | | | absorption at 63° f. | | absorption of chlorine by | | | water containing 40 p.p.m. | log(n_{1}/n_{2}) | | of colour | k = ---------------- | | | _t__{2} _t__{1} | +-------+--------------------+ | |time of|temperature of water+-------+--------+--------+--------+ |contact+--------------------+_t__{2}|_t__{1} |_t__{1} |_t__{1} | |minutes|32° f.|46° f.|63° f.|minutes| = 0 | = 5 | = 10 | +-------+------+------+------+-------+--------+--------+--------+ | nil |10.00 |10.00 |10.00 | | | | | | 5 | 8.00 | 7.45 | 6.50 | 5 | 0.0374 | --- | --- | | 10 | 7.23 | 7.09 | 5.91 | 10 | 0.0228 | 0.0082 | --- | | 20 | 7.00 | 6.60 | 5.18 | 20 | 0.0190 | 0.0066 | 0.0057 | | 40 | 6.42 | 6.05 | 4.47 | 40 | 0.0087 | 0.0043 | 0.0040 | | 60 | 6.22 | 5.60 | 3.90 | 60 | 0.0068 | 0.0040 | 0.0036 | | 80 | 6.13 | 5.40 | 3.65 | 80 | 0.0056 | 0.0033 | 0.0029 | +-------+------+------+------+-------+--------+--------+--------+] tables viii and ix, however, show that the temperature coefficient of the germicidal action has a greater effect than the reduction in the amount of chlorine absorbed and removed from the reaction. the results obtained on the works scale with these waters are very different to the laboratory ones and show that more chlorine is required during the summer season than in winter. the results with bleach and liquid chlorine are in the same direction (_vide_ diagrams iii and iv). the bleach was regulated so as to maintain a constant purity, whilst in the other case the dosage was constant with a varying _b. coli_ content. in diagram iv the _b. coli_ is plotted; this does not represent all the factors involved as the _b. coli_ content of the treated water is also a function of that of the raw water, but in the example given this factor is of no moment because it was comparatively constant during the period plotted (extreme variation 80 per cent). the discrepancies between the laboratory and works results cannot be easily explained. the only difference in the conditions is the nature of the containing vessel. glass is practically inert at all temperatures but the iron pipes, through which the water passed before the samples were taken, may exert an absorptive influence on the chlorine at the higher temperatures experienced during the summer months. waters containing organic matter that differs much in quantity from the examples above may yield very different results and no generalisation can be made that will cover all cases. an increase of temperature increases the germicidal velocity and also the rate of absorption of chlorine by the organic matter; other factors determine which of these competitive actions predominates. =method of application (admixture).= a thorough admixture of the water and chlorine is a _sine qua non_ for successful operation. this should, if possible, be attained by natural means, but if there is any doubt as to the efficiency of the mixing process, mechanical appliances should be utilised. pumps, especially centrifugal pumps, constitute a very convenient and efficacious method of mixing the germicide and the water, and the solutions should never be injected into the discharge pipes when it is possible to make connections with the suctions. [illustration: diagram iii effect of temperature] [illustration: diagram iv effect of temperature] inefficient admixture leads to local concentration of the chlorine, a condition which (_vide_ p. 35), results in a wastage of the disinfectant. two practical examples of this effect may be cited. in one case the water was free from colour and contained very little organic matter. this water was chlorinated at one plant by allowing the bleach solution to drop into one vertical limb of a syphon approximately 6,000 feet long, the other vertical limb being used as a suction well for the pumps which discharged into the distribution mains. at the other plant the bleach solution was injected into the discharge pipe of a reciprocating pump through a pipe perforated with a number of small holes. the results for two typical months are given in table x. table x.--effect of efficient mixing ------+-----------+-----------------------+-------------- | available | bacteria per c.cm. | | chlorine +-----------------------+ | parts per | | | b. coli index month.| million. | raw |treated water. | per 100 c.cms. +-----+-----+ water.+-------+-------+-------+------ | a. | b. | | a. | b. | a. | b. ------+-----+-----+-------+-------+-------+-------+------ july | 0.20| 0.25| 864 | 27 | 93 | <0.2 | 8.5 august| 0.20| 0.27| 1.108 | 12 | 120 | <0.2 | 10.2 ------+-----+-----+-------+-------+-------+-------+------ a = efficient mixing. b = inefficient mixing. the results with the "b" plant were very irregular. the hypochlorite and water did not mix thoroughly and, as several suctions pipes were situated in the suction shaft, there was no subsequent admixture in the pumps; this also caused complaints regarding taste and odour but the complaints were localised, and not general as would result from an overdose of solution due to irregularities at the plant. the second example deals with a water containing 40-45 p.p.m. of colour. this supply was taken from the river by low-lift pumps and discharged into a header which was connected with the high-lift pumps by two intake pipes about 5,000 feet in length. during 1914 a baffled storage basin of two hours capacity was constructed and in june the hypochlorite was added at the inlet to this basin by means of a perforated pipe. the object was to increase the contact period prior to the delivery of the water into the header. the results for this month were as follows: available chlorine 1.88 parts per million ------------------------+-------------------------+--------- | bacteria per c.cm. agar.| +------------+------------+ b. coli. | 3 days at | 1 day at | index | 20 c. | 37 c. | per c.cm. ------------------------+------------+------------+--------- raw water | 410 | 104 | 0.280 treated water | 49 | 26 | 0.036 percentage purification | 88.2 | 75.0 | 87.5 ------------------------+------------+------------+---------during august the point of application of the hypochlorite was changed from the inlet of the basin to the suctions of the pumps and the solution proportioned to the amount of water pumped by the starch and iodide test. the average of the daily tests for this month were: available chlorine 1.55 parts per million ------------------------+-------------------------+----------- | bacteria per c.cm. agar.| +------------+------------+ b. coli. | 3 days at | 1 day at | index | 20 c. | 37 c. | per c.cm. ------------------------+------------+------------+--------- raw water | 448 | 100 | 0.600 treated water | 26 | 12 | 0.005 percentage purification | 91.9 | 88.0 | 99.2 ------------------------+------------+------------+---------here again thorough admixture produced better results than inefficient admixture plus a longer contact period. langer[10] has also noted the effect of local concentration and found that the disinfecting action is increased by adding the bleach solution in fractions, a cumulative effect replacing that of concentration. the importance of the admixture factor was not thoroughly appreciated during the earlier periods of chlorination but later installations, and particularly the liquid chlorine ones, have been designed to take full advantage of it. the point of application in american water-works practice varies considerably (longley[11]). in 57 per cent of those cases in which it is employed as an adjunct to filtration, it is used in the final treatment; in 26 per cent it is used after coagulation or sedimentation and before filtration; in the remaining 17 per cent it is applied before coagulation and filtration. the report of the committee adds: "the data at hand do not give any reasons for the application before coagulation. in general, an effective disinfection may be secured with a smaller quantity of hypochlorite, if it is applied after rather than before filtration. it should be noted that the storage of chlorinated water in coagulating basins, and its passage through filters, tend to lessen tastes and odors contributed by the treatment and this fact may in some cases account for its use in this way." =contact period.= other things being equal, the efficiency of the treatment will vary directly, within certain limits, with the contact period. when a chlorinated water has to be pumped to the distribution mains directly after treatment, the dosage must be high enough to secure the desired standard of purity within twenty to thirty minutes. the chlorine is sometimes not completely absorbed in this period and may cause complaints as to tastes and odours. the examples given above show that the lack of contact period can be largely compensated by ensuring proper admixture. experience has amply demonstrated that there is no necessity to use heroic doses for water that is delivered for consumption almost immediately after treatment, and that, with proper supervision, complaints can be almost entirely prevented. the general effect of the effect of contact period is shown in tables viii and ix on page 37. another example of a coloured water is given in table xi, whilst table xii shows the results obtained with a colourless water. table xi.[a]--effect of contact period -----------------+------------------------------ | chlorine, parts per million. contact period. +-------+-------+-------+------ | 0.30 | 0.40 | 0.55 | 1.21 -----------------+-------+-------+-------+------ nil | 3,800 | ... | ... | ... 1 minute | 1,400 | 120 | 0 | 0 10 minutes | 720 | 5 | 0 | 0 20 minutes | 35 | 0 | 0 | 0 -----------------+-------+-------+-------+------ [a] results are _b. coli_ per 10 c.cms. table xii.--effect of contact period available chlorine 0.27 part per million -----------------+--------------------------------+------------------ | sampling point. | bacteria per c.cm. -----------------+--------------------------------+------------------ average of series| 5,000 ft. from pumping station| 300 of samples | 6,000 " " " " | 203 | 7,000 " " " " | 103 | 12,000 " " " " | 86 | 14,000 " " " " | 87 -----------------+--------------------------------+------------------table xiii is taken from the work of wesbrook et al.[4] table xiii.[b]--treatment of mississippi river water aug. 8, 1910 -------------+------------------------------------------------ | contact period. (temp. 22°-26° c.). available cl.+---------+---------+---------+---------+-------- p.p.m. | | 1 hr. | | 6 hrs. | | 30 mins.| 30 mins.| 3 hrs. | 30 mins.| 24 hrs. -------------+---------+---------+---------+---------+-------- 0 | 230,000 | 200,000 | 160,000 | 150,000 | 140,000 0.5 | 14,000 | 7,400 | 2,000 | 6,000 | 11,000 1.0 | 20 | 14 | 170 | 450 | 60,000 1.5 | 10 | 6 | 16 | 45 | 70,000 2.0 | 7 | 8 | 10 | 97 | 70,000 2.5 | 7 | 14 | 30 | 116 | 65,000 3.0 | 6 | 12 | 5 | 12 | 16,500 -------------+---------+---------+---------+---------+-------- [b] results are bacteria per c.cm. in tables viii, ix, xi, and xii, the bacteria decreased constantly with increase of contact period, but the results in table xiii show that no advantage was to be gained by prolonging the contact beyond three hours; after this period the bacteria commenced to increase in number and when twenty-four hours had elapsed the number approached the original. this increase in the bacteria is technically known as "aftergrowth" and will be discussed more fully in chapter iv. the replies to queries sent out by the committee on water supplies of the american public health association[11] indicate that the contact period after treatment varies considerably in american water-works practice. forty per cent of the replies indicated no storage after treatment; 18 per cent less than one hour; 9 per cent from one to three hours; 5 per cent three to twelve hours; 11 per cent twelve to twenty-four hours, and 17 per cent a storage of more than twenty-four hours. =turbidity= is usually considered to exert an effect upon the dosage required but no definite evidence has been adduced in support of this hypothesis. turbidity is generally caused by the presence of very finely divided suspended matter, usually silt or clay, which is inert to hypochlorites. the condition that produces turbidity, however, produces a concomitant increase in the pollution and some of the organisms are embedded in mineral or organic material that prevents access of the chlorine to the organisms which consequently survive treatment. a larger concentration is required to meet these conditions but it is not necessitated by the turbidity _per se_. =effect of light.= light exerts a marked photo-chemical effect on the germicidal velocity of chlorine and hypochlorites. when chlorinated water is passed through closed conduits and basins the effect of light is of course nil but in open conduits and reservoirs this factor is appreciable and reduces the necessary contact period. the effect of light on laboratory experiments made with colourless glass bottles is so marked as to make it impossible to compare the results obtained on different days under different actinic conditions. the following figures illustrate the effect of sunlight: effect of sunlight -----------------+------------------------------------ | available chlorine 0.35 p.p.m. contact period. +-------------------+---------------- | exposed to bright | stored in dark | sunlight (april) | cupboard. -----------------+-------------------+---------------- nil | 215 | 215 30 minutes | 130 | 145 1 hour | 122 | 136 2-1/2 hours | 61 | 130 3-1/2 hours | 0 | 32 -----------------+-------------------+----------------=determination of dosage required.= the dosage required for the treatment of a water can only be accurately determined by treating samples with various amounts of chlorine and estimating the number of bacteria and _b. coli_ after an interval of time equal to that available in practice. the temperature of the water during the experiment should be the same as that of the water at the time of sampling. in order to limit the range covered by the experiments the approximate dosage can be ascertained from diagram v if the amount of oxygen absorbed by the water is known. this diagram is calculated on the amount of available chlorine, present as chlorine or hypochlorite, that will reduce the _b. coli_ content to the u. s. treasury standard (2 _b. coli_ per 100 c.cms.) in two hours. if the oxygen absorbed values are determined by the four-hour test at 27° c. they should be multiplied by two. another method which has been generally adopted for military work during the war, consists in the addition of definite volumes of a standard chlorine solution to several samples of the water and, after a definite interval, testing for the presence of free chlorine by the starch-iodide reaction. the details of the method of gascard and laroche, which is used by the french sanitary service, have been given by comte.[12] one hundred c.cms. of the water to be examined are placed in each of 5 vessels and 1, 2, 3, 4, and 5 drops of dilute eau de javelle (1:100) are added and the contents stirred. after twenty minutes, 1 c.cm. of potassium iodide-starch reagent (1 gram each of starch, potassium, iodide and crystallized sodium carbonate to 100 c.cms.) is added and the samples again stirred. the lowest dilution showing a definite blue colour is regarded as the dose required, and the number of drops is identical with that required of the undiluted eau de javelle for 10 litres of water when the same dropping instrument is used. the actual concentration represented by these dilutions depends necessarily upon the size of the drops and the strength of the undiluted eau de javelle, but one drop per 100 c.cms. usually represents approximately 1 p.p.m. [illustration: diagram v relation of dosage to oxygen absorbed] in horrocks's method, as used in the british army, a standard bleach solution is added and is almost immediately followed by the zinc iodide-starch reagent. the two methods were compared by massy,[13] who found that the french method gave an average result of only 0.06 m.gr. per litre (0.06 p.p.m.) higher than the english method. water in the gallipoli campaign required from 0.21 to 1.06 p.p.m. as determined by both methods. diénert, director of the paris service for investigating drinking water, adds 3 p.p.m. of available chlorine and allows the mixture to stand fifteen minutes after shaking; the residual chlorine is then titrated with thiosulphate. the amount absorbed is increased by 0.5 p.p.m. and in the opinion of diénert this dosage is correct for a contact period of three hours. for military camps where a standpipe usually provides a reasonable contact period, it has been found good practice to add sufficient chlorine to give a rich blue colour with the starch-iodide reagent and subsequently reduce the dosage gradually until the water, after standing one hour, gives but a faint reaction to the test reagent. this method should be checked up as soon as possible by bacteriological examinations. an example of this method is given in table xiv. table xiv.--control of dosage by starch-iodide reaction --------------------+-----------------------------------+------------- starch-iodide | bacteria on agar per c.cm. | reaction after one +-----------------+-----------------+ b. coli per hour. | 1 day at 37 c. | 2 days at 20 c. | 100 c.cms. --------------------+-----------------+-----------------+------------- 000[¤][¤] | 40 | 15 | 0 0000[¤] | 37 | 18 | 8 00000 | 68 | 268 | 34 00000 | 115 | 553 | 61 raw water | 114 | 685 | 89 --------------------+-----------------+-----------------+------------- the number of [¤] signs indicates the intensity of the reaction. bibliography [1] nissen. zeit. f. hyg., 1890, =8=, 62. [2] delépine, j. soc. chem. ind., 1911, =29=, 1350. [3] phelps. water supply paper no. 220, u. s. geo. survey. [4] wesbrook, whittaker, and mohler, j. amer. public health assoc., 1911, =1=, 123. [5] lederer and bachmann. eng. rec., 1912, =65=, 360. [6] harrington. j. amer. waterworks assoc., 1914, =1=, 438. [7] ellms. eng. rec., 1911, =63=, 472. [8] heise. philippine jour. sci., 1917, =12=, a, 17-34. [9] norton and hsu, jour. inf. dis., 1916, =18=, 180. [10] langer. zeit. f. hyg., 1916, =81=, 296. [11] longley. j. amer. public health assoc., 1915, =5=, 920. [12] comte. j. pharm. chim., 1916, =14=, 261. [13] massy. j. pharm. chim., 1917, =15=, 209. chapter iv bacteria surviving chlorination a disinfectant is usually described as a substance capable of destroying bacteria and other micro-organisms, and an antiseptic as one that restrains or retards their growth or reproduction. this distinction is entirely arbitrary as the ability of a substance to kill organisms or merely inhibit their growth depends upon the concentration employed. chlorine and hypochlorites, even in minute doses, exert a toxic effect that is sufficient to produce death in organisms but when still smaller concentrations are employed the toxic effect is transient and the reproductive faculty may be entirely regained. the enumeration of bacteria by means of solid media depends upon the ability of the organism to reproduce at such a rate as to produce a visible colony within the period of incubation and any substance that prevents the growth of a visible colony is classified as a disinfectant; if on further incubation the bacterial count approximates that of the untreated sample the added substance has acted mainly as an antiseptic. in practice no substance acts entirely as an antiseptic as the organisms present have varying degrees of resistance and the less viable ones are killed by doses that are only antiseptic to the more resistant ones. an example of an antiseptic effect followed by a mild disinfectant action, caused by small doses of bleach is shown in table xv. in this experiment the water designated as control was from the same source as the treated water. in order to make the bacterial count in this water approximately the same as in the treated water, the original count was reduced by diluting the sample with water from the same source, sterilised by boiling, and afterwards reaërated with sterile air. table xv.[a]--antiseptic effect of chlorine sample treated with 0.1 part per million of available chlorine. -------------+---------------------------------------+----------------- | | ratio of plated. | incubation period, days. | bacterial | | counts. --------+----+-------+-------+-------+-------+-------+-----+-----+----- time. |day.| 2 | 3 | 4 | 5 | 6 | 2:4 | 2:5 | 2:6 | | | | | | |days.|days.|days. --------+----+-------+-------+-------+-------+-------+-----+-----+----- 11 a.m.| 1 | 520| 940| 1,350| 2,360| 2,780|1:2.6|1:4.5|1:5.3 12 noon| 1 | 390| 770| 1,080| 2,040| 2,320| 2.8| 5.2| 5.8 2 p.m.| 1 | 187| 260| 690| 1,840| 2,080| 3.7| 9.9| 16.4 4 p.m.| 1 | 91| 130| 280| 760| 840| 3.1| 8.3| 9.2 10 a.m.| 2 | 42| 120| 670| 920| ...| 15.9| 22. | ... 10 a.m.| 3 | 320| 1,210| 3,500| ...| ...| 10.9| ...| ... 10 a.m.| 4 | 8,700| 14,200| 26,000| ...| ...| 2.9| ...| ... --------+----+-------+-------+-------+-------+-------+-----+-----+----- control. no chlorine added -------------+---------------------------------------+----------------- | | ratio of plated. | incubation period, days. | bacterial | | counts. --------+----+-------+-------+-------+-------+-------+-----+-----+----- time. |day.| 2 | 3 | 4 | 5 | 6 | 2:4 | 2:5 | 2:6 | | | | | | |days.|days.|days. --------+----+-------+-------+-------+-------+-------+-----+-----+----- 11 a.m.| 1 | 121| 184| 285| liquid| ...|1:2.4|1:...| ... 12 noon| 1 | 115| 171| 223| 380| 392| 1.9|1:3.2|1:3.2 2 p.m.| 1 | 109| 152| 221| 362| 375| 2.0| 3.3| 3.4 4 p.m.| 1 | 121| 175| 251| 410| 415| 2.1| 3.4| 3.4 10 a.m.| 2 | 6,200| 8,500| 8,800| 8,900| liquid| 1.4| 1.4| ... 10 a.m.| 3 |425,000|650,000|670,000| liquid| ...| 1.5| ...| ... --------+----+-------+-------+-------+-------+-------+-----+-----+----- original sample. untreated and undiluted --------+----+-------+-------+-------+-------+-------+-----+-----+----- 11 a.m.| 1 | 915| 1,410| 1,630| 2,150| 3,200|1:2.2|1:2.8|1:3.5 --------+----+-------+-------+-------+-------+-------+-----+-----+----- [a] results are bacteria per c.cm. table xvi shows the effect of a concentration of 1.0 p.p.m. of chlorine; the hypochlorite at this concentration acted almost entirely as a germicide or disinfectant. table xvi.[a]--effect of chlorine as a disinfectant available chlorine 1.0 p.p.m. ---------------+----------------------------- plated. | incubation period, days. ---------+-----+-----+-----+-----+-----+----- time. |day. | 2 | 3 | 4 | 5 | 6 ---------+-----+-----+-----+-----+-----+----- 11 a.m. | 1 | 2| 5| 7| 8| 10 12 noon | 1 | 1| 1| 2| 2| 4 2 p.m. | 1 | 0| 0| 0| 2| 2 4 p.m. | 1 | 1| 2| 2| 6| 6 10 a.m. | 2 | 0| 0| 0| 1| .. 10 a.m. | 3 | 0| 0| 0| ..| .. 10 a.m. | 4 | 5| 13| 16| ..| .. 10 a.m. | 5 | 79| 166| ..| ..| .. untreated| | | | | | water | .. | 915|1,410|1,680|2,150|3,200 ---------+-----+-----+-----+-----+-----+----- [a] results are bacteria per c.cm. table xv shows a recovery of the anabolic functions after treatment with 0.1 p.p.m. of chlorine but since this was obtained by plating on such a suitable medium as nutrient gelatine, it is probable that reproduction in water having a low organic content would be still further diminished. this is indicated by the results obtained. there is no evidence of any marked difference in the resistance of ordinary water bacteria to chlorine and these are the first to be affected by the added germicide. the common intestinal organisms are also very susceptible to destruction by chlorine and there is considerable evidence that _b. coli_ is slightly more susceptible than many of the vegetative forms usually found in water. the specific organisms causing the water-borne diseases, typhoid fever and cholera, are, on the average, not more resistant than _b. coli_. the spore-forming bacteria usually found in water are those of the subtilis group, derived largely from soil washings, and _b. enteritidis sporogenes_, from sewage and manure. the spores of these organisms are very resistant and survive all ordinary concentrations. wesbrook et al.[1] found that 3 p.p.m. of available chlorine had little effect on a spore-forming bacillus isolated from the mississippi water and the author has obtained similar results with _b. subtilis_. thomas,[2] during the chlorination of the bethlehem, pa., supply, found four organisms that survived a concentration of 2 p.p.m. of available chlorine: _bact. ærophilum_, _b. cuticularis_, and _b. subtilis_, all spore formers and _m. agilis_. in practice no attempt is made, except in special cases, to destroy the spore-bearing organisms as they have no sanitary significance and the concentration of chlorine required for their destruction would cause complaints as to tastes and odours if the excess of chlorine were not removed. such doses are unnecessary and result in waste of material. it is found that, when the dose is sufficient to eliminate the _b. coli_ group from 25-50 c.cms. of water, the majority of the residual bacteria are of the spore-bearing type. smeeton[3] has investigated the bacteria surviving in the croton supply of new york city after treatment with 0.5 p.p.m. of available chlorine as bleach. table xvii gives the results obtained. the organisms of the _b. subtilis_ group outnumbered all the others, 66 (62.8 per cent) belonging to this group alone. this group contained _b. subtilis_--cohn (36 strains), _b. tumescens_--chester (15 strains) _b. ruminatus_--chester (13 strains), and _b. simplex_--chester 1904, (2 strains). three of the four coccus forms were classified as _m. luteus_. no intestinal forms were found. clark and de gage[4] in 1910 directed attention to the fact that the bacterial counts, made at 37° c. on chlorinated samples, were often much greater than the counts obtained at room temperature. "this phenomenon of reversed ratios between counts at the two temperatures," they stated, "has been occasionally observed with natural water, but a study of the record of many thousands of samples shows that the percentage of such samples is very small, not over 3-5 per cent.... on the other hand 20-25 per cent. of samples treated with calcium hypochlorite show higher counts at body temperature than at room temperature." clark and de gage were unable to state the true significance of this phenomenon but were of the opinion that it was not due to larger percentages of spore-forming bacteria in the treated samples. other observers, on the contrary, have invariably found the spore-formers to be more resistant to chlorine and thermophylic in type. table xvii.--organisms surviving treatment new york (smeeton) ---------------+---------------+-------------+-------------+------------ | morphology | spore | gelatine | reaction in | | formation |liquefaction | litmus milk +--------+------+------+------+------+------+------+----- |bacilli.|cocci.| pos. | neg. | pos. | neg. | pos. | neg. ---------------+--------+------+------+------+------+------+------+----- no. of strains | 100 | 5 | 89 | 16 | 68 | 37 | 98 | 7 per cent. | 95.2 | 4.7 | 84.7 | 15.2 | 64.7 | 35.2 | 93.3 | 6.6 ===============+========+======+======+======+======+======+======+====== | indol | acid | reduction | inhibition | production | production | of | by gentian | | in glucose | nitrates | violet +--------+------+------+------+------+------+------+----- | pos. | neg. | pos. | neg. | pos. | neg. | pos. | neg. ---------------+--------+------+------+------+------+------+------+----- no. of strains | 75 | 30 | 61 | 44 | 40 | 65 | 98 | 7 per cent. | 71.4 | 28.5 | 58 | 41.9 | 38 | 61.9 | 93.3 | 6.6 ---------------+--------+------+------+------+------+------+------+-----the removal of intestinal forms is, of course, merely a relative one and when large quantities of treated water are tested their presence can be detected. the author, in 1915, made a number of experiments to ascertain whether the _b. coli_ found after chlorination were more resistant to chlorine than the original culture. the strains surviving treatment with comparatively large doses were fished into lactose broth and subjected to a second treatment, the process being repeated several times. the velocity of the germicidal reaction with the strains varied somewhat, but not always in the same direction, and the variations were not greater than were found in control experiments on the original culture. no evidence was obtained that the surviving strains were in any way more resistant to chlorine than the original strain; in considering the results it should be borne in mind that the surviving strains were cultivated twice on media free from chlorine before again being subjected to chlorination. a number of the strains that survived several treatments were cultivated in lactose broth and the acidity determined quantitatively. all the cultures produced less acid than the original culture, and the average was materially less than the original. these results point to a diminution of the bio-chemical activity by action of the chlorine. a point of perhaps more scientific interest than practical utility is the relative proportion of the various types of _b. coli_ found before and after treatment with chlorine. the author, in 1914, commenced the differentiation of the types by means of dulcite and saccharose and obtained the results shown in table xviii. these figures are calculated from several hundreds of strains. although there is a slight difference in the relative proportions of the types found at ottawa and baltimore, both sets of results show definitely that there is no difference in the resistance of the various types to chlorination. =aftergrowths.= in tables xiii (p. 44) and xv (p. 51), it will be noticed that, after the preliminary germicidal action has subsided, a second phase occurs in which there is a rapid growth of organisms. this is usually known as aftergrowth. when the contact period between chlorination and consumption is short, the reaction does not proceed beyond the first phase, but when the treated water is stored in service reservoirs the second phase may ensue. at one purification plant, where the service reservoirs are of large capacity, the aftergrowths amounted to 20,000 bacteria per c.cm. although the water left the purification plant with a bacterial count usually lower than 50 per c.cm. table xviii.--types of _b. coli_ surviving chlorination ------------------+----------------------------------------------- | percentage of organisms. +-----------+-----------+-----------+----------- | b. coli | b. coli | b. lactis | b. acidi | communis | communior | aerogenes | lactici +-----+-----+-----+-----+-----+-----+-----+----- | |chlo-| |chlo-| |chlo-| |chlo |raw. | ri|raw. | ri|raw. | ri|raw. | ri | |nated| |nated| |nated| |nated ------------------+-----+-----+-----+-----+-----+-----+-----+----- ottawa, 1914 | 5 | 4 | 40 | 48 | 44 | 36 | 11 | 12 ottawa, 1915 | 8 | 8 | 50 | 46 | 34 | 31 | 8 | 15 baltimore, 1913[a]| 11 | 14 | 33 | 25 | 35 | 31 | 21 | 30 ------------------+-----+-----+-----+-----+-----+-----+-----+----- [a] thomas and sandman.[5] regarding the nature of this aftergrowth, there has been a considerable difference of opinion: some regard it as the result of the multiplication of a resistant minority of practically all the species of organisms present in the untreated water; others, that it is partially due to the organisms being merely "slugged" or "doped," i.e. are in a state of suspended animation, and afterwards resume their anabolic functions; whilst others believe that with the correct dosage of chlorine, only spore-forming organisms escape destruction and that the aftergrowth is the result of these cells again becoming vegetative. the aftergrowths obtained under the usual working conditions vary according to the dosage of chlorine employed, and none of the above hypotheses alone provides an adequate explanation. when the dosage is small, a small number of active organisms, in addition to the spore bearers, will escape destruction, and others will suffer a reduction of reproductive capacity. the flora of the aftergrowth in this case will only differ from the original flora by the elimination of a majority of the organisms that are most susceptible to the action of chlorine and the weaker members of other species of greater average resistance. as the dose is increased these factors become relatively less important until a stage is reached when only the most resistant cells, the spores, remain. the resultant aftergrowth must necessarily be almost entirely composed of spore-bearing organisms. a small number of the most resistant members of non-sporulating organisms may also be present but they will, in the majority of instances, form a very small minority. this is the condition that usually obtains in practice and it is necessary to consider whether the aftergrowth may have any sanitary significance. concerning the secondary development of _b. coli_, the usual index of pollution, there is but little information. h. e. jordon[6] reported that, of 201 samples, 21 gave a positive _b. coli_ reaction immediately after treatment, 39 after standing for twenty-four hours, and 42 after forty-eight hours. these increases were confined to the warm months, the cold months actually showing a decrease. the following figures, taken from the author's routine tests for 1913 and 1914, show a similar tendency, but an analysis of the results by months did not show that this was confined to the warm season. the sequence of the results from left to right, in the following table, is in the same order as the contact period. approximately 290 samples were taken at each sampling point. at station no. 2 the germicidal action was still proceeding but at no. 5, representing an outlying section of the city, the increase in the _b. coli_ content is very apparent. during 1915 and 1916 the author endeavoured to duplicate these results under laboratory conditions and entirely failed. these experiments, which were made with the same materials as were in use at the city chlorination plant, but in glass containers, were usually only carried to a forty-eight hours contact, as this was the extreme limit for the city mains; one, however, was prolonged to five days. many experiments were made under varying conditions, with similar results. typical examples are given in tables vi, viii and ix on pages 33 and 37. table xix.--aftergrowths of b. coli percentage of samples showing b. coli in 10 c.cms. -----+--------------------------------- | sampling point no. +------+------+------+------+----- | 1 | 2 | 3 | 4 | 5 +------+------+------+------+----- 1913 | 15.2 | 14.4 | 16.3 | 16.8 | 26.8 1914 | 7.0 | 5.7 | 6.0 | .... | 11.6 -----+------+------+------+------+-----in every case there was persistent diminution in the number of _b. coli_ with increase of contact period. determination of the bacterial count on nutrient agar showed that, in several experiments, the aftergrowth had commenced, and in some instances there was evidence that the second cycle was partially complete i.e. the number had reached a maximum and then commenced to decline. the time required for the completion of the two cycles, comprising the first reduction caused by the chlorine, the increase or aftergrowth, and the final reduction due to lack of suitable food material, is dependent upon several factors of which the dosage and temperature are the most important. with a small dosage the germicidal period is short and the second phase is quickly reached; with large doses, the second phase is not reached in forty-eight hours; the higher the temperature the quicker is the action and the development of the aftergrowth. these statements refer only to the bacteria capable of development on nutrient agar. the _b. coli_ group behaved differently and persistently diminished in every case. if _b. typhosus_ acts in a similar manner to _b. coli_, the laboratory experiments show that aftergrowths are of no sanitary significance and can safely be ignored, but as the results obtained in practice are contradictory to the laboratory ones, the matter must be regarded as _sub judice_ until more definite evidence is available. it is common knowledge that samples of water from "dead ends" of distribution mains show high counts and much larger quantities of _b. coli_ than the water delivered to the mains. this is another phase of aftergrowth problem that often causes complaints and can only be eliminated by "blowing off" the mains frequently or by providing circulation by connecting up the "dead ends." one extreme case of this description might be cited. a small service was taken off the main at the extreme edge of the city to supply a musketry school two miles away and was only in use for a few months in the summer season. this service pipe delivered water containing _b. coli_ in a considerable percentage of the 10 c.cm. samples and in a few instances in 1 c.cm., although the water delivered to the city mains never exceeded 2 _b. coli_ per 100 c.cms. and averaged about one-tenth that quantity. no epidemiological records of the effect of this water are available because it was put through a forbes steriliser before consumption. in some instances the rate of development of the organisms after chlorination is greater than in the same water stored under similar conditions. this is especially noticeable in the presence of organic matter and has been ascribed to the action of the chlorine on the organic matter with the production of other compounds that are available as food material for the organisms. houston, during the treatment of prefiltered water lincoln in 1905, found that although the removal of _b. coli_ and other organisms growing at 37° c. was satisfactory, there was almost invariably an increase in the bacteria growing on gelatine at 20° c. this was ascribed to the action mentioned above and the chemical results supported this view, more organic matter being found in the filter effluents than in the prefiltered water. rideal's experiments with sewage at guildford indicate that a similar action may occur in contact beds. the addition of bleach to the prefiltered water at yonkers also resulted in an increased count and in these instances the aftergrowths are due to a disturbance of the equilibrium by the action of the chlorine on the zooglea and other organic matter invariably found in ripe filters. similar results can be produced by the addition of chlorinated water to small experimental sand filters. this is shown by the results in tables xx and xxi. table xx.--aftergrowths in sand --------------+---------------+---------------+--------------- | bacteria per | | available | gram of |typical b. coli| free chlorine chlorine in | sand after |after 24 hours.| after 24 hrs. water p.p.m. +-------+-------+---+---+---+---+-------+------- | | |100| 10| 1 |0.1|without| after | 3 hrs.|24 hrs.|gr.|gr.|gr.|gr.| acidification. --------------+-------+-------+---+---+---+---+-------+------- nil | 12,000| 21,000| + | + | + | | | 3.0 | 80|114,000| | | | | | 5.0 | 50|150,000| | | | | | 7.0 | 25|214,000| | | | | | 10.0 | 26|500,000| | | | | | --------------+-------+-------+---+---+---+---+-------+-------table xxi.--aftergrowths in sand --------------+-------------------------------- | bacteria per gram of sand after available in +----------+----------+---------- water p.p.m. | 3 hours. |24 hours. |48 hours. --------------+----------+----------+---------- nil | 70,000 | ..... | ..... 0.1 | 7,200 | 20,400 | 12,800 0.3 | 5,240 | 6,400 | 11,200 0.5 | 5,120 | 4,700 | 10,800 1.0 | 1,100 | 8,800 | 20,400 --------------+----------+----------+----------it is observable that the effect of small doses was comparatively small and transient; large doses of bleach reduced the bacteria very materially but the reduction was not maintained and the subsequent increase was abnormally rapid. bibliography [1] wesbrook, whittaker and mohler. j. amer. pub. health assoc., 1911, 1, 123. [2] thomas. jour. ind. and eng. chem., 1914, 6, 548. [3] smeeton. jour. of bact., 1917, 2, 358. [4] clark and de gage. rpt. mass. b. of h., 1910, p. 319. [5] thomas and sandman. j. ind. and eng. chem., 1914, 6, 638. [6] jordan, h. e. eng. record, 1915, may 17. chapter v complaints the complaints that have been made against chlorinated water since the practice was commenced have been very diversified in character and can be numbered by the legion and although some have been justifiable, the great majority has been unsubstantiated and must be ascribed to auto-suggestion. almost every one who has had charge of chlorination plants has noted the latter phenomenon, for in some instances complaints have been made following the publication of the information that chlorination was to be commenced but antecedent to its actual operation, and in others when for some reason or another, the chlorination plant has been temporarily stopped. similar observations have been made in laboratory experiments when independent observers have been requested to detect the chlorinated waters from an equal number of treated and untreated waters. such observers are wrong in the majority of the waters which they designate as treated ones if the dosage is not in excess of that required for satisfactory purification. one amusing example of auto-suggestion was experienced by the author some years ago. during a ceremonial visit to the waterworks, the mayor and several civic representatives happened to visit a hypochlorite plant that was built on a pier over the river and which had no ostensible connection with the city mains. one of the party expressed a desire for a drink of good river water without any hypochlorite in it and was served with water from the plant supply by an assistant engineer of the waterworks department. the water was consumed by all with great relish and as it was being finished, the writer entered the plant and was invited to join them in the enjoyment of this "dopeless" water; on asking where it had been obtained he was astonished to hear that it was from a tap which was supplied with the ordinary chlorinated water of the city. on many occasions, complaints are justifiable and should be carefully investigated instead of, as is often the case, being attributed to auto-suggestion. the time and energy that are often devoted to endeavouring to persuade water consumers that their complaints are without foundation, can better be utilised in so improving the chlorination process as to eliminate tastes and odours. all complaints should be carefully investigated and a record kept for future reference, for the cause, although not manifest at the time, may be discovered later. the records then provide valuable corroborative evidence. the nature of the complaints against chlorinated water is very diversified and includes imparting foreign tastes and odours, causing colic, killing fish and birds, the extraction of abnormal amounts of tannin from tea, the destruction of plants and flowers, the corrosion of water pipes, and that horses and other animals refuse to drink it. _tastes and odours._ when an excess of hypochlorite or liquid chlorine is added to a water it imparts a sharp pungent odour and acid taste, characteristic of chlorine, that render it offensive to the nose and palate. in some instances the presence of chlorine compounds is not obtrusive when the temperature of the water is low but becomes so when the temperature is raised. it is especially observable when the faucets of hot water services are first opened and the chlorine is carried off as a vapour by the other gases liberated by the reduction in pressure. for this reason the complaints regarding hot water are relatively more numerous and sometimes constitute the whole of the complaints. in cold water containing appreciable quantities of mineral salts the hypochlorites and hypochlorous acid might not be entirely dissociated; they may become more hydrolysed with an increase in temperature and finally broken down under the influence of the carbonic acid liberated from the bicarbonates by heat. chlorine also forms chlorinated organic compounds by action on the organic matter present in water and some of the objectionable tastes and odours of chlorinated waters have been attributed to this agency. some observers have stated that chloramines were amongst the chloro-organo compounds produced but the author's experience with the ottawa supply has demonstrated that simple chloramine (nh_{2}cl) can be successfully employed for water treatment without causing complaints. it was suggested on page 28 that some of the higher chloro-amines might be the cause of some complaints but at present there is no definite information regarding the formation of these compounds in water and all such hypotheses are little more than conjectures. letton[1] has reported that at trenton, in 1911, when the water of the delaware river was first treated, the dosage was as high as 1.2 p.p.m. of available chlorine and although chemical tests showed the absence of free chlorine, the water had an extremely disagreeable taste which was especially noticeable in the hot water. the conclusion was reached that "the taste and odour were not those of chlorine, but were due to some complex chemical change brought about by the action of the chlorine on the organic matter present in the water." the waters that require the most accurate adjustment of chlorine dosage, if complaints are to be avoided, are those containing very small amounts of organic matter. the margin between the dosage required for the attainment of a satisfactory degree of bacteriological purity and that which may cause complaints is usually very small, often less than 25 per cent, with the waters of the great lakes and many filter effluents. on the other hand, coloured waters containing large amounts of organic matter can be treated with an excess of chlorine without causing tastes and odours. the author found that the addition of 1.5 p.p.m. of available chlorine to the ottawa river water did not cause complaints although only 0.8 to 0.9 p.p.m. were usually required for satisfactory purification. harrington of montreal has had a similar experience with this water. the presence of traces of foreign substances in water sometimes produces chlorinated derivatives having repugnant tastes and odours. creosote and tar oils have caused an odour somewhat resembling that of iodoform and industrial wastes have also produced complaints. the substitution of chlorine gas (liquid chlorine) for bleach solutions has apparently eliminated tastes and odours in some cases but this may be due to a more perfect control over the dosage rather than to any property of the bleach _per se_. in some instances the sludge from bleach plants has caused complaints by producing an excessive concentration of chlorine during the period of its discharge. this occurred in ottawa on several occasions before it was discovered and corrected. when the sludge in the storage tanks reached the discharge valve it was customary to wash out the tank and discharge the sludge into the river. the operators opened the wash out valves to the full extent and the sludge and liquor were discharged into the river about 70 feet away from the inlet to the sedimentation basin and on the downstream side of it. a portion of the hypochlorite was almost invariably carried into the basin and increased the dosage. this condition was remedied by carrying the sludge drain farther down stream and insisting upon the sludge being discharged at a slower rate. kienle[2] has reported similar occurrences at chicago. the hypochlorite was applied at the intake cribs situated a considerable distance off shore. the direction of the wind often necessitated holding the sludge for a considerable length of time but occasionally it was found impossible to await favourable conditions with the result that the wind and wave action carried a portion of the sludge back into the crib and down into the shaft and tunnel. the temperature of the water at the time of treatment is another factor bearing on the production of tastes and odours. when the temperature is low, water absorbs relatively less chlorine (_vide_ diagram no. ii, page 38) in the same period of time with the consequence that, if the dosage is kept constant, more chlorine is present in the free condition. at milwaukee (kienle)[2] with a dosage of 0.24 p.p.m. of available chlorine (as bleach) no complaints were received during the spring, summer, and autumn seasons but when the temperature reached 40° f., they were compelled to reduce the chlorine to 0.12 p.p.m. in order to prevent objectionable tastes and odours in the tap waters. abnormal conditions such as freshets, and storms, sometimes cause complaints regarding tastes and odours. adams[3] found that the complaints in toronto usually accompanied a change in the direction of the wind, a sustained east wind being the one most productive of trouble. the exact cause for this could not be ascertained but it was usually found that there was an accompanying increase in the number of microscopical organisms (plankton) present in the raw water. freshets usually increase the bacterial contamination and necessitate an increased dosage which may cause complaints. complaints as to tastes and odours can be best avoided by ensuring regularity of dosage, perfect admixture, and storage of the treated water for a reasonable period. these factors are discussed in detail elsewhere. _colic._ although claims have been made that the consumption of chlorinated water has produced "colic" no corroborative evidence has been adduced and the symptoms have probably been due to some other cause. dilute solutions of chlorine have been used as intestinal antiseptics in the treatment of typhoid fever without producing irritation of the mucous lining and the usual dose for this treatment is one grain of chlorine. before taking a _medicinal_ dose of chlorine 140 gallons of water containing 0.1 p.p.m. would have to be consumed, a quantity greater than is ordinarily drunk in a year. chlorine and hypochlorites are destructive and irritant to skin and it is possible that hot chlorinated water has, in some instances, a similar effect. it is inconceivable that the addition of minute traces of bleach or chlorine to water should cause it to extract abnormal amounts of tannin from tea but it is possible that free chlorine, when present, acts upon the tea extractives and produces compounds having obnoxious tastes and odours. tannin to the ordinary tea drinker represents the disagreeable portion of the tea and an obnoxious taste in tea brewed with chlorinated water would consequently be ascribed to the extraction of abnormal quantities of tannin. almost all waterworks departments using chlorination have received complaints to the effect that the water had killed fish and small birds. there is usually no evidence that the loss was due to chlorinated water but it is generally impossible to convince the owners that the process of water treatment was not the cause. many continuous physiological tests have been made of the effect of chlorinated water on small fish and have shown that the concentration used in water treatment is without effect. the author kept a tank of minnows in one of the pumping stations for months without loss although the tank was continuously supplied with water that had been treated but a few seconds previously. the bleach solution was discharged into the suction of the pumps and the water for the fish test was taken from the discharge header. it has been found on many occasions that fish are extremely susceptible to chlorine and hypochlorites. this knowledge has been sometimes used for such nefarious purposes as fish poaching, a few pounds of bleach in a small stream being a simple and most effective method of killing all the fish which are then carried down stream into a convenient net. chlorinated sewage effluents have also been known to destroy the fish life of the stream into which they were discharged. the opinion of fish culturists as to the action of chlorinated waters upon fish eggs in hatcheries is almost unanimously to the effect that it is a destructive one. fish eggs are extremely sensitive to chlorine and hypochlorous acid and very few will survive in a water containing 0.1 p.p.m. of free chlorine. the department of fisheries of the dominion of canada has informed the author that free chlorine in the water had a marked adverse effect on the hatching of the eggs of atlantic salmon, great lake trout, pickerel, and whitefish, but no effect was noticed when free chlorine was absent. the department has, however, decided to remove all the hatcheries to localities where water that does not require chlorination can be obtained. the effect of chlorinated water upon seeds, plants, and flowers has been investigated by the dominion department of agriculture and dr. gussow (dominion botanist) and dr. shutt (agricultural chemist) who were in charge of the work, have reported that water treated with hypochlorite caused no apparent injury to carnations and hybrid roses. six varieties of wheat seed, after soaking in freshly prepared hypochlorite solutions (0.05 to 10 parts per million of available chlorine) were all sown on the same day. germination was found to be uniform throughout and no effect of the chlorine was observed either as regards the rate of germination or the development of the young plants. experiments on barley and oats produced similar results. radishes, turnips, cucumbers, and beans also showed no retardation in development after treatment with chlorinated water. these experiments were conducted with solutions of bleach in distilled water, but identical results were obtained in a later series when the treated city supply (ottawa) was used. the results proved conclusively that statements alleging damage to plants, flowers, and seeds by the hypochlorite treatment of water are unfounded and do not merit the slightest consideration. _corrosion of pipes._ chlorinated water, it has been alleged on many occasions, causes rapid corrosion of galvanised iron water services and especially of the water tubes of boilers, water heaters, etc. when bleach is used for water treatment, a slight increase in the hardness is produced but as this is mostly due to calcium chloride, there is no corresponding increase in the salts that form a protective coating. the presence of traces of calcium chloride and chloro-organic compounds might tend to increase the corrosive properties of a water but this increase is probably so small as to be negligible. if pipe corrosion is considered by the carbonic acid hypothesis, the use of bleach should tend to reduce it because bleach contains an excess of base that combines with a portion of the free carbonic acid. the results of routine tests for free carbonic acid made on the raw and treated waters at ottawa are as follows: -------+----------------------+------------------------ | carbonic acid. | | parts per million | year. +----------+-----------+ nature of treatment. |raw water.|chlorinated| | | water. | -------+----------+-----------+------------------------ 1915 | 1.44 | 1.41 | bleach 1916 | 0.92 | 0.85 | bleach 1917 | 0.84 | 0.81 | bleach first four months | | | chloramine during last | | | eight months -------+----------+-----------+------------------------these figures shown that the hypochlorite treatment produced a small but definite decrease in the carbonic acid content and should, _cæteris paribus_, tend to reduce and not increase corrosion. if the corrosion of pipes is considered according to the electrolytic theory, a slight increase, due to an increased electrical conductivity, might be anticipated. the effect of the addition of hypochlorite upon the electrical conductivity of distilled water and the ottawa river water is shown in diagram vi. [illustration: diagram vi effect of calcium hypochlorite on electrical conductivity] with the concentrations of hypochlorite ordinarily used in water treatment it is inconceivable that the slight increase in the electrical conductivity has any practical significance at low temperatures. the conductivity increases rapidly, however, with increase of temperature and any increment due to chlorination might produce a slight appreciable effect at temperatures approaching the boiling-point of water. liquid chlorine does not increase the conductivity to the same extent as an equivalent quantity of hypochlorite but it increases the carbonic acid content in proportion to the dosage used. the author investigated the action of hypochlorite on galvanised pipes in 1914 and was unable to detect any definite corrosion with normal concentrations of chlorine. the experiments were made with 2-inch pipes and an examination of the first consignment received showed that, although the galvanising on the outside was perfect, the inner coat was very inferior: in some parts there was an excess of zinc that broke away on scraping whilst in others the iron pipe was bare. a committee of the pittsburg board of trade, appointed to investigate complaints as to pipe corrosion, reported in 1917 that they were largely due to inferior qualities of pipes and not to the method of water purification employed (slow sand filtration and chlorination). the effect of chlorination on the _plumbo-solvency_ of water was investigated in 1904 by houston who found that chlorine, as chloros, in amounts between one and ten parts per million, did not appreciably increase the plumbo-solvent action of either unfiltered or filtered water. similar results were obtained by the author with the toronto supply: raw lake water, filtered water, and water treated with 0.25 and 0.50 p.p.m. of chlorine, all dissolved the same quantity of lead in twenty-four hours. the amount in each case was too small to be of any significance. bibliography [1] letton. j. amer. waterworks assoc., 1915, 2, 688. [2] kienle. j. amer. waterworks assoc., 1915, 2, 690. [3] adams. j. amer. pub. health assoc., 1916, 6, 867. chapter vi bleach treatment the treatment of water with bleach alone has been largely supplanted by the liquid chlorine process but the following details will be of use on meeting conditions for which liquid chlorine cannot be used and also for the preparation of the hypochlorite solution required in the chloramine process. the essential features of a bleach installation are the solution or mixing tanks, storage tanks, piping system, discharge orifice or weir, and sludge drain. bleach is usually sent out by the manufacturers in sheet steel drums, 39 inches high and 29-1/2 inches in diameter, which contain about 14 cu. ft. of bleach and weigh approximately 750 pounds gross and 690 pounds net. it can be most economically purchased in car lots and if the consumption warrants this procedure storage should be provided for about 70 drums or rather more than one car load. according to hooker[1] bleach loses 1 per cent of available chlorine per month in hot seasons and 0.3 per cent in cold ones so that it is advisable to carry as little stock as possible during hot weather. hot weather also causes a further loss by accelerating the action of the bleach on the drum which rapidly disintegrates and cannot be handled. bleach can often be purchased more cheaply in hot weather but such a policy is a short sighted one unless it is required for immediate use. the general design of a hypochlorite plant is largely determined by the capacity but in all cases an effort should be made to avoid complicated details which may appear advantageous in the drafting office but do not stand up in actual practice. many metals rapidly develop a protective coating on immersion in bleach solution but if this is removed by friction, rapid erosion ensues; bearing metallic surfaces should be reduced to a minimum. _mixing tanks._ all tanks, whether mixing or storage, should be constructed of concrete and painted with two coats of asphalt. experience has shown that wooden tanks are not suitable. the author has used pine, oak, and cypress tanks but all were rapidly leached by the hypochlorite and ultimately had to be lined with concrete. there is a considerable variation in the concentration of bleach solution made in mixing tanks at various works. some operators use about one gallon of water per pound of bleach and mix the two to a cream by wooden paddles, revolving on a central axis, for 1-2 hours; the paddles are then stopped and the cream run out into the storage tanks and diluted to the required strength by passing water through the mixing tank. there are two objections to this method: (1) the addition of small quantities of water to bleach tends to gelatinisation which may protect lumps from the further action of water and (2) a stratification of the solution occurs in the storage tank unless agitation is used. gelatinisation causes loss of available chlorine and stratification causes irregular dosage unless corrected by agitation, which necessitates power. other operators mix the bleach and water to the final concentration in the mixing tank and discharge the contents into the storage tank, the intermittent process being repeated until the storage tank is full. gelatinisation is avoided by using a low original concentration and as all batches are of equal density no stratification is produced. at ottawa the bleach is crushed and, after weighing, dumped into a circular concrete tank provided with a hinged wooden lid. the stirring arrangement consists of a bronze shaft on which an aluminium impeller is fixed which revolves in an iron tube set slightly above the bottom of the tank (see fig. 1). after the requisite amount of water has been added the motor connected to the bronze shaft is started and the mixture pumped for 15-20 minutes; without waiting for the sludge to settle the contents are discharged into the storage tank and the operation repeated until the tank is full. the piping between the mixing and storage tanks is of galvanised iron of generous dimension so as to compensate for incrustation. the pipes are straight and are provided with crosses at every change of direction to enable excessive incrustation to be removed. the valves should be made of hard rubber or special bronze; if brass valves are used they will probably require renewing every twelve months. [illustration: fig. 1.--mixing tank for bleach.] the concentration of solution necessarily depends upon local conditions but it is usually advisable to keep it below 2.5 per cent of bleach, which is equivalent to 0.85 per cent of available chlorine. _storage tanks._ these should be built of reinforced concrete and painted inside with asphalt, which should be periodically renewed to prevent the solution seeping through to the reinforcement. at least two tanks should be provided so that one may be filled and allowed to settle before being put in operation. the hypochlorite discharge pipe is usually 6-9 inches from the bottom to permit the collection of sludge, which is run off when it reaches the elevation of the hypochlorite discharge. the sludge drain, which opens into the bottom of the tank, is usually a 4or 6-inch cast-iron pipe, with suitable gate valve, which discharges into a common drain made of clay pipe. the storage tanks should be provided with either glass gauges or float indicators to enable the orifice discharge to be checked up at periodical intervals. _regulation of dosage._ the discharge of the hypochlorite solution is usually regulated either by maintaining a constant head on an orifice of variable dimension or by varying the head on an orifice of fixed dimension. the weir principle may also be used but it is not so well adapted for hypochlorite as for other chemicals. in the constant head method, the head is maintained by a bronze valve connected to a float made of glass or tinned copper. in many cases the orifice is a rectangular slot in a brass plate and is adjusted by means of a brass slide operated by a micrometer screw. brass plates are not very suitable as they become corroded and so reduce the size of the orifice; if the incrustation is removed the orifice will discharge more than the calibration indicates. needle valves are unsuitable for similar reasons. an example of an orifice feed box of the constant head type is shown in fig. 2. a vertically arranged hard-rubber pipe passes though a hard rubber stuffing box in the bottom of the tank and has one or more orifices near its upper end. the area of the submerged portions of the orifices is controlled by the hand wheel which is connected with the threaded stem of the pipe. the stem has sixteen threads per inch, and one revolution of the wheel will submerge the orifices one-sixteenth of an inch. the extent to which the orifices are submerged is indicated on the dial fixed to the side of the tank. [illustration: fig. 2.--dosage tank.] fig. 3 shows the regulating mechanism of another apparatus of the constant head type. the orifice consists of a circular slot in a hard rubber disc and is regulated by means of a hand wheel which operates a hard rubber slide. [illustration: fig. 3.--orifice controlling device.] the general arrangement of one of the variable head types is shown in fig. 4. a constant head is maintained on the valve _v_ by a float and cock operating in a leador porcelain-lined tank. the circular tapered orifice _o_, cut in glass, is situated in the flanged end of the iron casting _c_ and the head, indicated on the gauge glass, is regulated by valve _v_. this arrangement is simple and reasonably accurate. the orifice may show slight incrustation after being in service for some time but it can be easily cleaned by means of a test-tube brush or a small swab moistened with acid; a wire or rod tends to break the edge of the conical orifice and should not be used. the volume of solution discharged by orifices of various dimensions is shown in diagram xv, page 149. diagram xvi, page 149, facilitates the calculation of the number of pounds of bleach required for any dosage. [illustration: fig. 4.--variable head dosage box.] the solution discharged from the orifice box is carried to the point of application either in galvanised iron pipes of generous dimension or in rubber hose. pumps may be used for raising the solution to a higher elevation but unless special material is used in their construction they corrode rapidly and cannot be kept in service. whenever possible, a water injector should be used as it does not corrode and assists in maintaining the delivery pipes free from sludge. all delivery pipes should be duplicated and blown out regularly by water under pressure; they should also be protected from frost. the adjustment of the hypochlorite dosage can be automatically regulated in plants where the flow of the water to be treated is measured by a venturi meter or other suitable appliance. various devices have been suggested and used but, in general, they are not so successful as automatic regulators for liquid chlorine on account of the presence of sludge particles which tend to diminish the area of the orifice. for small plants, barrels have often been used as solution and storage vessels with, in some instances, fairly successful results. the bleach process, however, cannot be recommended for small installations because the chemical control necessary for successful operation is usually not available. one drum of bleach may suffice for several months operation and as the powder gradually loses strength, the dosage constantly diminishes and may jeopardise the safety of the supply. liquid chlorine machines are much more suitable than hypochlorite installations for supplies having no chemical control. bleach is being very extensively used for the sterilisation of the water used by the allied troops in france. the water supplies on the british front are all more or less subject to pollution and it is consequently necessary, to ensure adequate protection, to chlorinate all supplies with bleach. other forms of chlorine have been tried but have not proved successful near the firing lines. the details of the technique employed cannot be given but it may be stated that the concentration of chlorine employed is always more than sufficient and that residual tastes and odours are regarded as secondary considerations. treated water is always tested by the starch-iodide method and a bacteriological examination is frequently made by mobile laboratories. =control of hypochlorite plants.= if efficient operation and regular dosage is to be obtained, it is necessary that hypochlorite plants should be controlled by a trained chemist. good results are occasionally obtained without such control but in every plant circumstances arise at some period or another which only a chemist is qualified to deal with. the points that require consideration are (1) the composition of the bleach; (2) concentration of available chlorine in the prepared solutions; and (3) chemical tests for free chlorine in the treated water. (1) _composition of bleach._ each drum of bleach should be sampled and analysed before use. the sample is obtained by cutting out the head of the drum and removing a vertical section by means of a special sampling tube or a piece of half-inch iron pipe which is forced to the bottom of the drum with a boring motion and then removed; the core is then forced out by means of a rod, mixed, and quartered down to the required size. for analysis weigh out 5 grms. on a balance sensitive to 0.01 grm. and grind in a mortar with 50-70 c.cms. of water; wash into a 250 c.cm. flask and make the volume up to 250 c.cms.; shake. after allowing the sludge to settle remove 10 c.cms. by means of a pipette and titrate by one of the following methods: _bunsen's method._ add 10 c.cms. of a 5 per cent solution of potassium iodide and 0.5 c.cm. glacial acetic acid and titrate with sodium thiosulphate (24.8 grms. of the c.p. crystalline salt and 1 c.cm. of chloroform per litre) using a starch solution as indicator. each cubic centimetre of thiosulphate used = 1.755 per cent of available chlorine (1 c.cm. n/10 sodium thiosulphate = 0.00355 grm. available chlorine). _penot's method._ dilute the hypochlorite solution with 15 c.cms. of water and titrate with a solution of n/10 sodium arsenite using starch-iodide paper as an external indicator. each c.cm. of solution used = 1.755 per cent of available chlorine (1 c.cm. = 0.00355 grm. available chlorine). the use of an external indicator makes this process a slow one and to overcome this objection mohr proposed the addition of an excess of sodium arsenite solution and then titrating with n/10 iodine solution after adding a few drops of starch solution. griffen and hedallen[2] compared these three methods and found that penot's method and mohr's modification of that method gave results which were 0.6 per cent lower than those obtained by bunsen's method. for a separate estimation of the chlorine present as chloride, chlorate, and hypochlorite the method given in sutton's volumetric analysis, 10th edition, page 178, should be followed. _storage liquor._ this is tested by any of the above methods. it has been proposed to determine the strength of the bleach solution by the use of a hydrometer but the results are not sufficiently accurate and the method cannot be recommended. if bleach is properly broken up and thoroughly agitated in the mixing tank at least 95 per cent of the available chlorine should be extracted. the efficiency of the extraction process is checked by comparing the tests of the storage liquor with those of the dry bleach and each batch of liquor should be tested daily. it is sometimes advisable to take two samples from each tank, one soon after a tank has been put into operation, and a second sample at the end of the run. considerable differences are occasionally found between these samples and are due, either to inadequate agitation of the liquor in the storage tank, or inefficient mixing in the mixing tank. if the results are irregular the former is the more probable cause but if the second sample is invariably stronger the mixing tank operations should be investigated. the increased concentration of the second sample is due to unextracted bleach passing out of the mixing tank and gradually becoming leached as the tank contents are run off. if the bleach is lumpy and is not subsequently broken up, losses are almost inevitable. hale[3] found that during the period when the new york city supply was being treated with bleach it was necessary to constantly check the operations of the labourers by frequent samples. "during one week about 95 per cent of the chlorine added was actually applied, the second week it dropped to 85 per cent. and the third week to 75 per cent. whenever a poor run is called to the attention of the labourers, results improve." by taking two samples daily from each tank discharged the author has been able to obtain an average annual efficiency on the ottawa plant of 94 per cent., i.e. the solutions contained 94 per cent. of the available chlorine contained in the bleach. in making such checks it is necessary to keep a careful account of the stock of bleach to prevent labourers adding a few extra pounds of bleach to compensate for losses. sludge forms an appreciable but unavoidable source of loss of material. when the sludge reaches the outlet of the hypochlorite pipe the sludge must be run to waste; otherwise it will pass over and tend to choke the dosage control apparatus. if the sludge is run into the same body of water that forms the source of supply, it must be discharged very slowly to prevent a possibility of over dosage and damage to fish life. with proper control, sludge losses can easily be kept under 2 per cent. and often under 1 per cent. the greatest source of unavoidable loss in hypochlorite plants is from deterioration of the bleach during storage; in warm climates this loss may exceed 10 per cent. in ottawa where high temperatures are only experienced during the summer months the loss from this cause has averaged from 7-8 per cent. on the bleach stored during that period. _detection and estimation of free chlorine._ the oldest and probably the best known test for free chlorine in water is the wagner test, made by adding a few drops of potassium iodide and starch; the presence of chlorine is indicated by a deep rich blue colouration that is proportional in intensity to the quantity of chlorine present. when this test is used as a colorimetric method for the estimation of chlorine several difficulties are encountered; the intensity of the colour produced by the majority of treated waters gradually diminishes and the loss is usually more rapid than in the standards made up with distilled water; a different result is obtained if the solutions are acidified and the results vary with different acids, acetic acid yielding a much lower result than a mineral acid such as hydrochloric acid; in the presence of acid the colouration usually intensifies on standing, whereas the standard intensifies but little. the difference caused by the addition of acid is imperfectly understood but it is obvious that the chlorine set free by the acid cannot be present in the "free" state; it is probably in a semi-labile condition loosely attached to organic compounds. whether this semi-labile chlorine is available for germicidal action is at present not definitely known but it has been noted by several observers that the germicidal action proceeds after the "free" chlorine reaction has disappeared. the method used by the author for the estimation of free chlorine is as follows: place 500 c.cms. of the sample in a stoppered bottle, add 1 c.cm. of 5 per cent ki solution, 2 drops of conc. hcl and 1 c.cm. of starch solution and titrate with n/1000 sodium thiosulphate until colourless. the difficulty introduced by the opalescence of the liquid is overcome by pouring portions of the liquid into two nessler tubes and adding a drop of thiosulphate solution to one and noting if any reduction of colour occurs on shaking; if the intensity of the colour is diminished, the contents of both tubes are poured back into the bottle and titrated until no further colour removal, as shown by the tubes, can be obtained. one c.cm. of n/1000 sodium thiosulphate = 0.07 p.p.m. of available chlorine when 500 c.cms. of water are used. adams[4] has employed the colorimetric method of estimating the colour obtained after the addition of dilute h_{2}so_{4}, ki, and starch but used standard solutions of dyes for comparison. the standards were prepared from mixtures of brilliant mill green "s" and cardinal red "j" and were made up weekly. phelps found that ortho-tolidine in acetic acid solution produced an intense yellow colouration with free chlorine and suggested the use of this reagent as a qualitative test for chlorine. ellms and hauser[5] developed this process into a quantitative one and substituted hydrochloric acid for acetic acid as a solvent. one c.cm. of the reagent (1 gram of pure _o_-tolidine dissolved in 1 litre of 10 per cent of hydrochloric acid) is added to 100 c.cms. of the sample in a nessler tube and the colour compared after five minutes with permanent standards made up with mixtures of potassium bichromate and copper sulphate. this method was adopted as the official standard method of the american public health association; the details are given in the appendix (p. 147). the author has found that this method gives excellent results except for coloured waters. the colouring matter in many waters diminishes in intensity on the addition of acids and is somewhat similar in tint to that produced by addition of _o_-tolidine. if the reaction is used qualitatively on coloured treated water and a comparison made with the untreated sample, a negative result, due to the reduction in colour produced by the acid being greater than the increase caused by the reagent, might be obtained when traces of free chlorine are present. similar difficulties are encountered when quantitative comparisons are made against permanent standards. benzidine (wallis[6]) has also been suggested for the detection of free chlorine. on adding this reagent a blue colouration is produced but on stirring it rapidly changes to a bright yellow which is proportional in intensity to the amount of free chlorine present. ellms and hauser[5] investigated benzidine in 1913 and found it to be inferior to _o_-tolidine as a test reagent for free chlorine. leroy[7] has proposed the use of hexamethyltri_para_-aminotriphenylmethane for detecting and estimating free chlorine. on the addition of a hydrochloric acid solution of this compound to a sample containing free chlorine a violet colouration is produced that can be matched in the usual way with standards. it is stated that 0.03 p.p.m. of free chlorine gives a distinct colouration and that the reagent reacts very slowly with nitrites and is quite unaffected by hydrogen peroxide. the starch-iodide and _o_-tolidine reactions are affected by oxidising agents or reducible substances; nitrites and ferric salts are the compounds that are most likely to interfere and ellms and hauser[5] have found that these bodies do not affect the _o_-tolidine reaction to the same extent as the starch-iodide reaction. very small quantities of nitrites (0.03 p.p.m. of n) and ferric salts (0.2 p.p.m. fe) give a blue colouration with the starch-iodide reagent and for this reason it is always advisable, whenever possible, to make a control test on the untreated water. nitrites are oxidised by free chlorine and consequently do not interfere with the estimation of it by the thiosulphate method; the influence of ferric salts can be overcome by substituting 3 c.cms. of 25 per cent phosphoric acid for hydrochloric acid (winkler[8]). an electrical instrument called a "chlorometer" has been devised by e. k. rideal and evans[9] for the estimation of free chlorine. the diagrammatic sketch, reproduced in fig. 5, shows the general construction of the apparatus. when water containing no free chlorine passes through the copper tube, hydrogen is liberated on the platinum rod by the electrolytic solution pressure of the copper and an electric current is generated; a polarizing action follows and the flow of current ceases. when free chlorine is present it combines with the hydrogen as produced and so enables more copper to dissolve and produces a permanent flow of current. the current produced is a function of the depolarizing action, i.e. of the free chlorine, and is indicated by the current meter which is graduated in parts per million of available chlorine. the usual range of instrument is 5 p.p.m. and each division of the scale is equal to one-tenth of one part per million. only strong oxidisers, such as chlorine, ozone, and permanganates, which have a great affinity for hydrogen, are able to produce a permanent current; ferric chloride and other weak oxidisers do not affect the indicator. [illustration: fig. 5.--rideal-evans chlorometer.] costs _cost of construction._ according to the replies received by the committee on water supplies of the american public health association[10] the total cost of equipment for disinfection varies widely and bears no apparent relation to the capacity of the equipment. this is due to the temporary nature of the plants erected in many cities and the necessity of erecting expensive structures in others. the cost of construction varies also in different localities. the cost of equipping hypochlorite plants with standard concrete tanks and dosage regulators would be more uniform and for capacities between 10 and 50 million gallons per day would approximate $15 to $50 per million gallons. _the operating cost_ of bleach plants shows similar wide variations. in some cases the labour required for mixing and supervision can be obtained without extra cost whilst in others the labour charge exceeds the cost of hypochlorite. the price of bleach has shown violent fluctuations during the last three years (see diagram ix, page 125) but is now (1918) comparatively steady at $2.25 to $2.75 per 100 pounds. assuming that 33.3 per cent of available chlorine can be extracted, each pound of chlorine costs 6.75-7.25 cents as compared with 15-25 cents for liquid chlorine. the fixed charges on the capital expenditures together with the labour and incidental charges almost invariably make the total cost of operation of a straight bleach plant higher than that of a liquid chlorine plant. the tendency during the last four years has been to substitute liquid chlorine for hypochlorite and the majority of the plants are now of the former type. "antichlors" substances used for the removal of excess chlorine are usually known as "antichlors" and those that have been most frequently employed are sodium bisulphite, nahso_{3}, and sodium thiosulphate na_{2}s_{2}o_{3}. the reactions with chlorine are: (i) nahso_{3} + cl_{2} + h_{2}o = nahso_{4} + 2hcl. (ii) na_{2}s_{2}o_{3} + cl_{2} = na_{2}s_{4}o_{6} + 2nacl. sodium bisulphite is a very efficient "antichlor," only 1.46 parts being required to remove 1 part of chlorine, but owing to its instability the action is uncertain. sodium thiosulphate is a comparatively stable cheap salt, containing 5 molecules of water of crystallization, na_{2}s_{2}o_{3} · 5h_{2}o but 7 parts are necessary to remove 1 part by weight of chlorine. "antichlors" are used as aqueous solutions and the dosage controlled in the same manner as for bleach solutions. the action is an instantaneous one and it is consequently necessary that the germicidal action should be complete before the "antichlor" is added. filters, containing solid materials capable of absorbing free chlorine, have also been used for removing the excess of the germicidal reagent. iron borings and aluminium were used experimentally by thresh[11] but the process was not commercially developed. the "de chlor" filter, in which carbon is the active substance, has been installed at several water works in england (reading, exeter, aldershot) with apparently successful results. the reading experimental installation, described by walker,[12] consisted of a steel drum, 8 feet 3 inches in width, the top and bottom being domed. in the upper portion, 10 feet 9 inches in depth, provision was made for thorough admixture of the bleach solution and water and a subsequent storage of thirty minutes. the lower section of the filter was divided into three compartments, the first and last of which contained graded silica; the middle compartment was filled with a layer (20 inches deep) of specially prepared granulated charcoal or carbon. the filter was operated under pressure and passed an average of 192,000 imp. gallons per day, the rate being 32,000 imp. gallons per square yard per day. water from the pre-filters (polarite and sand) was treated with bleach to give a concentration of 1 p.p.m. of available chlorine and passed through the de chlor filter. the average bacteriological results obtained during the first six months operation were as follows: bacteria per c.cm. b. coli index gelatine 3 days at 20° c. per 100 c.cms. raw river water 6,775 600 water from pre-filters 579 119 water from de chlor filter 33 nil free chlorine could not be detected by chemical tests in the filtered water which was also free from abnormal tastes and odours. it is stated that the carbon has to be removed and revivified periodically. the filter was washed about once per week, the wash water being only one-tenth of one per cent. the experimental filter was operated for nearly two years before being removed to permit the erection of larger units having a total capacity of one million imp. gallons per day. bibliography [1] hooker. chloride of lime in sanitation, new york, 1913. [2] griffen and hedallen. j. soc. chem. ind., 1915, =34=, 530. [3] hale. proc. n. j. san. assoc., 1914. [4] adams. j. amer. pub. health assoc., 1916, =6=, 867. [5] ellms and hauser. j. ind. and eng. chem., 1913, =5=, 915 and 1030; _ibid._, 1914, =6=, 553. [6] wallis. ind. jour. med. res., 1917, =4=, 797. [7] le roy. comptes rend., 1916, =163=, 226. [8] winkler. zeit. angew. chem., 1915, =28=, 22. [9]: rideal, e. k. and evans. analyst, 1913, =38=, 353. [10] j. amer. pub. health assoc. 1915, =5=, 921. [11] thresh. internat. congress appl. chem., 1908. [12] walker. jour. roy. inst. pub. health, jan., 1911. chapter vii liquid chlorine the use of liquefied chlorine for the disinfection of water was first proposed by lieutenant nesfield[1] of the indian medical service. he stated that: "it occurred to me that chlorine gas might be found satisfactory ... if suitable means could be found for using it.... the next important question was how to render the gas portable. this might be accomplished in two ways: by liquefying it, and storing it in lead-lined iron vessels, having a jet with a very fine capillary canal, and fitted with a tap or a screw cap. the tap is turned on, and the cylinder placed in the amount of water required. the chlorine bubbles out, and in ten to fifteen minutes the water is absolutely safe, and has only to be rendered tasteless by the addition of sodium sulphite made into a cake or tablet.... the cylinders could, of course, be refilled. this method would be of use on a large scale, as for service water carts." the first _practical_ demonstration of the possibilities of this method was made by major darnall[2] of the medical corps, united states army, in 1910. chlorine was taken from steel cylinders and passed through automatic reducing valves which provided a uniform flow of gas for the water requiring treatment. a uniform flow of water was maintained through the mixing pipe and so secured a uniform dosage. this apparatus might be considered as the forerunner of the various commercial types of machines that were developed later and which are being so extensively used at the present time. a working model, having a capacity of 500 gallons per hour, was erected at fort myer, va., and was operated on water that had been treated with alum but had received no further purification. despite the presence of the flocculated organic matter, satisfactory purification was obtained with 0.5 to 1.0 p.p.m. of available chlorine and no taste or odour was imparted to the supply. from the results obtained at fort myer, and washington, d.c., darnall concluded that "in general, it may be said that with an average unfiltered river water such as that of the potomac, about one-half of one part (by weight) of chlorine gas per million of water will be required. for clear lake waters three-tenths to four-tenths of a part per million will be sufficient." a board of officers of the war department examined the results and reported (june, 1911) "that the apparatus is as efficient as purification by ozone or hypochlorite and is more reliable in operation than either.... that it could be installed at a very low cost and that the cost of operation would be very slight." in june, 1912, ornstein experimented with chlorine gas, obtained from the liquefied gas in cylinders, for sewage and water disinfection but his method differed from darnall's in first dissolving the gas in water and feeding the solution to the liquid to be treated. kienle[3] made experiments at wilmington, del., in november, 1912, and obtained a constant flow of gas by means of highand low-pressure valves; the gas was dissolved in water in an absorption tower and afterwards fed to the water to be treated. van loan and thomas of philadelphia experimented with liquid chlorine on a large scale at the belmont filter plant in september, 1912. the chlorine was fed into the filtered water basin in the gaseous state and the quantity was regulated by the loss in weight of the containers. the dosage was approximately 0.14 p.p.m. (west[4]). jackson, of brooklyn, made similar experiments about the same time at the ridgewood reservoir, brooklyn, and his type of apparatus was shortly afterwards put on the market as the leavitt-jackson liquid chlorine machine. the regulation of the flow in this machine was determined by the loss in weight of the gas cylinder which was suspended from a sensitive scale beam. by moving the counterbalancing weight on the beam at a constant rate, a uniform flow of gas was obtained, the area of the orifice being kept constant by the equilibrium in the balance operating controlling valves through a system of levers. this type of apparatus was tried at several places but it was found that the adjustment of the regulating mechanism was too sensitive and produced considerable irregularities in the flow of gas. the type used by ornstein and kienle were combined and commercially developed by the electric bleaching gas co. of new york.[a] in this combined type the gas was collected from one or more cylinders by means of a manifold which delivered it to the regulating mechanism at the pressure indicated by a gauge attached to the inlet pipe. beyond this gauge were two pressure-regulating devices, the first being used primarily to reduce the initial pressure to about 15 pounds per square inch, and the second for controlling the pressure through a range sufficient to give the desired discharge of gas. the gas from the second regulator passed through an orifice in a plate at a pressure indicated by a suitable gauge which was calibrated in terms of weight of chlorine per unit of time. the gas, on leaving the regulating apparatus, passed up an absorption tower of hard rubber, where it met a descending stream of water. the solution was carried by suitable piping to the point of application. this type was modified in some cases by the substitution of a flow meter of the float type for the inferential pressure meter. [a] this type has recently been withdrawn from the market. [illustration: fig. 6.--manual control chlorinator, solution feed, type a.] another type of apparatus, developed by wallace and tiernan,[a] is shown in figs. 6 and 7. the gas under the pressure indicated by the tank pressure gauge (fig. 6) passes into the pressure compensating chamber, which maintains a constant drop in pressure across the chlorine control valve, through the check valve, and into the solution jar after measurement in the pulsating meter. the water required for dissolving the chlorine enters the jar through the feed line and check valve and the solution passes along the feed line after being water sealed in a special chamber. the meter is a volumetric displacement one and is regulated by observing the number of pulsations per minute. each pulsation corresponds to 100 milligrams or 0.00022 pound of chlorine; diagrams for converting pulsations per minute into weight per twenty-four hours are usually provided with the apparatus. this type of meter is suitable for quantities between 0.1 and 12 pounds per day and possesses the distinct advantage of enabling the operator to see the actual delivery of the gas. [a] manufactured by wallace and tiernan co. inc. n. y. [illustration: fig. 7.--manual control chlorinator, solution feed, type b.] the quantities of gas exceeding 12 pounds per day the type shown in fig. 7 may be used. the gas from the control valve passes through a visible glass orifice which is connected with the manometer. this manometer, or chlorine meter, contains carbon tetrachloride and is graduated empirically in terms of weight of chlorine per unit of time. a suitable gauge indicates the back pressure thrown by the check valve and registers the same pressure as the tank gauge when the flow of gas is stopped. the gas passes into the glass cylinder where it is dissolved in water and passes out by the feed pipe. the most accurate range of the orifice type is from 1-6, i.e. if the minimum graduation on the scale is 10, the maximum is 60. if quantities less than the minimum graduation are desired, a smaller orifice with its corresponding scale can be substituted in a few minutes. these types are manually controlled, but automatic control types, to meet almost any condition, can be obtained and are in use in many cities. in some instances (dry-feed types) the chlorine gas is not dissolved in water prior to addition to the water requiring treatment but is carried to the point of application as a dry gas and enters the water through a diffusion plate made of carborundum sponge. the sponge becomes saturated with water because of the capillary action of the carborundum upon the water. the pressure of the chlorine in the feed pipe forces the gas through the diffuser in the form of minute bubbles which become saturated with moisture. on meeting the water they immediately go into solution and no gas escapes. the operation of liquid chlorine machines is exceedingly simple. after the cylinders have been connected, the cylinder valves are opened and the joints tested for leakage by holding a swab of absorbent cotton saturated with strong ammonia under them; a leakage is indicated by the appearance of white fumes of ammonium chloride. the control valve is then slightly opened and the auxiliary cylinder valves partially opened; whilst the pressure in the apparatus is slowly increasing the remainder of the joints are tested and if found to be tight, the cylinder valves are fully opened and the control valve opened to the desired amount. in the solution feed types the water required as solvent is turned on before the control valve is opened. once the apparatus is working, no further attention is required, except for the regulation of the dosage in the manual control types, until the cylinders are replaced. when the stock of gas in the cylinders is almost depleted the pressure falls but it is always preferable to determine the stock by standing the cylinders on a platform scale and weighing at regular intervals. this also provides a check on the apparatus and can be utilised to check the operators. the accumulation of substances that impede the flow of gas is usually slow and is indicated by a gradual increase in the back pressure. the orifice is calibrated at 25 pounds back pressure and any deviation from this figure will show a discrepancy between the actual weight of chlorine evaporated and the amount calculated from the scale reading. liquid chlorine is usually sent out by the manufacturers in steel cylinders which contain about 1.1 cubic feet of liquid or approximately 100 pounds (1 cu. ft. = 89.75 pounds).[a] [a] an effort is now being made to standardise cylinders of 150 lbs. capacity. for small installations only one cylinder is necessary but it is always preferable to connect more than one. when the flow of gas is rapid the temperature of the liquid chlorine falls and reduces the pressure. the effect of the fall in temperature, due to the latent heat of evaporation, can be partially overcome by using a larger number of cylinders; in addition a source of external heat should be provided that will maintain the temperature of the cylinders at a minimum of 80° f. this is a "sine qua non" for successful operation. the effect of the temperature upon the pressure in the cylinders is shown in diagram vii. [illustration: diagram vii chlorine gas pressures at various temperatures] in practice it is found impossible to utilise all the gas contained in the containers; when the cylinders are almost empty the pressure necessary for the operation of the regulating device cannot be obtained and full cylinders must be attached. when sufficient heat is provided the weight of chlorine in the cylinder can be reduced to 1 1-1/2 pounds before the tank pressure becomes too low. liquid chlorine machines will operate, with ordinary care, for long periods. the various parts are made of such metals as experience has demonstrated to be best able to resist the corrosive action of the dry gas and the apparatus is designed to prevent the access of moisture which would otherwise produce corrosion and impede the flow of gas. stoppages are sometimes caused by brown deposits derived from impurities in the liquid chlorine. these are primarily due to variations in the graphite electrodes used in the electrolytic process for the manufacture of chlorine from salt. [illustration: fig. 8.--dunwoodie chlorinating plant treating 400,000,000 gallons per day for new york city.] to convey the dry gas from the apparatus to the point of application, copper or iron pipes may be used; for aqueous solutions, flexible rubber hose must be employed. chlorine water is exceedingly active, chemically, and rapidly attacks all the common metals; ordinary galvanised iron pipe is eroded in a few days and should never be used. liquid chlorine, for water disinfection, possesses several marked advantages over the ordinary bleach process. (1) the sterilising agent is practically 100 per cent pure, the only impurities being traces of carbon dioxide and air, and does not deteriorate on storage; it will, in fact, keep almost indefinitely. (2) liquid chlorine practically eliminates all labour costs because of the simplicity of the apparatus and the concentrated form of the sterilising agent. the apparatus is so compact that all the cylinders and regulating apparatus required for delivering 200 pounds of gas per day can be placed in an area of about 50 square feet and it can consequently be almost invariably accommodated in locations where the trifling amount of attention required can be obtained without extra cost. (3) the sludge problem, inseparable from bleach installations, is eliminated. (4) regulation of the dosage is simpler and consequently usually more accurate. the dosing apparatus in bleach plants invariably tends to choke and demands regular attention from intelligent operators; a similar tendency in liquid chlorine machines is easily detected and electrical devices can be installed to indicate automatically any changes in the flow. (5) the first cost is smaller. the cost of liquid chlorine machines varies from $400, for the small manual control types, to $1,200, for the automatic control types. the capital outlay is mainly determined by the number of machines and accessories required and not, within certain limits, by the capacity. one machine will deliver up to 200 pounds of gas per day, an amount sufficient to treat 60,000,000 u. s. a. gallons (50,000,000 imp. gals.) at 0.40 p.p.m. of available chlorine. unless duplicate machines are installed for the higher rates, the first cost is inversely proportional, though not directly so, to the volume of water treated. it is in all cases less than the first cost of a bleach plant of equal capacity, accuracy, and durability. (6) liquid chlorine installations usually tend to produce less complaints as to tastes and odours. this is probably due, not to any merit of the chlorine _per se_, but to a more accurate regulation of the dosage and efficient distribution of the chlorine in the treated water. the advantages ensuing from thorough admixture had only become partially appreciated before liquid chlorine machines were fully developed and they have been more fully utilised in the design of these later installations. claims have also been made that liquid chlorine prevents "aftergrowths" but no evidence can be adduced in support of this statement. aftergrowths have occurred at many places where this process is employed and in this respect it possesses no advantage over hypochlorite installations. it is also claimed that one pound of liquid chlorine is more efficient, as a germicide, than an equal weight of chlorine in the form of bleach. jackson[5] has stated that 1 pound of chlorine is equal to 9 pounds of bleach; kienle (_loc. cit._) that it was equal to 8 pounds of bleach, whilst huy claimed to have obtained an efficiency ratio of 1:10 at niagara falls, n. y. the conditions of the experiment were not comparable however, in the last mentioned ratio. catlett, at wilmington, n. c. (west[4]) obtained a better bacterial reduction with 1 pound of liquid chlorine than with 6 pounds of bleach. the efficiency ratio of chlorine to bleach has been reported upon by west.[4] from 1910-1913 the mixed filter effluents of the torresdale plant at philadelphia were treated with bleach but in november, 1913 the liquid chlorine process was substituted. on comparing the results obtained during the same months of the two periods it was found that, in general, 1 pound of liquid chlorine gave a slightly higher percentage purification than 6-7 pounds of bleach. similar results were obtained at the other philadelphia plants. the figures published by west show that the hypochlorite solutions used were abnormally strong (3.6-10.4 per cent of available chlorine), a condition that would increase the difficulty of extracting all the soluble hypochlorite. it was found indeed, that, under the most advantageous conditions, only 87 per cent of the available chlorine was extracted. the average chlorine content of the bleach used during 1912-1913 was 36.1 per cent but the figures given would indicate that at least 1.5 per cent, a reduction of 4.6 per cent of the total, was lost during storage. it would seem not improbable that the total loss under average conditions was not less than 20 per cent, which would reduce the efficiency ratio to 1:4.8-5.6. hale[6] also made a comparison of the relative efficiency of liquid chlorine and hypochlorite of lime at new york, and the earlier results agreed with west's ratio of 1:6-7. an investigation showed that large quantities of chlorine were not extracted from the bleach and when this condition was rectified the total loss averaged only 4 per cent and the results obtained were equal to those given by the liquid chlorine machines. hale's comparative figures are given in table xxiii. table xxiii.--comparison of liquid chlorine with efficient use of bleach--(hale) ----------------+----------+-----------+------------+-------------- treatment. | water | number of | chlorine | reduction | treated. | samples. | p.p.m. | of b. coli. ----------------+----------+-----------+------------+-------------- bleach | croton | 84 | 0.27-0.36 | 93% liquid chlorine | bronx | 84 | 0.27-0.36 | 93% ----------------+----------+-----------+------------+--------------hale concluded that, when efficiently used, the ratio of chlorine to bleach required to produce equal bacterial purification, approached 1:3. the results obtained by the author in ottawa are similar to those of hale. during the earlier period of the bleach treatment a dosage of 1.5 p.p.m. of available chlorine was required to obtain satisfactory purification but various improvements that were subsequently made enabled the quantity to be reduced to 0.8 p.p.m. the same raw water usually requires 0.75 to 0.80 p.p.m. of liquid chlorine to obtain the same purification. the total losses in the ottawa bleach plant averaged 6-8 per cent and based on these figures the efficiency ratio is approximately 1:3.5. ratios as low as 1:3.5 can only be obtained by the supervision of a chemist and this analytical control involves additional expense that must be charged against the bleach process. no chemical analyses are necessary for the control of liquid chlorine plants. _disadvantages of liquid chlorine plants._ the main objection to the use of liquid chlorine is that the slight leaks of gas occur occasionally and unless removed by forced ventilation may produce a concentration of chlorine that will injure the operators. pettenkofer and lehmann[7] found that 0.001-0.005 per cent of chlorine in air affected the respiratory organs; 0.04-0.06 per cent produced dangerous symptoms, whilst concentrations exceeding 0.06 per cent rapidly proved fatal. the danger of gas leakages can be eliminated by placing the apparatus in a small separate room provided with a fan and a ventilation duct. by the liberal use of glass in the construction of the room, the operation of the plant can be seen at all times without entering the chamber. a portion of the liquid chlorine apparatus is made of glass and is consequently easily fractured. duplicates of the glass parts should be kept in stock to prevent interrupting the supply of gas; a duplicate machine is also advisable in large installations. _cost of treatment._ prior to the outbreak of war in 1914, liquid chlorine sold at 10-11 cents per pound in small quantities and for 8-9 cents per pound in large shipments. in 1917 the price was 18-20 cents per pound for small quantities and 15 cents upwards for large contracts. canadian prices are 25 per cent higher. the amount of chlorine required for satisfactory disinfection (see chapter iii) depends upon the nature of the water and the cost of treatment varies accordingly. in the majority of plants the cost varies from 25-90 cents per million gallons. _popularity of process._ since 1913, when the first commercial liquid chlorine machines were used, the popularity of this process has increased in a most remarkable manner. in 1913 over 1,700 million gallons per day were treated with hypochlorite; in 1915, 1,000 million gallons per day were treated with liquid chlorine and an approximately equal amount with hypochlorite; in january 1918, the amounts were 3,500 million gallons per day (liquid chlorine) and 500 million gallons per day (hypochlorite). this wonderful development has been largely due to the intrinsic merits of the process and the reliability of the machines manufactured although it has been indirectly assisted by the excessive cost of hypochlorite during 1915-1916. liquid chlorine machines are being used for the purification of water on the western front of the european battlefield. the outfit is a mobile one and consists of a rapid sand filter, liquid chlorine apparatus, a small storage tank and solution tanks. owing to the limited contact period available a large dosage of chlorine is employed and the excess afterwards removed by the addition of a solution of sodium thiosulphate. _chlorine water._ marshall[8] has proposed the use of chlorine water for the sterilisation of water for troops. the solution is contained in ampoules which are of two sizes, one for water carts and the other for water bottles of one quart capacity. the coefficient of solubility of chlorine, from 10°-41° c. is _c_ = 3.0361 0.04196_t_ + 0.0001107_t_^{2}; when _t_ = 10° c. 1 c.cm. of water absorbs 2.58 c.cms. of chlorine or 8.2 m.gr., a quantity sufficient to give a concentration of 1 p.p.m. in 8 litres of water. marshall has stated that, when pure materials are used, chlorine water is stable but the author is unable to confirm this. a saturated solution of chlorine in distilled water lost over 50 per cent of its available chlorine content when stored for five days in the dark at 70° f. the chlorine present as hypochlorous acid increased slightly but the quantity never exceeded very small proportions. chlorine solutions decompose in accordance with the equation, cl_{2} + h_{2}o = 2hcl + o. although chlorine water appears to be of little value because of its instability there appears to be no reason why chlorine hydrate should not be successfully employed. the hydrate was first prepared by faraday[9] by passing chlorine into water surrounded by a freezing mixture. a thick yellow magma resulted from which the crystals of chlorine hydrate were separated by pressing between filter paper at 0° c. the hydrate prepared by faraday was found to have the composition represented by the formula cl·5h_{2}o but later investigators have shown that more concentrated hydrates can be prepared. roozeboom[10] prepared a hydrate represented by the formula cl·4h_{2}o and forcrand[11] one containing only 3-1/2 molecules of water (cl_{2}·7h_{2}o). chlorine hydrate separates into chlorine gas and chlorine water at 9.6° c. in open vessels and at 28.7° c. in closed vessels. pedler[12] has shown that when the ratio of cl_{2}:h_{2}o is 1:64 or greater, the mixture of chlorine hydrate and water exhibits great stability and can be exposed to tropical sunlight for several months without decomposition. cl_{2}·64h_{2}o contains 5.8 per cent of chlorine and about 8. c.cms. would be required to give a concentration of 1 p.p.m. in 110 imp. gallons of water, the usual capacity of a military water cart. bibliography [1] nesfield. public health, 1903, =15=, 601. [2] darnall. j. amer. pub. health assoc., 1911, =1=, 713. [3] kienle. proc. amer. waterworks assoc., 1913, 274. [4] west. j. amer. waterworks assoc., 1914, =1=, 400-446. [5] jackson. proc. amer. waterworks assoc., 1913. [6] hale. proc. n. j. san. assoc., 1914. [7] pettenkofer and lehmann. munich acad., 1887. [8] marshall. conv. amer. elect. chem. soc., 1917. eng. and contr., 1918, =49=, 40. [9] faraday. q. j. s., =15=, 71. [10] roozeboom. rec. trav. chim., 1885, =3=, 59. [11] forcrand. comp. rend., 1902, =134=, 991. [12] pedler. j. c. s., 1890, =83=, 613. chapter viii electrolytic hypochlorites and chlorine since 1889 when webster first proposed the use of electrolysed sea-water as a disinfectant, various attempts have been made to introduce electrolytic hypochlorites for the bactericidal treatment of water and sewage. two of these preparations were named hermite fluid, and electrozone (c.f. page 5). sodium hypochlorite, made by passing chlorine into solutions of caustic soda, or by the decomposition of bleach by sodium carbonate, has also been used and preparations of this character have been sold under such names as eau de javelle, labarraque solution, chloros, and chlorozone. these solutions contain mixtures of sodium hypochlorite and sodium chloride together with some free alkali. chlorozone was the name given by count dienheim-brochoki to a number of preparations patented in 1876 and subsequently down to 1885. they were produced by passing air and chlorine into solutions of caustic soda. lunge and landolt[1] have shown that the air introduced is without effect and that the advantages claimed for chlorozone are illusory. the earliest electrolytic installation on this continent was operated at brewster, n. y., in 1893 and since that date several plants have been erected where local conditions conduced to economical operation. when a uni-directional current of electricity is passed through a solution of sodium chloride, the salt is dissociated and the components liberated, nacl = na + cl. if the elements are not separated, the chlorine combines with the sodium hydrate, formed by the action of the sodium on the water, to form sodium hypochlorite. the equations 2na + 2h_{2}o = 2naoh + h_{2}, and 2naoh + cl_{2} = naocl + nacl + h_{2}o show that only one-half of the chlorine produced is found as hypochlorite; the other half reforming sodium chloride. several types of electrolysers have been used for the production of hypochlorites and chlorine but only two are suitable for water-works purposes: in one, the cathodic and anodic products recombine in the main body of the electrolyte; in the other, the diaphragm process, they are separated as removed and the final products are chlorine gas and a solution containing caustic soda and some undecomposed salt. until a few years ago the non-diaphragm process was the only one used for water treatment and it will consequently be discussed first. _non-diaphragm process._ the theoretical voltage required for the decomposition of sodium chloride is 2.3 but when the products recombine in the electrolyte, side reactions occur which increase the minimum voltage to 3.54. on this basis one kilowatt hour gives 272 ampere hours and as one ampere hour is theoretically capable of producing 1.33 grams of chlorine, 1.21 kilowatt hours are necessary for the production of 1 pound of chlorine by the decomposition of 1.65 pounds of salt. charles watt (1851) discovered this process and was the first to recognize the necessary conditions which are (1) insoluble electrodes, (2) low temperature of electrolyte, and (3) rapid circulation of electrolyte from the cathode to the anode. the control of the temperature is very important, for as it increases, side reactions occur with the formation of chlorates, and the efficiency is decreased. the non-diaphragm cells used in europe (haas and oettel, kellner, hermite, vogelsand, and mather and platt) have been described by kershaw.[2] in the haas and oettel electrolyser the electrodes are composed of carbon but in the other types at least one electrode is made from platinum or a platinum alloy. the dayton electrolyser, which is the cell most familiar in north america, is shown in fig. 9. [illustration: fig. 9.--dayton electrolytic cell.] the outer cell is made of soapstone and is approximately 2-1/2 feet long and 2 feet wide. the main electrodes consist of four pieces of atcheson graphite connected together by screws and metal strips to which is attached a clamp for connecting electrical terminals. circulation of the brine is produced by glass baffle plates and secondary electrodes placed one inch apart between the main electrodes. the cell is intended to be used at 110-volts pressure but by wiring two cells in series a 220-volt circuit may be employed. an inlet and outlet are provided at each end of the tank to permit the direction of the flow to be periodically reversed for the purpose of removing the lime deposit from the graphite plates. the salt solution is prepared in wooden tanks from coarse clean salt (ground rock salt is unsuitable), containing as little iron as possible, in the proportion of 50 pounds to 100 gallons of water. after passing through a gravel or other suitable filter the brine solution is carried by brass pipes to the electrolyser. the rate of flow is adjusted to the temperature of the hypochlorite solution leaving the cell but under normal conditions it is stated that the cell described will pass 40 gallons per hour with a consumption of 70 amperes and produce 2-1/2 pounds of chlorine per hour. this is equal to 8 pounds of salt and 3.08 kilowatt hours per pound of chlorine. after the cells have been operated for several months the efficiency usually falls and 10-11 pounds of salt and 3.5-3.7 kilowatt hours are required for the production of one pound of chlorine. the concentration of the hypochlorite solution is usually about 6 grams per litre. rickard[3] stated that by cooling the dayton cell with ice 1 pound of chlorine could be produced from 2.65 kilowatt hours and 6.9 pounds of sodium chloride; without cooling the figures were 3.62 kilowatt hours and 7.2 pounds of salt. based on the figures that have been obtained from mature cells, the efficiency of the dayton cell as compared with those described by kershaw is as follows: ------------------+----------------------+--------------------- | salt. | power. | per pound of available chlorine. type of cell. +----------+-----------+----------+---------- | pounds. | per cent | kilowatt | efficiency | | consumed. | hours. | per cent. ------------------+----------+-----------+----------+---------- haas and oettel | 10.7 | 15.4 | 3.8 | 31.9 kellner | 7.5 | 22.0 | 2.75 | 43.9 hermite | 11.2 | 14.5 | 2.87 | 42.2 mather and platt | .... | .... | 2.75 | 43.9 dayton | 10.0 | 16.5 | 3.6 | 33.6 theoretical | 1.65 | 100.0 | 1.21 | 100.0 ------------------+----------+-----------+----------+----------the cost of production depends upon local conditions: if alternating current is available at $30 per horse-power per annum, and low-grade salt can be obtained for $5 per ton the cost of 1 pound of chlorine would be -----------------+--------------------------- | cost (cents) per pound of | available chlorine. type of cell. +--------+----------+------- | salt. | current. | total. -----------------+--------+----------+------- haas and oettel | 2.67 | 1.97 | 4.64 kellner | 1.87 | 1.43 | 3.30 hermite | 2.80 | 1.49 | 4.29 dayton | 2.50 | 1.92 | 4.42 -----------------+--------+----------+-------the electrical and chemical efficiencies of the haas and oettel and dayton cells, which contain carbon electrodes, are smaller than those containing platinum electrodes but for water sterilisation the carbon cells have been found to be more suitable. to prevent the action of magnesium salts on the platinum electrodes it is necessary to use a higher grade of salt or to provide means of purification. because of the absence of a base and the presence of chlorides, electrolytic hypochlorite cannot be stored for more than a few hours without appreciable loss of titre. unless used for the treatment of the effluent of a filter plant operated at a fairly constant rate a small storage tank is necessary to compensate for the irregular demand and to provide the head required by orifice feed boxes. small variations can be made by regulating the flow through the cells but large ones are not compatible with efficiency, which is the highest under a constant load. claims have been made that electrolytic hypochlorite is more efficient as a germicide than bleach when compared on the basis of their available chlorine content but no evidence of it has been produced. bleach contains an excess of base, which retards the germicidal action, and electrolytic hypochlorite contains an excess of sodium chloride, which accelerates it (race[4]) but the ultimate effect is the same with both. this is shown in table xxiv. table xxiv.[a]--comparison of bleach with electrolytic hypochlorite ----------------+-------------------++------------------ | bleach. || electrolytic | || hypochlorite. +-------------------++------------------ contact period. | available chlorine. parts per million. +---------+---------++---------+-------- | 0.4 | 0.6 || 0.4 | 0.6 ----------------+---------+---------++---------+-------- nil | 182 | ... || ... | ... 10 minutes | 130 | 10 || 120 | 8 1 hour | 66 | 1 || 60 | 0 2 hours | 3 | 0 || 1 | 0 3-1/2 hours | 0 | 0 || 0 | 0 ----------------+---------+---------++---------+-------- [a] results are b. coli per 10 c.cms. electrolytic hypochlorite has a greater germicidal velocity than bleach but the difference is so small as to be of no practical importance. rabs[5] experimented with various hypochlorites but was unable to find any appreciable differences in their germicidal action. if electrical power can be obtained at a very low cost, or if the cost is merely nominal, as it is when there is an appreciable difference between the normal consumption and the peak load upon which the rate is based, the electrolytic hypochlorite method offers some advantages but in the great majority of plants it cannot economically compete with bleach. the instability of the liquor and cell troubles have also prevented the process being generally utilised. baltimore and cincinnati experimented with this method but did not adopt it. winslow[6] has reported that, owing to the difficulty in obtaining bleach since the outbreak of war, petrograd has used electrolytic hypochlorite made from salt. _diaphragm process._ the various types of diaphragm cells that have been commercially operated are of two varieties: (1) cells with submerged diaphragms and (2) cells in which the electrolyte comes in contact with one face only of an unsubmerged diaphragm. the le sueur, gibbs, crocker, billiter-siemens, nelson, and hargreaves-bird cells are of the submerged diaphragm variety. the nelson cell has been operated for some time at the filtration plant at little falls, n. j. the cells are fed with brine solution previously purified by the addition of soda ash and have given fairly successful results although the cost of maintenance is comparatively high. tolman[7] has reported that several towns in west virginia use a bleach solution prepared by absorbing chlorine, manufactured by the hargreaves-bird process, in lime water; the solution contains about 1.95 per cent of available chlorine. the diaphragms in both the submerged and unsubmerged types are usually constructed either with asbestos paper or cloth, placed in such a manner as to divide the cells into two separate compartments: the anodic, into which the brine is fed and where the chlorine is produced; and the cathodic, where caustic soda is formed. by maintaining the liquor in the anodic compartment at a higher elevation than in the cathodic one, the direction of flow is towards the latter, but owing to osmosis and diffusion the separation is not complete and a portion of the caustic soda passes the diaphragm and produces hypochlorite with a consequent loss of efficiency and rapid deterioration of the anodes. with the exception of the billiter-siemens cell, the submerged diaphragm cells operate at not more than 85 per cent efficiency and the cost of maintenance is usually high. in the non-submerged diaphragm types the invasion of the anodic compartment by caustic is much reduced and the efficiency and life increased. an electrolyser of the non-submerged diaphragm type is the allen-moore cell which has been adopted by the montreal water and power co. this has been described by pitcher and meadows.[8] the general lay-out of the installation is shown in fig. 10, and the essential features are: a salt storage bin having a capacity of 40 tons; the brine saturating and purifying apparatus; duplicate 15 horse-power motor-generator sets; four chlorine cells; and the silver ejectors and distributing lines for carrying the chlorine solution to the point of application. [illustration: fig. 10--brine saturating and purifying equipment.] the brine solution, which is prepared by passing water through the saturators previously filled with salt, is delivered to the two concrete reaction tanks where an amount of soda ash and caustic liquor sufficient to combine with the calcium and magnesium salts is added, and the mixture filtered through sand and stored in the purified brine tanks. to prevent the formation of hypochlorites by the interaction of chlorine and alkali, the alkalinity of the liquor is determined and sufficient hydrochloric acid added to ensure an acidity of 0.01 per cent. the acid brine is delivered at one end of the four cells (fig. 11) each of which is 7 feet long and 20-3/8 inches wide and consumes 600 amperes at 3.3 volts. the cell box is built of concrete and is provided with a perforated wrought iron cathode box and graphite anode plates which are separated by an unsubmerged asbestos paper diaphragm. [illustration: fig. 11.--sections of allen-moore cell.] each cell has a capacity of 32 pounds of chlorine per day and the gas flow is determined by measuring the volume of caustic soda produced in a given period of time and calculating the weight from the volume and concentration as determined by titration with standard acid; each gram of naoh is equal to 0.88 gram of chlorine. the efficiency of the cell is obtained by dividing the number of grams of chlorine produced per hour by the product of the current volume (in amperes) and the factor 1.33, the theoretical production of chlorine for one ampere hour. the average efficiency of the montreal cells was found to be 93 per cent. the installation comprises four cells, one being held in reserve, and the annual cost of producing 90 pounds of chlorine per day is given as $2,500. the details are: salt at $8.00 per ton, delivered $500.00 power, 15 h.p., at $30.00 flat rate 450.00 labour and superintendence 500.00 interest at 6 per cent on capital cost 300.00 depreciation, 15 per cent 750.00 -------- $2,500.00 cost per pound of chlorine = 7.6 cents. the diaphragm cells, like the non-diaphragm ones, operate most efficiently under a constant load; they are consequently suitable for treating the effluent of filter plants. where very cheap electrical power can be obtained, the cost per pound of available chlorine is less for the electrolytic method just described than for liquid chlorine or chlorine obtained from bleach; but this condition obtains in very few places. mr. j. a. meadows has suggested to the author that the cost could be reduced by converting the chlorine gas into hypochlorite and then adding dilute ammonia as in the chloramine process (_vide_ page 115). the caustic liquor, usually run to waste from the cathodic compartment, could be delivered into a feed box from which it would be drawn off by the water injector used for dissolving the chlorine gas. bibliography [1] lunge and landolt. jour. soc. dyers and colourists, nov. 25, 1885. [2] kershaw. jour. soc. chem. ind., 1912, =31=, 54. [3] rickard. quar. bull. ohio board of health, oct.-dec., 1904. [4] race. jour. amer. waterworks assoc., 1918, =5=, 63. [5] rabs. hygienische rundschau, 1901, 11. [6] winslow. public health rpts. u. s. p. h. s., 1917, =32=, 2202. [7] tolman. jour. amer. waterworks assoc., 1917, =4=, 337. [8] pitcher and meadows. jour. amer. waterworks assoc., 1917, =4=, 337. chapter ix chloramine chloramine (nh_{2}cl), a chemical compound in which one of the hydrogen atoms of ammonia has been replaced by chlorine, was discovered by raschig[1] in 1907. chloramine was prepared by cooling dilute solutions of bleach and ammonia and adding the latter to the former contained in a flask surrounded by a freezing mixture. the proportions were as the equivalent weights of anhydrous ammonia and available chlorine (approximately two parts by weight of chlorine to one part by weight of ammonia). after gas evolution had ceased the mixture was saturated with zinc chloride and the magma distilled under reduced pressure. the distillate was a dilute solution of comparatively pure chloramine. the first to notice the effect of ammonia on the germicidal value of hypochlorites was s. rideal[2] who noted that during the chlorination of sewage, the first rapid consumption of chlorine was succeeded by a slower action which continued for days in some instances, and was accompanied by a germicidal action after free chlorine or hypochlorite had disappeared. rideal stated that: "it became evident that chlorine, in supplement to its oxidising action, which had been exhausted, was acting by substitution for hydrogen in ammonia and organic compounds, yielding products more or less germicidal." on investigating the effect of ammonia on hypochlorite it was found that the addition of an equivalent of ammonia to electrolytic hypochlorite increased the carbolic acid coefficient of 2.18, for one per cent available chlorine, to 6.36 (nearly three times the value). further experimental work showed that the increase was due to the formation of chloramine. the author, in 1915, during a series of experiments on the relative germicidal action of hypochlorites, attempted to prepare the ammonium salt by double decomposition of bleach and ammonium oxalate solutions. ca(ocl)_{2} + (nh_{4})_{2}c_{2}o_{4} = cac_{2}o_{4} + 2nh_{4}ocl. the velocity of the germicidal action of the solution was found to be about ten times greater than the germicidal velocities of other hypochlorites of equal concentrations, (race[3]), and from a consideration of the chemical formula of ammonium hypochlorite it appeared probable that it would be very unstable and decompose into chloramine, which rideal had previously shown to have an abnormal germicidal action, and water. nh_{4}ocl = nh_{2}cl + h_{2}o. after these results have been confirmed, the effect of adding ammonia to bleach solution was tried and it was found that 0.20 p.p.m. of available chlorine and 0.10 p.p.m. of ammonia produced equally good results as 0.60 p.p.m. of chlorine only. similar results were obtained on the addition of ammonia to electrolytic hypochlorite. experiments made with a view to determining the most efficient ratios of ammonia gave very surprising results: chlorine to ammonia ratios (by weight) between 8:1 and 1:2 gave approximately the same germicidal velocity.[3] the action of the ammonia on the oxidising power of bleach, as measured by the indigo test, was also found to be disproportionate to the amount added. the oxidising action of various mixtures of bleach and ammonia as measured by the rate of absorption of the available by the organic matter in the ottawa river water is shown in table xxv. table xxv.--rate of absorption of available chlorine --------------------------+---------------------------------- ratio chlorine / ammonia | percentage of original found after by weight. +-----------+-----------+---------- | 10 mins. | 4 hours. | 20 hours. --------------------------+-----------+-----------+---------- infinity (ammonia absent) | 66.8 | 40.0 | 25.1 8:1 | 83.2 | 77.8 | 67.3 4:1 | 97.2 | 94.7 | 88.5 2.7:1 | 98.3 | 96.5 | 92.8 2:1 | 99.8 | 98.2 | 96.2 --------------------------+-----------+-----------+----------the 8:1 ratio caused a marked reduction in the rate of absorption of the chlorine whilst a 4:1 ratio was almost as active as the ratios containing more ammonia. at the time when the abnormal results were obtained with ammonium hypochlorite and mixtures of bleach and ammonia, the phenomenon appeared to be of scientific interest only and especially so as rideal had attributed the obnoxious tastes and odours, sometimes produced by chlorination, to the formation of chloramines. during the winter of 1915-1916 the price of bleach, however, advanced to extraordinary heights and the author then determined to try out the process on a practical scale for the purification of water. a subsidiary plant pumping about 200,000 imperial gallons per day (240,000 u. s. a. gallons) was found to be available for this purpose and the chloramine process was substituted for the bleach method previously in operation. the process was commenced by the addition of pure ammonia fort, in the amount required to give a chlorine to ammonia ratio of 2:1, to the bleach solutions in the barrels. the results were not in accordance with those obtained in the laboratory and it was found that the samples of bleach solutions received for analysis were far below the strength calculated from the amount of dry bleach used. this experience was repeated on subsequent days and the deficiency was found to increase on increasing the ammonia dosage. solutions of similar concentration were then used in the laboratory with similar losses, and it was observed that on the addition of ammonia a copious evolution of gas occurred. an investigation showed that the ammonia and bleach must be mixed as dilute solutions and prolonged contact avoided (_vide_ p. 127). alterations were accordingly made in the plant and the bleach and ammonia were prepared as dilute solutions in separate vessels and allowed to mix for only a few seconds before delivery to the suction of the pumps. this method of application was instantaneously successful and results equal to those obtained in the laboratory were at once secured. the dosage was reduced until the bacteriological results were adversely affected and continued at values slightly in excess of this figure (0.15 p.p.m.) for a short period to prove that the process was reliable. from a consideration of the work of raschig and rideal, it appeared that the most efficient proportions of available chlorine and ammonia would be two parts by weight of the former to one part of the latter and this ratio was maintained during the run on the experimental plant. lower ratios of chlorine to ammonia were contra-indicated by the laboratory experiments, which showed that the efficiency was not increased thereby whilst higher ratios were left for future consideration. the results obtained on the experimental plant, together with those obtained on the main plant, where 24 million gallons per day were treated with bleach only, are given in tables xxvi, xxvii and xxviii. the two periods given represent the spring flood condition and that immediately preceding it; these are respectively the worst and best water periods. the results in both cases are from samples examined approximately two hours after the application of the chemicals. the cost data were calculated on the current new york prices of bleach and ammonia. table xxvi.--comparison of hypochlorite and chloramine treatment bacteriological results -----+------------------+----------------------+--------------------------- | raw water. | treated with hypo | treated with hypochlorite | | chlorite alone. | and ammonia. +------------+-----+-----------+-----+----+------------+-----+----+--- 1916 | bacteria | | bacteria | | | bacteria | | | | per cubic | | per cubic | | | per cubic | | | |centimeter. | _b. |centimeter.| _b. | |centimeter. | _b. | | +-----+------+coli_+-----+-----+coli_| +------------+coli_| | |agar | agar |index|agar |agar |index| (1)|agar |agar |index| (1)| (2) | 1 | 3 | per | 1 | 3 | per | | 1 | 3 | per | | | day | days | 100 | day |days | 100 | | day | days | 100 | | | at | at | cc. | at | at | cc. | | at | at | cc. | | | 37° | 20° | | 37° | 20° | | | 37° | 20° | | | | c. | c. | | c. | c. | | | c. | c. | | | -----+-----+------+-----+-----+-----+-----+----+-----+------+-----+----+--- mar. | 44| 238| 35.7| 4 | 12 |<0.14|0.90| 4 | 12 |0.14 |0.22|0.11 15-31| | | | | | | | | | | | april|3,099|14,408|195.5| 32 | 56 | 0.50|1.10| 33 |246 |0.74 |0.25|0.13 1-19 | | | | | | | | | | | | -----+-----+------+-----+-----+-----+-----+----+-----+------+-----+----+--- legend: (1) available chlorine parts per million. (2) ammonia, parts per million. table xxvii _percentage reduction_ -------+---------------------------------+------------------------------- | hypochlorite alone. | hypochlorite and ammonia. +---------------+-------+---------+--------------+-------+-------- | bacteria | |available| bacteria | |available | per cubic | _b. |chlorine | per cubic | _b. |chlorine | centimeter. | coli_ | parts | centimeter. | coli_ | parts +------+--------+ index | per +------+-------+ index | per | agar | agar |per 100|million. | agar | agar |per 100|million. |1 day | 3 days | cubic | |1 day |3 days | cubic | | at | at |centi| | at | at |centi| |37° c.| 20° c. |meters.| |37° c.| 20° c.|meters.| -------+------+--------+-------+---------+------+-------+-------+-------- mar. | 90.9 | 95.8 | 99.9+ | 0.90 | 90.0 | 95.0 | 99.7| 0.22 15-31| | | | | | | | april | 98.9 | 99.6 | 99.7 | 1.10 | 98.3 | 98.9 | 99.6| 0.25 1-19 | | | | | | | | -------+------+--------+-------+---------+------+-------+-------+--------table xxviii _cost per million imperial gallons_[a] -----------+--------------+------------- | hypochlorite | hypochlorite | alone. | and ammonia. -----------+--------------+------------- mar. 15-31 | $1.12 | $0.46 april | 1.26 | 0.54 -----------+--------------+------------- [a] calculated as bleach at $3.80 per 100 pounds and aqua ammonia (26° bé.) at 5-1/2 cents per pound. the results were so satisfactory that the author recommended the adoption of the process on the main chlorinating plant but owing to conditions imposed by the provincial board of health the process was not operated until february, 1917. in place of ammonia fort, aqua ammonia (26° bé.), containing approximately 29 per cent of anhydrous ammonia, was used. the material was first examined by the presence of such noxious substance as cyanides and found to be very satisfactory. [illustration: fig. 12.--sketch of ottawa chloramine plant.] the general design of the plant is shown in fig. 12. the bleach is mixed in tank _a_ as a solution containing 0.3 to 0.6 per cent of available chlorine and delivered to tanks _b_ and _d_, each of which has a twenty-four-hour storage capacity. the ammonia solution is mixed and stored in tank _b_ and contains 0.3-0.5 per cent of anhydrous ammonia. the two solutions are run off into boxes _e_ and _f_ which maintain a constant head on valves _v_ and _v'_ controlling the head on the orifices. both orifices discharge into a common feed box _g_ from which the mixture is carried by the water injector _j_ through one of duplicate feed pipes and discharged into the suction well through a perforated pipe. as tank _b_ was previously used as a bleach storage tank, the change from hypochlorite alone to chloramine necessitated very little expense. the treatment was commenced by gradually increasing the quantity of ammonia, until a dosage of 0.12 p.p.m. was reached, and constantly increasing the dosage of bleach, which was formerly 0.93 p.p.m. of available chlorine. owing to the restrictions imposed by the provincial authorities it has not been possible to maintain a dosage as low as that indicated as sufficient by the experimental plants results, but some interesting data have been obtained. table xxix shows the results obtained from february to october, 1917, from the chloramine treatment at ottawa and also those obtained with liquid chlorine at hull where the same raw water is treated with 0.7-0.8 p.p.m. of chlorine. table xxix.--chloramine results at ottawa ---------+--------------+----------+--------+------------------+------ | _b. coli_ | | | | hull |per 100 c.cms.| | | dosage p.p.m. |_b. coli_ 1917 +------+-------+turbidity.| colour.+---------+--------+per 100 | raw | tap | | | | |c.cms. |water.| water.| | |chlorine.|ammonia.| ---------+------+-------+----------+--------+---------+--------+------ feb. | 268 | 0.88 | 3 | 40 | 0.57 | 0.05 | .... mar. 1-18| 250 | 0.96 | 4 | 40 | 0.32 | 0.11 | .... mar. 1-31| 643 | 0.43 | 4 | 40 | 0.47 | 0.14 | .... april | 5228 | 0.34 | 31 | 32 | 0.56 | 0.10 | .... may | 162 | <0.08 | 3 | 39 | 0.52 | 0.08 | .... june | 114 | <0.08 | 3 | 41 | 0.51 | 0.08 | .... july | 237 | 0.08 | 5 | 41 | 0.51 | 0.08 | 44.4 aug. | 165 | 0.08 | 4 | 42 | 0.51 | 0.10 | 28.0 sept. | 55 | <0.08 | 6 | 42 | 0.50 | 0.09 | 15.2 oct. | 31 | 0.15 | 5 | 42 | 0.42 | 0.08 | 1.1 ---------+------+-------+----------+--------+---------+--------+ average | 211 | 0.22 | 7 | 40 | 0.51 | 0.09 | ---------+------+-------+----------+--------+---------+--------+------at the height of the spring floods the raw water contained 80 p.p.m. of turbidity and over 500 _b. coli_ per c.cm. but 0.6 p.p.m. of chlorine and 0.13 p.p.m. of ammonia reduced the _b. coli_ index in the tap samples to 2.5 per 100 c.cms.; samples taken in hull on the same day (treated with 0.7-0.8 p.p.m. of liquid chlorine) gave a _b. coli_ index of 26.7. previous experiences in ottawa has shown that a dosage of approximately 1.5 p.p.m. of available chlorine is required to reduce the _b. coli_ index to 2.0 per 100 c.cms. under similar physical and bacteriological conditions. during the period of nine months covered by the results in table xxix, only five cases of typhoid fever were reported in which the evidence did not clearly indicate that the infection had occurred outside the city. the reduction in the bleach consumed during the same period effected a saving of $3,200. during one period of operation the hypochlorite dosage was gradually reduced to ascertain what factor of safety was maintained with a dosage of 0.5 p.p.m. of available chlorine and 0.06-0.08 p.p.m. of ammonia. the results are shown in diagram viii. the percentage of samples of treated water showing _b. coli_ in 50 c.cms. was calculated from the results of the examination of 4-7 samples daily. the results showed that it was possible to reduce the chlorine dosage to 0.25 p.p.m. with 0.06 p.p.m. of ammonia without adversely affecting the bacteriological purity of the tap supply and fully confirmed the experimental results previously obtained. the lowest ratio of available chlorine to ammonia used during this test was approximately 4:1. this is the ratio indicated by a consideration of the theory of the reaction, and not 2:1 as was formerly stated (race[4]). if bleach is represented as ca(ocl)_{2}, the equation ca(ocl)_{2} + 2nh_{3} = 2nh_{2}cl + ca(oh)_{2} would indicate a ratio of 2:1; but only one molecule of ca(ocl)_{2} is produced from two molecules of bleach and the theoretical ratio is therefore 4:1 (142:34), 2caocl_{2} = cacl_{2} + ca(ocl)_{2} and ca(ocl)_{2} + 2nh_{3} = cl = 142 34 = 2nh_{2}cl + ca(oh)_{2}. the chlorine to ammonia ratio is very important because of its influence on the economics of the process (_vide_ p. 124). [illustration: diagram viii chloramine treatment, ottawa] all the laboratory and works results that have been obtained in ottawa indicate the importance of an adequate contact period. the superiority of chloramine over other processes is due to the non-absorption of the germicidal agent and to obtain the same degree of efficiency the contact period must be increased as the concentration is decreased. for this reason the best results will be obtained by chlorinating at the entrance to reservoirs or under other conditions that will ensure several hours contact. at ottawa the capacity of the pipes connecting the pumping station (point of chlorination) and the distribution mains provides a contact period of one and a quarter hours but even better results would be obtained if the contact period were increased. the general results obtained during the use of chloramine at ottawa in 1917 have shown that the aftergrowths noted during the use of hypochlorite (see p. 56) have been entirely eliminated and that the _b. coli_ content of the tap samples from outlying districts has been invariably less than that of samples taken from taps near to the point of application of the chloramine. at denver, col., where the chloramine process has also been used, similar results were obtained[5]: four days after the initiation of the chloramine treatment the aftergrowth count on gelatine of the capitol hill reservoir dropped from 15,000 to 10 per c.cm. the hypochlorite dosage was cut from 0.26-0.13 p.p.m. of available chlorine and 0.065 p.p.m. of ammonia added. _economics of the chloramine process._ the chloramine process was introduced at ottawa for the purpose of obtaining relief from the effect of the high price of bleach caused by the cessation of imports from europe in 1915. the results obtained with the experimental plant indicated that, calculated on the prices current at the beginning of 1917, appreciable economies could be made. although the reduction in the chlorine dosage has not been as great as was anticipated, due to the restrictions previously mentioned, the cost of sterilising chemicals in 1917 was $3,200 less than the cost of straight hypochlorite treatment. during the latter part of 1917 the relative cost of bleach and ammonia changed (see diagram ix). when calculated on the new york prices for january, 1918, the cost of chloramine treatment in the united states would be greater than hypochlorite alone unless a large reduction in the dosage could be secured by very long contact periods. this condition is only temporary, however, and the price of ammonia will probably gradually decline as the plants for fixation of atmospheric nitrogen commence operations and reduce the demand for the ammonia produced from ammoniacal gas liquor. in canada, the market conditions are still (1918) favourable to the chloramine process: bleach is 25 per cent higher than the u.s.a. product and ammonia can be obtained for one-half the new york prices. [illustration: diagram ix bleach and ammonia prices] _advantages of the chloramine process._ although the market conditions may, in some instances, be unfavourable to the chloramine process, the method possesses certain advantages that more than offset a slight possible increase in the cost of materials. the taste and odour of chloramine is even more pungent than that of chlorine but since the introduction of the process in ottawa no complaints have been received. owing to the reduced dosage, slight proportional fluctuations in the dosage do not produce the same variations in the amount of free chlorine which is the usual cause of complaints. a public announcement that the amount of hypochlorite has been reduced also has a psychological effect upon the consumers and tends to reduce complaints due to auto-suggestion. the most important advantage of the process is the elimination of the aftergrowth problem. at denver, where the aftergrowth trouble is possibly more acute than at any other city on the continent, it was effectively banished by the use of chloramine. at ottawa, the sanitary significance of _b. coli_ aftergrowths is no longer of practical interest because such aftergrowths have ceased to occur. whatever may be their opinion as to the sanitary significance of aftergrowths, all water sanitarians will agree that the better policy is to prevent their occurrence. _operation of chloramine process._ for the successful operation of the chloramine process, the essential factors are low concentrations of the hypochlorite and ammonia solutions. the author has found that hypochlorite containing 0.3-0.5 per cent of available chlorine and ammonia containing 0.3-0.5 per cent of anhydrous ammonia can be mixed in a 4:1 or 8:1 ratio without appreciable loss in titre. solutions of these concentrations mixed in 4:1 ratio lost only 2-3 per cent of available chlorine in fifteen minutes and less than 10 per cent in five hours. the effect of mixing solutions containing 4.35 per cent of available chlorine and 2.2 per cent of ammonia is shown in table xxx. the stability of chloramine is a function of the concentration and the temperature and in practice it will be found advisable to determine in the laboratory the maximum concentrations that can be used at the maximum temperature attained by the water to be treated (cf. muspratt and smith[6]). according to raschig[1] two competing reactions occur when ammonia is in excess. (1) nh_{2}cl + nh_{3} = n_{2}h_{4}hcl hydrazine hydrochloride and (2) 3nh_{2}cl + 2nh_{3} = n_{2} + 3nh_{4}cl. when the excess of ammonia is large, as on the addition of ammonia fort, the second reaction predominates and the yield of nitrogen gas is almost quantitatively proportional to the quantity of available chlorine present. as ammonium chloride has no germicidal action, and hydrazine a carbolic coefficient of only 0.24 (rideal), the formation of these compounds should be avoided. table xxx.--loss on mixing hypochlorite and ammonia hypochlorite containing 4.35 per cent available chlorine. ammonia contained 2.2 per cent nh_{3} -----------------------------+------------------------------------ | loss of available chlorine after ratio chlorine to ammonia by +--------------+----------+---------- weight. | few minutes. | 1 hour. | 24 hours. -----------------------------+--------------+----------+---------- | per cent | per cent | per cent 6:1 | 19 | 19 | 19 4:1 | 24 | 25 | 25 2:1 | 45 | 47 | 47 1:1 | 91 | 91 | 92 1:2 | 20 | 28 | 65 -----------------------------+--------------+----------+----------the dosage of chloramine can be checked by titration of the available chlorine (see p. 82) immediately after treatment or by the estimation of the increment in the total ammonia (free and albuminoid). routine determinations of the latter made in ottawa show that practically the whole (90-95 per cent) of the added ammonia can be recovered by distillation with alkaline permanganate and that 85-90 per cent is in the "free" condition. in operating the chloramine process it is important that the pipes used for conveying the chloramine solution should be of ample dimensions and provided with facilities for blowing out the lime that deposits from the solution. ca(ocl)_{2} + 2nh_{3} = 2nh_{2}cl + ca(oh)_{2}. the marked activity of chloramine as a chlorinating agent could be predicated from its heat of formation, which is 8,230 calories. the other possible chloramines should be even more active as the heat of formation of these compounds are: dichloramine nhcl_{2} -36,780 calories. nitrogen trichloride ncl_{3} -65,330 calories. dichloramine is unknown but nitrogen chloride has been prepared and is a highly explosive yellow oil that decomposes slowly when kept under water in the ice box. ncl_{3} can be easily prepared by passing chlorine gas into a solution of ammonium chloride and this process would suggest that a method might be found of utilising chlorine and ammonia as gases for the production of nitrogen trichloride as a germicide for water chlorination. nh_{4}cl + 3cl_{2} = ncl_{3} + 4hcl. the "available" chlorine content of the chloramines is double the actual chlorine content as each atom of chlorine will liberate two atoms of iodine from hydriodic acid. nh_{2}cl + 2hi = i_{2} + nh_{4}cl. ncl_{3} + 6hi = 3i_{2} + nh_{4}cl + 2hcl. halazone for the sterilisation of small individual quantities of water such as are required by cavalry and other mobile troops bleach and acid sulphate tablets have been usually employed. such tablets have given fairly satisfactory results but certain difficulties inherent to these chemicals have made it desirable to seek other methods. the subject was investigated by dakin and dunham,[7] who first tried chloramine-t (sodium toluene-_p_-sulphochloramide). it was found that heavily contaminated waters, and particularly those containing much carbonates, required a comparatively high concentration of the disinfectant: 40 parts per million of chloramine-t were necessary in some cases and such an amount was distinctly unpalatable. by adding tartaric acid or citric acid the effective concentration could be reduced to 4 p.p.m. but the mixture could not be made into a tablet without decomposition and a two-tablet system was deemed undesirable. toluene sulphodichloramines were next tried. excellent bacteriological results were obtained but the manufacture of tablets again presented difficulties. when the necessary quantity of dichloramine was mixed with what were assumed to be inert salts--sodium chloride for example--the normal slow rate of decomposition was accelerated. the dichloramine, in tablet form, was also found to be too insoluble to effect prompt sterilisation. the most suitable substance found by dakin and dunham was "halazone" or _p_-sulphodichloraminobenzoic acid (cl_{2}n·o_{2}s·c_{6}h_{4}·cooh). this compound is easily prepared from cheap readily available materials and was found to be effective and reasonably stable. the starting point in the preparation of halazone is _p_-toluenesulphonic chloride, a cheap waste product in the manufacture of saccharine. by the action of ammonia, _p_-toluene sulphonamide is produced and is subsequently oxidised by bichromate and sulphuric acid to _p_-sulphonamidobenzoic acid. this acid, on chlorination at low temperatures, yields _p_-sulphondichloraminobenzoic acid (halazone). the reactions may be expressed as follows: ch_{3} cooh cooh / \ / \ / \ | | --> | | --> | | \ / \ / \ / so_{2}·nh_{3} so_{2}·nh_{2} so_{2}·ncl_{2} halazone is a white crystalline solid, sparingly soluble in water and chloroform, and insoluble in petroleum. it readily dissolves in glacial acetic acid from which it crystallizes in prisms (m.p. 213° c.). the purity of the compound can be ascertained by dissolving in glacial acetic acid, adding potassium iodide, and titrating with thiosulphate; 0.1 gram should require 14.8 to 14.9 c.cms. of n/10 sodium thiosulphate. each chlorine atom in halazone is equivalent to 1 molecule of hypochlorous acid and the "available" chlorine content is consequently 52.5 per cent or double the actual chlorine content. >so_{2}·ncl_{2} + 4hi = >so_{2}·nh_{2} + 2hcl + 2i_{2}. from the bacteriological results given by dakin and dunham it would appear that 3 parts per million of halazone (1.5 p.p.m. available chlorine) are sufficient to sterilise heavily polluted waters in thirty minutes and that this concentration can be relied upon to remove pathogenic organisms. the formula recommended for the preparation of tablets is halazone 4 per cent, sodium carbonate, 4 per cent (or dried borax 8 per cent), and sodium chloride (pure) 92 per cent. halazone and halazone tablets, when tested in the author's laboratory on the coloured ottawa river water seeded with _b. coli_, have given rather inferior results. with 1 tablet per quart, over six hours were required to reduce a _b. coli_ content of 100 per 10 c.cms. to less than 1 per 10 c.cms. clear well waters gave excellent results and large numbers of _b. coli_ were reduced to less than 1 per 10 c.cms. in less than thirty minutes. mccrady[a] has also obtained excellent results with various strains of _b. coli_ seeded into the colourless st. lawrence water. [a] private communication. bibliography [1] raschig. chem. zeit., 1907, =31=, 926. [2] rideal. s. j. roy. san. inst., 1910, =31=, 33-45. [3] race. j. amer. waterworks assoc., 1918, =5=, 63. [4] race. eng. and contr., 1917, =47=, 251. [5] contract record. aug. 15, 1917, 696. [6] muspratt and smith. j. soc. chem. ind., 1898, =17=, 529. [7] dakin and dunham. brit. med. jour., 1917, no. 2943, 682. chapter x results obtained the object of adding chlorine or chlorine compounds to water is for the purpose of destroying any pathogenic organisms that may be present. in a few instances some collateral advantages are also obtained but, in general, no other object is aimed at or secured. chlorination does not change the physical appearance of water; it does not reduce or increase the turbidity nor does it decrease the colour in an appreciable degree. the chemical composition is also practically unaltered. when bleach is used there is a proportionate increase in the hardness but the amount is usually trifling and is without significance. during 1916 when the ottawa supply was entirely treated with bleach at the rate of 2.7 parts per million (0.92 p.p.m. of available chlorine) the average increase in the total hardness as determined by the soap method was 2.5 parts per million. when chlorine is added to prefiltered water, as an adjunct to filtration, an increase in the number of gallons filtered per run has been noted at some plants. this increase is not so great with rapid as with slow sand filters but in some instances it has led to appreciable economies. walden and powell[1] of baltimore, found that the addition of a quantity of bleach equal to approximately 0.50 p.p.m. of available chlorine enabled the alum to be reduced from 0.87 to 0.58 grain per gallon. the percentage of water used in washing the filters was also reduced, from 4.1 per cent to 2.9 per cent, whilst the filter runs were increased on the average by one hour and ten minutes. the net saving in coagulant alone amounted to 30 cents per million gallons. clark and de gage[2] found that the use of smaller amounts of coagulant during the period of combined disinfection and coagulation resulted in an increase of nearly 25 per cent in the quantity of water passed through the filter between washings, and also in a material reduction of the cost of chemicals, which averaged $2.62 per million gallons for combined disinfection and coagulation as against $4.86 for coagulation alone. the water used in these experiments was obtained from the merrimac river at lawrence. the effect of hypochlorite on the reduction of algæ growths on slow sand filters was first noticed by houston during the treatment of the lincoln supply in 1905. two open service reservoirs were fed with treated water and were themselves dosed from time to time. "previous to 1905 they developed seasonally most abundant growths, but during the hypochlorite treatment it was noticed that they remained bright, clear, and remarkably free from growths" (houston[3]). ellms,[4] of cincinnati, has also noted the effect of hypochlorite on algæ. when the bleach was added to the coagulated water the destruction of the plankton was not as satisfactory as had been anticipated and it was found that large doses destroyed the coating of the sand particles and rendered the filters less efficient. the use of bleach in the filtered water basin was more successful and cleared it of troublesome growths. in 1916, during the treatment of the london supply with bleach (dosage 0.5 p.p.m. of available chlorine), houston made further observations on this point. the thames water, taken at staines, had previously been stored for considerable periods in reservoirs, but this necessitated lifting the water by pumps which consumed large quantities of coal that were urgently needed for national purposes. as a war measure, the storage was eliminated and the water treated with hypochlorite at staines and allowed to flow by gravitation to the various works where the slow sand filters are situated. the treatment resulted in a marked reduction in the growths of algæ, the reduction in the area of filters cleaned in 1916 (june to september) as compared with 1915 being as follows: percentage filter works. reduction (approximate). grand junction (hampton) 6 grand junction (kew) 43 east london (sunbury) 30 kempton park 33 west middlesex 56 a portion of this reduction can probably be attributed to the elimination of storage. chlorination, by decreasing the load on filter beds, has enabled the rate of filtration to be increased in some cases. this increased capacity, which would otherwise have necessitated additional filter units, has been obtained without any further capital outlay. at pittsburg (johnson[5]) the rate of filtration, after cleaning, was increased 250,000 gallons each hour until the normal rate was reached; restored beds were maintained at a 250,000 gallon rate for one week. after the introduction of chlorination it was found possible to increase the rates more rapidly without adversely affecting the purity of the mixed filter affluents. _hygienic results._ evidence as to the actual reduction of the number of such pathogenic germs as _b. typhosus_ in water supplies by chlorination is most readily found in the death rates from typhoid fever in cities that have no other means of water purification. in some cases this evidence is necessarily of a circumstantial nature; in others it is definite and conclusive. some of the earlier results of the effect of chlorination on typhoid morbidity and mortality rates were compiled by jennings[6] and others have been published by longley.[7] these data have been brought up to date in table xxxi and other statistics added. table xxxi.--effect of chlorination on typhoid rates average typhoid death rate per 100,000 population ----------------+-------------+--------------+--------------+---------- city. | commenced | before using.| after using. | |chlorination.+-------+------+-------+------+ percentage | |period.|rate. |period.|rate. | reduction. ----------------+-------------+-------+------+-------+------+---------- baltimore |june 1911 |1900-10| 35.2 |1912-15| 22.2 | 36 cleveland |sept. 1911 |1900-10| 35.5 |1912-16| 8.2 | 77 des moines |dec. 1910 |1905-10| 22.7 |1911-13| 13.4 | 41 erie |mar. 1911 |1906-10| 50.6 |1912-14| 15.0 | 70 evanston, ill. |dec. 1911 |1908-11| 29.0 |1912-13| 14.5 | 50 jersey city |sept. 1908 |1900-17| 18.7 |1909-16| 8.4 | 55 kansas city, mo.|jan. 1911 |1900-10| 42.5 |1911-16| 14.2 | 66 omaha, neb. |may 1910 |1900-09| 22.5 |1911-16| 10.6 | 53 trenton |dec. 1911 |1907-11| 46.0 |1911-14| 28.7 | 35 montreal |feb. 1910 |1906-10| 40.0 |1911-16| 25.0 | 37 toronto |apr. 1911 |1906-10| 31.2 |1912-16| 7.8 | 75 ottawa |sept. 1912 |1906-10| 34.0 |1913-17| 17.0 | 50 ----------------+-------------+-------+------+-------+------+----------the figures given in this table show the effect of chlorination only; no other form of purification was used during the periods given, except at toronto where a portion of the supply has been subjected to filtration. it will be seen that since chlorination was adopted the typhoid death rates have been reduced by approximately 50 per cent and that the averages for the period after treatment are almost invariably less than 20 per 100,000, a figure that a few years ago was regarded as satisfactory. the average death rate for the last available year is 11 per 100,000, a result that is even more satisfactory and exceeds the anticipations of the most optimistic of sanitarians. a portion of the reduction in the typhoid rates is no doubt due to improvements in general sanitary conditions but the reduction is much greater than can be accounted for in that manner alone and in many cases there was a sharp decline immediately following the commencement of chlorination. in a few instances there is evidence that chlorination has reduced the typhoid rates of cities previously supplied with filtered water. diagram x, drawn from data supplied by dr. west, of the torresdale filtration plant, shows the effect of disinfecting the filter effluents at philadelphia. [illustration: diagram x typhoid in philadelphia] during the years 1909-10-11, when practically the whole of the city supply was filtered, the average typhoid death rate was 18, but when the water was also chlorinated, in 1914-15-16, the rate was only 7, a reduction of 61 per cent. the figures in table xxxii show that the torresdale filters, during 1915-16 were unable to adequately purify the water and that chlorination was necessary. table xxxii.--chlorination of filter effluents (torresdale) ----+---------+---------+----------+--------------------------------- | | | | bacteria per cubic centimeter. | oxygen | | +-----------------+--------------- |consumed.| colour. |turbidity.| untreated. | treated. | | | +---------+-------+---------+----- | | | |gelatine.| agar. |gelatine.| agar. ----+---------+---------+----------+---------+-------+---------+----- 1915| 1.70 | 12 | 0.6 | 141 | 30 | 28 | 14 1916| 1.90 | 12 | nil. | 88 | 23 | 38 | 11 ====+=========+=========+==========+=========+=======+=========+====== | _b. coli communis_ | | per cent positive tests. | +----------------------+-------------------------+ | untreated. | treated. | added chlorine +----------+-----------+------------+------------+ parts per |10 c.cms. | 1 c.cm. | 10 c.cms. | 1 c.cm. | million. ----+----------+-----------+------------+------------+--------------- 1915| 66 | 24 | 5 | 0.3 | 0.18 1916| 49 | 16 | 7.4 | 1.9 | 0.15 ----+----------+-----------+------------+------------+---------------in diagram xi the typhoid death rates of columbus, ohio, and new orleans are shown to exemplify conditions that have not been improved by chlorination. the endemic condition of typhoid in columbus was brought to an abrupt conclusion by the installation and operation of the softening and filter plant in september, 1908, and no further reduction followed the introduction of chlorination in december, 1909. in new orleans the typhoid rate decreased on the inception of the new water works system in 1909 and again after the installation of the carrollton filters in 1912. the product of the filtration plants has always been above suspicion but aftergrowths occasionally developed and the bacterial count then exceeded the united states treasury standard. to overcome this difficulty, hypochlorite was used in 1915, but, as was anticipated, it had no effect on the typhoid rate. the high rate in new orleans is largely due to outside cases received for hospital treatment and to other circumstances beyond the control of the water and sewerage department. in all the examples previously cited, the evidence as to the effect of chlorination on typhoid mortality rates is circumstantial but, taken as a whole, it is fairly conclusive. in the examples to be considered next the evidence is more direct. [illustration: diagram xi typhoid in columbus and new orleans] one of the most conclusive experiments as to the beneficial effect of chlorination is that reported by young[8] of chicago. the water supply of chicago was obtained from lake michigan by means of intake pipes and pumped to various parts of the city. the distribution system was divided into four districts and, although there was a certain amount of mixing along the borders, the water supplied to each district was substantially separate. the rapid and progressive decline in the typhoid rate of chicago (from 19 in 1900 to 10.8 in 1911) subsequent to the diversion of the city sewage from the lake, led to the assumption that water-borne typhoid had ceased to be of any moment. early in 1912, however, permission was secured to chlorinate the supply of one district (no. 1) and the treatment was continued until december when the solutions commenced to freeze. diagram xii shows the effect of the treatment on the autumnal increase in district no. 1 as compared with the other three districts. the autumnal increase was calculated from the excess of typhoid incidence for july to november inclusive, over that for february to june inclusive. [illustration: diagram xii autumnal increase in typhoid, chicago (young)] these results demonstrate in a most striking manner the beneficial effect of chlorination. the general conditions, with the exception of the raw water supply, were approximately the same in all four districts. diagram xiii shows that the raw water supply of district no. 1 was slightly worse than any of the others, 21.8 per cent of the samples from district no. 1 containing _b. coli_ in 1 c.cm. as compared with 21.0 per cent in the most polluted supply of the other districts. [illustration: diagram xiii b. coli in chicago raw water (young)] the results obtained at ottawa are also conclusive. following two epidemics of typhoid fever in 1911 and 1912, caused by breaks in the intake pipe, hypochlorite treatment was commenced and has been in continuous operation until february, 1917, when chloramine treatment was substituted. the dosage has been so regulated as to assure a high degree of purity at all times in the water delivered to the mains and as evidence of this it might be mentioned that the average _b. coli_ index (calculated by phelps' method) for the years 1916 and 1917 was only 0.27 per 100 c.cms. the typhoid rates for the five years preceding the epidemic years and for a similar subsequent period are given in diagram xiv. [illustration: diagram xiv typhoid in ottawa] the diagram shows that there has been a constant reduction in the city typhoid rate since the last severe epidemic with the exception of the year 1915. the high rate of that year was caused by a localised epidemic started by polluted well water and spread by flies from an unsewered area. this outbreak was the cause of about seven deaths registered during that year (population 100,000). the objection might be raised that if the reduction of the typhoid rate were due to the water treatment, the decline should have been abrupt and not a gradual one. it is probable that there has been practically no water-borne typhoid in the city since chlorination was commenced but this fact is masked by cases from other sources. during 1911 and 1912 over 3,500 cases of typhoid were reported, of which an appreciable number would become carriers for various periods of time. as these carriers decreased the number of cases infected by them would also decrease and so account for a gradually declining death rate. it might be further objected that the reduced typhoid rate is due to a general improvement in the sanitary conditions. if the death rate from causes other than typhoid can be regarded as a measure of the general sanitary conditions it is obvious from the data in table xxxiii that the improvement in the typhoid rate is immeasurably greater than can be ascribed to that cause. table xxxiii.--death rates in ottawa before and after chlorination --------------------------+-------------------+-------------------- | rate per 100,000 | percentage cause. +---------+---------+-----------+-------- | 1908-12 | 1913-17 | reduction | increase --------------------------+---------+---------+-----------+-------- total[a] | 14.90 | 14.78 | 1.2 | ... typhoid, total | 34[b] | 17 | 50.0 | ... typhoid, city | 26[b] | 8 | 69.2 | ... pneumonia | 100 | 107 | ... | 7.0 tuberculosis | 133 | 138 | ... | 3.7 diarrh[oe]a and enteritis | 139 | 128 | 7.9 | ... under 2 years | | | | --------------------------+---------+---------+-----------+-------- [a] rate per 1,000. [b] 1906-10, epidemic years 1911-12 excluded. one further objection might be made: that the raw water was not infected during 1913-17 or infected to a smaller extent than during the previous period. attempts to isolate _b. typhosus_ from the raw water have invariably been futile but their presence in 1914 might be inferred from the fact that during the latter part of the summer of that year an epidemic of typhoid fever occurred at aylmer, a village that discharges its sewage into the ottawa river about six miles above the ottawa intake. hull, situated on the opposite bank of the river and having a population of 20,000, takes its water supply from the same channel that supplies ottawa but at a point a few hundred feet further down stream. during november and december, 1914, some 200 cases of typhoid fever (incidence 1,000 per 100,000) occurred in hull as compared with 28 in ottawa. as the ottawa intake is situated between the hull intake and the outlet of the aylmer sewer it is incredible that the ottawa raw water was not also infected. in 1916 a liquid chlorine plant was installed in hull, but in 1917, owing to an accident, it was out of commission for a short period and at least 100 cases of fever developed during the following month. during the same period only two cases were reported in ottawa and of these one was obviously contracted outside the city. in view of the preceding facts it must be granted that the improvement in the typhoid rate of ottawa can be definitely attributed to an improvement in the water supply caused by chlorination. the efficacy of chlorination to prevent and check epidemics of water-borne typhoid has never been doubted. innumerable instances could be cited in which the prompt treatment of large public supplies has promptly checked outbreaks that threatened to assume serious proportions and there is no doubt that the extremely low typhoid morbidity rate on the western front of the european battlefield is partially due to the extensive and rigorous chlorination measures that have been instigated. prophylactic vaccination and the prompt isolation of typhoid carriers have largely contributed to the wonderful results obtained but due credit must also be given to the systematic purification and treatment of water supplies. similar results have been obtained at training camps in canada and in other countries by effective treatment with either liquid chlorine or hypochlorite. since the inception of water chlorination in america in 1908, the merit of the method has been very generally recognized throughout the continent but was regarded with scepticism in europe, except as a temporary expedient, until the results obtained by the military forces compelled more general recognition. before the war, chlorination of water supplies in england was only practised in a few isolated and relatively unimportant instances; in 1917, practically the whole supply of london was chlorinated and at worcester a similar treatment has been recommended to enable the slow sand filters to be operated at higher rates without reducing the quality of the water supplied to the consumers. _use and abuse of chlorine._ inasmuch as chlorination has no beneficial effect on water except the reduction of the bacterial content it should be used for this purpose only and under such conditions as permit the operations to be under full control at all times. the supplies that can be most efficiently and safely treated are those that are relatively constant in chemical composition and bacterial pollution. changes in volume can be dealt with by automatic apparatus but sudden changes in organic and bacterial content require a change of dosage that cannot be made by any mechanical appliance. long experience and accurate meteorological records may in some cases enable those in charge of chlorination plants to anticipate changes in the conditions of the water supply, but it is always preferable to provide a positive method of preventing sudden changes by using chlorination merely as an adjunct to other processes of purification. unpurified waters that are objectionable on account of their bacterial content only are very rare, as the cause that produces the bacterial pollution usually produces other conditions that are equally objectionable though not so dangerous to health. sudden storms in summer, or sudden thaws in winter, usually cause large increments in turbidity accompanied by soil washings that often carry appreciable quantities of fæcal matter into surface water supplies. lake supplies often suffer in the same manner and sewage, which during normal conditions is carried safely away from water intakes, obtains access to the supply. if the dosage is maintained at a level sufficiently high to meet these abnormal conditions, complaints as to taste and odour would ensue, and in general, such a practice is impossible. some supplies have been chlorinated successfully for years but the principle of using chlorination as the first and last line of defence cannot be recommended. success can only be obtained by eternal vigilance and the responsibility for results is more than water works officials should be called upon to assume. chlorination is an invaluable adjunct to other forms of water purification and it is not improbable that, in the future, filter plants will be designed to remove æsthetic objections at the lowest possible cost and that chlorination will be relied upon for bacterial reduction. chlorination is the simplest, most economical, and efficient process by which the removal of bacteria can be accomplished and there is no valid reason why it should not be used for that purpose. the popularity of this process has suffered through the efforts of over zealous enthusiasts who have been unable either to recognize its limitations or to appreciate the fact that a domestic water supply should be something more than a palatable liquid that does not contain pathogenic organisms. every system of water purification has its limited sphere of utility and chlorination is no exception to the rule. bibliography [1] weldon and powell. eng. rec., 1910, =61=, 621. [2] clark and de gage, 41st annual rpt. mass. state b. of h. 1910. [3] houston. 12th research rpt. metropolitan water board, london. [4] ellms. eng. rec., 1911, =63=, 388. [5] johnson. eng. rec., 1911, =64=, no. 16. [6] jennings. 8th inter. congr. appl. chem., =26=, 215. [7] longley. j. amer. waterworks assoc., 1915, =2=, 679. [8] young. j. amer. public health assoc., 1914, =4=, 310. appendix estimation of chlorine in chlorinated waters reagents. 1. tolidine solution. one gram of _o_-tolidine, purified by recrystallization from alcohol, is dissolved in 1 litre of 10 per cent hydrochloric acid. 2. copper sulphate solution. dissolve 1.5 grams of copper sulphate and 1 c.cm. of concentrated sulphuric acid in distilled water and dilute the solution to 100 c.cms. 3. potassium bichromate solution. dissolve 0.025 gram of potassium bichromate and 0.1 c.cm. of concentrated sulphuric acid in distilled water and dilute the solution to 100 c.cms. procedure. mix 1 c.cm. of the tolidine reagent with 100 c.cms. of the sample in a nessler tube and allow the solution to stand at least five minutes. small amounts of free chlorine give a yellow and larger amounts an orange colour. for quantitative determination compare the colour with that of standards in similar tubes prepared from the solutions of copper sulphate and potassium bichromate. the amounts of solution for various standards are indicated in the following table: preparation of permanent standards for content of chlorine --------------------+-------------------+---------------------- chlorine. | solution of | solution of | copper sulphate. | potassium bichromate. parts per million. | c.cms. | c.cms. --------------------+-------------------+---------------------- 0.01 | 0.0 | 0.8 .02 | 0.0 | 2.1 .03 | 0.0 | 3.2 .04 | 0.0 | 4.3 .05 | 0.4 | 5.5 .06 | 0.8 | 6.6 .07 | 1.2 | 7.5 .08 | 1.5 | 8.7 .09 | 1.7 | 9.0 .10 | 1.8 | 10.0 .20 | 1.9 | 20.0 .30 | 1.9 | 30.0 .40 | 2.0 | 38.0 .50 | 2.0 | 45.0 --------------------+-------------------+----------------------[illustration: diagram xv] [illustration: diagram xvi] name index a adams, 66, 82 b bassenge, 9 baxter, 4 berge, 9 berthollet, 1 bevan, 29 bonjean, 36 bray, 24 breteau, 26 bucholtz, 5 c catlett, 99 clark, 53, 133 comte, 47 cross, 29 cruikshank, 3 d dakin, 22, 28, 129 darnall, 89 davy, 1 degage, 53, 133 demorveau, 3 dibden, 6 diénert, 48 dienheim-brochoki, 105 dowell, 24 dunbar, 6 dunham, 129 dupré, 5 dusch, 4 e ellms, 34, 83, 84, 133 elmanovitsch, 36 elsner, 6 evans, 84 f faraday, 103 fischer, 16 forcrand, 103 fuller, g. w., 11 g gascard, 47 griffen, 17, 79 h haberkorn, 5 hale, 80, 100 harrington, 34, 65 hauser, 83, 84 hedallen, 17, 79 heise, 36 henry, 2 hermite, 5 hewlett, 9 hooker, 72 horrocks, 48 houston, 8, 59, 71, 133 hsu, 21 j jackson, 91, 99 jakowkin, 26 jennings, 135 johnson, 11, 134 jordan, h. e., 57 k kanthack, 6 kauffman, 9 kellerman, 7 kershaw, 107 kienle, 65, 66, 90, 99 kimberly, 7 klein, 5 koch, 4 kolessnikoff, 16 kranejuhl, 7 kuhn, 5 kurpjuivat, 7 l landolt, 105 langar, 10 laroche, 47 lavoisier, 1, 15 leal, 16 lehmann, 101 leroy, 83 letton, 64 longley, 43, 135 lunge, 105 lyon, 24 m marshall, 102 massy, 48 meadows, 112, 114 mccrady, 130 mcgowan, 8 mclintock, 5 mohler, 31 mohr, 79 moor, 9 muspratt, 126 n nesfield, 8, 89 nissen, 30 norton, 21 novey, 23 noyes, 24 o ornstein, 90 orticoni, 36 p pedler, 103 percy, 3 pettenkofer, 101 phelps, 7, 17, 82 pitcher, 112 plucker, 10 powell, 132 pratt, 7 proskauer, 6, 16 r rabs, 110 race, 36, 110, 116 raschig, 115 rickard, 108 rideal, e. k., 84 rideal, s., 6, 9, 21, 22, 60, 115, 116 roscoe, 5 roozeboom, 103 rouquette, 36 ruffer, 5 s sandman, 56 scheele, 1, 15 schroder, 4 schuder, 10 schumacher, 7 schumburg, 10 schwann, 4 schwartz, 7 semmelweiss, 4 sickenberger, 9 smeeton, 53 smith, 126 t tennant, 2 thomas, 53, 56 thresh, 87 tiernan, 92 tolman, 111 traube, 9 v valeski, 36 von loan, 90 w walden, 132 walker, 87 wallace, 92 wallis, 83 warouzoff, 16 watt, 2, 3, 15, 106 webster, 5, 105 wesbrook, 31, 44, 53 west, 91, 99, 136 whittaker, 31 winkler, 84 winogradoff, 16 winslow, 110 woodhead, 7 woolf, 5 y young, 138 z zirn, 6 subject index a absorption of chlorine by water, 35 abuse of chlorination, 144 acids, effect of, 19, 21 action of chlorine, 16 admixture, effect of, 39 aftergrowths, 55 accelerated growth, 58 _b. coli_ in, 57 effect of liquid chlorine, 99 views as to nature of, 56 algæ, effect of chlorine on, 133 alkalies, effect of, 19, 20 allen-moore cell, 111 ammonia, and chlorine, 24 and sodium hypochlorite, 114 effect on bleach, 21 effect on oxidising action, 21 soda process, 2 antichlors, 86 antiseptics, early work on, 3 chlorine as an, 50 application of chlorine, point of, 43 auto-suggestion, 62 b _b. choleræ_ suis, 31 _b. cloacæ_, 31 _b. coli_, aftergrowths, 57 in sewage, 6, 7 in water, 9, 28, 31 standard, 46 viability of, 52, 55 _b. cuticularis_, 53 _b. fæcalis alkaligenes_, 31 _b. enteritidis_, 31 _b. enteritidis sporogenes_, 53 _b. lactis ærogenes_, 31 _b. subtilis_, 53 _b. tetani_, 9 _b. typhosus_, 9, 10, 30, 31 bacteria surviving chlorination, 50 aftergrowths, 55 nature of, 53 spores, 57 benzidine, 83 bleach, analysis of solution, 79 as deodourant, 3, 6 as sewage disinfectant, 6, 7 at adrian, 11 at boonton, 11, 16 at bubbly creek, 11 composition, 14 decomposition of, 25 discovery, 2 germicidal velocity, 20, 21 hydrolysis, 18, 19 production, 3 stability of, 17 toxic action, 22 treatment, 72 control of, 78 cost, 86 dosage regulation, 75 in france, 78 losses in, 81 mixing tank, 73 plant design, 72 storage tank, 75 brest experiments, 5 c carnallite, 1 chicago, typhoid rate, 138 chloramine, 114 at denver, 124, 126 at ottawa, 28, 116 contact period, 123 cost of, 124 decomposition of, 126 experimental results, 119 germicidal power, 116 operation of process, 126 plant design, 120 preparation of, 115 ratio of chlorine and ammonia, 116, 122 tastes and odours, 28, 64, 117 toxic action, 22, 29 chlorides, effect of, 20 chlorine, and ammonia, 24, 25 discovery of, 1 disinfection, effect of pabulum, 4 general reactions, 28 hydrate, 103 detection of, 81 effect on flowers, 68 estimation of, 81 in sanitary work, 4 medicinal dose, 67 oxygen equivalent, 23 liquid, 89 advantages of, 97 cost of treatment, 101 disadvantages of, 101 germicidal efficiency, 99 machines, 89 peroxide, 9 water, 102 corrosion of pipes, 69 damage to seeds, 68 decomposition of, 15 heat of formation, 27 chlorometer, 84 chloros, 8 chlorozone, 105 colour, effect on dosage, 33 columbus, typhoid rates, 137 complaints, 62 contact period, effect on dosage, 44 effect on taste, 43 usual practice, 45 cost of bleach plant, 85 bleach treatment, 86 liquid chlorine treatment, 101 crossness experiments, 5 d dayton cell, 107 dechlor filters, 87 denver, chloramine treatment, 124, 126 dichloramine, 128 disinfectants, 50 disinfection, early views of, 3 dosage, 30 determination of, 46 effect of, admixture, 39 colour, 33 contact period, 43 initial contamination, 32 light, 45 oxidisable matter, 32 standard of purity, 30, 32 temperature, 34, 36 turbidity, 45 for military work, 48 regulation of bleach, 75 relation to oxygen absorbed, 36 tanks, 75 e eau de javelle, 3, 47 electrical conductivity of treated water, 70 electrolysed sea water, 5 electrolytic hypochlorite, 2, 104 bradford, 5 brest, 5 brewster, 6, 105 cost of, 113 electrolytic hydrochlorite, crossness, 5 discovery of, 3 diaphragm cells, 110 early use of, 5 efficiency of, 109 havre, 5 non-diaphragm cells, 106 electrozone, brewster, 6 maidenhead, 6 tonetta creek, 6 f filter effluents, chlorination of, 34 filters, effect on beds, 60 effect on runs, 132 fish, effect on, 8, 67, 68 g germicidal velocity, effect of acids, 21 alkalies, 20 ammonia, 21 chlorides, 20 guildford, chlorination at, 9 h haas and oettel cell, 108 halazone, 128 hardness, effect of chlorine on, 132 havre experiments, 5 hermite fluid, 5 hexamethyl-_p_-aminotriphenylmethane, 83 historical, 1 hooghly river, 7 hydrazine, 126 hydrogen peroxide, 24 hydrolysis of hypochlorites, effect of, acids, 19 alkalies, 19 chlorides, 20 hygienic results, 134 hypochlorous acid, 17 decomposition of, 24, 25, 26 hydrolytic constant, 18 i initial contamination, effect on dosage, 32 intestinal organisms, viability of, 52 iodoform taste, 65 iron salts, effect on dosage, 33 j jersey city, court case, 11, 16 k kellner cell, 108 l labarraque solution, 105 leavitt-jackson machine, 91 leblanc process, 2 light, effect on dosage, 45 lincoln, chlorination at, 8, 59 liquid chlorine, advantages of, 97 and tastes, 65 effect of temperature on, 95 machines, 89 dry feed, 94 e. b. g. co., 91 leavitt-jackson, 91 operation of, 95 wallace and tiernan, 92 l'orient, experiments at, 5 m m. agilis, 53 maidstone, use of bleach at, 8 margin of safety for taste and odour, 64 material for bleach plants, 74 military work, bleach method for, 78 chlorine water, 103 dosage for, 47, 48, 78 early european, 10 liquid chlorine, 102 typhoid reduction, 143 use of chlorine in, 8 mixing tank for bleach, 73 moisture, effect on chlorine gas, 16 montreal, dosage at, 34 electrolytic cells, 112 n nascent oxygen hypothesis, 17 nelson cell, 111 neva river, 36 new orleans, typhoid rates, 137 new york, bacteria surviving treatment, 53 bleach efficiency, 100 liquid chlorine plant, 97 nitrites, effect on dosage, 33 nitrogen trichloride, 24, 128 o odours, effect of contact period on, 43 nature of, 63 ottawa, aftergrowths at, 57 bleach plant efficiency, 100 chloramine plant, 120 chloramine results, 121 sludge trouble, 65 typhoid rates, 140 oxidisable matter, effect on dosage, 32, 36 oxychloride, guildford, 9 middlekerke, 9 ostend, 9 ozone, 24 p philadelphia and chlorination, 136 pipe corrosion, 69 pittsburg report, 71 plumbo solvency, 71 _p. mirabilis_, 31 potassium permanganate, 23 puerperal fever in vienna, 4 pumps, for admixture, 41 r red bank, sewage disinfection at, 7 reversed ratio of counts, 54 s sewage disinfection at baltimore, berlin, 7 boston, 7 brewster, 6 hamburg, 6 maidenhead, 6 sludge, as cause of complaints, 65 sodium bisulphite, 86 sodium chloride, deposits, 1 decomposition of, 106 sodium hypochlorite, 105 decomposition of, 26 effect of ammonia on, 21 hydrolysis of, 26 sodium thiosulphate, 87 standard of purity, 30 storage tanks, 75 sulphuretted hydrogen, 33 sylvine, 1 t tannin, 67 tastes, effect of contact period on nature of, 63 temperature, effect on absorption of chlorine, 35, 38 bleach deterioration, 72 dosage, 34, 36 germicidal velocity, 38 pressure of liquid chlorine, 96 tastes and odours, 66 thermophylic organisms, 54 tolidine, 82 toxic action of chlorine, 22, 29 turbidity, effect on dosage, 45 effect of chlorine on, 132 u use of chlorination, 144 w water mains, disinfection of, 8 well water, 7 worcester, chlorination at, 11 worthing experiments, 5 subjects related to this volume for convenience a list of the wiley special subject catalogues, envelope size, has been printed. these are arranged in groups--each catalogue having a key symbol. (see special subject list below.) to obtain any of these catalogues, send a postal using the key symbols of the catalogues desired. _list of wiley special subject catalogues_ =1--agriculture. animal husbandry. dairying. industrial canning and preserving.= =2--architecture. building. masonry.= =3--business administration and management. law. industrial processes:= canning and preserving; oil and gas production; paint; printing; sugar manufacture; textile. chemistry =4a= general; analytical, qualitative and quantitative; inorganic; organic. =4b= electroand physical; food and water; industrial; medical and pharmaceutical; sugar. civil engineering =5a= unclassified and structural engineering. =5b= materials and mechanics of construction, including: cement and concrete; excavation and earthwork; foundations; masonry. =5c= railroads; surveying. =5d= dams; hydraulic engineering; pumping and hydraulics; irrigation engineering; river and harbor engineering; water supply. (over) =5e= highways; municipal engineering; sanitary engineering; water supply. forestry. horticulture, botany and landscape gardening. =6=--design. decoration. drawing: general; descriptive geometry; kinematics; mechanical. electrical engineering--physics =7=--general and unclassified; batteries; central station practice; distribution and transmission; dynamo-electro machinery; electro-chemistry and metallurgy; measuring instruments and miscellaneous apparatus. =8=--astronomy. meteorology. explosives. marine and naval engineering. military. miscellaneous books. mathematics =9=--general; algebra; analytic and plane geometry; calculus; trigonometry; vector analysis. mechanical engineering =10a= general and unclassified; foundry practice; shop practice. =10b= gas power and internal combustion engines; heating and ventilation; refrigeration. =10c= machine design and mechanism; power transmission; steam power and power plants; thermodynamics and heat power. =11=--mechanics. =12=--medicine. pharmacy. medical and pharmaceutical chemistry. sanitary science and engineering. bacteriology and biology. mining engineering =13=--general; assaying; excavation, earthwork, tunneling, etc.; explosives; geology; metallurgy; mineralogy; prospecting; ventilation. +---------------------------------------------------------------------+ | additional transcriber's notes: | | | | * the original symbol in table xiv (a circled +) has been changed | | to [¤]. | | * some formulas have been spaced out for better readability. | | * some minor typographical errors have been corrected (including | | indicators for references and missing diacritical marks from | | german words). | | * in-line multi-line formulas have been changed to in-line single | | line formulas, if necessary with the addition of brackets. | | * inconsistencies in spelling, hyphenation, lay-out or formatting | | have not been corrected, except in the following cases: | | * bassenege, schemmelweiss, langar and kanthdack in the name index| | have been changed to bassenge, semmelweiss, langer and kanthack | | as in the text. | | * heisse, jordon, tonnetta creek and horrock's have been changed | | to heise, jordan, tonetta creek and horrocks's, respectively, as| | elsewhere in the text. | | * page 35: n^{1} and n^{2} in formula changed to n_{1} and n_{2} | | as elsewhere. | | * page 7: hadallen changed to hedallen as elsewhere in the text. | | * changes made to the text: | | * page 17: --> changed to <=> in chemical formula as described in | | the text. | | * page 26: h^{.} + hco_{3} changed to h^{.} + hco_{3}'. | | * page 26: chlor-ions changed to chlorine ions. | | * page 54: gention violet changed to gentian violet. | | * page 103: footnote marker [11] inserted (missing in original). | | * the author called kurpjuivut, kurjuivut and kurpjuivat in various | | places in the text is probably called kurpjuweit. the author | | called schumburg and schumberg in the text is called schumberg. | | the book contains references to both zaleski and elmanovitsch | | and valeski and elmanovitsch; zaleksi is probably correct. | | * other remarks: | | * footnote on page 119: fraction unclear in the original, | | presented here as 5-1/2. | | * page 134: affluents should probably be effluents. | | * in the original work, there is no table xxii between table xxi | | and xxiii. | +---------------------------------------------------------------------+ * * * * * transcriber's note: words in italics are indicated like _this_. subscripts are indicated like this: h_{2}o. the original publication has been replicated faithfully except as listed at the end of the text. * * * * * table of contents introductory. 475 the concession. 476 geology and topography. 476 population, area, and mortality. 479 rainfall and temperature. 480 available sources of supply. 484 materials for concrete. 491 estanzuela supply. 494 south distributing reservoir. 506 san geronimo gravity supply. 514 distributing reservoir at obispado. 525 comparison of south and obispado reservoirs. 530 analyses of estanzuela and san geronimo waters. 532 city water distribution system. 532 main sewerage system. 539 main outfall sewer. 542 sewage disposal works and irrigation lands. 545 quality of and rates for labor. 552 cost of works. 552 tariffs and sanitary regulations. 553 engineers, etc. 556 discussion. 557 james d. schuyler. 557 david t. pitkethly. 559 v. saucedo. 563 george t. hammond. 567 rudolf meyer. 576 george robert graham conway. 580 american society of civil engineers instituted 1852 transactions paper no. 1193 the water-works and sewerage of monterrey, n. l., mexico.[1] by george robert graham conway, m. am. soc. c. e. with discussion by messrs. james d. schuyler, david t. pitkethly, george s. binckley, vicente saucedo, george t. hammond, rudolf meyer, and george robert graham conway. introductory. [1] presented at the meeting of february 1st, 1911. monterrey, the capital of the state of nuevo león, mexico, is built on the site of the old village of santa lucía de león, which was established in 1583 by the governor of the kingdom of león, don luis carabajal. four years later carabajal was imprisoned by the inquisition, and the village of santa lucía was abandoned by its few inhabitants. in 1596, captain diego montemayor, a resident of saltillo, in the adjoining state, wishing to render a service to his king, philip ii of spain, assembled his friends, and on september 20th of that year, proceeded to establish a town on the site of the old village on the northern side of the principal spring at the place. the town was named "nuestra señora de monterrey" (our lady of monterrey), after the count of monterrey (ojos de santa lucía y valle de extremadura), the ruling governor of new spain, as mexico was then called. monterrey is approximately in the center of the state of nuevo león, 1° 12´ west of mexico city, and in latitude 26° 40´ n. it is a distributing railway center on the main line of the national railroad, 270 km. from the rio grande at laredo, 1,022 km. from mexico, and 520 km. from tampico by the mexican central railway. it is the center of many large industries, and is the second largest manufacturing city in the republic. the concession. the works described in this paper were carried out under a guaranteed concession granted by his excellency, general bernardo reyes, governor of the state of nuevo león, to messrs. james d. stocker and william walker, of scranton, pa. the concession is dated october 19th, 1904, and is for 99 years from that date; the works for a complete water and drainage system were to be finished in 3 years from the time of their commencement. before the works were designed and begun, the concession was acquired by mr. william mackenzie, of the firm of mackenzie, mann and company, limited, of toronto, ont., canada, who, on may 4th, 1906, organized the monterrey water-works and sewerage company, limited (compañía de servicio de agua y drenaje de monterrey, s. a.), under the laws of the dominion of canada, of which company he is president. mr. mackenzie is also president of the monterrey railway, light, and power company, limited, which was constructing the street railways of monterrey concurrently with the water-works. under the provisions of the concession, the government appointed a financial interventor, who had authority to examine and check the company's expenditures, and also a technical inspector to examine and report on the construction. the duties of these officials also apply to the operation of the system when the construction is finished. the government has the right, after the system has been operated 40 years, to purchase the entire property, subject to 6 months' notice, for a sum equal to 16-2/3 times the average annual net proceeds during the 3 preceding years. this right may be exercised at the end of 40 years, or at the end of any 10-year period thereafter, up to 99 years from the commencement of operations. geology and topography. monterrey lies in a plain at the foot of the eastern sierra madre mountains which constitute the eastern margin of the mexican cordilleran plateau, and is surrounded by the magnificent mountains of that group, among the most notable of which are the beautiful mitra and silla mountains. in the neighborhood of monterrey these mountains attain heights of from 2,000 to 2,400 m., and are noted for their broken and jagged sky-lines. the leading geological characteristics of the district are the uplifted limestones of the older cretaceous age which form the main mass of the mountains. primarily, the mountains are compressional folds which, in the sierra madre, near monterrey, are close and vertically compressed.[2] the drainage areas of the santa catarina river, which flows through monterrey, and of the estanzuela and silla rivers, its tributaries, are of limestone and shale; originally the shales were above the limestone, but the convulsion which formed the sierra madre as an anticlinal fold, left the originally horizontal strata standing nearly upright, and subsequent erosion in the upper part of the anticline has exposed nearly vertical strata in many places. the limestone being hard and resisting erosion, there is generally, along the line of contact, an abrupt drop vertically on the face of the limestone to the shale below. in many places this abrupt drop is broken by a limestone talus, but the line of contact can generally be traced. mining operations in these mountains have revealed the presence of large caves at a considerable elevation, many of which contain large reservoirs of water, delivered to them through numerous faults. the river valleys are formed of masses of limestone conglomerate and coarse gravels, re-cemented in many cases by the lime deposits of the flowing waters. one of the chief characteristics of the subsoil of monterrey itself is a local rock called "sillar," which is a superficial deposit of carbonate of lime from the evaporated waters. in some places the "sillar" is largely mixed with a conglomerate called "tepetate," or "impure sillar." [2] _transactions_, am. inst. min. engrs., vol. xxxii (1902), pp. 163-178. [illustration: plate ii.--general plan of the water supply and drainage works for monterrey, n. l., mexico.] topographically, the region around monterrey is distinguished by the drainage area of the river santa catarina, which rises in the sierra madre near the laguna de sanchez, at an elevation of 1,850 m., as shown on plate ii. from this laguna it follows a tortuous course between precipitous mountains through the boca of santa catarina to monterrey, for a distance of 90 km., eventually finding its way to the san juan river, a tributary of the rio grande. throughout its course it disappears, flows underground, and again appears; and, except in flood time, it has a subsurface flow for a distance of 16 km. above the city. in the cañon of santa catarina it appears at the surface, having a normal flow of about 1,415 liters (50 cu. ft.) per sec., and its waters at that point are divided into two parts and carried into irrigation canals. the drainage area of the river above monterrey is 1,410 sq. km., and its bed at monterrey is between 518 and 545 m. above sea level. southward from monterrey the country rises along the valley of the silla for a distance of 19 km., where the silla is separated from the san juan by a low divide, the former flowing northward to monterrey and the latter southeastward toward allende. the silla valley is bounded on the east and west by the steep ranges of the silla and sierra madre mountains. the floor of this valley is gently rolling, but is cut by many arroyos which carry little or no water during the greater part of the year. the chief feeder of the silla river is the estanzuela, a stream which derives its waters from several springs coming to the surface near the line of contact between the limestone and the shale, at elevations of about 800 and 900 m.[3] above datum. the water-shed of this stream is rich with abundant vegetation due to the precipitation being greater than on the santa catarina water-shed. to the south of the divide the country is well wooded, and el porvenir, 35 km. from monterrey, is the garden spot of the state of nuevo león. here the rainfall is much greater than at any other point near monterrey, and there are many streams which are used for irrigation purposes. monterrey is built on a plain, chiefly on the north side of the santa catarina river. this plain has a general fall toward the northeast, and beyond the city it slopes gently northward for several miles toward the topo grande river, and then southeastward to join the great coastal plain of the gulf of mexico. the general elevation of the city lies between the 519and 550-m. contours. the plaza zaragoza, in the center of the city, is 533.90 m. above sea level; the elevation of the highest part of the city, at the western boundary, is 550.05 m., and of the lowest part, at the northeastern boundary, 518.0 m. above sea level. [3] throughout this paper datum refers to the height in meters above the mean sea level of the gulf of mexico at the port of tampico. [illustration: plate iii, fig. 1.--general view of line, estanzuela aqueduct.] population, area, and mortality. the population of monterrey has increased as follows: census of 1851 14,621 " " 1861 26,000 " " 1871 33,811 " " 1881 39,456 " " 1891 41,154 " " 1901 73,508 (estimated) 1909 86,000 to 90,000 the greatest progress, it will be noted, was between 1891-1901, with an increase of more than 22,000 in 10 years. in designing the new works, provision has been made for the future requirements of a city of 200,000 persons. the actual area within the city limits proper is 960.5 hectares (2,374 acres), forming the area to be provided with water and drainage, but the municipal district extends to many surrounding suburbs, and covers an area of 33,758 hectares (83,426 acres). table 1.--population and death rate of monterrey, n. l., mexico, from 1901 to 1909, inclusive. ============+========+=========+========+=========================| | | | |deaths from typhoid fever| | popu | deaths | rate +----+----+----+----+-----+ year. |lation. |from all | per | | | | | | | | causes. | 1,000. |jan.|feb.|mar.|apr.|may. | | | | | | | | | | ------------+--------+---------+--------+----+----+----+----+-----+ census 1901 | 73,508 | 2,965 | 40.3 | 0 | 2 | 1 | 3 | 4 | estim. 1902 | 74,500 | 3,338 | 44.8 | 1 | 4 | 2 | 3 | 6 | " 1903 | 76,000 | 3,825 | 50.3 | 3 | 2 | 4 | 1 | 0 | " 1904 | 77,500 | 2,905 | 37.4 | 0 | 1 | 1 | 5 | 3 | " 1905 | 79,000 | 2,951 | 37.4 | 2 | 0 | 0 | 3 | 3 | " 1906 | 80,000 | 2,935 | 36.7 | 1 | 2 | 1 | 3 | 3 | " 1907 | 82,500 | 3,269 | 39.6 | 4 | 6 | 3 | 3 | 5 | " 1908 | 84,000 | 3,188 | 37.9 | 5 | 2 | 5 | 3 | 8 | " 1909 | 86,000 |[4]3,477 | 40.4 | 5 | 1 | 4 | 5 | 13 | ============+========+=========+========+====+====+====+====+=====+ ============+=========================================+==============+ | deaths from typhoid fever. (continued) | deaths from | |----+----+----+----+----+----+----+------+ typhoid fever| year. | | | | | | | |total | per year per | |jne.|jly.|aug.|sep.|oct.|nov.|dec.|for | 100,000 | | | | | | | | |year. | population. | ------------+----+----+----+----+----+----+----+------+--------------+ census 1901 | 3 | 6 | 6 | 3 | 6 | 4 | 2 | 40 | 54 | estim. 1902 | 5 | 3 | 1 | 1 | 2 | 3 | 5 | 36 | 48 | " 1903 | 5 | 3 | 5 | 6 | 16 | 3 | 1 | 49 | 64 | " 1904 | 3 | 3 | 4 | 1 | 5 | 1 | 0 | 27 | 35 | " 1905 | 7 | 6 | 3 | 2 | 7 | 2 | 2 | 37 | 47 | " 1906 | 6 | 5 | 3 | 2 | 1 | 2 | 3 | 32 | 40 | " 1907 | 6 | 4 | 4 | 9 | 3 | 0 | 3 | 50 | 61 | " 1908 | 5 | 9 | 7 | 2 | 7 | 4 | 0 | 57 | 68 | " 1909 | 11 | 15 | 12 | 6 | 8 | 3 | 4 | 87 | 101 | ============+====+====+====+====+====+====+====+======+==============+ [4] excluding deaths due to drowning in the great flood of august 27th and 28th. table 1 gives particulars of the death rate for 1901 to 1909, inclusive, and data relative to the mortality due to typhoid fever. the high death rate is caused by the excessive infantile mortality, which is so prevalent throughout the whole of mexico. the climatic condition of monterrey, with its exceptionally healthy subsoil, ought to make it one of the healthiest of cities, if proper care were taken to enforce sanitary laws. the data regarding typhoid mortality are probably understated, as they were compiled by the writer, in the absence of any official publications, from the actual death certificates, but no special care is taken by the authorities to insure accuracy in such certificates. attention is called to the typhoid rate in may, june, july, and august, 1909; this high rate coincides with a scarcity of rainfall and the greatest period of drought experienced in 30 years, and immediately precedes the great flood of august 27th. it was probably due to the lowering of the ground-water throughout the city and the consequent contamination of the private wells, which were largely in use during that time. throughout the city the wells are sunk to a depth of about 12 or 15 m., in order to reach the subterranean waters, and the cesspools are often in dangerous proximity to them and at a much higher level. the nature of the subsoil, which is often much fissured and open in the conglomerate and sillar strata, would make the passage of contamination an easy matter, and this alone would account for a high mortality due to water-borne diseases. rainfall and temperature. the precipitation records of monterrey and its neighborhood are very meager, and cannot be relied on for a longer period than from 1894 to 1909, inclusive. the records are available from 1886, but in the early years there are many apparent discrepancies, and they are probably inaccurate. the average rainfall for the 15 years (1894-1908) is 21.94 in.; the driest years for this period are as follows: 1894, 14.14 in.; 1902, 15.29 in.; 1907, 15.23 in.; 1908, 15.11 in. assuming the early records to be correct, the average rainfall for the period, 1886-1908, would be 19.86 in. at saltillo, which is 50 miles due southwest, at an elevation of about 1,520 m. above sea level, the average rainfall for the 23 years, 1884-1908, inclusive, is given as 21 in. the maximum year was 1889, with 33-1/2 in., and the minimum 1903, with 7-1/2 in. at carmen, in the state of tamaulipas, 144 km. southwest of monterrey, at an elevation of about 310 m. above sea level, the average fall for 12 years is 24.70 in., the maximum year being 1897, with a fall of 34.09 in., and the minimum year, 1905, with 13.41 in. [illustration: fig. 1.--annual rainfall in monterrey covering the period from 1894 to 1909.] fig. 1 shows the annual variation of rainfall at monterrey for 1894-1909. fig. 2 shows the monthly variation during the same period, and gives the minimum, average, and maximum for each month. from these diagrams it will be seen that the months of least rainfall are december, january, february, and march, with averages of 0.66, 0.59, 0.79, and 0.93 in., respectively. the months of greatest rainfall are august, with an average of 4.39 in., and september with 4.87 in. the maximum in any month prior to 1909 was 16.75 in., during september, 1904. _rainfall in 1909._--the rainfall in 1909 was unprecedented, causing the disastrous flood in the santa catarina river, which will be referred to when describing the works. fig. 3 shows the monthly rainfall for 1906 to 1909, inclusive, and has been plotted to show the variation of rainfall prior to the great precipitation of august, 1909. in that month there were two heavy falls, one beginning at midnight on august 9th, and during the following 42 hours a fall of 13.28 in. was recorded by the gauge at the water-works company's general offices, 10.20 in. of which fell, during the first 24 hours. from 6 p. m. to 11 p. m., on august 10th, 5.019 in. were recorded, or an average of 1 in. per hour. [illustration: fig. 2.--monthly rainfall in monterrey covering the period from 1894 to 1909 inclusive.] [illustration: fig. 3.--monthly variation of rainfall at monterrey 1906-1907-1908-1909.] after 13 dry days, another rainstorm began, at 4 p. m., on august 25th, and continued more or less intermittently until august 29th. during this 98-hour period there was an additional fall of 21.61 in., 11.27 in. falling in 24 hours. the total precipitation during the month amounted to 36.00 in. the highest previous record for the month of august was in 1895, with a fall of 6.61 in. fig. 4 gives the details of the two heavy precipitations in august. as no automatic recording gauge was available, the maximum intensity could only be computed approximately, owing to the intermittent character of the readings taken from the ordinary rain gauge on the roof of the water-works company's office in the city. from the readings thus obtained, it was shown that the maximum intensity occurred early on the morning of the 28th, and was nearly 2 in. per hour. above monterrey, in the santa catarina water-shed, it is believed that the precipitation was considerably greater, but no gauges were accessible during the month. [illustration: fig. 4.--curve of rainfall at monterrey during august 10th & 11th and from august 25th to 29th 1909.] the total rainfall for 1909 amounted to 47.46 in., of which 75% fell in august. this is 50% greater than the previous highest annual record (31.65 in. in 1900) for monterrey. _temperature._--fig. 6 gives a record of the temperature at monterrey from 1901 to 1909, inclusive. these records were taken at an altitude of 520 m. it will be noted that the lowest recorded temperatures are in january and february. the lowest during these years was 24° fahr., in january, 1905. the monthly maxima vary between 80 and 110° fahr. the mean annual temperature is 72.65° fahr. (the mean annual barometer is 28.2 in.) [illustration: fig. 6.--diagram of temperature variation at monterrey, 1901-09.] available sources of supply. the question of the best sources from which monterrey should be supplied with potable water was one that had been long under discussion, and was the subject of many investigations prior to the granting of the present concession. several of the original schemes called for an impounding reservoir in the cañon of santa catarina and it was on the assumption that a dam would be built that a clause was inserted in the concession for the purpose of making its construction obligatory. the general character of the physical and geological conditions surrounding monterrey has already been referred to. a thorough study of these conditions proved that no suitable site for impounding the santa catarina river could be found, apart from the fact that periodically this river is subject to enormous floods which tear through the steep cañon with tremendous velocity. at the site originally proposed for the dam, a considerable underflow was found, and later investigations, carried out under the present concession, proved that, although borings were carried to a depth of 54 m., bed-rock could not be found, the strata being composed of gravels, conglomerate and sand. assuming that such a dam could have been built, the quality of the water draining from a comparatively barren water-shed, on which many thousands of goats are pastured, would have made its filtration an absolute necessity before it could be delivered to the consumers. the various available sources from which water could be delivered to the city by gravity were investigated by mr. f. s. hyde, in the autumn of 1905, and also by j. d. schuyler, m. am. soc. c. e., who was afterward retained as consulting engineer for the company. the various investigations made from time to time showed that the question of a satisfactory supply was one of extreme difficulty, requiring prolonged observation and study, more particularly into the character of the underground sources of supply. one of the chief characteristics of many of the streams in the state of nuevo león, is their disappearance and reappearance at different points along their routes, and the santa catarina river, under normal conditions, as already remarked, is a very notable example of a river which is very dry at the surface for many kilometers of its length. in the writer's opinion, the waters of this and similar rivers in the state pass through many open caverns underground, so that experience gained in the investigation of underflow waters in other places would be insufficient to determine the quantity passing at any point along the river if ascertained by merely computing it from the velocity of the underflow and the area of the water-bearing gravels. the rainfall on the water-shed of the santa catarina river is probably 25% greater than at monterrey, and all ordinary rains sink rapidly into the limestone soils and quickly disappear. in another water-shed of a very similar character, namely, that of the rio blanco, in the southern part of the state, the underflow waters appear at the surface at a place called mezquital, where a metamorphosed sandstone barrier prevents them from disappearing underground. at this point the normal quantity of water is about 5,660 liters (200 cu. ft.) per sec., but it gradually disappears, and a few kilometers below it has sunk to an insignificant stream, finally disappearing altogether for about 20 km. in the neighborhood of monterrey similar conditions exist with regard to the surface-water supplies, and investigations, therefore, were directed toward obtaining unpolluted supplies from springs and underground sources. _santa catarina sources._--the chief points from which it was thought desirable to obtain underflow supplies were (1) at the barrier of san geronimo, and (2) at the cañon of santa catarina, both shown on plate ii. conditions at san geronimo, which is only 6-1/2 km. west of monterrey, were investigated by the state government in 1892, to determine the depth of bed-rock, the rock on either side of the valley being shale, with its original bedding planes standing almost vertical. to determine this depth, borings were made by driving 2-in. tubes until it was assumed that bed-rock had been reached, a method which, in strata containing so many boulders, was obviously unreliable. these borings indicated that bed-rock was from 12 to 15 m. below the surface. if these had proved to be correct, there is no doubt that a development of the underground water at this point, by constructing a submerged dam combined with an infiltration gallery, would have yielded a large supply. in march, 1906, the company commenced operations at san geronimo by sinking a well a few meters north of the then dry bed of the river. water was found in considerable quantities a few meters below the surface, practically at the level of the river, that is, 570 m. above datum. this supply was used for provisional purposes, and will be referred to later in describing the san geronimo gravity supply works. between august, 1906, and january, 1907, 4-in. bore-holes were sunk in the river bed and on the high ground to the north with a "keystone" driller outfit. these borings showed bed-rock immediately under the river bed, at a depth of from 15 to 45 m., but dipping gradually as the borings were carried northward. boring operations were also carried on at santa catarina, during november and december, 1906, and in january, 1907, to determine the geological conditions, and the results are shown on fig. 7. from the area of water-bearing gravels found, it was proposed to tap the underflow water at the 630-m. level by an infiltration gallery. this would have necessitated a gravitation tunnel 3,000 m. long, and an aqueduct of 14 km., which it was proposed to carry to one of two distributing reservoirs at guadalupe, on the south side of the river, opposite monterrey. in may, 1907, the writer, after making a study of all the available data which had been accumulated, had additional borings sunk farther across the valley to the north, and these revealed a considerable area of water-bearing gravels, and proved that, in former geological times, the santa catarina flowed about 500 m. north of its present position, and to the back of obispado mountain, instead of through the city. this aspect of the subject was discussed with mr. schuyler, who agreed with the writer that, in the interest of economy, it was better to tap this supply by an infiltration gallery at the 560-m. level, and bring the water thus obtained to a reservoir to be placed at the western limits of the city, dividing the city, for distribution purposes, into two interchangeable systems, a highand a low-pressure, the high-pressure system being supplied from estanzuela, 18 km. south of the city. one advantage to be gained from this change was that the scheme was capable of considerable extension, and any future developments at santa catarina cañon would form part of the works to be constructed for both highand low-pressure districts. [illustration: fig. 7.--cross-section of santa catarina river at santa catarina.] the future extension of the santa catarina sources, the writer believes, can be developed best by driving an infiltration gallery 10 m. below the surface of the santa catarina river, a little west of the village of the same name, and then conveying the water through a comparatively short gravitation tunnel and pressure conduit to a main reservoir near san geronimo having a top water level at an elevation of about 590 m. above datum. _southern sources of supply._--the available sources of supply southward from monterrey include a number of springs at various points in a distance of 40 km. many of these springs are of uncertain quantity, and some are quite dry during periods of drought. the chief perennial springs near monterrey are those which contribute to form the estanzuela and diente rivers, both tributaries of the silla, while farther south, at the potrero cerna, near el porvenir, there are excellent springs, at a considerable elevation, with a minimum flow of from 170 to 200 liters (from 6 to 7 cu. ft.) per sec. the total quantity of water available from all these springs during the driest season would probably not be less than about 560 or 700 liters (from 20 to 25 cu. ft.) per sec. the estanzuela springs issue at the foot of the sierra madre mountains, and have a normal flow of from 56 to 85 liters (2 to 3 cu. ft.) per sec. in an ordinary dry year; they probably derive their water, through the limestone formation, from the neighboring water-shed of santa catarina, as the catchment area of the stream is only 910 hectares, and the stream has never been known to fail, even in the driest periods of prolonged drought. the rainfall on the area is about 30 in. per annum, and the catchment area is well wooded and covered with abundant vegetation. the el diente springs have an ordinary dry-weather flow of about 28-1/2 liters (1 cu. ft.) per sec.; but part of the water is carried underground, and the real quantity is much greater and could be developed by a small submerged dam carried down to bed-rock. the elevation and the extreme purity of the water of the estanzuela river made its acquisition very desirable, and the company, therefore, purchased the federal water rights owned by various members of the estanzuela community, amounting to 91 liters per sec., and has since acquired a federal concession to all the flood-waters of that river. it was decided, therefore, to adopt the estanzuela river as the first step toward developing the water to the south of monterrey for a high-pressure supply, the advantage of the scheme being that from time to time extensions could be made to tap other sources by gravity, as the demands of the city required. the estanzuela scheme, therefore, is a preliminary step toward future extensions which will be necessary in this direction as the city grows. the springs near el porvenir, and others which contribute to the san juan river, can be tapped at a sufficiently high level to convey them by a gravity pressure line to the estanzuela aqueduct near mederos. the two sources definitely decided on in july, 1907, were those from estanzuela and san geronimo. the works were designed to supply 40,000,000 liters daily, which it was assumed would be sufficient for all future developments for a population of 200,000 at a per capita consumption of 200 liters per day. the present requirements of the city's population, assuming that all the water was supplied by the company, would be, at that rate, which is a very liberal one, only 18,000,000 liters daily. this, it was thought, would be easily met by the san geronimo source alone, as it was estimated that it would provide not less than 20,000,000 liters, if the infiltration gallery was driven far enough into the water-bearing gravels. the question of a high-pressure water supply for domestic use in a city like monterrey is not a serious one, as practically nine-tenths of the houses are of one story. the increase in the number of large commercial buildings, however, will make the demand greater in the future, and this point has been kept in mind in arranging the division of the distribution systems. materials for concrete. _cement._--in the early stages of construction the cement for the work was obtained from the associated portland cement manufacturers, limited, of london, which supplied the "pyramid" brand, from the knight, bevan, and sturges works, but later the supply was obtained from a new factory at hidalgo, near monterrey. the total quantity of portland cement used was 42,500 bbl. of "pyramid" and 32,500 bbl. of "hidalgo." the english cement was tested for the water-works company in london before shipment and again at monterrey, to conform to the british standard specifications; the "hidalgo" cement was required to pass the standard specifications advocated by the special committee of the american society of civil engineers. the quality in each case was of the very highest, no difficulties being experienced at any time. _sand and rock._--one of the chief difficulties in connection with the construction work in its initial stages was in procuring satisfactory sand for the concrete. an investigation of the quality of all the available sands in the neighborhood of monterrey resulted in the decision to use a manufactured sand obtained from the calcareous shales in the foot-hills opposite the city, on the south side, and near the site of one of the proposed reservoirs. a quarry was opened, and the raw material was delivered by a gravity plane to a crushing plant, 230 m. from the quarry and at a level about 50 m. lower. the plant consisted of a no. 5 austin gyratory rock-crusher, fitted with elevators and revolving screens of various dimensions, driven by a 150-h.p. erie steam engine; two sets of traylor's heavy-duty crushing rolls, one having 30 by 16-in. and the other 18 by 12-in. rolls; and a niagara sand disintegrator. this plant, except during a short period when the requirements were beyond its capacity, was able to produce all the sand and rock required for construction purposes. more than 40,000 tons of rock were quarried, the greater part of which was converted into crushed stone and sand. table 2 gives the chemical analysis of the chief constituents of the various sands examined. table 2.--analysis of sands in the neighborhood of monterrey. key: a: percentage of silica (absolute), sio_{2} b: percentage of alumina, al_{2}o_{3} c: percentage of sesquioxide, fe_{2}o_{3} d: percentage of lime carbonate, caco_{3} ===+============================+=======+=======+=======+=======+ no.| location. | a | b | c | d | ---+----------------------------+-------+-------+-------+-------+ 1.| arroyo seco, near | | | | | | brickyard at monterrey | 60.10 |17.95 | 2.89 | 8.01 | 2.| arroyo seco, near | | | | | | brickyard at monterrey, | | | | | | no. 2 | 42.92 |14.26 | 4.66 | 34.58 | 3.| near garcia station, | | | | | | mexican national r. r., | | | | | | chiquito river, no. 1 | 50.22 | 9.72 | 1.44 | 34.62 | 4.| near garcia station. | | | | | | mexican national r. r., | | | | | | chiquito river, no. 2 | 48.7 | 4.92 | 8.28 | 35.43 | 5.| san luis potosí | 85.02 | 5.00 | 7.38 | 2.21 | 6.| topo grande, pesquería | | | | | | river | 40.20 | 5.15 | 4.25 | 46.50 | 7.| hornos, near torreón | 77.9 | 13.1 | 2.4 | 4.9 | 8.| salinas river, at salinas | 41.5 | 5.7 | 1.4 | 48.2 | 9.| pits near caballeros, on | | | | | | tampico branch of | | | | | | mexican central r. r. | 73.4 | 5.6 | 4.4 | 10.1 | 10.| santa catarina river, | | | | | | near san geronimo | | | | | | (washed sand) | 12.40 | 2.06 | 1.14 | 81.70 | 11.| santa catarina river, | | | | | | at monterrey | 17.4 | 2.50 | 2.00 | 77.00 | 12.| composition of rock, quarry| | | | | | in foot-hills opposite | | | | | | monterrey, monterrey | | | | | | water-works and sewer | | | | | | company's property | 40.44 | 15.70 | 2.20 | 34.30 | 13.| manufactured sand from | | | | | | above quarry | | | | | | (run of crusher) | 51.80 | 12.14 | 8.7 | 32.6 | | | | | | | ===+============================+=======+=======+=======+=======+ the chief sands used for ordinary building purposes in monterrey are nos. 10 and 11, which are procured from the bed of the santa catarina river. as these sands contain large proportions of lime carbonates, which make them very undesirable for important structures, their use was limited to relatively unimportant work. the best sands procurable were nos. 5 and 9, but the long distance of the pits from monterrey, and consequently the heavy freight rate, made their use prohibitive on economical grounds. the best of the available sands, although it was very fine, was no. 7, from hornos, near torreon, as it could be depended on for uniformity and could be obtained f. o. b. cars at monterrey for 3.18[5] pesos per ton. [5] all costs given in this paper are in mexican pesos, one peso being equivalent to 50 cents in u. s. currency. the bulk of the sand and crushed rock used was similar to nos. 12 and 13, and reference to the cement sand tests in table 3, will show that the manufactured sands gave very satisfactory results. table 3 gives the average tests made with the "hidalgo" cement and various sands, alone and in combination, for the purpose of obtaining comparative results; the mixtures tested were composed of 3 parts of sand to 1 of cement. table 3.--tests of "hidalgo" cement with various sands. =====================================+============+============ sand. | at 7 days. | at 28 days. -------------------------------------+------------+----------- ottawa (standard) | 305 lb. | 414 lb. monterrey, 1-1/2 parts, } | | hornos, 1-1/2 parts } | 188 " | 313 " monterrey | 253 " | 365 " hornos | 202 " | 301 " manufactured sand, company's crusher | 372 " | 566 " hornos, 2 parts, } | | crusher sand, 1 part } | 231 " | 352 " hornos, 1-1/2 parts, } | | crusher sand, 1-1/2 parts } | 265 " | 346 " hornos, 1 part, } | | crusher sand, 2 parts } | 248 " | 328 " =====================================+============+============ the hornos sand was used during a few weeks in the latter part of 1908, when the crusher was unable to produce all that was required. its use was restricted to thick walls which were required to be water-tight, and it was always used in equal proportions with the crusher dust. estanzuela supply. [illustration: fig. 8.--location plan of estanzuela dam.] _intake works._--the intake (fig. 8) is about 1 km. below the lowest spring and at a point where the maximum flow of the stream was observed. the works consist of a small monolithic concrete dam, placed obliquely across the stream at an angle selected for the purpose of obtaining a foundation running parallel to the direction of the strata, which at this point were lying almost vertically across the bed of the stream. above these strata the stream bed was formed chiefly of large cemented limestone blocks and smaller conglomerate. no storage being possible in this valley, which has a very precipitous fall, the height of the dam was fixed merely to obtain a small settling basin for sand and débris brought down in time of flood. the dam foundation was excavated to bed-rock, from which the upper disintegrated portions were carefully removed; the rock was then stepped, and dovetailed recesses were left for properly bonding the concrete. the dam is carried well into the banks. its extreme length is 52 m., its maximum height 4.50 m., and its greatest thickness 2 m. the up-stream face has a batter of 1 in 12, and the down-stream face, 1 in 8. the top of the wall is 1 m. thick. for the discharge of flood-water there is a weir 10 m. long, and it was calculated that with a depth of 1 m. it would discharge about 400 times the ordinary flow, or about 23,000 liters per sec., but, in addition, the whole length of the dam (excluding that occupied by the gate-house) was arranged for the discharge of abnormal floods, one of which, on august 27th, reached the enormous quantity of 82,070 liters (2,900 cu. ft.) per sec., or 825 cu. ft. per sec. per sq. mile of drainage area, a remarkable run-off from so small an area as 910 hectares. the concrete forming the dam is a 1:3:5 mixture. the overflow sill is 692 m. above sea level. when the dam was completed it was filled to the overflow level, in order to test the water-tightness of the basin, which, when cleared, was found to be slightly fissured on the north side. the leakage was sufficient to cause a serious loss during periods of drought, and it was then decided to line the basin with concrete, so that the stream would enter it without being under a head greater than its own depth. the length of the basin, measured along the center line of the original stream surface, is 85 m., and its area is 1,100 sq. m. at its upper end it is merely a lined channel, 5 m. wide at the entrance. the floor of the basin has a fall of 4 m. the lining was formed in two thicknesses totaling 30.5 cm. (12 in.) of 1:2-1/2:3-1/2 concrete, laid in panels approximately 3 m. square, the upper panels breaking joint with those immediately below; in this way a very satisfactory and water-tight lining was obtained. a parapet wall, 45.7 cm. high, surrounds the basin. for scouring out the basin a 30.5-cm. (12-in.) cast-iron pipe was taken through the dam at the lowest point, this pipe being provided with a gate-valve encased in concrete on the down-stream face. the gate-house was built in connection with the dam at the north end of the overflow weir, its inner dimensions being 4.34 by 2.80 m. the substructure, to the level of the dam, is of concrete founded on the solid rock, and the superstructure is of brick rendered with cement plaster. the roof is of framed timber with red french tiles. the intake pipe is of cast iron. 40.6 cm. (16 in.) in internal diameter, fitted outside with a movable copper screen which is further protected by a wrought-iron hinged screen to prevent damage from stones, floating timber, etc., during times of flood. inside the gate-house the outlet pipe is provided with a 40.6-cm. (16-in.) sluice-valve, operated from the floor level by a vertical head-stock with worm-gearing. the gate-house has a scour-out pipe (also operated by a head-stock) and duplicate copper screens fitted to iron frames. from this house the water is conveyed to the upper portion of the conduit, which is a 45.7-cm. (18-in.) cast-iron pipe. of the total area of land, 885 hectares (2,187 acres), owned by the company, 392 hectares (970 acres) have been fenced in, to prevent any contamination of the springs. this fence is formed of five lines of barbed wire protected with stout hog netting at the bottom, in order to prevent more particularly the entrance of goats, many thousands of which pasture in the adjoining mountains. on the high ground immediately below the intake, a 3-roomed stone house has been constructed for the inspector in charge of the intake works, who also keeps in daily touch with the general office and records the condition of the stream, particulars of rainfall, etc. _aqueduct._--the total length of the aqueduct, from the intake dam to the south reservoir, is 18,700 m., made up as shown in table 4. table 4.--estanzuela aqueduct. +===========================================================+==========+ | description. |length, | | |in meters | +-----------------------------------------------------------+----------+ | | | |cast-iron pipes, 45.7 cm. (18 in.) in diameter, along | | | the stream bed of the estanzuela river | 110 | | | | |concrete tubes, 55.9 cm. (22 in.) in diameter, | | | to mederos (including 281 m. of tunnel) | 4,473.81 | | | | |cast-iron siphons, 45.7 cm. (18 in.) | | | in diameter: calabozos 239 m | | | south virgen 124 " | | | north virgen 177 " | | | mederos 426 " | | | ----| 966 | | | | |concrete tubes, 63.5 cm. (25 in.) in diameter, | | | mederos to south reservoir. |12,039.19 | | | | |cast-iron siphons, 50.8 cm. (20 in.) in diameter: | | | necaxa 315 m.| | | san augustin 796 " | | | ----| 1,111 | | | | +-----------------------------------------------------------+----------+ | total |18,700 | +===========================================================+==========+ the gradient of the concrete pipes is 0.43% from estanzuela to mederos, and 0.53% from mederos to the south reservoir. the calculated discharging capacity of the conduit when running full is 364 liters (13 cu. ft.) per sec. for the upper, and 465 liters (16.4 cu. ft.) per sec. for the lower section. for these pipes, the coefficient, _n_, in kutter's formula, was taken at 0.013. at present the line has been limited by overflows to discharge three-quarters full. the increase in the size of the pipes from mederos is for the purpose of receiving the waters of the mederos river and other springs in the san pablo and aqua verde catchment areas, as shown on plate ii. the invert of the concrete conduit where it leaves the estanzuela river is 684.25 m. above datum, and at the valve-house of the south reservoir it is 589.00 m. the concrete pipes were manufactured and laid under contract with mr. arthur s. bent, of los angeles, cal., the company providing all materials, labor, etc. the contractor was paid 10 cents per lin. ft. of pipe manufactured and 10 cents per lin. ft. laid. he was also responsible for the satisfactory completion of the work. [illustration: fig. 9.--estanzuela pipe line steel forms for the manufacture of concrete pipe.] fig. 9 shows the details of the joint recommended by mr. schuyler and adopted for these pipes. the 63.5-cm. (25-in.) pipes were 61 cm. long and 76 mm. (3 in.) thick. the 55.9-cm. (22-in.) pipes were of the same length, but 70 mm. (2-3/4 in.) thick. for the purpose of strengthening these pipes while hauling them over very rough roads they were reinforced with four rings of no. 6 galvanized-iron wire. _manufacture of pipes._--the pipes were manufactured under the supervision of mr. h. stanley bent, at a pipe yard established below the crushing plant, from which the crushed rock and sand were delivered by gravity in bogies run on narrow-gauge rails. the area of the pipe yard was approximately 1-1/4 hectares, and it was laid out with parallel lines of 76-mm. (3-in.) galvanized-iron piping with hose couplings for sprinkling purposes. after trials with aggregates of various sizes, the concrete for the pipes was proportioned by volume as follows: crushed rock broken to pass through a 19-mm. screen 0.136 cu. m. manufactured sand (run of rolls) 0.119 " " portland cement 0.090 " " ----------- total 0.345 cu. m.= (12.2 cu. ft.) [illustration: plate iii, fig. 2.--steel forms for moulding concrete tubes, estanzuela aqueduct.] the above quantity manufactured two 63.5-cm. pipes; a 55.9-cm. pipe required 0.1415 cu. m. (5 cu. ft.) of the material, in the same proportions. fig. 9 shows the forms for these pipes, and fig. 2, plate iii, illustrates the process of moulding. the forms consist of cast-iron bottom rings, to the proper section of the joint, and inner and outer steel forms of 3-mm. plate, provided with inner and outer locking arrangements. the concrete was poured through a cast-iron hopper which fitted to the top of the outer form. the concrete, which was mixed very dry, in a 1/2-cu. yd. batch, "smith" mixer, was thoroughly tamped with a 22-lb. tamper, and worked until it was of a stiff jelly-like consistency, the wire rings being added as the concrete was placed. the best results were obtained with the minimum quantity of water. the upper joint was moulded with a heavy cast-iron ring. the jacket and core forms were loosened immediately, and placed over other rings, a sufficient number of bottom rings being used for a day's work. for the pipes required for curves, special forms were used to give the necessary bevel to the joint. after 24 hours the finished pipes were lifted from the bottom ring with a special lifter, and ranged in position for coating internally with a portland cement grout to which a little freshly slaked lime was added. the pipes were all numbered, and were kept moist for 10 days by constant sprinkling. they were not hauled to the work until 28 days after they were moulded, although this rule was sometimes broken, to the detriment of the pipes. more than 32,000 pipes were manufactured, but some were used for purposes other than the estanzuela aqueduct. _cost of pipes._--the contractor brought with him experienced concrete pipe makers from california, and these were afterward assisted by mexican labor. in a day two tampers could manufacture from 45 to 50 pipes of the larger (63.5-cm,), and from 55 to 60 of the smaller (55.9-cm.) size. the cost varied from 2.75 to 3.25 pesos per pipe for the smaller, and from 3.50 to 4.00 pesos for the larger size. the approximate cost of manufacturing is as follows: taking, as a fair example, one week's work during march, 1908, the wages paid to the 74 men comprising the total pay-roll (though part of this labor was intermittent) amounted to 981 pesos. this includes a general foreman at 10 pesos per day, four american tampers at 7.50 pesos, and mexican labor varying from 4 to 1 peso, and all labor necessary to handle and finish the pipes, including coating the interiors. during this week there were made 1,126 of the 63.5-cm. and 1,095 of the 55.9-cm. size. the pay-roll includes 520 pesos for the larger pipes (46 cents each) and 461 pesos for the smaller pipe (42 cents each). table 5 shows the quantities and cost of the materials used in the manufacture of these pipes. table 5.--cost of concrete pipe. ========================================+=============================== | for 1,126 pipes 63.5 cm. | in diameter. materials. +-------------+---------------- | quantities. | cost. ----------------------------------------+-------------+---------------- portland cement, at 8.00 pesos per | | bbl., delivered at pipe-making yard. | 401 bbl. | 3,208.00 pesos. sand, at 2.65 pesos per cu. m. | 85 cu. m.| 225.25 " crushed rock, 19-mm. (3/4-in.), at 2.65 | | pesos per cu. m. | 62 cu. m.| 164.30 " no. 6 galvanized-wire hoops. 4 rings | | to each pipe. | 4,504 | 203.00 " ----------------------------------------+-------------+---------------- totals. | ... | 3,800.55 pesos. ----------------------------------------+-------------+---------------- cost per pipe. | ... | 3.37 pesos. ========================================+=============+================= ========================================+============================== | for 1,095 pipes 55.9 cm. | in diameter. materials. +-------------+--------------- | quantities. | cost. ----------------------------------------+-------------+--------------- portland cement, at 8.00 pesos per | | bbl., delivered at pipe-making yard. | 303 bbl. | 2,424.00 pesos. sand, at 2.65 pesos per cu. m. | 68 cu. m.| 180.20 " crushed rock, 19-mm. (3/4-in.), at 2.65 | | pesos per cu. m. | 50 cu. m.| 132.15 " no. 6 galvanized-wire hoops. 4 rings | | to each pipe. | 4,380 | 183.00 " ----------------------------------------+-------------+--------------- totals. | ... | 2,919.45 pesos. ----------------------------------------+-------------+--------------- cost per pipe. | ... | 2.66 pesos. ========================================+=============+================ from table 5 it is seen that the cost of the 63.5-cm. pipes was 3.37 pesos for material plus 0.46 peso for labor = 3.83 pesos per pipe, or 6.26 pesos per lin. m. (1.91 pesos per lin. ft.). the cost of the 55.9-cm. pipes amounted to 2.66 pesos for material plus 0.42 peso for labor = 3.08 pesos per pipe, or 5.05 pesos per lin. m. (1.54 pesos per lin. ft.). the cost of cement included hauling from the bodega to the yard, a distance of about 5 km. at a later date, after the company had commenced using the "hidalgo" cement, some additional 55.9-cm. pipes were manufactured, so as to have them on hand as a reserve in case of emergency. in this work only mexican labor was used, as the previous gang had been dispersed, but the tampers had previous experience. taking the cost of 418 pipes made during one period of 9 days, the detailed cost was as given in table 6. table 6.--cost of 55.9-cm. concrete pipes. ========================================+=============================== | for 1,126 pipes 63.5 cm. | in diameter. materials. +-------------+---------------- | quantities. | cost. ----------------------------------------+-------------+---------------- portland cement, at 8.00 pesos per | | bbl., delivered at pipe-making yard. | 401 bbl. | 3,208.00 pesos. sand, at 2.65 pesos per cu. m. | 85 cu. m.| 225.25 " crushed rock, 19-mm. (3/4-in.), at 2.65 | | pesos per cu. m. | 62 cu. m.| 164.30 " no. 6 galvanized-wire hoops. 4 rings | | to each pipe. | 4,504 | 203.00 " ----------------------------------------+-------------+---------------- totals. | ... | 3,800.55 pesos. ----------------------------------------+-------------+---------------- cost per pipe. | ... | 3.37 pesos. ========================================+=============+================= ========================================+============================== | for 1,095 pipes 55.9 cm. | in diameter. materials. +-------------+--------------- | quantities. | cost. ----------------------------------------+-------------+--------------- portland cement, at 8.00 pesos per | | bbl., delivered at pipe-making yard. | 303 bbl. | 2,424.00 pesos. sand, at 2.65 pesos per cu. m. | 68 cu. m.| 180.20 " crushed rock, 19-mm. (3/4-in.), at 2.65 | | pesos per cu. m. | 50 cu. m.| 132.15 " no. 6 galvanized-wire hoops. 4 rings | | to each pipe. | 4,380 | 183.00 " ----------------------------------------+-------------+--------------- totals. | ... | 2,919.45 pesos. ----------------------------------------+-------------+--------------- cost per pipe. | ... | 2.66 pesos. ========================================+=============+================ _excavation for pipe line and siphons._--the excavation for the pipe line and for bridge works, etc., was let by contract to messrs. scott and lee, of monterrey, under three classifications: (1) "all material which in the judgment of the engineer can be economically loosened with picks and handled with shovels." (2) "indurated earth or gravel, shale or rock which can be loosened without blasting, and 'sillar', locally so-called, whether pure or mixed with other substances, and whether it requires blasting or not." (3) "all rock not included in the above which requires drilling or blasting." locally, this classification is well understood, particularly no. 2, as it covers the sillar soils which are common in the neighborhood of monterrey. the contract prices were: no. 1, 50 cents; no. 2, 1.50 pesos; and no. 3, 2.50 pesos per cu. m. these prices were over and above the clearing and grubbing of the line, which was paid for at the rate of 100 pesos per hectare. the route of the pipe line being along broken country, at some points difficult of access, service roadways, about 3 m. wide, for hauling material were constructed, and, for about 7 km., a roadway was made along the line of the trench. the prices for the roadway, under the above classification, were: for no. 1, 35 cents; no. 2, 1.50 pesos; and no. 3, 2.50 pesos per cu. m. the trenches were excavated 5 cm. below the required finishing depth, to allow for grading the pipes in selected material, and were taken out to an average width of 40 cm. greater than the outside diameter of the pipe, to allow for their proper jointing, and also to give sufficient room to roll the pipes in the trenches. the final quantities of excavation were: trench: no. 1 11,115 cu. m. no. 2 18,096 " " no. 3 6,650 " " ------------- total 35,861 cu. m. roadways: no. 1 4,165 cu. m. no. 2 1,999 " " no. 3 30 " " ------------ total 6,194 cu. m. the route of the pipe line was laid out so as to obtain an average fill of not more than 1 m. over the tops of the pipes, but in some cases the cuts, for short lengths, were 3 m. deep. the excavation for this work began in june, 1907. _hauling pipes._--the pipes were hauled to the site of the work with ox-carts and mule teams. the cost of hauling varied from 25 cents per pipe at the lower end, to 1 peso per pipe at the upper and, comparatively speaking, inaccessible portion of the line. the weight of each 55.9-cm. pipe was about 182 kg.; that of each 63.5-cm. pipe was about 216 kg. the breakages in all the pipes cast at the pipe yard amounted to about 1%, due chiefly to unloading them carelessly near the pipe line. _pipe laying._--the pipe-laying gang was composed of 7 mexicans under the direction of an american foreman, who was in charge of several gangs. one gang could lay daily from 60 to 73 m. (from 100 to 120 pipes). the following was the ordinary pay-roll for one gang: 1 foreman at 8 pesos (proportion). 2.00 pesos. 1 pipe layer at 3 pesos. 3.00 " 1 pipe layer's assistant at 2 pesos. 2.00 " 1 cement mixer at 2 pesos. 2.00 " 2 outside plasterers at 2.50 pesos. 5.00 " 2 inside plasterers at 2.25 pesos. 4.50 " 1 water boy at 0.50 peso. 0.50 " ---------- total. 20.00 pesos. this brings the average cost of laying the pipes to 32.8 cents per lin. m. the pipes were jointed with 1:2 cement mortar, the outer joint being rounded over both pipes for a width of 12-1/2 cm. (5 in.) and a height of about 19 mm. (3/4 in.). in making these joints the pipe layers wore rubber gloves. the joints were kept moist, and the trench was back-filled with fine, screened material to a depth of 10 cm. above the top of the pipe. inside, the joints were carefully caulked with cement and rendered smooth, the plasterers working continuously along with the pipe layers, doing from 20 to 35 m. at a time. water had to be conveyed to the trenches by barrels on burros, and during the dry season it was sometimes carried 5 or 6 km. [illustration: plate iv, fig. 1.--typical reinforced concrete girder bridge, estanzuela aqueduct.] [illustration: plate iv, fig. 2.--elliptical arch bridge carrying estanzuela aqueduct.] _bridges._--the line as laid out passed over many gulches and dry arroyos, and these were crossed with reinforced concrete bridges of varying spans and heights, two being shown on plate iv. these bridges were formed of continuous horizontal girders, 1.10 m. deep and 1 m. wide, with a cantilever overhang at the abutments, varying in length from 1 to 2 m., so as to avoid settlement between the pipes and the bridges. the bottom reinforcement consisted of from 2 to 6 twisted bars of mild steel, varying in different spans from 12.7 to 19 mm. (1/2 to 3/4 in.) in diameter. the turned up bars were 28-1/2 mm. (1-1/8 in.) in diameter; they were placed on either side, carried over the upper part of the beams, and continued along the end for the overhanging part of the girder. these bars, when not obtainable of the full length, were spliced with a lap of 1.2 m. with no. 6 galvanized-steel wire. the vertical stirrups were 4.7 by 25.4 mm. (3/16 by 1 in.), of mild steel; they were equally spaced 30.5 cm. (12 in.) apart, and carried all around the girders, lapping at the center about 15 cm. (6 in.), all the steel being carefully wired together before placing the concrete. the general type of the piers and abutments is shown by fig. 1, plate iv, and varies in height with practically every bridge, the foundations in every case resting on hard rock. the concrete for the girders was a 1:2-1/2:3-1/2 mixture, the crushed stone used having all passed a mesh of 19 mm. (3/4 in.). the piers were of 1:3-1/2:5-1/2 concrete, and heavy "displacers" were embedded within them. the concrete was placed after the pipes had been laid through the form by the pipe contractor, the joints being kept clear of the bottom to the required distance by small moulded concrete blocks. the tops of the girders were moulded to a slightly segmental form. the bridges were all kept watered for about 15 days, and the forms were not struck for 28 days after placing. at station 13.4 the pipes were carried over a picturesque arroyo on an elliptical arched bridge (fig. 2, plate iv) of 11 m. clear span. the abutments of all bridges were protected by rubble walls in cement mortar carried up 60 cm. above the tops of the girders. the contract price for the concrete work of these bridges, the company furnishing the steel and cement, was 14 pesos per cu. m., and for placing reinforcing steel 35 pesos per metric ton (2,204 lb.). there are 49 single-span bridges, the larger spans being 9.10 m.; 8 two-span, and 11 three-span bridges, their total length, including the overhang, amounting to 870.50 m., or 4-1/2% of the whole length of aqueduct. _concrete aprons._--at 76 points there were small depressions which did not necessitate the construction of bridges, and at these places the pipes were encased in blocks of concrete carried up the hillside in the form of an apron having small abutment walls from 1 to 2 m. apart. this also served to protect the pipes from scouring action during rainstorms. at the upper end of the line, near the intake, the pipe had to be protected by concrete continuously for a distance of about 300 m., in order to prevent damage from falling rocks. [illustration: plate v, fig. 1.--ventilating column and entrance manhole, estanzuela aqueduct.] _ventilators and manholes._--along the route of the concrete pipe there are 27 ventilators, one of which, together with an entrance manhole, is shown by fig. 1, plate v. they consisted of simple concrete columns, 3.35 m. high, above the ground line, the interior of the shafts being formed of fire-clay pipes, 15 cm. (6 in.) in diameter. at each ventilator the pipe was cut and a block of concrete, the width of the trench, filled in as a foundation. entrance manholes were also placed at 49 points, at 27 of which they immediately adjoined the ventilating columns. _estanzuela tunnel._--at 1,560 m. from the intake at estanzuela, the conduit is laid through a tunnel 281 m. long. the tunnel was driven through hard calcareous strata from the open cuttings at each end. the inner dimensions were trimmed to approximately 2 m. high and 1-1/2 m. wide. at the ends of the tunnel the rock was moderately easy to take out, but the inner section was very hard and difficult to blast. ordinary hand drilling was adopted, and the actual cost of driving varied from 28 pesos per lin. m. at the ends to 50 pesos in the center. the pipes were laid through the tunnel in the ordinary way, and back-filled from the center, so as to give a cover of about 45 cm. above to protect them from falling pieces of shale. [illustration: plate v, fig. 2.--placing concrete pipes in forms for bridge crossing at north end of tunnel, estanzuela aqueduct.] _siphons._--it has already been mentioned that there are 6 cast-iron pipe siphons. the head on these varies between 10 and 38 m. all are provided with special inlets and outlets, forming combined overflow and ventilating chambers, and have wooden hand-sluices to divert the water when necessary. the bottoms of all siphons are provided with 20-cm. cast-iron scour-out pipes, fitted with valves, and carried down to a lower point to obtain a free outlet. the valve-boxes are protected by being placed in heavy concrete chambers carried up above the level of ordinary floods. the siphons are formed of cast-iron socket pipes, 3.65 m. (12 ft.) long, caulked in the ordinary way with lead joints. the thickness of the 45.7-cm. (18-in.) pipes is 19 mm.; that of the 50.8-cm. pipes is 21 mm. on the steep hillsides the pipes are anchored securely to the rock in concrete blocks reinforced with heavy iron chains. in some cases these siphons were difficult of access, but ox-teams hauled the pipes in a very efficient and satisfactory manner. _overflow chambers._--the ordinary overflows, of which there are 14, are similar in design to the siphon inlets. _testing, etc._--when the line was completed it was tested for water-tightness, and the loss was found to be about 5%, part of which was probably due to absorption. at a later date it was found that the waters of the estanzuela river, which contain 150 parts of calcium carbonate (caco_{3}) per million, deposited a very fine film of lime on the interior of the pipes, completely filling any pores there might have been. at the present time there is no measurable leakage, thus proving that the character of the work is very satisfactory. the water was turned into the conduit on june 11th, 1908, and delivered to the city on the following day through a by-pass, before the reservoir was completed. the pipe line is patrolled daily by an inspector with the authority of a gendarme, so as to prevent the unlawful abstraction of water, a very necessary precaution in so dry a country. south distributing reservoir. the distributing reservoir for the estanzuela supply is at guadalupe, on the foot-hills to the south of the santa catarina river, about 2 km. from the center of the city. the reservoir is a covered one, of reinforced concrete, and its capacity is 38,000,000 liters (10,000,000 u. s. gal.). [illustration: plate viii, fig. 1.--general view of excavation and embankment for south reservoir before lining.] _excavation and embankment._--the heavy slope of the ground at the selected site made the circular form the most desirable. on the low side the ground was excavated about 2 m. below the original ground line, while the excavation at the upper part of the slope was about 12 m. deep. the excavated material consisted chiefly of sillar and limestone conglomerate, which when broken up forms a calcareous clay of an excellent character for the formation of embankments, when proper care is taken. the dimensions fixed for the internal diameter of the finished concrete work of the reservoir were: 81 m. (265.68 ft.) at the top, and a depth of water of 9 m., with sides sloping 55 in 100. [illustration: fig. 10.--south reservoir plan of excavation.] fig. 10 is a plan of the reservoir, with a cross-section of the excavation and embankment. on the lower side the original ground line was cut down in steps, and all loose earth, roots, etc., were carefully removed. the floor of the reservoir was chiefly sillar conglomerate, a hard material that required a considerable amount of blasting for its removal. the embankments were formed in 10-cm. layers of sillar and conglomerate broken into small fragments and then rolled with 3-ton sectional rollers drawn by teams of 4 and 6 mules, which assisted in disintegrating the mass thoroughly, and produced by constant wetting a homogeneous and compact clay. the excavation and embankment were left so that 15 cm. of trimming could be done at a later date, immediately prior to the lining of the reservoir. the excavated material amounted to about 34,000 cu. m., and, of this quantity, 31,500 cu. m. were used to form the embankment; the remainder was taken to a spoil bank immediately adjoining, the black earth stripping being separated and reserved for covering the reservoir, etc. the contract prices for the excavated material placed in the embankment were: pesos per cubic meter class 1.--material which could be removed by plows and scrapers 0.60 class 2.--this consisted chiefly of "sillar" 1.09 class 3.--limestone conglomerate (requiring blasting) 1.65 the prices (for the same classification) for material taken to the spoil bank, were 0.40, 0.80, and 1.40 pesos, respectively. of the material taken out, 15% came under no. 1 classification, 80% under no. 2, and 5% under no. 3. the excavation was begun at the end of may, 1907, and completed in january, 1908, by scott and lee, the contractors. the embankments were then allowed to stand until the beginning of july, 1908, to permit the whole to become thoroughly settled and consolidated prior to beginning the lining. in july the work of trimming the embankments and excavating for the foundations of the reservoir columns was commenced, under the company's own administration, which completed the entire work. [illustration: plate vi.--details of beams and columns for south reservoir.] [illustration: plate viii, fig. 1.--details of forms for south reservoir.] [illustration: plate viii, fig. 2.--view of western half of south reservoir, showing final setting up of derrick on central columns.] _concrete lining and roof._--the general arrangement and details of the side-walls, columns, and roof are shown on plates vi, vii, viii and ix. the principal feature consists in dividing the reservoir into radial sections and supporting the roof on 135 primary and 670 secondary beams, from 135 columns, spaced as follows: outer ring, at 34.25 m. from center 40 columns. 2d " " 27.88 " " 40 " 3d " " 21.51 " " 20 " 4th " " 15.41 " " 20 " 5th " " 8.77 " " 10 " 6th " " 2.40 " " 5 " -- total 135 columns. the inner bottom diameter of the reservoir is 70.32 m. (230.64 ft.); the upper inside diameter is 81 m. (265.68 ft.); the water depth at the overflow level is 9 m. (29-1/2 ft). the roof was designed to carry a dead load (the earth cover) of 150 lb. per sq. ft., and a live load of 100 lb. the maximum compressive fiber stress in the concrete was assumed at 550 lb. per sq. in. for the beams, and at 350 lb. for the columns, a low figure, because of their eccentric loading. the tensile strength of the steel was taken at 14,500 and 16,000 lb. per sq. in. the twisted steel used for the column reinforcement was made at the local steel plant, but for the beams, etc., a twisted lug bar, of higher quality and greater permissible tensile stress, was used. the total quantity of steel used was 178 tons. it was calculated that the load on the column foundations would not exceed 1-1/4 tons per sq. ft. with the exception of the side-wall and floor, all the concrete was reinforced with steel, of the sizes and spacing shown on plate vi. _general construction and erection scheme._--the question of ordinary forms, requiring very heavy timber work, was a serious one, as suitable lumber is very expensive in mexico; and the necessity of finishing this reservoir before the end of the first term allowed under the concession, which expired on december 31st, 1908, led to the adoption of what the writer believes is an original scheme for so large a structure. this scheme was to cast the columns in short sections, mould the radial and secondary beams as separate members, and then place them in position with derricks. at the same time, in the case of the beams, it was important not to sacrifice either the benefit of that part of the slab which is ordinarily assumed to act as a part of the beam, or the additional strength due to continuity; and, in case of the columns, the strength due to the reinforcement extending from the foundation to the beams. the t-beam section was secured by notching the tops of the moulded members, with notches 10 cm. deep, throughout the lengths of the beams, as shown on plate vi. a computation of the maximum flange increment shows that these notches are sufficient to transfer the flange stresses to the stem, but, for additional security, flat steel bars were bent to a z-shape and embedded in the top of the beam, about 60 cm. apart. continuity in the beams was secured by carrying the steel to the tops of the beams over all supports, and, after erection, concreting them into the roof slab. the secondary beams, after casting, were dropped into recesses left in the radial beams for the purpose. _concreting, mixing, etc._--the radial beams and column sections were cast as nearly as possible under their ultimate positions; the secondary beams were cast outside and immediately adjoining the reservoir. the rock and sand was brought from the company's crushing plant, in 3-cu. yd., side-dump cars, running on a 30-in. track by gravity a distance of 1 km., the last 150 m. requiring hauling with 6 mules. the cars returned all the way to the crusher by gravity. these cars dumped the material into bins on the high ground above the reservoir; from there it was hoppered into cars which carried to the mixer all the material for one batch of concrete. two no. 1 smith mixers were used, and from 25 to 30 batches per hour could be handled in each machine. the concrete was transported from the mixers to place in 1/2-cu. yd., 18-in. gauge, swivel, steel dump-cars pushed by two men. all the concrete used in the bottom of the reservoir, for the main beams, columns, and floor, amounting to about 2,460 cu. m., was dumped through a chute into smaller cars. the chute had so many baffle-plates and bolts that it resembled a gravity mixer, but, although it was 12 m. long, it effectively prevented the separation of the materials. _concrete placing and moulding._--the square foundations for the columns were deposited _in situ_, a recess being left for the reception of the pedestals, which were moulded in place afterward. the capitals and pedestals were cast in one piece, and the columns in 1.21-m. (48-in.) sections, eight 5-cm. holes being left in them by using wrought-iron pipes, held in place by templates and removed when the castings were about 3 hours old. the columns were erected by threading them on the 15.8-mm. (5/8-in.) reinforcing rods, which extended from the pedestals up through the capitals. the rods were in two lengths, arranged to lap alternately at one-fourth, the center, and three-fourths of the height of the columns. in erection, a light timber frame was used in conjunction with the derrick, and, as the columns were placed, the reinforcing steel was grouted solid with 1:2 cement mortar. all the erection was done with a combined stiff-leg or guy derrick, having an 80-ft. boom and a 50-ft. mast, and fitted with a 30-h.p. lambert hoisting engine. the derrick was erected seven times at the circumference, and its final position was on top of the center columns. the moving of the derrick a distance of about 45 m. and its subsequent erection occupied usually about 48 hours. the erection work was carried on continuously, day and night, the placing of the whole of the radial and secondary beams and columns occupying 2-1/2 months. _forms._--as the erection scheme was designed to reduce the cost of forms, economical construction was of considerable importance. the wall was formed in 40 panels, about 6 m. wide and 11.27 m. high. the chief object in arranging them in this manner was to permit an expansion joint, 30 cm. wide, at each panel; this joint was not filled until after the completion of the roof, when the temperature inside the reservoir was uniform and not subjected to such great fluctuations as if exposed alternately to the hot sun and comparatively cool nights. the range of temperature during the construction period sometimes amounted to 80° fahr. in 24 hours. the expansion joints were left to the last, when a uniform temperature of about 70° inside permitted the filling of the joints, thus avoiding all trouble from expansion cracks. the forms are shown in detail on plate vii. they consisted of shutters stiffened with four trapezoidal trusses. the bottom posts of the trusses were fixed in holes formed in the foundation block; they were propped back from the embankment at the top, and secured to anchorages by iron rods. six sets of these forms were used to construct the whole wall. the concrete was placed in position through stove-pipe chutes, 20 cm. in diameter, in continuous layers, the workmen treading and spading it well as it was deposited. the forms were allowed to remain 4 or 5 days, and were then struck and removed to another section. the pedestals and capital forms were of lumber, and five of each were used to cast the total number required. in the column sections the outer steel forms used in the manufacture of the estanzuela pipes were adapted for this purpose. the radial beam forms, shown on plate vii, were arranged with internal wedge-shaped blocks to mould accurately the recess for the secondary beams. the bottom forms were left attached to the beams for 28 days, but the sides and ends were removed after 24 hours. eight forms were sufficient for the whole 135 beams. for the secondary beams, 29 forms were used for the 670 beams, the bottom lumber also being left until they were mature for handling. by referring to the cross-section of the secondary beam, it will be noticed that it is jug-shaped, shelves being left on either side for the support of the roof forms, which were placed after the secondary beams had been properly grouted to the radial ones. the lagging was laid diagonally, so that the short diameter was slightly greater than the distance between the beams. this greatly facilitated the removal of the lagging, as it was merely necessary to strike the wedge-shaped fillets beneath, and turn them clockwise, after tearing out the end lagging. [illustration: plate ix, fig. 1.--view of separately moulded secondary beams in yard below south reservoir.] [illustration: plate ix, fig. 2.--setting primary beams, south reservoir.] the writer believes that the adoption of forms of this type, rather than the ordinary kind, led to a saving of lumber of about 400,000 ft. b. m. during the erection and placing of the concrete, all the joining surfaces were carefully picked and cleaned, particular care being taken at the junction of the secondary with the radial beams, and the upper surfaces of all beams before laying the roof slab. after the greater part of the roof was completed, the floor was laid in those sections where it was protected from the sun's rays. the concrete was placed in two 15-cm. thicknesses, and the work was carried on night and day, without any joints. the laying of the floor occupied 8 days, or an average of nearly 100 cu. m. daily. [illustration: plate x, fig. 1.--view of completed section of south reservoir. expansion joints in side-wall not yet filled.] _proportions of concrete._--all the concrete work was brought to a smooth face by careful spading, no plastering being used throughout the reservoir, except in the superstructures. the work was kept well watered in every case for about 15 days. the whole of the concrete work in connection with the reservoir was completed in 5-1/2 months. the concrete for the columns and foundations was a 1:3:5 mixture, the aggregate consisting of equal parts of 19-mm. (3/4-in.) and 38-mm. (1-1/2-in.) crushed stone. the remainder of the concrete, except that for the roof, was a 1:2:4 mixture, the aggregate also consisting of equal parts of 19-and 38-mm. stone. with the exception of a short length of the side-walls, the sand used was that manufactured by the company. when the crushing plant was unable to produce all the sand required, the hornos sand (see table 3) was used in the side-walls in equal proportions with the crusher sand. _reservoir outlet and entrance tower._--the outlet, 61 cm. (24 in.) in diameter, leads from a well in the center of the reservoir and passes under the floor and embankment to an outside valve-pit, 89 m. from the center. this pipe was laid in a trench in a solid cutting before the construction of the embankment, and was encased in 1:4:8 concrete. where it passes under the embankment a 1:2:4 concrete cut-off wall, 3.6 m. wide, 2.5 m. high, and 1 m. thick, was placed across it at right angles. the cast-iron pipe is curved upward in the central well, and has a bellmouth on which rests a movable circular copper screen. above the outlet well, and on the roof of the reservoir, there is a central tower, giving access to the interior by a steel stairway. this tower also serves as a main ventilating shaft, and in it are arranged the guide-screens and gearing for raising them for cleaning purposes. in addition to the ventilation provided in the tower, 20 circular openings, 30 cm. in diameter, are carried through the roof of the reservoir at the circumference and into the parapet walls. _inlet gate-house, etc._--the inlet gate-house is above the reservoir and about 54-1/2 m. from its center. the conduit enters at 589.00 m. above datum, and the gate-house contains the valves for controlling the inlet pipe to the reservoir, the by-pass, overflow, scour-out pipe, and the copper screens. the inlet, which is 45.7 cm. (18 in.) in diameter, is of cast-iron flanged pipes, carried on iron hangers on the side-wall of the reservoir, and, at a point 90 cm. above the floor level, it is turned at right angles to the side-wall and carried on concrete piers to the center of the first row of columns. the end of the pipe is closed by a blank flange, and the water is deflected at right angles through two 30-cm. (12-in.) branches, for the purpose of setting up a slight circular motion as it enters the reservoir. the valve-pit is clear of the embankment, and in it are brought together the main supply and by-pass pipes on which are placed two 61-cm. (24-in.) sluice-valves; and between them there is a 20-cm. (8-in.) scour-out pipe, for emptying the reservoir into an adjoining arroyo. the arrangement of the valves gives complete control over the contents of the reservoir. _venturi meter-house._--fig. 11 shows the arrangement of the venturi meter and its automatic register in a house over the main supply pipe. this house is designed to form a feature of the entrance gateway of the reservoir grounds, which cover an area of 12 hectares. [illustration: fig. 11.--venturi meter-house.] _general._--the roof of the reservoir has been laid out as a garden, and the embankments are turfed. the intention is to develop the company's land as a public park, as it commands fine views of the city and the surrounding mountains. an inspector's house has been built, and a private telephone line provides for communication with the estanzuela intake and also with the general offices in the city. [illustration: plate xviii, fig. 1.--view of south reservoir, looking toward the city.] san geronimo gravity supply. _provisional supply._--it has already been stated that the company began operations at san geronimo in march, 1906, by sinking a well on the north bank of the santa catarina river at san geronimo. at this point, a little later, a small steam pumping plant, sufficient to handle about 8,000 liters per min., was installed. the lowest depth to which this well was ultimately sunk in water-bearing strata, was 7 m., the normal level of the water during 1906 and 1907 never falling lower than 569 m. above datum. tests made from time to time during 1907-08, showed that this well was capable of supplying nearly 10,000,000 liters (264,000 gal.) of water daily. the excellent supply yielded by this well made it desirable to adopt it immediately as a provisional measure, pending the completion of the larger works forming the western source of supply. to utilize the well to its fullest extent, a reinforced concrete reservoir, of 3,000,000 liters capacity, was constructed on the south bank of the river, the top water level being 585 m. above datum, that is, at the same elevation as the proposed reservoir for the estanzuela supply. the reservoir is 53.80 m. long, 21 m. wide, and has a water depth of 3.25 m. at the overflow level. it is excavated on a steep hill slope, and has an earth embankment on the lower side. the lining is of concrete, 20 cm. thick, and the roof is of reinforced concrete composed of flat arches springing from beams carried on 46 by 35-cm. reinforced columns. there are 68 of these columns, and they are 3 m. apart longitudinally and 5 m. apart transversely. the roof was not constructed until october and november, 1907, and prior to that time the necessity of covering the reservoir was amply demonstrated by the growth, during hot weather, of considerable quantities of green algæ, which had to be skimmed from the surface of the reservoir every few days. the delivery pipe from the pumping plant was originally of riveted steel and was asphalted. it was 30 cm. in diameter, 2 mm. in thickness, with slip joints, and where it crossed the river it was encased in concrete. this pipe was afterward replaced by a cast-iron pipe of the same diameter. the supply pipe to the city was also of sheet steel, 30 cm. in diameter. for a part of its length it was laid in the high ground of the south bank of the river, which it crossed near the western limits of the city, and was then connected to a 30-cm, cast-iron pipe in the distribution system. the total length of the pipe from the reservoir to the city distribution system was 2,850 m. this provisional pipe continued in service from october, 1906, until august 27th, 1909, when the river portion was completely swept away, together with the provisional pump-house at san geronimo, during the great flood in the santa catarina river. fortunately, the permanent supply works were completed at the time, so that the destruction of this pipe line, which had already served its original purpose, had no effect on the supply of water to the city. [illustration: plate xi.--section of infiltration gallery, san geronimo gravity supply.] _infiltration gallery._--the chief feature of the san geronimo gravity supply is the infiltration gallery. by referring to the profile on plate xi it will be seen that at this place there is a considerable area of what is undoubtedly water-bearing gravel. the main conditions were revealed by the borings previously carried across the valley, but the profile has been corrected to show the actual conditions as established at a subsequent date by shafts. practically, the water-bearing strata are not limited merely to the sand and coarse gravels, as the clay formation lying above and below them is full of small gravel deposits containing considerable volumes of water. the main direction of the underflow is toward the east, and the hydraulic gradient, which was established from wells sunk farther west, was found to be approximately 1%, or practically the same as the average surface of the bed of the river above the line of the infiltration gallery. the general scheme for tapping this underflow was to drive a main gallery at the 560-m. level on a grade of 0.05%, which was sufficiently high to take the supply by gravity to the western reservoir, having a top water level at 558.75 m. above datum. this elevation is sufficient to give an excellent pressure over about 60% of the city, and a fair pressure to reach the upper stories of the highest houses, if required, over the whole supply district. from this gallery it was proposed to sink shafts at frequent intervals, for a total distance of 300 m., carrying them below the gallery level, to tap any water-bearing gravels there might be in the clay formation underlying the gravels and sands. from the main gallery it was proposed to construct branch galleries up stream on a flat gradient, so as to obtain the advantage of an increased head due to the steep hydraulic gradient of the underflow water. [illustration: fig. 12.--diagram showing variation in water plane 1905 to march 1910 at san geronimo.] in investigations of this kind, it is of first importance to have a continuous record of the level of the water plane, and fig. 12 has been plotted to show its variation at san geronimo from the beginning of 1905 to march, 1910. from january, 1909, to march 31st, 1910, these levels are averages of daily readings taken in 9 shafts sunk along the proposed line of the infiltration gallery. in 1902 the water plane was standing at 570.18 m. above datum, but from that date until 1905 the writer has been unable to find any records. this diagram should be examined together with the rainfall diagram, fig. 3, and it will be noticed that the fall in the water plane drops with the general scarcity of the rainfall during 1907-08, and until july, 1909. the year previous to july, 1909, is regarded, by many competent local observers to have been the longest period of extreme drought in 30 years in nuevo león, and the evidence which the writer has been able to gather regarding stream flow in the neighborhood of monterrey supports this view. the total rainfall at monterrey for the year prior to july 1st, 1909, amounted to 9.98 in., or 4.16 in. less than the lowest record for any calender year since 1894, or, in other words, about 45% of the average annual rainfall. the lowest point to which the water plane dropped was during june and july, 1909, when the levels stood slightly above 565.00 m., or 5 m. above the level of the floor of the infiltration gallery. during this period pumping tests were made in the various wells, and from these it was quite clear that the infiltration gallery, if carried far enough to meet them all, would yield a supply of from 25,000,000 to 40,000,000 liters daily. during the great rainfall of august, 1909, the water levels rose very rapidly; the heavy precipitation between august 9th and 10th caused the level to rise to 568.00 m. in about 4 days, and 6 days after the great flood of august 27th, the water level, which had continued rising gradually, reached 571.40 m., and then fell gradually until at the end of march, 1910, it was practically the same as it had been from 1902 to 1905. [illustration: plate xii.--san geronimo gravity supply.] it should be noticed that the readings were taken in the shafts on the high ground to the west of the present river bed, and were independent of any flow there might be in the river. during times of ordinary floods in the river, it was very noticeable that, notwithstanding the fact that the river water might be turbid to an extreme degree, the well even in immediate proximity to the river bed did not show the least sign of discoloration. _design of works._--plate xii shows the general design of the gravity scheme, which consists of a main tunnel 550 m. long and a concrete aqueduct, 1.06 m. (42 in.) in internal diameter and 2,311 m. in length, discharging into a low-service distributing reservoir at the extreme western limits of the city. the tunnel and aqueduct were laid on a gradient of 0.05%, and the latter was designed to discharge 55,000,000 liters per day (22.8 cu. ft. per sec.) if flowing to its full capacity. _gravitation tunnel._--this tunnel, shown on plate xii and fig. 13, was completed prior to driving the infiltration gallery into the water-bearing gravel, so that the water encountered in the gallery could be easily drained off by gravity, thus avoiding a heavy outlay for pumping. the tunnel passes through various strata, the principal ones being calcareous shale, conglomerate, and gravels. the tunneling operations were carried on from 5 shafts, no. 1 being 23 m. deep, and the others varying from 20 to 10 m. the shafts in loose ground were timbered in the usual way, having clear inside dimensions of 2 m. shaft no. 1, which was entirely in shale, was taken out approximately to 3.35 m. in diameter, so as to permit it to be lined with concrete having a finished internal diameter of 2.43 m. [illustration: fig. 13.--general details san geronimo gravity pipe line.] fig. 13 shows the details of the tunnel, which was lined with concrete, the bottom and sides being approximately 23 cm. (9 in.) thick. the interior dimension is 0.91 m. at the invert level and 1.016 m. at a height of 1.22 m., the corners between the side-walls and the floor being slightly curved. the arch is formed of two rings of brickwork in cement mortar, this thickness being increased in some lengths to three rings. where the rock was in good condition, and not likely to disintegrate easily, the arch, for a distance of 90 m., was left unlined. of the total distance of 550 m., careful timbering was required for 300 m. in lining the timbered portion of the tunnel with concrete, all the timber was removed, except in loose ground, where the laggings were left in position. while the tunnel was being driven, a start was made to drive the north end of the infiltration gallery, which was in rock for a distance of 44 m. water appeared at about 35 m., and then the work was temporarily suspended until the gravitation tunnel was completed and a length of the aqueduct had been constructed far enough down stream on the north bank of the river to permit of draining direct to the river. this point was reached at 1,170 m. from shaft no. 1, and there a temporary overflow chamber was constructed. when the tunnel was completed, the two intermediate shafts were filled up, the remaining three being retained permanently. shafts nos. 2 and 3 were lined with concrete, 76 cm. (30 in.) in internal diameter, and 23 cm. thick. they were domed at the top to form circular openings to receive cast-iron covers. progress on this tunnel was slow, taking from december, 1907, to november, 1908, to complete, owing chiefly to difficulties with an incompetent contractor. the contract was subsequently transferred to mr. john phillips, of mexico city (who was also the contractor for the aqueduct), who completed it satisfactorily. _continuation of the infiltration gallery._--when the aqueduct (to be referred to again) was completed as far as 1,170 m. from shaft no. 1, the driving of the infiltration gallery, which was 2 m. high and 1-1/2 m. wide, was continued until gravel was encountered in the roof, at 44 m. from the shaft. at this point the rock dipped at an angle of 45°, and the gravels contained quantities of large boulders mixed with fine sand; immediately after encountering the gravel, a flow of about 90 liters per sec. was met, evidently coming through from a pot-hole in the shale. this quantity diminished in about 10 days to about one-fourth, but gradually increased again as the driving proceeded. the operations of driving the tunnel from 44 m. forward were begun in the dry season, in february, 1909, and the gravel was encountered for a distance of 24 m., or up to 68 m. from the shaft. the center of this gravel bed was about 30 m. south of the old river channel, which had been continuously dry at the surface for several years. up to 68 m. the work was very difficult, owing to the upper part being of loose gravel and the lower in very contorted shale. the timbering of the tunnel in the full gravel section consisted of heavy square settings, 1 m. apart. at 68 m. the clay and gravel formation was met, and the rate of progress then was about 4 or 5 m. a week. a short branch gallery was also driven about 7 m. up stream near shaft no. 2. the total distance the infiltration gallery was carried from shaft no. 1, was 100 m., when the floods of august, 1909, caused its suspension. during the progress of the gallery, attempts were made to sink a 3-1/2 by 2-m. shaft at a point along the line of the infiltration gallery, about 130 m. from shaft no. 1, but water in such abundance was encountered that it was practically impossible to sink it in the ordinary way more than about 6 m. deep, the quantity of water to be dealt with amounting to about 20,000,000 liters daily. seven shafts were then sunk in the high ground to the north of the river, five of these being on the line of the gallery and two 30 m. westward. they were sunk during the dry season prior to july, 1909. these were ordinary timbered shafts, 2 m. square between the walings, and were carried to the depths shown on plate xi. in shafts nos. 5, 6, and 7 the water was flowing with considerable velocity, while shaft no. 9 seemed to have penetrated a different water plane and one which was probably independent of that showing in any of the other shafts, in which the water was practically at a uniform level. the evidence obtained showed that if the gallery could be carried to shafts nos. 6 or 7 a great abundance of water would be intercepted. owing to the difficulties of sinking ordinary shafts in the wide river channel, circular shafts were put down. these were 1.37 m. in internal diameter and 23 cm. thick, and were of concrete reinforced with no. 10 vertical rods, 19 mm. in diameter, tied together with no. 6 wire. these shafts were provided with steel cutting edges. shaft no. 2 was sunk to a depth of 1 m. below the infiltration gallery level, no. 3 within 2 m., and no. 4 within 4 m., before august, 1909. the shafts were sunk by digging them out and loading them at the top, the top of the shafts being kept generally 3 m. out of the ground. shaft no. 3 encountered great volumes of water, and, in order to enable sinking operations to proceed, a pumping shaft, 2-1/4 m. square, was sunk a little west of it to draw off the water. notwithstanding the fact that the prolonged period of drought had lowered the general water plane in all the shafts to 565.00 m. above datum, the difficulties of handling the water even at that level were considerable. at the beginning of august the work was progressing very satisfactorily, but the extraordinary rainfall of that month caused the work to be shut down temporarily. _effect of the floods in the santa catarina river._--the area of the water-shed of the santa catarina river above monterrey is about 1,410 sq. km. (544 sq. miles), and its area at san geronimo, owing to its configuration, is practically the same. its general character has already been referred to. on the night of august 10th and early on the morning of august 11th, a big flood came down the river, flowing at its maximum about 1,130 cu. m. (40,000 cu. ft.) per sec., due to the heavy rainfall (fig. 4). this flood carried away all the temporary staging around the shafts, seriously wrecking the temporary pumping station, as well as destroying the 30-cm. cast-iron pipe, notwithstanding the fact that it had been encased in a block of concrete 3 m. wide and 1-1/2 m. thick right across the river; but no damage was done to the infiltration gallery or to the shafts in the river channel. the effect of the flood on this pipe is shown by fig. 2, plate xxxi. [illustration: plate xxxi, fig. 2.--profile sketch, looking up stream on line of 24-inch main supply pipe.] following this flood, which had caused the loss of 14 lives in the city, 3 miles below san geronimo, there was practically no rain for 13 days. then, on august 25th the second heavy precipitation began and continued until august 29th, the details being shown on fig. 4. this precipitation, therefore, fell on a water-shed which was completely saturated, as it had already absorbed a large proportion of the 13.38 in. of rain which fell during august 10th and 11th; and at every point along the river, prior to august 25th, springs were issuing forth, and there had been very little evaporation during the intervening dry spell. the writer has calculated that at monterrey this flood reached the enormous quantity of 6,650 cu. m. (235,000 cu. ft.) per sec., a rate equal to 432 cu. ft. per sec. per sq. mile of water-shed.[6] the effect of this flood was to demolish completely about 1,200 "sillar" houses (without taking into consideration the numerous wooden houses) at monterrey, and to cause a fearful loss of life, variously estimated between 3,000 and 5,000 persons; the lower figure the writer believes is approximately correct. at san geronimo the original pumping station was carried away entirely, leaving practically no trace whatever. [6] the writer, in a brief article contributed to _engineering news_ soon after the flood (september 23d, 1909), gave this figure as 271,500, or approximately equal to a run-off of 500 cu. ft. per sec. per sq. mile; but, from a later and more complete study of the conditions for many miles above monterrey, he believes the above quantity to be approximately correct. shaft no. 2 was apparently destroyed, while no. 3 was turned at an angle of about 50° down stream and filled up completely with sand. the infiltration gallery, near shaft no. 2, was completely blocked with fine sand and gravel, and access could only be obtained as far as 54 m. the profile, plate xi, shows the change which had taken place in the river bed. the original course of the stream was changed to the north bank, 50 m. distant, the effect of the scouring action of the flood being to lower the general level at this point about 3.65 m., while the southern portion of the channel was slightly raised. at present (april, 1910), the end of the driven portion of the infiltration gallery is about 35 m. from the center of the stream, which is still carrying about 2,270 liters (80 cu. ft.) per sec. immediately after the flood the flow in the gallery was 450 liters (16 cu. ft.) per sec., and this quantity has remained constant since that time. the probable effect of the flood was to disturb the whole subsurface above the infiltration gallery and put it in motion, completely cleaning the gravels of their surrounding clay, which would account for the large infiltration of water in so limited a distance. the water has always been limpid and pure, but its hardness remains the same as it was prior to the flood. with the copious supply of water from this source, due of course to abnormal conditions and not likely to be permanent, the operations of tunneling have been suspended temporarily; but it is proposed to continue the driving of the gallery, from a new shaft west of no. 3. the water encountered will be drained off by pumping until the main water-bearing gravels, in the neighborhood of shaft no. 5, are reached. it is also proposed to reconstruct the 30-cm. high-level pipe line, from san geronimo along the high road on the north bank of the river, so that by pumping water can be delivered to the city system from shafts nos. 5, 6, and 7, in the event of a shortness of supply from the estanzuela river. _shaft no. 1._--shaft no. 1 is designed to connect the infiltration gallery with the gravitation tunnel. this shaft has an inner diameter of 2.43 m. (8 ft.) and is fitted with a special gate-valve. in the bottom of the door of this valve there is a smaller valve, 30 cm. in diameter, so that, when the infiltration gallery is closed for cleaning out the sump, the smaller door, which is operated through the same spindle by a bevel-geared head-stock at the top of the shaft, can be opened first. space is also left for screens if these should be found necessary. access to this shaft is gained by a reinforced concrete stairway in nine stages. the superstructure is to be supported on reinforced concrete column foundations carried to the firm rock, owing to the loose condition of the strata at the top of the shaft. _aqueduct._--the construction of the concrete conduit was begun in april, 1908. fig. 13 shows the general types. type _a_ was adopted in gravel and conglomerate formation, and type _b_ where the excavation was in "sillar," the soft nature of this rock permitting it to be excavated exactly to the required external diameter of the concrete lining. the concrete which was without steel reinforcement was a 1:2-1/2:3-1/2 mixture, the sand being from the crusher and the aggregate from the river bed, screened to pass a 25-mm. mesh. where the conduit crossed the river obliquely, immediately below the gravitation tunnel, it was strengthened with mass boulder concrete of type _c_. during the great flood this heavy section withstood its effects without damage of any kind, but beyond this point, where the conduit had been laid in compact cemented gravels, the scouring action of the flood on the north bank lowered the level of the gravels from 2 to 3 m.; the only damage, however, was the scouring away of the gravels at the south side of the conduit. to prevent such an occurrence in the future, the conduit at that point was strengthened with additional concrete for a distance of 195 m., as shown on fig. 13. the extra concrete, amounting to 733 cu. m., was a 1:3:5 mixture, in which was embedded 20% of heavy boulders. the top of this special length now forms a weir for the present river flow. where the conduit enters the bluff on the north side of the river, at 1,200 m., there is an overflow chamber which has a sluice-gate 76 cm. wide, arranged so that the conduit can overflow at the present time when running 76 cm. deep. to deflect the flow in the conduit, a wrought-iron plate, provided with a balance weight, is dropped into a groove on the lower side. the outlet is a 61 cm. concrete tube, having its invert above ordinary flood level, and arranged to be closed by a gate. at 1,963 m. the conduit is carried over an arroyo on a segmental arch of 8 m. clear span, as shown on fig. 13. there are 5 ventilating columns and 5 manholes on the aqueduct. [illustration: plate x, fig. 2.--setting forms for san geronimo culvert.] the aqueduct terminates in the obispado distributing reservoir valve-house, at a level of 558.50 m. the work in connection with this aqueduct was completed by december, 1908. distributing reservoir at obispado. the main distributing reservoir for the san geronimo gravity supply is immediately below the historic obispado (bishop's palace), at the western limits of the city. the general arrangement and lay-out is shown on plate xiii. [illustration: plate xiii.--general plan and sections, obispado reservoir.] _valve-house._--the invert of the conduit from san geronimo, where it enters the valve-house, is 558.50 m. above datum. the valve-house, which is built in the center of the reservoir, is shown on fig. 2, plate xviii. one of its special features is the provision of the main overflow at this point instead of within the reservoir proper. the inlet, main supply tunnel, independent by-pass overflow, scour-out pipes, gate-valves, and screens, are all controlled within the valve-house. [illustration: plate xviii, fig. 2.--view of roof of obispado reservoir, looking north.] _reservoir._--the reservoir is rectangular, 126 by 81 m. (413.28 by 265.68 ft.) at the top, and has a water depth of 4 m. (13.1 ft.). in the design it was necessary to limit it to the lowest economical depth, so as to increase the static pressure over the low-pressure district as much as possible. _excavation and embankment._--the excavation, except for a depth of about 1 m. which was in black soil, was chiefly in a disintegrated "sillar" stratum of a heavy clayey nature, the greater part of which could be handled conveniently with plows and scrapers; the actual foundation on the eastern half required blasting for the final depths. the total excavation amounted to 56,479 cu. m., of which 7,255 cu. m. were placed in the embankment, the remainder being deposited in the immediate neighborhood of the reservoir. the final trimming of the banks, which were left 30 cm. full, was not undertaken until the lining was begun. the work was done under contract with mr. j. s. nickerson, of monterrey. the excavation had only one classification, and the contract prices were 0.50 peso per cu. m. for material carried to spoil banks, and 1.00 peso for material placed in the embankment. the excavation was begun in december, 1907, and completed in april, 1908. the work was then left standing until the end of 1908 to allow the banks to consolidate thoroughly prior to lining, which was begun on january 4th, 1909. _concrete lining and roof._--plate xiii shows the general plan and sections, the main feature being the simple division of the reservoir into 24 rows of columns longitudinally and 15 rows transversely, making a total of 360 columns, less the four left out at the central tower. all the columns are 5 m. apart both ways. the roof was designed for a live load of 100 lb. and a dead load of 150 lb., the same as at the south reservoir. with the exception of the floor, all the concrete work was reinforced with twisted steel lug bars. the foundation load on the columns for the eastern half of the reservoir is 0.9 ton per sq. ft.; that on the columns for the western half, where the foundation is of very hard sillar and conglomerate, is 1.95 tons per sq. ft. _under-drainage of the floor._--to provide for proper drainage in case of seepage, the floor was underdrained with rubble drains, 30 cm. wide and 23 cm. deep, filled with large round gravel carted from the bed of the santa catarina river. the total length of these underdrains is 1,160 m. in order to facilitate the detection of any seepage, they were conducted to a permanent inspection pit outside of the reservoir. _main distributing conduit._--the main distributing conduit is laid along the inside of the reservoir, at the inlet end, and carried on elliptical arches of 2 m. span to a height of 71 cm. above the finished floor level. this conduit is 76 cm. high and 45.7 cm. wide, and it branches in two directions from the inlet tunnel to each side of the reservoir, its total length being 69 m. in order to prevent any stagnation and to give a continuous circulation, the water is delivered at eight points, in the length of the distributing pipe, through square openings with semicircular tops, the areas of the openings increasing toward the ends. these inlets are placed so that the current will not strike the roof columns. _outlet tunnel and valve-house._--the outlet tunnel is at the north end of the reservoir, and was excavated in hard sillar rock. the tunnel is lined with concrete 30 cm. thick, the finished internal dimensions being 1.52 by 0.91 m. the length of the tunnel is 22.5 m. to the point where it enters the outlet-house. this house is divided by a wall 45 cm. thick, which supports a 76-cm. (30-in.) penstock-valve. the supply pipe to the city leaves this chamber in the west wall, and is also fitted with a 76-cm. penstock-valve. the supply pipe has a copper screen of the same design and dimensions as those in the inlet-house. a 30-cm. (12-in.) scour-out pipe in this chamber provides for draining the contents of the reservoir to a neighboring irrigation ditch, when necessary. the superstructure of the valve-house is of concrete, and at the floor level there are bevel-geared head-stocks to raise the valves, etc. _by-pass and supply pipes._--the by-pass and supply pipes are carried below the reservoir embankment to join the main 76-cm. (30-in.) cast-iron distributing pipe to the city. for this short distance they were constructed of concrete, 76 cm. in internal diameter, 10 cm. (4 in.) thick, reinforced with 6-1/2-mm. square steel longitudinal rods, 30 cm. from center to center in the circumference, and hooped with 6-1/2-mm. square steel rods spaced 30 cm. apart. the concrete forming these pipes was a 1:1-1/2:2-1/2 mixture. _parapet walls._--the parapet walls have 12 piers at each side and 8 at each end. in these piers there are ventilating openings branching at the top to each side of the parapet, with outlets provided with cast-iron screens. this arrangement gives 4 sq. m. of ventilating space (exclusive of that provided in the central tower), equally distributed at 40 points around the walls of the reservoir. _general construction scheme._--the concrete mixing plant, which consisted of two no. 1 smith mixers, was arranged in connection with the bins and hoppers for the rock and sand on the high ground to the west, and from there the material was conveyed on a framed timber gangway carried right across the center of the reservoir, as shown by fig. 1, plate xvii. from this central platform the concrete for the columns was filled from stages placed on the top of traveling towers, 5 m. high, which were run between two rows of columns on standard-gauge rails laid on the floor of the reservoir. by this arrangement 24 columns could be filled from each length of track. a main narrow track was also laid right around the reservoir, with the necessary turn-outs. [illustration: plate xvii, fig. 1.--filling primary beams from traveling tower, obispado reservoir.] [illustration: plate xv, fig. 1.--construction of west side-wall of obispado reservoir.] [illustration: plate xv, fig. 2.--primary beams and columns, obispado reservoir.] [illustration: plate xiv.--details of forms for concrete work, obispado reservoir.] the forms for the columns, primary and secondary beams, are shown on plate xiv. the side forms for the primary beams were struck in 24 hours, so as to economize lumber; but the bottom lumber was left in position for 28 days. to avoid much unnecessary timber, the secondary beam forms were supported at the ends on reinforced concrete corbels cast on the primary beams. for placing the side-walls, a special traveling form was used, the details of which are shown clearly on plate xiv. at the end of each form an expansion joint of 25 cm. was left to be filled after the roof was placed in position. the concrete was delivered to the wall through stove-pipe chutes, and carefully spaded by workmen in the limited space between the forms and the embankment. the wall form was removed after 36 hours, by loosening the jacks and pulling forward the hooked tie-rods. this form is also shown on fig. 2, plate xvi. [illustration: plate xvi, fig. 2.--traveling side-wall form, obispado reservoir.] [illustration: plate xvi, fig. 1.--preparing floor for concreting, obispado reservoir.] the concreting of the roof slab was carried on continuously, and, when partly completed, the floor was laid in the shade. the bottom layer of the floor, 13 cm. thick, was laid in continuous panels between the columns, and brought to a fairly smooth surface. on this surface, after keeping it wet for 10 days and then allowing it to dry thoroughly, a layer of asphaltum, supplied by the american asphaltum and rubber company, of chicago, was placed. the work was done by ordinary mexican laborers after they had received a few days' instruction from one of the asphaltum company's superintendents. the surface of the lower layer was kept perfectly clean, and then received one coat of "pioneer" paint. the asphaltum, heated in a boiler inside the reservoir to a temperature of approximately 425° fahr., was then poured over the floor from buckets, in a layer approximately 4 mm. thick. where the floor joined the column pedestals, and at each new panel section, a double thickness was used. the labor cost of water-proofing, including superintendence, etc., amounted to 3.3 cents (mexican) per sq. m. for painting with "pioneer" paint, and 5.4 cents for the asphaltum coating, or a total labor cost of 8.7 cents per sq. m. for the complete water-proofing. this cost is based on a rate of 8.00 pesos per day for a foreman, and 1.00 peso for each laborer. it required 50 u. s. gal. of the paint to cover 265.2 sq. m., and an average of about 6 lb. of asphaltum for 1 sq. m. the upper concrete layer of the floor, 10 cm. thick, was placed so as to break joint with the lower, and was brought to a smooth surface with wooden floats sheathed with steel and reaching across the panels. in this way a perfectly smooth surface was obtained without any plastering. [illustration: plate xvii, fig. 2.--central tower and stairway, obispado reservoir.] the concrete for the beams, columns, side-walls, and floor, was a 1:2-1/2:4 mixture, crushed sand and stone being used throughout. in the roof slab the mixture was 1:2:3. the whole of the concrete work of the reservoir was completed in 6 months, by the company's own administration, and the reservoir was first put into service a few days after the great flood of august 27th, when the estanzuela supply main, crossing the santa catarina river, was partly destroyed. since that time frequent examinations of the inspection pit, which is connected by a pipe to the rubble drains under the floor, have never revealed the slightest leakage. _lay-out of the reservoir roof and grounds._--the company owns about 11-1/2 hectares of land, which includes that occupied by the reservoir and its surroundings, and as this property is in an attractive situation, commanding fine views of the sierra madre mountains, the whole of the works have been given a pleasing architectural character, and the grounds laid out to form a public park for the citizens of monterrey. [illustration: fig. 14.--sketch plan of lay out at obispado reservoir.] the general plan of the scheme is shown by fig. 14 and fig. 2, plate xviii. the roof, which has an area of 1 hectare, has been laid out with walks and grass plots, and the surrounding embankments have been converted into driveways. above the reservoir a small plazuela of 1/2 hectare has been laid out with a space above it for a band-stand. the whole of the ground has been encircled with carriage drives, on which it is the intention to plant shade trees. the lay-out of this land also embraced the scheme for protecting the reservoir by draining the surface-water away to the irrigation ditches. comparison of south and obispado reservoirs. the two reservoirs are practically of the same capacity, the only difference being the level of the overflows in their relationship to the roof, which gives the obispado reservoir a slightly greater capacity. some comparative figures may be of interest, owing to the differences in type and construction. table 7 gives the comparative quantities of material in each reservoir proper, that is to say, exclusive of the valve-houses, lay-out of grounds, etc. table 7.--comparison of materials in south and obispado reservoirs. ==========================+===============================+============ | south reservoir. | _obispado reservoir._ +--------+-------------+--------+----------- | | quantities, | | quantities, | no. | in cubic | no. | in cubic | | meters. | | meters. --------------------------+--------+-------------+--------+----------- _earthwork:_ | | | | total excavation | ... | 34,000 | ... | 56,479 placed in embankment | ... | 31,500 | ... | 7,255 placed in spoil banks | ... | 2,500 | ... | 49,224 +--------+-------------+--------+----------- _concrete:_ | | | | columns (including | | | | foundations) | 135 | 1,240 | 356 | 543 primary beams | 135 | 440 | 374 | 462 secondary beams | 670 | 515 | 1,252 | 576 side-walls | ... | 1,255 | ... | 710 | | | | | square | | square | | meters.| | meters.| roof slab | 5,140 | 520 | 10,206 | 1,020 floor | 4,070 | 780 | 9,200 | 2,120 parapet walls | ... | 90 | ... | 165 +--------+-------------+--------+----------- total concrete | ... | 4,840 | ... | 5,596 +--------+-------------+--------+----------- | | pounds. | | pounds. reinforcing steel bars | ... | 387,000 | ... | 380,000 | | | | | | square | | square | | meters. | | meters. expanded metal in roofs, | | | | slabs, etc. | ... | 5,691 | ... | 10,490 ==========================+========+=============+========+============ the total cost of these reservoirs, including valve-houses, by-passes, and the length of supply pipe where the by-pass joins, and including all engineering expenses, etc., but exclusive of the cost of lands, planting, fencing, and special work in connection with the formation of parks, was as follows: south reservoir: 394,000 pesos, or 10,368 pesos per million liters. obispado reservoir: 375,000 pesos, or 9,375 pesos[7] per million liters. [7] mexican currency. these rates may be regarded as reasonable when taking into consideration the special difficulties of construction in mexico, and the high cost of all imported material, on which heavy duties are levied. the value of the materials alone in these reservoirs amounted to more than 70% of their total cost. analyses of estanzuela and san geronimo waters. table 8 shows analyses of the estanzuela and san geronimo waters, made in february, 1910, by messrs. ledoux, of new york city. the estanzuela sample was taken at the valve-house of the south reservoir, while that of san geronimo was taken in shaft no. 1 of the infiltration gallery when flowing at the rate of about 450 liters per sec. both waters are absolutely free from turbidity. table 8.--analyses of estanzuela and san geronimo waters. in parts per million. ==================================+================+=============== | | san geronimo | estanzuela. | infiltration | | gallery. ----------------------------------+----------------+-------------- total solid matter in solution | 209.00 | 305.00 organic and volatile matter | not weighable. | not weighable. | | analysis of solids: | | silica | 10.5 | 12.0 iron and alumina | traces. | traces. lime | 85.4 | 112.6 magnesia | 3.8 | 22.6 soda (na_{2}o) | 13.3 | 20.2 potash (k_{2}o) | 2.0 | 1.9 sulphuric acid | 24.4 | 11.5 chlorine | 2.0 | 2.8 +----------------+-------------- probable combination of bases & | | acid radicals in the solids: | | silica | 10.5 | 12.0 iron and alumina | traces. | traces. sodium chloride | 3.3 | 4.6 potassium sulphate | 3.7 | 3.5 sodium sulphate | 26.3 | 40.8 calcium sulphate | 13.3 | 22.1 calcium carbonate | 142.7 | 184.8 magnesium carbonate | 8.4 | 49.8 +----------------+-------------- | 208.2 | 317.6 | | nitrogen as free ammonia | 0.004 | 0.032 nitrogen as albuminoid ammonia | 0.006 | 0.022 nitrogen as nitrites (n_{2}o_{3}) | 0.002 | 0.002 nitrogen as nitrates (n_{2}o_{3}) | 0.100 | 1.85 total hardness (as caco_{3}) | 155.0 | 220.0 alkalinity (as caco_{3}) | 121.0 | 180.0 ==================================+================+=============== city water distribution system. [illustration: plate xix.--diagram of the main water pipes of monterrey.] the distribution system was begun in september, 1906, but the general lay-out of the mains was modified in july, 1907, in view of the division of the system into two services, for high and low pressure. plate xix shows in skeleton form the lines of the cast-iron mains. these are laid at the present time along routes containing houses (excluding wooden shacks) which can be served immediately. the distribution system is arranged to serve as follows: estanzuela supply 4,150 houses. san geronimo supply 8,600 " ------------- total 12,750 houses. this represents, at the present time, a division of the city of 32-1/2% for the estanzuela, and 67-1/2% for the san geronimo supply. of the area of the supply district north of santa catarina river, 57% will be supplied from san geronimo and 43% from estanzuela. the real development of the city, however, is northward in the area of the low-pressure supply. the static pressure over the city in the two sections varies as follows: estanzuela supply 85 to 50 lb. san geronimo supply 55 to 29 lb. the main supply pipe from the south reservoir is 61 cm. (24 in.) in internal diameter, and this size allows ample provision for future extensions. the supply pipe from the obispado reservoir is 76 cm. (30 in.) in internal diameter. on this main, in calle de cinco de mayo, at a distance of 320 m. from the reservoir, has been placed a 76-cm. (30-in.) venturi meter, the recording apparatus being in the house on the side of the road. both these supply pipes are carried well into the city, and from them the distribution mains are laid; these are 45.7 and 30 cm. (18 and 12 in.) in internal diameter, with intermediate sections of 15 and 10 cm. (6 in. and 4 in.). along calle de cinco de mayo, where the division between the two services takes place, two lines are laid, a 30-cm. for high pressure and a 38-cm. (15-in.) for the low pressure. a duplicate pipe, 30 cm. (12 in.) in diameter, is also laid in calle de dr. coss. on calle de alvarez the low-pressure pipe is 61 cm. (24 in.), and the high-pressure, 45.7 cm. (18 in.) in diameter. provision is also made for extending the range of the two services to other districts. practically every block is provided with gate-valves to cut off the supply in any direction. on the 76-cm. main, 61-cm. (24-in.) valves are used, and are connected by tapers to the pipe. on the 61-cm. mains, 45.7-cm. (18-in.) valves are used. the actual frictional loss by reducing the valve being small, this method permitted the use of valves of a more convenient size. on all the larger valves there are 15-cm. by-passes fitted with independent gate-valves. [illustration: fig. 15.--connection between high-and low-pressure areas and the intersection of cinco de mayo and alvarez streets.] scour-out pipes, 10 cm. (4 in.) and 15 cm. (6 in.) in diameter, are placed in various parts of the system, draining to the sewers. air-valves, both double and single, are also placed at high points in different parts of the system. _reducing valves._--at four points in the system the mains are arranged so that the supply can be interchangeable. fig. 15 shows the arrangement of the mains at the junction of cinco de mayo and alvarez streets, and is typical of the arrangement at the other points. each reducing valve is placed on a 30-cm. (12-in.) branch main between the two services. these valves adjust themselves automatically to the pressure required, after they have been properly regulated to the different pressures on either side. to allow repairs to be easily made, there are ordinary gate-valves at each end enclosed in the same pit. if necessary, as in case of fire, any part of the system can be changed into high pressure temporarily by closing the valves against the san geronimo supply. table 9 gives the length of the mains as laid, and the number of valves. table 9.--length of water mains. =========================+=====================+============= diameter: | | --------------+----------+ length, in meters. | number of centimeters. | inches. | | gate-valves. --------------+----------+---------------------+------------ 10.2 | 4 | 49,831.68 | 677 15.2 | 6 | 31,918.31 | 306 30.5 | 12 | 14,461.31 | 117 38.1 | 15 | 1,661.98 | 11 45.7 | 18 | 4,522.61 | 5 61.0 | 24 | 2,826.54 | 10 76.2 | 30 | 1,454.40 | --------------+----------+---------------------+------------ totals | 106,676.83 | 1,126 =========================+=====================+============= the pipes were all cast according to the british standard specification, in 3.65-m. (12-ft.) lengths, and were supplied by messrs. d. y. stewart and company, and messrs. dick, kerr and company, of kilmarnock and london. the valves were all of standard design, faced with gun-metal, and were supplied by messrs. glenfield and kennedy, limited, of kilmarnock, scotland. in the distribution system it is proposed to provide 200 fire-hydrants, by arrangement with the municipality, but only a few of these have been placed. the general type is a double hydrant for two 63.5-mm. (2-1/2-in.) streams. these are to be placed at the corner of every block in the business portion of the city; single-way hydrants will be used in the residential districts. _laying cast-iron pipes._--table 10 has been prepared to show what can be accomplished with mexican labor in laying pipes. in this kind of work the labor was particularly efficient; after the gangs were once drilled into shape, the work proceeded systematically, and at very good speed. all the pipes, after being laid, were tested to 150 lb. per sq. in. in the presence of the technical inspector. table 11 gives the details of the excavation, the material, and the average cost, of laying about 106.6 km. of pipes. _house connections._--the ordinary house connections, which are of 19-mm. (3/4-in.) galvanized-steel pipe, are connected to the mains by lead goosenecks and brass corporation cocks. the company's obligation under the concession extended to the edge of the sidewalk, and at this point curb-boxes, chiefly of the hays pattern, were placed; but, subsequently, owing to the metering of every house service in the city, the control of the company extended to the meter, which, as a rule, is placed immediately inside of the house. owing to the rapid deterioration of the house service pipes in some districts of the northern part of the city, where the soil is formed of decaying organic matter, it has been decided to use lead pipe entirely from the main to the meter. _damage due to floods._--during the night of august 27th, the main 61-cm. pipe, under the river bed of santa catarina, at the point where the main entered the city, was destroyed for a distance of 130 m., due to the scouring away of a whole block of city property. the venturi meter register chart at the south reservoir showed that the break occurred a few minutes before midnight. the location of this pipe is shown by fig. 5; its broken end was in proximity to an old bridge pier. fortunately, at the time of the flood, the obispado reservoir works were completed, and the whole city was supplied with water from san geronimo within 48 hours. as only about 1,500 services had then been connected, this delay was not serious; in fact, in the lower part of the city, the water in the mains was sufficient until the san geronimo supply could be connected. to make a temporary connection to conduct the high-pressure water to the city, a 15-cm. steel pipe was placed above ground, on the line of the main, for a distance of 100 m. this pipe was supported by a cable, 30 mm. in diameter, and by timber trestles. by limiting the supply district, this pipe was of sufficient capacity to serve until the large main could be safely restored. table 10.--cost of laying and jointing cast-iron pipes, excluding lowering and testing. +--------------+----------+----------------------------------------+ | | | 76 cm. (30 in.) | | | +-------+------------+--------+----------+ | employees. | rate for | total | total cost | no. of | cost per | | | 10-hour | no. | of labor. | pipes | linear | | | day. | men. | pesos. | laid. | meter. | | | pesos. | | | | pesos. | +--------------+----------+-------+------------+--------+----------+ | foreman | 4.50 | 1 | 4.50 | ... | ... | | caulkers | 3.00 | 4 | 12.00 | ... | ... | | lead pourers | 2.00 | 2 | 4.00 | ... | ... | | lead melter | 1.50 | 1 | 1.50 | 20 | 0.498 | | pipe cutter | 2.00 | 1 | 2.00 | ... | ... | | peons | 1.00 | 12 | 12.00 | ... | ... | | water boy | 0.50 | 1 | 0.50 | ... | ... | | | | | | | | | | ... | 22 | 36.50 | ... | ... | +--------------+----------+-------+------------+--------+----------+ | | | 61 cm. (24 in.) | | | +-------+------------+--------+----------+ | employees. | rate for | total | total cost | no. of | cost per | | | 10-hour | no. | of labor. | pipes | linear | | | day. | men. | pesos. | laid. | meter. | | | pesos. | | | | pesos. | +--------------+----------+-------+------------+--------+----------+ | foreman | 4.50 | 1 | 4.50 | ... | ... | | caulkers | 3.00 | 5 | 15.00 | ... | ... | | lead pourers | 2.00 | 2 | 4.00 | ... | ... | | lead melter | 1.50 | 1 | 1.50 | 25 | 0.410 | | pipe cutter | 2.00 | 1 | 2.00 | ... | ... | | peons | 1.00 | 10 | 10.00 | ... | ... | | water boy | 0.50 | 1 | 0.50 | ... | ... | | | | | | | | | | ... | 21 | 37.50 | ... | ... | +--------------+----------+-------+------------+--------+----------+ | | | 50 cm. (20 in.) | | | +-------+------------+--------+----------+ | | rate for | total | total cost | no. of | cost per | | employees. | 10-hour | no. | of labor. | pipes | linear | | | day. | men. | pesos. | laid. | meter. | | | pesos. | | | | pesos. | +--------------+----------+-------+------------+--------+----------+ | foreman | 4.50 | 1 | 4.50 | ... | ... | | caulkers | 3.00 | 4 | 12.00 | ... | ... | | lead pourers | 2.00 | 2 | 4.00 | ... | ... | | lead melter | 1.50 | 1 | 1.50 | 35 | 0.287 | | pipe cutter | 2.00 | 1 | 2.00 | ... | ... | | peons | 1.00 | 12 | 12.00 | ... | ... | | water boy | 0.50 | 1 | 0.50 | ... | ... | | | | | | | | | | | 22 | 36.50 | ... | ... | +--------------+----------+-------+------------+--------+----------+ | | | 45.7 cm. (18 in.) | | | +-------+------------+--------+----------+ | | rate for | total | total cost | no. of | cost per | | employees. | 10-hour | no. | of labor. | pipes | linear | | | day. | men. | pesos. | laid. | meter. | | | pesos. | | | | pesos. | +--------------+----------+-------+------------+--------+----------+ | foreman | 4.50 | 1 | 4.50 | ... | ... | | caulkers | 3.00 | 4 | 12.00 | ... | ... | | lead pourers | 2.00 | 2 | 4.00 | ... | ... | | lead melter | 1.50 | 1 | 1.50 | 40 | 0.221 | | pipe cutter | 2.00 | 1 | 2.00 | ... | ... | | peons | 1.00 | 8 | 8.00 | ... | ... | | water boy | 0.50 | 1 | 0.50 | ... | ... | | | | | | | | | | | 18 | 32.50 | ... | ... | +--------------+----------+-------+------------+--------+----------+ | | | 38 cm. (15 in.) | | | +-------+------------+--------+----------+ | | rate for | total | total cost | no. of | cost per | | employees. | 10-hour | no. | of labor. | pipes | linear | | | day. | men. | pesos. | laid. | meter. | | | pesos. | | | | pesos. | +--------------+----------+-------+------------+--------+----------+ | foreman | 4.50 | 1 | 4.50 | ... | ... | | caulkers | 3.00 | 4 | 12.00 | ... | ... | | lead pourers | 2.00 | 2 | 4.00 | ... | ... | | lead melter | 1.50 | 1 | 1.50 | 45 | 0.196 | | pipe cutter | 2.00 | 1 | 2.00 | ... | ... | | peons | 1.00 | 8 | 8.00 | ... | ... | | water boy | 0.50 | 1 | 0.50 | ... | ... | | | | | | | | | | | 18 | 32.50 | ... | ... | +--------------+----------+-------+------------+-------------------+ | | | 30.5 cm. (12 in.) | | | +-------+------------+--------+----------+ | | rate for | total | total cost | no. of | cost per | | employees. | 10-hour | no. | of labor. | pipes | linear | | | day. | men. | pesos. | laid. | meter. | | | pesos. | | | | pesos. | +--------------+----------+-------+------------+--------+----------+ | foreman | 4.50 | 1 | 4.50 | ... | ... | | caulkers | 3.00 | 4 | 12.00 | ... | ... | | lead pourers | 2.00 | 2 | 4.00 | ... | ... | | lead melter | 1.50 | 1 | 1.50 | 60 | 0.147 | | pipe cutter | 2.00 | 1 | 2.00 | ... | ... | | peons | 1.00 | 8 | 8.00 | ... | ... | | water boy | 0.50 | 1 | 0.50 | ... | ... | | | | | | | | | | | 18 | 32.50 | ... | ... | +--------------+----------+-------+------------+--------+----------+ | | | 15 cm. (6 in.) | | | +-------+------------+--------+----------+ | employees. | rate for | total | total cost | no. of | cost per | | | 10-hour | no. | of labor. | pipes | linear | | | day. | men. | pesos. | laid. | meter. | | | pesos. | | | | pesos. | +--------------+----------+-------+------------+--------+----------+ | foreman | 4.50 | 1 | 4.50 | ... | ... | | caulkers | 3.00 | 4 | 12.00 | ... | ... | | lead pourers | 2.00 | 2 | 4.00 | ... | ... | | lead melter | 1.50 | 1 | 1.50 | 100 | 0.082 | | pipe cutter | 2.00 | 1 | 2.00 | ... | ... | | peons | 1.00 | 6 | 6.00 | ... | ... | | water boy | 0.50 | 1 | 0.50 | ... | ... | | | | | | | | | | | 16 | 30.50 | ... | ... | +--------------+----------+-------+------------+--------+----------+ | | | 10 cm. (4 in.) | | | +-------+------------+--------+----------+ | employees. | rate for | total | total cost | no. of | cost per | | | 10-hour | no. | of labor. | pipes | linear | | | day. | men. | pesos. | laid. | meter. | | | pesos. | | | | pesos. | +--------------+----------+-------+------------+--------+----------+ | foreman | 4.50 | 1 | 4.50 | ... | ... | | caulkers | 3.00 | 4 | 12.00 | ... | ... | | lead pourers | 2.00 | 2 | 4.00 | ... | ... | | lead melter | 1.50 | 1 | 1.50 | 150 | 0.0574 | | pipe cutter | 2.00 | 1 | 2.00 | ... | ... | | peons | 1.00 | 6 | 6.00 | ... | ... | | water boy | 0.50 | 1 | 0.50 | ... | ... | | | | | | | | | | | 16 | 30.50 | ... | ... | +--------------+----------+-------+------------+--------+----------+ table 11.--cast-iron water pipes.--cost of materials and laying at monterrey. materials per standard length of pipe . key: cm = centimeter in = inch mm = millimeter kg = kilogram m = linear meter +-----------+------+-------+--------+-------------+--------+--------+-------+ | pipe | |weight |cost/ | lead | oakum |charcoal| total | | diameter |thick-| of |piece +------+------+--------+--------+ ma | +------+----+ ness | pipe |fob mon-|weight| cost | cost | cost |terial | | | | | |terrey | | | | | cost | | cm | in | mm | kg | pesos | kg |pesos | pesos | pesos | per m | +------+----+------+-------+--------+------+------+--------+--------+-------+ | 10 | 4 | 10.3 | 109 | 11.65 | 2.0 | 0.37 | 0.025 | 0.0525 | 3.30 | | 15 | 6 | 11.1 | 163 | 15.74 | 3.7 | 0.67 | 0.0675 | 0.065 | 4.51 | | 30.5 | 12 | 15.8 | 463 | 76.50 | 7.9 | 1.44 | 0.1225 | 0.1 | 21.35 | | 38 | 15 | 17.4 | 680 | 79.36 | 10.6 | 1.94 | 0.175 | 0.12 | 22.30 | | 45.7 | 18 | 19.0 | 871 | 90.28 | 13.4 | 2.42 | 0.2375 | 0.1375 | 25.42 | | 61 | 24 | 22.2 | 1,261 | 117.60 | 18.8 | 3.42 | 0.335 | 0.175 | 33.20 | | 76 | 30 | 25.4 | 1,946 | 199.05 | 24.5 | 4.42 | 0.44 | 0.2125 | 55.77 | +------+----+------+-------+--------+------+------+--------+--------+-------+ labor. key: cm = centimeter, in = inch, m = meter +-----------+------+------+------+------+-------+-------+--- | | | | | | |total | | diameter | | | cubic| cost |back |cost, | | of pipe: | width|depth |meters| of |filling|exca | | | of | | per |exca|and re-|vation | +------+----+trench| |linear|vation|moving |back | continues | | | | | meter| per |surplus|filling| | cm | in | m | m | |lin. m|pesos |etc. | | | | | | | | |pesos | +------+----+------+------+------+------+-------+-------+--- | 10 | 4 | 0.55 | 0.90 | 0.50 | 0.60 | 0.18 | 0.78 | | 15 | 6 | 0.60 | 1.00 | 0.60 | 0.72 | 0.22 | 0.94 | | 30.5 | 12 | 0.65 | 1.20 | 0.78 | 0.94 | 0.29 | 1.23 | | 38 | 15 | 0.70 | 1.30 | 0.91 | 1.10 | 0.34 | 1.44 | below | 45.7 | 18 | 0.80 | 1.40 | 1.12 | 1.34 | 0.41 | 1.75 | | 61 | 24 | 1.00 | 1.50 | 1.50 | 1.80 | 0.55 | 2.35 | | 76 | 30 | 1.10 | 1.60 | 1.76 | 2.11 | 0.65 | 2.76 | +------+----+------+------+------+------+-------+-------+--- --+----------------+--------+--------+--------+ | hauling per | cost | total | total | | | of |hauling |excava| | linear meter | laying | and |tion and| | | per |laying |laying, | +--------+-------+ linear | per |labor, | | haul | misc. | meter |linear |complete| | ing | pesos | | meter | | | pesos | | pesos | pesos | pesos | --+--------+-------+--------+--------+--------+ | 0.0275 | 0.005 | 0.06 | 0.0925 | 0.8725 | | 0.45 | 0.005 | 0.825 | 0.1325 | 1.0725 | | 0.18 | 0.0075| 0.1475 | 0.335 | 1.565 | | 0.2725 | 0.01 | 0.19 | 0.4775 | 1.9125 | | 0.2725 | 0.01 | 0.245 | 0.5275 | 2.2775 | | 0.825 | 0.08 | 0.41 | 1.315 | 3.665 | | 0.83 | 0.10 | 0.53 | 1.46 | 4.22 | --+--------+-------+--------+--------+--------+ note.--the above costs of earthwork are based on the following rates and percentages over the whole city: earth, per cubic meter | 0.35 pesos | 50% soft sillar | 0.75 " | 20% hard sillar | 1.50 " | 20% rock (chiefly conglomerate) | 4.00 " | 10% summary of table 11. +------------------------+-------------+------------+------------+ | diameter | total labor | materials. | total cost | | of pipe : | cost. | pesos. | per linear | +--------------+---------+ in pesos. | | meter, in | | centimeters. | inches. | | | pesos. | +--------------+---------+-------------+------------+------------+ | 10 | 4 | 0.8725 | 3.30 | 4.1725 | | 15 | 6 | 1.0725 | 4.51 | 5.5825 | | 30.5 | 12 | 1.565 | 21.35 | 22.915 | | 38 | 15 | 1.9125 | 22.30 | 24.2125 | | 45.7 | 18 | 2.2775 | 25.42 | 27.6975 | | 61 | 24 | 3.665 | 33.20 | 36.865 | | 76 | 30 | 4.22 | 55.77 | 59.99 | +--------------+---------+-------------+------------+------------+ the flood destroyed about 1,200 houses in the neighborhood of the river. in a number of blocks the smaller mains were scoured away, but considerable salvage was done afterward, and, as it is the intention of the authorities not to permit rebuilding along the flood-path of the river, these mains do not require reconstruction. main sewerage system. the company's obligations, as far as drainage is concerned, were limited to the removal and disposal of sewage, no provision being required for storm-water, which is allowed to find its way to the natural watercourses. apart from that fact, however, the best system for a city like monterrey, where rainfall for many months at a time is very scarce, is the strictly "separate system." in the design advantage was taken of the natural topography of the drainage district, which is almost an ideal one for a gravitation system of sewers, the general fall in all directions being northeast; it was also in this direction that the best available land could be obtained for disposal purposes. [illustration: plate xx.--diagram of the main sewers of monterrey.] plate xx shows in skeleton form the general lay-out of the sewers. two drainage districts are arranged, divided by calle de washington, which may be regarded as practically the center of the city, and each of these districts has an independent main collector connecting to the outfall sewer at the northeast extremity of the city. the system has been designed so that extensions may be made and may cover any part within the city limits; the main collectors are large enough for the whole area when fully built up. the sewers are designed on a very liberal basis, namely, on the assumption that when flowing half full the quantity to be dealt with will be 380 liters per capita per day, with a maximum rate of flow of 200 per cent. it was assumed that each house would be occupied by 7 persons and have a frontage of 12-1/2 m. the minimum velocities in the sewers, when running full, vary between 0.91 and 1.5 m. per sec., with the exception of a few blocks. the minimum size adopted was 24.3 cm. (8 in.) in internal diameter. the sewers of diameters between 24.3 and 50 cm., are 0.91 m. (36 in.) long, and are of salt-glazed vitrified clay, imported from san antonio, tex. table 12 gives the details of the length of the various sewers laid. table 12.--length of sewers. +----------+------------------------------------------+-----------+ |diameter: | | | +-----+----+ kind. | length, | | cm | in.| | in meters.| +-----+----+------------------------------------------+-----------+ |24.3 | 8 | fire-clay | 38,332.85 | |25.4 | 10 | " | 16,400.69 | |30.5 | 12 | " | 7,953.15 | |38.1 | 15 | " | 4,850.56 | |45.7 | 18 | " | 2,023.40 | |50.8 | 20 | " | 1,450.53 | |55.9 | 22 | reinforced concrete tubes, 6.9 cm. thick | 3,134.20 | |61.0 | 25 | " " " 7.6 " " | 357.40 | |68.6 | 27 | brick and concrete | 484.05 | |76.2 | 30 | " " " | 662.69 | | | | | | | | | total | 75,649.15 | +-----+----+------------------------------------------+-----------+ the greater number of the manholes are of brickwork, 23 cm. thick, and have concrete inverts. they have a diameter of 1.2 m., which is reduced to 0.61 m. at the top, and each is provided with a heavy cast-iron frame and closed cover weighing about 190 kg. there are 521 manholes, and they are placed at every block and on long lines about 80 m. apart. [illustration: fig. 16.--standard 300-gal. flush tanks.] the sewers are flushed with 15-cm. (6-in.) automatic flushing siphons of the miller pattern with 20-cm. (8-in.) discharge pipes. there are 278 of these siphons, and they are placed in flush-tanks (fig. 16) built of brickwork and plastered with 1:1 cement mortar. their capacity varies from 800 to 1,200 liters, and they discharge from 22-1/2 to 28-1/2 liters per sec. they are timed to flush once in 24 hours. the system is at present ventilated by 23-cm. (9-in.) steel ventilating columns (fig. 16), with ornamental cast-iron bases. there are 220 of these columns. most of them are 7.85 m. above the level of the edge of the sidewalk, and are connected to special 15-cm. branch pipes leading from the sewer on the outside of the flush-tanks. in the center of the city they are provided with extension lengths, giving a total height of 12 m. table 13 gives the particulars of the average distributed cost of laying the 75.6 km. of sewers. table 13.--average cost, per linear meter, for 75.6 km. of sewers, for materials and labor complete. +----------+-----------+--------+-----------------------------+--------+ | | internal |cost of | earthwork and labor: | total | | | diameter | mater|-------+------------+--------| cost of| | | of | ials | | cost of |cost of | sewer | | | sewers. |includ|average| excavation,|labor |complete| |kind of +------+----+ ing | depth | including | in | per | | sewer. | | |10-cm. | of | back |laying | linear | | | | |(4-in.) | sewer | filling, |(includ-| meter. | | | cm. | in.|branches| | removing | ing | | | | | |every | m. | surplus, |hauling,| | | | | |4-1/2 m.| | etc. | etc.). | | | | | |pesos. | | pesos. | pesos. | | +----------+------+----+--------+-------+------------+--------+--------+ |fire-clay | 24.3 | 8 | 2.00 | 2.10 | 3.46 | 0.21 | 5.67 | | " | 25.4 | 10 | 2.78 | 2.25 | 3.97 | 0.2625 | 7.0125 | | " | 30.5 | 12 | 3.64 | 2.50 | 4.705 | 0.305 | 8.65 | | " | 38.1 | 15 | 6.14 | 2.75 | 5.50 | 0.4375 |12.0775 | | " | 45.7 | 18 | 8.80 | 3.00 | 6.745 | 0.645 |16.19 | | " | 50.8 | 20 | 11.30 | 3.50 | 8.275 | 0.815 |20.39 | |concrete | 55.9 | 22 | 5.93 | 3.50 | 9.19 | 1.325 |16.445 | | " | 61.0 | 25 | 7.30 | 3.75 | 11.245 | 1.685 |20.23 | |one brick}| | | | | | | | |thick on }| 68.6 | 27 | 7.17 | 3.75 | 11.735 | 3.93 |22.835 | |concrete }| 76.2 | 30 | 7.925 | 4.00 | 14.53 | 4.515 |26.97 | |founda }| | | | | | | | |tions }| | | | | | | | +----------+------+----+--------+-------+------------+--------+--------+ [illustration: fig. 17.--sketch showing disconnecting trap on house drain.] the house connections are chiefly of 10-cm. (4-in.) pipes, laid on a minimum gradient of 2-1/2%, from oblique branches on the sewer to siphon intercepting traps near the house, as shown by fig. 17. from this trap a 10-cm. fire-clay inspection pipe is carried up and capped at the sidewalk level with a cast-iron box having a locked cover. from this inspection pipe a branch is connected to a cast-iron fresh-air inlet, in most cases set in the wall of the house, the inlet being 30 cm. above the level of the pavement. _effect of the flood on sewers._--the flood of august 27th and 28th, 1909, partly destroyed one of the main collectors, which was laid along the banks of the river and encased in concrete. this has now been relaid farther north, and out of the way of any future floods. the total length of the new sewers replacing those damaged amounts to 1200 m., and they vary in internal diameter from 20 to 55.9 cm. (8 to 22 in.). main outfall sewer. the direction of the main outfall sewer was determined after a thorough study of all the available land lying to the north and northeast of the city, as it was the intention of the company to utilize for irrigation purposes the sewage and any surplus waters that might be developed. the best available site was found to be about 12 km. north of the city, a little northwest of the village of san nicolas de los garzas, as shown on plate ii. the long length of outfall required was justified by the cheap cost of the land and its excellent character for sewage irrigation. the sewer was designed for a capacity of 90,000,000 liters a day (36.76 cu. ft. per sec.) in order to allow for conveying surplus waters as well as sewage. [illustration: plate xxii.--outfall sewer: plan of ground showing sewer; also details of various sections.] the outfall intercepts the two main branches of the city sewers at calle de allende and calle de tapia, and its total length is approximately 11,900 m. the chief type adopted is shown on plate xxii. it is formed with an invert of radial bricks laid in 1:2 cement mortar, on a foundation of 1:3:5 concrete approximately 7 cm. thick. as the ground was chiefly in hard sillar, only a little concrete was required to mould the bottom to the correct shape. the arch was formed of special radial bricks, 15 cm. (6 in.) deep, laid in cement mortar. these bricks were adopted in preference to concrete, owing to the heavy cost of sand and rock, due to the long haul, and for the purpose of obtaining rapid work. plate xxi shows the sewer arch, and one of the ventilating columns and manholes. the bricks were obtained from the local brick plant, and form a very satisfactory material for sewers, being well burnt, thoroughly hard, and absorbing not more than 7-1/2% of their weight of water. the contract prices for the labor on the brickwork were 1.25 pesos per sq. m., and 1.38 pesos for the arch. [illustration: plate xxi, fig. 1.--view of arch, outfall sewer.] [illustration: plate xxi, fig. 2.--ventilating column and manhole, outfall sewer.] the general route of the sewer is very direct, long straight lines of several kilometers being possible, and these were joined by curves of approximately 30 m. radius. the gradient of the sewer invert is 0.2% (1 in 500) which is approximately the general fall of the ground northward from monterrey. the total quantity of excavation was as follows: no. 1, soft earth 8,960 cu. m. no. 2, sillar 18,492 " " no. 3, conglomerate rock 9,822 " " ----- total 37,274 cu. m. the contract prices for this excavation were: for no. 1, 32 cents; no. 2, 85 cents; and no. 3, 2.17 pesos per cu. m. all the excavation was in perfectly dry ground. where the sewer was partly out of the ground it had a foundation of concrete, 1.75 m. wide, from 15 to 23 cm. thick, below the bottom of the brickwork, and carried up to the springing of the arch, and a well-tamped embankment, with slopes of 1-1/2 to 1, to protect the sewer to a height of 30 cm. (12 in.) above the arch. for 342 m. at the monterrey end of the line, the sewer was constructed in tunnel, from, the open end and from two intermediate shafts. the tunnel throughout was in sillar, and the contract price for excavation was 24.50 pesos per lin. m. this work was done without timbering of any kind, except at the shaft lengths. plate xxii shows the lining of the tunnel, which was of concrete with a brick invert. at four places the sewer passes under main railway tracks, which at these points were carried on steel girders supported on concrete abutments, the sewer being carried under the tracks in the ordinary way. _bridges._--at three points the sewer was carried over arroyos on reinforced concrete girders. no. 1, at station 5,600, consisted of four 10-m. spans; no. 2, at station 8,365, over the estanscia arroyo, consisted of nine 10-m. spans; and no. 3, at station 8,960, over the topo chico arroyo, consisted of three 10-m. spans. one of these bridges is shown on plate xxiii. they were designed as two parallel continuous girders with connecting top and bottom slabs. the concrete for the girders was a 1:2-1/2:3-1/2 mixture, the sand being from the crusher and the rock gauged to pass a 19-mm. (3/4-in.) screen. the inside was rendered with a coat of 1:1 cement mortar, 7 mm. thick, for water-tightness. [illustration: plate xxiii, fig. 1.--forms for main girders, estanscia bridge, outfall sewer.] [illustration: plate xxiii, fig. 2.--view of estanscia bridge, completed.] the piers of the estanscia bridge (plate xxiii) were carried down through soft earth to a stiff clay from 4-1/2 to 6 m. below the surface, and the foundations were spread so that the pressure would not exceed 1 ton per sq. ft. the ends of the bridges were protected by rubble wing-walls supporting the embankment over the sewer. a 1:3:5 concrete was used for the upper part of the piers, and the lower part was of the same mixture with 30% of large boulders. there are 70 manholes (fig. 19) along the line of the sewer, and they vary from 150 to 230 m. apart. the sewer is ventilated with 30 concrete towers (fig. 18, and fig. 2, plate xxi), 2.9 m. high, having 20-cm. (8-in.) shafts. [illustration: fig. 18.--details of ventilators on outfall sewer.] [illustration: fig. 19.--details of manholes on outfall sewer.] the works for the outfall sewer were carried out satisfactorily under a contract with mr. john phillips, of mexico city, the company supplying the greater part of the materials. the work was begun on march 16th, and finished on november 12th, 1908. sewage disposal works and irrigation lands. for the purpose of disposing of the sewage and using it profitably, the company purchased 909 hectares (2,246 acres) of land from the community of san nicolas de los garzas, the outfall sewer being carried to the southwestern boundary of the land acquired. this area has a general fall in all directions to the northeastern boundary, with a gradual fall of about 25 m. across the diagonal of the land. the area purchased was practically virgin land, only small portions having been cultivated. the greater part was covered with a growth of mezquite trees and small shrubs. the quality of the land is excellent, if properly irrigated, and capable of yielding abundant crops of every description. the limits of this land are shown on plate ii. _sewage purification tanks._--for the purpose of obtaining a satisfactory effluent to discharge on the land without causing nuisance, the company built a system of detritus chambers and liquefying tanks at the end of the outfall sewer. one difficulty to be faced, in designing these works, was the fact that there were no data regarding the probable quantity of dry-weather sewage, nor any particulars as to its general character; there was also the probability that the outfall sewer would have to carry large quantities of surplus water. therefore, the system was designed so as to be capable of extension if necessary, and the sizes of the various tanks were limited at present, because of the septic processes which would be set up in the long length of outfall sewer. the tanks were designed to deal with 10,000,000 liters of sewage proper per day, and the channels, etc., were proportioned to take the full flow of the sewer if necessary. provision was also made for discharging large volumes of surplus water directly on the land, independent of the tanks. to do this a by-pass was taken from the sewer a short distance before reaching the site of the tanks. by properly timing the flow, arrangements could be made to discharge these waters in the early hours of the morning, by allowing the scour-pipes in the distribution system to be opened at night when the domestic sewage flow was at its minimum. as the area of land available is very great, the degree of purification in the tanks was relatively unimportant; the object to be obtained consisted chiefly in distributing on the land an effluent which would be innocuous and clear. the general design of the works is shown on plate xxiv, and they consist essentially of a screen chamber, duplicate detritus tanks, and three liquefying tanks. there is also a sludge-pit 629 m. from the tanks. [illustration: plate xxiv.--sewage disposal works at san nicolas de los garzas; general plan of detritus and liquefying tanks, with details of the latter.] _screen chamber and detritus tanks._--enlarged details of the screen chamber are shown on plate xxv. the invert, where the sewer enters the screen chamber, is 489.45 m. above datum. this chamber has duplicate screens which are fully detailed on plate xxx. for cleaning purposes the screens are raised by a steel-framed head-gear, which is arranged so that they may be lowered to a small traveling bogie, out of the way of the screen chamber. [illustration: plate xxv.--sewage disposal works at san nicolas de los garzas. details of detritus chambers and inlet channels.] [illustration: plate xxvi.--sewage disposal works at san nicolas de los garzas detritus and liquefying tanks; details of distributing channels.] [illustration: plate xxx.--sewage disposal works at san nicolas de los garzas. details of screening apparatus.] from the screen chamber there are two main channels, 1.22 m. wide, branching to the two concrete detritus chambers. each channel has a square penstock, so that the sewage can be diverted into either chamber when necessary. the detritus chambers are octagonal in plan, 4 m. in diameter, and each is provided with an outlet weir 1.50 m. wide. at the weir level the chambers have a depth of 1.75 m., with drainage channels below that level. the coping is 1 m. above the outlet weir of the detritus tanks. to drain off these chambers, each has a scour-out pipe, 30 cm. in diameter, controlled from valves with spindles carried above the coping level. each of these pipes is connected to a central chamber, and leads to a 56-cm. (22-in.) sludge-pipe. the chambers as designed are of smaller capacity than those usually provided, but, as all surface water is strictly excluded from the sewerage system, the quantity of detritus reaching the chambers may be small. the velocity through them when both are in use will be approximately 0.082 m. (0.27 ft.) per sec. from these chambers the sewage is carried to the three liquefying tanks by a main channel, 11.5 m. long and 1.50 m. wide. [illustration: plate xxvii, fig. 1.--cast concrete beams being placed in position, liquefying tanks.] [illustration: plate xxvii, fig. 2.--inlet weirs to liquefying tanks, during construction.] [illustration: plate xxviii, fig. 1.--view of liquefying tanks, from inlet end.] the tanks are of concrete and have reinforced concrete roofs. each is 66 m. long and 6 m. wide; the minimum depth for the sewage is 1.50 m. at the outlet end, and 2.25 m. at the inlet, increasing to a maximum depth of 2.75 m. at the lowest depth at the scour-out channel. their combined capacity is 2,500,000 liters, which is equivalent to 6 hours' flow of the quantity of sewage for which they were designed. the sewage passes from the main channel, through penstock-valves which control the flow, into one or the other of the tanks. from these valve openings it flows over concrete weirs, 5 m. long, and is deflected to the bottom of the tank by a reinforced concrete scum-plate, extending across each tank, with a clearance of 15 cm. at each end. this scum-plate is 1.5 m. deep and 10 cm. thick, and is placed 40 cm. from the end walls. [illustration: plate xxix.--sewage disposal works at san nicolas de los garzas; details of outlet channels and weir box.] the details of the concrete division and outside walls are shown on plate xxix. the floor was constructed in two layers, and its surface is divided into 6 channels formed by small walls, 20 cm. wide and 15 cm. deep, the object of these channels being to facilitate the cleaning of the floor by scouring it out to a specially arranged channel at the deepest point of the tank, near the inlet end. each scour-out channel has a 30-cm. (12-in.) gate-valve, controlled from the roof of the tank, the three scour-pipes meeting in a concrete chamber outside of the tanks, from which a 56-cm. (22-in.) concrete pipe discharges the contents of the tanks to the sludge-pit during cleaning operations. the velocity through the tanks, when they are used in combination, is 0.0253 m. (0.083 ft.) per sec., the tanks being made as long as economically possible, in order to obtain this low velocity and thus permit the proper sedimentation of the suspended matters. the roof of each tank is 1 m. above the weir level. each tank has four ventilating columns, 3.7 m. high and 30 cm. in diameter, vitrified clay pipes, with an exterior casing of contrete, being used for the shafts. the roof is enclosed within parapet walls, and is covered with a layer of earth 25 cm. thick. the outlet channel from the tanks leads to a measuring chamber, 3 m. square, as shown on plate xxix. this chamber is fitted with penstocks, 1.83 m. wide, and measuring weirs. from this chamber the sewage is delivered to two main irrigation ditches, which distribute the sewage in two directions, one northward and the other to the western extremity of the lands. _construction of tanks._--the excavation for the tanks was in soft earth for a depth of 1-1/2 m.; the lower depths were in a firm foundation of sillar and calcareous clay. the total excavation in the tanks, channels, etc., was 8,335 cu. m., and the actual cost was 45-3/4 cents per cu. m. to facilitate the construction, about six-tenths of the concrete beams were cast as single monoliths and placed in position by sliding them across the tanks on temporary timbers. the remainder of the beams, the roof, and the slab were placed in position in the ordinary way with timber forms. the total quantity of concrete placed was 1,360 cu. m. a 1:2-1/2:4-1/2 concrete was used for the walls, channels, etc., and a 1:2:3 mixture for the roof slab and beams. table 14 gives the average cost per cubic meter for all the concrete work. table 14.--average cost per cubic meter for concrete in tanks. +-----------------------------------------+-----------+-----------+ | | pesos per | pesos per | | | cubic | cubic | | | meter. | meter. | +-----------------------------------------+-----------+-----------+ | labor : | | | | mixing and placing | 5.20 | | | carpenter work in forms, framing, etc. | 4.20 | | | | _____ | | | total labor cost | | 9.40 | | | | | | materials : | | | | screened gravel | 4.04 | | | sand (from neighboring arroyo) | 4.98 | | | cement (including hauling) | 15.19 | | | lumber, nails, and other supplies | 1.90 | 26.11 | +-----------------------------------------+-----------+-----------+ | total cost of concrete per cubic meter 35.51 | +-----------------------------------------------------------------+ _sludge-pit._--the sludge-pit, used when cleaning out the tanks, is carried 639 m. northward, far enough to get the available fall to drain the bottom of the detritus chambers and liquefying tanks. the drainage pipe was formed of 56-cm. (22-in.) concrete tubes. the sludge-pit is merely an excavation in the earth 20 m. square and 2 m. deep, the sides having a slope of 1-1/2 to 1. an overflow drains the pit to an irrigation ditch, the solid matter being allowed to settle and the liquid to drain off. from time to time it is proposed to dig out the solids and plow them into the land. _general._--to the east of the tanks a 3-roomed house has been built for the inspector. in order to provide a good supply of water for cleaning operations, a well 22 m. deep has been sunk and is fitted with pumps operated by an eclipse windmill, 4 m. in diameter, on a tower 22 m. high, which delivers the pump water to a circular wooden tank of 20,000 liters capacity. the work in connection with the purification tanks was carried out by the company's own staff; it was begun on september 10th, 1908, and practically completed by the first week in january, 1909. at the time of writing, the tanks have to deal with the sewage from a population of only 10,000 persons, as only from 15 to 20% of the connections have been made. the sewage, therefore, has been diluted with several times its volume of surplus water, and the necessary scum on the top of the sewage in the tanks has not yet assumed the usual thick matty condition observed in most systems. as there are no available means in monterrey of having proper determinations made of the degree of purification which takes place in the passage of the sewage through the liquefying tanks, a few simple tests have been made. these tests were limited to the determination of the amount of oxygen absorbed in 4 hours, and show a purification of 50% in passing from the detritus chambers to the outlet. the sewage, although very black and full of suspended matter as it enters the tanks, leaves them in a very clarified condition. of the total area of land acquired by the company, 904 hectares (2,234 acres) have been leased to the monterrey railway, light, and power company, for 99 years, the water-works company reserving 5 hectares (12 acres) absolutely for future extensions of the sewage works. by giving 12 months' notice, the company also reserves the right to utilize any part of 145 hectares (358 acres) near the tanks, should it be required at any time in the future for sewage purification purposes. quality of and rates for labor. all the work was practically under the direction of english-speaking superintendents and general foremen. for the ordinary skilled and low-skilled labor, mexicans were employed exclusively, and, on the work, which was quite new to them, they proved entirely efficient and satisfactory; throughout the work, on which at some periods between 2,000 and 3,000 men were employed, chiefly under the company's direct administration, they were very tractable and willing to do their best, and no trouble was experienced at any time. the mexican "peon," and also the ordinary skilled workman in the north of mexico, is intelligent, and is excellent for purely routine work, but he is not adaptable or resourceful in cases of emergency. under intelligent and careful supervision, however, it is quite possible to get as good results as could be obtained anywhere. the daily rates of wages for a 10-hour day were approximately as given in table 15, these rates being varied in special cases. table 15.--rates of wages +-----------------------------------+-------------------+ | | pesos per day. | +-----------------------------------+-------------------+ | general foreman | 8.00 to 10.00 | | foreman | 6.00 " 8.00 | | cabos | 2.00 " 4.00 | | masons | 3.00 " 4.00 | | bricklayers | 3.00 " 4.00 | | masons and bricklayers helpers | 1.50 | | cast-iron pipe jointers (foreman) | 4.50 | | " " caulkers | 3.00 | | " " helpers | 1.50 to 2.00 | | fire-clay pipe layers | 1.75 | | " " helpers | 1.25 to 1.50 | | drillers | 1.25 " 1.50 | | carpenters | 2.00 " 2.50 | | blacksmiths | 2.50 | | crane men | 6.00 | | peons (laborers) | 1.00 to 1.25 | | boys (watering concrete) | 0.37-1/2 to 0.50 | | watchman | 1.00 | | timekeepers | 22.00 per week. | +-----------------------------------+-------------------+ cost of works. table 16 gives the main items of the approximate expenditure. these include all expenses for preliminary location, engineering, superintendence, purchase of lands, water rights, etc., but do not include other heavy expenditures chargeable to the concession, such, for example, as general expenses, interest at the rate of 6% during the construction period, preliminary expenses for investigations, etc., items which would increase the total by nearly 25 per cent. table 16.--principal items of expenditure. +---------------------------------------------+--------------------+ | | pesos, | | | mexican currency. | +---------------------------------------------+--------------------+ | estanzuela supply : | | | aqueduct and dam | 502,000 | | south reservoir | 429,000 | | | ------ 931,000 | | | | | san geronimo gravity supply : | | | aqueduct, tunnel, and infiltration gallery | 223,000 | | obispado reservoir | 436,000 | | | ------ 659,000 | | | | | san geronimo provisional supply , | | | including boring operations, etc. | 130,000 | | | | | city water distribution system | 1,195,700 | | | | | city sewer system | 1,036,000 | | | | | outfall : | | | main outfall sewer | 425,000 | | sewage purification works | 75,000 | | | ------ 500,000 | +---------------------------------------------+--------------------+ | total 4,451,700 | +---------------------------------------------+--------------------+ as a general statement, the actual cost of labor is about 33-1/3% of the total cost of the construction work, including materials. fig. 20 shows in graphic form the amount of the labor pay-rolls and the progress of the work during the whole construction period from 1906 to 1909, inclusive, comprising also that done under contract. [illustration: fig. 20.--progress diagram showing monthly labor pay-rolls during the construction period.] tariffs and sanitary regulations. _tariffs._--the tariffs charged for the water and drainage service (table 17) were approved by the state government (which accepts the responsibility for their collection), under a compulsory state law which came into force on march 1st, 1910, for the southern portion of the city, and on july 1st, for the northern half, the penalty for non-compliance being a tax of 10% on the monthly rental value of the property, as assessed by the state officials. the basis of the tariffs (which were published on february 22d, 1909) is a charge for water varying between 12 and 16 cents (mexican) per 1,000 liters, with a minimum monthly rate for each different class of property connected to the system. the rate for house drainage is fixed at 80% of the minimum water rate levied on the consumer. the minimum rates have been fixed so that the poorer classes of the community will not be overtaxed, while at the same time the rate is actually levied on the quantity of water used, as indicated by the meter. all the services at the present time are metered, and the meter system will be used throughout. table 17.--the tariffs. +-----+------------+---------+-----------+---------+----------+--------+ | | monthly | liters | price for | minimum | rate for | total | |class| property | of | 1,000 | monthly | drainage | rate | | | rental. | water | liters. | rate. | service. |payable.| | | pesos. | allowed.| cents. | pesos. | pesos. | pesos. | +-----+------------+---------+-----------+---------+----------+--------+ | i | up to 20 | 7,800 | 16 | 1.25 | 1.09 | 2.25 | | ii | 21 to 40 | 12,500 | 16 | 2.00 | 1.60 | 3.60 | | iii | 41 to 60 | 18,750 | 16 | 3.00 | 2.40 | 5.40 | | iv | 61 to 120 | 23,350 | 15 | 3.50 | 2.80 | 6.30 | | v | 121 to 300 | 30,000 | 15 | 4.50 | 3.60 | 8.10 | | vi | 301 upward | 33,350 | 15 | 5.00 | 4.00 | 9.00 | +-----+------------+---------+-----------+---------+----------+--------+ "notes: (1st) the rental for the water meters 5/8-in. size (15-1/2 mm.), which shall always be considered the property of the company, will be 20 cents per month. houses of the first and second classes shall be exempt from paying such rental for one year's time, counting from this date. "(2d) all excess consumption of water over that allowed by the tariff will be charged for at 2 cents less than the price shown in the tariff per thousand liters. "(3d) extra large houses, large establishments, such as colleges, hotels, etc., etc., having a consumption of 50,000 to 60,000 liters of water per month, will pay at the rate of 14 cents per thousand liters. the drainage rate for such buildings will be arranged in proportion to the water tariff, or 80% of the value of the water. "(4th) the laundry establishments, bath-houses, etc., when using 50,000 liters or upward, can arrive at some agreement so as to pay 12 cents per 1,000 liters. "(5th) groups can be formed of two or more small houses so as to obtain a joint service under the proportion shown in the tariff. "(6th) any other combination that cannot be entered into under the basis of this tariff, will be arranged by specially agreed upon prices, such agreement being as much as possible subject to the basis mentioned." _sanitary regulations._--the state government, on march 1st, 1909, published regulations for the proper installation of the water and drainage services within the houses. at the government's request, a draft of the proposed regulations was submitted by the writer, who prepared it, after a study of american and british sanitary by-laws, to suit the special conditions of monterrey. these regulations were afterward modified by him in collaboration with the government technical inspector and financial interventor, and, in their final form, though not as stringent as those adopted in many northern cities, are probably more complete than those in any other mexican city. under these regulations only registered plumbers can undertake plumbing installations, and they have to execute a bond to the satisfaction of the _alcalde primero_ (city mayor) for the sum of 2,000 pesos as a guaranty of responsibility. for defective workmanship or any infraction of the plumbing regulations, they are liable to heavy fines, and can be called on to make good all defects in workmanship, without extra charge to the owner of the property. the provisions of the regulations are carried out under the supervision of the government technical inspector, the company's obligations extending only to the sidewalk and to the meters placed within the houses. engineers, etc. g. s. binckley, m. am. soc. c. e., was chief engineer of the company from february to december, 1906. the writer was chief engineer from may 1st, 1907, until april, 1910, and is responsible for the design and construction of the works carried out during that period. mr. j. d. schuyler advised the company throughout all preliminary studies and investigations, and acted as consulting engineer until february, 1908. the technical inspector, on behalf of the government, throughout the whole progress of the works, has been rudolf meyer, m. am. soc. c. e., and the writer wishes to record the valuable assistance the company has received from him. in conclusion the writer may be permitted to pay a tribute to the devoted public spirit shown by his excellency, general bernardo reyes, the governor of the state of nuevo león from 1885 to february, 1910, and who, untiring in his devotion to the interests of the city, was primarily responsible for the inception of the works and their successful completion. discussion. james d. schuyler, m. am. soc. c. e. (by letter).--for completeness of detail and wide range of subjects of general interest to engineers, this paper is certainly one of the notable contributions to recent engineering literature. it is a minute and painstaking record of the successful accomplishment of construction work under unusual climatic conditions and difficult circumstances, and reflects credit on the author, not only in his capacity as an engineer, but as a faithful recorder of facts. it was particularly fortunate that he was an eyewitness of the disastrous and extraordinary flood which swept through monterrey, destroying many lives and much property, and has thus been able to give an intelligent estimate of the maximum discharge of the river during the height of the flood wave of august 27th-28th, 1909, when the rate of run-off per unit of area of water-shed drained reached an amount which has seldom been equalled or exceeded, as far as reliable records extend. it is worthy of note that works deriving their water supply from the source of such torrential floods should have survived with so little actual damage, and with scarcely any interruption of service. the repair of all damages to the system was estimated to have cost not more than $20,000. as mr. conway did not assume charge of construction until may, 1907, he was spared the responsibility of deciding on the general plan of securing an abundant supply of pure water from sources permitting of delivery by gravity under adequate pressure for fire protection--a responsibility which devolved on the writer, assisted by g. s. binckley, m. am. soc. c. e., mr. conway's predecessor, as chief engineer. not only the water-works, but the system of sewerage and sewage disposal by broad irrigation were subsequently carried out on the plans submitted to the state government by the writer in 1906, and given provisional acquiescence at that time. there was no lack of water at hand for the supply of a city of that size, as there are large perennial springs which flow out of the travertine of the plain, and are used for irrigation in the valley below the city. one of the largest of these, near the civic center, has a normal flow of nearly 30 cu. ft. per sec.; another nearby, also within the city limits, flows some 10 or 12 sec-ft., while both the estanscia and robalar springs, but a few miles below (shown on plate ii), discharge more than 20 sec-ft., as nearly as memory serves. besides this supply, the water to be developed by sinking shafts in certain parts of the plain, as demonstrated at the brewery and elsewhere, was apparently a reliable source of large volume. to utilize these sources, however, would have involved condemnation of the water-rights in the case of the springs, depriving present owners of the use of the water, and this governor reyes wished to avoid. besides, it would have necessitated pumping the water for the city in perpetuity, an expense which the governor was equally anxious to save; hence a gravity supply was made the prime requisite of the plans. until the concession was granted, and for a year or more afterward, it was assumed that an adequate supply could only be obtained by the storage of the flood-water of the santa catarina river in a large reservoir; and the earlier plans of the concessionaires were based on the construction of a high masonry storage dam at the upper end of the "narrows," where the river turns from a western direction to a course almost due east, between high vertical cliffs of limestone. the concession distinctly provided for such a dam, and among the plans on file in the state capitol is one prepared by the late e. sherman gould, m. am. soc. c. e., for a masonry weir across the gorge. samuel m. gray, m. am. soc. c. e., also filed a plan and report proposing a capacious, shallow, storage reservoir near the city, to be filled by a large flood-water canal from the santa catarina cañon. although the writer could not have anticipated the occurrence of floods of the magnitude of the one of august, 1909, which would surely have destroyed any reservoir built in the cañon, he was unable to endorse the storage plan of water development, chiefly because of the uncertainty of the water-tightness of the reservoir in a cavernous limestone formation, and also because of the probable impurity of water draining from such extensive goat pastures. he, therefore, urged the development of the underflow of the river, which was manifesting itself in the springs referred to. mr. binckley secured two keystone drilling machines and proceeded to profile the bed-rock at santa catarina cañon and at san geronimo, the two places on the stream where the river flows between walls of rock _in situ_. at both sites the strata were standing nearly vertical across the channel, and, by careful sampling and testing, it was found that in both locations there were thick strata of limestone so highly silicious as to be insoluble, and hence free from caverns. from this determination it was concluded that all the water which appeared in the valley below must pass through the sections where the borings were made. the results of this drilling, however, proved conclusively that the depth to bed-rock at either place was too great to permit of a masonry dam being considered as practical, and demonstrated the inadequacy of methods which had been used in the earlier investigations when dams were regarded as feasible. the results have also shown that the subterranean supply at the lower cross-section of the river, at san geronimo, is abundant, and can probably be increased to an indefinite degree by continuing the filtration gallery; while at santa catarina the same type of development can be made for a high-source supply, although requiring a long and expensive tunnel and conduit. david t. pitkethly, assoc. m. am. soc. c. e. (by letter).--having been engaged on the design of sewerage systems for some years, the writer finds this paper of peculiar interest, particularly the sewerage portion. there are some points in the design, however, which do not appear to be clear. the system is described as "strictly separate," and yet the sewers are designed to run half-full, providing a capacity of 200%, the 100% basis, or 380 liters per capita, being 90%, or 180 liters, in excess of the calculated water supply of 200 liters per capita. it has been the writer's practice to design sanitary sewer systems on the basis of the water consumption, and to assume the whole daily amount to reach the sewer in 16 hours, thus providing capacity sufficient to care for the maximum or wash-day flow without causing the sewers to run above the calculated hydraulic gradient, which should be placed within the pipe so as to provide air space for ventilation under all circumstances. the practice of calculating sanitary sewers to run half-full is a good one when ground-water is expected in sufficient amount to fill the remaining portion of the sewer, but when no ground-water, or roof-, or surface-water is allowed to enter the system, or all precautions are taken to exclude such, then the system may be designed so that the expected maximum, or wash-day flow, will fill the sewer to the desired hydraulic gradient. the method of ventilating the sewers does not seem practicable. the houses are principally of one story, and yet the stand-pipes on the sewers have openings 25 ft. 9 in. above the sidewalk. are the ventilating or vent pipes of the house plumbing carried to a height to balance this, or will these chimneys draw the air from the house drains and fresh-air pipes, breaking the seal in the so-called disconnecting traps, thus causing the circulation of air in the house piping to be downward through the sewers instead of upward through the fresh-air inlets and vents, as designed? it is interesting to note that crude sewage, as well as the liquefying (septic) tank effluent, is to be applied to land for irrigation purposes, but the application of crude sewage without any attempt at removing the suspended matter, or the effluent from the septic tanks where only a partial removal occurs, seems to be bad practice. the author states that: "the degree of purification in the tanks was relatively unimportant; the object to be obtained consisted chiefly in distributing on the land an effluent which would be innocuous and clear." how he expects to obtain such an effluent by passage through screens, detritus tanks, and septic tanks only, is more than the writer can understand. the removal of suspended matter in a septic tank depends on the strength of the sewage, the time of retention, the time elapsing between cleaning, the presence of trade wastes, etc., and seldom exceeds 38 per cent. the subject of septic tanks and their effect on sewage is discussed in the "fifth report of the royal commission on sewage disposal" (england, 1908), and the following extracts, relative to the application of crude sewage to land and the effect of septic tanks on sewage, seem apropos: "23. * * * there are also many cases in which crude sewage has been passed over land, but the evidence shows that land treatment of crude sewage is liable to give rise to nuisance by the accumulation of solids on the surface of the land. moreover, in some cases these solids are apt to form an impervious layer, which interferes with the aeration of the soil, and so impairs the efficiency of the treatment." "31. * * * at that time it was claimed that the septic tank possessed the following, among other, advantages: "that it solved the sludge difficulty, inasmuch as practically all the organic solid matter was digested in the tank. "that it destroyed any pathogenic organisms which there might be in the sewage." "32. as regards the first of these claims, it is now clearly established that, in practice, all the organic solids are not digested by septic tanks, and that the actual amount of digestion varies to some extent with the character of the sewage, the size of the tanks relative to the volume treated, and the frequency of cleansing." "at huddersfield, mr. campbell estimated that about 38 per cent. of the solids were converted into gas or digested; * * * while at birmingham, messrs. watson and o'shaughnessy say that the figures available indicated a digestion of not more than 10 per cent. of the suspended matter entering the tanks." "33. as regards the second claim, we find as a result of a very large number of observations that the sewage issuing from the septic tanks is, bacteriologically, almost as impure as the sewage entering the tanks." messrs. winslow and phelps, in their interesting paper, "investigations on the purification of boston sewage,"[8] quote a suggestion made by stoddart (1905): [8] water supply and irrigation paper no. 185, p. 125. "he finds, in a septic tank of several compartments, a considerable deposit of sludge in the first compartment, giving a fairly clear supernatant liquid, which in the last chamber of all undergoes a secondary decomposition, leading to the throwing down of an additional precipitate of offensive sludge." what took place in the case referred to by stoddart corresponds to the author's observations of the liquid leaving the tanks in a clarified condition, but the secondary decomposition must take place in some manner, and, when it does, a nuisance seems to be unavoidable where no provision is made to care for it. in view of the experience of others, some further treatment seems to be necessary. such treatment should include disinfection, as no method of disposal yet devised has succeeded in reducing materially the pathogenic germs usually to be found in sewage and tank effluents. if the crops to be irrigated are to be eaten, uncooked, by mankind, then disinfection at least is imperative. george s. binckley, m. am. soc. c. e. (by letter).--mr. conway's admirable paper is of special interest to the writer, as the entire general design of the system, as well as the extensive hydrological studies and final selection of the sources of water supply, was completed during 1906 through the joint labors of the writer, as chief engineer, and james d. schuyler, m. am. soc. c. e., as consulting engineer. in this work, mr. schuyler and the writer had the rare privilege of dealing from its inception with the problem of designing a complete and somewhat extensive system of municipal water supply and drainage, unhampered by any existing works to which the new systems would have to be adapted. it would probably be difficult to find in the united states a city of 85,000 inhabitants, previously totally lacking either a water supply or sewerage system, which, under a consistent and harmonious design, has been provided with both in the degree of completeness and structural excellence exemplified in the works at monterrey. the few important changes or amplifications made in the original design, and the manner in which its detail has been executed is naturally most interesting to the writer, and this excellent paper should be of very substantial value, particularly to engineers engaged on similar work in mexico or spanish america. the very novel construction method adopted by mr. conway in the roofing of the south or guadalupe reservoir, seems to the writer rather to invite criticism, and the fact that in the subsequent construction of the roof over the rectangular obispado reservoir the customary monolithic concrete construction was apparently reverted to after experience with the separate-unit plan previously used, would indicate that mr. conway reached the same conclusion. the original design of the circular guadalupe reservoir contemplated just about the same arrangement of columns and roof support as that actually used, but the writer had expected that the columns would be cast in place, and that the system of primary and secondary beams would be filled at the same time as, and integral with, the roof slab, the reinforcement being placed in accordance with what may be described as conventional practice. the writer believes that the efficiency of the concrete and steel placed in this manner would be notably higher than under the system actually adopted, which, in effect, is pretty much the same as constructing the supporting system of units of cut stone. if, with all the elements of structural weakness involved in the multiplicity of mortised joints, discontinuous reinforcement, etc., this construction is strong enough, it would seem that an important reduction in the dimensions of the members could have been effected by monolithic construction and continuous reinforcement, without sacrifice of strength. the comparison, in table 7, of the costs of these two reservoirs, is interesting, but very moderately illuminating, as the comparative unit cost of the most important element in their construction--the concrete--is not given. the total excavation cost for each reservoir is practically the same, and the general expense, engineering, and cost of fittings and accessories presumably so, but the total cost of the guadalupe reservoir as given is $19,000 (pesos) in excess of that of the obispado reservoir, while, in the latter, there were 756 cu. m. more concrete. this certainly indicates a much higher cost of concrete per unit as laid in the south (guadalupe) reservoir. an actual comparison of the cost per unit of concrete laid under the two systems would be instructive. the writer is interested to observe that the same system of sub-drainage used by him in the construction of the reservoir for the provisional supply of water from san geronimo, has been used by the author in the obispado reservoir. this arrangement of drains under the floor of the reservoir at san geronimo was devised as a safeguard against damage to the lining through the accumulation of water inside the impervious bank against its back. it was realized that, in such a climate as that of monterrey, perfect water-tightness of the lining might be difficult to secure or maintain, and, if leaks existed, a sudden draft on the contents of the reservoir might result in serious damage through the static pressure exerted against the lining of the sides or upward thrust against the floor. in the writer's opinion, such a system of drains is an important element, as not alone the fact but the quantity of leakage may be determined, and danger of saturation of the supporting bank avoided--a matter of importance where, as is sometimes the case, the material of such a bank is unfit to resist the effects of saturation. the author does not state whether or not this safeguard was omitted in the guadalupe reservoir. incidentally, however, the matter of saturation of the bank is not important in either reservoir, as the material of which these banks are constructed is such that settlement or failure through saturation is out of the question. it may be remarked, however, that in fixing the angle of the sides of the guadalupe reservoir at 60° the writer contemplated the same system of constructing the bank as he used in that of the san geronimo reservoir. in this case, the bank was built up by spreading the material in thin layers, wetting down, and rolling and puddling by the passage of the ox-carts used for the transportation of the material, the wheels of the carts, and especially the cloven hoofs of the animals, producing a most excellent effect. the inside slope was built up in this fashion to a much lower angle, and with a top width considerably in excess of the finished dimensions. the excess material was then picked off to the line, and exactly to the slope. thus the finished slope presented a surface which was compacted to a degree impossible to attain at or near the surface of the bank as built, and presenting a support of the best possible character for the concrete lining and coping. v. saucedo, assoc. m. am. soc. c. e. (by letter).--the author's description of the water-works and sewerage of monterrey, one of the most extensive schemes in mexico, will be of general interest to engineers, especially those engaged in hydraulic and sanitary problems. the writer, having been connected with the works for four years, knows the local conditions well, and presents herewith some complementary data on what he considers an important feature, the subject of floods, mentioned by the author on different occasions, especially as certain developments in the works show the importance of such occurrences as a factor in designing. abnormal rainfalls of long duration and high intensity are common in the semi-arid region of mexico. they come at irregular intervals, though tending to coincide with the early fall. the floods of august, 1909, were a repetition of similar occurrences in the past; and, though there are no numerical records of previous cases, local traditions and historical state documents describe them as having occurred since the foundation of the city, at intervals of from 15 to 40 years. the graphic descriptions of the places flooded are in accord with the character of the floods of august, 1909, and september, 1910. the diagram, fig. 21, is a record of the rainfall during the latter flood, and was plotted from intermittent readings of standard gauges. it demonstrates that the intensity increased toward the mountains on the south, which form the tributary water-shed of the santa catarina river, showing a difference of 10.54 in. between the city and the estanzuela dam, which is not quite 12 miles to the southeast. [illustration: fig. 21.--rainfall during floods of september 14th-16th, 1910, in monterrey.] an estimate of the volume of discharge of the river at the time of maximum flood is only a reasonable conjecture which (without special reference to accuracy) aims to impress those who have not witnessed such occurrences with the tremendous volume coming from barren steep surfaces previously saturated. the original computation, referred to by the author, was obtained from the average of two different methods which gave results close to each other. in one method the extent and nature of the water-shed were considered, together with the maximum period of precipitation that occurred, sufficient to gather a maximum volume of water in the river. in the other method the volume was derived from a cross-section of the wetted perimeter of the river at the time of maximum flow, in combination with velocity approximations obtained by using rough floats. this gave 271,500 cu. ft. per sec. the figure submitted by the author, 235,000 cu, ft. per sec., is in accord with the proposed formula[9] for impervious surfaces by c. e. gregory, m. am. soc. c. e. in the first and last methods, the intensity, a governing factor, is more or less of an assumption, and the cross-sectional method is also unreliable, as the river-bed was greatly disturbed, due to the high velocity of the water, which deepens the channel to a considerable extent at times of maximum flood, the gravels being redeposited during the period of subsidence. such was the case during the flood of september, 1910, when the depth of gravel above the roof of the san geronimo infiltration gallery was diminished to such an extent that it was so inefficient as a filter for the flood as to permit the percolation of turbid water into the underground supply. [9] _transactions_. am. soc. c. e., vol. lviii. p. 458. during the floods of august, 1909, shafts nos. 2 and 3 were damaged beyond repair, and sand and gravel, entering through them, blocked up the gallery to within about 150 ft. of shaft no. 1. the interior timbering probably collapsed, due to cavings and disturbance in the river-bed during the period of maximum flood, but no explorations have been possible on account of the great quantity of water still coming through (at present more than 650 liters per sec.). for this reason the work of driving the gallery, as well as lining shaft no. 1, has been suspended. [illustration: plate xxviii, fig. 2.--view of santa catarina river in flood, on august 28th, 1909.] [illustration: plate xxxi, fig. 1.--flush-tank carried down by flood of august 27th-28th, 1909.] [illustration: plate xxxi, fig. 2.--view showing scouring effect of flood on san geronimo aqueduct.] [illustration: plate xxxii, fig. 1.--view of santa catarina river after the flood.] [illustration: plate xxxii, fig. 2.--view of santa catarina river flowing through low-lying streets, 8 days after the flood.] on reaching the city, the flood of august, 1909, swept away two streets adjoining the river. these streets had been built on made ground, in what was originally the river-bed. the sewers and water mains laid in them were destroyed entirely, and some 460 ft. of the 24-in. cast-iron pipe, buried under the river-bed at a depth of 8 ft., were carried away. in relaying this portion of the main, and for protecting the remainder of it across the river, it is now proposed to encase it in a solid rubble concrete block, 8 ft. square, which will impart weight and stability against the scouring effect of floods. the south reservoir is circular in shape, with an interior diameter of 165.68 ft. at the top, and is partly excavated in the ground and partly completed by an embankment of vast proportions (fig. 10). right after the flood of august, 1909, a wet spot appeared on the northeastern toe of the embankment, and it was supposed for some time that it was the effect of the saturation produced by the preceding rains, but, as it persisted for several months, it was obvious that its origin was in the interior of the reservoir, which was emptied when the writer took charge of the work. the first inspection revealed a horizontal crack in the concrete lining, about 310 ft. long and extending about 153° around the circumference on the north side. throughout its length it coincided with the line of cut and fill. vertical cracks, coinciding with the panel points in the lining, had also developed, and extended from the main horizontal crack to the roof. the circumstances originating this development can be conjectured by considering the position of the main crack, its characteristic features, and the conditions that preceded its formation. the coincidence of the crack with the joint of cut and fill, points to this line as a source of danger. an examination showed, besides, that the fracture was clean and sharp, ranging in thickness from a hair line at the ends to 3/16 in. at the center, and that its upper border projected over the lower one perceptibly, a proof that horizontal motion had taken place. the vertical cracks were a secondary effect, the consequence of the displacement immediately after it was scoured. a fracture was discovered in the floor of the reservoir. it started at the center and branched out into two diverging lines in a radial direction. the circumstance of two abnormal rainfalls, giving 35 in. in 9 days, the precipitation being concentrated in two periods, not far apart, of 42 hours and 98 hours, respectively (fig. 4), together with lack of provision for shedding the water from the roof of the reservoir and from the surrounding embankment, lead to the inference that the latter became saturated, increasing thereby in weight and decreasing in stability, especially in its steep inner face. a settlement and the consequent horizontal displacement, under these conditions, was natural. the concrete lining, only 16 in. thick at that height, was not sufficient to sustain the resulting strain, and the main fracture developed, permitting the stored-up water to leak into the bank. in time this seepage found its way under the bottom of the reservoir, softening the ground and producing a slight settlement which caused the crack in the floor. had under-drainage been provided, as at the obispado reservoir, the actual conditions would have been noticed earlier. however, as the embankment is of vast proportions, stable in itself to sustain with a large margin of safety the weight of the stored-up water, there was no actual danger of failure, except for the fact that the material forming the structure, on account of its calcareous nature, is dissolved by water. long exposure to this condition would, in time, open passages in the embankment, and it is certain that there would be cavings in its interior. the necessary grouting has been done, and provision is being made for water-proofing the interior of the reservoir and shedding the water from the roof and from the embankment, thus relieving the structure of the consequent strain. another place in the works where floods have had a damaging effect is the estanzuela intake basin, which, when the dam was completed, was filled to the overflow level in order to test its water-tightness. as this basin, when cleaned, was found to be slightly fissured on the north side, it was decided to line it with concrete. as shown in fig. 8, the lining does not cover its entire area, but only the central portion, leaving a strip on either side without protection. the flood of september, 1910, coming in greater volume than the previous ones of august, 1909, in passing through the narrow gorge at the entrance, undermined the lining in those places where it was not founded on solid rock. figs. 1, 2, and 3, plate xxxiii, show some of the damage caused by this flood. the buoyant effect of the water and the impact of large rolling boulders caused fractures all over the surface, and lifted the concrete lining bodily; but the dam proper, being founded on rock bottom, did not suffer any injury. in the future, in order to avoid the seepage of the ordinary supply, alluded to by the author, the water will be carried to the valve-house in an open rubble concrete channel, lined with cement mortar and built high up against the western hillside. the remainder of the basin will be paved with large boulders. [illustration: plate xxxiii, fig. 1.--estanzuela dam: broken concrete basin lining.] [illustration: plate xxxiii, fig. 2.--estanzuela dam: broken concrete basin lining, east side.] [illustration: plate xxxiii, fig. 3.--estanzuela dam sept. 26, 1910: view of shearing fractures of wall and lining after flood sept. 14-17, 1910.] in conclusion, the writer wishes to emphasize the point that, notwithstanding the severity of the test, relatively small damage was inflicted on the extensive works carried out under the author's design and direction. a test so severe that it caused serious damage and immense losses in the entire region, washing away kilometers of railroad track and destroying practically all the bridges within reach of the flood, is an occurrence of paramount importance, and should be remembered as a leading factor in the design of engineering works. george t. hammond, m. am. soc. c. e. (by letter).--in a country, such as that described in this paper, where water is valuable, and a shortage is at times possible, where the majority of the population is very poor, and water and sewage discharge are both to be paid for on a basis of volume, the question of the expected quantity of daily water supply and sewage flow per capita is of primary importance. this question, notwithstanding its difficulty, should be given a first place in the studies for water-works and sewerage projects, and should never be lost sight of in the design, which should be such that, while proper for the expected future flow for a reasonable time, should also be proper and economical for conditions which at present obtain and may change but slowly. it is desirable, of course, to get as much capacity in works as one can for the outlay, but there are instances where one can get too much for the money, as where a larger pipe than is necessary is used for a sewer, merely because it costs about the same as a smaller one, and as a result the cost of maintenance is permanently increased. the water-works were designed to supply 40,000,000 liters (10,582,000 gal.) daily, which it was assumed would be sufficient for all future developments in monterrey for a population of 200,000 at a per capita consumption of 200 liters (about 53 gal.) per day. the present population of the city is given as less than 90,000, there having been an increase of 22,000 in ten years (1891-1901), but it is evident that in the last ten years (1901-1911) this rate of increase has not continued. taking into account all the data known to the writer, it does not seem that the city will attain a population of 200,000 in a great many years, if it ever does; but this is a matter of personal opinion, and is only stated as such. the present requirements of the city's population, assuming that each person uses 200 liters (53 gal.) per day, would be, at that rate, which is a very liberal one, only 18,000,000 liters (4,762,000 gal.) per day, or less than half the amount which may be provided. if the water were not to be metered and the sewage discharge paid for by measure, it is possible that the free use of water might lead to the usual waste with which all are fairly familiar; but the use of meters, and the rates charged, will reduce the water consumption to a minimum. this end will especially result from section 5 of the tariffs which provides that: "groups can be formed of two or more small houses so as to obtain a joint service under the proportion shown in the tariff." this provision will keep down the per capita supply, among the majority of the people, to about 37-1/2 liters (10 gal.) per day. a similar provision led to abuse in santiago de cuba, as well as in other cuban cities, where one householder, taking water, frequently delivers it to adjoining houses and tenements through rubber hose. as many as ten or twelve families are sometimes found to be supplied from one tap in this manner. indeed, it may be stated as a rule, having but few exceptions, that where water is paid for by meter its use is always restricted. the water mains and distribution system, however, are so well laid out, and the whole design is so good, that the writer would not anticipate much difficulty because it is on rather too liberal lines for the present or probable future. it may, perhaps, be argued that it may cost more to keep the mains in such a system clean; but this extra cost will scarcely be of much moment, and will be offset by the greater lasting quality of the larger pipes. there is another feature of the problem, however, which is not affected favorably by a too liberal forecast of the per capita water supply, namely, the sewerage system. if it is assumed that, using 200 liters per capita per day, the total water supply of the city for the present population will be 18,000,000 liters, and that this may double in fifty years, or even amount to 40,000,000 liters in that time, it would seem that a rather liberal provision has been made for the water supply, and that this will scarcely be exceeded by the sewage, for the latter must come from the water supply, there being little or no ground-water and no storm-water taken into the sewers. designing the sewers to flow half full for all diameters less than 18 in., and seven-tenths full for all larger sizes, it would seem that this would give ample capacity for all time to come in such a city, and that good practice would not exceed these figures, it being more desirable that the sewers should not be too large to work well, than that they should be large enough in all places to meet every possible contingency. if all the sewers of a system are too large, the condition is incurably bad; while, if a few miles prove to be too small, on account of growth and prosperity not anticipated by the designer, it will be easy enough to relay such parts when this becomes necessary. mr. conway states that: "the sewers are designed on a very liberal basis, namely, on the assumption that when flowing half full the quantity to be dealt with will be 380 liters [100 gal.] per capita per day, with a maximum rate of flow of 200 per cent." if the writer understands this statement correctly, it means that the sewers, flowing half full, will carry 380 liters per capita in 12 hours, or are designed with 200% of the capacity required to take the assumed flow in 24 hours. it was assumed that each house would be occupied by 7 persons and have a frontage of 12-1/2 m. (about 41 ft.), that is, about 700 gal. per day per house, the maximum flow rate being 200%, or at the rate of 700 gal. per house in 12 hours. it is to be remembered that nearly all the houses are of one story, and that, as a rule in tropical and sub-tropical countries, the per capita use of water diminishes with some function of the increasing number of inhabitants in one house. most of the water is used in the kitchen, and where there are 7 persons instead of 5, the quantity used by the smaller number will generally serve the larger. the writer is unable to understand how this quantity of sewage will be produced, especially as the author states that, as far as the company is concerned, it is limited to the removal and disposal of the sewage, and is not required to provide for storm-water. he also states that: "apart from that fact, however, the best system for a city like monterrey, where rainfall for many months at a time is very scarce, is the strictly 'separate system'." the minimum velocities in the sewers, when running full, vary between 0.91 and 1.5 m. (from 3 to 5 ft.) per sec., and will be the same flowing half full. from the foregoing data it will be observed that: (1) the water supply is the only source from which sewage flow is anticipated; (2) the water supply is very liberally estimated at 200 liters (53 gal.) per capita daily; (3) for purposes of sewer design, the daily flow of sewage expected (all of which is derived from the water supply of 200 liters per capita) is estimated at 380 liters per capita, with a maximum rate of flow of 200% (or at the rate of 760 liters per capita), and with this quantity the sewers are designed to flow only half full; (4) the gradients are such that a velocity of from 3 to 5 ft. (0.91 to 1.5 m.) per sec. will be secured in the sewers flowing half full with the above quantity of flow per capita. the writer does not agree with this method of computation, as he feels sure that it will give sewers which are too large, with grades too steep for the best obtainable results. his experience, extending over more than twenty years in sewer design and hydraulic work, convinces him that the method pursued is wrong in principle. the principles involved in sewer design are first of all hydraulic. the quantity of flow, in the nature of things, cannot be forecasted accurately; success depends on getting the nearest possible approximation to average conditions. if 200 liters per capita per day is a liberal allowance, and 40,000,000 liters per day is a liberal expectation at this rate for double the present population, and the sewers are designed to flow half full only, why should this again be doubled? the design of a sewer system for a city such as monterrey is, in fact, a very difficult problem, especially as the quantity of sewage will be very limited, flush-water will have to be used in considerable quantities, and water in that part of the world is precious at all times and often scarce. under these circumstances, the size or shape of the pipes selected for the lateral sewers, should have been such as would more nearly agree with the requirements than does the 8-in. circular. a. p. folwell, m. am. soc. c. e., writing of the 8-in. circular size, states:[10] [10] "sewerage," by a. p. folwell, m. am, soc. c. e. "to secure a flow in this pipe having an average depth of 4 inches would require the sewage from a population of 6,500. in general it may be said that the ordinary depth of flow in any sewer should not be less than 2 inches, nor should it be less than 1/2 the radius of the invert, since if it is so there is much more danger of deposits forming along the edges and even in the center of the stream. it will sometimes be impossible to meet this requirement fully, but it should be kept in mind as extremely desirable." sewers of small size should be proportioned throughout the system so that the depth of the minimum daily flow in the invert, and the velocity of flow, will be the best possible to prevent deposits. the transporting power of water is dependent mainly on the depth of flow, a minimum velocity being selected rather than a minimum depth of flow. to those who have had charge of the maintenance of sewers, as well as of their design and construction, this principle seems so obvious that it is always a surprise to see it disregarded by designers, who in these days seem inclined to consider sewerage as a system of grades and sizes of pipes installed for ideal, rather than for actual, conditions. messrs. staley and pierson have well stated the principle involved as follows: "a stream having a depth of flow sufficient to immerse solid matter held in suspension, to a certain extent lifts it and carries it forward. the entire surface is also exposed to the action of the current. a stream having an equal velocity but a less depth in proportion to the diameter of the solid matters to be transported, evidently has less transporting power. * * * an amount of sewage which can be properly transported by a circular sewer of a given size, cannot be as efficiently transported by one of larger diameter." from some strange idea, which is apparently without foundation in logic or based on any actual justification from experience, it has of late years become the practice of designing engineers to make the 8-in. circular pipe the smallest size for sewers; and it is not improbable that the designer of the monterrey system has merely followed this example. it has also become the frequent practice of designers to give every length of sewer all the grade possible, regardless of the fact, taught both by hydraulics and experience, that the best grade is that which will give as much depth of flow as is consistent with a scouring velocity. some years ago it was the standard practice, in the "strictly separate system" of sewers, to use the 6-in. pipe as the minimum size, and, as far as the writer has been able to discover, after giving the matter a rather extensive investigation, the 6-in. size has given excellent results wherever its use was proper. in places where it has not succeeded there were excellent reasons why it should not have been selected, and these could easily have been observed at the time the designs were made. the best sizes for the sewers in a given system is always a matter to be determined by local conditions; but there seems to be no reason why the 6-in. size should not be used where the flow is so slight that the 8-in. will not work well; or where the velocity must of necessity be so great that a flotation depth of flow cannot be maintained in the larger size. as to likelihood of clogging and stoppage, the writer's opinion, based on the maintenance of three rather extensive systems in different parts of the united states, in each of which the 6-in. size comprises more than 75% of the whole length of pipe, and of three other systems, one having 12-in. and two having 8-in. as the minimum sizes, is that the 6-in. size, where properly used, is less likely to become clogged than either of the others used improperly. the cost of maintaining the 6-in. pipe lateral, under these circumstances, is much less than that of maintaining the 8-in. lateral. the 6-in. pipe is not being used now as much as the 8-in., and in most cases this is probably because the capacity of the latter is nearly double that of the 6-in., and costs only a few cents more per foot. if there is a sufficient population per acre, or if, within 30 or 40 years, such a population is anticipated as will fill the 8-in. pipe half full, its use, of course, is justified and necessary; but where it is quite evident that this will never occur, its use is counter-indicated. in monterrey, where the building lots have a frontage of 41 ft., where the houses, as a rule, are only one story high, where the water service is metered and paid for, and the sewage flow is also paid for, there seems to be no reason to justify the use of 8-in. pipe for the upper reaches of the smallest sewers. the sewage flow to be anticipated will probably never be sufficient to keep an 8-in. pipe sewer in a good clean condition at the upper ends of the lines of sewers without excessive flushing; and the sharper or steeper the grade on which it is placed, the worse will be the result, because the sharper the grade, the thinner the flowing thread of sewage will be drawn out in the invert; on the other hand, if the grades are flat, the slight quantity of sewage flow will be spread out in a sluggish stream, without sufficient depth, on the bottom of the 8-in. pipe. where a wide surface is given to a small quantity of flowing sewage, it stagnates slowly along the bottom of the sewer, leaving frequent deposits to undergo decomposition and create foul air, if not to choke the sewer, a result often produced; and where a circular sewer which is too large for the ordinary flow is given a strong velocity by using steep grades, the stream, though flowing rapidly, is drawn out to such a thin thread that it will not effect the flotation of the solid masses in the sewage brought in at house connections, and the shallow and thin stream simply flows around such masses until a dam or obstruction forms and the sewage is backed up sufficiently to force the obstruction farther down, to form another obstruction in a larger pipe below. flushing may possibly keep such a sewer fairly clean; but, as usually practiced, it is effective only for a few hundred feet from the flush-tank; and the quantity of flush-water required by an 8-in. pipe is more than twice as much as that required to keep the 6-in. pipe clean. ventilation is better in the smaller sewer than in the larger, as there is less air to move; but the elaborate ventilating stacks provided at monterrey may take care of this; and it is evidently a place where ventilation will be needed. the ideal size and shape of cross-section for a sewer is such as will give the best flotation to moving solids which are being carried along by the flow; and this means the sewer that, with the expected ordinary or average flow, will give the best depth in the invert, when the velocity of flow is sufficient to keep suspended solids, grit, etc., moving at a rate of from 2 to 3 ft. per sec. the size, however, is limited by practical considerations. the circular pipes cannot well be less than 6 in. in diameter, because the house connections cannot well be less than 4-in. pipe, and the sewer should be larger than the house connections, for various practical reasons; but, in order to secure flotation and a scouring flow, the smallest pipe, or the pipe having the smallest invert radius, that practical considerations permit, should be selected. the grade should be such, and the collecting system so laid out, that the flow may be conserved as far as possible, and the sewage flow should be kept of as great a depth in the invert, or bottom of the sewer, as safety in self-cleansing velocity will permit. this will save flush-water and prevent stoppages, and thus reduce the cost of maintenance to a minimum. for good sanitary practice, the sewers should be designed, first of all, to comply with the requirements of the present, or immediately expected, ordinary flow, with some reasonable allowance for the future. they should be neither too large nor too small, and the grade should neither be too great nor too little, to secure the best flotation and scouring effects and the best flush-wave action under all circumstances. the use of cement concrete pipe for sewers seems to be growing in favor; nor is this surprising, in view of the many improvements made in their design and manufacture. the excellence of the concrete pipe used in monterrey and its success, suggest the query: why was it not used still more extensively? table 13 shows that the cement pipe cost much less than the vitrified tile, or "fire-clay" pipe. thus, the 38.1 cm. (15-in.) fire-clay cost 6.14 pesos per lin. m., the 45.7 cm. (18-in.) cost 8.80 pesos, and the 50.8 cm. (20-in.) cost 11.30 pesos. compared with this, the concrete pipe was much the cheaper; the 55.9 cm. (22-in.) cost 5.93 pesos, which is less than the cost of the 38.1 cm. (15-in.) fire-clay; and the 61.0 cm. (25-in.) concrete pipe cost 7.30 pesos, which is less than the 45.7 cm. (18-in.) fire-clay. the writer's experience with concrete pipe, derived mainly from a long service in sewer design and construction in brooklyn, n. y., leads him to believe that at monterrey the whole sewer system might, with advantage, have been built of concrete pipe, using an egg-shaped pipe with an area slightly larger than an 8-in. circle, designed for a discharge equal to an 8-in. pipe for all the smaller sewers. the invert of such an egg-shaped pipe would fulfill the present requirements in carrying a very small flow with good flotation depth, better than would a 6-in. circular pipe, and the reserve capacity of the 8-in. pipe would be secured without interfering with good present service. egg-shaped pipes, similar to those used in brooklyn, the writer believes, would have given far better satisfaction throughout the monterrey sewerage system than circular fire-clay pipe, and would have cost no more, but probably less. the egg-shaped pipe referred to is made with a flat base and a self-centering joint, thus insuring perfect alignment, and a smoother interior surface than can be obtained with fire-clay pipes. brooklyn has about 450 miles of concrete pipe sewers, of all sizes less than 24 in., the greater part of which is egg-shaped. there are also about 250 miles of vitrified stoneware circular pipe sewers of similar sizes, and the cost of repairs and replacing pipe, over a period of years is about the same per mile for each kind. incidentally, it may be stated that the annual cost of repairs per mile on both kinds of pipe is very small, and is only about one-fifth of the cost of repairs per mile on the brick sewers, of which there are about 200 miles. the principal advantages and disadvantages of cement concrete pipe sewers may be summed up as follows: advantages of concrete pipe. (a) cement concrete pipe is usually less costly than vitrified pipe. (b) it can be formed in any shape desired. (c) it is not cracked by vibration, and resists impact better than vitrified pipe, for which reason it is a better material to lay near the surface of a street in which there is heavy traffic. (d) it is not affected by ordinary sewage. (e) the cost of repairing and maintaining is about the same as for a vitrified pipe sewer. (f) it can be made in the city or town where it is to be installed, thus giving the locality the advantage of having some of the money paid for labor in its manufacture spent in the place where the sewers are being put in, where it is raised as a tax, etc.; also saving freight charges, etc. (g) it can be made under the most careful local supervision and inspection, of selected material, by the engineer who is responsible for the success of the work. vitrified pipe can seldom be made in this way. disadvantages of concrete pipe. (a) if not carefully made and of the best of materials, it is subject to failure by disintegration, etc. (b) it will not stand strong chemical action, and therefore the smaller sizes should not be used where they are likely to be exposed to trade wastes containing strong acids. in the larger sizes the quantity of flow mixes so quickly with the trade wastes that this danger is minimized, and it is very seldom that even the smaller sizes become affected; but vitrified pipe may be used in places where chemical action is anticipated. (c) if not properly made, it will be attacked by steam and hot vapor, and by animal fats in the sewage; but, if properly made, it is not affected by these. (d) unless reinforced or made very thick, it will not stand as great a crushing load as the best vitrified stoneware pipe; but, as sewers are not intended to be used under very heavy pressure, this is not so very important. it is amply strong to withstand any internal pressure or any external crushing load to which it probably will be submitted. (e) under a considerable head of ground-water, it may permit water to infiltrate through its walls for a considerable time after it is laid, thereby temporarily increasing the flow, which, if the sewage is to be pumped, will increase the cost of pumping. this difficulty can be met by using a carefully selected mix of materials in making the pipe, and by making the joints carefully. infiltration through concrete diminishes rapidly after the sewer is in use; it occurs in vitrified pipe, also, to some extent. the house connection drain adopted in monterrey, with the disconnecting trap, is very much like one which the writer has seen introduced with very bad result. these are being removed as rapidly as possible by one of his clients, a sewerage company, in the southern states. it has been a fruitful cause of stoppages and bad smells; the ordinary method now in general use is much better. in the design shown, it would seem that there may even be some danger that the ventilation of the sewer by the stand-pipes in the streets may force the traps. one is rather surprised to learn that the main outfall sewer is designed with a capacity of 90,000,000 liters per day, the present sewage being estimated as not more than 18,000,000 liters, and the far future being thought to require only 40,000,000 liters. why this excessive size? possibly the surplus water which it is to carry is to be discharged into the sewers from the water supply system direct, and is intended for irrigating the land at the disposal area, when the sewage is insufficient for this purpose. the author states that all surface water is strictly excluded. the method of sewage disposal gives rise to several questions. it is proposed to use an extensive area for growing crops, which are to be irrigated with sewage. the paper states that the underlying strata at monterrey contain numerous caverns, and the first question is: what will be the effect on the water supply of other towns lower down the valley? the writer recollects a serious outbreak of typhoid fever in bluefield, w. va., caused by the pollution of the water in similar strata finding its way through unknown underground caverns and channels to the city's water supply. the next question is: what crops will be grown? it is a well-known fact that vegetables grown by the use of sewage as a fertilizer, are unsafe in a raw state for human consumption. this is well-known to european travelers in china and japan, where the use of fecal matter as fertilizer renders the various water supplies (where not filtered and disinfected) and all green vegetables, unsafe, on account of typhoid germs. moreover, crops not intended for human consumption, which are grown on lands irrigated by sewage bearing typhoid germs, etc., are unsafe for men to handle; even to store them may cause a dissemination of disease. it is evident, therefore, that the whole sewage flow should be in some manner disinfected at least, if not filtered, before it is used. the method of sewage disposal and the use of merely settled septic sewage for irrigation seem to be open to objection. the disposal plant is not sufficiently effective to meet the present requirements of sanitary science; and the sludge-pit will be certain to breed a pest of flies, if it is not also an intolerable nuisance on account of foul smells. monterrey would seem to be a proper place for the introduction of the imhoff tank, with percolating filters, and a final settling tank, the effluent being disinfected, before entering the latter tank. the flow might then be used safely for irrigation purposes for crops not to be eaten uncooked by man. the writer does not see how the method provided can possibly fulfill the object stated, to distribute on the land an effluent which will be "innocuous and clear," or how any consequential degree of purification can be obtained in the tanks provided. while there are described in this paper many things to find fault with, there are also many things to commend. the water supply system, with its reservoirs, etc., seems to be admirable; and the methods of construction by which the expense for forms was reduced is very interesting. the parking and ornamentation of the grounds over the reservoir roofs cannot fail to benefit the people and popularize the work. rudolf meyer, m. am. soc. c. e. (by letter).--the writer, as engineer for the government (guaranteeing the concessionaires a gross return of 10% per annum on the capital invested), and as inspector of the various works has had exceptional opportunities to become acquainted, not only with their construction, but also with events leading up to the granting of the final concession under which they were built and will be extended. in order to judge of the extent to which the different engineers, in their turn contributed toward the design of these works, the writer has thought it desirable to submit a complete statement of all matters relating to the inception, investigations, surveys, tests, etc., previous to the adoption of the present plans. data regarding former investigations, plans, and concessions which have since lapsed, have been obtained from the government archives. these refer to periods prior to mr. conway's engagement, and anterior to the retaining of mr. schuyler by the concessionaires, and mr. binckley's connection with the scheme, and they are presented here as complementary to the information in the paper. samuel m. gray, m. am. soc. c. e., acting in the interest of some american capitalists (who had been induced by col. j. a. robertson, of monterrey, to look into the merits of a concession acquired by him, for building these works), being guided by the government's proposition to supply the city with water by damming the flood-waters of the santa catarina river in the narrow gorge through which the stream emerges from the sierras, some eight miles from the city, had several soundings made and reservoir sites surveyed in the first two box cañons up the river, and prepared and presented to the government several alternative projects, besides the one mentioned by mr. schuyler. several different dam sites were designated by mr. gray, whose investigations extended over some two years, and were finally abandoned after he had designed the general outlay for a complete network of water mains and sewers for the city, on account of the unwillingness of the government at that time, about 1897, to grant any guaranties as to bonds or income to the concessionaire or his assigns. mr. gray did not favor the general scheme of storing flood-waters as a water supply, but strongly recommended to the attention of the government the greater advantages of deriving the supply from subterranean flow in the river, by an infiltration gallery driven into the water-bearing gravels in the santa catarina cañon (only a short distance above the place where mr. binckley afterward established his bore-holes across the river). he proposed to take advantage of the steep slope of the river at a turn in the cañon, and from the lower end drive a tunnel through a projecting rock spur, which tunnel, though starting well above the ordinary reach of floods, would terminate in water-bearing gravel, at a sufficient depth below the surface of the river-bed to intercept part of the underflow. mr. gray, through investigations made under his direction, by nathaniel turner, m. am. soc. c. e., had ascertained that there was an abundant subterranean flow, and work had actually been started on the proposed tunnel. the results of mr. gray's investigations were put at the disposal of messrs. mackenzie, mann & co. by mr. robertson, at whose offices mr. binckley prepared the first plans submitted by him for the approval of the government. after mr. gray's investigations, messrs. mackin and dillon (f. h. dillon, assoc. m. am. soc. c. e.), under contract with the government, prepared the following plans: for a dam in the santa catarina cañon; for a pipe line, similar to the one proposed by mr. gray, to a reservoir and settling basin on the left bank of the river (a short distance above where the provisional pumping station was established afterward by mr. binckley), but on the flat above the bluff skirting the river, practically at the same elevation as the present high-pressure reservoirs; for a complete network of water mains and sewers in the city, indicating the approximate direction in which the sewage would be disposed of, either by turning it into the river or by spreading it over suitable lands, the location of which was to be determined later; and also a complete set of specifications. on these data bids were invited by publication, and inquiries were received from several parties. finally, messrs. stocker and walker, of scranton, pa., entered into negotiations with the government, and the present concession was agreed upon and granted. messrs. stocker and walker engaged the late e. sherman gould, m. am. soc. c. e., to prepare a plan for a storage dam in the santa catarina cañon, and submitted plans for water distribution and sewers in the city, slightly modifying the original plans of messrs. mackin and dillon. in the fall of 1905, the concession was acquired by messrs. mackenzie, mann & co., of toronto, canada, together with all plans, etc., presented by the original concessionaires. the new concessionaires stated that they would examine the whole situation again, for the purpose of presenting modified plans for works. mr. schuyler, in the interest of the new owners, had paid one flying visit to monterrey when mr. gray's projects were brought to his notice, and the writer had an opportunity to show him the tunnel which had been started. mr. schuyler left for brazil and did not return until february, 1906, when he was accompanied by the chief engineer appointed by the concessionaires. messrs. schuyler and binckley then prepared plans for the water distribution and sewer systems in the city and for a provisional water supply to be pumped at san geronimo, some two miles up the river. the new plans for the city work followed closely the general disposition by mr. gray, the principal difference being that the main reservoirs for the permanent water supply were located to the south instead of to the west. this change was due to the results of an investigation, made during mr. schuyler's absence in brazil, by mr. f. s. hyde, late hydraulic engineer of the necaxa water power plant, who, accompanied by the writer, visited the whole water-shed of the santa catarina river in october, 1905, in search of suitable dam sites and prospects of power development. mr. hyde extended his studies to the santiago cañon, southeast of the city, recommending finally that the water be brought from that cañon, and that wells be dug in different points of the santa catarina river between san geronimo and the entrance of the cañon, and tested by pumping, for the purpose of establishing levels and ascertaining the available amount of underflow, with a view of determining the location for an infiltration gallery high enough up the river to permit of a gravity delivery and under good pressure in the city. in view of mr. hyde's report, and as the result of a visit to the santiago cañon, mr. schuyler decided to locate the reservoirs south of the town, intending to bring in water from the southeast, from springs in the santiago cañon, and also by infiltration from santa catarina, his and mr. binckley's scheme of water supply being for the same pressure throughout the city. to supply water during construction, and partly meet the demands of the city, mr. binckley, on his arrival, decided to establish a provisional pumping station at the well in the river nearest to town, started by direction of mr. hyde at san geronimo. this well was situated within the bed of inundation of high floods, on a low bank, at the foot of a conglomerate bluff some 20 ft. high, limiting a flat which was above the reach of any flood. it was on the same side of the river as the city, and there was plenty of good ground on the flat above for the establishment of a reservoir. a slightly shorter pipe line was secured by crossing the river, building the reservoir (a substantial concrete-lined and vaulted-over structure) on the opposite bank, laying out the pipe line to follow that bank nearly to the city, and finally crossing back again; but the result has been that since the flood of august, 1909, in which the river crossings were destroyed, the reservoir remains isolated on the other side of the river from town, though intended to form part of the permanent works and act as a compensating reservoir for equalizing the pressure of the high-pressure system. fortunately, the pumping station, the larger pumps, and the boilers, had been moved up the bank (after a rapid rise in the river on august 10th, 1909) to the new wells established by mr. conway on the line of the proposed prolongation of the infiltration gallery. the reservoir, however, is left to stand alone on the other side of the river, and its usefulness will not be restored until a new line is laid across the river, re-establishing its connection with the new pump line and the new and permanent pipe line to be laid along the north bank from the pumping station to the city. this will free monterrey from the constant menace of a water famine. at present its two main water supplies may be cut off by unexpected floods like those of 1909 and 1910, as both supplies are carried across the river, and though only the cast-iron pipe connecting with the water supply from estanzuela was carried away by the flood, the concrete conduit of the san geronimo low-pressure supply was seriously threatened. such risks are too great to be carried for any length of time; besides, a succession of dry years would cause such a reduction in the estanzuela supply as to require an additional reserve in the way of pumping stations drawing on the under-flow of the river, such as already exists in san geronimo. afterward, messrs. schuyler and binckley submitted preliminary plans and profiles for the projected concrete gravity conduit from estanzuela to the reservoir south of the city, and mr. binckley submitted excavation plans for two reservoirs, only one of which was built, and from designs by mr. conway. stephen e. kieffer, m. am. soc. c. e., was intrusted by mr. binckley with the revision of the plans of the water distribution and sewers. the southern half was approved by the government and executed according to his plans; the northern part was afterward revised by mr. conway and has been partly built. the final maturing of the project of an infiltration gallery in san geronimo as a low-pressure gravity supply, the division of the city into highand low-pressure districts corresponding to the two supplies, with one reservoir, instead of two to the south of the city, and the other to the west at the obispado, the entire details of both these gravity schemes, and of the whole sewage disposal scheme, as well as the modification introduced into the city work for the northern half, are unquestionably due to mr. conway, independently of the general views which may have been held on those points by other engineers. in march, 1910, mr. conway left monterrey, all the principal works being finished. since that time vicente saucedo, assoc. m. am. soc. c. e., has put in many additional water mains and sewers in the northern part of the city, and is finishing the _force majeure_ work caused by the destruction wrought in the districts along the river banks by the extraordinary floods. the writer, having had an opportunity to watch the earnest efforts of the several engineers connected with these works, in the course of their design and construction, resulting without doubt in being the first of their kind built in mexico, has been induced to contribute this discussion in order to bring out clearly the share of each. mr. pitkethly's apprehensions as to the adequacy of the system of ventilation adopted have not been realized, in part perhaps because the houses, though generally of only one story, have such high ceilings that the tops of their vent pipes are generally higher than the ventilating columns at the heads of the branch sewers. george robert graham conway, m. am. soc. c. e. (by letter).--the writer regrets that some features of the works described in this paper have failed to call forth the many useful criticisms which he expected, and his remarks, therefore, are limited to the few points which have been raised. he is particularly indebted to messrs. schuyler, meyer, and saucedo for adding supplementary information of value to the paper, but regrets that he cannot support mr. binckley in his claim that "the entire general design of the system, as well as the extensive hydrological studies and final selection of the sources of water supply, was completed in 1906," etc. on may 1st, 1907, when the writer assumed responsibility as chief engineer, he was unfortunately confronted with the fact that very little data and only a few preliminary and incomplete plans were available. his first duty was to report upon the final sources of supply, and the recommendations made in his report (dated july 12th), received mr. (now sir william) mackenzie's approval during the same month. the final plans, upon which the approval of the state government was definitely obtained, were prepared by the writer during the summer of 1907, were submitted to the governor of the state, gen. bernard reyes, on october 19th, and received his approval on december 12th, 1907. no works, with a long preliminary history, such as those at monterrey, can rightly be said to be due to any one individual; many engineers contributed to the final result, and the writer willingly acknowledges his indebtedness to the able men, who, for ten years prior to the construction of the works, investigated the particular problems which were met--problems which were not only of an engineering and physical nature, but racial and financial. the responsibility of constructing the works in their present form, and leaving them practically complete, did, however, fall on the writer's shoulders. messrs. pitkethly and hammond have criticized the basis of the calculations upon which the sewer system was laid down. in considering this problem, it is necessary to remember that, in designing this system, there was practically no information upon which to base the calculations; and the writer believed that the wisest course was to anticipate a liberal growth, and provide a large margin of safety. in designing a sewer system in older and well-established communities, the engineer is generally able to compile considerable information regarding the probable sewage flow for which it is necessary to provide. in monterrey this quantity was absolutely unknown. the writer's practice in other places has been to assume that about 8% of the total daily discharge of sewage will flow off in one hour; and, from many curves which he has plotted regarding sewage flow in british towns, this rate appears to him to be approximately correct. in monterrey, however, the old mexican traditions are rapidly changing, and the city is now becoming one of the most americanized in mexico; the old one-story houses will give way in time to buildings of several stories--a change, already noticeable, which has occurred during the past few years, particularly in the business portion of the city. taking these facts into consideration, it is believed that it would be, not only bad engineering, but bad business, for a company whose concession lasts 99 years, to provide sewers as small as 6 in., as mr. hammond would recommend, and then be called upon, under the terms of the concession, to relay larger sewers at a future date, thus incurring further capital expenditure upon which no government guaranty would apply, and no further revenue be obtained. in matters of this kind, not only the engineering, but the commercial, aspect of the question must be kept in view, and this point, the writer must frankly admit, he has always seriously considered. the writer's experience with reference to the method of ventilating sewers by tall columns extends over many years, and he still maintains that no other system gives such satisfactory results. in this view he finds considerable support in a recent paper on "salisbury drainage," by mr. w. j. e. binnie,[11] written since the system at monterrey was installed, in which the result of a series of experiments carried on during 1906-07 are given. at salisbury, england, 68 ventilators, 6 in. in internal diameter, 30 ft. high, were connected to the main sewer by 6-in. stoneware pipes. they were placed about 540 ft. apart, and, from careful anemometer readings, the following conclusions were reached: [11] _minutes of proceedings_, inst. c. e., vol. clxxxi, p. 317. "(1) that four ventilators all lying in the lower portion of the town acted sometimes as air-inlets and sometimes as air-outlets, and that the other sixty-four acted as air-outlets. "(2) that the average velocity of the air escaping up these columns was 3.2 feet per second, representing the circulation of 3,600,000 cubic feet of air per diem, or sufficient to change the air in the sewers every 10 minutes. "(3) that the average velocity of the current of air in the ventilating-column increases with the size of the sewer to which it is connected, averaging 2.4 feet per second with the 7-inch sewer, 3.6 feet per second with the 9-inch sewer, 3.7 feet per second with the 12-inch sewer, and 4.1 feet per second with the 15-inch sewer in these experiments. "(4) that the draught in the column is very largely dependent on the wind, being at its minimum on a still day, and could therefore be readily increased by the use of a suitable cowl. "(5) that the draught is very little affected by the sewer-gradients. it was expected that, in ventilating-columns placed in connection with the upper end of a sewer laid at a steep gradient, a strong draught would have been obtained. no direct connection, however, was traceable." as the result of these experiments, mr. binnie rightly came to the conclusion that this system of ventilation was efficient. mr. hammond anticipates that the house connection trap system at monterrey will lead to bad results, but the writer has seen the system at work in many widely different cities with excellent results. he believes that it is in accord with the best practice of the most eminent sanitarians during the last 20 years, and has no apology to make for introducing that system in monterrey. regarding mr. hammond's summary of the advantages of concrete pipes for sewer construction, the writer is in entire agreement, and would willingly have introduced them throughout the whole of the monterrey system, but for the fact that it was an exceedingly difficult matter to obtain suitable sand for their manufacture during the early days of construction, and considerable delays would have arisen if a complete network of such pipes had been used. his later experience at monterrey, when the sand difficulty had been solved, clearly showed that concrete pipe could be laid down at much less expense than fire clay. both mr. pitkethly and mr. hammond refer to the system of liquefying tanks used at monterrey preparatory to turning the sewage on the irrigation lands, and both express doubts as to their efficiency. the writer is now separated from his library and notes by many thousands of miles, and cannot quote "chapter and verse" as accurately as he would like, in order to support his views that the system adopted was adequate for dealing with a system such as that at monterrey. it must be pointed out that not only was it intended to prevent the sewage from becoming a nuisance, but that the sewage flow plus a large quantity of surplus water was intended to be used profitably for irrigation purposes. with that object, the company--or rather its allied company, the monterrey railway, light, and power company--obtained the control of 2,246 acres of the very finest arable land, with almost perfect natural drainage conditions, so that this land could be utilized to create a profitable revenue from the use of the sewage. the outfall sewer was accordingly designed to carry sufficient water and sewage to irrigate about 2,500 acres of land, which area could be considerably extended if necessary at any future time. most authorities now agree that before turning sewage upon land, a preliminary treatment is required to remove as much as possible of the suspended matter, and then reduce the latter by subsidence in liquefying or septic tanks, so that the quantity remaining in the effluent is so small and finely divided that it may be readily decomposed and oxidized by bacterial action without risk of clogging the surface or interstices of the land upon which it may discharge.[12] [12] see raikes, "sewage disposal works," pages 97-98. mr. pitkethly quotes messrs. watson and o'shaughnessy as saying, in their evidence before the royal commission on sewage disposal, that not more than 10% of the solids are digested in septic tanks, but it must be remembered that in many other places evidence was given before the same commission showing that from 25 to 30% was actually obtained. mr. j. d. watson, in his paper, "birmingham sewage-disposal works,"[13] read in march, 1910, points out that: [13] _minutes of proceedings_, inst. c. e., vol. clxxxi, p. 259. "the much-maligned sewage-farm still may be allowed (where the conditions are favourable) to rank as one of the best methods of sewage-disposal. diverse opinions may be held as to what are favourable conditions, particularly as conditions are sure to vary widely with locality; but it may be assumed that where there is 1 acre of suitable land per 100 persons, as in berlin and several other important cities, the efficiently-worked sewage-farm, when judged solely by the standard of the effluent produced, is still in the front rank. effluents from such a farm are remarkable for their paucity of micro-organisms, their low albuminoid ammonia, and their unvarying character." assuming that not more than 2,000 acres of the irrigated land at monterrey were available for sewage purposes, this area would represent the sewage treatment of the present population of not more than 45 persons per acre, and on the basis of the design, that is, for a population of 200,000 persons, this represents not more than 100 persons per acre. in many sewage farms on the continent of europe, the number treated per acre varies between 80 and 200 persons; for example, at breslau it is 187, at berlin 105, at brunswick 88, and at steglitz 185. regarding the crops to be grown on the land, very satisfactory results were obtained from growing indian corn, and two excellent crops per annum were taken from an area of 500 acres during the period in which the writer was responsible for the works. it was also his intention to grow alfalfa, and turn a part of the land into a pecan grove, and, although he does not share the apprehensions of danger of either mr. pitkethly or mr. hammond as to growing root crops, he believes the growth of alfalfa, indian corn, oats, barley, and pecan and fruit trees is eminently suitable for the land, which is a deep rich loam, from 4 to 8 ft. deep, overlying the "sillar" formation referred to in the paper. the writer has seen many sewage farms during the last 18 years, upon which root crops of excellent quality have been grown, and not the least suspicion has ever been raised regarding their use. in reference to the adoption of the monolithic form for constructing the south reservoir, the writer is so convinced as to its economy that had he to build this reservoir again, he would adopt the same method. mr. binckley, in drawing attention to the method of construction, has overlooked the fact that the cost of forms for a reservoir 30 ft. deep was a very serious item, and warranted the adoption of this new method, not only on account of economy but because of rapidity of construction; while, in the case of the obispado reservoir, which is very much shallower, simpler forms could be and were adopted. mr. saucedo's remarks regarding the repetition of the extraordinary floods of august, 1909, in september, 1910, are particularly interesting, and show how abnormal conditions are in so dry a section of mexico as the state of nuevo león. these two floods, the writer believes, are among the most instructive in north america, particularly when one remembers that prior to 1909 the average rainfall during a period of 15 years, was less than 22 in. per annum. table 18.--comparison of volume of floods, etc. +------------------------------+-----------+----------+-------+--------+ | | | maximum |cu. ft.| annual | | | drainage | recorded | /sec. | amount | | river. | area, in | flow, in | per | of | | | square | cu. ft. |square | rain| | | miles. | per sec. | mile. | fall. | +------------------------------+-----------+----------+-------+--------+ | santa catarina, monterrey, | | | | | | august 27th, 1907 | 544 | 235,000 | 432 | 22 | | estanzuela, near monterrey, | | | | | | august 28th, 1909 | 3.5 | 2,900 | 825 | 25 | | tansa, india | 52.5 | 35,000 | 666.7 | 101 | | krishna, india | 345 | 118,000 | 342.6 | 258 | | coquitlam river, vancouver | 100 | 12,000 | 120 |147-189 | | sweetwater, cal. | 186 | 18,150 | 99 | ... | | delaware, lambertville, n. j.| 6,820 | 250,000 | 36.5 | 45 | | colorado, austin, tex. | 37,000 | 123,000 | 3.3 | 24.5 | | ohio, cairo, ill. | 214,000 | 700,000 | 3.3 | 54.9 | +------------------------------+-----------+----------+-------+--------+ table 18, compiled by the writer, shows how very extreme the floods of 1909 were compared with those on other rivers, while those of 1910, referred to by mr. saucedo, although not so great, would appear to have reached a rate of flow of about 300 cu. ft. per sec. per sq. mile of the drainage area. the writer agrees with mr. saucedo that in the semi-arid regions of mexico and the southern states, and also in india, the possibility of these abnormal floods is an important consideration in the design of hydraulic works. * * * * * changes to this document transcriber's note: the table of contents has been added. blank pages have been deleted. illustrations may have been moved. discovered publisher's punctuation errors have been corrected. some wide tables have been re-formatted to narrower equivalents with some words replaced with commonly known abbreviations and possibly a key. some ditto marks have been replaced with the words represented. in addition, the following changes or corrections were made: p. 501: but the tampers had had[del 2nd had] previous experience p. 508: shown on plates vi to ix[vi, vii, viii, ix[to accomodate links]] p. 516: at this place there is a considererable[considerable] area p. 538: based on the following rates and and[del 2nd and] percentages p. 579: by crossing the river, build-the[building the] reservoir p. 550: [for table 14: added "total materials cost"] p. 566: respectively (fig. 5)[(fig. 4)], together with lack of p. 584: [table 17 renamed to table 18 to avoid duplication.] p. 584: table 17[18], compiled by the writer, shows how very extreme * * * * * available by internet archive (https://archive.org) note: project gutenberg also has an html version of this file which includes the numerous original illustrations. see 45703-h.htm or 45703-h.zip: (http://www.gutenberg.org/files/45703/45703-h/45703-h.htm) or (http://www.gutenberg.org/files/45703/45703-h.zip) images of the original pages are available through internet archive. see https://archive.org/details/presentpracticeo00sponuoft transcriber's note: text enclosed by underscores is in italics (_italics_). text enclosed by equal signs is in bold face (=bold=). small capitals have been changed to all capitals. [v] and [t] symbols represent sans-serif characters in the original text. sinking and boring wells. [illustration: boring shear frame.] water supply. the present practice of sinking and boring wells; with geological considerations and examples of wells executed. by ernest spon, member of the society of engineers; of the franklin institute; of the iron and steel institute; and of the geologists' association. [illustration: ornate monogram.] london: e. & f. n. spon, 48, charing cross. new york: 446, broome street. 1875. contents. chap. page preface. v. i. geological considerations. 1 ii. the new red sandstone. 35 iii. well sinking. 40 iv. well boring. 60 v. american tube well. 81 vi. well boring at great depths. 85 vii. examples of wells executed, and of districts supplied by wells. 155 viii. tables and miscellaneous information. 202 index. 211 e. & f. n. spon's new books. advertisements preface. in modern times the tendency of the inhabitants of a country to dwell together in large communities, and the consequent need for accumulating in a particular locality a sufficient supply of water for household, social, and industrial purposes, have rendered necessary the construction of such engineering works as impounding reservoirs and wells, by means of which the abundant measure of sparsely populated districts may be utilized, and water obtained not only free from those impurities which it collects in densely populated districts, but also in greater quantity than the natural sources of the district are capable of supplying. of the works mentioned, wells have fairly a primary claim upon the notice of the sanitary engineer, for, without undervaluing other sources of supply, the water from them certainly possesses the advantage over that from rivers and surface drainage, of being without organic admixture and unimpregnated with those deadly spores which find their way into surface waters and are so fatal in seasons of epidemic visitation. a great deal of the irregularity in the action of wells, and the consequent distrust with which they are regarded by many, is attributable either to improper situation or to the haphazard manner in which the search for underground water is frequently conducted. as regards the first cause, it cannot be too strongly stated that extreme caution is necessary in the choice of situations for wells, and that a sound geological knowledge of the country in which the attempt is to be made should precede any sinking or boring for this purpose, otherwise much useless expense may be incurred without a chance of success. indeed, the power of indicating those points where wells may, in all probability, be successfully established, is one of the chief practical applications of geology to the useful purposes of life. two cases in point are before me as i write; in the one 15,000_l._ has been spent in sinking a shaft and driving headings which yield but little water, found abundantly at the same depth in a mine adjoining; and in the other a town would be, but for its surface wells, entirely without water, the waterworks having been idle for weeks, and the sinkers are feebly endeavouring to obtain water by deep sinkings, in a position where its occurrence in any quantity is physically impossible. ample supplies could be obtained in both these cases by shifting the situation a few hundred yards. the subject-matter of the following pages is divided into chapters which treat of geological considerations, the new red sandstone, well sinking, well boring, the american tube well, well boring at great depths, and examples of wells executed and of localities supplied respectively, with tables and miscellaneous information. each system with its adjuncts has been kept complete in itself, instead of separating the various tools and appliances into classes, the plan adopted in the most approved french and german technical works. this, however, when too rigidly adhered to, as is the case with german works in particular, renders it troublesome for even a practised engineer to grasp a strange system in its entirety, while the pupil is wearied and retarded in his reading by an over-elaborate classification. it may, perhaps, be remarked that undue prominence has been given to the tertiary and cretaceous formations, but it is urged in extenuation that they happen to underlie two of the most important cities in europe, and that they have, in consequence, received a more thorough investigation than has been accorded to other districts. the records of wells in many formations are singularly scanty and unreliable, but it is hoped that the time is not far distant when the water-bearing characteristics of strata, such as the new red sandstone and permian, will receive proper attention, and that correct official records of well-work will be found in every locality, as this alone can rescue an important branch of hydraulic engineering from the charge of empiricism. in the course of the work the writings of g. r. burnell, c.e., baldwin latham, c.e., m. dru, emerson bainbridge, c.e., g. c. greenwell, and other well known authorities, have been freely referred to, particular recourse having been had to the works of professor prestwich, f.g.s. i am indebted to geo. g. andré, c.e., f.g.s., messrs. s. baker and son, and messrs. t. docwra and son, for many suggestions and much valuable information; to messrs. docwra special thanks are due for some of the important sections illustrating chapter vii. any claim to attention the book may deserve is based upon its being an attempt to embody, in a collected form, facts and information derived from practice, or from various sources not accessible to the majority of those engaged in the superintendence, or otherwise interested in the construction of wells. ernest spon. 16, craven street, charing cross, _june, 1875_. sinking and boring wells. chapter i. geological considerations. nearly every civil engineer is familiar with the fact that certain porous soils, such as sand or gravel, absorb water with rapidity, and that the ground composed of them soon dries up after showers. if a well be sunk in such soils, we often penetrate to considerable depths before we meet with water; but this is usually found on our approaching some lower part of the porous formation where it rests on an impervious bed; for here the water, unable to make its way downwards in a direct line, accumulates as in a reservoir, and is ready to ooze out into any opening which may be made, in the same manner as we see the salt water filtrate into and fill any hollow which we dig in the sands of the shore at low tide. a spring, then, is the lowest point or lip of an underground reservoir of water in the stratification. a well, therefore, sunk in such strata will most probably furnish, besides the volume of the spring, an additional supply of water. the transmission of water through a porous medium being so rapid, we may easily understand why springs are thrown out on the side of a hill, where the upper set of strata consist of chalk, sand, and other permeable substances, whilst those lying beneath are composed of clay or other retentive soils. the only difficulty, indeed, is to explain why the water does not ooze out everywhere along the line of junction of the two formations, so as to form one continuous land-soak, instead of a few springs only, and these oftentimes far distant from each other. the principal cause of such a concentration of the waters at a few points is, first, the existence of inequalities in the upper surface of the impermeable stratum, which lead the water, as valleys do on the external surface of a country, into certain low levels and channels; and secondly, the frequency of rents and fissures, which act as natural drains. that the generality of springs owe their supply to the atmosphere is evident from this, that they vary in the different seasons of the year, becoming languid or entirely ceasing to flow after long droughts, and being again replenished after a continuance of rain. many of them are probably indebted for the constancy and uniformity of their volume to the great extent of the subterranean reservoirs with which they communicate, and the time required for these to empty themselves by percolation. such a gradual and regulated discharge is exhibited, though in a less perfect degree, in all great lakes, for these are not sensibly affected in their levels by a sudden shower, but are only slightly raised, and their channels of efflux, instead of being swollen suddenly like the bed of a torrent, carry off the surplus water gradually. an artesian well, so called from the province of artois, in france, is a shaft sunk or bored through impermeable strata, until a water-bearing stratum is tapped, when the water is forced upwards by the hydrostatic pressure due to the superior level at which the rain-water was received. among the causes of the failure of artesian wells, we may mention those numerous rents and faults which abound in some rocks, and the deep ravines and valleys by which many countries are traversed; for when these natural lines of drainage exist, there remains only a small quantity of water to escape by artificial issues. we are also liable to be baffled by the great thickness either of porous or impervious strata, or by the dip of the beds, which may carry off the waters from adjoining high lands to some trough in an opposite direction,--as when the borings are made at the foot of an escarpment where the strata incline inwards, or in a direction opposite to the face of the cliffs. [illustration: effect of strata on artesian well. fig. 1.] [illustration: effect of a fault. fig. 2.] as instances of the way in which the character of the strata may influence the water-bearing capacity of any given locality, we give the following examples, taken from baldwin latham's papers on 'the supply of water to towns.' fig. 1 illustrates the causes which sometimes conduce to a limited supply of water in artesian wells. rain descending on the outcrop e f of the porous stratum a, which lies between the impervious stratum b b, will make its appearance in the form of a spring at s; but such spring will not yield any great quantity of water, as the area e f, which receives the rainfall, is limited in its extent. a well sunk at w, in a stratum of the above description, would not be likely to furnish a large supply of water, if any. the effect of a fault is shown in fig. 2. a spring will in all probability make its appearance at the point s, and give large quantities of water, as the whole body of water flowing through the porous strata a is intercepted by being thrown against the impermeable stratum b. permeable rock intersected by a dyke and overlying an impermeable stratum is seen in fig. 3. the water flowing through a, if intersected by a dyke d, will appear at s in the form of a spring, and if the area of a is of large extent, then the spring s will be very copious. as to the depth necessary to bore certain wells, in a case similar to fig. 4, owing to the fault, a well sunk at a would require to be sunk deeper than the well b, although both wells derive their supply from the same description of strata. if there is any inclination in the water-bearing strata, or if there is a current of water only in one direction, then one of the wells would prove a failure owing to the proximity of the fault, while the other would furnish an abundant supply of water. [illustration: permeable rock intersected by a dyke. fig. 3.] it should be borne in mind that there are two primary geological conditions upon which the quantity of water that may be supplied to the water-bearing strata depends; they are, the extent of superficial area presented by these deposits, by which the quantity of rain-water received on their surface in any given time is determined; and the character and thickness of the strata, as by this the proportion of water that can be absorbed, and the quantity which the whole volume of the permeable strata can transmit, is regulated. the operation of these general principles will constantly vary in accordance with local phenomena, all of which must, in each separate case, be taken into consideration. [illustration: well depth either side of a fault. fig. 4.] the mere distance of hills or mountains need not discourage us from making trials; for the waters which fall on these higher lands readily penetrate to great depths through highly-inclined or vertical strata, or through the fissures of shattered rocks; and after flowing for a great distance, must often reascend and be brought up again by other fissures, so as to approach the surface in the lower country. here they may be concealed beneath a covering of undisturbed horizontal beds, which it may be necessary to pierce in order to reach them. the course of water flowing underground is not strictly analogous to that of rivers on the surface, there being, in the one case, a constant descent from a higher to a lower level from the source of the stream to the sea; whereas, in the other, the water may at one time sink far below the level of the ocean, and afterwards rise again high above it. for the purposes under consideration, we may range the various strata of which the outer crust of the earth is composed under four heads, namely: 1, drift; 2, alluvion; 3, the tertiary and secondary beds, composed of loose, arenaceous and permeable strata, impervious, argillaceous and marly strata, and thick strata of compact rock, more or less broken up by fissures, as the norwich red and coralline crag, the molasse sandstones, the bagshot sands, the london clay, and the woolwich beds, in the tertiary division; and the chalk, chalk marl, gault, the greensands, the wealden clay, and the hastings sand; the oolites, the has, the rhætic beds, and keuper, and the new red sandstone, in the secondary division; and 4, the primary beds, as the magnesian limestone, the lower red sand, and the coal measures, which consist mainly of alternating beds of sandstones and shales with coal. the first of these divisions, the drift, consisting mainly of sand and gravel, having been formed by the action of flowing water, is very irregular in thickness, and exists frequently in detached masses. this irregularity is due to the inequalities of the surface at the period when the drift was brought down. hollows then existing would often be filled up, while either none was deposited on level surfaces, or, if deposited, was subsequently removed by denudation. hence we cannot infer when boring through deposits of this character that the same, or nearly the same, thickness will be found at even a few yards' distance. in valleys this deposit may exist to a great depth, the slopes of hills are frequently covered with drift, which has either been arrested by the elevated surface or brought down from the upper portions of that surface by the action of rain. in the former case the deposits will probably consist of gravel, and in the latter, of the same elements as the hill itself. the permeability of such beds will, of course, depend wholly upon the nature of the deposit. some rocks produce deposits through which water percolates readily, while others allow a passage only through such fissures as may exist. sand and gravel constitute an extremely absorbent medium, while an argillaceous deposit may be wholly impervious. in mountainous districts springs may often be found in the drift; their existence in such formations will, however, depend upon the position and character of the rock strata; thus, if the drift cover an elevated and extensive slope of a nature similar to that of the rocks by which it is formed, springs due to infiltration through this covering will certainly exist near the foot of the slope. upon the opposite slope, the small spaces which exist between the different beds of rock receive these infiltrations directly, and serve to completely drain the deposit which, in the former case, is, on the contrary, saturated with water. if, however, the foliations or the joints of the rocks afford no issue to the water, whether such a circumstance be due to the character of their formation, or to the stopping up of the issues by the drift itself, these results will not be produced. it will be obvious how, in this way, by passing under a mass of drift the water descending from the top of hill slopes reappears at their foot in the form of springs. if now we suppose these issues stopped, or covered by an impervious stratum of great thickness, and this stratum pierced by a boring, the water will ascend through this new outlet to a level above that of its original issue, in virtue of the head of water measured from the points at which the infiltration takes place to the point in which it is struck by the boring. alluvion, like drift, consists of fragments of various strata carried away and deposited by flowing water; it differs from the latter only in being more extensive and regular, and, generally, in being composed of elements brought from a great distance, and having no analogy with the strata with which it is in contact. usually it consists of sand, gravel, rolled pebbles, marls or clays. the older deposits often occupy very elevated districts, which they overlie throughout a large extent of surface. at the period when the large rivers were formed, the valleys were filled up with alluvial deposits, which at the present day are covered by vegetable soil, and a rich growth of plants, through which the water percolates more slowly than formerly. the permeability of these deposits allows the water to flow away subterraneously to a great distance from the points at which it enters. springs are common in the alluvion, and more frequently than in the case of drift, they can be found by boring. as the surface, which is covered by the deposit, is extensive, the water circulates from a distance through permeable strata often overlaid by others that are impervious. if at a considerable distance from the points of infiltration, and at a lower level, a boring be put down, the water will ascend in the bore-hole in virtue of its tendency to place itself in equilibrium. where the country is open and uninhabited, the water from shallow wells sunk in alluvion is generally found to be good enough and in sufficient quantity for domestic purposes. the strata of the tertiary and secondary beds, especially the latter, are far more extensive than the preceding, and yield much larger quantities of water. the chalk is the great water-bearing stratum for the larger portion of the south of england. the water in it can be obtained either by means of ordinary shafts, or by artesian wells bored sometimes to great depths, from which the water will frequently rise to the surface. it should be observed that water does not circulate through the chalk by general permeation of the mass, but through fissures. a rule given by some for the level at which water may be found in this stratum is, "take the level of the highest source of supply, and that of the lowest to be found. the mean level will be the depth at which water will be found at any intermediate point, after allowing an inclination of at least 10 feet a mile." this rule will also apply to the greensand. this formation contains large quantities of water, which is more evenly distributed than in the chalk. the gault clay is interposed between the upper and the lower greensand, the latter of which also furnishes good supplies. in boring into the upper greensand, caution should be observed so as not to pierce the gault clay, because water which permeates through that system becomes either ferruginous, or contaminated by salts and other impurities. the next strata in which water is found are the upper and inferior oolites, between which are the kimmeridge and oxford clays, which are separated by the coral rag. there are instances in which the oxford clay is met with immediately below the kimmeridge, rendering any attempt at boring useless, because the water in the oxford clay is generally so impure as to be unfit for use. and with regard to finding water in the oolitic limestone, it is impossible to determine with any amount of precision the depth at which it may be reached, owing to the numerous faults which occur in the formation. it will therefore be necessary to employ the greatest care before proceeding with any borings. lower down in the order are the upper has, the marlstone, the lower has, and the new red sandstone. in the marlstone, between the upper and lower beds of the has, there may be found a large supply of water, but the level of this is as a rule too low to rise to the surface through a boring. it will be necessary to sink shafts in the ordinary way to reach it. in the new red sandstone, also, to find the water, borings must be made to a considerable depth, but when this formation exists a copious supply may be confidently anticipated, and when found the water is of excellent quality. every permeable stratum may yield water, and its ability to do this, and the quantity it can yield, depend upon its position and extent. when underlaid by an impervious stratum, it constitutes a reservoir of water from which a supply may be drawn by means of a sinking or a bore-hole. if the permeable stratum be also overlaid by an impervious stratum, the water will be under pressure and will ascend the bore-hole to a height that will depend on the height of the points of infiltration above the bottom of the bore-hole. the quantity to be obtained in such a case as we have already pointed out, will depend upon the extent of surface possessed by the outcrop of the permeable stratum. in searching for water under such conditions a careful examination of the geological features of the district must be made. frequently an extended view of the surface of the district, such as may be obtained from an eminence, and a consideration of the particular configuration of that surface, will be sufficient to enable the practical eye to discover the various routes which are followed by the subterranean water, and to predicate with some degree of certainty that at a given point water will be found in abundance, or that no water at all exists at that point. to do this, it is sufficient to note the dip and the surfaces of the strata which are exposed to the rains. when these strata are nearly horizontal, water can penetrate them only through their fissures or pores; when, on the contrary, they lie at right-angles, they absorb the larger portion of the water that falls upon their outcrop. when such strata are intercepted by valleys, numerous springs will exist. but if, instead of being intercepted, the strata rise around a common point, they form a kind of irregular basin, in the centre of which the water will accumulate. in this case the surface springs will be less numerous than when the strata are broken. but it is possible to obtain water under pressure in the lower portions of the basin, if the point at which the trial is made is situate below the outcrop. the primary rocks afford generally but little water. having been subjected to violent convulsions, they are thrown into every possible position and broken by numerous fissures; and as no permeable stratum is interposed, as in the more recent formations, no reservoir of water exists. in the unstratified rocks, the water circulates in all directions through the fissures that traverse them, and thus occupies no fixed level. it is also impossible to discover by a surface examination where the fissures may be struck by a boring. for purposes of water supply, therefore, these rocks are of little importance. it must be remarked here, however, that large quantities of water are frequently met with in the magnesian limestone and the lower red sand, which form the upper portion of the primary series. joseph prestwich, jun., in his 'geological inquiry respecting the water-bearing strata round london,' gives the following valuable epitome of the geological conditions affecting the value of water-bearing deposits; and although the illustrations are confined to the tertiary deposits, the same mode of inquiry will apply with but little modification to any other formation. the main points are-the extent of the superficial area occupied by the water-bearing deposit. the lithological character and thickness of the water-bearing deposit, and the extent of its underground range. the position of the outcrop of the deposit, whether in valleys or hills, and whether its outcrop is denuded, or covered with any description of drift. the general elevation of the country occupied by this outcrop above the levels of the district in which it is proposed to sink wells. the quantity of rain which falls in the district under consideration, and whether, in addition, it receives any portion of the drainage from adjoining tracts, when the strata are impermeable. the disturbances which may affect the water-bearing strata, and break their continuous character, as by this the subterranean flow of water would be impeded or prevented. extent of superficial area. to proceed to the application of the questions in the particular instance of the lower tertiary strata. with regard to the first question, it is evident that a series of permeable strata encased between two impermeable formations can receive a supply of water at those points only where they crop out and are exposed on the surface of the land. the primary conditions affecting the result depend upon the fall of rain in the district where the outcrop takes place; the quantity of rain-water which any permeable strata can gather being in the same ratio as their respective areas. if the mean annual fall in any district amounts to 24 inches, then each square mile will receive a daily average of 950,947 gallons of rain-water. it is therefore a matter of essential importance to ascertain, with as much accuracy as possible, the extent of exposed surface of any water-bearing deposit, so as to determine the maximum quantity of rain-water it is capable of receiving. the surface formed by the outcropping of any deposit in a country of hill and valley is necessarily extremely limited, and it would be difficult to measure in the ordinary way. prestwich therefore used another method, which seems to give results sufficiently accurate for the purpose. it is a plan borrowed from geographers, that of cutting out from a map on paper of uniform thickness and on a large scale, say one inch to the mile, and weighing the superficial area of each deposit. knowing the weight of a square of 100 miles cut out of the same paper, it is easy to estimate roughly the area in square miles of any other surface, whatever may be its figure. mineral character of the formation. the second question relates to the mineral character of the formation, and the effect it will have upon the quantity of water which it may hold or transmit. if the strata consist of sand, water will pass through them with facility, and they will also hold a considerable quantity between the interstices of their component grains; whereas a bed of pure clay will not allow of the passage of water. these are the two extremes of the case; the intermixture of these materials in the same bed will of course, according to their relative proportions, modify the transmission of water. prestwich found by experiment that a silicious sand of ordinary character will hold on an average rather more than one-third of its bulk of water, or from two to two and a half gallons in one cubic foot. in strata so composed the water may be termed free, as it passes easily in all directions, and under the pressure of a column of water is comparatively but little impeded by capillary attraction. these are the conditions of a true permeable stratum. where the strata are more compact and solid, as in sandstone, limestone, and oolite, although all such rocks imbibe more or less water, yet the water so absorbed does not pass freely through the mass, but is held in the pores of the rock by capillary attraction, and parted with very slowly; so that in such deposits water can be freely transmitted only in the planes of bedding and in fissures. if the water-bearing deposit is of uniform lithological character over a large area, then the proposition is reduced to its simplest form; but when, as in the deposit between the london clay and the chalk, the strata consist of variable mineral ingredients, it becomes essential to estimate the extent of these variations; for very different conclusions might be drawn from an inspection of the lower tertiary strata at different localities. [illustration: _a_ london clay, _b_ sands and clay, _c_ chalk. fig. 5.] in the fine section exposed in the cliffs between herne bay and the reculvers, in england, a considerable mass of fossiliferous sands is seen to rise from beneath the london clay. fig. 5 represents a view of a portion of this cliff a mile and a half east of herne bay and continued downwards, by estimation below the surface of the ground to the chalk. in this section there is evidently a very large proportion of sand, and consequently a large capacity for water. again, at upnor, near rochester, the sands marked 3 are as much as 60 to 80 feet thick, and continue so to gravesend, purfleet, and erith. in the first of these places they may be seen capping windmill hill; in the second, forming the hill, now removed, on which the lighthouse is built; and in the third, in the large ballast pits on the banks of the river thames. the average thickness of these sands in this district may be about 50 to 60 feet. in their range from east to west, the beds 2 become more clayey and less permeable, and 1, very thin. as we approach london the thickness of 3 also diminishes. in the ballast pits at the west end of woolwich, this sand-bed is not more than 35 feet thick, and as it passes under london becomes still thinner. [illustration: fig. 6. general section of strata below london.] fig. 6 is a general or average section of the strata on which london stands. the increase in the proportion of the argillaceous strata, and the decrease of the beds of sand, in the lower tertiary strata is here very apparent, and from this point westward to hungerford, clays decidedly predominate; while at the same time the series presents such rapid variations, even on the same level and at short distances, that no two sections are alike. on the southern boundary of the tertiary district, from croydon to leatherhead, the sands 3 maintain a thickness of 20 to 40 feet, whilst the associated beds of clay are of inferior importance. we will take another section, fig. 7, representing the usual features of the deposit in the northern part of the tertiary district. it is from a cutting at a brickfield west of the small village of hedgerley, 6 miles northward of windsor. [illustration: unusual deposit features 6 miles north of windsor. fig. 7.] here we see a large development of the mottled clays, and but little sand. a somewhat similar section is exhibited at oak end, near chalfont st. giles. but to show how rapidly this series changes its character, the section of a pit only a third of a mile westward of the one at hedgerley is given in fig. 8. [illustration: section of a pit. fig. 8.] in this latter section the mottled clays have nearly disappeared, and are replaced by beds of sand with thin seams of mottled clays. at twyford, near reading, and at old basing, near basingstoke, the mottled clays again occupy, as at hedgerley, nearly the whole space between the london clays and the chalk. near reading a good section of these beds was exhibited in the sonning cutting of the great western railway; they consisted chiefly of mottled clays. at the katsgrove pits, reading, the beds are more sandy. referring back to fig. 6, it may be noticed that there is generally a small quantity of water found in the bed marked 1, in parts of the neighbourhood of london. owing, however, to the constant presence of green and ferruginous sands, traces of vegetable matters and remains of fossil shells, the water is usually indifferent and chalybeate. the well-diggers term this a slow spring. they well express the difference by saying that the water creeps up from this stratum, whereas that it bursts up from the lower sands 3, which is the great water-bearing stratum. in the irregular sand-beds interstratified with the mottled clays between these two strata water is also found, but not in any large quantity. [illustration: section at pebble hill. fig. 9.] fig. 9 is a section at the western extremity of the tertiary district at pebble hill, near hungerford. here again the mottled clays are in considerable force, sands forming the smaller part of the series. the following lists exhibit the aggregate thickness of all the beds of sand occurring between the london clay and the chalk at various localities in the tertiary district. it will appear from them that the mean results of the whole is very different from any of those obtained in separate divisions of the country. the mean thickness of the deposit throughout the whole tertiary area may be taken at 62 feet, of which 36 feet consist of sands and 26 feet of clays; but as only a portion of this district contributes to the water supply of london, it will facilitate our inquiry if we divide it into two parts, the one westward of and including london, and the other eastward of it, introducing also some further subdivisions into each. measurement of sections eastward of london. +---------------------+-----+-----+ |southern boundary. |sand.|clay.| +---------------------+-----+-----+ | | ft. | ft. | |lewisham | 65 | 26 | |woolwich | 66 | 18 | |upnor | 80? | 8 | |herne bay | 70? | 50 | | | | | | | | | | | | | | | | | | +-----+-----+ | average | 70 | 25 | +---------------------+-----+-----+ +---------------------+-----+-----+ |northern boundary. |sand.|clay.| +---------------------+-----+-----+ | | ft.| ft. | |hertford | 26 | 3 | |beaumont green, | | | | near hoddesdon | 16 | 10 | |broxbourne | 28 | 2 | |gestingthorpe, | | | | near sudbury | 50?| ? | |whitton, | | | | near ipswich | 60?| 5 | | +-----+-----+ | average | 36 | 5 | +---------------------+-----+-----+ the mean of the three columns in two western sections gives a thickness to this formation of 57 feet, of which only 19 feet are sand and permeable to water, and the remaining 38 feet consist of impermeable clays, affording no supply of water. the area, both at the surface and underground, over which they extend is about 1086 square miles. measurement of sections westward of london. +--------------------------------------------+ | on or near the southern boundary | | of the tertiary district. | +--------------------------------+-----+-----+ | |sand.|clay.| | +-----+-----+ | | ft.| ft.| |streatham | 30 | 25 | |mitcham | 47 | 34 | |croydon | 35?| 20?| |epsom | 31 | 23 | |fetcham | 35 | 20 | |guildford | 10?| 40 | |chinham, near basingstoke | 20?| 30 | |itchingswell, near kingsclere | 22 | 34 | |highclere | 24 | 27 | |pebble hill, near hungerford | 9 | 39 | | | | | | | | | | | | | | +-----+-----+ | average | 26 | 29 | +--------------------------------+-----+-----+ +--------------------------------------------+ | on a central line in the | | tertiary district. | +--------------------------------+-----+-----+ | |sand.|clay.| | +-----+-----+ | sand.clay.| ft.| ft.| | ft. ft. | | | |london: | | | | millbank 49 40} | | | | trafalgar square 49 30} | | | | tottenham court road 35 30} | | | | pentonville 34 44} | 46 | 39 | | barclay's brewery 55 42} | | | | lombard street 53 35} | | | | the mint 49 38} | | | | whitechapel 45 50} | | | |garrett, near wandsworth | 20 | 52 | |isleworth | 17 | 70 | |twickenham | 7 | 50 | |chobham | 3 | 45 | | +-----+-----+ | average | 18 | 51 | +--------------------------------+-----+-----+ +--------------------------------------------+ | on or near the northern boundary | | of the tertiary district | +--------------------------------+-----+-----+ | |sand.|clay.| | +-----+-----+ | | ft.| ft.| |hatfield | 23 | 2 | |watford | 25 | 10 | |pinner | 12 | 32 | |oak end, chalfont st. giles | 3 | 40 | |hedgerley, near slough | 5 | 45 | |starveall, " " | 13 | 20 | |twyford | 5 | 60 | |sonning, near reading | 12 | 54 | |reading | 16 | 33 | |newbury | 20 | 36 | |pebble hill | 9 | 39 | | | | | | | | | | +-----+-----+ | average | 13 | 34 | +--------------------------------+-----+-----+ the average total thickness of the eastern district deduced from the nine sections we have taken gives 68 feet, of which 53 feet are sands and 15 feet clays. the larger area, 1849 square miles, over which the eastern portion of the tertiary series extends, and the greater volume of the water-bearing beds, constitute important differences in favour of this district; and if there had been no geological disturbances to interfere with the continuous character of the strata, we might have looked to this quarter for a large supply of water to the artesian wells of london. [illustration: a geological section. fig. 10.] from these tables it will be readily perceived that the strata of which the water-bearing deposits are composed are very variable in their relative thickness. they consist, in fact, of alternating beds of clay and sand, in proportions constantly changing. in one place, as at hedgerley, the aggregate beds of sand may be 5 feet thick, and the clays 45 feet; whilst at another, as at leatherhead, the sands may be 35, and the clays 20 feet thick, and some such variation is observable in every locality. but although we may thus in some measure judge of the capacity of these beds for water, this method fails to show whether the communication from one part of the area to another is free, or impeded by causes connected with mineral character. now as we know that these beds not only vary in their thickness, but that they also frequently thin out, and sometimes pass one into another, it may happen that a very large development of clay at any one place may altogether stop the transit of the water in that locality. thus in fig. 10 the beds of sand at y allow of the free passage of water, but at x, where clays occupy the whole thickness, it cannot pass; the obstruction which this cause may offer to the underground flow of water can only be determined by experience. it must not, however, be supposed that such a variation in the strata is permanent or general along any given line. it is always local, some of the beds of clay commonly thinning out after a certain horizontal range, so that, although the water may be impeded or retarded in a direct course, it most probably can, in part or altogether, pass round by some point where the strata have not undergone the same alteration. position and general conditions of the outcrop. this involves some considerations to which an exact value cannot at present be given, yet which require notice, as they to a great extent determine the proportion of water which can pass from the surface into the mass of the water-bearing strata. in the first place, when the outcrop of these strata occurs in a valley, as represented in fig. 11, it is evident that _b_ may not only retain all the water which might fall on its surface, but also would receive a proportion of that draining off from the strata of _a_ and _c_. this form of the surface generally prevails wherever the water-bearing strata are softer and less coherent than the strata above and below them. [illustration: water-bearing strata in a valley. fig. 11.] it may be observed in the lower tertiary series at sutton, carshalton, and croydon, where a small and shallow valley, excavated in these sands and mottled clays, ranges parallel with the chalk hills. it is apparent again between epsom and leatherhead, and also in some places between guildford and farnham, as well as between odiham and kingsclere. the southampton railway crosses this small valley on an embankment at old basing. this may be considered as the prevailing, but not exclusive, form of structure from croydon to near hungerford. the advantage, however, to be gained from it in point of water supply is much limited by the rather high angle at which the strata are inclined, as well as by their small development, which greatly restrict the breadth of the surface occupied by the outcrop. it rarely exceeds a quarter of a mile, and is generally very much less, often not more than 100 to 200 feet. the next modification of outcrop, represented in fig. 12, is one not uncommon on the south side of the tertiary district. the strata _b_ here crop out on the slope of the chalk hills, and the rain falling upon them, unless rapidly absorbed, tends to drain at once from their surface into the adjacent valleys. v, l, shows the line of valley level. [illustration: strata on slope of chalk hills. fig. 12.] this arrangement is not unfrequent between kingsclere and inkpen, and also between guildford and leatherhead. eastward of london it is exhibited on a larger scale at the base of the chalk hills, in places between chatham and faversham, a line along which the sands of the lower tertiary strata, _b_, are more fully developed than elsewhere. as, however, the surface of _b_ is there usually more coincident with the valley level, v, l, of the district, it is in a better position for retaining more of the rainfall. [illustration: chalk stratum at base of a hill. fig. 13.] a third position of outcrop, much more unfavourable for the water-bearing strata, prevails generally along the greater part of the northern boundary of the tertiary strata. instead of forming a valley, or outcropping at the base of the chalk hills, almost the whole length of this outcrop lies on the slope of the hills, as in fig. 13, where the chalk _c_ forms the base of the hill and the lower ground at its foot, whilst the london clay, _a_, caps the summit, thus restricting the outcrop of _b_ to a very narrow zone and a sloping surface. this form of structure is exhibited in the hills round sonning, reading, hedgerley, rickmansworth, and watford; thence by shenley hill, hatfield, hertford, sudbury; and also at hadleigh this position of outcrop is continued. if, as on the southern side of the tertiary district, the outcrop were continued in a nearly unbroken line, then these unfavourable conditions would prevail uninterruptedly; but the hills are in broken groups, and intersected at short distances by transverse valleys, as that of the kennet at reading, of the loddon at twyford, of the colne at uxbridge, and so on. between watford and hatfield there is a constant succession of small valleys running back for short distances from the lower district of the chalk, through the hills of the tertiary district. the valley of the lea at roydon and hoddesdon is a similar and stronger case in point. the effect of these transverse valleys is to open out a larger surface of the strata _b_ than would otherwise be exposed, for if the horizontal line, v, l, fig. 13, were carried back beyond the point _x_, to meet the prolongation of _b_, then these lower tertiary strata would not only be intersected by the line of valley level, but would form a much smaller angle with the plane v, l, and therefore spread over a larger area than where they crop out on the side of the hills. the foregoing are the three most general forms of outcrop, but occasionally the outcrop takes place wholly or partly on the summit of a hill, as, near the reculvers in the neighbourhood of canterbury, of sittingbourne, and at the addington hills, near croydon, in which cases the area of the lower tertiary is expanded. when the dip is very slight, and the beds nearly horizontal, the lower tertiary sands occasionally spread over a still larger extent of surface, as between stoke pogis, burnham common, and beaconsfield, and in the case of the flat-topped hill, forming blackheath and bexley heath, as in fig. 14. favourable as such districts might at first appear to be from the extent of their exposed surface, nevertheless they rarely contribute to the water supply of the wells sunk into the lower tertiary sands under london, the continuity of the strata being broken by intersecting valleys; thus the district last mentioned is bounded on the north by the valley of the thames, on the west by that of ravensbourne, and on the east by the valley of the cray; consequently the rain-water, which has been absorbed by the very permeable strata on the intermediate higher ground, passes out on the sides of the hills, into the surface channels in the valleys, or into the chalk. almost all the wells at bexley heath, for their supply of water, have, in fact, to be sunk into the chalk through the overlying 100 to 133 feet of sand and pebble beds, _b_. [illustration: section at blackheath and bexley heath. fig. 14.] thus far we have considered this question, as if, in each instance, the outcropping edges of the water-bearing strata, _b_, were laid bare, and presented no impediment to the absorption of the rain-water falling immediately upon their surface, or passing on to it from some more impermeable deposits. but there is another consideration which influences materially the extent of the water supply. if the strata _b_ were always bare, we should have to consider their outcrop as an absorbent surface, of power varying according to the lithological character and dip of the strata only. but the outcropping edges of the strata do not commonly present bare and denuded surfaces. thus a large extent of the country round london is more or less covered by beds of drift, which protect the outcropping beds of _b_, and turn off a portion of the water falling upon them. the drift differs considerably in its power of interference with the passage of the rain-water into the strata beneath. the ochreous sandy flint gravel, forming so generally the subsoil of london, admits of the passage of water. all the shallow surface springs, from 10 to 20 feet deep, are produced by water which has fallen on, and passed through, this gravel, _g_, fig. 15, down to the top of the london clay, _a_, on the irregular surface of which it is held up. [illustration: section through london subsoil. fig. 15.] when the london clay is wanting, this gravel lies immediately upon the lower tertiary strata, as in the valley between windsor and maidenhead, and in that of the kennet between newbury and thatcham, transmitting to the underlying strata part of the surface water. where beds of brick earth occur in the drift, as between west drayton and uxbridge, the passage of the surface water into the underlying strata is intercepted. sometimes the drift is composed of gravel mixed very irregularly with broken up london clay, and although commonly not more than 3 to 8 feet thick, it is generally impermeable. over a considerable portion of suffolk and part of essex, a drift, composed of coarse and usually light-coloured sand with fine gravel, occurs. water percolates through it with extreme facility, but it is generally covered by a thick mass of stiff tenacious bluish grey clay, perfectly impervious. this clay drift, or boulder clay, caps, to a depth of from 10 to 50 feet or more, almost all the hills in the northern division of essex, and a large portion of suffolk and norfolk. it so conceals the underlying strata that it is difficult to trace the course of the outcrop of the lower tertiary sands between ware and ipswich; and often, as in fig. 16, notwithstanding the breadth, apart from this cause of the outcrop of the tertiary sands, _b_, and of the drift of sand and gravel, 2, they are both so covered by the boulder clay, 1, that the small surface exposed can be of comparatively little value. [illustration: outcrop covered by boulder clay. fig. 16.] there are also, in some valleys, river deposits of silt, mud, and gravel. these are, however, of little importance to the subject before us. under ordinary conditions they are generally sufficiently impervious to prevent the water from passing through the beds beneath. height of water-bearing strata above surface of country. the height of the districts, wherein the water-bearing strata crop out, above that of the surface of the country in which the wells are placed, should be made the subject of careful consideration, as upon this point depends the level to which the water in artesian wells may ascend. again, taking the london district as an example, prestwich remarks that, as the country rises on both sides of the thames to the edge of the chalk escarpments, and as the outcrop of the lower tertiary strata is intermediate between these escarpments and the thames, it follows that the outcrop of these lower beds must, in all cases, be on a higher level than the thames itself, where it flows through the centre of the tertiary district. its altitude is, of course, very variable, as shown in the following list of its approximate height above trinity high water-mark at london. these heights are taken where the tertiaries are at their lowest level in the several localities mentioned. --------------------------------+------------------------ south of london. | north of london. --------------------------------+------------------------ croydon about 130 feet. | thetford about 200 feet. leatherhead " 90 " | watford " 170 " guildford " 96 " | slough " 60 " old basing " 250 " | reading " 120 " near hungerford " 360 " | newbury " 236 " --------------------------------+------------------------eastward of london these strata crop out at a gradually decreasing level. in consequence, therefore, of the outcrop of the water-bearing strata being thus much above the surface of the central tertiary district bordering the thames, the water in these strata beneath london tended originally to rise above that surface. as, however, these beds crop out on a level with the thames immediately east of the city between deptford, blackwall, and bow, the water, having this natural issue so near, could never have risen in london much above the level of the river. rainfall in the district where the water-bearing strata crop out. when inquiring into the probable relative value of any water-bearing strata, it is necessary to compare the rainfall in their respective districts. rain is of all meteorological phenomena the most capricious, both as regards its frequency and the amount which falls in a given time. in some places it rarely or never falls, whilst in others it rains almost every day; and there does not yet exist any theory from which a probable estimate of the rainfall in a given district can be deduced independently of direct observation. but although dealing with one of the most capricious of the elements, we nevertheless find a workable average in the quantity of rain to be expected in any particular place, if careful and continued observations are made with the rain-gauge. g. j. symons, the meteorologist, to whose continued investigations we are indebted for our most reliable data upon the subject of rainfall, gives the following practical instructions for using a rain-gauge;-"the mouth of the gauge must be set quite level, and so fixed that it will remain so; it should never be less than 6 inches above the ground, nor more than 1 foot except when a greater elevation is absolutely necessary to obtain a proper exposure. "it must be set on a level piece of ground, at a distance from shrubs, trees, walls, and buildings, at the very least as many feet from their base as they are in height. "if a thoroughly clear site cannot be obtained, shelter is most endurable from n.w., n., and e., less so from s., s.e., and w., and not at all from s.w. or n.e. "special prohibition must issue as to keeping all tall-growing flowers away from the gauges. "in order to prevent rust, it will be desirable to give the japanned gauges a coat of paint every two or three years. "the gauge should, if possible, be emptied daily at 9 a.m., and the amount entered against the previous day. "when making an observation, care should be taken to hold the glass upright. "it can hardly be necessary to give here a treatise on decimal arithmetic; suffice it therefore to say that rain-gauge glasses usually hold half an inch of rain (0·50) and that each 1/100 (0·01) is marked; if the fall is less than half an inch, the number of hundredths is read off at once, if it is over half an inch, the glass must be filled up to the half inch (0·50), and the remainder (say 0·22) measured afterwards, the total (0·50 + 0·22) = 0·72 being entered. if less than 1/10 (0·10) has fallen, the cipher must always be prefixed; thus if the measure is full up to the seventh line, it must be entered as 0·07, that is, no inches, no tenths, and seven hundredths. for the sake of clearness it has been found necessary to lay down an invariable rule that there shall always be two figures to the right of the decimal point. if there be only one figure, as in the case of one-tenth of an inch, usually written 0·1, a cipher must be added, making it 0·10. neglect of this rule causes much inconvenience. "in snow three methods may be adopted--it is well to try them all. 1. melt what is caught in the funnel, and measure that as rain. 2. select a place where the snow has not drifted, invert the funnel, and turning it round, lift and melt what is enclosed. 3. measure with a rule the average depth of snow, and take one-twelfth as the equivalent of water. some observers use in snowy weather a cylinder of the same diameter as the rain-gauge, and of considerable depth. if the wind is at all rough, all the snow is blown out of a flat-funnelled rain-gauge." a drainage area is almost always a district of country enclosed by a ridge or watershed line, continuous except at the place where the waters of the basin find an outlet. it may be, and generally is, divided by branch ridge-lines into a number of smaller basins, each drained by its own stream into the main stream. in order to measure the area of a catchment basin a plan of the country is required, which either shows the ridge-lines or gives data for finding their positions by means of detached levels, or of contour lines. when a catchment basin is very extensive it is advisable to measure the smaller basins of which it consists, as the depths of rainfall in them may be different; and sometimes, also, for the same reason, to divide those basins into portions at different distances from the mountain chains, where rain-clouds are chiefly formed. the exceptional cases, in which the boundary of a drainage area is not a ridge-line on the surface of the country, are those in which the rain-water sinks into a porous stratum until its descent is stopped by an impervious stratum, and in which, consequently, one boundary at least of the drainage area depends on the figure of the impervious stratum, being, in fact, a ridge-line on the upper surface of that stratum, instead of on the ground, and very often marking the upper edge of the outcrop of that stratum. if the porous stratum is partly covered by a second impervious stratum, the nearest ridge-line on the latter stratum to the point where the porous stratum crops out will be another boundary of the drainage area. in order to determine a drainage area under these circumstances it is necessary to have a geological map and sections of the district. the depth of rainfall in a given time varies to a great extent at different seasons, in different years, and in different places. the extreme limits of annual depth of rainfall in different parts of the world may be held to be respectively nothing and 150 inches. the average annual depth of rainfall in different parts of britain ranges from 22 inches to 140 inches, and the least annual depth recorded in britain is about 15 inches. the rainfall in different parts of a given country is, in general, greatest in those districts which lie towards the quarter from which the prevailing winds blow; in great britain, for instance, the western districts have the most rain. upon a given mountain ridge, however, the reverse is the case, the greatest rainfall taking place on that side which lies to leeward, as regards the prevailing winds. to the same cause may be ascribed the fact that the rainfall is greater in mountainous than in flat districts, and greater at points near high mountain summits than at points farther from them; and the difference due to elevation is often greater by far than that due to 100 miles geographical distance. the most important data respecting the depth of rainfall in a given district, for practical purposes, are, the least annual rainfall; mean annual rainfall; greatest annual rainfall; distribution of the rainfall at different seasons, and especially, the longest continuous drought; greatest flood rainfall, or continuous fall of rain in a short period. the available rainfall of a district is that part of the total rainfall which remains to be stored in reservoirs, or carried away by streams, after deducting the loss through evaporation, through permanent absorption by plants and by the ground, and other causes. the proportion borne by the available to the total rainfall varies very much, being affected by the rapidity of the rainfall and the compactness or porosity of the soil, the steepness or flatness of the ground, the nature and quantity of the vegetation upon it, the temperature and moisture of the air, which will affect the rate of evaporation, the existence of artificial drains, and other circumstances. the following are examples: available rainfall. ground. ÷ total rainfall. steep surfaces of granite, gneiss, and slate, nearly 1 moorland and hilly pasture from ·8 to ·6 flat cultivated country from ·5 to ·4 chalk 0 deep-seated springs and wells give from ·3 to ·4 of the total rainfall. stephenson found that for the chalk district round watford the evaporation was about 34 per cent., the quantity carried off by streams 23·2 per cent., leaving 42·8 per cent., which sank below the surface to form springs. in formations less absorbent than the chalk it can be calculated roughly, that streams carry off one-third, that another third evaporates, and that the remaining third of the total rainfall sinks into the earth. such data as the above may be used in approximately estimating the probable available rainfall of a district; but a much more accurate and satisfactory method is to measure the actual discharge of the streams, and the quantity lost by evaporation, at the same time that the rain-gauge observations are made, and so to find the actual proportion of available to total rainfall. the following table gives the mean annual rainfall in various parts of the world;-table of rainfall. collected by g. j. symons. -----------------------------+--------------+----------+------ | period | | mean country and station. | of | latitude.| annual | observations.| | fall. -----------------------------+--------------+----------+------ europe. | years | ° ´ | ins. austria--cracow | 5 | 50 4n | 33·1 prague | 47 | 50 5 | 15·1 vienna | 10 | 48 12 | 19·6 belgium--brussels | 20 | 50 51 | 28·6 ghent | 13 | 51 4 | 30·6 louvain | 12 | 50 33 | 28·6 denmark--copenhagen | 12 | 55 41 | 22·3 france--bayonne | 10 | 43 29 | 56·2 bordeaux | 32 | 44 50 | 32·4 brest | 30 | 48 23 | 38·8 dijon | 20 | 47 14 | 31·1 france--lyons | .. | 45 46 | 37·0 marseilles | 60 | 43 17 | 19·0 montpelier | 51 | 43 36 | 30·3 nice | 20 | 43 43 | 55·2 paris | 44 | 48 50 | 22·9 pau | 12 | 43 19 | 37·1 rouen | 10 | 49 27 | 33·7 toulon | .. | 43 4 | 19·7 toulouse | 52 | 43 36 | 24·9 great britain- | | | england, london | 40 | 51 31 | 24·0 " manchester | 40 | 53 29 | 36·0 " exeter | 40 | 50 44 | 33·0 " lincoln | 40 | 53 15 | 20·0 wales, cardiff | 40 | 51 28 | 43·0 " llandudno | 40 | 53 19 | 30·0 scotland, edinburgh | 40 | 55 57 | 24·0 " glasgow | 40 | 55 52 | 39·0 " aberdeen | 40 | 57 8 | 31·0 ireland, cork | 40 | 51 54 | 40·0 " dublin | 40 | 53 23 | 30·0 " galway | 40 | 53 15 | 50·0 holland--rotterdam | .. | 51 55 | 22·0 iceland--reikiavik | 5 | 64 8 | 28·0 ionian isles--corfu | 22 | 39 37 | 42·4 italy--florence | 8 | 43 46 | 35·9 milan | 68 | 45 29 | 38·0 naples | 8 | 40 52 | 39·3 rome | 40 | 41 53 | 30·9 turin | 4 | 45 5 | 38·6 venice | 19 | 45 25 | 34·1 malta | .. | 35 54 | 15·0 norway--bergen | 10 | 60 24 | 84·8 christiania | .. | 59 54 | 26·7 portugal--coimbra | | | (in vale of mondego) | 2 | 40 13 | 224·0? lisbon | 20 | 38 42 | 23·0 prussia--berlin | 6 | 52 30 | 23·6 cologne | 10 | 50 55 | 24·0 hanover | 3 | 52 24 | 22·4 potsdam | 10 | 52 24 | 20·3 russia--st. petersburg | 14 | 59 56 | 16·2 archangel | 1 | 64 32 | 14·5 astrakhan | 4 | 46 24 | 6·1 finland, uleaborg | .. | 65 0 | 13·5 sicily--palermo | 24 | 38 8 | 22·8 spain--madrid | .. | 40 24 | 9·0 oviedo | 1 | 43 22 | 111·1 sweden--stockholm | 8 | 59 20 | 19·7 switzerland--geneva | 72 | 46 12 | 31·8 great st. bernard | 43 | 45 50 | 58·5 lausanne | 8 | 46 30 | 38·5 | | | asia. | | | china--canton | 14 | 23 6 | 69·3 macao | .. | 22 24 | 68·3 pekin | 7 | 39 54 | 26·9 india- | | | ceylon, colombo | .. | 6 56 | 91·7 " kandy | .. | 7 18 | 84·0 " adam's peak | .. | 6 50 | 100·0 bombay | 33 | 18 56 | 84·7 calcutta | 20 | 22 35 | 66·9 cherrapongee | .. | 25 16 | 610·3? darjeeling | .. | 27 3 | 127·3 madras | 22 | 13 4 | 44·6 mahabuleshwur | 15 | 17 56 | 254·0 malabar, tellicherry | .. | 11 44 | 116·0 palamcotta | 5 | 8 30 | 21·1 patna | .. | 25 40 | 36·7 poonah | 4 | 18 30 | 23·4 malay--pulo penang | .. | 5 25 | 100·5 singapore | .. | 1 17 | 190·0 persia--lencoran | 3 | 38 44 | 42·8 ooroomiah | 1 | 37 28 | 21·5 russia--barnaoul | 15 | 53 20 | 11·8 nertchinsk | 12 | 51 18 | 17·5 okhotsk | 2 | 59 13 | 35·2 tiflis | 6 | 41 42 | 19·3 tobolsk | 2 | 58 12 | 23·0 turkey--palestine, jerusalem | { 14 | 31 47 | 65·0? | { 3 | 31 47 | 16·3 smyrna | .. | 38 26 | 27·6 | | | africa. | | | abyssinia--gondar | .. | 12 36 | 37·3 algeria--algiers | 10 | 36 47 | 37·0 constantina | .. | 36 24 | 30·8 mostaganem | 1 | 35 50 | 22·0 oran | 2 | 35 50 | 22·1 ascension | 2 | 8 8s | 11·5 cape colony--cape town | 20 | 33 52 | 24·3 guinea--christiansborg | .. | 5 30n | 19·2 madeira | 4 | 33 30 | 30·9 mauritius--port louis | .. | 20 3s | 35·2 natal--maritzburgh | .. | 29 36 | 27·6 st. helena | 3 | 15 55n | 18·8 sierra leone | .. | 8 30 | 86·0 teneriffe | 2 | 28 28 | 22·3 | | | north america. | | | british columbia- | | | new westminster | 3 | 49 12 | 54·1 canada--montreal, | | | st. martin's | 2 | 45 31 | 47·3 toronto | 16 | 43 39 | 31·4 honduras--belize | 1 | 17 29 | 153·0 mexico--vera cruz | .. | 19 12 | 66·1 russian america--sitka | 7 | 57 3 | 89·9 united states--arkansas, | | | fort smith | 15 | 35 23 | 42·1 california, san francisco | 9 | 37 48 | 23·4 nebraska, fort kearny | 6 | 40 38 | 28·8 new mexico, socorro | 2 | 34 10 | 7·9 new york, west point | 12 | 41 23 | 46·5 ohio, cincinnati | 20 | 39 6 | 46·9 pennsylvania, philadelphia | 19 | 39 57 | 43·6 south carolina, charlestown| 15 | 32 46 | 48·3 texas, matamoras | 6 | 25 54 | 35·2 west indies--antigua | .. | 17 3 | 39·5 barbadoes | 10 | 13 12 | 75·0 " st. philip | 20 | 13 13 | 56·1 cuba, havannah | 2 | 23 9 | 50·2 matanzas | 1 | 23 2 | 55·3 grenada | .. | 12 8 | 126·0 guadaloupe, basseterre | .. | 16 5 | 126·9 " matonba | .. | 16 5 | 285·8 jamaica, caraib | .. | 18 3 | 97·0 " kingstown | .. | 17 58 | 83·0 st. domingo, cape haitien | .. | 19 43 | 127·9 " tivoli | .. | 19 0 | 106·7 trinidad | .. | 10 40 | 62·9 virgin isles, st. thomas' | .. | 18 17 | 60·6 " tortola | .. | 18 27 | 65·1 | | | south america. | | | brazil--rio janeiro | .. | 22 54s | 58·7 s. luis de maranhao | .. | 3 0 | 276·0 guyana--cayenne | 6 | 4 56 | 138·3 demerara, george town | 5 | 6 50 | 87·9 paramaribo | .. | 6 0 | 229·2 new granada--la baja | 6 | 7 22 | 54·1 marmato | 15 | 5 29 | 90·0 santa fé de bogota | 6 | 4 36 | 43·8 venezuela--cumana | .. | 10 27 | 7·5 curaçoa | .. | 12 15n | 26·6 | | | australia. | | | new south wales--bathurst | 3 | 33 24s | 22·7 deniliquin | 2 | 35 32 | 13·8 newcastle | 3 | 32 57 | 55·3 port macquarie | 12 | 31 29 | 70·8 sydney | 6 | 33 52 | 46·2 new zealand--auckland | 2 | 36 50 | 31·2 christchurch | 3 | 43 45 | 31·7 nelson | 2 | 41 18 | 38·4 taranaki | 2 | 39 3 | 52·7 wellington | 2 | 41 17 | 37·8 south australia--adelaide | 6 | 34 55 | 19·2 tasmania--hobart town | 12 | 42 54 | 20·3 victoria--melbourne | 6 | 37 49 | 30·9 port phillip | 11 | 38 30 | 29·2 west australia--albany | .. | 35 0 | 32·1 york | 1 | 31 55 | 25·4 | | | polynesia. | | | society islands- | | | tahiti, papiete | 5 | 17 32 | 45·7 -----------------------------+--------------+----------+-------disturbances of the strata. the last question to be considered relates to the disturbances which may have affected the strata; for whatever may be the absorbent power of the strata, the yield of water will be more or less diminished whenever the channels of communication have suffered break or fracture. if the strata remained continuous and unbroken, we should merely have to ascertain the dimensions and lithological character of the strata in order to determine their water value. but if the strata is broken, the interference with the subterranean transmission of water will be proportionate to the extent of the disturbance. although the tertiary formations around london have probably suffered less from the action of disturbing forces than the strata of any other district of the same extent in england, yet they nevertheless now exhibit considerable alterations from their original position. the principal change has been that which, by elevation of the sides or depression of the centre of the district, gave the tertiary deposits their present trough-shaped form, assuming it not to be the result of original deposition. if no further change had taken place we might have expected to find an uninterrupted communication in the lower tertiary strata from their northern outcrop at hertford to their southern outcrop at croydon, as well as from newbury on the west to the sea on the east; and the entire length of 260 miles of outcrop would have contributed to the general supply of water at the centre. but this is far from being the case; several disturbing causes have deranged the regularity of original structure. the principal one has caused a low axis of elevation, or rather a line of flexure running east and west, following nearly the course of the thames from the nore to deptford, and apparently continued thence beyond windsor. it brings up the chalk at cliff, purfleet, woolwich, and loampit hill to varied but moderate elevations above the river level. between lewisham and deptford the chalk disappears below the tertiary series, and does not come to the surface till we reach the neighbourhood of windsor and maidenhead. there is also, probably, another line of disturbance running between some points north and south and intersecting the first line at deptford. it passes apparently near beckenham and lewisham, and then, crossing the thames near deptford, continues up a part, if not along the whole length of the valley of the lea towards hoddesdon. this disturbance appears in some places to have resulted in a fracture or a fault in the strata, placing the beds on the east of it on a higher level than those on the west; and at other places merely to have produced a curvature in the strata. prestwich states that he was unable to give its exact course, but its effect, at all events upon the water supply of london, is important, as, in conjunction with the first or thames valley disturbance, it cuts off the supplies from the whole of kent, and interferes most materially with the supply from essex; for in its course up the valley of the lea it either brings up the lower tertiary strata to the surface, as at stratford and bow, or else, as farther up the valley, it raises them to within 40 or 60 feet of the surface. the tertiary district thus appears, on a general view, to be divided naturally into four portions by lines running nearly north and south, the former line passing immediately south, and the latter east of london, which stands at the south-east corner of the north-western division, and consequently it must not be viewed as the centre of one large and unbroken area, so far as the tertiary strata are concerned. chapter ii. the new red sandstone. this formation has been already alluded to at pp. 5 and 8; it is, next to the chalk and lower greensand, the most extensive source of water supply from wells we have in england, and although the two formations mentioned occupy a larger area, yet, owing to geographical position, the new red sandstone receives a more considerable quantity of rainfall, and, owing to the comparative scarceness of carbonate of lime, yields softer water. the new red sandstone is called on the continent "the trias," as in germany and parts of france it presents a distinct threefold division. although the names of each of the divisions are commonly used, they are in themselves local and unessential, as the same exact relations between them do not occur in other remote parts of europe or in england, and are not to be looked for in distant continents. the names of the divisions and their english equivalents are: 1. keuper, or red marls. 2. muschelkalk, or shell limestones (not found in this country). 3. bunter sandstone, or variegated sandstone. the strata consist in general of red, mottled, purple, or yellowish sandstones and marls, with beds of rock-salt, gypsum pebbles, and conglomerate. the region over which triassic rocks outcrop in england stretches across the island from a point in the south-western part of the english channel about exmouth, devon, north-north-eastward, and also from the centre of this band along a north-westward course to liverpool, thence dividing and running north-east to the tees, and north-west to solway firth. in central europe the trias is found largely developed, and in north america it covers an area whose aggregate length is some 700 or 800 miles. the beds, in england, may be divided as follows; average thickness. keuper--red marls, with rock-salt and gypsum 1000 ft. lower keuper sandstones, with trias sandstones and marls (waterstones) 250 ft. dolomitic conglomerate bunter--upper red and mottled sandstone 300 ft. pebble beds, or uncompacted conglomerate 300 ft. lower red and mottled sandstone 250 ft. the keuper series is introduced by a conglomerate often calcareous, passing up into brown, yellow, or white freestone, and then into thinly laminated sandstones and marls. the other subdivisions are remarkably uniform in character, except in the case of the pebble beds, which in the north-west form a light red pebbly building stone, but in the central counties becomes generally an unconsolidated conglomerate of quartzose pebbles. the following tabulated form, due to edward hull, esq., m.a., shows the comparative thickness and range of the triassic series along a south-easterly direction from the estuary of the mersey, and also shows the thinning away of all the triassic strata from the north-west towards the south-east of england, which hull was amongst the first to demonstrate. thickness and range of the trias in a s.e. direction from the mersey. ------------------+----------------+---------------+-------------- | lancashire | | leicestershire names of strata. | and | staffordshire.| and | west cheshire. | | warwickshire. ------------------+----------------+---------------+-------------- keuper series- | | | red marl | 3,000 | 800 | 700 lower keuper | | | sandstone | 450 | 200 | 150 | | | bunter series- | | | upper mottled | | | sandstone | 500 | 50 to 200 | absent pebble beds | 500 to 750 | 100 to 300 | 0 to 100 lower mottled | | | sandstone | 200 to 500 | 0 to 100 | absent ------------------+----------------+---------------+--------------the formation may be looked upon as almost equally permeable in all directions, and the whole mass may be regarded as a reservoir up to a certain level, from which, whenever wells are sunk, water will always be obtained more or less abundantly, this view is very fairly borne out by experience, and the occurrence of the water is certainly not solely due to the presence of the fissures or joints traversing the rock, but to its permeability, which, however, varies in different districts. in the neighbourhood of liverpool the rock, or at least the pebble bed, is less porous than in the neighbourhood of whitmore, nottingham, and other parts of the midland counties, where it becomes either an unconsolidated conglomerate or a soft crumbly sandstone. yet wells sunk even in the hard building stone of the pebble beds, either in cheshire or lancashire, always yield water at a certain variable depth. beyond a certain depth the water tends to decrease, as was the case in the st. helen's public well, situated on eccleston hill. at this well an attempt was made, in 1868, to increase the supply by boring deeper into the sandstone, but without any good result. when water percolates downwards in the rock we may suppose there are two forces of an antagonistic character brought into play; there is the force of friction, increasing with the depth, and tending to hinder the downward progress of the water, while there is the hydrostatic pressure tending to force the water downwards; and we may suppose that when equilibrium has been established between these two forces, the further percolation will cease. the proportion of rain which finds it way into the rock in some parts of the country must be very large. when the rock, as is generally the case in lancashire, cheshire, and shropshire, is partly overspread by a coating of dense boulder clay, almost impervious to water, the quantity probably does not exceed one-third of the rainfall over a considerable area; but in some parts of the midland counties, where the rock is very open, and the covering of drift scanty or altogether absent, the percolation amounts to a much larger proportion, probably one-half or two-thirds, as all the rain which is not evaporated passes downwards. the new red sandstone, as remarked, may be regarded, in respect to water supply, as a nearly homogeneous mass, equally available throughout; and it is owing to this structure, and the almost entire absence of beds of impervious clay or marl, that the formation is capable of affording such large supplies of water; for the rain which falls on its surface and penetrates into the rock is free to pass in any direction towards a well when sunk in a central position. if we consider the rock as a mass completely saturated with water through a certain vertical depth, the water being in a state of equilibrium, when a well is sunk, and the water pumped up, the state of equilibrium is destroyed, and the water in the rock is forced in from all sides. the percolation is, doubtless, much facilitated by joints, fissures, and faults, and in cases where one side of a fault is composed of impervious strata, such as the keuper marls, or coal measures, the quantity of water pent up against the face of the fault may be very large, and the position often favourable for a well. an instance of the effect of faults in the rock itself, in increasing the supply, is afforded in the case of the well at flaybrick hill, near birkenhead. from the bottom of this well a heading was driven at a depth of about 160 feet from the surface, to cut a fault about 150 feet distant, and upon this having been effected the water flowed in with such impetuosity that the supply, which had been 400,000 gallons a day, was at once doubled. the water from the new red sandstone is clear, wholesome, and pleasant to drink; it is also well adapted for the purposes of bleaching, dyeing, and brewing; at the same time it must be admitted that its qualities as regards hardness, in other words, the proportions of carbonates of limes and magnesia it contains, are subject to considerable variation, depending on the locality and composition of the rock. as a general rule, the water from the new red sandstone may be considered as occupying a position intermediate between the _hard_ water of the chalk, and the _soft_ water supplied to some of our large towns from the drainage of mountainous tracts of the primary formations, of which the water supplied from loch katrine to glasgow is perhaps the purest example, containing only 2·35 grains of solid matter to the gallon. having besides but a small proportion of saline ingredients, which, while they tend to harden the water, are probably not without benefit in the animal economy, the water supply from the new red sandstone possesses incalculable advantages over that from rivers and surface drainage. many of our large towns are now partially or entirely supplied with water pumped from deep wells in this sandstone; and several from copious springs gushing forth from the rock at its junction with some underlying impervious stratum belonging to the primary series. chapter iii. well sinking. previous to sinking it will be necessary to have in readiness a stock of buckets, shovels, picks, rope, a pulley-block or a windlass, and barrows or other means of conveying the material extracted away from the mouth of the sinking. after all the preliminary arrangements have been made, the sinking is commenced by marking off a circle upon the ground 12 or 18 inches greater in circumference than the intended internal diameter of the well. the centre of the well as commenced from must be the centre of every part of the sinking; its position must be carefully preserved, and everything that is done must be true to this centre, the plumb-line being frequently used to test the vertical position of the sides. [illustration: drum curb plan. fig. 17.] [illustration: drum curb section. fig. 18.] to sink a well by underpinning, an excavation is first made to such a depth as the strata will allow without falling in. at the bottom of the excavation is laid a curb, that is, a flat ring, whose internal diameter is equal to the intended clear diameter of the well, and its breadth equal to the thickness of the brickwork. it is made of oak or elm planks 3 or 4 inches thick, either in one layer fished at the joints with iron, or in two layers breaking joint, and spiked or screwed together. on this, to line the first division of the well, a cylinder of brickwork, technically called steining, is built in mortar or cement. in the centre of the floor is dug a small pit, at the bottom of which is laid a small platform of boards; then, by cutting notches in the side of the pit, raking props are inserted, their lower ends abutting against a foot block, and their upper ends against the lowest setting, so as to give temporary support to the curb with its load of brickwork. the pit is enlarged to the diameter of the shaft above; on the bottom of the excavation is laid a new curb, on which is built a new division of the brickwork, giving permanent support to the upper curb; the raking props and their foot-blocks are removed; a new pit is dug, and so on as before. care should be taken that the earth is firmly packed behind the steining. a common modification of this method consists in excavating to such a depth as the strata will admit without falling in. a wooden curb is laid at the bottom of the excavation, the brick steining laid upon it and carried to the surface. the earth is then excavated flush with the interior sides of the well, so that the earth underneath the curb supports the brickwork above. when the excavation has been carried on as far as convenient, recesses are made in the earth under the previous steining, and in these recesses the steining is carried up to the previous work. when thus supported the intermediate portions of earth between the sections of brickwork carried up are cut away and the steining completed. in sinking with a drum curb, the curb, which may be either of wood or iron, consists of a flat ring for supporting the steining, and of a vertical hollow cylinder or drum of the same outside diameter as the steining, supporting the ring within it and bevelled to a sharp edge below. the rings, or ribs, of a wooden curb are formed of two thicknesses of elm plank, 1-1/2 inch thick by 9 inches wide, giving a total thickness of 3 inches. [illustration: iron drum curb plan. fig. 19.] [illustration: iron curb enlarged segment. fig. 20.] fig. 17 is a plan of a wooden drum curb, and fig. 18 a section showing the mode of construction. the outside cylinder or drum is termed the lagging, and is commonly made from 1-1/2-inch yellow pine planks. the drum may be strengthened if necessary by additional rings, and its connections with the rings made more secure by brackets. in large curbs the rings are placed about 3 feet 6 inches apart. fig. 19 is a plan, and fig. 20 an enlarged segment of an iron curb. when the well has been sunk as far as the earth will stand vertical, the drum curb is lowered into it and the building of the brick cylinder commenced, care being taken to complete each course of bricks before laying another, in order that the curb may be loaded equally all round. the earth is dug away from the interior of the drum, and this, together with the gradually increasing load, causes the sharp lower edge of the drum to sink into the earth; and thus the digging of the well at the bottom, the sinking of the drum curb and the brick lining which it carries, and the building of the steining at the top, go on together. care must be taken in this, as in every other method, to regulate the digging so that the well shall sink vertically. should the friction of the earth against the outside of the well at length become so great as to stop its descent before the requisite depth is attained, a smaller well may be sunk in the interior of the first well. a well so stopped is said to be earth-fast. this plan cannot be applied to deep wells, but is very successful in sandy soils where the well is of moderate depth. the curbs are often supported by iron rods, fitted with screws and nuts, from cross timbers over the mouth of the well, and as the excavation is carried on below, brickwork is piled on above, and the weight of the steining will carry it down as the excavation proceeds, until the friction of the sides overpowers the gravitating force or weight of the steining, when it becomes earth-bound; then a set-off must be made in the well, and the same operation repeated as often as the steining becomes earth-bound, or the work must be completed by the first method of underpinning. when the rock to be sunk through is unstratified, or if stratified, when of great thickness, recourse must be had to the action of explosive agents. the explosives most frequently used for this purpose are guncotton, dynamite, lithofracteur, and gunpowder. lithofracteur is now often employed, and always with considerable success, as its power is similar to that of dynamite, but, what is particularly important in vertical bore-holes, its action is intensely local; it is, moreover, safe, does not generate fumes more harmful than ordinary gunpowder, requires smaller holes, and but little tamping. the dangerous character of guncotton has hitherto prevented its adoption for ordinary operations, while the comparatively safe character and convenient form of gunpowder have commended it to the confidence of workmen, and hence for sinking operations this explosive is generally employed. we shall therefore, in treating of blasting for well sinking, consider these operations as carried out by the aid of gunpowder alone. the system of blasting employed in well sinking is that known as the small-shot system, which consists in boring holes from 1 to 3 inches diameter in the rock to be disrupted to receive the charge. the position of these holes is a matter of the highest importance from the point of view of producing the greatest effects with the available means, and to determine them properly requires a complete knowledge of the nature of the forces developed by an explosive agent. this knowledge is rarely possessed by sinkers. indeed, such is the ignorance of this subject displayed by quarrymen generally, that when the proportioning and placing the charges are left to their judgment, a large expenditure of labour and material will produce very inadequate results. in all cases it is far more economical to entrust these duties to one who thoroughly understands the subject. the following principles should govern all operations of this nature. the explosion of gunpowder, by the expansion of the gases suddenly evolved, develops an enormous force, and this force, due to the pressure of a fluid, is exerted equally in all directions. consequently, the surrounding mass subjected to this force will yield, if it yield at all, in its weakest part, that is, in the part which offers least resistance. the line along which the mass yields, or line of rupture, is called the line of least resistance, and is the distance traversed by the gases before reaching the surface. when the surrounding mass is uniformly resisting, the line of least resistance will be a straight line, and will be the shortest distance from the centre of the charge to the surface. such, however, is rarely the case, and the line of rupture will therefore in most instances be an irregular line, and often much longer than that from the centre direct to the surface. hence in all blasting operations there will be two things to determine, the line of least resistance and the quantity of powder requisite to overcome the resistance along that line. for it is obvious that all excess of powder is waste; and, moreover, as the force developed by this excess must be expended upon something, it will probably be employed in doing mischief. charges of powder of uniform strength produce effects varying with their weight, that is, a double charge will move a double mass. and as homogeneous masses vary as the cube of any similar line within them, the general rule is established that charges of powder to produce similar results are to each other as the cubes of the lines of least resistance. hence when the charge requisite to produce a given effect in a particular substance has been determined by experiment, that necessary to produce a like effect in a given mass of the same substance may be readily determined. as the substances to be acted upon are various and differ in tenacity in different localities, and as, moreover, the quality of powder varies greatly, it will be necessary, in undertaking sinking operations, to make experiments in order to determine the constant which should be employed in calculating the charges of powder. in practice, the line of least resistance is taken as the shortest distance from the centre of the charge to the surface of the rock, unless the existence of natural divisions shows it to lie in some other direction; and, generally, the charge requisite to overcome the resistance will vary from 1/15 to 1/35 of the cube of the line, the latter being taken in feet and the former in pounds. thus, suppose the material to be blasted is chalk, and the line of least resistance 4 feet, the cube of 4 is 64, and taking the proportion for chalk as 1/30, we have 64/30 = 2-2/15 lb. as the charge necessary to produce disruption. [illustration: jumper. fig. 21.] when the blasting is in stratified rock, the position of the charge will frequently be determined by the natural divisions and fissures; for if these are not duly taken into consideration, the sinker will have the mortification of finding, after his shot has been fired, that the elastic gases have found an easier vent through one of these flaws, and that consequently no useful effect has been produced. the line of least resistance, in this case, will generally be perpendicular to the beds of the strata, so that the hole for the charge may be driven parallel to the strata and in such a position as not to touch the planes which separate them. this hole should never be driven in the direction of the line of least resistance, and when practicable should be at right-angles to it. the instruments employed in boring the holes for the shot are iron rods having a wedge-shaped piece of steel welded to their lower ends and brought to an edge so as to cut into the rock. these are worked either by striking them on the head with a hammer, or by jumping them up and down and allowing them to penetrate by their own weight. when used in the former manner they are called borers or drills; in the latter case they are of the form fig. 21, and are termed jumpers. recently power jumpers worked by compressed air, and drills actuated in the same manner have been very successfully employed. holes may be made by these instruments in almost any direction; but when hand labour only is available, the vertical can be most advantageously worked. hand-jumpers are usually about 4 feet 8 inches in length, and are used by holding in the direction of the required hole, and producing a series of sharp blows through lifting the tool about a foot high and dropping it with an impulsive movement. the bead divides a jumper into two unequal lengths, of which the shorter is used for commencing a bore-hole, and the longer for finishing it. often the bit on the long length is made a trifle smaller than the other to remove any chance of its not following into the hole which has been commenced. drills and jumpers should be made of the best iron, preferably swedish, for if the material be of an inferior quality it will split and turn over under the repeated blows of the mall, and thus endanger the hands of the workman who turns it, or give off splinters that may cause serious injury to those engaged in the shaft. frequently they are made entirely of steel, and this material has much to recommend it for this purpose; the length of drills varies from 18 inches to 4 feet, the different lengths being put in successively as the sinking of the hole progresses. the cutting edge of the drills should be well steeled, and for the first, or 18-inch drill, have generally a breadth of 2 inches; the second, or 28-inch drill, may be 1-3/4 inch on the edge; the third, or 3-foot drill, 1-1/2 inch, and the fourth, or 4-foot drill, 1-1/4 inch. [illustration: funnel and pipe for shot-hole acid pouring. fig. 22.] the mode of using the drill in the latter case is as follows; the place for the hole having been marked off with the pick, one man sits down holding the drill in both hands between his legs. another man then strikes the drill with a mall, the former turning the drill partially round between each blow to prevent the cutting edge from falling twice in the same place. the speed with which holes may be sunk varies of course with the hardness of the rock and the diameter of the hole. at holyhead the average work done by three men in hard quartz rock with 1-1/2-inch drills was 14 inches an hour; one man holding the drill, and two striking. in granite of good quality, it has been ascertained by experience that three men are able to sink with a 3-inch jumper 4 feet in a day; with a 2-1/2-inch jumper, 5 feet; with a 2-1/4-inch, 6 feet; with a 2-inch, 8 feet; and with a 1-3/4-inch, 12 feet. a strong man with a 1-inch jumper will bore 8 feet in a day. the weight of the hammers used with drills is a matter deserving attention; for if too heavy they fatigue the men, and consequently fewer blows are given and the effect produced lessened; while, on the other hand, if too light, the strength of the workman is not fully employed. the usual weight is from 5 to 7 lb. as the labour of boring a shot-hole in a given kind of rock is dependent on the diameter, it is obviously desirable to make the hole as small as possible, due regard being had to the size of the charge; for it must be borne in mind in determining the diameter of the boring that the charge should not occupy a great length in it. various expedients have been resorted to for the purpose of enlarging the hole at the bottom so as to form a chamber for the powder. if this could be easily effected, such a mode of placing the charge would be highly advantageous, as a very small bore-hole would be sufficient, and the difficulties of tamping much lessened. one of these expedients is to place a small charge at the bottom of the bore and to fire it after being properly tamped. the charge being insufficient to cause fracture, the parts in immediate contact with it are compressed and crushed to dust, and the cavity is thereby enlarged. the proper charge may then be inserted in the chamber thus formed by boring through the tamping. another method, applicable chiefly to calcareous rock, has been tried with satisfactory results at marseilles. when the bore-hole has been sunk to the required depth, a copper pipe, fig. 22, of a diameter to fit the bore loosely, is introduced, the end a reaching to the bottom of the hole, which is closed up tight at b with clay so that no air may escape. the pipe is provided with a bent neck c. a small leaden pipe _e_, about half an inch in diameter, with a funnel _f_ at the top, is introduced into the copper pipe at d and passed down to within about an inch of the bottom. the annular space between the leaden and copper pipes at _g_ is filled with a packing of hemp. dilute nitric acid is then poured through the funnel and leaden pipe. the acid dissolves the calcareous rock at the bottom, causing an effervescence, and a substance containing the dissolved lime is forced out of the orifice c. this process is continued until from the quantity of acid consumed it is judged that the chamber is sufficiently enlarged. other acids, such as muriatic or sulphuric, will produce the same effects, but the result of the chemical solution will of course depend upon the nature of the stone. after the shot-hole has been bored, it is cleaned out and dried with a wisp of hay, and the powder poured down; or, when the hole is not vertical, pushed in with a wooden rammer. the quantity of powder should always be determined by weight. one pound, when loosely poured out, will occupy about 30 cubic inches, and 1 cubic foot weighs 57 pounds. a hole 1 inch in diameter will therefore contain ·414 ounce for every inch of depth. hence to find the weight of powder to an inch of depth in any given hole, we have only to multiply ·414 ounce by the square of the diameter of the hole in inches, and we are enabled to determine either the length of hole for a given charge, or the charge in a given space. it is important to use strong powder in blasting operations, because, as a smaller quantity will be sufficient, it will occupy less space, and thereby save labour in boring. [illustration: clay iron. figs. 24, 25.] [illustration: pricker. fig. 23.] when the hole is in wet stone, means must be provided for keeping the powder dry. for this purpose, tin cartridges are sometimes used. these are tin cylinders of suitable dimensions, fitted with a small tin stem through which the powder is ignited. the effect of the powder is, however, much lessened by the use of these tin cases. generally a paper cartridge, well greased to prevent the water from penetrating, will give far more satisfactory results. when the paper shot is used, the hole should, previous to the insertion of the charge, be partially filled with stiff clay, and a round iron bar, called a clay-iron or bull, figs. 24, 25, driven down to force the clay into the interstices of the rock through which the water enters. by this means the hole will be kept comparatively dry. the bull is withdrawn by placing a bar through the eye near the top of the former, provided for that purpose, and lifting it straight out. the cartridge is placed upon the point of a pricker and pushed down the hole. the pricker, shown in fig. 23, is a taper piece of metal, usually of copper to prevent accidents, pointed at one end and having a ring at the other. when the cartridge has been placed in its position by this means, a little oakum is laid over it, and a bickford fuse inserted. this fuse is inexpensive, very certain in its effects, not easily injured by tamping, and is unaffected by moisture. the no. 8 fuse is preferred for wet ground; and when it is required to fire the charge from the bottom in deep holes, no. 18 is the most suitable. when the line of least resistance has been decided upon, care must be taken that it remains the line of least resistance; for if the space in bore-hole is not properly filled, the elastic gases may find an easier vent in that direction than in any other. the materials employed to fill this space are, when so applied, called tamping, and they consist of the chips and dust from the sinking, sand, well-dried clay, or broken brick or stones. various opinions are held concerning the relative value of these materials as tamping. sand offers very great resistance from the friction of the particles amongst themselves and against the sides of the bore-hole; it may be easily applied by pouring it in, and is always readily obtainable. clay, if thoroughly baked, offers a somewhat greater resistance than sand, and, where readily procurable, may be advantageously employed. broken stone is much inferior to either of these substances in resisting power. the favour in which it is held by sinkers and quarrymen, and the frequent use they make of it as tamping, must be attributed to the fact of its being always ready to hand, rather than to any excellent results obtained from its use. the tamping is forced down with a stemmer or tamping bar similar to figs. 26, 27, too frequently made of iron, but which should be either of copper or bronze. the tamping end of the bar is grooved on one side, to admit of its clearing the pricker, or the fuse, lying along the side of the hole. the other end is left plain for the hand or for being struck with a hammer. all tamping should be selected for its freedom from particles likely to strike fire, but it must not be overlooked that the cause of such a casualty may lie in the sides of the hole itself. under these circumstances is seen the advisability of using bronze or copper tamping tools, and of not hammering violently on the tamping until a little of it has been first gently pressed down to cover over the charge, because the earlier blows on the tamping are the most dangerous in the event of a spark occurring. a little wadding, tow, paper, or a wooden plug is sometimes put to lie against the charge before any tamping is placed in the hole. [illustration: tamping bar. figs. 26, 27.] [illustration: metal cone plug. fig. 28.] to lessen the danger of the tamping being blown out, plugs or cones of metal of different shapes are sometimes inserted in the hole. the best forms of plug are shown in figs. 28 and 29; fig. 28 is a metal cone wedged in on the tamping with arrows, and fig. 29 is a barrel-shaped plug. when all is ready, the sinkers, with the exception of one man whose duty it is to fire the charge, are either drawn out of the shaft, or are removed to some place of safety. this man then, having ascertained by calling and receiving a reply that all are under shelter, applies a light to the fuse, shouts "bend away," or some equivalent expression, and is rapidly drawn up the shaft. to avoid shattering the walls of a shaft, no shot should be placed nearer the side than 12 inches. the portion of stone next the wall sides of the shaft left after blasting is removed by steel-tipped iron wedges 7 or 8 inches in length. these wedges are applied by making a small hole with the point of the pick and driving them in with a mall. the sides may be then dressed as required with the pick. [illustration: barrel shaped plug. fig. 29.] after some 30 or 40 feet have been sunk the air at the bottom of the well may be very foul, especially in a well where blasting operations are being carried on, or where there is any great escape of noxious gases through fissures. means must then be provided for applying at the surface a small exhaust fan to which is attached lengths of tubing extending down the well. another good plan is to pass a 4 or 6 inch pipe down the well, bring it up with a long bend at surface, and insert a steam jet; a brick chimney is frequently built over the upper end of the pipe to increase the draught, and the lower end continued down with flexible tubing. with either fan or steam jet, the foul air being continuously withdrawn, fresh air will rush down in its place. this is far better than dashing lime-water down the well, using a long wooden pipe with a revolving caphead, or pouring down a vertical pipe water which escaped at right-angles, the old expedients for freshening the air in a well. a means of increasing the yield of wells, which is frequently very successful, is to drive small tunnels or headings from the bottom of the well into the surrounding water-bearing stratum. [illustration: fig. 30. sectional plan. water-bearing stratum.] as an example, let fig. 30 represent a sectional plan of a portion of the water-bearing stratum at the bottom of the shaft. this stratum is underlaid by an impervious stratum, and, consequently, the water will flow continuously through the former in the direction of the dip, as shown by the arrow and the dotted lines. that portion of the stratum to the rise of the shaft, s, which is included within vertical lines tangent to the circle at the points _m_ and _n_, will be drained by the shaft. the breadth of this portion will, however, be extended beyond these lines by the relief to the lateral pressure afforded by the shaft, which relief will cause the fillets of water to diverge from their original course towards the shaft, as shown in the figure. hence the breadth of drainage ground will be _a b_, and it is evident that the shaft, s, can receive only that water which descends towards it through this space. but if tunnels be driven from the shaft along the strike of the stratum, as at _m c_, _n d_, these tunnels will obviously intercept the water which flows past the shaft. by this means the drainage ground is extended from _a b_ to _a´ b´_, and the yield of the well proportionately increased. it should be remarked that when the strata is horizontal or depressed in the form of a basin, that is, when it partakes more of the character of a _reservoir_ than a _stream_, the only use of tunnels is to facilitate the ingress of water into the shaft, and in such case they should radiate from the shaft in all directions. they are also of service in case of accident to the pumps, as the time they take to fill up allows of examination and repairs being made in that time to the pumps, which could not be got at if the engines stopped pumping and the water rose rapidly up the shaft. the size of the headings is usually limited by the least dimensions of the space in which miners can work efficiently, that is about 4-1/2 feet high and 3 feet wide. the horse-shoe form is generally adopted for the sides and top, the floor being level, for the drawing off of the water by the pumps is quite sufficient to cause a flow, unless of course the dip of the stratum in which the tunnels are driven is such as to warrant an inclination. where there is any water it is not possible to drive them with a fall, for the men would be drowned out. the cost of some headings in the new red sandstone which the writer recently inspected, varied from 30_s._ a yard in ordinary stone, to 4_l._ 10_s._ a yard in very hard stone. the foregoing remarks do not apply to headings driven in the chalk, where it is the usual practice to select the largest feeder issuing from a fissure and follow that fissure up, unless the heading is merely to serve as a reservoir, when the direction is immaterial. the sides of wells usually require lining or steining, as it is termed, with some material that will prevent the loose strata of the sides of the excavation falling into the well and choking it. the materials that have been successfully used in this work are brick, stone, timber, and iron. each description of material is suitable under certain conditions, while in other positions it is objectionable. brickwork, which is universally used in steining wells in england, not unfrequently fails in certain positions; through admitting impure water when such water is under great pressure, or from the work becoming disjointed from settlement due to the draining of a running sand-bed, or the collapse of the well. stone of fair quality, capable of withstanding compressive strains, is good in its way; but, inasmuch as it requires a great deal of labour to fit it for its place, it cannot successfully compete with brickwork in the formation of wells, more especially as it has no merits superior to those of brick when used in such work; however, if in any locality, by reason of its cheapness, it can be used, care should be taken to select only such as contains a large amount of silica; indeed, in all cases it is a point of great importance in studying the nature of the materials used in the construction of wells, to select those which are likely to be the most durable, and at the same time preserve the purity of the water contained in the well; and this is best secured by silicious materials. timber is objectionable as a material to be used in the lining of wells, on account of its liability to decay, when it not only endangers the construction of the well, but also to some extent fouls the water. it is very largely used under some circumstances, especially in the preliminary operations in sinking most wells. it is also successfully used in lining the shafts of the salt wells of cheshire, and will continue entire in such a position for a great number of years, as the brine seems to have a tendency to preserve the timber and prevent its decay. iron is of modern application, and is a material extensively employed in steining wells; and, as it possesses many advantages over materials ordinarily used, its use is likely to be much extended. it is capable of bearing great compressive strains, and of effectually excluding the influx of all such waters as it may be desirable to keep out, and is not liable to decay under ordinary circumstances. baldwin latham mentions instances in his practice where recourse has been had to the use of iron cylinders, when it was found that four or five rings of brickwork, set in the best cement, failed to keep out brackish waters; and, if the original design had provided for the introduction of these cylinders, it would have reduced the cost of the well very materially. [illustration: _plan at top_ fig. 31.] [illustration: elevation. fig. 32.] [illustration: _plan at bottom_ fig. 33.] the well-sinker has often, in executing his work, to contend with the presence of large volumes of water, which, under ordinary circumstances, must be got rid of by pumping; but by the introduction of iron cylinders, which can be sunk under water, the consequent expense of pumping is saved. when sinking these cylinders through water-bearing strata, various tools are used to remove the soil from beneath them. the principal is the mizer, which consists of an iron cylinder with an opening on the side and a cutting lip, and which is attached to a set of boring rods and turned from above. the valve in the old form of mizer is subject to various accidents which interfere with the action of the tool; for instance, pieces of hard soil or rock often lodge between the valve and its seat, allowing the contents to run out whilst it is being raised through water. to remedy this defect the eminent well-sinker, thomas docwra, designed and introduced the improved mizer, shown of the usual dimensions in figs. 31 to 36; fig. 31 being a plan at top, fig. 32 an elevation, fig. 33 a plan at bottom, fig. 35 a section, fig. 34 a plan of the stop _a_, and fig. 36 a plan of the valve. it consists of an iron cylinder, conical shaped at bottom, furnished with holes for the escape of water, and attached to a central shank by means of stays. the shank extends some 7 inches beyond the bottom, and ends in a point, while the upper part of the shank has an open slot, to form a box-joint, figs. 37 to 39, with the rods. the conical bottom of the mizer has a triangular-shaped opening; on the outside of this is fitted a strong iron cutter, and on the inside a properly-shaped valve, seen in section and plan in figs. 35 and 36. when the mizer is attached to and turned by means of the boring rods, the _débris_, sand, or other soil to be removed, being turned up by the lip of the cutter, enters the cylinder, the valve, whilst the mizer is filling, resting against a stop. after the mizer is charged, which can be ascertained by placing a mark upon the last rod at surface and noting its progress downwards, the rods are reversed and turned once or twice in a backward direction; this forces the valve over the opening and retains the soil safely in the tool. [illustration: plan of the stop. fig. 34.] [illustration: a section. fig. 35.] [illustration: plan of the valve. fig. 36.] fig. 40 is a pot mizer occasionally used in such soils as clay mixed with pebbles; there is no valve, as the soil is forced upwards by the worm on the outside, and falls over the edge into the cone. [illustration: box joint. figs. 37-39.] [illustration: pot mizer. fig. 40.] mizers are fastened to the rods by means of the box-joint, shown in figs. 37 to 39, as a screw-joint would come apart on reversing. as many as five or six different sized mizers, ranging from 1 foot 6 inches to 9 feet in diameter, can be used successively, the smallest commencing the excavation, and the larger ones enlarging it until it is of the requisite size. [illustration: picker. figs. 41-43.] as an accessory, a picker, shown by the three views, figs. 41 to 43, fig. 42 indicating its correct position when in operation, is employed where the strata is too irregular or compact to be effectually cleared away by the cutter of the mizer. the picker is fixed upon the same rods above the mizer, and is used simultaneously, being raised and lowered with that tool. [illustration: scratcher. figs. 44, 45.] the cutting end of the picker is frequently replaced by a scratcher, figs. 44, 45. this useful tool rakes or scratches up the _débris_ thrown by the mizer beyond its own working range, and causes it to accumulate in the centre of the sinking, where it is again subjected to the action of the mizer. brick steining is executed either in bricks laid dry or in cement, in ordinary clay 9-inch work being used for large wells, and half-brick, or 4-1/2-inch work, for small wells. [illustration: brick steining. sectional plans. figs. 46-48.] figs. 46 and 47 show the method of laying for 9-inch work, and fig. 48 for 4-1/2 inches. the bricks are laid flat, breaking joint; and to keep out moderate land-springs clay, puddle, or concrete is often introduced at the back of the steining; for most purposes concrete is the best, as, in addition to its impervious character, it adds greatly to the strength of the steining. a ring or two of brickwork in cement is often introduced at intervals, varying from 5 feet to 12 feet apart, to strengthen the shaft, and facilitate the construction of the well. too much care cannot be bestowed upon the steining; if properly executed it will effectually exclude all objectionable infiltration, but badly made, it may prove a permanent source of trouble and annoyance. half the wells condemned on account of sewage contamination really fail because of bad steining. chapter iv. well boring. the first method of well boring known in europe is that called the chinese, in which a chisel suspended by a rope and surrounded by a tube of a few feet in length is worked up and down by means of a spring-pole or lever at the surface. the twisting and untwisting of the rope prevents the chisel from always striking in the same place; and by its continued blows the rock is pounded and broken. the chisel is withdrawn occasionally, and a bucket or shell-pump is lowered, having a hinged valve at the bottom opening upwards, so that a quantity of the _débris_ becomes enclosed in the bucket, and is then drawn up by it to the surface; the lowering of the bucket is repeated until the hole is cleared, and the chisel is then put to work again. fig. 49 is of an apparatus, on the chinese system, which may be used either for hemp-rope or wire-rope, and which was originally made for hoop-iron. at a, fig. 49, is represented a log of oak wood, which is set perpendicularly so deep in the ground as to penetrate the loose gravel and pass a little into the rock, and stand firm in its place; it is well rammed with gravel and the ground levelled, so that the butt of the log is flush with the surface of the ground, or a few feet below. through this log, which may be, according to the depth of loose ground, from 5 feet to 30 feet long, a vertical hole is bored by an auger of a diameter equal to that of the intended boring in the rock. on the top of the ground, on one side of the hole, is a windlass whose drum is 5 feet in diameter, and the cogwheel which drives it 6 feet; the pinion on the crank axle is 6 inches. this windlass serves for hoisting the spindle or drill, and is of a large diameter, in order to prevent short bends in the iron, which would soon make it brittle. [illustration: chinese system. fig. 49.] in all cases where iron, either hoop-iron or wire-rope, is used, the diameter of the drum of the windlass used must be sufficiently large to prevent a permanent bend in the iron. on the opposite side of the windlass is a lever of unequal leverage, about one-third at the side of the hole, and two-thirds at the opposite side, where it ends in a cross or broad end where men do the work. the workmen, with one foot on a bench or platform, rest their hands on a railing, and work with the other foot the long end of the lever. in this way the whole weight of the men is made use of. the lift of the bore-bit is from 10 to 12 inches, which causes the men to work the treadle from 20 to 24 inches high. below the treadle, t, is a spring-pole, s, fastened under the platform on which the men stand, the end of this spring-pole is connected by a link to the working end of the lever, or to the rope directly, and pulls the treadle down. when the bore-spindle is raised by means of the treadle, the spring-pole imparts to it a sudden return, and increases by these means the velocity of the bit, and consequently that of the stroke downwards. this method has been generally disused, iron or wood rods substituted in the place of the rope, and a variety of augers and chisels instead of the simple chisel, with appliances for clearing the bore-hole of _débris_. figs. 50 to 56 show examples of an ordinary set of well boring tools. fig. 52 is a flat chisel; fig. 53 a [v]-chisel; and fig. 54 a [t]-chisel. these chisels are made from wrought-iron, and when small are usually 18 inches long, 2-1/2 inches extreme breadth, and weigh some 4-1/2 lb.; the cutting edge being faced with the best steel. they are used for hard rocks, and whilst in operation need carefully watching that they may be removed and fresh tools substituted when their sides are sufficiently worn to diminish their breadth. if this circumstance is not attended to the size of the hole decreases, so that when a new chisel of the proper size is introduced it will not pass down to the bottom of the hole, and much unnecessary delay is occasioned in enlarging it. in working with the chisel, the borer keeps the tiller, or handles, in both hands, one hand being placed upon each handle, and moves slowly round the bore, in order to prevent the chisel from falling twice, successively, in the same place, and thus preserve the bore circular. every time a fresh chisel is lowered to the bottom it should be worked round in the hole, to test whether it is its proper size and shape; if this is not the case the chisel must be raised at once and worked gradually and carefully until the hole is as it should be. the description of strata being cut by the chisel can be ascertained with considerable accuracy by a skilful workman from the character of the shock transmitted to the rods. when working in sandstone there is no adherence of the rock to the chisel when drawn to the surface, but with clays the contrary is the case. should the stratum be very hard, the chisel may be worn and blunt before cutting three quarters of an inch, it must therefore be raised to the surface and frequently examined; however, 7 or 8 inches may be bored without examination, should the nature of the stratum allow of such progress being made. [illustration: well-boring tools. figs. 50-56.] ground augers, figs. 50, 51, and 56, are similar in action to those used for boring wood, but differ in shape and construction. the common earth auger, fig. 50, is 3 feet in length, having the lower two-thirds cylindrical. the bottom is partially closed by the lips, and there is an opening a little up one side for the admission of soft or bruised material. augers are only used for penetrating soft rock, clay, and sand; and their shape is varied to suit the nature of the strata traversed, being open and cylindrical for clays having a certain degree of cohesion, conical, and sometimes closed, in quicksands. augers are sometimes made as long as 10 feet, and are then very effective if the strata is soft enough to permit of their use. the shell is made from 3 feet to 3-1/2 feet in length, of nearly the same shape as the common auger, sometimes closed to the bottom, fig. 56, or with an auger nose, fig. 51; in either case there is a clack or valve placed inside for the purpose of retaining borings of a soft nature or preventing them from being washed out in a wet hole. fig. 59 shows a wad-hook for withdrawing stones, and fig. 58 a worm-auger. the crow's foot, fig. 55, is used when the boring rods have broken in the bore-hole, for the purpose of extracting that portion remaining in the hole; it is the same length, and at the foot the same breadth as the chisels. when the rods have broken, the part above the fracture is drawn out of the bore-hole and the crow's foot screwed on in place of the broken piece; when this is lowered down upon the broken rod, by careful twisting the toe is caused to grip the broken piece with sufficient force to allow the portion below the fracture to be drawn out of the bore-hole. a rough expedient is to fasten a metal ring to a rope and lower it over the broken rod, when the rod cants the ring, and thus gives it a considerable grip; this is often very successful. fig. 57 is a worm used for the same purpose. a bell-box, fig. 60, is frequently employed for drawing broken rods; it has two palls fixed at the top of the box, which rise and permit the end of the rod to pass when the box is lowered, but upon raising it the palls fall and grip the rod firmly. a spiral angular worm, similar to fig. 57, is also applied for withdrawing tubes. [illustration: withdrawing tools. figs. 57-59.] [illustration: bell-box. fig. 60.] of these withdrawing tools the crow is the safest and best, as it may be used without that intelligent supervision and care absolutely necessary with the worms and wad-hooks, or the bell-box. the boring rods, figs. 61, 62, are in 3, 6, 10, 15, or 20 feet lengths, of wrought-iron, preferably swedish, and are made of different degrees of strength according to the depth of the hole for which they are required; they are generally 1 inch square in section: at one end is a male and at the other end a female screw for the purpose of connecting them together. the screw should not have fewer than six threads. one of the sides of the female screw frequently splits and allows the male screw to be drawn out, thus leaving the rods in the hole. by constant wear, also, the screw may have its thread so worn as to become liable to slip. common rods being most liable to accident should be carefully examined every time they are drawn out of the bore-hole, as an unobserved failure may occasion much inconvenience, and even the loss of the bore-hole. in addition to the ordinary rods there are short pieces, varying from 6 inches to 2 feet in length, which are fixed at the top, as required, for adjusting the rods at a convenient height. [illustration: boring rods. fig. 61, 62.] [illustration: hand-dog. fig. 63.] [illustration: lifting dog. fig. 64, 65.] [illustration: tillers. fig. 66.] fig. 63 is a hand-dog; figs. 64 and 65, a lifting dog; fig. 66, the tillers or handles by which the workmen impart a rotary motion to the tools. the tillers are clamped to the topmost boring rod at a convenient height for working. fig. 61, a top rod with shackle. fig. 67, a spring-hook. when in use this should be frequently examined and kept in repair. [illustration: spring-hook. fig. 67.] lining tubes are employed to prevent the bore-hole falling in through the lateral swelling of clay strata, or when passing through running sand. the tubes are usually of iron, of good quality, soft, easily bent, and capable of sustaining an indent without fracture. inferior tubes occasion grave and costly accidents which are frequently irreparable, as a single bad tube may endanger the success of an entire boring. wrought-iron tubes with screwed flush joints, fig. 68, are to be recommended, but they are supplied brazed, fig. 69, or riveted, fig. 70, and can be fitted with steel driving collars and shoes. cast-iron tubes are constantly applied; they should have turned ends with wrought-iron collars and countersunk screws. [illustration: tubes with screwed joints. fig. 68.] [illustration: tubes with brazed or riveted joints. figs. 69, 70.] cold-drawn wrought-iron tubes have been used, and are very effective as well as easily applied, but their relatively high cost occasions their application to be limited. [illustration: stud block. fig. 71.] fig. 71 shows a stud-block, which is used for suspending tubing either for putting it down or for drawing it up. it consists of a block made to fit inside the end of the tube, and attached to the rods in the usual way. in the side of the block is fixed an iron stud for slipping into a slot, similar to a bayonet-joint, cut in the end of the tube, so that it may be thus suspended. figs. 72 to 74 show various forms of spring-darts, and fig. 75 a pipe-dog, for the same purpose. sometimes a conical plug, with a screw cut around the outside for tightening itself in the upper end of the tube, is used for raising and lowering tubing. figs. 76 and 77 are of tube clamps, and fig. 78 tongs for screwing up the tubes. fig. 79 is of an ordinary form of sinker's bucket. [illustration: spring-dart. fig. 72.] [illustration: spring-dart. fig. 73.] [illustration: spring-dart. fig. 74.] [illustration: pipe-dog. fig. 75.] [illustration: tube clamp. fig. 76.] [illustration: tube clamp. fig. 77.] [illustration: tongs. fig. 78.] [illustration: sinker's bucket. fig. 79.] fig. 80 is a pipe-dolly, used for driving the lining tubes; the figure shows it in position ready for driving. when a projection in the bore-hole obstructs the downward course of the lining tubes, the hole can be enlarged below the pipes by means of a rimer, fig. 81. it consists of an iron shank, to which is bolted two thin strips, bowed out in to the form of a drawing pen. the rimer is screwed on to the boring rods, and forced down through the pipes; when below the last length of pipe the rimer expands, and can then be turned round, which has the effect of scraping the sides and enlarging that portion of the hole subject to its operation. fig. 82 is of an improved form of rimer, termed a riming spring. it will be seen that this instrument is much stronger than the ordinary rimer, in consequence of the shank being extended through its entire length, thus rendering the scraping action of the bows very effective, whilst the slot at the foot of the bows permits of its introduction into, and withdrawal from, the tubing. [illustration: pipe-dolly. fig. 80.] [illustration: rimer. fig. 81.] [illustration: riming spring. fig. 82.] in england, for small works, the entire boring apparatus is frequently arranged as in fig. 83, the tool being fixed at the end of the wrought-iron rods instead of at the end of a rope, as in the chinese method. referring to fig. 83, a is the boring tool; b the rod to which the tool is attached; d d the levers by which the men e e give a circular or rotating motion to the tool; f, chain for attaching the boring apparatus to the pole g, which is fixed at h, and by its means the man at i transmits a vertical motion to the boring tool. [illustration: boring apparatus. english, for small works. fig. 83.] the sheer-legs, made of sound norway spars not less than 8 inches diameter at the bottom, are placed over the bore-hole for the purpose of supporting the tackle k k for drawing the rods out of or lowering them into the hole, when it is advisable to clean out the hole or renew the chisel. it is obvious that the more frequently it is necessary to break the joints in drawing and lowering the rods, the more time will be occupied in changing the chisels, or in each cleaning of the hole, and as the depth of the hole increases the more tedious will the operation be. it therefore becomes of much importance that the rods should be drawn and lowered as quickly as possible, and to attain this end as long lengths as practicable should be drawn at each lift. the length of the lift or off-take, as it is termed, depending altogether upon the height of the lifting tackle above the top of the bore-hole, the length of the sheer-legs for a hole of any considerable depth should not be less than 30 to 40 feet; and they usually stand over a small pit or surface-well, which may be sunk, where the clay or gravel is dry, to a depth of 20 or 30 feet. from the bottom of this pit the bore-hole may be commenced, and here will be stationed the man who has charge of the bore-hole while working the rods. [illustration: boring platform. for deep or difficult wells. fig. 84.] the arrangement, fig. 84, is intended for either deep or difficult boring. a regular scaffolding is erected upon which a platform is built. the boring chisel a is, as in the last instance, coupled by means of screw-couplings to the boring rods b. at each stroke two men stationed at e e turn the rod slightly by means of the tiller d d. a rope f, which is attached to the boring tool, is passed a few times round the drum of a windlass g, the end of the rope being held by a man at i. when the handles are turned by the men at l l the man at i pulls at the rope end, the friction between the rope and the drum of the windlass is then sufficient to raise the rods and boring tool, but as soon as the tool has been raised to its intended height the man at i slackens his hold upon the rope, and as there is insufficient friction on the drum to sustain the weight of the boring tools, they fall. by a repetition of this operation the well is bored, and after it has been continued a sufficient length of time the tiller is unscrewed, and a lifting dog, attached to the rope from the windlass, is passed over the top of the rods, and then a short top rod with a shackle is screwed on. the two men at the windlass draw up the rods as far as the height of the scaffolding or sheer-legs will allow, when a man at e, fig. 84, by passing a hand-dog or a key upon the top of the rod under the lowest joint drawn above the top of the hole, takes the weight of the rods at this joint, the men at l having lowered the rods for this purpose; with another key the rods are unscrewed at this joint, the rope is lowered again, the lifting dog put over the rod, another top rod screwed on, the rods lifted, and the process continued until the chisel is drawn from the hole and replaced by another, or, if necessary, replaced by some other tool. when a deep boring is undertaken, direct from the surface, the operation had best be conducted with the aid of a boring sheer-frame such as is shown in the frontispiece. this consists of a framework of timber balks, upon which are erected four standards, 27 feet in height, and 9 inches × 1 foot thick, 3 feet 8 inches apart at bottom, and 1 foot 2 inches at top, as seen in the front and rear elevations. the standards are tied by means of cross pieces, upon which shoulders are cut which fit into mortise holes, and are fastened by means of wooden keys, the standards being surmounted by two head pieces 5 feet long, mortised and fitted. upon the head pieces two independent cast-iron guide pulleys are arranged in bearings; over these pulleys are led the ends of two ropes coiling in opposite directions upon the barrel of a windlass moved by spur gearing, and having a ratchet stop attached to a pair of diagonal timbers, connected with the left-hand legs or standards of the sheers, near the ground. these ropes are used for raising or lowering the lengths of the boring rod. eight feet below the bearings of the top pulleys, a pair of horizontal traverses is fixed across the frame, supporting smaller pulleys mounted on a cast-iron frame, which is capable of motion between horizontal wooden slides. over these pulleys is led a rope from a plain windlass fixed to the right-hand legs of the frame, to be used for raising or lowering the shell to extract the _débris_ or rubbish from the hole. the lever, 15 feet long, and 9 inches × 6 inches in section, is supported by an independent timber frame. it has a cast-iron cap, fastened by means of two iron straps, cast with lugs through which bolts are passed, these being tightened with nuts in the ordinary manner. the bearing-pins at a are 1-1/2 inch in diameter, and also form part of the lower strap. upon the cap is an iron hook, to this a chain is attached carrying the spring-hook which bears the top shackle of the rods. the top of the bore-hole is surrounded by a wooden tube 1 foot in diameter, and surrounded by a hinged valve, whose action is similar to that of a clack-valve; this has a hole in the centre for the rods to pass up and down freely. the valve permits of the introduction and withdrawal of the tools, and at the same time prevents anything from above falling into the bore-hole. [illustration: diminishing tube diameter arrangement. fig. 85.] the lever is applied by pressure upon its outer end, and as the relation of the long to the short arm is as 4 to 1, a depression of 2 feet in the one case produces an elevation of 6 inches in the other, the minimum range of action, the maximum being 26 inches. with the sheer-frame the boring tools are worked in the same manner as in the preceding arrangements, figs. 83, 84; but its portability, compactness, and adaptation of means to the required end, render its use desirable wherever it is possible to obtain it. [illustration: driving ring for wrought-iron tubes. fig. 86.] when in the progress of the work it is found that the auger does not go down to the depth from which it was withdrawn, after trial, tubing will generally be necessary. the hole should be enlarged from the surface, or, if not very deep, commenced afresh from the surface with a larger auger, and run down to nearly the same depth; the first length of tube is then driven into the hole, and when this is effected another tube, having similar dimensions to the first, is screwed into its upper end, and the driving repeated, and so on until a sufficient number of pipes have been used to reach to the bottom of the hole. if the ordinary auger is now introduced through these tubes it will have free access to the clay or sand, and after a few feet deeper have been bored another pipe may be screwed on, and the whole driven farther down. in this way from 10 to 20 feet of soft stratum may be bored through. if the thickness of the surface clay or sand is considerable the method here mentioned will not be effective, as the friction of the pipes caused by the pressure of the strata will be so great that perhaps not more than 80 or 100 feet can be driven without the pipes being injured. it will then be necessary to put down the first part of the bore-hole with a large auger, and drive in pipes of larger diameter; the hole is continued of smaller diameter, and lined with smaller tubes projecting beyond the large tubes, as in fig. 85, until the necessity for their use ceases. it will be evident that to ensure success the tubing, whatever it is made of, should be as truly cylindrical as possible, straight, and flush surface, both outside and in. it will also be evident that in thus joining pieces of tubing together, the thickness ought to have a due proportion to the work required, and the force likely to be used in screwing or driving them down. wrought-iron tubes, when driven, must be worked carefully, by means of a ring made of wrought-iron, from 1-1/2 to 2 inches in height and 3/4 inch thick, and of the form shown in fig. 86; or driven with a pipe-dolly such as that in fig. 80. the ring, or the dolly, is screwed into the lowermost boring rod and worked at the same rate and in a similar manner to the chisel, due regard being had to the depth at which the driving is being done, as the weight of the boring rods will materially affect the strength of the blow delivered. cast-iron tubing may be driven hard with a monkey. to withdraw broken or defective tubing quickly, two hooks attached to ropes are lowered down from opposite sides of the bore-hole, caught on the rim of the lowermost tube, and power applied to haul the tubing up bodily. figs. 87 to 91 show good methods of forming tube or pipe joints both in cast and wrought-iron, when not screwed. [illustration: fig. 87.] [illustration: fig. 88.] [illustration: fig. 89.] [illustration: fig. 90.] [illustration: fig. 91.] p. s. reed, an english mining engineer, gives the following instance of replacing defective tubing in a boring which had been pursued to the depth of 582-1/2 feet, but which, owing to circumstances which were difficult to determine, had become very expensive, and made slow progress. the 582-1/2 feet had been bored entirely by manual labour; but reid recommended the erection of a horse-gin, in which the power was applied to a 40-inch drum placed upon a vertical axle, the arms of which admitted of applying two horses, and men at pleasure, the power gained being in the proportion of one to ten at the starting-point for the horses. upon the upright drum a double-ended chain was attached, which worked over sheer-legs erected immediately over the hole, so as to attain an off-take for the rods of 60 feet, and so as that, in the act of raising or lowering, there might always be one end of the chain in the bottom, ready to be attached, and expedite the work as much as possible. these arrangements being made, it was soon found that there was a defect in the tubing which was inserted to the depth of 109 feet, and the defect was so serious, in permitting the sand to descend and be again brought up with the boring tools, as to render it very difficult to tell in what strata they really were; this increased to such a degree as to cause the silting up of the hole in a single night to the extent of 180 feet, and it occupied nearly a fortnight in clearing the hole out again. on carefully examining into this defect, it appeared that the water rose in the hole to the depth of 74 feet from the surface; and that at this point it was about level with the high-water mark on the tees, about two miles distant, with which it was no doubt connected by means of permeable beds, extending from the arenaceous strata at a depth of 100 feet. on commencing to bore, the motion of the rods in the hole caused the vibration of the water between a range of 40 feet at the bottom of the tubing, and so disturbed the quiescent sand as to cause it to run down through the faults in the lower end of the tubing. this tubing was made of galvanized iron plates, riveted together and soldered; at the top of the hole it was in three concentric circles, which had been screwed and forced down successively until an obstacle was met with at three different places. so soon as the outer circle reached the first depth, all hope appears to have vanished, from those who bored the earlier part of the work, of getting the tube farther; a second tube was, therefore, inserted, which seems to have advanced as far as the second obstacle, where it, in its turn, was abandoned; and a third one advanced until it rested in the strata at the lower part of the lias freestone of a blue nature, as found on the rocks at seaton carew, and in the bed of the leven, near hutton rudby. the diameter of the first tubing was 3-7/8 inches external and 3-1/2 inches internal; the second tube was 3-1/4 inches external, and 3 inches internal diameter; and the third tube was 2-3/4 inches external and 2-1/2 inches internal diameter. such being the account gathered from the workmen who superintended the earlier part of the boring, it became necessary to decide upon the best cause to remedy the evil. at first sight it would have appeared easy enough to have caught the lower end of the tubes by means of a fish-head properly contrived, and thus to have lifted them out of the hole, and replaced them with a perfect tube, such as a gas-tube, with faucet screw-joints; but, on attempting this, it soon became evident that however good the tubing which might have been adopted, it would be a work of the greatest difficulty to extract when once it was regularly fixed and jammed into its place by the tenacious clayey strata surrounding it; and the difficulty of extracting it, in the present case, was even enhanced by the inferior quality and make of the tubing; in short, that, unless by crumpling it up in such a manner as to destroy the hole, it was impossible to extract this tubing by main force. there was, therefore, no other choice left but to attempt cutting it out, inch by inch; though before doing so, force was applied to the bottom of the tubing, to the extent of upwards of 30 tons, the only result being the loss of several pieces of steel down the hole, which had to be brought up with a powerful magnet. after much mature consideration and contrivance, it was determined to order such tubing as would at the same time present as little obstacle as possible to the clay to be passed through on the outside, as well as surround the largest of the three tubes then in the hole, and present no obstacle to their being withdrawn through its interior. these tubes were made 12 feet in length, flush outside and in, the lower portion being steeled for 6 inches from the bottom end, so as to cut its way and follow down the space, and cover that exposed by the old tubes when cut and drawn, as shown in fig. 92. in order to commence operations, and avoid too much clay going down to the bottom of the hole, a straw-plug was firmly fixed in the lias portion of the hole. the lower portion of the new tubes was then screwed around the old ones by means of powerful clamps, attached to the exterior in such a manner as to avoid injuring the surface; and when they could be screwed no farther, the knife or cutter, figs. 92 to 94, was introduced inside the old tubing. some force was needed to get this knife down into the tubing, but the spring a giving so as to accommodate itself to the hole, permitted its descent to the distance required; this being effected, it was turned round so that the steel cutter, shown at _b_, being forced against the sides of the tube, cut it through in the course of ten minutes or a quarter of an hour's turning. see section at _b_, _c_, fig. 93. [illustration: the action of the knife or spring-cutter. prepared for cutting. fig. 92.] [illustration: the action of the knife or cutter. ready for removal after cutting. fig. 93.] [illustration: back view of knife or cutter. fig. 94.] the old tubes being three-ply, three of these knives or cutters were required to cut out the three tubes, the inner one being detached first, and then the two exterior ones; and so soon as these latter were cut out as far as they had been forced into the clay, the work became simplified into following down the interior tubing by the new tubes, as shown by the dotted lines. from _d_ at the lower end, it was found that the old inner tube had been so damaged or torn, either by the putting in or hammering it down, as to leave a vent or fissure for the sand to descend, and thus spoil the whole of the work for all future success in the boring, to say nothing of the very great cost of lifting the sand out, and subsequent most arduous labour to put the hole right. boring was recommenced after about a month's labour in taking out the old tubings, leaving the new ones firmly bedded into the lias formation, 112 feet from the surface, and the hole was subsequently bored to a depth of 710 feet in the new red sandstone formation, proceeding at the rate of about 3 feet in the twelve hours, and leaving the hole so as, if requisite, it might be widened out to 4 inches diameter. fig. 92 shows the action of the knife and spring-cutter when forced down into the tubing, ready to commence cutting. it also shows the lower end of the new tubing, enclosing the others at the commencement of the work. the joints of the new tubes were made by means of a half-lap screw. fig. 94 is a back view of the knife or cutter _b_. fig. 93 shows the action of the spring and cutter when the requisite length is cut through and ready for lifting; the position of the tube being maintained perpendicular, or nearly so, by the ball or thickening on the rods at k, and the lower end of the tube being supported by the projecting steel cutter at _b_, the dotted lines from _d_ showing the position of the new steel-ended tube when screwed down ready for another operation. in boring deeper after the tubes were removed, three wooden blocks were used round the rods in the new tube to keep them plumb. in some cases it is necessary to widen out holes below the sharp edge of tubing, so as to permit its descent. this is effected with a rimer, figs. 81 and 82, and is an operation requiring great care and attention. to reduce the stoppages for the withdrawal of _débris_ the system of fauvelle was introduced, but it is now very little practised on the continent, and not at all in great britain. the principles upon which it was founded were: first, that the motion given to the tool in rotation was simply derived from the resistance that a rope would oppose to an effort of torsion; and therefore that the limits of application of the system were only such as would provide that the tool should be safely acted upon; and, secondly, that the injection of a current of water, descending through a central tube, should wash out the _débris_ created by the cutting tool at the bottom. the difficulties attending the removal of the _débris_ were great; and though the system of fauvelle answered tolerably well when applied to shallow borings, it was found to be attended with such disadvantages when applied on a large scale, that it has been generally abandoned. the quantity of water required to keep the boring tool clear is a great objection to the introduction of this system, especially as in the majority of cases artesian wells are sunk in such places as are deprived of the advantage of a large supply. in the ordinary system of well boring, innumerable breakages and delays occur when a boring is required to be carried to any depth exceeding 200 or 300 feet, owing to the buckling of the rods, the crystallization of the iron by the constant jarring at each blow, and particularly the increased weight of the rods as the hole gets deeper. it follows from this, that where the excavation is very deep, there is considerable difficulty in transmitting the blow of the tool, in consequence of the vibration produced in the long rod, or in consequence of the torsion; and, for the same reason, there is a danger of the blows not being equally delivered at the bottom. it has been attempted to obviate this difficulty, but without much success, by the use of hollow rods, presenting greater sectional area than was absolutely necessary for the particular case, in order to increase their lateral resistance to the blows tending to produce vibration. boring is usually executed by contract. the approximate average cost in england may be taken at 1_s._ 3_d._ a foot for the first 30 feet; 2_s._ 6_d._ a foot for the second 30 feet; and continue in arithmetical progression, advancing 1_s._ 3_d._ a foot for every additional 30 feet in depth. this does not include the cost of tubing, conveyance of plant and tools, professional superintendence, or working in rock of unusual hardness, such as hard limestone and whinstone. a clause is usually inserted in the contract, to the effect that, if any unforeseen difficulty is met with in the course of the work, it is then paid for by the day, at a rate previously determined upon, until the difficulty has been overcome. chapter v. american tube well. this well consists of a hollow wrought-iron tube about 1-3/4 inch diameter, composed of any number of lengths from 3 to 11 feet, according to the depth required. the water is admitted into the tube through a series of holes, which extend up the lowest length to a height of 2-1/2 feet from the bottom. the position for a well having been selected, a vertical hole is made in the ground with a crowbar to a convenient depth; the well tube _a_, having the clamp _d_, monkey _c_, and pulleys _b_, fig. 95, previously fixed on it, is inserted into this hole. the clamp is then screwed firmly on to the tube from 18 inches to 2 feet from the ground, as the soil is either difficult or easy; each bolt being tightened equally, so as not to indent the tube. the pulleys are next clamped on to the tube at a height of about 6 or 7 feet from the ground, the ropes from the monkey having been previously rove through them. [illustration: tube well assembly. fig. 95.] the monkey is raised by two men pulling the ropes at the same angle. they should stand exactly opposite each other, and work together steadily, so as to keep the tube perfectly vertical, and prevent it from swaying about while being driven. if the tube shows an inclination to slope towards one side, a rope should be fastened to its top and kept taut on the opposite side, so as gradually to bring the tube back to the vertical. when the men have raised the monkey to within a few inches of the pulleys, they lift their hands suddenly, thus slackening the ropes and allowing the monkey to descend with its full weight on to the clamp. the monkey is steadied by a third man, who also assists to force it down at each descent. this man, likewise, from time to time, with a pair of gas-tongs, turns the tube round in the ground, which assists the process of driving, particularly when the point comes in contact with stones. particular attention must be paid to the clamp, to see that it does not move on the tube; the bolts must be tightened up at the first appearance of any slipping. when the clamp has been driven down to the ground, the monkey is raised off it, the screws of the clamp are slackened, and the clamp is again screwed to the tube, about 18 inches or 2 feet from the ground. after this, the monkey is lowered on to it, and the pulleys are then raised until they are again 6 or 7 feet from the ground. the driving is continued until but 5 or 6 inches of the well tube remain above the ground, when the clamp, monkey, and pulleys are removed, and an additional length of tube screwed on to that in the ground. this is done by first screwing a collar on to the tube in the ground, and then screwing the next length of tube into the collar, till it buts against the lower tube; a little white-lead must be placed on the threads of the collar before the ends of the tubes are screwed into it. the driving can thus be continued until the well has obtained the desired depth. soon after another length has been added, the upper length should be turned round a little with the gas-tongs, to tighten the joints, which have a tendency to become loose from the jarring of the monkey. care must be taken, after getting into a water-bearing stratum, not to drive through it, owing to anxiety to get a large supply. from time to time, and always before screwing on an additional length of tube, the well should be sounded, by means of a small lead attached to a line, to ascertain the depth of water, if any, and character of the earth which has penetrated through the holes perforated in the lower part of the well tube. as soon as it appears that the well has been driven deep enough, the pump is screwed on to the top and the water drawn up. it usually happens that the water is at first thick, and comes in but small quantities; but after pumping for some little time, as the chamber round the bottom of the well becomes enlarged, the quantity increases and the water becomes clearer. when sinking in gravel or clay, the bottom of the well tube is liable to become filled up by the material penetrating through the holes; and before a supply of water can be obtained, this accumulation must be removed by means of the cleaning pipes. the cleaning pipes are of small diameter, 1/2-inch externally, and the several lengths are connected together in the same way as the well tubes, by collars screwing on over the adjoining end of two pipes. to clear the well, one cleaning pipe after another is lowered into the well, until the lower end touches the accumulation; the pipes must be held carefully, for if one were to drop into the well it would be impossible to get it out without drawing the well. a pump is then attached to the upper cleaning pipe by means of a reducing socket; the lower end of the cleaning pipe is then raised and held about an inch above the accumulation by means of the gas-tongs: water is next poured down the well outside the cleaning pipe, and, being pumped up through the cleaning pipe, brings up with it the upper portion of the accumulation; the cleaning pipe is gradually lowered, and the pumping continued until the whole of the stuff inside the well tube is removed. the pump is then removed from the cleaning pipe, and the cleaning pipes are withdrawn piece by piece; and finally the pump is screwed on to the upper end of the tube well, fig. 96, which is then in working order. [illustration: tube well in working order. fig. 96.] the tube being very small, is in itself capable of containing only a limited supply of water, which would be exhausted by a few strokes of the pump; the condition, therefore, upon which alone these tube wells can be effective, is that there shall be a free flow of water from the outside through the apertures into the lower end of the tube. when the stratum in which the water is found is very porous, as in the case of gravel and some sorts of chalk, the water flows freely; and a yield has been obtained in such situations as great and rapid as the pump has been able to lift, that is 600 gallons an hour. in some other soils, such as sandy loam, the yield in itself may not be sufficiently rapid to supply the pump; in such cases, the effect of constant pumping is to draw up with the water from the bottom a good deal of clay and sand, and so gradually to form a reservoir, as it were, around the foot of the tube, in which water accumulates when the pump is not in action, as is the case in a common well. in dense clays, however, of a close and very tenacious character, the american tube well is not applicable, as the small perforations become sealed, and water will not enter the tube. when the stratum reached by driving is a quicksand, the quantity of sand drawn up from the water will be so great, that a considerable amount will have to be pumped before the water will come up clear; and even in some positions, when the quicksand is of great extent, the effect of the pumping may be to injure the foundations of adjoining buildings on the surface of the ground. the tube well cannot itself be driven through rock, although it might be used for drawing water from a subjacent stratum through a hole bored in the rock to receive it. subject to these conditions, these tube wells afford a ready and economical means for drawing water to the surface from a depth not exceeding 27 or 28 feet. chapter vi. well boring at great depths. the first well that was executed of great depth, and which gave rise to the adoption of tools which directed public attention to the art of well boring, was that for the city of paris by mulot, at the abattoir of grenelle. this was commenced in the year 1832; and after more than eight years' incessant labour, water rose, on the 26th of february, 1842, from the total depth of 1798 feet. subsequent to this, many wells have been sunk on the continent, with the hope of attaining the brine springs so often met with in the rhine provinces, or the springs destined for the supply of towns, and which are even deeper than the well of grenelle, reaching in some cases to the extraordinary depth of 2800 feet; but all of them, like the grenelle well, of small diameter. in their construction, however, the german engineers introduced some important modifications of the tools employed; and, amongst other inventions, euyenhausen imparted a sliding movement to the striking part of the tool used for comminuting the rock, so as to fall always through a certain distance; and thus, while he produced a uniform action upon the rock at the bottom, he avoided the jar of the tools. kind also began to apply his system to the working of the large excavations for the purpose of winning coal. whilst the art was in this state, and when he had already executed some very important works in germany, belgium, the north of france, creuzot, and seraing, the municipal council of paris determined to entrust him with the execution of a new well they were about to sink at passy. in sinking the well of passy, the weight of the trepan for comminuting the rock was about 1 ton 16 cwt., 1800 kilog.: the height through which it fell was about 60 centimètres; and its diameter was 3 feet 3-7/16 inches, 1 mètre. the rods were of oak, about 8 inches on the side, and the dimensions of the cutting tool were limited to 3 feet 3-7/16 inches because it worked the whole time in water; but generally the class of borings kind undertook were of such a description as justified resorting to tools of great dimensions. when sinking the shafts for winning coal, his operations required to be carried on with the full diameters of 10 feet or 14 feet; and he then drove a boring of 3 feet 4 inches diameter in the first instance, and subsequently enlarged this excavation. there can be no objection to executing artesian borings of this diameter, other than the probable exhaustion of the supply; particularly as it is now known that the yield of water by these methods is proportionate to the diameter of the column; though, strange as it may appear, the first opposition to kind's plan of sinking the well of passy was founded upon the assumption that he would not meet with a larger supply of water from the subcretaceous formations than had been met with at grenelle, where the diameter of the boring was at the bottom not more than 8 inches. it is now, however, proved that there is a direct gain in adopting the larger borings, not only as regards the quantity of water to be derived from them, but also in their execution, arising from the fact that the tools can be made more secure against the effects of torsion or of concussion against the sides of the excavation, which is the cause of the most serious accidents met with in well sinking. the trepan of m. kind contains some peculiar details, which are shown in figs. 97, 98. the trepan is composed of two principal pieces, the frame and the arms, both of wrought-iron, with the exception of the teeth of the cutting part, which are of cast steel. the frame has at the bottom a series of holes, slightly conical, into which the teeth are inserted, and tightly wedged up, fig. 99. these teeth are placed with their cutting edges on the longitudinal axis of the frame that receives them; and at the extremity of the frame there are formed two heads, forged out of the same piece with the body of the tool, which also carries two teeth, placed in the same direction as the others, but double their width, in order to render this part of the tool more powerful. by increasing the dimensions of these end teeth, the diameter of the boring can be augmented, so as to compensate for the diminution of the clear space caused by the tubing, necessarily introduced for security in traversing strata disposed to fall in, or for the purpose of allowing the water from below to escape at an intermediate level. [illustration: the trepan of m. kind. figs. 97-99.] above the lower part of the frame of the trepan is a second piece composed of two parts bolted together, and made to support the lower portion of the frame. this part of the machinery also carries two teeth at its extremities, which serve to guide the tool in its descent, and to work off the asperities left by the lower portion of the trepan. above this, again, are the guides of the machinery, properly speaking, consisting of two pieces of wrought-iron, arranged in the form of a cross, with the ends turned up, so as to preserve the machinery perfectly vertical in its movements, by pressing against the sides of the boring already executed. these pieces are independent of the blades of the trepan, and may be moved closer to it or farther away from it, as may be desired. the stem and the arms are terminated by a single piece of wrought-iron, which is joined to the frame with a kind of saddle-joint, and is kept in its place by means of keys and wedges. the whole of the trepan is finally jointed to the great rods that communicate the motion from the surface, by means of a screw-coupling, formed below the part of the tool which bears the joint; this arrangement permits the free fall of the cutting part, and unites the top of the arms and frame, and the rod, fig. 100. it has been proposed to substitute for this screw-coupling a keyed joint, in order to avoid the inconvenience frequently found to attend the rusting of the screw, which often interposes great difficulties in cases where it becomes necessary to withdraw the trepan. [illustration: the rod. fig. 100.] the sliding joint is the part of euyenhausen's invention most unhesitatingly adopted by kind, and it is one of the peculiarities of his system as contrasted with the processes formerly in use. so long as his operations were confined to the small dimensions usually adopted for artesian borings, he contented himself with making a description of joint with a free fall; a simple movement of disengagement regulating the height fixed by the machinery itself, like the fall of the monkey in a pile-driving machine; but it was found that this system did not answer when applied to large borings, and it also presented certain dangers. kind then, for the larger class of borings, availed himself of sliding guides, so contrived as to be equally thrown out of gear when the machinery had come to the end of the stroke, and maintained in their respective positions by being made in two pieces, of which the inner one worked upon slides, moving freely in the piece that communicated the motion to the striking part of the machinery. the two parts of the tool were connected with pins, and with a sliding joint, which, in the passy well, was thrown out of gear by the reaction of the column of water above the tool unloosing the click that upheld the lower part of the trepan, figs. 101 to 103. the changes thus made in the usual way of releasing the tool, and in guiding it in its fall were, however, matters of detail; they involved no new principle in the manner of well boring: and the modern authorities upon the subject consider that there was something deficient in kind's system of making the column of water act upon a disc by which the click was set in motion. this system, in fact, required the presence of a column of water not always to be commanded, especially when the borings had to be executed in the carboniferous strata. [illustration: sliding joints. figs. 101-103.] [illustration: wrought-iron joints. fig. 104.] [illustration: shell elevation.] the rods used for the suspension of the trepan, and for the transmission of the blows to it, were of oak; and this alone would constitute one of the most characteristic differences between the system of tools introduced by kind and those made by the majority of well-borers, but which, like the disengagement of the tool intended to comminute the rock, depended for its success upon the boring being filled with water. the resistance that the wood offers, by its elasticity, to the effects of any sudden jar, is also to be taken into account in the comparison of the latter with iron, for the iron is liable to change its form under the influence of this cause. the resistance to an effort of torsion need not, however, be much dwelt on, for the turn given to the trepan is always made when the tool is lifted up from its bed. for the purpose of making the rods, kind recommended that straight-grown trees, of the requisite diameter, should be selected, rather than they should be made of cut-timber, as there is less danger of the wood warping, and the character of the wood is more homogeneous. he generally used these trees in lengths of about 50 feet, and he connected them at the ends with wrought-iron joints, fitting one into the other, fig. 104. the ironwork of the joints is made with a shoulder underneath the screw-coupling, to allow the rods to be suspended by the ordinary crow's foot during the operation of raising or lowering them. in the works executed at passy there was a kind of frame erected over the centre of the boring, of sufficient height to allow of the rods being withdrawn in two lengths at a time, thus producing a considerable economy of time and labour. [illustration: shell plan. figs. 105, 106.] nearly all the processes yet introduced for removing the products of the excavation must be considered to be, more or less, defective, because all are established on the supposition that the comminuting tool must be withdrawn, in order that the shell, or other tool intended to remove the products of the working of the comminutor, may be inserted. this remark applies to kind's operations at passy and elsewhere, as he removed the rock detached from the bottom of the excavation by a shell, figs. 105, 106, which was a modification of the tool he invariably employs for this purpose. it consisted of a cylinder of wrought-iron, suspended from the rods by a frame, and fastened to it, a little below the centre of gravity, so that the operation of upsetting it, when loaded, could be easily performed. this cylinder was lowered to the level of the last workings of the trepan, and the materials already detached by that instrument were forced into the tool, by the gradual movement of the latter in a vertical direction. some other implements, employed by kind for the purpose of removing the products of the excavation in the shafts for the coal-mines of the north of france, were ingenious, and well adapted to the large dimensions of the shafts; but they were all, in some degree, exposed to the danger of becoming fixed, if used in the small borings of artesian wells, by the minute particles of rocks falling down between their sides and the excavation from above. their use was therefore abandoned, and the well of passy was cleared out with the shell, the bottom of which was made to open upwards, with a hinged flap, which admitted the finer materials detached by the trepan. there were also several tools for the purpose of withdrawing the broken parts of the machinery from the excavation, or whatever substances might fall in from above; and all were marked by a great degree of simplicity, but they did not differ enough from those generally used for the same purpose to merit further remarks. in fact, the accidents intended to be guarded against or remedied are so precisely alike in all cases, that there can be little variety in the manufacture of these instruments. but there is no doubt that kind deprived himself of a valuable appliance in not using the ball-clack, _la soupape à boulet_, that other well-borers employ, fig. 107. [illustration: ball-clack. fig. 107.] at passy great strength was given to the head of the striking tool, and to the part of the machinery applied to turn the trepan, because the great weight of the latter superinduced the danger of its breaking off under the influence of the shock, and because the solidity of this part of the machinery necessarily regulated the whole working of the tool. the head of the boring arrangement was connected with the balance-beam of the steam-engine by a straight link-chain, with a screw-coupling, admitting of being lengthened as the trepan descended, figs. 108, 109. the balance-beam, in order to increase its elastic force in the upward stroke, is in kind's works made of wood, in two pieces; the upper one being of fir and the lower one of beech. the whole of the machinery is put in motion by steam, which is admitted to the upper part of the cylinder, and presses it down, and thus raises the tool at the other end of the beam to that part in connection with the cylinder. the counterpoise to the weight of the tools is also placed upon the cylinder-end of the beam. the cylinder receives the steam through ports that are opened and closed by hand, like those of a steam-hammer; so that the number of the strokes of the piston may be increased or diminished, and the length of the strokes may be increased, as occasion may require. [illustration: side elevations on balance-beam connection. figs. 108, 109.] the balance-beam is continued beyond the point where the piston is connected with it, and it goes to meet the blocks placed to check the force of the blow given by the descent of the tool. the guides of the piston-head are attached to the part of the machinery that acts in this manner; but at passy, kind made the balance-beam work upon two free plummer-blocks, or blocks having no permanent cover, that they might be more easily moved whenever it was necessary to displace the beam, for the purpose of taking up or letting down the rods, or for changing the tools; for the balance-beam was always immediately over the centre of the tools, and it therefore had to be displaced every time that the latter were required to be changed. this was effected by allowing the beam to slide horizontally, so as to leave the mouth of the pit open. the counter-check, above mentioned, likewise prevented the piston from striking the cylinder cover with too great a force, when it was brought back by the weight of the tools to its original position. the operation of raising and lowering the rods, or of changing the tools, was performed at passy by a separate steam-engine, and the shell was discharged into a special truck, moving upon a railway expressly laid for this purpose in the great tower erected over the excavation. all these arrangements were in fact made with the extreme attention to the details of the various parts of the work which characterizes the proceedings of foreign engineers, and conduces so much to their success. the beating, or comminution of the rock, was usually effected at passy at the rate of from fifteen strokes to twenty strokes a minute. the rate of descent, of course, differed in a marked manner, according to the nature of the rock operated upon; but, generally speaking, the trepan was worked for the space of about eight hours at a time, after which it was withdrawn, and the shell let down in order to remove the _débris_. the average number of men employed in the gang, besides the foreman, or the superintendent of the well, was about fourteen: they consisted of a smith and hammerman, whose duty it was to keep the tools in order; and two shifts of men entrusted with the excavation, namely, an engine-driver and stoker, a chief workman, or sub-foreman, and three assistants. the total time employed in sinking the shafts executed upon this system in the north of france, where it has been applied without meeting with the accidents encountered in the passy well, was found to be susceptible of being divided in the following manner: from 25 per cent. to 56 per cent. was employed in manoeuvring the trepan; from 11 per cent. to 14-1/2 per cent. in raising and lowering the tools; from 19 per cent. to 21 per cent. in removing the materials detached from the rocks, and cleaning out the bottom of the excavation; and from 8 per cent. to 10-1/2 per cent. was lost, owing to the stoppage of the engines, or to the accidents from broken tools, or to other causes always attending these operations. in the well of passy there was, of course, a considerable difference in the proportions of the time employed in the various details of the work; and the long period occupied in obviating the effects of the slips which took place in the clays, both in the basement beds of the paris basin and in the subcretaceous strata, would render any comparison derived from that well of little value; but it would appear that, until the great accident occurred, the various operations went on precisely as kind had calculated upon. kind-chaudron system. [illustration: section through kind-chaudron well at durham. fig. 110.] in the year 1872 emerson bainbridge, c.e., drew attention to the kind-chaudron system of sinking mine shafts through water-bearing strata, without the use of pumping machinery, in a paper read before the institute of civil engineers. as the operation is almost identical with that which would have to be carried through in the case of a well sunk through an upper series of water-bearing strata, of minor importance or of impure quality, past rock and into the lower water strata, as for instance through tertiaries and chalk into the lower greensand, the following extract from bainbridge's paper may be read with interest. in the first place, it may be desirable to describe briefly the system of sinking hitherto pursued in passing through strata yielding large quantities of water. the most important sinkings of this character have been carried out in the county of durham, to the east of the point at which the permian overlie the carboniferous rocks. in this district there is a thin bed of sand between the permian rock and the coal measures. towards this bed the feeders of water are generally found to increase, and in the sand there is usually a large reservoir of water. the mode of sinking will be understood by reference to fig. 110. whilst sinking in hard rock, it has ordinarily been the custom to place iron curbs, or cribs, wherever a bed of stone appeared to form a natural barrier between two distinct feeders of water. thus it has frequently happened that important feeders have been tubbed back, rendering much less pumping power necessary than would have been required had all the feeders been allowed to accumulate in the shaft. as will be seen by fig. 110, the number of wedging cribs employed is no less than thirteen in 250 feet. the cribs forming the foundation of each set of tubbing are generally much more massive and costly than the segments of tubbing. [illustration: cast-iron tubbing. fig. 111.] [illustration: wooden tubbing. fig. 112.] [illustration: end elevation showing arrangement at extensive sinking. fig. 113.] [illustration: side elevation showing arrangement at extensive sinking. fig. 114.] [illustration: pass pipe. fig. 115.] [illustration: pass pipe. fig. 116.] [illustration: ball type of pressure equalizer. fig. 118.] the process of fixing the crib is as follows;--the diameter of the shaft is made about 30 inches larger than that of the inside of the tubbing. when a bed of rock, which may be considered sufficiently hard and close to separate the feeders above and below it, is reached, the shaft is contracted to the diameter of the tubbing, and a smooth horizontal face is made on which to place the wedging crib. the wedging crib, which usually consists of segments about 4 feet long by 6 inches high by 14 inches wide, is then placed on the bed. to give the crib a firm and secure position, it is tightly wedged with wood, both behind and between the joints; the tubbing is then built upon it to the next wedging crib, which rests upon a bell-shaped section of rock. when the tubbing nearly reaches this crib, the rock is removed piece by piece, and the top ring of tubbing is placed close up against the crib. it will thus be seen that the fixing of each crib is a costly process, often causing considerable delay. in some cases, where it has been difficult to find suitable foundations for intermediate wedging cribs, the whole of the water-bearing rocks have been sunk through without attempting to stop the feeders separately, and no tubbing has been placed in the shaft till the wedging crib could be fixed below the lowest feeder. this process is more expeditious where there are small quantities of water; but where the water is excessive greater delay is caused by contending with it than from putting in numerous sets of tubbing to stop the feeders separately. the tubbing used in england has almost invariably been of cast-iron; on the continent, till recently, tubbing of wood has chiefly been used. illustrations of both descriptions are shown by figs. 111 and 112. figs. 113, 114, show, in elevation, the plant and the arrangements generally in use at extensive sinkings. where the water is in large quantities it is usually pumped by an engine erected for the purpose, assisted by the engine or engines intended to be employed to raise the coal. a small capstan engine is used for passing the men and material up and down the pit during the sinking, such engine being provided also with a drum on slow motion, which is used for heavy weights. the continual pumping, the placing of cribs, and the fixing of the tubbing are proceeded with till the lowest feeder is reached, when a hard bed is sought for on which to fix the lowest wedging crib. in all cases the water has to be pumped out before the wedging crib, which forms the foundation of each set of tubbing, can be placed. from this description it will be understood that the sinkers, who number from ten to twelve at one time, working four hours at a shift in a pit, say, 14 feet in diameter, are compelled to work in water until all the tubbing is fixed. this causes a serious obstacle to blasting, and in other ways delays the progress of the work. the tubbing used for damming back the water is generally in segments from 1 foot to 3 feet high, and about 4 feet in length, the thickness varying from half an inch to 3-3/4 inches. it is kept in position by packing with wood behind the joints; and is made water-tight by placing between the segments pieces of wood sheeting about half an inch thick, which are wedged when all the tubbing is fixed, usually twice with wood, and sometimes once with iron wedges. [illustration: pressure equalizing valve in the wedging crib. fig. 117.] to equalize the pressure of water and gas behind the different sets of tubbing, pass pipes, figs. 115 and 116, are sometimes used. another expedient to effect this is to have a valve, working upwards, placed in the wedging crib, fig. 117. a ball is also sometimes used, fig. 118. the various modes of piercing beds of quicksand are;--by hanging tubbing to that already fixed, and adding fresh rings as the sand is removed. this is only practicable when the quantity of sand is inconsiderable. by heavily weighting a cylinder of iron of the same size as the shaft, and thus forcing it down through the sand. by keeping back the sand by the use of piles--a resource that can only be recommended when the bed of sand is not of great thickness. when the water is excessive, by using pneumatic agency. as these operations are apart from our immediate subject we need not further discuss them. m. chaudron's system, which is a modification of kind's, is divisible into the following distinct processes, which consist of;-the erection of the necessary machinery on the surface, and the opening of the mine. the boring of the pits to the lowest part of the water-bearing strata. the placing of the tubbing. the introduction of cement behind the tubbing to complete its solidity. the extraction of the water from the pits, and the placing of the wedging cribs, or "faux cuvelage," below the moss box. [illustration: surface plant elevation. fig. 119.] [illustration: surface plant elevation. fig. 120.] [illustration: surface plant plan. fig. 121.] figs. 119 to 121 show in elevations and in plan the plant usually employed on the surface. o is a small capstan engine, having a cylinder 20 inches in diameter and a stroke of 32 inches, working on the third motion. attached to this engine, and working in the small pit c, is a counterbalance weight. this engine is used for raising and lowering boring tools, and for lifting the _débris_ resulting from the boring. as far as the platform, which is about 10 feet from the surface, the pit has a diameter of 19 feet, or 4 feet more than the diameter of the pit below. a at level of about 38 feet above this platform there is a tramway on which small trucks run, carrying the _débris_ cylinder on one side, and the boring tools on the other. at a level of 48 feet above the platform are placed supports for the wooden spears to which the boring tools are attached. the machinery for boring is worked by a cylinder, which has a diameter of 39-1/3 inches, and a full stroke of 39-1/3 inches, the usual stroke varying from 2 feet to 3 feet. a massive beam of wood transmits motion from this cylinder to the boring apparatus, the connection between the beam and the piston-rod and the beam and the boring tools being made by a chain. the engine-man sits close to the engine, and applies the steam above the piston only. the down stroke of the boring tools is caused by the sudden opening of the exhaust, and a frame then prevents the shock of the boring rods from being too severe. the engines work at speeds varying from 12 to 18 strokes a minute, according to the character of the strata passed through. [illustration: the small trepan. fig. 122.] [illustration: the small trepan. fig. 123.] [illustration: the small trepan. fig. 124.] [illustration: plan of guide b. fig. 125.] [illustration: swivelled ring front elevation. fig. 126.] [illustration: swivelled ring side elevation. fig. 127.] [illustration: large trepan front elevation. fig. 128.] [illustration: large trepan side elevation. fig. 129.] [illustration: large trepan component, fig. 130.] [illustration: trepan teeth. figs. 131-134.] after the working platform is fixed, the first boring tool applied is the small trepan, figs. 122 to 125. this tool is attached to the wooden beam by the same arrangement shown by fig. 109. the boring tools can be lowered at pleasure by means of an adjusting screw. next in order comes the handle for boring. this is worked by four men on the platform, and is turned by the aid of a swivel. attached to the handle-piece are wooden rods, made from riga pitch pine. these rods are 59 feet in length and 7-3/4 inches square. a swivelled ring, figs. 126, 127, is attached to the rope when raising and lowering the boring rods. the small trepan cuts a hole 4 feet 8-3/4 inches in diameter, and has fourteen teeth, fitted in cylindrical holes and secured by pins entering through circular slots. the teeth are steeled. at a distance of 4 feet 4 inches above the main teeth of the trepan there is an arm, with a tooth at each end. this piece answers the purpose of a guide, and at the same time removes irregularities from the sides of the hole. at a distance of 13 feet 6 inches above the main teeth are the actual guides, consisting of two strong arms of iron fixed on the tool, and placed at right-angles to each other. the hole made by the small trepan is not kept at any fixed distance in advance of the full-sized pit, but the distance generally varies from 10 to 30 yards. with the small trepan, which weighs 8 tons, the progress varies from 6 to 10 feet a day. the large trepan, figs. 128 to 130, weighs 16-1/2 tons, is forged in one solid piece, and has twenty-eight teeth. a projection of iron forms the centre of this trepan, and fits loosely into the hole made by the small trepan, acting as a guide for the tool. at a distance of 7 feet 6 inches above the teeth, a guide is sometimes fixed on the frame, but is not furnished with teeth. at a distance of 13 feet 3 inches from the teeth are two other guides at right-angles to each other. these guides are let down the pit with the boring tool, the hinged part of the guides being raised whilst passing through the beams at the top of the pit, which are only 6 feet 7 inches apart. when the tool is ready to work, the two arms are let down against the side of the pit, and are hung in the shaft by ropes, thus acting as a guide for the trepan, which moves through them. to provide against a shock to the spears when the trepan strikes the rock on the down stroke, at the upper part of the frame a slot motion is arranged, the play of which amounts to about half an inch. the teeth of the large trepan are not horizontal, but are deeper towards the inside of the pit, the face of the inside tooth being 3-3/4 inches lower than the outside. the object of this is to cause the _débris_ to drop at once into the small hole, by the face of the rock at the bottom of the pit being somewhat inclined. the teeth used, figs. 131 to 134, are the same both for the large and the small trepan, and weigh about 72 lb. each. as a rule, only one set of teeth is kept in use, this set working for twelve hours, the alternate twelve hours being employed in raising the _débris_. this time is divided in about the following proportions;--boring, twelve hours; drawing the rods, one hour to five hours, according to depth; raising the _débris_, two hours; and lowering the rods one hour to five hours. the maximum speed of the larger trepan may be taken at about 3 feet a day. the ordinary distance sunk is not more than 2 feet a day, and in flint and other hard rocks the boring has proceeded as slowly as 3 inches a day. [illustration: tools used in boring. figs. 135, 136.] [illustration: epicycloidal hook. figs. 137, 138.] [illustration: rod disconnection key. figs. 139, 140.] [illustration: connections to the trepan and spears or rods. fig. 141, 142.] the _débris_ in the small bore-hole contains pieces of a maximum size of about 8 cubic inches. in the large boring, pieces of rock measuring 32 cubic inches have been found. as a rule, however, the material is beaten very fine, having much the appearance of mud or sand. in both the large and the small borings the _débris_ is raised by a shell, similar to figs. 105, 106, and in this system consisting of a wrought-iron cylinder, 3 feet 3 inches in diameter by 6 feet 9 inches long, and containing two flap-valves at the bottom, through which the excavated material enters. this apparatus is passed down the shaft by the bore-rods, and it is moved up and down through a distance varying from 6 to 8 inches, for about a quarter of an hour, and is then drawn up and emptied. in some cases where the rock is hard, three sizes of trepan are used consecutively, the sizes being 5 feet, 8 feet, and 13 feet. the several other tools and appliances used during the boring operations are shown, figs. 135 to 140, including the key, figs. 139, 140, used at the surface to disconnect the rods, the hook on which each rod is hung after being raised to the high platform and there detached, the bar upon which the hooks are moved, and the fork for suspending the rods or tools from the rollers when it is desired to move the rods or tools from above the shaft. [illustration: connections to the trepan and spears or rods. figs. 143-146.] figs. 141 to 146 are of the connections to the trepan and spears or rods. should broken tools fall into the shaft, several varieties of apparatus are used for their recovery. in case of broken rods of any kind having a protuberance that can be clutched, a hook or crow, figs. 137, 138, of an epicycloidal form, enables the object to be taken hold of very readily. where the broken part has no shoulder which can be held, but is simply a bar, the apparatus shown by figs. 147, 148, is employed. this is composed of two parts. the rods, the bottom of which have teeth inside, are prevented from diverging by the cone and slide on the main rods. when passed over a rod or pipe, they clutch it by means of the teeth, and draw it up. chaudron has, by this tool, raised a column of pipes 295 feet in length and 8 inches in diameter. an instrument, called a "grapin," figs. 149, 150, is used for raising broken teeth or other small objects which may have fallen into the bottom of the shaft. this tool also has one part sliding in the other, and is lowered with the claws closed. the parts are moved by two ropes worked from the surface. by weighting the cross-bar, which is attached to the moving parts, the pressure desired can be exerted on the claws. the weight is then lifted, the claws are opened, and are made to close upon the substance to be raised. this instrument is now seldom required. [illustration: pipe or rod recovery tool. figs. 147, 148.] [illustration: grapin. figs. 149, 150.] in boring shafts in the manner described, without being able to prove in the usual way the perpendicularity of the shaft, it might be feared that the system would be open to objection on this account. it appears, however, that in all cases where chaudron has sunk shafts by this system he has succeeded in making them perfectly vertical. this is ensured by the natural effect of the treble guide, which the chisels and the two sets of arms attached to the boring tools afford, and by the fact that if the least divergence from a plumb-line is made by the boring tool, the friction of the tool upon one side of the shaft is so great as to cause the borers to be unable to turn the instrument. boring alternately with the large and the small instrument, the shaft is at length sunk to the point at which the lowest feeder of water is encountered. in a new district this has to be taken, to some extent, at hazard; but where pits have been sunk previously, it is not difficult to tell, by observing the strata, almost the exact point at which the bottom of the tubbing may be safely fixed. this point being ascertained, the third process is arrived at. [illustration: hydraulic test apparatus. fig. 151.] as the object of placing tubbing in a shaft is effectually to shut off the feeders, which for water supply may have some bad qualities, and to secure a water-tight joint at the base, it is important that the bed on which the moss box has to rest should be quite level and smooth. this is attained by the use of a tool, termed a "scraper," attached to the bore-rods, the blades being made to move round the face of the bed intended for the moss box. the tubbing employed is cast in complete cylinders. at maurage each ring has an internal diameter of 12 feet and is 4 feet 9 inches high. each ring has an inside flange at the top and bottom, and also a rib in the middle, the top and bottom of the ring being turned and faced. the rings of tubbing are attached to each other by twenty-eight bolts 1·1 inch in diameter, passed through holes bored in the flanges. the tubbing is suspended in the pit by means of six rods, which are let down by capstans placed at a distance of 30 feet above the top of the pit. these machines work upon long screws. when a new ring of tubbing is added, the rods are detached at a lower level, and are hung upon chains, thus leaving an open space for passing it forward. before each ring is put into the pit it is tested by hydraulic apparatus, fig. 151. the tubbing is usually proved to one-half more pressure than it is expected to be subjected to. at maurage, where a length of 550 feet of tubbing has to be put in, the chief particulars respecting it are;- +-----------+---------+------------+--------------+--------------+ | | | | | pressure | | | | | pressure | at which | | | length. | thickness. | expected. | tubbing is | | | | | | proved. | +-----------+---------+------------+--------------+--------------+ | | | | lbs. a | lbs. a | | | feet. | inches. | square inch. | square inch. | | | | | | | | top | 130 | 1·17 | 30 | 45 | | | 60 | 1·31 | 60 | 90 | | | 60 | 1·57 | 90 | 135 | | | 60 | 1·76 | 120 | 180 | | | 60 | 1·96 | 150 | 225 | | | 60 | 2·16 | 180 | 270 | | | 60 | 2·35 | 210 | 315 | | bottom | 60 | 2·55 | 240 | 360 | +-----------+---------+------------+--------------+--------------+ the joints between the rings of tubbing are made with sheet lead one-eighth of an inch thick, coated with red-lead. the lead is allowed to obtrude from the joint one-third of an inch, and is wedged up by a tool which has a face one-twelfth of an inch thick. the mode of suspending the tubbing to the rods will be understood by referring to figs. 152 to 154. the rods are attached to a ring by the bolts connecting one ring of tubbing with another. the bottom ring of tubbing and the ring carrying the moss box have their top flange turned inwards, but their bottom flange outwards. a strong web of iron, forming the base of a tube 16-1/2 inches in diameter, is attached to the tubbing. the object of this tube is to cause the water in the shaft to ease the suspension rods, by bearing part of the weight of the tubbing. cocks to admit water are placed at intervals up the tube, by which means the weight upon the rods can be easily regulated, so that not more than one-tenth to one-twentieth of the weight of the tubbing is suspended by the rods at one time. the ring holding the moss box is hung from the bottom joint in the tubbing by sliding rods. [illustration: mode of suspending the tubbing to the rods. figs. 152-154.] the arrangement of the moss box which forms the base of the tubbing is one of the most important points requiring attention in this system of sinking. ordinary peat moss is used. it is enclosed in a net, which, with the aid of springs, keeps it in its place during the descent of the tubbing. when the moss box, which hangs on short rods fixed to the tubbing, reaches the face of rock, it is dropped gently upon it, and the whole weight of the tubbing is allowed to rest upon the bed. this compresses the moss, the capacity of the chamber holding it is diminished, and the moss is forced against the sides of the shaft, thus forming a water-tight joint, past which no water can escape. this completes the third process. it may be noted that up to this point the following important differences between this and the ordinary system of placing tubbing are to be observed;--the tubbing, on reaching its bed, bears the aggregate pressure of all the feeders of water which have been met with in the shaft. the tubbing, having been passed down the shaft in the manner described, no wedging behind, or other modes of consolidating it in the shaft, have been carried out. the connection between each ring of tubbing is so carefully made, that the repeated wedging of the joints, as in the ordinary system, is rendered unnecessary. the pit is still full of water up to the ordinary level. under these conditions the next process is;--the introduction of cement behind the tubbing to complete its solidity. [illustration: close ladle, figs. 155, 156.] before the water is removed, the annular space between the tubbing and the sides of the shaft is filled with hydraulic cement, to render the tubbing impermeable, by a process of consolidation, less liable to the effect of any pressure of water or gas which may be exerted towards the centre of the shaft. the cement is inserted behind the tubbing by close ladles, figs. 155, 156, capable of holding 44 gallons, and consisting of two iron plates, one-eighth of an inch thick, fixed on two wooden uprights 3-1/8 inches square. this apparatus is curved to suit the mean circumference of the space to be concreted. a piston is placed at the top of the ladle, and to this piston is attached a rod, which can be moved from the surface; a door is also attached to the piston. the ladle containing the concrete is passed down behind the tubbing by means of a windlass at the surface, and when it reaches the lowest point, the piston is pushed down and the cement allowed to escape from the chamber. the weight of the cement and the ladle is sufficient with a little ballast to enable it to descend easily. a number of experiments have been made to discover a cement which will not harden too quickly, and which, when hardened, will form a perfectly compact and solid mass. a composition having the following proportions has been found the best;--hydraulic lime, from the lias near metz, slaked by sprinkling, 1 part; picked sand, from the vosges sandstone, 1 part; trass, from andernacht on the rhine, 1 part; cement from ropp (haute saone), 1/4 part. six men are employed in putting in the cement;--two at the windlass for letting down the ladle, two for working the rods attached to the piston, and two on the working platform. the rods referred to have been found such an inconvenience, that lately a rope on another windlass has been used, and an appliance arranged for dropping the piston by moving the rope. [illustration: sectional elevation showing base to the tubbing. fig. 157.] when a sufficient time has elapsed for the cement to harden, the water within the tubbing, now effectually separated from the feeders, is drawn out by a bucket worked by the crab engine,--an operation which occupies from one to three weeks, according to circumstances. when concluded, the joint between the moss box and the rock bed can be examined. in some cases this joint is considered sufficient; but it is generally thought desirable to form a base to the tubbing by building a few feet of brickwork in cement on a ring or crib of wood, as in fig. 157. another wooden crib is then placed on the top of this brickwork, and above this, two cast-iron segmental wedging cribs with a broad bed also wedged perfectly tight. on the base so prepared, four or more rings of tubbing in segments are fixed, the top ring coming close against the bottom of the moss box. this being done the work is completed, and the sinking of the shaft is continued in the ordinary way. the application of the boring trepan is not to be recommended in the sinking of the dry part of the shaft. the use of the tool would cause the sinking to extend over a longer period, since the breaking of the rock passed through into such minute particles would lead to loss of time. dru's system. [illustration: dru's system. sectional elevation showing surface arrangement. fig. 158.] the system applied by dru is worthy of attention, not so much on account of the novelty of the invention, or of any new principle involved in it, as on account of the contrivances it contains for the application of the tool, "_à chute libre_," or the free-falling tool, to artesian wells of large diameters. it has been already explained that under kind's arrangements the trepan was thrown out of gear by the reaction of the water which was allowed to find its way into the column of the excavation; but that it is not always possible to command the supply of the quantity necessary for that purpose; and even when possible, the clutch kind adopted was so shaped as to be subject to much and rapid wear. dru, with a view to obviate both these inconveniences, made his first trepan similar to that shown in fig. 101, in which it will be seen that the tool was gradually raised until it came in contact with the fixed part of the upper machinery, when it was thrown out of gear. the bearings of the clutch were parallel to the horizontal line, and were found in practice to be more evenly worn, so that this instrument could be worked sometimes from eight days to fourteen days without intermission; whereas, on kind's system, the trepan was frequently withdrawn after two days' or three days' service. we take the following complete account of the system from a paper read by m. dru at the conservatoire des arts et métiers, paris, 6th june, 1867. it will be seen from figs. 158, 159, that the boring rod a is suspended from the outer end of the working beam b, which is made of timber hooped with iron, working upon a middle bearing, and is connected at the inner end to the vertical steam cylinder c, of 10 inches diameter and 39 inches stroke. the stroke of the boring rod is reduced to 22 inches, by the inner end of the beam being made longer than the outer end, serving as a partial counterbalance for the weight of the boring rod. the steam cylinder is shown enlarged in fig. 160, and is single-acting, being used only to lift the boring rod at each stroke, and the rod is lowered again by releasing the steam from the top side of the piston; the stroke is limited by timber stops both below and above the end of the working beam b. the boring tool is the part of most importance in the apparatus, and the one that has involved most difficulty in maturing its construction. the points to be aimed at in this are,--simplicity of construction and repairs; the greatest force of blow possible for each unit of striking surface; and freedom from liability to get turned aside and choked. [illustration: elevation showing beam connected to rods, fig. 159.] [illustration: steam cylinder. fig. 160.] [illustration: single chisels. figs. 161, 162.] the tool used in small borings is a single chisel, as shown in figs. 161, 162; but for the large borings it is found best to divide the tool-face into separate chisels, each of convenient size and weight for forging. all the chisels, however, are kept in a straight line, whereby the extent of striking surface is reduced; and the tool is rendered less liable to be turned aside by meeting a hard portion of flint on a single point of the striking edge, which would diminish the effect of the blow. [illustration: tools for large borings. figs. 163-169.] the tool is shown in figs. 163 to 169, and is composed of a wrought-iron body d, connected by a screwed end e to the boring rod, and carrying the chisels f f, fixed in separate sockets and secured by nuts above; two or four chisels are used, or sometimes even a greater number, according to the size of the hole to be bored. this construction allows of any broken chisel being easily replaced; and also, by changing the breadth of the two outer chisels, the diameter of the hole bored can be regulated exactly as may be desired. when four chisels are used, the two centre ones are made a little longer than the others, as shown in fig. 167, to form a leading hole as a guide to the boring rod. a cross-bar g, of the same width as the tool, guides it in the hole in the direction at right-angles to the tool; and in the case of the larger and longer tools a second cross-bar higher up, at right-angles to the first and parallel to the striking edge of the tool, is also added. [illustration: free-falling tools. figs. 170-173.] if the whole length of the boring rod were allowed to fall suddenly to the bottom of a large bore-hole at each stroke, frequent breakages would occur; it is therefore found requisite to arrange for the tool to be detached from the boring rod at a fixed point in each stroke, and this has led to the general adoption of _free-falling tools_. m. dru's plan of self-acting free-falling tool, liberated by reaction, is shown in side and front view in figs. 170 to 173. the hook h, attached to the head of the boring tool d, slides vertically in the box k, which is screwed to the lower extremity of the boring rod; and the hook engages with the catch j, centred in the sides of the box k, whereby the tool is lifted as the boring rod rises. the tail of the catch j bears against an inclined plane l, at the top of the box k; and the two holes carrying the centre-pin i of the catch, are made oval in the vertical direction, so as to allow a slight vertical movement of the catch. when the boring rod reaches the top of the stroke, it is stopped suddenly by the tail end of the beam b, fig. 159, striking upon the wood buffer-block e; and the shock thus occasioned causes a slight jump of the catch j in the box k; the tail of the catch is thereby thrown outwards by the incline l, as shown in fig. 172, liberating the hook h, and the tool then falls freely to the bottom of the bore-hole, as shown in fig. 173. when the boring rod descends again after the tool, the catch j again engages with the hook h, enabling the tool to be raised for the next blow, as in fig. 171. [illustration: self-acting free-falling tools. figs. 174-178.] another construction of self-acting free-falling tool, liberated by a separate disengaging rod, is shown in side and front view in figs. 174 to 178. this tool consists of four principal pieces, the hook h, the catch j, the pawl i, and the disengaging rod m. the hook h, carrying the boring tool d, slides between the two vertical sides of the box k, which is screwed to the bottom of the boring rod; and the catch j works in the same space upon a centre-pin fixed in the box, so that the tool is carried by the rod, when hooked on the catch, as shown in fig. 175. at the same time the pawl i, at the back of the catch j, secures it from getting unhooked from the tool; but this pawl is centred in a separate sliding hoop n, forming the top of the disengaging rod m, which slides freely up and down within a fixed distance upon the box k; and in its lowest position the hoop n rests upon the upper of the two guides p p, fig. 174, through which the disengaging rod m slides outside the box k. in lowering the boring rod, the disengaging rod m reaches the bottom of the bore-hole first, as shown in figs. 174, 175, and being then stopped it prevents the pawl i from descending any lower; and the inclined back of the catch j sliding down past the pawl, the latter forces the catch out of the hook h, as shown in fig. 176, thus allowing the tool d to fall freely and strike its blow. the height of fall of the tool is always the same, being determined only by the length of the disengaging rod m. the blow having been struck, and the boring rod continuing to be lowered to the bottom of the hole, the catch j falls back into its original position, and engages again with the hook h, as shown in fig. 177, ready for lifting the tool in the next stroke. as the boring rod rises, the tail of the catch j trips up the pawl i in passing, as shown in fig. 176, allowing the catch to pass freely; and the pawl before it begins to be lifted returns to the original position, shown in fig. 177, where it locks the catch j, and prevents any risk of its becoming unhooked either in raising or lowering the tool in the well. the boring tool shown in figs. 163, 164, which was employed for boring a well of 19 inches diameter, weighs 3/4 ton, and is liberated by reaction, by the arrangement shown in figs. 170 to 173; and the same mode of liberation was applied in the first instance to the larger tool, shown in figs. 166 to 169, employed in sinking a well of 47 in. diameter at butte-aux-cailles. the great weight of the latter tool, however, amounting to as much as 3-1/2 tons, necessitated so violent a shock for the purpose of liberating the tool by reaction, that the boring rods and the rest of the apparatus would have been damaged by a continuance of that mode of working; and m. dru was therefore led to design the arrangement of the disengaging rod for releasing the tool, as shown in figs. 174, 175. in this case the cross-guide g fixed upon the tool is made with an eye for the disengaging rod m to work through freely. for borings of small diameter, however, the disengaging rod cannot supersede the reaction system of liberation, as the latter alone is able to work in borings as small as 3-1/4 inches diameter; and a bore-hole no larger than this diameter has been successfully completed by m. dru with the reaction tool to a depth of 750 feet. the boring rods employed are of two kinds, wrought-iron and wood. the wood rods seen in figs. 159, 179, are used for borings of large diameter, as they possess the advantage of having a larger section for stiffness without increasing the weight; and also when immersed in water the greater portion of their weight is floated. the wood for the rods requires to be carefully selected, and care has to be taken to choose the timber from the thick part of the tree, and not the toppings. in france, lorraine, or vosges, deals are preferred. [illustration: lantern. fig. 179.] [illustration: boring rod sockets. figs. 180-182.] the boring rods, whether of wood or iron, are screwed together either by solid sockets, as in fig. 181, or with separate collars, as in figs. 180, 182. the separate collars are preferred for the purpose, on account of being easy to forge; and also because, as only one half of the collar works in coupling and uncoupling the rods, while the other half is fixed, the screw-thread becomes worn only at one end, and by changing the collar, end for end, a new thread is obtained when one is worn out, the worn end being then jammed fast as the fixed end of the collar. the boring rod is guided in the lower part of the hole by a lantern r, fig. 159, shown to a larger scale in fig. 179, which consists of four vertical iron bars curved in at both ends, where they are secured by movable sockets upon the boring rod, and fixed by a nut at the top. by changing the bars, the size of the lantern is readily adjusted to any required diameter of bore-hole, as indicated by the dotted lines. in raising up or letting down the boring rod, two lengths of about 30 feet each are detached or added at once, and a few shorter rods of different lengths are used to make up the exact length required. the coupling screw s, fig. 158, by which the boring rod is connected to the working beam b, serves to complete the adjustment of length; this is turned by a cross-bar, and then secured by a cross-pin through the screw. [illustration: conical socket. fig. 183.] [illustration: crow's foot. fig. 184.] in ordinary work, breakages of the boring rod generally take place in the iron, and more particularly at the part screwed, as that is the weakest part. in the case of breakages, the tools usually employed for picking up the broken ends are a conical screwed socket, shown in fig. 183, and a crow's foot, shown in fig. 184; the socket being made with an ordinary v-thread for cases where the breakage occurs in the iron; but having a sharper thread, like a wood screw, when used where the breakage is in one of the wood rods. in order to ascertain the shape of the fractured end left in the bore-hole, and its position relatively to the centre line of the hole, a similar conical socket is first lowered, having its under surface filled up level with wax, so as to take an impression of the broken end, and show what size of screwed socket should be employed for getting it up. tools with nippers are sometimes used in large borings, as it is not advisable to subject the rods to a twist. when the boring tool has detached a sufficient quantity of material, the boring rod and tool are drawn up by means of the rope o, fig. 158, winding upon the drum q, which is driven by straps and gearing from the steam-engine t. a shell is then lowered into the bore-hole by the wire-rope u, from the other drum v, and is afterwards drawn up again with the excavated material. a friction break is applied to the drum q, for regulating the rate of lowering the boring rod down the well. the shell shown in figs. 186, 187, consists of a riveted iron cylinder, with a handle at the top, which can either be screwed to the boring rod or attached to the wire-rope; and the bottom is closed by a large valve, opening inwards. two different forms of valve are used, either a pair of flap-valves, as shown in fig. 186, or a single-cone valve, fig. 187; and the bottom ring of the cylinder, forming the seating of the valve, is forged solid, and steeled on the lower edge. on lowering this cylinder to the bottom of the bore-hole, the valve opens, and the loose material enters the cylinder, where it is retained by the closing of the valve, whilst the shell is drawn up again to the surface. in boring through chalk, as in the case of the deep wells in the paris basin, the hole is first made of about half the final diameter for 60 to 90 feet depth, and it is then enlarged to the full diameter by using a larger tool. this is done for convenience of working; for if the whole area were acted upon at once, it would involve crushing all the flints in the chalk; but, by putting a shell in the advanced hole, the flints that are detached during the working of the second larger tool are received in the shell and removed by it, without getting broken by the tool. [illustration: shells. figs. 185-187.] the resistance experienced in boring through different strata is various; and some rocks passed through are so hard, that with 12,000 blows a day of a boring tool weighing nearly 10 cwt., with 19 inches height of fall, the bore-hole was advanced only 3 to 4 inches a day. as the opposite case, strata of running sand have been met with so wet, that a slight movement of the rod at the bottom of the hole was sufficient to make the sand rise 30 to 40 feet in the bore-hole. in these cases dru has adopted the chinese method of effecting a speedy clearance, by means of a shell closed by a large ball-clack at the bottom, as shown in fig. 186, and suspended by a rope, to which a vertical movement is given; each time the shell falls upon the sand a portion of this is forced up into the cylinder, and retained there by the ball-valve. borings of large diameter, for mines or other shafts, are also sunk by means of the same description of boring tools, only considerably increased in size, extending up to as much as 14 feet diameter. the well is then lined with cast-iron or wrought-iron tubing, for the purpose of making it water-tight; and a special contrivance, invented by kind, and alluded to at p. 110, has been adopted for making a water-tight joint between the tubing and the bottom of the well, or with another portion of tubing previously lowered down. this is done by a stuffing-box, shown in fig. 188, which contains a packing of moss at a a. the upper portion of the tubing is drawn down to the lower portion by the tightening screws b b, so as to compress the moss-packing when the weight is not sufficient for the purpose. a space c is left between the tubing and the side of the well, to admit of the passage of the stuffing-box flange, and also for running in concrete for the completion of the operation. the moss-packing rests upon the bottom flange d; but this flange is sometimes omitted. the joint is thus simply made by pressing out the moss-packing against the sides of the well; and this material, being easily compressible and not liable to decay under water, is found to make a very satisfactory and durable joint. [illustration: stuffing-box. fig. 188.] m. dru states that the reaction tool has been successfully employed for borings up to as large as about 4 feet diameter, witness the case of the well at butte-aux-cailles of 47 inches diameter; but beyond that size he considers the shock requisite to liberate the larger and heavier tool would probably be so excessive, as to be injurious to the boring rods and the rest of the attachments; and he therefore designed the arrangement of the disengaging rod for liberating the tool in borings of large diameter, whereby all shock upon the boring rods was avoided and the tool was liberated with complete certainty. in practice it is necessary, as with the common chisel, to turn the boring tool partly round between each stroke, so as to prevent it from falling every time in the same position at the bottom of the well; and this was effected in the well at butte-aux-cailles by manual power at the top of the well, by means of a long hand-lever fixed to the boring rod by a clip bolted on, which was turned round by a couple of men through part of a revolution during the time that the tool was being lifted. the turning was ordinarily done in the right-hand direction only, so as to avoid the risk of unscrewing any of the screwed couplings of the boring rods; and care was taken to give the boring rod half a turn when the tool was at the bottom, so as to tighten the screw-couplings, which otherwise might shake loose. in the event of a fracture, however, leaving a considerable length of boring rod in the hole, it was sometimes necessary to have the means of unscrewing the couplings of the portion left in the hole, so as to raise it in parts instead of all at once. in that case a locking clip was added at each screwed joint above, and secured by bolts, as shown at c in fig. 180, at the time of putting the rods together for lowering them down the well to recover the broken portion; and by this means the ends of the rods were prevented from becoming unscrewed in the coupling sockets, when the rods were turned round backwards for unscrewing the joints in the broken length at the bottom of the bore-hole. when running sands are met with, the plan adopted is to use the chinese ball-scoop, or shell, fig. 186, described for clearing the bottom of the bore-hole; and where there is too much sand for it to be got rid of in this way, a tube has to be sent down from the surface to shut off the sand. this, of course, necessitates diminishing the diameter of the hole in passing through the sand; but on reaching the solid rock below the running sand, an expanding tool is used for continuing the bore-hole below the tubing with the same diameter as above it, so as to allow the tubing to go down with the hole. in the case of meeting with a surface of very hard rock at a considerable inclination to the bore-hole, m. dru employs a tool, the cutters of which are fixed in a circle all round the edge of the tool, instead of in a single diameter line; the length of the tool is also considerably increased in such cases, as compared with the tools used for ordinary work, so that it is guided for a length of as much as 20 feet. he uses this tool in all cases where from any cause the hole is found to be going crooked, and has even succeeded by this means in straightening a hole that had previously been bored crooked. the cutting action of this tool is all round its edge; and therefore in meeting with an inclined hard surface, as there is nothing to cut on the lower side, the force of the blow is brought to bear on the upper side alone, until an entrance is effected into the hard rock in a true straight line with the upper part of the hole. although as regards diameter, depth, and flow of water in favourable localities, some extraordinary results have been obtained with this system of boring by rods worked by steam power, yet, as dru himself observes, "in some instances his own experience of boring had been, that owing to the difficulties attending the operation, the occurrence of delays from accidents was the rule, while the regular working of the machinery was the exception." a further disadvantage to be noticed is that, owing to the time and labour involved in raising and lowering heavy rods in borings of 10 inches diameter and upwards, there is a strong inducement to keep the boring tool at work for a much longer period than is actually necessary for breaking-up fresh material at each stroke. the fact is that after from 100 to 200 blows have been given, the boring tool merely falls into the accumulated _débris_ and pounds this into dust, without again touching the surface of the solid rock. it may therefore be easily understood how much time is totally lost out of the periods of five to eight hours during which with the rod system the tool is allowed to continue working. mather and platt's system. in the most recent method of boring adopted in england, the rope employed in the chinese system has been reverted to, in place of the iron or wood rods used on the continent. a flexible rope admits of being handled with greater facility than iron rods, but wants the advantage of rigidity: in the chinese method it admitted of withdrawing the chisel or bucket very rapidly, but gave no certainty to the operation of the chisel at the bottom of the hole. the rods on the other hand enable a very effective blow to be given, with a definite turning or screwing motion between the blows according to the requirements of the strata; but the time and trouble of raising heavy rods from great depths on each occasion of changing from boring to clearing out the hole form a serious drawback, which makes the stoppages occupy really a longer time than the actual working of the machinery. [illustration: elevation of mather and platt apparatus. fig. 189.] [illustration: small boring machine. _side elevation._] [illustration: small boring machine. _plan._ figs. 190, 191.] the method invented by colin mather, and manufactured by mather and platt, of oldham, employed largely in england for deep boring, seems to combine the advantages of the systems hitherto used, and to be free from many of their disadvantages. the distinctive features of this plan, which is shown in figs. 189 to 195, are the mode of giving the percussive action to the boring tool, and the construction of the tool or boring-head, and of the shell-pump for clearing out the hole after the action of the boring-head. instead of these implements being attached to rods, they are suspended by a flat hemp-rope, about 1/2 inch thick and 4-1/2 inches broad, such as is commonly used at collieries; and the boring tool and shell-pump are raised and lowered as quickly in the bore-hole as the bucket and cages in a colliery shaft. [illustration: large boring machine. _longitudinal section._ fig. 192.] the flat rope a a, fig. 189, from which the boring-head b is suspended, is wound upon a large drum c driven by a steam-engine d with a reversing motion, so that one man can regulate the operation with the greatest ease. all the working parts are fitted into a wood or iron framing e e, rendering the whole a compact and complete machine. on leaving the drum c the rope passes under a guide pulley f, and then over a large pulley g carried in a fork at the top of the piston-rod of a vertical single-acting steam cylinder. [illustration: _large boring machine._ _transverse section._ fig. 193.] this cylinder, by which the percussive action of the boring-head is produced, is shown to a larger scale in the vertical sections, figs. 192, 193; and in the larger size of machine here shown, the cylinder is fitted with a piston of 15 inches diameter, having a heavy cast-iron rod 7 inches square, which is made with a fork at the top carrying the flanged pulley g of about 3 feet diameter and of sufficient breadth for the flat rope a to pass over it. the boring-head having been lowered by the winding drum to the bottom of the bore-hole, the rope is fixed secure at that length by the clamp j; steam is then admitted underneath the piston in the cylinder h by the steam valve k, and the boring tool is lifted by the ascent of the piston-rod and pulley g; and on arriving at the top of the stroke the exhaust valve l is opened for the steam to escape, allowing the piston-rod and carrying pulley to fall freely with the boring tool, which falls with its full weight to the bottom of the bore-hole. the exhaust port is 6 inches above the bottom of the cylinder, while the steam port is situated at the bottom; and there is thus always an elastic cushion of steam retained in the cylinder of that thickness for the piston to fall upon, preventing the piston from striking the bottom of the cylinder. the steam and exhaust valves are worked with a self-acting motion by the tappets m m, which are actuated by the movement of the piston-rod; and a rapid succession of blows is thus given by the boring tool on the bottom of the bore-hole. as it is necessary that motion should be given to the piston before the valves can be acted upon, a small jet of steam n is allowed to be constantly blowing into the bottom of the cylinder; this causes the piston to move slowly at first, so as to take up the slack of the rope and allow it to receive the weight of the boring-head gradually and without a jerk. an arm attached to the piston-rod then comes in contact with a tappet which opens the steam valve k, and the piston rises quickly to the top of the stroke; another tappet worked by the same arm then shuts off the steam, and the exhaust valve l is opened by a corresponding arrangement on the opposite side of the piston-rod, as shown in fig. 193. by shifting these tappets the length of stroke of the piston can be varied from 1 to 8 feet in the large machine, according to the material to be bored through; and the height of fall of the boring-head at the bottom of the bore-hole is double the length of stroke of the piston. the fall of the boring-head and piston can also be regulated by a weighted valve on the exhaust pipe, checking the escape of the steam, so as to cause the descent to take place slowly or quickly, as may be desired. the boring-head b, fig. 189, is shown to a larger scale in figs. 194, 195, and consists of a wrought-iron bar about 4 inches diameter and 8 feet long, to the bottom of which a cast-iron cylindrical block c is secured. this block has numerous square holes through it, into which the chisels or cutters d d are inserted with taper shanks, as shown in fig. 195, so as to be very firm when working, but to be readily taken out for repairing and sharpening. two different arrangements of the cutters are shown in the elevation, fig. 194, and the plan, fig. 196. a little above the block c another cylindrical casting e is fixed upon the bar b, which acts simply as a guide to keep the bar perpendicular. higher still is fixed a second guide f, but on the circumference of this are secured cast-iron plates made with ribs of a saw-tooth or ratchet shape, catching only in one direction; these ribs are placed at an inclination like segments of a screw-thread of very long pitch, so that as the guide bears against the rough sides of the bore-hole when the bar is raised or lowered they assist in turning it, for causing the cutters to strike in a fresh place at each stroke. each alternate plate has the projecting ribs inclined in the opposite direction, so that one half of the ribs are acting to turn the bar round in rising, and the other half to turn it in the same direction in falling. these projecting spiral ribs simply assist in turning the bar, and immediately above the upper guide f is the arrangement by which the definite rotation is secured. to effect this object two cast-iron collars, g and h, are cottered fast to the top of the bar b, and placed about 12 inches apart; the upper face of the lower collar g is formed with deep ratchet-teeth of about 2 inches pitch, and the under face of the top collar h is formed with similar ratchet-teeth, set exactly in line with those on the lower collar. between these collars and sliding freely on the neck of the boring bar b is a deep bush j, which is also formed with corresponding ratchet-teeth on both its upper and lower faces; but the teeth on the upper face are set half a tooth in advance of those on the lower face, so that the perpendicular side of each tooth on the upper face of the bush is directly above the centre of the inclined side of a tooth on the lower face. to this bush is attached the wrought-iron bow k, by which the whole boring bar is suspended with a hook and shackle o, fig. 192, from the end of the flat rope a. the rotary motion of the bar is obtained as follows: when the boring tool falls and strikes the blow, the lifting bush j, which during the lifting has been engaged with the ratchet-teeth of the top collar h, falls upon those of the bottom collar g, and thereby receives a twist backwards through the space of half a tooth; and on commencing to lift again, the bush rising up against the ratchet-teeth of the top collar h receives a further twist backwards through half a tooth. the flat rope is thus twisted backwards to the extent of one tooth of the ratchet; and during the lifting of the tool it untwists itself again, thereby rotating the boring tool forwards through that extent of twist between each successive blow of the tool. the amount of the rotation may be varied by making the ratchet-teeth of coarser or finer pitch. the motion is entirely self-acting, and the rotary movement of the boring tool is ensured with mechanical accuracy. this simple and most effective action taking place at every blow of the tool produces a constant change in the position of the cutters, thus increasing their effect in breaking the rock. [illustration: _boring head._ _elevation._ fig. 194.] [illustration: _boring head._ _sectional elevation._ fig. 195.] [illustration: _plan at bottom, inverted._ fig. 196.] [illustration: shell pump. figs. 197, 198.] the shell-pump, for raising the material broken up by the boring-head, is shown in figs. 197, 198, and consists of a cylindrical shell or barrel p of cast-iron, about 8 feet long and a little smaller in diameter than the size of the bore-hole. at the bottom is a clack a opening upwards, somewhat similar to that in ordinary pumps; but its seating, instead of being fastened to the cylinder p, is in an annular frame c, which is held up against the bottom of the cylinder by a rod d passing up to a wrought-iron bridge e at the top, where it is secured by a cotter f. inside the cylinder works a bucket b, similar to that of a common lift-pump, having an indiarubber disc valve on the top side; and the rod d of the bottom clack passes freely through the bucket. the rod g of the bucket itself is formed like a long link in a chain, and by this link the pump is suspended from the shackle o, fig. 192, at the end of the flat rope, the bridge e, fig. 197, preventing the bucket from being drawn out of the cylinder. the bottom clack a is made with an indiarubber disc, which opens sufficiently to allow the water and smaller particles of stone to enter the cylinder; and in order to enable the pieces of broken rock to be brought up as large as possible, the entire clack is free to rise bodily about 6 inches from the annular frame c, as shown in fig. 197, thereby affording ample space for large pieces of rock to enter the cylinder, when drawn in by the up stroke of the bucket. the general working of the boring machine is as follows. the winding drum c, fig. 189, is 10 feet diameter in the large machine, and is capable of holding 3000 feet length of rope 4-1/2 inches broad and 1/2 inch thick. when the boring-head b is hooked on the shackle at the end of the rope a, its weight pulls round the drum and winding engine, and by means of a break it is lowered steadily to the bottom of the bore-hole; the rope is then secured at that length by screwing up tight the clamp j. the small steam jet n, figs. 192, 193, is next turned on, for starting the working of the percussion cylinder h; and the boring-head is then kept continuously at work until it has broken up a sufficient quantity of material at the bottom of the bore-hole. the clamp j which grips the rope is made with a slide and screw i, fig. 192, whereby more rope can be gradually given out as the boring-head penetrates deeper in the hole. in order to increase the lift of the boring-head, or to compensate for the elastic stretching of the rope, which is found to amount to 1 inch in each 100 feet length, it is simply necessary to raise the top pair of tappets on the tappet rods whilst the percussive motion is in operation. when the boring-head has been kept at work long enough, the steam is shut off from the percussion cylinder, the rope unclamped, the winding engine put in motion, and the boring-head wound up to the surface, where it is then slung from an overhead suspension bar q, fig. 189, by means of a hook mounted on a roller for running the boring-head away to one side, clear of the bore-hole. the shell-pump is next lowered down the bore-hole by the rope, and the _débris_ pumped into it by lowering and raising the bucket about three times at the bottom of the hole, which is readily effected by means of the reversing motion of the winding engine. the pump is then brought up to the surface, and emptied by the following very simple arrangement: it is slung by a traversing hook from the overhead suspension bar q, fig. 189, and is brought perpendicularly over a small table e in the waste tank t; and the table is raised by the screw s until it receives the weight of the pump. the cotter f, fig. 197, which holds up the clack seating c at the bottom of the pump, is then knocked out; and the table being lowered by the screw, the whole clack seating c descends with it, as shown in fig. 198, and the contents of the pump are washed out by the rush of water contained in the pump cylinder. the table is then raised again by the screw, replacing the clack seating in its proper position, in which it is secured by driving the cotter f into the slot at the top; and the pump is again ready to be lowered down the bore-hole as before. it is sometimes necessary for the pump to be emptied and lowered three or four times in order to remove all the material that has been broken up by the boring-head at one operation. the rapidity with which these operations may be carried on is found in the experience of the working of the machine to be as follows. the boring-head is lowered at the rate of 500 feet a minute. the percussive motion gives twenty-four blows a minute; this rate of working continued for about ten minutes in red sandstone and similar strata is sufficient for enabling the cutters to penetrate about 6 inches depth, when the boring-head is wound up again at the rate of 300 feet a minute. the shell-pump is lowered and raised at the same speeds, but only remains down about two minutes; and the emptying of the pump when drawn up occupies about two or three minutes. [illustration: accident tools. figs. 199-204.] in the construction of this machine it will be seen that the great desideratum of all earth boring has been well kept in view; namely, to bore-holes of large diameter to great depths with rapidity and safety. the object is to keep either the boring-head or the shell-pump constantly at work at the bottom of the bore-hole, where the actual work has to be done; to lose as little time as possible in raising, lowering, and changing the tools; to expedite all the operations at the surface; and to economize manual labour in every particular. with this machine, one man standing on a platform at the side of the percussion cylinder performs all the operations of raising and lowering by the winding engine, changing the boring-head and shell-pump, regulating the percussive action, and clamping or unclamping the rope: all the handles for the various steam valves are close to his hand, and the break for lowering is worked by his foot. two labourers attend to changing the cutters and clearing the pump. duplicate boring-heads and pumps are slung to the overhead suspension bar q, fig. 189, ready for use, thus avoiding all delay when any change is requisite. as is well known by those who have charge of such operations, in well boring innumerable accidents and stoppages occur from causes which cannot be prevented, with however much vigilance and skill the operations may be conducted. hard and soft strata intermingled, highly-inclined rocks, running sands, and fissures and dislocations are fruitful sources of annoyance and delay, and sometimes of complete failure; and it will therefore be interesting to notice a few of the ordinary difficulties arising out of these circumstances. in all the bore-holes yet executed by this system, the various special instruments used under any circumstances of accident or complicated strata are fully shown in figs. 199 to 207. [illustration: grapnel for stiff clay. fig. 207.] [illustration: straightening plug for tubes. fig. 205.] [illustration: grapnel for cores. fig. 206.] the boring-head while at work may suddenly be jammed fast, either by breaking into a fissure, or in consequence of broken rock falling upon it from loose strata above. all the strain possible is then put upon the rope, either by the percussion cylinder or by the winding engine; and if the rope is an old one or rotten it breaks, leaving perhaps a long length in the hole. the claw grapnel, shown in fig. 199, is then attached to the rope remaining on the winding drum, and is lowered until it rests upon the slack broken rope in the bore-hole. the grapnel is made with three claws a a centred in a cylindrical block b, which slides vertically within the casing c, the tail ends of the claws fitting into inclined slots d in the casing. during the lowering of the grapnel, the claws are kept open, in consequence of the trigger e being held up in the position shown in fig. 199, by the long link f, which suspends the grapnel from the top rope. but as soon as the grapnel rests upon the broken rope below, the suspending link f continuing to descend allows the trigger e to fall out of it; and then in hauling up again, the grapnel is lifted only by the bow g of the internal block b, and the entire weight of the external casing c bears upon the inclined tail ends of the claws a, causing them to close in tight upon the broken rope and lay hold of it securely. the claws are made either hooked at the extremity or serrated. the grapnel is then hauled up sufficiently to pull the broken rope tight, and wrought-iron rods 1 inch square with hooks attached at the bottom are let down to catch the bow of the boring-head, which is readily accomplished. two powerful screw-jacks are applied to the rods at the surface, by means of the step-ladder shown in fig. 201, in which the cross-pin h is inserted at any pair of the holes, so as to suit the height of the screw-jacks. if the boring-head does not yield quickly to these efforts, the attempt to recover it is abandoned, and it is got out of the way by being broken up into pieces. for this purpose the broken rope in the bore-hole has first to be removed, and it is therefore caught hold of with a sharp hook and pulled tight in the hole, while the cutting grapnel, shown in fig. 200, is slipped over it and lowered by the rods to the bottom. this tool is made with a pair of sharp cutting jaws or knives i i opening upwards, which in lowering pass down freely over the rope; but when the rods are pulled up with considerable force, the jaws nipping the rope between them cut it through, and it is thus removed altogether from the bore-hole. the solid wrought-iron breaking-up bar, fig. 203, which weighs about a ton, is then lowered, and by means of the percussion cylinder it is made to pound away at the boring-head, until the latter is either driven out of the way into one side of the bore-hole, or broken up into such fragments as that, partly by the shell-pump and partly by the grapnels, the whole obstacle is removed. the boring is then proceeded with again, the same as before the accident. the same mishap may occur with the shell-pump getting jammed fast in the bore-hole, as illustrated in fig. 208; and the same means of removing the obstacle are then adopted. experience has shown the danger of putting any greater strain upon the rope than the percussion cylinder can exert; and it is therefore usual to lower the grapnel rods at once, if the boring-head or pump gets fast, thus avoiding the risk of breaking the rope. [illustration: shell-pump jammed in the bore-hole. fig. 208.] the breaking of a cutter in the boring-head is not an uncommon occurrence. if, however, the bucket grapnel, or the small screw grapnel, fig. 202, be employed for its recovery, the hole is readily cleared without any important delay. the screw grapnel, fig. 202, is applied by means of the iron grappling rods, so that by turning the rods the screw works itself round the cutter or other similar article in the bore-hole, and securely holds it while the rods are drawn up again to the surface. the bucket grapnel, fig. 206, is also employed for raising clay, as well as for the purpose of bringing up cores out of the bore-hole, where these are not raised by the boring-head itself in the manner already described. the action of this grapnel is nearly similar to that of the claw grapnel, fig. 199; the three jaws a a, hinged to the bottom of the cylindrical casing c, and attached by connecting rods to the internal block b sliding within the casing c, are kept open during the lowering of the tool, the trigger e being held up in the position shown in fig. 206, by the long suspending link f. on reaching the bottom, the trigger is liberated by the further descent of the link f, which, in hauling up again, lifts only the bow g of the internal block b; so that the jaws a are made to close inwards upon the core, which is thus grasped firmly between them and brought up within the grapnel. where there is clay or similar material at the bottom of the bore-hole, the weight of the heavy block b in the grapnel causes the sharp edges of the pointed jaws to penetrate to some depth into the material, a quantity of which is thus enclosed within them and brought up. another grapnel that is also used where a bore-hole passes through a bed of very stiff clay is shown in fig. 207, and consists of a long cast-iron cylinder h fitted with a sheet-iron mouthpiece k at the bottom, in which are hinged three conical steel jaws j j opening upwards. the weight of the tool forces it down into the clay with the jaws open; and then on raising it the jaws, having a tendency to fall, cut into the clay and enclose a quantity of it inside the mouthpiece, which on being brought up to the surface is detached from the cylinder h and cleaned out. a second mouthpiece is put on and sent down for working in the bore-hole while the first is being emptied, the attachment of the mouthpiece to the cylinder being made by a common bayonet-joint l, so as to admit of readily connecting and disconnecting it. [illustration: tubing for bore-hole. fig. 209.] a running sand in soft clay is, however, the most serious difficulty met with in well boring. under such circumstances the bore-hole has to be tubed from top to bottom, which greatly increases the expense of the undertaking, not only by the cost of the tubes, but also by the time and labour expended in inserting them. when a permanent water supply is the main object of the boring, the additional expense of tubing the bore-hole is not of much consequence, as the tubed hole is more durable, and the surface water is thereby excluded; but in exploring for mineral it is a serious matter, as the final result of the bore-hole is then by no means certain. the mode of inserting tubes has become a question of great importance in connection with this system of boring, and much time and thought having been spent in perfecting the method now adopted, its value has been proved by the repeated success with which it has been carried out. the tubes used by mather and platt are of cast-iron, varying in thickness from 5/8 to 1 inch according to their diameter, and are all 9 feet in length. the successive lengths are connected together by means of wrought-iron covering hoops 9 inches long, made of the same outside diameter as the tube, so as to be flush with it. these hoops are from 1/4 to 3/8 inch thick, and the ends of each tube are reduced in diameter by turning down for 4-1/2 inches from the end, to fit inside the hoops, as shown in fig. 209. a hoop is shrunk fast on one end of each tube, leaving 4-1/2 inches of socket projecting to receive the end of the next tube to be connected. four or six rows of screws with countersunk heads, placed at equal distances round the hoop, are screwed through into the tubes to couple the two lengths securely together. thus a flush joint is obtained both inside and outside the tubes. the lowest tube is provided at the bottom with a steel shoe, having a sharp edge for penetrating the ground more readily. in small borings, from 6 to 12 inches diameter, the tubes are inserted into the bore-hole by means of screw-jacks, by the simple and inexpensive method shown in figs. 210, 211. the boring machine foundation a a, which is of timber, is weighted at b b by stones, pig iron, or any available material; and two screw-jacks c c, each of about 10 tons power, are secured with the screws downwards, underneath the beams d d crossing the shallow well e, which is always excavated at the top of the bore-hole. a tube f having been lowered into the mouth of the bore-hole by the winding engine, a pair of deep clamps g are screwed tightly round it, and the screw-jacks acting upon these clamps force the tube down into the ground. the boring is then resumed, and as it proceeds the jacks are occasionally worked, so as to force the tube if possible even ahead of the boring tool. the clamps are then slackened and shifted up the tubes, to suit the length of the screws of the jacks; two men work the jacks, and couple the lengths of tubes as they are successively added. the actual boring is carried on simultaneously within the tubes, and is not in the least impeded by their insertion, which simply involves the labour of an additional man or two. [illustration: tube-forcing apparatus with screw-jacks. fig. 210, 211.] a more perfect and powerful tube-forcing apparatus is adopted where tubes of from 18 to 24 inches diameter have to be inserted to a great depth, an illustration of which is afforded by an extensive piece of work at the horse fort, standing in the channel at gosport. this fort is a huge round tower, as shown in fig. 212; and to supply the garrison with fresh water, a bore-hole is sunk into the chalk. a cast-iron well a, consisting of cylinders 6 feet diameter and 5 feet long, has been sunk 90 feet into the bed of the channel in the centre of the fort, and from the bottom of this well an 18-inch bore-hole b is now in progress. the present depth is 400 feet, and the bore-hole is tubed the whole distance with cast-iron tubes 1 inch thick, coupled as before described. [illustration: _horse fort, spithead._ _section shewing bore-hole._ fig. 212.] [illustration: tube-forcing apparatus with hydraulic presses. fig. 213.] the method of inserting these tubes is shown in fig. 213. two wrought-iron columns c c, 6 inches diameter, are firmly secured in the position shown, by castings bolted to the flanges of the cylinders a a forming the well, so that the two columns are perfectly rigid and parallel to each other. a casting d, carrying on its under side two 5-inch hydraulic rams i i of 4 feet length, is formed so as to slide freely between the columns, which act as guides; the hole in the centre of this casting is large enough to pass a bore-tube freely through it, and by means of cotters passed through the slots in the columns the casting is securely fixed at any height. a second casting e, exactly the same shape as the top one, is placed upon the top of the tubes b b to be forced down, a loose wrought-iron hoop being first put upon the shoulder at the top of the tube, large enough to prevent the casting e from sliding down the outside of the tubes; this casting or crosshead rests unsecured on the top of the tube and is free to move with it. the hydraulic cylinders i, with their rams pushed home, are lowered upon the crosshead e, and the top casting d to which they are attached is then secured firmly to the columns c by cottering through the slots. a small pipe f, having a long telescope joint, connects the hydraulic cylinders i with the pumps at the surface which supply the hydraulic pressure. by this arrangement a force of 3 tons on the square inch, or about 120 tons total upon the two rams, has frequently been exerted to force down the tubes at the horse fort. after the rams have made their full stroke of about 3 feet 6 inches, the pressure is let off, and the hydraulic cylinders i with the top casting d slide down the rams resting on the crosshead e, until the rams are again pushed home. the top casting d is then fixed in its new position upon the columns c, by cottering fast as before, and the hydraulic pressure is again applied; and this is repeated until the length of two tubes, making 18 feet, has been forced down. the whole hydraulic apparatus is then drawn up again to the top, another 18 feet of tubing added, and the operation of forcing down resumed. the tubes are steadied by guides at g and h, fig. 213, shown also in the plans. the boring operations are carried on uninterruptedly during the process of tubing, excepting only for a few minutes when fresh tubes are being added. it will be seen that the cast-iron well is in this case the ultimate abutment against which the pressure is exerted in forcing the tubes down, instead of the weight of the boring machine with stones and pig iron added, as in the case where the screw-jacks are used; the hydraulic method was designed specially for the work at gosport, and has acted most perfectly. both the cast-iron well and the bore-hole are entirely shut off from all percolation of sea-water, by first filling up the well 30 feet with clay round the tubes, and making the tubes themselves water-tight at the joints at the time of putting them together. in the event of any accident occurring to the tubes while they are being forced down the bore-hole, such as requires them to be drawn up again out of the hole, the prong grapnel, fig. 204, is employed for the purpose, having three expanding hooked prongs, which slide down readily inside the tube, and spring open on reaching the bottom; the hooks then project underneath the edge of the tube, which is thus raised on hauling up the grapnel. in case the tubes get disjointed and become crooked during the process of tubing, the long straightening plug, fig. 205, consisting of a stout piece of timber faced with wrought-iron strips, is lowered down inside them; above this is a heavy cast-iron block, the weight of which forces the plug past the part where the tubes have got displaced, and thereby straightens them again. although there are few localities where the geological formation is not favourable to the yield of pure water if a boring be carried deep enough, yet it rarely happens that free-flowing wells such as those in paris and hull are the result. generally after the water-bearing strata have been pierced, the level to which the water will rise is at some depth below the surface of the ground; and only by the aid of pumps can the desired supply be brought to the surface. various pumping arrangements have therefore been adopted to suit the different conditions that are met with. it is not the object of the present work to treat of the forms and fittings of pumps, and the following details are only given as completing mather and platt's system. it is always desirable to sink a cast-iron well, such as that at the horse fort, as nearly as possible down to the level at which the water stands in the bore-hole. the sinking of such a well is rendered an easy and rapid operation, with the aid of the boring machine in winding out the material from the bottom, and keeping the sinkers dry by the use of the dip-bucket, shown in figs. 214 to 216, which will lift from 50 to 100 gallons of water a minute, for taking off the surface drainage. a well having thus been made down to the level of the water in the bore-hole, the permanent pumps are then applied to the bore-hole as follows, the size of the pumps varying according to the diameter of the bore-hole. taking the case of a 15-inch bore-hole, a pump barrel consisting of a plain cast-iron cylinder, say 12 inches diameter and 12 feet long, as shown in section in fig. 219, is attached at the bottom of cast-iron or copper pipes, which are 1/4 inch larger in diameter than the pump barrel, and are coupled together in lengths by flanges, fig. 217. by adding the requisite number of lengths of pipe at the top, the pump barrel is lowered to any desired depth down the bore-hole: the nearer to the depth of the water-bearing strata the better. the topmost length of pipe has a broad flange at its upper end, which rests upon a preparation made to receive it on the cast-iron bottom of the well, as at c in fig. 219. [illustration: dip bucket. figs. 214, 215.] [illustration: sectional plan. fig. 216.] [illustration: joint of copper tubes. fig. 217.] [illustration: couplings of pump rods. fig. 218.] a pump bucket d, fig. 219, with a water passage through it and a clack on the top side, is then lowered into the barrel, being suspended by a solid wrought-iron pump-rod e, which is made up of lengths of 30 feet coupled together by right-and-left-hand screw-couplings, as in fig. 218. a second bucket f of similar form is also lowered into the pump barrel, above the first bucket, and is suspended by hollow rods g coupled together in the manner just described; the inside diameter of the hollow rods g being such that the couplings of the solid rods e may pass freely through. the pump-rods are carried up the well a to the surface, where the hollow rod of the top bucket is attached to the horizontal arm of a bell-crank lever h, fig. 219; and the solid rod of the bottom bucket, passing up through the hollow rod of the top bucket, is suspended from the horizontal arm of a second reversed bell-crank lever k, facing the first lever h. as the extremities of the horizontal arms of the levers meet over the centre of the well, one of them is made with a forked end to admit of the other passing it. the vertical arms of the two levers are coupled by a connecting rod l, and a reciprocating motion is given to them by means of an oscillating steam cylinder m, the piston-rod of which is attached direct to the extremity of one of the vertical arms; a crank and flywheel n are also connected to the levers, for controlling the motion at the ends of the stroke. with the proportion shown in the figure of 3 to 4 between the horizontal and vertical arms of the bell-crank levers, the stroke of 5 feet 4 inches of the steam piston gives 4 feet stroke of the pump. the reciprocating motion of the reversed bell-crank levers causes the two buckets to move always in opposite directions, so that they meet and separate at each stroke of the engine. a continuous flow of water is the result, for when the top bucket is descending, the bottom bucket is rising and delivering its water through the top bucket; and when the top bucket rises, it lifts the water above it while the bottom bucket is descending, and water rises through the descending bottom bucket to fill the space left between the two buckets. in this way the effect of a double-acting pump is produced. [illustration: pumping engine and bore-hole. fig. 219.] although a continuous delivery of water is thus obtained of equal amount in each stroke, it is found in practice that a heavy shock is occasioned at each end of the stroke, in consequence of both the buckets starting and stopping simultaneously, causing the whole column of water to be stopped and put into motion again at each stroke. as an air-vessel for keeping up the motion of the water is inapplicable in such a situation, a modified arrangement of the two bell-crank levers has been adopted, which answers the purpose, causing each bucket at the commencement of its up stroke to take the lift off the other, before the up stroke of the latter is completed. by this means all shock is avoided, as the first bucket gently and gradually relieves the second, before the return stroke of the second commences. [illustration: pumping engine and double-acting pump with improved motion. fig. 220, 221.] in this improved pumping motion, which is shown in figs. 220, 221, the two bell-crank levers h and k, working the pump buckets, are centred one above the other, the upper one being inverted; the vertical arms are slotted, and are both actuated by the same crank-pin working in the slots, the revolution of the crank thus giving an oscillating movement to the two levers through the extent of the arcs shown by the dotted lines in fig. 220. the solid pump-rod e suspending the bottom bucket d is attached to the upper bell-crank lever k, and the hollow rod g of the top bucket is suspended from the lower lever h; the crank-shaft j working the levers is made to revolve in the direction shown by the arrow in fig. 220, by means of gearing driven by the horizontal steam-engine p. the result of this arrangement is, that in the revolution of the crank the dead point of one of the levers is passed before that of the other is reached; so that the bucket which first comes to rest at the end of its stroke is started into motion again before the second bucket comes to rest. thus in the lifting stroke of the bottom bucket worked by the upper lever k, the bucket in ascending has only reached the position shown at d in fig. 220, at the moment when the top bucket worked by the lower lever h arrives at the bottom extremity of its stroke, and the bottom bucket d, which is still rising, continues to lift until it reaches its highest position, by which time the top bucket has got well into motion in its up stroke, and is in its turn lifting the water. chapter vii. examples of wells executed, and of districts supplied by wells. permian strata. _durham._--large quantities of water are pumped from the lower permian sandstone beneath the magnesian limestone of this county, and are used for the supply of the towns of sunderland, south shields, jarrow, and many villages. the quantity, calculated by daglish and foster to reach five millions of gallons a day, is obtained from an area of fifty square miles overlying the coal measures. the water-level has not been lowered in the rock by these operations. along the coast it is that of mean tide, and inland rises to a level of 180 feet. in the coal measures below there is little water, and that little is saline. sedgwick gives the strata as red gypseous marls, 100 feet; thin bedded grey limestone, 80 feet; red gypseous marls, slightly salt, 200 feet; magnesian limestone, 500 feet; marl slate, 60 feet; lower red sandstone, 200 feet. _coventry._--warwickshire. the town is supplied with 750,000 gallons of water a day from two bore-holes made in the bottom of the reservoir. the bore-holes are respectively 6 inches and 8 inches diameter, and 200 feet and 300 feet deep. the town is situated on the permian formation, but latham states that the supply is procured from the red sandstone, and, from observations made, it has been found that the two bore-holes yield water at the rate of 700 gallons a minute. trias strata. _birkenhead._--there are here several deep wells belonging to the tranmere local board, the birkenhead commissioners, and the wirral water company, yielding together about 4,000,000 gallons a day. figs. 222, 223, show a section and plan of the no. 2 or new engine well at the birkenhead waterworks. the shaft is 7 feet diameter for 105 feet, with a bore-hole 26 inches for 35 feet, 18 inches for 16 feet, 12 inches for 99 feet, and 7 inches for 150 feet, or a total depth from surface of 405 feet. the water-level is about 95 feet from surface when the engine is not at work. at the upper water-level, shown in the 26-inch hole, the yield was at the rate of 1,807,400 gallons in twenty-four hours, at the lower level at the rate of 2,000,000 gallons in the same time. at the water-level indicated in the 7-inch bore, water was met with in large quantities. the old engine well is almost identical. [illustration: new engine well, birkenhead waterworks. fig. 222.] [illustration: plan. fig. 223.] [illustration: fig. 224. well at aspinall's brewery, birkenhead.] [illustration: fig. 225. plan] [illustration: enlarged parts. _at_ a. a. _at_ b. b. _at_ c. c. _at_ d. d. _at_ e. e. fig. 226.] figs. 224, 225, are a section and plan, and fig. 226 enlarged parts of the well at aspinall's brewery, birkenhead. it consists of a shallow shaft 5 feet in diameter and steined, continued by means of iron cylinders 3 feet 3 inches in diameter and 50 feet in depth. when sand with much water of poor quality was met with, a series of lining tubes was introduced from the point a a, the space between these and the cylinders being filled with concrete. the tubes were discontinued at the sandstone, and the lowest portion of the hole, 3 inches in diameter, is unlined. the water overflows. figs. 227, 228, are a section and plan of the well at cook's brewery, birkenhead. the shaft is 6 feet diameter, lined with 9-inch steining, and is 66 feet deep. at 29 feet from surface it is enlarged for the purpose of affording increased storage room for the water. there is a 16-inch pipe at bottom of shaft 49 feet deep, continued by a 12-inch bore-hole 13 feet into the red sandstone. the water-level is 27 feet from the surface of the ground. _birmingham._--out of the 7,000,000 gallons a day supplied to the town in 1865 by the waterworks company, 2,000,000 were derived from wells in the new red sandstone. in that year an act was passed authorizing the sinking of several new wells, whereby the quantity may be greatly increased. _burton-on-trent._--fig. 229 is a section of the well at the london and colonial brewery. extraordinary precautions were taken in constructing this well to obtain the water from the lower strata perfectly free from admixture with that from above. there is a steined shaft within which is an iron cylinder, and this again is lined with brick steining backed with concrete. the bore-hole, 182 feet deep and 4 inches diameter, is lined throughout with copper tubes. at the top the bore-hole is surrounded with a short tube upon which a thread is cut, so that, if necessary, a pipe may be screwed on and up to surface. the water rises to within 6 feet 3 inches of the level of the ground. fig. 230 is an enlarged section of the arrangements at the top of the bore-hole, and fig. 231 an enlarged section of the pipe joints. _crewe._--cheshire. a very plentiful supply of water for the supply of the town and works of crewe is obtained from a well sunk in the new red sandstone. the water is said to be very pure, and from the analysis of dr. zeidler it appears that there are only 6·10 grains of solid matter to the gallon. _leamington._--the well in this town is situated at the foot of newbold hill, and is 5 feet in diameter and sunk to a depth of 50 feet. at the bottom of the well a bore-hole, part of the way 18 inches and the remainder 12 inches in diameter, is carried down 200 feet. it passes through alternating beds of marl and sandstone, and the surface water met with has been bricked or puddled out. the yield is about 320,000 gallons in twenty-four hours. previously to this well being made, a trial boring, of which figs. 232, 233, are sections, was made. this boring was lined with iron tubes 9 inches in diameter for 17 feet, inside this 8 inches in diameter for 22 feet 9 inches, and within this again a 5-inch tube. it was continued by a 5-inch bore reduced to 4-1/2 inches, and at bottom to 3 inches. [illustration: well at cook's brewery, birkenhead. fig. 227.] [illustration: plan a.b. fig. 228.] [illustration: well at london and colonial brewery, burton-on-trent. fig. 229.] [illustration: _top of bore-hole_ fig. 230.] [illustration: _enlarged section of pipe joints_ fig. 231.] _liverpool._--the oldest wells are at bootle, to the north of the town; these consisted in the first instance of three lodges or excavations in the rock, covering about 10,000 feet super and about 26-1/2 feet deep. these were covered with timber or slate roofs, and in them 16 bore-holes were sunk, of various diameters and at depths ranging from 13 feet to 600 feet. in 1850 the yield of one of these bore-holes was 921,192 gallons in twenty-four hours, and the total yield in the same time only 1,102,065. the water was collected in the lodges and conveyed by a tunnel 255 feet to a well 8 feet in diameter and 50 feet deep, from which it was pumped. the yield of the bootle well in 1865 was 643,678 gallons a day. since this time a new well of oval form, 12 feet by 9 feet and 108 feet deep, has been sunk, and at its completion the yield rose to 1,575,000 gallons a day, but it has again diminished considerably. the green lane wells were commenced in 1845, the surface being 144 feet above the sea-level and their depth 185 feet, or 41 feet below the sea-level. headings extend in all about 300 feet from the shafts in various directions, three separate shafts being carried up to the surface. at first the yield was 1,250,000 gallons a day. a bore-hole, 6 inches in diameter, was then driven to a depth of 60 feet from the bottom of the well, when the yield increased to 2,317,000 gallons. in june, 1856, the bore-hole was widened to 9 inches and carried down 101 feet farther, when the yield amounted to its present supply of over 3,000,000 gallons a day. the large quantity of water yielded by the green lane well is probably due to the existence of a large fault which is considered to pass in a north-westerly direction by the well. in 1869 a bore-hole, 24 inches in diameter at the top and diminishing to 18 inches in diameter, was sunk from the bottom of a new shaft, 174 feet deep, to a depth of 310 feet, and the additional quantity of water derived from the new hole was about 800,000 gallons a day. the windsor station well is of oval form, 12 feet by 10 feet and 210 feet deep, with a length of headings of 594 feet, and a bore-hole 4 inches in diameter and 245 feet deep. the yield is 980,000 gallons a day. the dudlow lane well is also oval, 12 feet by 9 feet, and is sunk to a depth of 247 feet from the surface of the ground. headings have been driven from the bottom of the well for a total distance of 213 feet, and an 18-inch bore-hole has been sunk to a depth of 196 feet from the bottom of the well, which is chiefly in a close hard rock, with occasional white beds from which the water is mainly obtained. the yield is nearly 1,500,000 gallons a day. [illustration: trial boring for well at leamington. figs. 232, 233.] the total weekly supply from wells in liverpool is upwards of 41,000,000 gallons, and there are also a great number of private wells drawing water from the sandstone, and their supply may be roughly estimated at 30,000,000 gallons a week. [illustration: plan of wells at longton. fig. 234.] _longton_, staffordshire.--the potteries obtain a portion of their supply from a series of wells at longton, which are shown in the diagrammatic sectional plan, fig. 234. the well marked no. 1 is 12 feet in diameter, and 135 feet deep in the new red sandstone. when finished the water rose to within 35 feet from the surface. the cost of the first 45 feet was 3_l._ 10_s._ a yard; of the second 45 feet, 6_l._ 10_s._ a yard; and the third 45 feet, 9_l._ a yard. when this well was 36 feet down, a large quantity of water was met with, so a heading was driven at that depth in the direction of no. 2 well; this, after 30 feet, passed through a fault which drained off the water, and the sinking of no. 1 was proceeded with. after the engine had been erected and pumping some short time, it was proposed to drive headings from the bottom; but owing to the pumps taking up so much room in the shaft, there was not space enough for sinking operations to be carried on, and no. 2 well was therefore sunk for convenience sake, at the cost of about 30_s._ a yard. when no. 2 was down 54 feet, a trial bore-hole 3 inches diameter was put down, and water rose in a jet about 3 feet high. the well was then continued to the level of no. 1, and a heading, 39 feet long, driven between the two shafts. no. 2 has now a 12-inch bore-hole at bottom, down 54 feet. [illustration: well at bolckow and vaughan's, middlesborough. fig. 235.] [illustration: plan at a a. fig. 237.] [illustration: plan at b b. fig. 238.] [illustration: well at bolckow and vaughan's, middlesborough fig. 236.] headings have also been driven w. and n. of no. 2 well, at a cost of 30_s._ a yard. the western heading is 213 feet long, driven with a slight rise, and gave much water. there are two headings n., running in the direction of the railway, one over the other. the lower was driven level with the bottom of the shaft, but no water met with; the upper is 36 feet from the surface, and is intended to carry away surplus water down to a line of earthenware pipes which are led along the railway to a low-level reservoir. in the eastern heading there is a rise of 4 feet, owing to the nature of the strata; and after it had been driven 510 feet, well no. 3 was sunk for ventilation and for drawing out material. a bed of very hard sandstone, 63 feet long, was passed, cost 4_l._ 10_s._ a yard, and beyond came marl, in which driving cost 45_s._ a yard. this heading was continued 330 feet beyond no. 3, and an air-hole 3 inches diameter put down 126 yards deep, but no water was met with. the bed of hard sandstone was also found in driving the lower n. heading, which was discontinued after going into it some 5 or 6 feet. the yield from these wells is about 600,000 gallons a day, and recently a new bore-hole at no. 3 well, when down 350 feet, gave some 380,000 gallons a day additional. _leek._--the potteries waterworks have also wells at the wallgrange springs, near leek; these rise from the conglomerate beds, and are stated to yield 3,000,000 gallons daily. the water from these springs is pumped into ladderidge reservoir, and is distributed from thence into the town of newcastle-under-lyme and the potteries. [illustration: well at ross, herefordshire. fig. 239.] [illustration: plan. fig. 240.] _middlesborough._--the figs. 235 to 238 are sections and plans of a well at the works of messrs. bolckow and vaughan, middlesborough, made under the direction of s. c. homersham, c.e. a trial hole was first put down to a depth of 398 feet 6 inches, and a shaft afterwards sunk by messrs. docwra and son to that depth, through alternating beds of clay, sand, gypsum, and sandstone. at the bottom of the shaft a bore-hole of 18 inches diameter throughout was made with mather and platt's apparatus to a depth of 1312 feet; the first 1160 feet of which were through new red sandstone interspersed with beds of clay, white sandstone, red marl, and gypsum. next came 40 feet of gypsum, hard white sandstone, and limestone; and the remaining 100 feet were through red sandstone, pure salt rock, occasional layers of limestone, and then salt rock to the bottom. the gross time spent in sinking this bore-hole was 510 days, or an average of 2 feet 5 inches a day. _ross_, herefordshire.--the well at the alton court brewery is shown in figs. 239, 240. the shaft, 5 feet in diameter and 27 feet deep, is steined with 9-inch brickwork for a distance of 17 feet. at the bottom is a 12-inch bore-hole 100 feet 9 inches deep, unlined. the water is abundant. at level of the bore a heading, 6 feet high, 5 feet wide, and 27 long, has been driven, to afford storage room. _wolverhampton._--this town is partially supplied from wells sunk in the new red sandstone. there are two shafts, 7 feet in diameter and 300 feet deep, a heading 459 feet long, and in this a boring of 390 feet. the yield when first completed was 211,000 gallons a day. [illustration: well at swanage, dorset. fig. 241.] [illustration: plan. fig. 242.] _st. helens_, lancashire.--supplied with about 570,000 gallons daily from two wells, each 210 feet deep, in the new red sandstone. each well has a bore-hole at the bottom. oolitic strata. _northampton._--the well at the waterworks is sunk and bored 253 feet 3 inches in the lias. the shaft is steined with brickwork and iron cylinders in the following order: for 16 feet 9 inches in depth the well is 7 feet 6 inches in diameter, lined with brickwork; at this depth two cast-iron cylinders 5 feet 6 inches diameter are introduced, which are again succeeded by 9-inch brickwork, commencing at 5 feet 6 inches internal diameter and widening out to 7 feet 6 inches in diameter. the bottom of the shaft is floored with bricks at a distance of 120 feet from surface. at this point the bore-hole commences, and for the first 31 feet it is lined with 14-inch pipes, which rise into the shaft 5 feet above the floor. the remaining portion of the bore-hole, 102 feet, is 9 inches diameter. _swanage_, dorset.--the section and plan, figs. 241, 242, are of a well at swanage, sunk 60 feet and bored 53 feet, the lining tube rising 8 feet into the shaft, which is 5 feet 6 inches in diameter, and lined with 9-inch steining. the strata passed through are clays and limestones, and may perhaps be referred to the purbeck beds. at first this well yielded little or no water, but it now gives a sufficient supply. cretaceous strata. _bishop stortford._--the waterworks and well are situate west of the town, near the farm buildings known as marsh barns. the shaft is 160 feet deep, the bore-hole 140 feet. the following is a section of the strata;- feet. boulder clay 17 london clay, 54 feet;- brown clay 14 black clay 2 black sandy loam, with iron pyrites 12 black clay, with lignite 11 dark grey sand, with large pieces of sandstone and shells 15 reading beds, 45-1/2 feet;- black clay 2 brown clay 20 light brown sand 0-1/2 variegated sand 18 brown clay 4 flints and pebbles 1 ------ to chalk 116-1/2 chalk 183-1/2 ------ total 300 ------the water rises to within 140 feet of the surface of the ground. the yield is 10,000 gallons a minute; only 25 gallons a minute from the bore; the rest from the headings driven north and south respectively at a depth of 154 feet. _braintree._--the well sunk for the local board is in a field near pod's brook. the shaft is 8 feet in diameter, steined with 9-inch steining, and carried down 55 feet, the remainder of the well being bored. strata;- drift, 14 feet;- feet. sandy gravel 5 drift clay 9 london clay, 136 feet;- clay, with sand, shells, and septaria, the bottom part more sandy 126 dark sand, with a few shells, yielding much water 10 reading beds, 45 feet;- mottled plastic clays, getting more sandy lower down, and with specks of chalk 44 coarse black sandy clay 1 thanet sand (?), 33 feet;- light-coloured sands, firm and hard, getting darker and more friable lower down 20 light-coloured sands, firm, changing to coarse and dark 13 to chalk 228 chalk, with much water, rising to about 12 feet from the surface 17 --- total 245 ---the level of the ground is 140 feet above the sea-level; water stands 29 feet deep; yield about 11,500 gallons an hour. _brighton._--this town has always been supplied from wells sunk in the chalk. one well is sunk near the lewes road, and has a total length of 2400 feet of headings driven in a direction parallel with the sea, and at about the coast-level of low water. these headings intercept many fissures and materially add to the yield. a second well was sunk in 1865, at goldstone bottom, and headings driven to the extent of about a quarter of a mile across the valley parallel to the sea. goldstone bottom is a naturally formed basin in the chalk, the lowest side of which, nearest the sea, is more than 60 feet higher than the middle or bottom of the basin. the water is obtained as at lewes road, from fissures running generally at right-angles to the coast-line, but they are of much larger size and at far greater distances from each other; whereas at the lewes road well it is rare that 30 feet of headings were driven without finding a fissure, and the yield of the largest was not more than 100 to 150 gallons a minute. at goldstone nearly 160 feet were traversed without any result, and then an enormous fissure was pierced which yielded at once nearly 1000 gallons a minute; and the same interval was found between this and the next fissure, which was of a capacity nearly as large. the total length of the headings at goldstone bottom is 13,000 feet. the yield from each well is about 3,000,000 gallons daily. _chelmsford._--the well belonging to the local board of health, situated at moulsham, yields about 95,000 gallons of water a day. it is sunk for 200 feet; the rest bored. water overflowed at first, but now that the well is in use and pumped from, the water only rises to 76 feet from the surface. the following strata were pierced;- feet. in. black soil (mould) 3 0 drift, 63-1/2 feet;- yellow clay 2 6 gravel 12 6 quicksand 44 6 sand, with stones 4 0 london clay, 186-1/2 feet;- clay 104 0 clay, with sand 50 0 dark sand 12 6 clay slate (? septaria) 0 9 clay and shells 4 0 clay slate (? septaria) 0 3 dark sand and clay 9 6 sand and shells 4 0 pebbles 1 6 woolwich beds;- sand 7 0 red clay 12 0 clay and sand 64 0 dark thanet sand 30 0 ------ to chalk 366 0 chalk, 202 feet;- chalk 88 0 rubble 1 0 chalk 113 0 ------ total 568 0 ------_cheshunt, new river company._--situate at the engine-house between the two reservoirs. the well is 171 feet deep, and is steined partly with brickwork and partly with iron cylinders. for 12 feet in depth the well is 11 feet 6 inches in diameter, and steined with 14-inch brickwork; for a farther depth of 44 feet it is 9 feet diameter, and steined with 9-inch brickwork; of the 44 feet, 41 feet are lined with cast-iron cylinders, 8 feet diameter, which are also carried to a depth of 105 feet from the surface. there are fifteen cylinders of this size in use, and they are succeeded by others 6 feet 10 inches diameter, of which there are six in use; these are again succeeded by two cylinders 6 feet diameter. the whole of the cylinders are 6 feet in depth. the bottom of the last cylinder is 118 feet from the surface, at which point they rest upon a foundation of 9-inch brick steining 7 feet in depth. at the bottom of the 6-feet cylinders the well widens out in the form of a cone 12 feet 6 inches diameter at the floor, which is 26 feet below the bottom of the 6-feet cylinder. in the centre of the well a bore-hole, 3 inches diameter and 27 feet deep, was made, and the well is provided on the floor-level with headings. section of strata. feet. in. surface earth 1 6 gravel 8 0 london clay, 47 feet;- blue clay 45 0 yellow clay 2 0 reading beds, 51 feet;- white sand 12 0 dark sand 39 0 ------- to chalk 107 6 chalk 63 6 ------- total 171 0 -------_dorking_, surrey, obtains its water supply from a well sunk into the outcrop of the lower greensand, at the south side of the town. the shaft is 11 feet in diameter and 160 feet deep, steined with 9-inch work laid dry. the yield is not more than 30 gallons a minute, owing to the unfortunate position of the well, but might be considerably increased if suitable means were adopted. _harrow waterworks._--the well is situate 430 yards to the west of the church. the surface of the ground is 226 feet above the ordnance datum. there is a shaft for 193-1/2 feet; the rest is a bore. in a bed of dark red sand 144 feet down, the water was very foul. strata;- feet. in. light blue clay, with light-coloured stone 19 11 brown clay, with white stone 54 11 dark mottled clay 15 0 similar clay, with dark and green sand 4 0 the same, very hard 3 0 the same, very hard, and dark sand 2 0 lighter-coloured hard clay 5 0 the same, and dark sand 6 0 large pebbles 0 6 clay and sand 5 0 light blue clay 0 4 light-coloured stone, with red and blue spots 1 3 mottled clays 7 11 yellow, light blue, and green clay 1 0 dark green clay, with black veins and spots 5 0 blue clay 1 6 very hard brown, yellow, and blue clay 4 0 light brown running sand, with water 2 6 hard mottled clays 6 6 light brown dead sand 8 8 black peat, with dark pebbles 0 6 brown and green gravel, with flints 3 2 green clay 0 4 ------- to chalk 158 6 chalk, with beds of flint 4 to 15 inches in thickness, 15 to 24 inches apart; 395-1/2 feet down, from surface, a bed of flint 6 feet thick 254 0 ------- total 412 6 -------water rises to a height of 125 feet below the surface. the yield is about 190 gallons a minute. [illustration: well at highbury. fig. 243.] [illustration: plan. fig. 244.] [illustration: pipes enlarged. fig. 245.] _highbury_, middlesex.--well at the residence of h. rydon, esq., new park. figs. 243 to 245. the shaft is 4 feet 6 inches diameter, and 136 feet deep, steined with 9-inch work set in cement. the bore was commenced with a 12-inch hole, but the character of the ground was such that the successive reductions in size, shown in the enlarged section of the lining tubes, fig. 245, had to be made. when in the chalk the bore was continued some 48 feet unlined. the strata passed were;- gravel 3 feet. london clay, 111 feet;- blue clay 110 " claystone 1 " reading and thanet sand, 85 feet;- mottled clay 25 " coloured sand 60 " --- to chalk 199 " chalk 50 " --- total 249 " ---_kentish town._--this well was sunk under the supposition that as the outcrop of the subcretaceous formations was continuous around the margin of the cretaceous basin surrounding and underlying the london tertiaries, except at the eastern border, those subcretaceous formations would be found under london, just as they actually were at paris. this proved to be the case until the gault was passed, when a series of sandstones and clays was encountered, occupying the place of the lower greensand, but evidently of older geological character, and having many of the features of the new red sandstone. [illustration: boring at kentish town, london. figs. 246. 247.] the surface of the ground, fig. 246, is 174 feet above thames high-water mark. there is a shaft for 539 feet; the remainder being bored. the following detailed account of the strata is due to prestwich. [illustration: boring at kentish town, london--_continued_. figs. 248, 249.] london clay, 236 feet;- feet. in. yellow clay 30 6 blue clay, with septaria 205 6 reading beds, 61-1/2 feet:- red, yellow, and blue mottled clay 37 6 white sand, with flint pebbles 0 6 black sand, passing into the bed below 2 0 mottled green and red clay 1 0 clayey sand 3 0 dark grey sand, with layers of clay 9 6 ash-coloured quicksand 6 6 flint pebbles 1 6 thanet sand, 27 feet;- ash-coloured sand 10 0 clayey sand 4 0 dark grey clayey sand 11 0 angular green-coated flints 2 0 chalk, with flints (? upper chalk), 244-1/2 feet;- chalk, with flints 119 6 hard chalk, without flints 8 0 chalk, softer, with a few flints 31 6 nodular chalk, with three beds of tabular flints 13 6 chalk, with layers of flint 32 6 chalk, with a few flints and patches of sand 9 6 very light-grey chalk, with a few flints 30 0 chalk, without flints (lower chalk), 341 feet;- light grey chalk, and a few thin beds of marl 133 0 grey chalk marl, with compact and marly beds and occasional pyrites 161 0 grey marl 20 0 harder grey marl, rather sandy and with occasional pyrites 27 0 chalk marl, 59-1/4 feet;- hard rocky marl (? tottenhoe stone) 0 6 bluish grey marl, rather sandy, lower part more clayey 58 9 upper greensand;- dark green sand, mixed with grey clay 13 9 gault, 130-1/2 feet;- bluish grey micaceous clay, slightly sandy 39 0 the same, with two layers of clayey greensand 6 7 micaceous blue clay; at base a layer full of phosphatic nodules 84 11 lower greensand (?), 188-1/2 feet;- red and yellow clayey sand and sandstone 1 0 compact red clay, with patches of variegated sandstone 4 0 dark red clay 4 7 red clay, whitish sand, and mottled sandstone 3 0 hard red conglomerate, with pebbles from the size of a marble to that of a cannon-ball 2 0 micaceous red clay, mottled in places 26 0 layers of white sandstone and red sand 3 8 mottled sandstone 0 4 red sand and sandstone, with pebbles (a spring) 2 0 layers of red sandstone and white sand 4 0 pebbly red sand and sandstone 1 0 white and red sandstone 5 0 fine light red sand 2 9 hard sandstone 0 3 very fine light red sand 4 0 red clay 2 0 clayey sand 1 3 red sandy micaceous clay, with sandstone 2 5 compact hard greenish sandstone 10 0 very micaceous red clay 1 0 grey and red clayey sand 1 1 light-coloured soft sandstone 2 1 red sand and sandstone 6 2 greenish sandstone 4 0 white and grey clayey sand, with iron pyrites 2 0 reddish clayey sand, with layers of sandstone 3 8 micaceous red clay 18 4 greenish sandstone 0 5 red mottled micaceous clay, with patches of sand 34 6 red quartzose micaceous sandstone 2 0 brownish-red clayey sand and sandstone 4 0 very hard micaceous sandstone, with pebbles of white quartz 4 0 light red clayey sand 10 0 red micaceous quartzose sandstone 8 0 light red clayey sand, small fragments of chalk 2 0 whitish and greenish hard micaceous sandstone 6 0 ------- total 1302 0 -------the engravings, figs. 246 to 249, which are on the authority of g. r. burnell, do not exactly agree with prestwich's section, but in the main they are both alike. the following summary may be found of service;- feet. in. london clay 236 0 lower london tertiaries 88 6 chalk 644 9 upper greensand 13 9 gault 130 6 lower greensand (?) 188 6 [illustration: well at michelmersh. fig. 250.] _michelmersh_, hants.--fig. 250 shows a section of a well in this village, comprised within the writer's practice. the shaft is 4 ft. 6 in. in diameter and 400 feet deep, steined both above and below the chalk with 9-inch work, the upper course having rings of cement at every 12 inches. the strata pierced were;- feet. in. surface soil 4 0 dark clay 27 0 chalk 250 0 band of calcareous sand 2 6 upper greensand 17 0 ------ total 300 6 ------the water rises some 19 feet in the shaft, and is abundant, although up to the present its quantity has not been tested. _mile end_, middlesex.--well at charrington, head, and co.'s brewery. figs. 251 to 253. the surface is 33-1/2 feet above trinity high-water mark. in the upper part there are three iron cylinders built upon 9-inch brickwork, which is carried down into the mottled clay. a 9-inch iron cylinder, partially supported by rods from the surface, rises some 28 feet into the brick shaft into which it is built by means of rings. another iron cylinder is carried down into the chalk, the space between the cylinders being filled in with concrete. the strata passed were;- feet. in. made earth 7 0 valley drift, 6 feet;- sand 3 0 gravel 3 0 london clay, 86 feet;- blue clay 7 0 hard brown clay, with claystones 68 0 brown sandy clay 2 0 hard brown sandy clay, rotten at bottom 9 0 woolwich and reading beds 63 0 thanet sand, 40 feet;- green sand 2 0 brownish-green quicksand and pebbles 2 0 brown sand 2 0 grey and brownish-green sand 2 0 green sand and pebbles 2 0 brown sand 2 0 green sand and pebbles 15 0 grey sand and small pebbles 2 0 dark grey and green sand 10 6 green sand and green-coated flints 0 6 ------ to chalk 202 0 chalk flints 0 6 hard chalk and water 2 0 ------ total 204 6 ------the water-level is some 103 feet from surface, and the yield 60,000 to 70,000 gallons a day. [illustration: well at charrington's, mile end. figs. 251-253.] _norwich_.--well at coleman's works. after a few feet of alluvium the borer passed through hard chalk with flints at distances of about 6 or 7 feet apart, for 700 feet, with the exception of 10 feet at the depth of 500 feet where the rock was soft and of a rusty colour, thence the flints were thicker, namely, about 4 feet apart to the depth of 1050 feet. after this 102 feet were pierced of chalk, free from flints, to the upper greensand, a stratum of about 6 feet, and then gault for 36 feet. the whole boring being full of water to within 16 feet of the surface. section of strata;- feet. alluvium 12 hard chalk, with flints 483 soft chalk 10 hard chalk 190 hard chalk, flints closer 350 chalk without flints 102 upper greensand 6 gault 36 --- total 1189 ---[illustration: geological section from niort to verdun, through the paris basin. horizontal scale, 90 miles the inch. vertical scale, 1500 feet the inch. fig 254.] _paris_.--the wells sunk in the paris basin, of which fig. 254 is a section, are very numerous, and many of them of great depth. fig. 255 is a plan indicating the position of the principal wells, and figs. 256 to 258 sections giving each a summary of the nature and thickness of the formations passed through. for boring these wells special tools had to be used, which have already been described at length in chap. vi. a large artesian well was, in 1867, being constructed by dru at butte-aux-cailles, fig. 255, for the supply of the city of paris, which is intended to be carried down through the greensand to a depth of 2600 or 2900 feet to reach the portland limestone. the boring in 1867 was 490 feet deep, and its diameter 47 inches. during the previous 2-1/2 years, m. dru was engaged in sinking a similar well of 19 inches diameter for supplying the sugar refinery of m. say, in paris, fig. 255; 1570 feet deep of this well had been bored in 1867, see fig. 258. the well at grenelle was sunk by mulot in 1832, and after more than eight years' incessant labour, water rose on the 26th of february, 1842, from the total depth of 1806 feet 9 inches. the diameter of the bore-hole is 8 inches, ending, as is seen in the detail sections, figs. 259 to 262, in the lower greensand. the well of passy was intended to be executed in the paris basin which it was to traverse with a diameter, hitherto unattempted, of 1 mètre (3·2809 feet); that of the grenelle well being only 20 centimètres (8 inches). it was calculated that it would reach the water-bearing stratum at nearly the same depth as the latter, and would yield 8000 mètres or 10,000 cubic mètres in twenty-four hours, or about 1,786,240 gallons to 2,232,800 gallons a day. figs. 263 to 266 show a detail section of the strata passed. [illustration: fig. 255. reference.--p. passy. g. grenelle. b. butte-aux-cailles. r. sugar refinery.] [illustration: passy. fig. 256.] [illustration: grenelle. fig. 257.] [illustration: sugar refinery. fig. 258.] the operations were undertaken by kind under a contract with the municipality of paris, by which he bound himself to complete the works within the space of twelve months from the date of their commencement, and to deliver the above quantity of water for the sum of 300,000 francs, 12,000_l_. on the 31st of may, 1857--after the workmen had been engaged nearly the time stipulated for the completion of the work, and when the boring had been advanced to the depth of 1732 feet from the surface--the excavation suddenly collapsed in the upper strata, at about 100 feet from the ground, and filled up the bore. kind would have been ruined had the engineers of the town held him to the strict letter of his contract; but it was decided to behave in a liberal manner, and to release him from it, the town retaining his services for the completion of the well, as also the right to use his patent machinery. the difficulties encountered in carrying the excavation through the clays of the upper strata were found to be so serious that, under the new arrangement, it required six years and nine months of continuous efforts to reach the water-bearing stratum, of which time the far larger portion was employed in traversing the clay beds. the upper part of this well was finally lined with solid masonry, to the depth of 150 feet from the surface; and beyond that depth tubing of wood and iron was introduced. this tubing was continued to the depth of 1804 feet from the surface, and had at the bottom a length of copper pipe pierced with holes to allow the water to enter. at this depth the compound tubing could not be made to descend any lower; but the engineers employed by the city of paris were convinced that they could obtain the water by means of a preliminary boring; and therefore they proceeded to sink in the interior of the above tube of 3.2809 feet diameter, an inner tube 2 feet 4 inches diameter, formed of wrought-iron plates 2 inches thick, so as to enable them to traverse the clays encountered at this zone. at last, the water-bearing strata were met with on the 24th of september, 1861, at the depth of 1913 feet 10 inches from the ground-line; the yield of the well being, at the first stroke of the tool that pierced the crust, 15,000 cubic mètres in 24 hours, or 3,349,200 gallons a day; it quickly rose to 25,000 cubic mètres, or 5,582,000 gallons a day; and as long as the column of water rose without any sensible diminution, it continued to deliver a uniform quantity of 17,000 mètres, or 3,795,000 gallons a day. the total cost of this well was more than 40,000_l._, instead of 12,000_l._, at which kind had originally estimated it. [illustration: boring at grenelle, paris. figs. 259, 260.] [boring at grenelle, paris--_continued_. figs. 261. 262.] [illustration: boring at passy, paris. figs. 263, 264.] [illustration: boring at passy, paris--_continued_. figs. 265, 266.] it may be questioned whether the engineers of the town were justified in passing the contract with kind to finish the work within the time, and for the sum at which he undertook it; but they certainly treated him with kindness and consideration, in allowing him to conduct the work at the expense of the city of paris, for so long a period after the expiration of his contract. it seems, however, that the french well-borers could not at the time have attempted to continue the well upon any other system than that introduced by kind; that is to say, upon the supposition that it should be completed of the dimensions originally undertaken. experience has shown that both steining and tubing were badly executed at the well of passy. the masonry lining was introduced after kind's contract had expired, and when he had ceased to have the control of the works; the wrought-iron tubing at the lower part of the excavation being a subsequent idea. it has followed from this defective system of tubing--the wood necessarily yielding in the vertical joints--that the water in its upward passage escaped through the joints, and went to supply the basement beds of the paris basin, which are as much resorted to as the london sand-beds for an artesian supply; and, in fact, the level of the water has been raised in the neighbouring wells by the quantity let in from below, and the yield of the well itself has been proportionally diminished, until it has fallen to 450,000 gallons a day. that the increased yield of the neighbouring wells is to be accounted for by the escape of the water from the artesian boring is additionally proved by the temperature of the water in them; it is found to be nearly 82° fah., or nearly that observed in the water of passy. this was an unfortunate complication of the bargain made between kind and the municipal council; but it in no respect affects the choice of the boring machinery, which seems to have complied with all the conditions it was designed to meet. the descent of the tubes and their nature ought to have been the subject of special study by the engineers of the town, who should have known the nature of the strata to be traversed better than kind could be supposed to do, and should have insisted upon the tubing being executed of cast or wrought-iron, so as effectually to resist the passage of the water. at any rate, this precaution ought to have been taken in the portions of the well carried through the basement beds of the paris basin, or through the lower members of the chalk and the upper greensand. [illustration: well at ponders end. figs. 267, 268.] _ponders end_, middlesex.--at the works of the london jute company. it will be seen from the figs. 267, 268, that this well is bored all but the top 4 feet, which is 5 feet across and steined with 9-inch work. the uppermost tube is 12 inches in diameter, decreased to 9 inches, and then to 8 inches, and ending with a 6-inch bore, unlined, in the chalk. the strata passed were;- alluvium, 6 feet;- feet. in. clay and mud 3 6 peat 2 6 sand and shingle (gravel). 7 0 london clay, 15 feet;- blue clay 8 0 sandy clay (basement bed?) 7 0 reading beds, 49-1/2 feet;- dead sand 10 0 mottled clays 22 0 sand and metal (pyrites?) 1 0 sandy clay 3 0 sand and pebbles 4 0 dead sand 1 6 dead sand and pebbles 1 0 sand and pebbles 7 0 thanet sand (?), 35 feet;- green sand 27 0 dead sand 8 0 ------- to chalk 112 6 in chalk 290 6 ------- total 403 0 -------the water at this well overflows. * * * * * _freshwater_, isle of wight.--well, figs. 269, 270, sunk at golden hill for h.m. government. the diameter of the shaft is 4 feet 6 inches, brickwork 9 inches thick, there are 3 feet in cement at the top of the well, and 3 feet 9 inches at the bottom. there are four courses in cement every 5 feet, internal work four courses in cement every 10 feet. the bore-hole is lined throughout with pipes of 6 inches, 5 inches, and 4 inches diameter respectively. [illustration: well at freshwater, isle of wight. figs. 269, 270.] _winchfield_, hants.--well, figs. 271 to 273, at the brewery of messrs. w. cave and son. the shaft above the steining is lined with iron cylinders into which the bore-pipe is carried up. the strata passed were;- feet. made earth, soil, gravel, blue clay and dead sand 350 dark sandy clay 3 black pebbles 2 coloured clay 5 stone (septaria?) 2 coloured clay 22 coarse shifting sands 7 -- total 391 --[illustration: well at winchfield, hants. figs. 271-273.] the following table, compiled from the government memoirs and other reliable sources, furnishes in a condensed form the most important particulars relating to wells, and trial bore-holes comprised within the geographical area known as the london basin. the first column gives the name of the place where the well is situated, the second column that of the county, and the third column the precise locality. the following abbreviations have been employed: b. for bedfordshire; berks, berkshire; bucks, buckinghamshire; e., essex; h., hampshire; herts, hertfordshire; k., kent; m., middlesex; s., surrey. o.d. stands for, above ordnance datum; t., above trinity high-water mark. particulars of wells. +-------------+-------+-------------+----------------------------------------+ | | | | depth. | | name of | | +-------+-------+-------+-------+--------| | place. |county.| locality. | of | of |in ter-| in |to water| | | | |shaft. | bore. |tiary |chalk. | from | | | | | | |strata.| |surface.| | | | +-------+-------+-------+-------+--------+ | | | | remarks. | +-------------+-------+-------------+-------+-------+-------+-------+--------+ | | | | feet. | feet. | feet. | feet. | feet. | |abridge | e. |brewery | 100 | 190 | 290 | - | 30 | | | | |london clay, 280 feet. | | | | | | | | | | |acton | m. |mr. | | | | | | | | |engleheart's | - | - | 284 | 119 | 12 | | | | | | | | | | | ditto | " |mr. wood's | - | - | 315 | 135 | 40 | | | | | | | | | | | ditto, east| " |mr. davis's | - | - | 267 | 68 | | | | | | | | | | | |albany street| " |london | - | - | 182 | 125 | - | | | | |100 feet o.d. | | | | | | | | | | |aldershot | h. | - - | - | - | 194 | - | - | | place | | |260 feet o.d. | | | | | | | | | | | ditto | " | - - | - | - | 148 | 69-1/2| - | | | | |245 feet o.d. | | | | | | | | | | |amwell end | herts.|new river | 72 |347-3/4| 36 |383-3/4| - | | | |company |yield about 2,500,000 gallons a day. | | | | | | | | | | |arlesey | b. |asylum | 100 | 365 | 7 | 120 | - | | | | |233 feet o.d.; water rises into shaft; | | | | | yield 2640 gallons an hour. | | | | | | | | | | |ash | s. |s.w. railway | - | 600 | 370 | 230 | - | | | |station |290 feet o.d. | | | | | | | | | | |bank of | m. |london | 137 |197-1/2| 234-1/2| 100 | 88 | | england | | |about 27 feet t.; yield, 35 gallons | | | | | a minute. | | | | | | | | | | |bagshot | s. |orphan asylum| 123 | 523 | 646 | - | - | | | | |last 192 feet london clay. | | | | | | | | | | |balham hill | " |near clapham | - | - | 347 | - | - | | | |common |last 40 feet thanet sands. | | | | | | | | | | |barking | e. |byfron's | 140 | - | 140 | - | 30 | | | | |bottom in hard pebbles. | | | | | | | | | | |barnet, east | herts.|lion's down | 122 | 270 | 162 | 230 | 130 | | | | |shaft half steined, half iron cylinders.| | | | | | | | | | | ditto, new | " |near railway | 137 | 302 | 159 | 280 | 130 | | | |station | | | | | | | | | | | | | | | |battersea | s. |jones's works| 249 | - | 249 | | | | | | | | | | | | | ditto | " |beaufoy's | 240 | - | 240 | - | - | | | |works |yield said to equal 15,000 gallons a | | | | | day. | | | | | | | | | | |bearwood |berks. |mr. walters's| - | - | 350 | 15 | | | | | | | | | | | |beaumont |herts. |near cheshunt|183-1/2| - | 126-1/2| 57 | | |green | | | | | | | | | | | | | | | | | |belleisle | m. |pashes and | - | - | 185 | 118 | 118 | | | |co.'s | | | | | | | | | | | | | | | |berkeley | " |london | 160 | 156 | 224 | 92 | 80 | |square | | | | | | | | | | | | | | | | | |bermondsey | s. |crimscott | - | - | 120 | - | - | | | |street |9 feet o.d.; yield plentiful. | | | | | | | | | | | ditto | " |donkin's | - | 232 | 91-1/2 |140-1/2| 16 | | | |works |yield 30 gallons a minute. | | | | | | | | | | |berry green |herts. |hadham | 40 | 20 | 60 | - | 8 | | | | | | | | | | |bexley | k. |brickfield | 65 | 110 | 129-1/4| 45-3/4| 60 | | | | | | | | | | |bishop |herts. |waterworks | 160 | 140 | 116-1/2|183-1/2| 140 | |stortford | | |supply 10,000 gallons a minute. | | | | | | | | | | | ditto | " |hockerill | 85 | 125 | 90 | 120 | 78 | | | | |good supply. | | | | | | | | | | | ditto | " |new road | | 77 | - | 56 | 21 | | | | | | | | | | |blackfriars | m. |apothecaries'| - | - | 218 | 76 | | | | |hall | | | | | | | | | | | | | | | |blackheath | k. |near enfield | - | - | 109 | 30 | | | | |terrace | | | | | | | | | | | | | | | |boston heath | " |near | - | - | 130 | 70 | | | | |woolwich | | | | | | | | | | | | | | | |bow | m. |starch works | 176 | 148 | 174 | 150 | | | | | | | | | | | |boxley wood | k. |near |386-1/2|213-1/2| 3 | 600 | - | | | |maidstone |382 feet t.; last 78-1/2 feet in chalk, | | | | | marl, and gault. | | | | | | | | | | |braintree | e. |near pod's | 55 | 190 | 228 | 7 | 216 | | | |brook |yield, 11,500 gallons an hour. | | | | | | | | | | |brentford | m. |brewery | 30 | 338 | 315 | 53 | 5 | | | | | | | | | | |bromley | k. |gas works | 50 | 120 | 150 | 20 | - | | | | |supply abundant. | | | | | | | | | | | ditto | " |widmore kiln | 52 | 98 | 140 | 10 | | | | | | | | | | | | ditto | | ditto | 55 | 85 | 120 | 10 | 61 | | | | | | | | | | | ditto | " |tylney road | 77 | 85 | 137 | 25 | | | | | | | | | | | | ditto | " |waterworks | - | - | 70 | 180 | - | | | | |yield, 500 to 600 gallons a minute. | | | | | | | | | | |broxbourne |herts. | -- | 84 | - | 84 | 6 | - | | | | |water overflowed. | | | | | | | | | | |bushey | " |near | 142 | 24 | 145 | 21 | | | | |watford | | | | | | | | | | | | | | | |camberwell | s. |the grove | - | - | 208 | 300-1/2| 90 | | | | | | | | | | |camden | m. |l. and n.w. | 180 | 220 | 234 | 166 | 150 | |station | |railway |100 foot o.d. | | | | | | | | | | |camden town | m. |pickford's | - | - | 215 | 82 | 120 | | | | |good supply. | | | | | | | | | | | ditto | " |whitaker's | 235 | 75 | 210 | 90 | 190 | | | |brewery | | | | | | | | | | | | | | | |canterbury | k. |orphan asylum| - | - | 145 | - | 120 | | | | | | | | | | |caterham | s. |waterworks | - | - | 89 | 349 | - | | | | |709 feet t.; through chalk, and 39 feet | | | | | into upper greensand. | | | | | | | | | | |chelmsford | e. |moulsham | 200 | 368 | 366 | 202 | 76 | | | | |water overflowed at first. | | | | | | | | | | |cheshunt |herts. |new river | 144 | 27 |107-1/2| 63-1/2| 120 | | | |company |yield, 702,000 gallons a day. | | | | | | | | | | | ditto | " |theobald's | 71 |131-1/2|121-1/2| 81 | 65 | | | |park | | | | | | | | | | | | | | | |chiswell | m. |whitbread's | 183 | 150 | 183 | 150 | 132 | |street | |brewery | | | | | | | | | | | | | | | |chiswick | " |griffin | 204 | 200 | 297 | 107 | - | | | |brewery |yield, 14 gallons a minute. | | | | | | | | | | | ditto | " |lamb brewery | 203 | 194 | 293 | 104 | | | | | | | | | | | | ditto | " | ditto | 8 | 339 | 297 | 50 | | | | | | | | | | | |clewer green |berks. |capt. winter-| | | | | | | | |bottom's | 42 | 294 | 270 | 66 | | | | | | | | | | | | ditto | " |wycombe | 20 | 246 | 169 | 97 | | | | |cottage | | | | | | | | | | | | | | | |colnbrook | m. |paper mills | - | - | 207 | 175 | - | | | | |water found at 203 feet down. | | | | | | | | | | |colney hatch | " |asylum | 137 | 193 | 189 | 141 | | | | | | | | | | | |covent garden| " |market | 140 | 218 | 260 | 98 | 120 | | | | |70 feet o.d. | | | | | | | | | | |cricklewood | " |near | 225 | 85 | 291 | 19 | 110 | | | |hampstead |157 feet t. | | | | | | | | | | |croydon | s. |well for | 77 | - | 11 | 62 | - | | | |local board |yield 1,500,000 gallons a day. | | | | | | | | | | | ditto | " |new well | - | - | 15 | 137 | 11-1/2 | | | | | | | | | | |dartford | k. |paper mills | 34 | 49 | 33 | 50 | - | |creek | | |supply good. | | | | | | | | | | | ditto | " | ditto | 10 |240-1/2| 30 |220-1/2| 2 | | | | | | | | | | |denham |bucks. |tile house | 110 | 85 | 67 | 128 | 85 | | | | | | | | | | |deptford | k. |waterworks | 27 | - | 14 | 13 | - | | | | |20 feet o.d. | | | | | | | | | | |dulwich | s. |champion | - | - | 210 | 298 | | | | |hill | | | | | | | | | | | | | | | |east ham | |beckton gas | | | | | | |level | e. |works | 25 | 175 | 117 | 83 | 2 | | | | | | | | | | |edgware | m. |mr. day's | - | - | 290 | 45 | 40 | | | | | | | | | | |edgware road | " |the hyde | - | - | 101 | 37 | | | | | | | | | | | |edlesborough |bucks. |well, near | - | 301 | - | - | 70 | | | |mill |6-inch bore; through 50 feet of chalk | | | | | marl to lower greensand. | | | | | | | | | | |eltham | k. |dr. king's | 46 | - | 46 | - | 17 | | | | | | | | | | | ditto | " |the moat | 110 | - | 100 | 10 | | | | | | | | | | | | ditto | " |mr. tuck's | 44 | 123 |122-1/2| 44-1/2| 25 | | | | | | | | | | | ditto | " |well hall | - | 107 | 104 | 3 | | | | | | | | | | | | ditto park | " | - - | - | - | 122 | 94 | 170 | | | | | | | | | | |enfield lock | e. |small arms | 45 |239-1/2|152-1/2| 132 | 4 | | | |factory | | | | | | | | | | | | | | | |epping | " |waterworks | 275 | 129 | 400 | 4 | 260 | | | | |slow spring. | | | | | | | | | | |erith | k. |mineral oil | 166 | - | 146 | 20 | | | | |company | | | | | | | | | | | | | | | |farnham | s. |near hale | 176 | - | 80 | 96 | | | | |farm | | | | | | | | | | | | | | | |fleet street | m. |london, | 100 | 225 | 100 | 225 | | | | |shoe lane | | | | | | | | | | | | | | | |fulmer |bucks. |j. kay's | 85 | - | 47-3/4| 37-1/4| - | | | | |through gravel and reading beds. | | | | | | | | | | |golden lane | m. |baths and | 158 | - |151-1/2| 6-1/2| - | | | |washhouses |65 feet o.d. | | | | | | | | | | |gravesend | k. |church street| 10 | 234 | 120 | 124 | 8 | | | | |supply good and abundant. | | | | | | | | | | |greenwich | " |brewery | 22 | 158 | 80 | 100 | 11 | | | | | | | | | | | ditto | " |east street | 189 | - | 159 | 30 | | | | | | | | | | | | ditto | " |hospital | 155 | 150 |124-1/2|180-1/2| 19 | | | |brewery | 7 feet t.; supply 120 gallons a minute.| | | | | | | | | | |hackney road | m. |wiltshire | 96 |315-3/4|152-3/4| 259 | 80 | | | |brewery | | | | | | | | | | | | | | | |haggerstone | " |imperial gas |118-1/2| 302 |164-1/2| 256 | | | | |works | | | | | | | | | | | | | | | |hainault | e. | -- | 165 | - | 110 | 55 | | |forest | | | | | | | | | | | | | | | | | |halstead | " |the white | - | - | 170 | 30 | | | | |hart | | | | | | | | | | | | | | | |hammersmith | m. |average of | - | - | 245 | 68 | - | | | |four wells |yield, 16 gallons a minute. | | | | | | | | | | |hampstead | " |lower heath | 320 | 130 | 378 | 72 | - | | | | |now not used. | | | | | | | | | | |hampstead | " |eagle | 138 | 94 | 146 | 86 | 147 | |road | |brewery | | | | | | | | | | | | | | | | ditto | " |reservoir | 244 | - | 152 | 92 | 106 | | | | |77 feet t. | | | | | | | | | | |hanwell | " |asylum | 230 | 90 | 290 | 30 | - | | | | |water to surface. | | | | | | | | | | |harrow | " |waterworks |193-1/2| 219 |158-1/2| 254 | 125 | | | | |226 feet o.d. | | | | | | | | | | |haverstock | |orphan | 230 | 160 | 312 | 78 | 196 | |hill | " |school |176 feet o.d. | | | | | | | | | | |hayes | " |dawley | 19 | 300 | 231 | 88 | 27 | | | |court | | | | | | | | | | | | | | | |hendon | " |mr. booth's | - | - | 244 | 132 | 76 | | | | | | | | | | |highbury | " |brewery | 104 | 210 | 180 | 134 | 95 | | | | |yield, 1000 gallons an hour. | | | | | | | | | | | ditto | " |new park | 136 | 113 | 199 | 50 | | | | | | | | | | | |hoddesdon |herts. |new river | 52 | 234 |24-1/2 |261-1/2| 2 | | | |company | | | | | | | | | | | | | | | |holloway | m. | -- | 140 | 200 | 240 | 100 | | | | | | | | | | | | ditto | " |city prison | - | - | 217 | 102 | | | | | | | | | | | | ditto | " |hanley road | - | - | 67 | 13 | | | | | | | | | | | | ditto | " |redcap lane | - | - | 210 | 90 | | | | | | | | | | | | ditto | " |islington | 234 | 306 | 299 | 250 | | | | |workhouse | | | | | | | | | | | | | | | |hornsey | " |near church | - | - | 202 | 48 | | | | | | | | | | | | ditto | " |the priory | - | - | 225 | - | 70 | | | | | | | | | | |horselydown | s. |anchor | 100 | 162 | 158 | 104 | 50 | | | |brewery | | | | | | | | | | | | | | | |hoxton | m. | -- | 152 | 10 | 151 | 11 | | | | | | | | | | | |hyde park | " |st. | 200 |137-1/4|319-1/4| 18 | 100 | |corner | |george's |50 foot o.d.; yield, 3300 gallons | | | |hospital | an hour. | | | | | | | | | | |ickenham | " |public well | 64 | 80 | 64 | 80 | | | | | | | | | | | |isle of dogs | " |oil mills | 27 | 337 |124-1/2|239-1/2| 10 | | | | | | | | | | |isle of grain| k. |fort | 180 | 140 | 320 | - | 20 | | | | |21 feet o.d. | | | | | | | | | | |isleworth | m. |sion house | - | - | 420 | 115 | - | | | | |water overflowed at the rate of 5 | | | | | gallons a minute. | | | | | | | | | | | ditto | " |mr. | - | 327 | 327 | - | - | | | |wilmot's |water rose above surface. | | | | | | | | | | |islington | |webb's | - | 320 | 176 | 144 | 200 | |green | " |mineral | | | | | | | | |water works | | | | | | | | | | | | | | | |kensington | " |brewery | - | - | 197 | - | - | | | | |16 feet t. | | | | | | | | | | | ditto | " |britannia | | | | | | | | |brewery | 100 | 170 | 270 | - | 88 | | | | | | | | | | | ditto | " |horticultural| 200 | 201 | 317 | 84 | 100 | | | |society |60 feet o.d. | | | | | | | | | | | ditto | " |workhouse | - | - | 270 | 100 | | | | | | | | | | | | ditto | | | | | | | | | gardens | " |serpentine | 263 | 58 |263-1/4| 57-3/4| 105 | | | | | 60 feet o.d.; yield, 250 gallons a | | | | | minute. | | | | | | | | | | |kentish town | " |waterworks | 539 | 763 |324-1/2|644-3/4| - | | | | |through london clay, 236 feet; london | | | | | tertiaries, 88-1/2 feet; chalk, | | | | | 644-3/4 feet; upper greensand, 13-3/4 | | | | | feet; gault, 130-1/2 feet; and into | | | | | lower greensand (?), 188-1/2 feet. | | | | | | | | | | |kilburn | " |brewery | 250 | 30 | 235 | 45 | 150 | | | | | | | | | | |kingsbury | " |brent | 101 | 139 | 132 | 108 | | | | |reservoir | | | | | | | | | | | | | | | |kingston | s. |brook | 90 | 380 | 371 | 99 | - | |on-thames | |street |25 feet o.d.; yield, about 44,000 | | | | | gallons a day. | | | | | | | | | | |knightsbridge| m. | - - | 240 | - | 240 | - | 50 | | | | | | | | | | |lambeth | s. |beaufoy's | 100 | 275 | 201 | 174 | - | | | |vinegar works|yield, 92 gallons a minute. | | | | | | | | | | | ditto | " |south lambeth| 25 | 166 | 187 | 4 | | | | |road | | | | | | | | | | | | | | | | ditto | " |bethlehem | 30 | 161 | 191 | 20 | 15 | | | |hospital | | | | | | | | | | | | | | | | ditto | " |lion brewery,| - | - | 245 | 173 | 40 | | | |belvedere | | | | | | | | |road | | | | | | | | | | | | | | | | ditto | " |duke street, | 26 | 184 | 210 | | | | | |street, | | | | | | | | |clowes & | | | | | | | | |sons' | | | | | | | | | | | | | | | |lea bridge | m. |waterworks | 118 | - | 100 | 18 | | | | | | | | | | | |leicester | " | | | | | | | |square | |alhambra | 150 | 195 | 244 | 101 | | | | | | | | | | | |limehouse | " |johnson's, | 90 | 110 | 190 | 10 | | | | |commercial | | | | | | | | |road | | | | | | | | | | | | | | | | ditto | " |brewery, | - | - |139-1/2| | | | | |fore street | | | | | | | | | | | | | | | |liquorpond | " |reid's |222-1/2| 40 | 136 |126-1/2| 121 | |street | |brewery |70 feet o.d.; yield, 277,200 gallons in | | | | | 24 hours. | | | | | | | | | | |long acre | " |combe & co.'s| 263 | 228 | 223 | 268 | - | | | |brewery |70 feet o.d.; yield, 90 gallons a minute| | | | | | | | | | |loughton | e. | -- | - | 535 | 324 | 211 | 90 | | | | |no water from chalk. | | | | | | | | | | |lower morden | s. |on the green | 20 | 365 | 340 | 45 | - | | | | |water to surface. | | | | | | | | | | |luton | b. |waterworks | 50 | 272 | - | 322 | | | | | | | | | | | |maldon | e. |waterworks | 234 | - | 234 | - | - | | | | |entirely through london clay. | | | | | | | | | | |margate | k. |cobb's | 31 | 243 | - | 374 | | | | |brewery | | | | | | | | | | | | | | | |marylebone | m. |london; | 186 | 101 | 232 | 55 | 156 | |road | |a brewery | | | | | | | | | | | | | | | |mile end | " |mann's | 195 | - | 185 | 10 | | | | |brewery | | | | | | | | | | | | | | | | ditto | " |charrington's| 204 | - | 202 | 2 | 103 | | | |brewery |33-1/2 feet t.; yield, 60,000 to 70,000 | | | | | gallons a day. | | | | | | | | | | | ditto road | m. |city of | - | - | 175 | 10 | | | | |london union | | | | | | | | | | | | | | | |millbank | " |distillery | 115 | 190 | 205 | 100 | 70 | | | | |level of t. | | | | | | | | | | | ditto | " |westminster | - | - | 225 | 70 | - | | | |brewery |5-1/2 feet t. | | | | | | | | | | |mitcham | s. |nightingale's| - | 211 | 189 | 22 | | | | |factory | | | | | | | | | | | | | | | |monkham park | e. |near waltham | 225 | 125 | 304 | 76 | 50 | | | |abbey | | | | | | | | | | | | | | | |mortlake | s. |mortlake | 30 | 288 | 287 | 31 | 50 | | | |brewery |yield, 14,000 gallons a day. | | | | | | | | | | | ditto | " |mr. randell's| - | 365 | 315 | 50 | | | | | | | | | | | |new cross | k. |naval school | 50 | 130 | 125 | 55 | 60 | | | | | | | | | | |northolt | m. |near harrow | 12 | 228 | 180 | 60 | 4 | | | | | | | | | | |notting dale | " |near notting | - | - | 244 | 12 | | | | |hill | | | | | | | | | | | | | | | |notting hill | " |mr. knight's | - | - | 230 | 200 | | | | | | | | | | | |old kent road| s. |welsh ale | - | - | 30 | 170 | - | | | |brewery |10 feet o.d. | | | | | | | | | | |old windsor |berks. |pelham place | - | - | 222 | 9 | | | | | | | | | | | | ditto | " |the union | 60 | 180 | 240 | 47 | | | | | | | | | | | |orange street| m. |back of | | | | | | | | |national | | | | | | | | |gallery | 174 | 126 | 250 | 50 | 115 | | | | |42 feet t. | | | | | | | | | | |oxford street| " |star brewery | 166 | 170 | 158 | 178 | | | | | | | | | | | |peckham | s. |marlborough | - | - | 100 | 123 | | | | |house | | | | | | | | | | | | | | | |penge | " |palace | 250 | 310 | 358 | 202 | 90 | | | |grounds | | | | | | | | | | | | | | | |pentonville | m. |brewery, |219-1/2| - |219-1/2| 45 | 180 | | | |caledonian |to chalk. | | | |road | | | | | | | | | | | | | | | | ditto | " |prison | 170 |200-1/2|219-1/2| 151 | | | | | | | | | | | |pimlico | " |cubitt's | 188 | - | 188 | - | - | | | |works |2 feet t. | | | | | | | | | | | ditto | " |brewer street| 30 | 368 | 271 | 127 | | | | | | | | | | | | ditto | " |simpson's | - | - | 231 | 100 | 36 | | | |factory |1 foot t. | | | | | | | | | | |pinner | " |hatch end | 140 | - | 60 | 80 | | | | | | | | | | | |plaistow | e. |odam's manure| - | - |170-1/2| 128 | | | | |works | | | | | | | | | | | | | | | |ponders end | m. |london jute | 4 | 399 |112-1/2|290-1/2| - | | | |company |water overflows. | | | | | | | | | | | ditto | " |crape works | 20 | 42 | 62 | | | | | | | | | | | | | ditto | " |local board | - | - | 106 | 96-1/2| | | | |(speller) | | | | | | | | | | | | | | | | ditto | " |waterworks | 23 | 181 | 97 | 107 | - | | | | |43 feet t. | | | | | | | | | | |pudsey hall | e. |near | 297 | - | 297 | - | - | | | |canewdon |water abundant and good. | | | | | | | | | | |ratcliffe | m. |queen's head | - | - | 160 | 200 | | | | |brewery | | | | | | | | | | | | | | | | ditto | " |marine | 16 | 236 | 150 | 102 | | | | |brewery | | | | | | | | | | | | | | | | ditto | " |ravenhill's | - | 137 | | | | | | | | | | | | | |regent's park| " |colosseum | 150 | 100 | 171 | 79 | | | | | | | | | | | | ditto | " |mr. day's | - | - | 184 | 216 | 80 | | | | | | | | | | | ditto | " |zoological | 183 | 91 | 224 | 50 | 120 | | | |gardens |yield, 90,000 gallons a day. | | | | | | | | | | |richmond | s. |old | - | - | 276 | 103 | | | | |waterworks | | | | | | | | | | | | | | | | ditto | " |star and | - | - | 416 | 76 | | | | |garter | | | | | | | | | | | | | | | |romford | e. |ind, coope, | 155 | - | 145 | 10 | | | | |& co. | | | | | | | | | | | | | | | |rotherhithe | s. |brandram's | 30 | 222 | 107 | 145 | 27 | | | |works |yield, 100,000 gallons in 12 hours. | | | | | | | | | | | ditto | " |tunnel | - | - | 125 | 135 | - | | | |flour mills |15 feet o.d.; yield, 80 gallons a | | | | | minute. | | | | | | | | | | |ruislip | m. |near "the | 15 | 90-3/4| 75-3/4| 30 | - | | | |george" |water to surface. | | | | | | | | | | |saffron | e. | - - | - | - | - | 1000 | | |walden | | | | | | | | | | | | | | | | | |sandhurst |berks. |well at | - | 603 | - | - | - | | | |college |trial boring; chalk reached. | | | | | | | | | | |sandwich | k. |the bank | 70 | - | 62 | 8 | 20 | | | | | | | | | | |sheerness | " |waterworks | 300 | 84 | 384 | - | - | | | | |5-1/2 feet o.d.; yield, 10,000 gallons | | | | | an hour. | | | | | | | | | | | ditto | " |dockyard | 330 | 125 | 455 | - | 53 | | | | |yield, 675 gallons an hour. | | | | | | | | | | |shoreditch | m. |truman's | 300 | 230 | 199 | 331 | 120 | | | |brewery |yield, 7-1/2 gallons a minute. | | | | | | | | | | |shorne meade | | | | | | | | |fort | k. |near | 112 | - | 77-1/2| 34-1/2| | | | |gravesend | | | | | | | | | | | | | | | |shortlands | " |near | 59 | 150 | 109 | 100 | 61 | | | |bromley |yield, 1000 gallons an hour. | | | | | | | | | | |slough |bucks. |eton union | 28 | 103 | 107 | 24 | | | | | | | | | | | | ditto | " |royal nursery| - | - | 94 | 17-1/2| | | | | | | | | | | | ditto | " |upton park | - | - |102-1/4|170-1/4| | | | | | | | | | | | ditto | " |waterworks | 117 | - | 90 | 27 | 7 | | | | |heading into chalk. | | | | | | | | | | |smithfield | m. |booth's | - | - | 230 | 70 | 70 | | | |distillery | | | | | | | | | | | | | | | |southend | e. |waterworks | 417 | - | 417 | - | 100 | | | | |old well. | | | | | | | | | | |southwark | s. |barclay's | 115 | 288 | 212 | 211 | - | | | |brewery |level of t.; yield, 300 gallons a | | | | | minute. | | | | | | | | | | | ditto | " |guy's | 132 | 173 | 196 | 109 | 84 | | | |hospital |2 feet t.; yield, 33 gallons a minute. | | | | | | | | | | |staines | m. |ashby's | - | - | 369 | 154 | - | | | |brewery |water to surface. | | | | | | | | | | |stifford | e. |s.e. of | 63 | - | 33 | 30 | | | | |church | | | | | | | | | | | | | | | |stockwell | s. |waltham's | 100 | 210 | 210 | 100 | 46 | |green | |brewery |yield, 33 gallons a minute. | | | | | | | | | | | ditto | " |hammerton's | 25 | 186 | 211 | 154 | - | | | |brewery |yield, 46 gallons a minute. | | | | | | | | | | |stratford | e. |great eastern| 56 | 344 | 106 | 294 | | | | |works | | | | | | | | | | | | | | | | ditto | " |savill bros.'|112-1/2| - |109-1/2| 3 | | | | |brewery | | | | | | | | | | | | | | | | ditto | " |langthorn | 60 | 395 | 132 | 323 | - | | | |chemical |supply abundant. | | | |works | | | | | | | | | | | | | | | |streatham | s. |the common | 100 | 185 | 285 | | | | | | | | | | | | |sudbury | m. |london and | 200 | - | 120 | 80 | | | | |north-western| | | | | | | | |rail. station| | | | | | | | | | | | | | | |tottenham | " |warne's | - | - | 147 | 104 | | | | |works | | | | | | | | | | | | | | | | ditto | " |long water | - | - |149-1/2|101-1/2| | | | | | | | | | | | ditto | " |tottenham | - | 253 | 153 | 100 | | | | |hall | | | | | | | | | | | | | | | |tottenham | |meux's | 188 | 622 | 156 | 654 | - | |court road | " |brewery |85 feet o.d.; yield, 12-1/2 gallons | | | | | a minute. | | | | | | | | | | |tower hill | " |royal mint |195-1/2| 202 |195-1/2| 202 | 80 | | | | | | | | | | |trafalgar | " |london | 168 | 228 | 248 | 148 | - | |square | | |yield, 450 gallons a minute. | | | | | | | | | | |upchurch | k. |burntwick | - | 236 | 236 | | | | | |island | | | | | | | | | | | | | | | | ditto | " |milford hope | - | 304 | 210 | 94 | - | | | |marshes |good supply at bottom. | | | | | | | | | | |upper thames | m. |city of | 90 | 415 | 210 | 295 | 10 | |street | |london | | | | | | | | |brewery | | | | | | | | | | | | | | | |uxbridge | " |the dolphin | 121 | - | 81-1/2| 39-1/2| 3 | | | | | | | | | | | ditto | " |near market | - | - | 104 | 28 | 15-1/2 | | | |place | | | | | | | | | | | | | | | | ditto | " |page's lane | 98 | - | 98 | | | | | | | | | | | | | ditto | " |town well | - | - | 109 | 30 | 19 | | | | | | | | | | | ditto | " |near | 24 | 84 | 108 | - | 19 | | | |"king's arms"|to chalk. | | | | | | | | | | | ditto | " |new year's | 63 | - | 63 | - | 51 | | | |green farm | | | | | | | | | | | | | | | | ditto | " |hurdle yard | 78 | 39-1/2| 78 | 39-1/2| | | | | | | | | | | | ditto | " |near meeting | 41-1/2|109-1/2| 115 | 36 | 39 | | | |house | | | | | | | | | | | | | | | | ditto | " |the union | 51 | 162 | 175 | 38 | 29 | | | | | | | | | | |vauxhall | s. |burnett's | 140 | 186 | 224 | 102 | 55 | | | |distillery |yield, 80 gallons a minute. | | | | | | | | | | |waltham abbey| e. |brewery | 164 | - | 160 | 4 | - | | | | |water supply from bed of sand. | | | | | | | | | | |walthamstow | " |east london | - | - | 152 | 140 | - | |marsh | |waterworks |15 feet t. | | | | | | | | | | |wandworth | s. |young & | 170 | 164 | 274 | 60 | 45 | | | |bainbridge's |yield, 10 gallons a minute. | | | | | | | | | | | ditto | " |prison | - | - | 357 |126-1/2| 80 | | | | |yield, 27 gallons a minute. | | | | | | | | | | | ditto | " |county asylum| - | - | 331 | 6 | 30 | | | | | | | | | | |westbourne | m. |hippodrome | 240 | 67 | 300 | 7 | | |grove | | | | | | | | | | | | | | | | | |west drayton | " |victoria | 12 | 274 | 186 | 100 | - | | | |oil mills |water overflowed. | | | | | | | | | | | ditto | " |vitriol works| - | - |133-1/2| 45-1/2| | | | | | | | | | | | ditto | " |drayton | 3 | 146 | 149 | - | - | | | |mills |to chalk. | | | | | | | | | | |west ham | e. |mr. tucker's | - | - | 132 | 306 | | | | | | | | | | | | ditto | " |union | - | - | 110 | 55 | | | | | | | | | | | |west india | m. |south of | - | - | 120 | 240 | | |dock | |export dock | | | | | | | | | | | | | | | |westminster | " |artillery | - | - | 230 | | | | | |brewery | | | | | | | | | | | | | | | | ditto | " |chartered | - | - | 225 | | | | | |gas works | | | | | | | | | | | | | | | | ditto | " |vickers' | 116 | 184 | 249 | 51 | 70 | | | |distillery |yield, 94 gallons a minute. | | | | | | | | | | | ditto | " |swallow | - | - | 210 | - | 60 | | | |street | | | | | | | | | | | | | | | |whitechapel | " |furze's | 130 | 218 | 248 | 100 | | | | |brewery | | | | | | | | | | | | | | | | ditto | " |smith's | 106 | 264 | 210 | 160 | 36 | | | |distillery |36 feet t. | | | | | | | | | | | ditto | " |smith, druce,|141-1/2| - |141-1/2| - | 85 | | | |& co.'s |39 feet t. | | | | | | | | | | |willesden | " |mr. kilsby's | - | - | 273 | 97 | 30 | | | | | | | | | | |wimbledon | s. |convalescent | 200 | 367 | 537 | 30 | 50 | | | |hospital | | | | | | | | | | | | | | | | ditto, new | " |opposite | | | 193 | 75 | | | | |"white hart" | | | | | | | | | | | | | | | |windsor |berks. |clower lodge | 40 | 175 | 175 | 40 | | | | | | | | | | | | ditto | " |royal | 72 | | 72 | | | | | |brewery |through clay and running sand to chalk. | | | | | | | | | | | ditto | " |jennings' | | | | | | | | |brewery | | | 30 | 500 | 12 | | | | | | | | | | |winkfield | " |captain | | | 304 | 126 | 70 | |plain | |forbes' | | | | | | | | | | | | | | | |witham | e. | -- | - | - | 306 | - | 5 | | | | | | | | | | |woodley lodge|berks. |3 miles east | 95 | 35 | 130 | | | | | |of reading | | | | | | | | | | | | | | | |woolwich | k. |well of | - | - | 54-1/2|311-1/2| 37 | | | |arsenal | | | | | | | | | | | | | | | | ditto | " |paper | - | 550 | 5-1/2|544-1/2| - | | | |factory |yield, 650 gallons a minute. | | | | | | | | | | | ditto | " |dockyard | - | 608 | 20 | 588 | 70 | | | | |yield good. | | | | | | | | | | |wormley |herts. |nunsbury | 26 | 76-1/2| 80-1/2| 22 | | | | | |water overflows. | | | | | | | | | | | ditto | " |west end | 85 |150-1/2| 72 | 63-1/2| 62 | | | | | | | | | | |wormwood | m. | -- | - | - | 250 | 116 | 5 | |scrubbs | | | | | | | | +-------------+-------+-------------+-------+-------+-------+-------+--------+ chapter viii. tables and miscellaneous information. the following tabulated form shows the order of succession of the various stratified rocks with their usual thicknesses. -----------------+------------------------------------+----------- | | thickness groups. | strata. | in feet. -----------------+------------------------------------+----------- | | cainozoic, or tertiary. | | | { recent | 1 modern deposits. | { | | { pleistocene | 2 drift and gravel beds | 20 to 100 { | | { {| 3 mammaliferous crag | 10 to 40 { pliocene {| 4 red crag | 30 { {| 5 suffolk (coralline) crag | 30 { | | { miocene {| 6 faluns (touraine) molasse }| { {| sandstones }| 6000 { | | { eocene | | { {| 7 hempstead series | 170 { upper {| 8 bembridge series | 110 { {| 9 headon series | 200 { | | { middle | 10 barton beds | 300 { | | { {| 11 bagshot and bracklesham series | 1200 { lower {| 12 london clay and bognor beds | 200 to 520 { {| 13 woolwich beds & thanet sands | 100 | | | | mesozoic, or secondary. | { {| 14 maestricht beds | 110 { {| 15 upper chalk | 300 { {| 16 lower chalk and chalk marl | 400 { cretaceous {| 17 upper greensand | 130 { {| 18 gault | 100 { {| 19 speeton clay | 130 { {| 20 lower greensand | 250 { | | { wealden {| 21 weald clay | 150 { {| 22 hastings sands | 600 { | | { purbeck | 23 purbeck beds | 150 { | | { upper {| 24 portland rock and sand | 150 { oolite {| 25 kimmeridge clay | 400 { | | { {| 26 upper calcareous grit | 40 { middle {| 27 coralline oolite | 30 { oolite {| 28 lower calcareous grit | 40 { {| 29 oxford clay | 400 { {| 30 kellaways rock | 30 { | | { {| 31 cornbrash | 10 { {| 32 forest marble and bradford clay | 50 { lower {| 33 great oolite | 120 { oolite {| 34 stonesfield slate | 9 { {| 35 fullers' earth | 50 to 150 { {| 36 inferior oolite | 80 to 250 { | | { {| 37 upper lias shale | 50 to 300 { lias {| 38 marlstone and shale | 30 to 200 { {| 39 lower lias and bone beds | 100 to 300 { | | { triassic, or {| 40 variegated marls or keuper | 800 { new red {| 41 muschelkalk | { sandstone {| 42 red sandstone or bunter | 600 | | | | palæozoic, or primary. | | | { permian or {| 43 red sand and marl | 50 { magnesian {| 44 magnesian limestone | 300 { limestone {| 45 marl slate | 60 { {| 46 lower red sandstone | 200 { | | { {| 47 coal measures |3000 to 12,000 { carboniferous{| 48 millstone grit | 600 { {| 49 mountain limestone | 500 to 1400 { {| 50 limestone shales | 1000 { | | { devonian or {| 51 upper devonian }| { old red {| 52 middle devonian }|3000 to 8000 { sandstone {| 53 lower devonian and tilestones }| { | | { silurian | | { {| 54 ludlow rocks | 2000 { upper {| 55 wenlock beds | 1800 { {| 56 woolhope series | 3050 { | | { middle | 57 llandovery rocks | 2000 { | | { {| 58 caradoc and bala rocks | 5000 { lower {| 59 llandeilo rocks | 4000 { {| 60 lingula flags | 8000 { | | { cambrian | 61 longmynd and cambrian rocks | 20,000 | | | | azoic. | | | | { metamorphic {| clay slate, mica-schist. | { {| gneiss, quartz rocks. | { | | { igneous | granite. | { | | the quantity of excavation in wells for each foot in depth. (hurst.) +-------------+---------------+ | diameter of | | | excavation. | quantity. | +-------------+---------------+ | ft. in. | cubic yards. | | 3 0 | ·2618 | | 3 3 | ·3072 | | 3 6 | ·3563 | | 3 9 | ·4091 | | 4 0 | ·4654 | | 4 3 | ·5254 | | 4 6 | ·5890 | | 4 9 | ·6563 | | 5 0 | ·7272 | | 5 3 | ·8018 | | 5 6 | ·8799 | | 5 9 | ·9617 | | 6 0 | 1·0472 | | 6 3 | 1·1363 | | 6 6 | 1·2290 | | 6 9 | 1·3254 | | 7 0 | 1·4254 | | 7 3 | 1·5290 | | 7 6 | 1·6362 | | 7 9 | 1·7472 | | 8 0 | 1·8617 | | 8 6 | 2·1017 | | 9 0 | 2·3562 | | 9 6 | 2·6253 | | 10 0 | 2·9089 | | 10 6 | 3·2070 | | 11 0 | 3·5198 | | 12 0 | 4·1888 | +-------------+---------------+ the measure in gallons, and the weight in pounds, of water contained in wells, for each foot in depth. ------------+----------------+--------- diameter. | no. of galls. | weight. ------------+----------------+--------- ft. in. | | 2 0 | 19·61 | 196·1 2 6 | 30·56 | 305·6 3 0 | 43·97 | 439·7 3 6 | 60·00 | 600·0 4 0 | 78·19 | 781·9 4 6 | 98·87 | 988·7 5 0 | 122·23 | 1222·3 5 6 | 147·96 | 1479·6 6 0 | 175·99 | 1759·9 6 6 | 206·59 | 2065·9 7 0 | 239·05 | 2395·0 7 6 | 275·49 | 2754·9 8 0 | 313·43 | 3134·3 8 6 | 353·03 | 3533·0 9 0 | 395·42 | 3954·2 9 6 | 441·71 | 4417·1 10 0 | 489·93 | 4899·3 ------------+----------------+---------brickwork. the number of bricks and quantity of brickwork in wells for each foot in depth. (hurst.) ------+------------------------------+----------------------------- | half-brick thick. | one brick thick. +-----------------+------------+-----------------+----------- |number of bricks.| |number of bricks.| +------+----------+ cubic feet +------+----------+ cubic feet | laid | laid in | of | laid | laid in | of | dry. | mortar. | brickwork. | dry. | mortar. | brickwork. ------+------+----------+------------+------+----------+----------- 1·0 | 28 | 23 | 1·6198 | 70 | 58 | 4·1233 1·3 | 33 | 27 | 1·8145 | 80 | 66 | 4·7124 1·6 | 38 | 31 | 2·2089 | 90 | 74 | 5·3015 1·9 | 43 | 35 | 2·7979 | 112 | 92 | 6·4795 2·3 | 53 | 44 | 3·0926 | 122 | 100 | 7·0686 2·6 | 58 | 48 | 3·3870 | 132 | 108 | 7·6577 3·0 | 68 | 57 | 3·9760 | 154 | 126 | 8·8357 3·6 | 79 | 65 | 4·5651 | 174 | 142 | 10·0139 4·0 | 89 | 73 | 5·1541 | 194 | 159 | 11·1919 4·6 | 100 | 82 | 5·7432 | 214 | 176 | 12·3701 5·0 | 110 | 90 | 6·3322 | 234 | 192 | 13·5481 5·6 | 120 | 98 | 6·9213 | 254 | 209 | 14·7263 6·0 | 130 | 107 | 7·5103 | 276 | 226 | 15·9043 6·6 | 140 | 115 | 8·0994 | 296 | 242 | 17·0825 7·0 | 150 | 123 | 8·6884 | 316 | 260 | 18·2605 7·6 | 160 | 131 | 9·2775 | 336 | 276 | 19·4387 8·0 | 170 | 140 | 9·8665 | 358 | 292 | 20·6167 8·6 | 180 | 148 | 10·4556 | 378 | 308 | 21·7949 9·0 | 191 | 156 | 11·0446 | 398 | 326 | 22·9729 10·0 | 212 | 174 | 12·2227 | 438 | 360 | 25·3291 ------+------+----------+------------+------+----------+-----------good bricks are characterized as being regular in shape, with plane parallel surfaces, and sharp right-angles; clear ringing sound when struck, a compact uniform structure when broken, and freedom from air-bubbles and cracks. they should not absorb more than one-fifteenth of their weight in water. after making liberal allowance for waste, 9 bricks will build a square foot 9 inches thick, or 900, 100 square feet, or say 2880 to the rood of 9-inch work, which gives the simple rule of 80 bricks = a square yard of 9-inch work. the resistance to crushing is from 1200 to 4500 lb. a square inch; the resistance to fracture, from 600 to 2500 lb. a square inch; tensile strength, 275 lb. a square inch; weight, in mortar, 175 lb. a cubic foot; in cement, 125 lb. a cubic foot. compressed bricks are much heavier, and consequently proportionately stronger, than those of ordinary make. storing well-water. the reservoirs for storing well-water should be covered with brick arches, as the water is generally found to become rapidly impure on being exposed to the sunlight, principally owing to the rapid growth of vegetation. various methods have been tried, such as keeping up a constant current of fresh water through them, and a liberal use of caustic lime; but so rapid is the growth of the vegetation, as well as the change in the colour of the water, that a few hours of bright sunlight may suffice to spoil several million gallons. these bad results are completely prevented by covering the reservoirs. hints on superintending well-work. the engineer who has to superintend the construction of a well should be ever on the watch to see whether, in the course of the work, the strata become so modified as to overthrow conclusions previously arrived at, and on account of which the well has been undertaken. a journal of everything connected with the work should be carefully made, and if this one point alone is attended to it will be found of great service both for present and future reference. before commencing a well a wooden box should be provided, divided by a number of partitions into small boxes; these serve to keep specimens of the strata, which should be numbered consecutively and described against corresponding numbers in the journal. at each change of character in the strata, as well as every time the boring rods are drawn to surface, the soil should be carefully examined, and at each change a small quantity placed in one of the divisions of the core box, noting the depth at which it was obtained, with other necessary particulars. a note should be made of all the different water-levels passed through, the height of the well above the river near which it is situated, as well as its height above the sea. the memoranda in the journal relating to accidents should be especially clear and distinct in their details; it is necessary to describe the effects of each tool used in the search for, or recovery of, broken tools in a bore-hole, in order to suit the case with the proper appliances, for without precaution we may seek for a tool indefinitely without being sure of touching it, and perhaps aggravate the evil instead of remedying it. it is by no means a bad plan to make rough notes of all immediate remarks or impressions, in such a manner as to form a full and detailed account of any incidents which occur either in raising or lowering the tools. at the time of an accident a well kept journal is a precious resource, and at a given moment all previous observations, trivial as they may have often seemed, will form a valuable clue to explain difficulties, without this aid perfectly inexplicable. when an engineer has a certain latitude allowed him in the choice of the position for a well, he should not, other things being equal, neglect the advantages which will be derived from the proximity of a road for the transport of his supplies; of a well, if not a brook, from which to obtain the water necessary for the cleansing of the tools; and of a neighbouring dwelling, to facilitate his active supervision. this supervision, having often to be carried on both day and night, should be the object of particular study; well carried out, it may be effective, while at the same time allowing a great amount of liberty; badly carried out, however fatiguing it may be, it will be incomplete. rate of progress of boring. (andré.) there are probably no engineering operations in which the rate of progress is so variable as it is in that of boring. that such must necessarily be the case will be obvious when we bear in mind that the strata composing the earth's crust consist of very different materials; that these materials are mingled in very different proportions, and that they have in different parts been subjected to the action of very different agencies operating with very different degrees of intensity. hence it arises not only that some kinds of rocks require a much longer time to bore through than others, but also that the length of time may vary in rocks of the same character, and that the character may change within a short horizontal distance. thus it is utterly impossible to predicate concerning the length of time which a boring in an unknown district may occupy, and only a rough approximation can be arrived at in the case of localities whose geological constitution has been generally determined. such an approximation may, however, be attained to, and it is useful in estimating the probable cost; and to attain the same end, for unknown localities, an average may be taken of the time required in districts of a similar geological character. the following, which are given for this purpose, are the averages of a great number of borings executed under various conditions by the ordinary methods. the progress indicated represents that made in one day of eleven hours. ft. in. 1. tertiary and cretaceous strata, to a depth of 100 yards, average progress 1 8 2. cretaceous strata, without flints " 250 " " 2 1 3. cretaceous strata, with flints " 250 " " 1 4 4. new red sandstone " 250 " " 1 10 5. new red sandstone " 500 " " 1 5 6. permian strata " 250 " " 2 0 7. coal measures " 200 " " 2 3 8. coal measures " 400 " " 1 8 --- ----- general average 275 1 9 --- -----when the cost of materials and labour is known, that of the boring may be approximately estimated from the above averages. should hard limestone or igneous rock be met with, the rate of progress may be less than half the above general average. below 100 yards, not only does the rate of progress rapidly increase, but the material required diminishes in like proportion, so that for superficial borings no surface erections are needed, and the cost sinks to two or three shillings a yard. cost of boring. the cost of boring when executed by contract has already been treated of at page 80. the following formula will furnish the same results as the rule there given, but with the least possible labour of calculation; _x_ = 0·5_d_(·187 + ·0187_d_); _x_ being the sum sought, in pounds, and _d_ the depth of the boring in yards. _example._ let it be required to know the cost of a bore-hole 250 yards deep. here 125{·187 + (·0187 × 250)} = £607·75. tempering boring chisels. 1. heat the chisel to a blood red heat, and then hammer it until nearly cold; again, heat it to a blood red and quench as quickly as possible in 3 gallons of water in which is dissolved 2 oz. of oil of vitriol, 2 oz. of soda, and 1/2 oz. of saltpetre, or 2 oz. of sal ammoniac, 2 oz. of spirit of nitre, 1 oz. of oil of vitriol: the chisel to remain in the liquor until it is cold. 2. to 3 gallons of water add 3 oz. of spirit of nitre, 3 oz. of spirits of hartshorn, 3 oz. of white vitriol, 3 oz. sal ammoniac, 3 oz. alum, 6 oz. of salt, with a double handful of hoof-parings, the chisel to be heated to a dark cherry red. gases in wells. the most abundant deleterious gas met with in wells is carbonic acid, which extinguishes flame and is fatal to animal life. carbonic acid is most frequently met with in the chalk, where it has been found to exist in greater quantity in the lower than in the upper portion of the formation, and in that division to be unequally distributed. fatal effects from it at epsom, 200 feet down, and in norbury park, near dorking, 400 feet down, have been recorded. at bexley heath, after sinking through 140 feet of gravel and sand and 30 feet of chalk, it rushed out and extinguished the candles of the workmen. air mixed with one-tenth of this gas will extinguish lights; it is very poisonous, and when the atmosphere contains 8 per cent. or more there is danger of suffocation. when present it is found most abundantly in the lower parts of a well from its great specific gravity. sulphuretted hydrogen is also occasionally met with, and is supposed to be generated from the decomposition of water and iron pyrites. in districts in which the chalk is covered with sand and london clay, carburetted hydrogen is occasionally emitted, but more frequently sulphuretted hydrogen. carburetted hydrogen seldom inflames in wells, but in making the thames tunnel it sometimes issued in such abundance as to explode by the lights and scorch the workmen. sulphuretted hydrogen also streamed out in the same place, but in no instance with fatal effects. at ash, near farnham, a well was dug in sand to the depth of 36 feet, and one of the workmen descending into it was instantly suffocated. fatal effects have also resulted elsewhere from the accumulation of this gas in wells. index. abridge, well at, 190 accident tools, mather and platt's, 138-143 acton, wells at, 190 africa, rainfall in, 30 air freshening in wells, 53 albany street, well at, 190 aldershot place, wells at, 190 alluvion, 5, 7 america, north, rainfall, 30, 31 ---south, 31 american tube well, 81 amwell end, well at, 190 apothecaries' hall, well at, 191 apparatus for boring, 68, 71, 72 arlesey, well at, 190 artesian well, definition, 2 ------causes of failure, 2-4 ash, well at, 190 asia, rainfall in, 29, 30 augers, 62-64 available rainfall, 27 bagshot sands, 5 ---well at, 190 balance-beam, kind's, 91 balham hill, well at, 190 ball-clack, 91 bank of england, well at, 190 bare outcrop, 18-21 barking, well at, 190 barnet, wells at, 190 battersea, wells at, 190 bearwood, well at, 191 beaumont green, well at, 191 bell-box, 64 belleisle, well at, 191 berkeley square, well at, 191 bermondsey, wells at, 191 berry green, well at, 191 bexley, well at, 191 bexley heath, wells at, 21 bickford's fuse, 50 birkenhead, wells at, 155 birmingham, wells at, 156 bishop stortford, wells at, 167, 191 blackfriars, well at, 191 blackheath, well at, 191 blasting, sinking by, 44 bootle, wells at, 158 borers or drills, 47 boring, 60-80 ---apparatus for, 61, 68, 71, 72 ---at great depths, 85 ---cost of, 80, 209 ---chisels, 62, 87, 102, 115, 132 ---difficulties of, 80 ---direct from surface, 72 ---kind-chaudron system, 93 ---mather and platt's system, 126-149 ---machine, mather and platt's, 127-130 ---rate of, 207, 208 ---rods, 64, 65 ---rods, hollow, 80 ---sheer-frame _frontispiece_, 72 ---tools, 62-79 boston heath, well at, 191 bow, well at, 191 box-clutch, 107 box-joint for mizer, 57 boxley wood, well at, 191 braintree, well at, 168, 191 breaking-up bar, 139, 141 brentford, well at, 191 brick steining, 55, 59, 205 bricks, good, characteristics, 205 brickwork in wells, 205 brighton, wells at, 168 broken tubing, 74-79 ---rods, extracting, 64, 107, 122 bromley, wells at, 191 broxbourne, well at, 191 bucket, sinkers', 67, 150 bucket grapnel, 140, 142 bull or clay-iron, 50 bunter sandstone, 35, 36 burton-on-trent, wells at, 156 bushey, well at, 191 butte-aux-cailles, well at, 179 camberwell, well at, 191 camden station, well at, 191 camden town, wells at, 192 canterbury, well at, 192 carbonic acid in wells, 209 carburetted hydrogen in wells, 210 cartridges for blasting, 50 cast-iron tubes, 66, 143 caterham, well at, 192 cement backing, 111, 112 ---ladle for tubbing, 111, 112 chalk, 5, 7 ---headings or tunnels in, 54 ---level of water in, 8 ---marl, 5 ---rainfall on, 27 charge of powder, rule for, 45, 46 chelmsford, well at, 169, 192 cheshire, thickness of trias, 36 cheshunt, wells at, 170, 192 chinese system of boring, 60, 61 chisels for boring, 62, 87, 102, 115, 132 ---or trepans, 113, 115 ---tempering, 209 chiswell street, well at, 192 chiswick, wells at, 192 clamp for tube well, 81 claw grapnel, 139 clay, 12 ---grapnel, 140, 141, 143 ---iron or bull, 50 cleaning pipes, tube well, 83 ---shot-holes, 49 clewer green, wells at, 192 cold-drawn wrought-iron tubes, 66 colnbrook, well at, 192 colney hatch, well at, 192 core box, 206 core grapnel, 140 cost of boring, 80, 209 ---of headings in sandstone, 54 covent garden, well at, 192 coventry, wells at, 155 covered outcrop, 21 cretaceous strata, 167-201 crewe, wells at, 158 cribs, fixing, 94 cricklewood, well at, 192 crow, kind-chaudron, 107 crow's foot, 64 croydon, wells at, 192 curb in underpinning, 40 cutting grapnel, 139, 141 cylinder, mather and platt's, 130 cylinders, iron for lining, 56 dartford creek, wells at, 193 deep boring, 72, 85-150 defective tubing, 74-79 denham, well at, 193 deptford, well at, 193 depth of rainfall, 26 difficulties of boring, 80 dip-bucket, 150 dogs, 65, 67 dolly, 67, 74 dorking, well at, 171 drainage area, definition, 25 drift, 5-7, 21, 22 ---outcrop covered by, 21 driving tubes, 67, 73, 74 ---tube well, 81-83 drum curb, 42 dru's first trepan, 113 ---system, 113 -------, summary, 126 dudlow lane well, 160 dulwich, well at, 193 durham, sinkings in, 93 ---wells in, 155 dyke, effect of, 4 dynamite, 44 earth-fast, definition, 44 east barnet, well at, 190 east ham level, well at, 193 edgware, well at, 193 edgware road, well at, 193 edlesborough, well at, 193 eltham, wells at, 193 enfield lock, well at, 193 enlarging hole below tubes, 67, 68 ---shot-holes, 48 epping, well at, 193 erith, well at, 193 europe, rainfall in, 28, 29 euyenhausen joint, 85, 88 excavation in wells, table of, 204 explosive agents, use of, 45 fan, for ventilation, 52 farnham, well at, 193 fault, effect of, 4 fauvelle's system, 79 fissures, 2, 12 ---in blasting, 46 ---in chalk, 8 flat chisels, 62 fleet street, well at, 193 formation, mineral character of, 11 foul air in wells, 52, 209 four and a half inch steining, 59 free-falling tools, dru's, 117-123 freshwater, well at, 187, 188 fulmer, well at, 193 fuse for blasting, 50 gases in wells, 52, 209 gault, 5 general conditions of outcrop, 18 geological conditions, epitome of, 10 ------primary, 4 gneiss, rainfall on, 27 golden lane, well at, 193 granite, rainfall on, 27 grapin, or clutch, 107 grapnels, 107, 139-141 gravesend, well at, 193 green lane wells, 160 greensands, 5, 8 greenwich, wells at, 193 grenelle, well at, 85, 179 guides, bore-head, 132 ----, dru's, for rods, 121 guncotton, 44 gunpowder, 44 ---weight of, 49 hackney road, well at, 193 haggerstone, well at, 194 hainault forest, well at, 194 half-brick steining, 59 halstead, well at, 194 hammersmith, well at, 194 hampstead, wells at, 194 ---road, wells at, 194 hand-dog, 65 hand-jumpers, 47 hanwell, well at, 194 hard rock, dru's system, 125 ------sinking in, 44, 53 harrow, well at, 171, 194 hastings sand, 5 haverstock hill, well at, 194 hayes, well at, 194 headings or tunnels, 53, 54 hedgerley, sands and clays at, 17 height of strata above surface, 23 hendon, well at, 194 herne bay, section at, 12 highbury, wells at, 172, 194 hills or mountains, 5 ---drift on, 6 ---flat-topped, 20 ---outcrop on, 19 hoddesdon, well at, 194 holloway, wells at, 194 hollow rods, 80 hoop-iron, boring with, 60, 61 horizontal strata, 9 hornsey, wells at, 194 horselydown, well at, 194 hoxton, well at, 195 hungerford, section near, 14 hyde park corner, well at, 195 hydraulic tube-forcers, 146-148 ickenham, well at, 195 instruments used in blasting, 46 iron cylinders for lining, 56 ---drum curb, 42 ---for drills and jumpers, 47 ---rods, 64, 65, 80, 120 ---tubbing, 95, 97, 98 isle of dogs, well at, 195 ---of grain, well at, 195 isleworth, wells at, 195 islington green, well at, 195 joints, kind-chaudron rod, 105-107 ---tubbing, 109 ---tube, 75, 143, 144 journal of well-work, 206 jumpers, 47, 48 kensington, wells at, 195 kentish town, well at, 172, 195 keuper, 5, 35, 36 key, kind-chaudron, 105 kilburn, well at, 195 kind-chaudron system, 93 kind's moss-joint, 123, 124 ---system, 85-93 kind's system, time employed, 92 kingsbury, well at, 195 kingston-on-thames, well at, 195 knightsbridge, well at, 195 ladle, cement, for tubbing, 111 lagging of drum curb, 42 lambeth, wells at, 195, 196 lancashire, thickness of trias, 36 lea bridge, well at, 196 leamington, well at, 158 least resistance, line of, 45, 46, 50 leatherhead, sands and clays at, 17 leek, wells at, 163 leicester square, well at, 196 lias, 5, 8 lifting dog, 65 lift of rods, 70 limehouse, wells at, 196 line of least resistance, 45, 46, 50 lining or steining wells, 54-59 ---tubes for bore-hole, 66, 143, 144 liquorpond street, well at, 196 lithofracteur, 44 liverpool, wells at, 158 london basin, wells in, 190-201 ---average section of strata, 13 ---clay, 5 ---measurement of sections, 15, 16 long acre, well at, 196 longton, wells at, 162 loughton, well at, 196 lower morden, well at, 196 ---tertiaries, outcrop of, 23 luton, well at, 196 magnesian limestone, 5, 10 maldon, well at, 196 margate, well at, 196 marylebone road, well at, 196 mather and platt's system, 126-154 measure of water in wells, 204 michelmersh, well at, 176 middlesborough, well at, 163 mile end, wells at, 176, 196 mile end road, well at, 197 millbank, wells at, 197 mineral character of formation, 11 mitcham, well at, 197 mizers, 56, 57 molasse sandstones, 5 monkey for tube well, 81 monkham park, well at, 197 mortlake, wells at, 197 moss box, kind-chaudron, 110, 111 moss joints, 110, 111, 123 mountain slopes, springs in, 6 mountains or hills, 5 muschelkalk, 35 new barnet, well at, 190 new cross, well at, 197 new red sandstone, 5, 8, 35 ------headings in, 54 new wimbledon, well at, 201 nine-inch steining, 59 north america, rainfall, 30, 31 northampton, well at, 166 northolt, well at, 197 norwich crag, 5 ---well at, 177 notting dale, well at, 197 ---hill, well at, 197 number of bricks in wells, 205 observations with rain-gauge, 24 off-take of rods, 70 old kent road, well at, 197 old windsor, wells at, 197 oolitic strata, 5, 8, 166 orange street, well at, 197 outcrop, 11 ---position of, 18 ---rainfall on, 11 ---rainfall on district, 24 oxford street, well at, 197 paris, wells at, 179 pass pipes for tubbing, 98 ---valves for tubbing, 98 passy, well at, 85, 180 pebble hill, section at, 14 ---beds, 36, 37 peckham, well at, 197 penge, well at, 197 pentonville, wells at, 197 permeability of new red sandstone, 37 permian strata, 155 picker, 58 pimlico, wells at, 197 pinner, well at, 197 pipe-dolly, 67 ---iron, 74 plaistow, well at, 197 planes of bedding, 12 plant, dru's system, 114, 115 ---kind-chaudron system, 99 ---well sinking, 40-58 ---well boring, 61-79 plug, tube straightening, 140, 149 plugs for tamping, 52 ponders end, wells at, 187, 197 porous soils, 8 position of outcrop, 18 ---of well, 207 pot mizer, 57 preparations for sinking, 40 pricker, 50 primary beds, 5, 9 principles of blasting, 45 prong grapnel, 139, 149 pudsey hall, well at, 198 pumps, mather and platt's, 149-154 quantity of brickwork in wells, 205 quicksand, modes of piercing, 98 rainfall, 24 ---on new red sandstone, 37 ---on outcrop, 11 ---tables of, 28-32 rain-gauge, instructions for using, 24 ratcliffe, wells at, 198 rate of boring, 207, 208 -------, dru, 123 ---of working, mather and platt's, 137 reculvers, section at, 12 regent's park, wells at, 198 rhætic beds, 5 richmond, wells at, 198 rimers, 68 riming spring, 68 ring for broken rods, 64 river deposits, 22 rock, chisels for, 62, 87, 102, 115, 132 ---intersected by dyke, 4 ---sinking in, 44 rod guides, dru's, 121 ---joints, dru's, 121 ---at passy, 86, 89 rods, boring, 64, 65 ---boring, dru's, 120, 121 ---kind-chaudron system, 101 ---remarks on, 126, 127 romford, well at, 198 rope, boring with, 60, 130 ross, well at, 165, 166 rotherhithe, wells at, 198 ruislip, well at, 198 running sands, dru's system, 125 saffron walden, well at, 198 st. helens, wells at, 166 sand, 11 ---mather and platt's system, 143 sandhurst, well at, 198 sandstone, new red, 35 sandwich, well at, 198 scaffolding for boring, 71 scratcher, 58 screw grapnel, 139, 142 screw-jacks, 144, 145 searching for water, 9 secondary beds, 5 setting rain-gauge, 24 shallow surface springs, 21 sheer-frame, boring, _frontispiece_, 72 sheer-legs, 69 sheerness, wells at, 198 shell, 63, 122 ---at passy, 90 ---kind-chaudron system, 105 ---or auger, 63 ---pump, mather and platt's, 134, 136 ------jammed, 141, 142 shoreditch, well at, 198 shorne meade fort, well at, 198 shortlands, well at, 199 shot-holes, boring, 48 ---in wet stone, 50 sinkers' bucket, 67, 150 sinking mine shafts, 93 ---plant for, 96 ---with drum curb, 42 sinkings in durham, 93 ---in hard rock, 44-53, 94 site for rain-gauge, 24 slate, rainfall on, 27 slope of hills, outcrop on, 19 slough, wells at, 199 small-shot system in blasting, 44 smithfield, well at, 199 snow, measuring fall of, 25 south america, rainfall, 31 southend, well at, 199 southwark, wells at, 199 speed of holing with hand-drills, 48 spitalfields, well at, 199 spithead, well at, 146 spring, definition, 1 ---cutter for tubes, 78, 79 ---darts, 67 ---pole, 61 springs, 1, 2 ---in alluvium, 7 ---in drift, 6 ---in chalk, 7 ---in permeable strata, 1 ---surface, 21 staffordshire, thickness of trias, 36 ---wells in, 162, 163 steam jet for ventilation, 52 steel for drills, 47 steining, 40, 43, 54-59 stemmer or tamping bar, 51 step-ladder, 139, 141 stifford, well at, 199 stockwell green, wells at, 199 stone steining, 55 storing well-water, 206 strata, disturbances of the, 32 ---table of, 202, 203 stratford, wells at, 199 stratified rock, blasting in, 46 streatham, well at, 199 stud-block, 66 sudbury, well at, 199 sulphuretted hydrogen in wells, 210 superficial area, extent of, 11 superintending well-work, hints on, 206 surface, height of strata above, 23 ---of outcrop, 11 ---springs, 21 swanage, dorset, well at, 167 tables of excavation in wells, 204 ---rainfall, 28-32 ---of strata, 202, 203 tamping, 50, 51 ---bar, 51 ---tools, 50-52 t-chisels, 62 tempering boring chisels, 209 tertiary beds, 5 ---district, division of, 34 testing machine, for tubbing, 108, 109 thames street, upper, well at, 200 tillers, 62, 65 timber steining, 55 tongs, 67 tools for well boring, 62-79 top rods, 65, 66 tottenham, wells at, 199 tottenham court road, well at, 199 tower hill, well at, 199 trafalgar square, well at, 199 trepan at passy, 85 ---dru's first, 113 ---kind-chaudron system, 101-105 ---kind's, 86, 87 trias strata, 35, 36, 155 tubbing, 94, 95 ---pass pipes for, 98 ---placing kind-chaudron, 108, 109 ---testing machine for, 108, 109 tube clamps, 67 ---forcing apparatus, 74, 144-148 ---grapnel, 139, 149 ---joints, 66, 75 ---well, american, 81 tubes, 66, 143 tubing, when necessary, 73 tunnels or headings, 53, 54 underpinning, 40 upchurch, wells at, 199, 200 upper thames street, well, at, 200 uxbridge, wells at, 200 valleys, drift in, 6 ---outcrop in, 18 valve for mizer, 56, 57 valves for shell, 64, 122, 123, 134 vauxhall, well at, 200 v-chisels, 62 wad-hook, 64 waltham abbey, well at, 200 walthamstow marsh, well at, 200 wandsworth, wells at, 200 warwickshire, thickness of trias, 36 water in new red sandstone, 38 ---measure and weight in wells, 204 ---searching for, 9 water-bearing deposits, value of, 10 ---strata, height of, above surface, 23 ------sinking through, 56, 93 well, artesian, definition, 2 ------causes of failure, 2-4 ---boring, 60-80 ---sinking, 40 well-water, storing, 206 wealden clay, 5 wedging cribs, 94, 95 weight of water in wells, 204 westbourne grove, well at, 200 west drayton, wells at, 200 west ham, wells at, 102 west india dock, well at, 201 westminster, wells at, 201 wet stone, shot-holes in, 50 whitechapel, wells at, 201 willesden, well at, 201 wimbledon, wells at, 201 windsor station well, 160 windsor, wells at, 201 ---wells at old, 197 winchfield, well at, 189 windlass, 42, 60, 72 winkfield plain, well at, 201 witham, well at, 201 withdrawing tools, 64 withdrawing tubes, 74-79 wolverhampton, wells at, 166 wooden drum curb, 41, 42 ---rods, 89, 101, 106 wood tubbing, 95 woodley lodge, well at, 201 woolwich beds, 5 ---wells at, 201 worm-auger, 64 wormley, wells at, 201 wormwood scrubbs, well at, 201 wrought-iron tubes, 66 london: printed by william clowes and sons, stamford street and charing cross. e. & f. n. spon's new books. crown 4to, cloth, 36_s._ _pyrology; or, fire chemistry._ a science interesting to the general philosopher, and an art of infinite importance to the chemist, mineralogist, metallurgist, geologist, agriculturist, engineer (mining, civil, and military), &c., &c. by william alexander ross, lately a major in the royal artillery. crown 8vo, cloth, 8_s._ _electricity: its theory, sources, and applications._ by john t. sprague, member of the society of telegraph engineers. with 91 woodcuts and 30 valuable tables. crown 4to, cloth, 15_s._ _the draughtsman's handbook of plan and 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architects' and builders' pocket-book of useful memoranda and prices for 1875._ by w. young, architect, author of 'picturesque architectural studies,' &c. crown 4to, cloth, 15_s._ _practical geometry and engineering drawing_. a course of descriptive geometry, adapted for the requirements of the engineering draughtsman, including the determination of cast shadows and isometric projection, each chapter being followed by numerous examples. to the above are added rules for shading, shade-lining, &c., together with practical instructions as to the lining, colouring, printing, and general treatment of engineering drawings. by george s. clarke, lieut. royal engineers, instructor in mechanical drawing, royal indian engineering college, coopers hill. third edition, 8vo, sewed, 1_s._ 6_d._ _the liverpool waterworks_. by charles m. beloe, m. inst. c.e., author of the 'construction of catch-water reservoirs.' crown 8vo, cloth, 7_s._ 6_d._ _dry rot_. a treatise on the origin, progress, prevention, 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(author of model houses), showing who are liable for dilapidations, and the extent of the liability of lessors, lessees, tenants at will, tenants by elegit, statute, merchant, or staple tenants in fee simple, tenants in tail, tenants for life, tenants for years without impeachment of waste, mortgagor, mortgagee in possession, yearly tenants, tenants in common, and joint tenants, rights of comparceners, also what are dilapidations and waste, and further fully instructs the surveyor how to take and value them, to which is added the duties of surveyors, with a table of legal cases, embracing the most recent, and illustrated throughout by examples drawn from the author's experience, and latest legal decisions, crown 8vo, cloth 5 0 =earthwork tables=. tables for computing the contents of earthwork in the cuttings and embankments of railways, by w. macgregor, royal 8vo, cloth 6 0 =economy in the use of steam=. a statement of the principles on which a saving of steam can be best effected, by frank salter, b.sc., crown 8vo 3 6 =electrical standards=. reports of the committee on electrical standards appointed by the british association, revised by sir w. thomsom, dr. j. p. joule, professors clark, maxwell, and fleeming jenkin, with a report to the royal society on units of electrical resistance, by prof. f. jenkin, edited by professor fleeming jenkin, f.r.s., _plates_, 8vo, cloth 9 0 =electric telegraph.= electrical tables and formulæ for the use of telegraph inspectors and operators, compiled by latimer clark and robert sabine, _with wood engravings_, crown 8vo, cloth 12 6 =engineering.= spons' dictionary of engineering, civil, mechanical, military, and naval, with technical terms in french, german, italian, and spanish, 3100 pp., and _nearly_ 8000 _engravings_, super-royal 8vo, in 8 divisions, cloth 13_s._ 6_d._ each £5 8 0 8 " half-morocco £6 8 0 8 " french morocco £7 4 0 complete in 3 vols., cloth £5 5 0 bound in a superior manner, half-morocco, top edge gilt, 3 vols. £6 12 0 =engineers' companion.= the office and cabin companion for engineers and officers of steam vessels, consisting of observations, rules, and tables to facilitate such calculations as naval officers and engineers are called upon to make, by j. simond holland, second edition, 12mo, cloth 3 0 =engineering drawing.= an elementary treatise on orthographic projection, being a new method of teaching the science of mechanical and engineering drawing, intended for the instruction of engineers, architects, builders, smiths, masons, and bricklayers, and for the use of schools, _with numerous illustrations on wood and steel_, by william binns, associate institute civil engineers, late master of the mechanical drawing class at the department of science and art, and at the school of mines, formerly professor of applied mechanics, at the college for civil engineers, etc., eighth edition, 8vo, cloth 9 0 _mr. binns' system of mechanical drawing is in successful operation in all the art schools of the united kingdom._ =engineering drawing.= the second course of orthographic projection; being a continuation of the new method of teaching the science of mechanical and engineering drawing; with some practical remarks on the teeth of wheels, the projection of shadows, principles of shading, and the practice of making to scale drawings from actual machinery. intended for the instruction of engineers, architects, builders, smiths, masons, and bricklayers, and for the use of science schools and classes, _with numerous illustrations_, by wm. binns, consulting engineer, associate i.c.e., late master of the mechanical drawing class, at the department of science and art, and at the royal school of mines; formerly professor of applied mechanics at the college for civil engineers, etc., 8vo, cloth 10 6 =engineers' pocket-book.= the pocket-book of pocket-books, being molesworth and hurst's pocket-books, printed on india paper, bound together in one volume, royal 32mo, russia, gilt edges 12 6 =engineers' pocket-book.= a pocket-book of useful formulæ and memoranda, for civil and mechanical engineers, by guilford l. molesworth, mem. ins. c.e., consulting engineer to the government of india for state railways, eighteenth edition, revised, with considerable additions by the author; together with a valuable contribution on telegraphs, by r. s. brough, 32mo, roan 6 0 ditto, interleaved with ruled paper for office use 9 0 ditto, printed on india paper, for the waistcoat pocket 6 0 =engineers' price-book.= appleby's illustrated handbook of machinery and iron work, with the cost, the working expenses, and the results obtained in the use of steam and hand cranes, pumps, fixed and portable steam engines, and various other machines; with weight measurement, etc., etc.; also prices of tools, iron works, stores and materials required by civil and mechanical engineers, merchants, and others; together with numerous tables and memoranda, by appleby bros., engineers, _many hundred wood engravings_, 8vo, cloth 12 6 =engineers' tables.= spons' tables and memoranda for engineers, selected and arranged by j. t. hurst, c.e., author of 'architectural surveyors' handbook,' 'hurst's tredgold's carpentry,' etc., 64mo, roan, gilt edges, second edition 1 0 or in cloth case 1 6 =french measures.= french measures and english equivalents, by john brook. for the use of engineers, manufacturers of iron, draughtsmen, etc., 18mo, roan 1 0 "in a series of compact tables the english values of the french measures are arranged from one to a thousand millimètres, and from one to a hundred mètres; the fractions of an inch progressing in sixteenths are also reduced to french values. the little book will be found useful to almost every engineer." --_engineering._ =french-polishing.= the french-polisher's manual, by a french-polisher, containing timber staining, washing, matching, improving, painting, imitations, directions for staining, sizing, embodying, smoothing, spirit varnishing, french-polishing, directions for re-polishing, royal 32mo, sewed 0 6 =gas.= analysis, technical valuation, purification and use of coal gas, by the rev. w. r. bowditch, m.a., _with wood engravings_, 8vo, cloth 12 6 =gas works.= instructions for the management of gas works, by w. c. holmes, engineer, 8vo, cloth 4 0 =gunner's pocket-book.= bridges' gunner's pocket-book, compiled by captain t. w. bridges, h.p. royal artillery, crown 32mo, roan, 1_s._; or morocco 1 6 =handrailing.= handrailing cut square to the plank, without a falling mould, as discovered and taught at the mechanics' institution, liverpool, by john jones, staircase builder, _containing seven plates, with full instructions for working them_, fol. boards 6 0 =hydraulics.= practical hydraulics: a series of rules and tables for the use of engineers, etc., etc., by thomas box, fourth edition, _numerous plates_, post 8vo, cloth 5 0 =iron.= iron as a material of construction, forming a handbook for the use of students in engineering, by william pole, c.e., f.r.s., _cuts_, post 8vo, cloth 6 0 =iron and steel.= the journal of the iron and steel institute, edited by jno. jones, f.g.s., and david forbes, f.r.s., published half-yearly, 8vo, each part 7 6 =indian engineering.= india and indian engineering: three lectures delivered at the royal engineer institute, chatham, in july, 1872, by julius george medley, lieut.-col. r.e., assoc. inst. c.e., fellow of the calcutta university, principal thomason civil engineering college, roorkee, crown 8vo, cloth 3 0 =link-motion.= link-motion and expansion-gear practically considered, by n. p. burgh, engineer, _illustrated with 90 plates and 229 wood engravings_, small 4to, handsomely half-bound in morocco £2 2 0 =mechanical engineering.= the mechanician and constructor for engineers, comprising forging, planing, lining, slotting, shaping, turning, screw-cutting, etc., by cameron knight, _illustrated by 96 4to plates, containing 1147 illustrations, and 397 pages of letterpress_, 4to, cloth £2 10 0 or, half-bound french morocco £2 12 6 =mechanics.= the essential elements of practical mechanics, based on the principle of work, designed for engineering students, by oliver byrne, formerly professor of mathematics, college for civil engineers, second edition, _illustrated by numerous wood engravings_, post 8vo, cloth 7 6 =mechanics.= the principles of mechanics and their application to prime movers, naval architecture, iron bridges, water supply, etc., by w. j. millar, c.e., secretary to the institution of civil engineers and shipbuilders, scotland, crown 8vo, cloth 4 6 =metric weights and measures.= scales for the ready comparison of british and metric weights and measures, by a. l. newdigate, m.a., in neat cloth case 5 0 =military terms.= a handy dictionary of military terms, by major w. w. knollys, f.r.g.s., 93rd sutherland highlanders, garrison instructor, home district, etc., 18mo, cloth 2 0 =mill gearing.= a practical treatise on mill gearing, wheels, shafts, riggers, etc., for the use of engineers, by thomas box, post 8vo, cloth, _with eight plates_ 5 0 =millwright's guide.= the practical millwright's and engineer's ready reckoner, or tables for finding the diameter and power of cog-wheels, diameter, weight and power of shafts, diameter and strength of bolts, etc., by thomas dixon, fourth edition, 12mo, cloth 3 0 =mine engineering.= a practical treatise on coal mining, by george g. andré, mining civil engineer, f.g.s., assoc. inst. c.e., _numerous plates_, 2 vols., royal 4to, cloth £3 12 0 =mining.= records of mining and metallurgy; or, facts and memoranda for the use of the mine agent and smelter, by j. arthur phillips and john darlington, in crown 8vo, cloth, _illustrated with wood engravings_ 4 0 =oilman's calculator.= the oilman's calculator, containing tables showing the conversion in imperial gallons of any weight of oil of a specific gravity of from ·700 to ·960, from 1 lb. to 400 cwt.; prices per gallon equivalent to prices per ton at 16 different weights, from £3 to £100; contents of circular tanks in imperial gallons from 3 feet to 36 feet diameter; conversion of foreign moneys and weights into british value, etc., by james ireland, 8vo 7 6 =pyrology.= pyrology, or fire chemistry; a science interesting to the general philosopher, and an art of infinite importance to the chemist, mineralogist, metallurgist, geologist, agriculturalist, engineer (mining, civil, and military), etc., etc., by william alexander ross, lately a major in the royal artillery, _with plates and woodcuts_, crown 4to, cloth £1 16 0 "a work which we have no hesitation in pronouncing original and invaluable. the author is not a chemist trained in the orthodox school outside which there is no salvation: for cooked results and unproved theories he shows very little respect. we can strongly recommend this book to analysts, assayers, mineralogists, and to all persons interested in mining and metallurgy."--_chemical news_, august 6th, 1875. =railway engineering.= manual of railway engineering, for the field and the office, by charles p. cotton, c.e., second edition, revised and enlarged, post 8vo, cloth 7 6 =rennie, sir john.= the autobiography of sir john rennie, past-president of the institution of civil engineers, f.r.s., etc., etc., edited by his son, c. g. c. rennie, _with portrait_, 8vo, cloth 12 6 =reservoirs.= on the construction of catch-water reservoirs in mountain districts for the supply of towns, or for other purposes, by c. h. beloe, author of 'the handbook of the liverpool waterworks,' _plates_, 8vo, cloth 5 0 =retaining walls.= surcharged and different forms of retaining walls, by j. s. tate, _cuts_, 8vo, sewed 2 0 =ropemaking.= a treatise on ropemaking as practised in public and private rope-yards, with a description of the manufacture, rules, tables of weights, etc., adapted to the trade, shipping, mining, railways, builders, etc., by r. chapman, formerly foreman to messrs. huddart and co., limehouse, and late master ropemaker to h.m. dockyard, deptford, second edition, 12mo, cloth 3 0 =sanitary engineering.= proceedings of the association of municipal and sanitary engineers and surveyors, vol. i., 1873-4, edited by lewis angell, mem. inst. c.e., f.r.i.b.a., etc., etc., 8vo, cloth 10 6 ditto, vol. ii. 7 6 =sanitary engineering.= a series of lectures given before the school of engineering, chatham. division i. air. division ii. water. division iii. the dwelling. division iv. the town and village. division v. the disposal of sewage. copiously illustrated. by j. bailey denton, c.e., f.g.s., honorary member of the agricultural societies of norway, sweden, and hanover, and author of the 'farm homesteads of england,' 'storage of water,' etc., etc., royal 8vo, cloth 21 0 =sanitary works abroad.= report of the commission appointed to propose measures for remedying the pollution of the seine; with a description of the works in course of execution for the sewerage of berlin, and the application of sewage to irrigation at marienfelder and falkenburg. translated from the french by robert manning, m. inst. c.e., chief engineer to her majesty's board of public works in ireland, 8vo, sewed 2 0 =sewage.= a handbook of sewage utilization, by ulick ralph burke, esq., barrister-at-law, crown 8vo, cloth 3 6 this work treats: i. of the evils of the present system of sewage treatment, the pollution of water, and the waste of manure. ii. remedies, privy, and ash-pit; eureka system; milan, goul, and moule's systems. iii. treatment of sewage by chemical means; experiments with lime; lime and chloride of iron; sulphate of ammonia; holden's process; sulphate of alumina; persalts of iron; blyth, lenk, phospate, a.b.c., scott, and hille processes; filtration. iv. irrigation. with an appendix, including the law relating to sewage utilization. =sewage.= the sewage question on the treatment and utilization of sewage, the preparation of land for irrigation, and for intermittent downward filtration, by j. bailey denton, mem. inst. c.e., f.g.s., 8vo, sewed 2 0 =silver mines.= vazeeri rupi, the silver country of the vazeers, in kulu: its beauties, antiquities, and silver mines, including a trip over the lower himalayah range and glaciers, by j. calvert, f.g.s., mem. inst. c.e., _illustrated with a map and coloured plates_, 8vo, cloth 16 0 =slide valve.= the slide valve practically considered, by n. p. burgh, engineer, seventh edition, _containing 88 illustrations and 121 pages of letterpress_, crown 8vo, cloth 5 0 =slide valve. designing valve gearing.= a treatise on a practical method of designing slide valve gearing, by simple geometrical construction, based upon the principles enunciated in euclid's elements, and comprising the various forms of plain slide valve and expansion gearing; together with stephenson's, gooch's, and allan's link-motions, as applied either to reversing or to variable expansion combinations, by edward j. cowling welch, memb. inst. mechanical engineers, crown 8vo, cloth 6 0 the system described in this work enables any draughtsmen or foreman to "get out" in a _few minutes_, and with the greatest precision, all the details of a slide valve gear, without recourse to models or other similar appliances. =steam boilers.= practical treatise on steam boilers and boiler-making, by n. p. burgh, mem. inst. mec. eng., _illustrated by 1163 wood engravings and 50 large folding plates of working drawings_, royal 4to, half-morocco £3 13 6 =steam engine.= modern marine engineering applied to paddle and screw propulsion; consisting of _36 plates, 259 wood engravings_, and 403 pages of descriptive matter, the whole being an exposition of the present practice of the following firms: messrs. j. penn and sons; maudslay, sons, and field; james watt and co.; j. and g. rennie; r. napier and sons; j. and w. dudgeon; ravenhill and hodgson; humphreys and tenant; mr. j. f. spencer; and messrs. forester and co. by n. p. burgh, engineer, 4to, cloth £2 5 0 =steam engine.= modern compound engines, being a supplement to modern marine engineering, by n. p. burgh, mem. inst. mech. eng., _numerous large plates of working drawings_, 4to, cloth 18 0 the following firms have contributed working drawings of their best and most modern examples of engines fitted in the royal and mercantile navies: messrs. maudslay, rennie, watt, dudgeon, humphreys, ravenhill, jackson, perkins, napier, elder, laird, day, allibon. =steam engine.= practical treatise on the condensation of steam: contained in 262 pages of letterpress, _and illustrated with 212 engravings_, by n. p. burgh, engineer, super-royal 8vo, cloth £1 5 0 =steam engine.= a pocket-book of practical rules for the proportions of modern engines and boilers for land and marine purposes, by n. p. burgh, fifth edition, revised, with appendix, royal 32mo, roan 4 6 details of high-pressure engine, beam engine, condensing, marine screw engines, oscillating engines, valves, etc., land and marine boilers, proportions of engines produced by the rules, proportions of boilers, etc. =steep gradients on railways.= a treatise on the improved method for overcoming steep gradients on railways, whereby an ordinary locomotive capable of hauling a given load up a gradient 1 in 80, can take the same up 1 in 8, by henry handyside, 8vo, sewed 1 0 =strength of beams.= on the strength of beams, columns, and arches, considered with a view to deriving methods of ascertaining the practical strength of any given section of beam, column, or arch, in cast-iron, wrought-iron, or steel, by b. baker, _numerous cuts_, crown 8vo, cloth 9 0 =strength of beams.= new formulas for the loads and deflections of solid beams and girders, by william donaldson, m.a., assoc. inst. c.e., 8vo, cloth 4 6 =sugar.= the practical sugar planter; a complete account of the cultivation and manufacture of the sugar-cane, according to the latest and most improved processes, describing and comparing the different systems pursued in the east and west indies, and the straits of malacca, and the relative expenses and advantages attendant upon each, being the result of sixteen years' experience of a sugar planter in those countries, by leonard wray, esq., _with numerous illustrations_, 8vo, cloth 10 6 =short logarithms.= short logarithmic and other tables, intended to facilitate practical calculation, and for solving arithmetical problems in class, by professor w. c. unwin, 8vo, cloth 2 0 =sulphuric acid.= the chemistry of sulphuric acid manufacture, by henry arthur smith, _cuts_, crown 8vo, cloth 4 6 =surveying.= the principles and practice of engineering, trigonometrical, subterraneous, and marine surveying, by charles bourne, c.e., third edition, _numerous plates and woodcuts_, 8vo, cloth 5 0 =surveying.= a practical treatise on the science of land and engineering surveying, levelling, estimating quantities, etc., with a general description of the several instruments required for surveying, levelling, plotting, etc., by h. s. merrett, _41 fine plates, with illustrations and tables_, royal 8vo, cloth, second edition 12 6 =table of logarithms.= table of logarithms of the natural numbers, from 1 to 108,000, by charles babbage, esq., m.a., stereotyped edition, royal 8vo, cloth 7 6 =tables of squares and cubes.= barlow's tables of squares, cubes, square roots, cube roots, reciprocals of all integer numbers up to 10,000, post 8vo, cloth 6 0 =teeth of wheels.= camus (m.) treatise on the teeth of wheels, demonstrating the best forms which can be given to them for the purposes of machinery, such as mill-work and clock-work, and the art of finding their numbers, translated from the french, third edition, carefully revised and enlarged, with details of the present practice of millwrights, engine makers, and other machinists, by isaac hawkins, _illustrated by 18 plates_, 8vo, cloth 5 0 =telegraphy.= journal of the society of telegraph engineers, including original communications on telegraphy and electrical science, edited by major frank bolton and g. e. preece, parts i. to xii., demy 8vo, sewed, _with wood engravings_, each 5 0 _to be continued quarterly._ =torpedo warfare.= a treatise on coast defence; based on the experience gained by officers of the corps of engineers of the army of the confederate states, and compiled from official reports of officers of the navy of the united states, made during the north american war from 1861 to 1865, by von scheliha, lieutenant-colonel and chief engineer of the department of the gulf of mexico, of the army of the late confederate states of america; _with numerous fine plates_, imperial 8vo, cloth, top edge gilt 15 0 =trevithick.= the life of richard trevithick (inventor of the high-pressure steam-engine), with an account of his inventions, by francis trevithick, c.e., 2 vols., medium 8vo, cloth, _illustrated by a steel portrait, lithographs, and numerous beautiful wood engravings, including many accurate illustrations of cornwall, its mines, and mining machinery_, reduced to 12 6 =turbine.= a practical treatise on the construction of horizontal and vertical waterwheels, _with 11 plates_, specially designed for the use of operative mechanics, by william cullen, millwright and engineer, second edition, revised and enlarged, small 4to, cloth 12 6 =turning.= the practice of hand-turning in wood, ivory, shell, etc., with instructions for turning such work in metal as may be required in the practice of turning in wood, ivory, etc.; also an appendix on ornamental turning, by francis campin, second edition, _with wood engravings_, crown 8vo, cloth (a book for beginners) 6 0 =valve-gears.= treatise on valve-gears, with special consideration of the link-motions of locomotive engines, by dr. gustav zeuner, third edition, revised and enlarged, translated from the german, with the special permission of the author, by moritz müller, _plates_, 8vo, cloth 12 6 =ventilation.= health and comfort in house building, or ventilation with warm air by self-acting suction powder, with review of the mode of calculating the draught in hot-air flues, and with some actual experiments, by j. drysdale, m.d., and j. w. hayward, m.d., second edition, with supplement, demy 8vo, _with plates_, cloth 7 6 the supplement separate 0 6 =weight of iron.= tabulated weights of angle, t, bulb, and flat iron, for the use of naval architects and shipbuilders, by charles h. jordan, m.i.n.a., 18mo, sewed, second edition 1 6 =wood-working factories.= on the arrangement, care, and operation of wood-working factories and machinery, forming a complete operators' handbook, by j. richards, mechanical engineer, _woodcuts_, crown 8vo, cloth 5 0 =wood-working machines.= a treatise on the construction and operation of wood-working machines, including a history of the origin and progress and manufacture of wood-working machinery, by j. richards, mechanical engineer, _25 folding plates and nearly 100 full-page illustrations_ of english, french, and american wood-working machines in modern use, selected from the designs of prominent engineers, 4to, cloth £1 5 0 =workshop receipts.= workshop receipts for the use of manufacturers, machinists, and scientific amateurs, by ernest spon, crown 8vo, cloth 5 0 royal 8vo, cloth, 7_s._ 6_d._ _spons' engineers' and contractors' illustrated book of prices of machines, tools, ironwork, and contractors' material._ e. & f. n. spon: london and new york * * * * * * transcriber's note: a table of contents was added for the convenience of the reader. hyphenation has been made consistent except where the meaning would be affected. metre and centimetre changed to mètre and centimètre for consistency; all other accentuation unchanged. original spelling has been retained with the exception of 'guage,' which has been changed to 'gauge;' parimaribo changed to paramaribo; filteration changed to filtration; homogenous changed to homogeneous. suction 'powder' appears to be a misprint for 'power' and has not been changed. some illustrations are not referenced in the text and have no title, e.g. fig. 10. descriptive titles were added by transcriber where needed in the plain text version only. 'p. s. reed' is mentioned in several places and is probably a misprint for 'reid'; see neimme library. h. s. merritt changed to h. s. merrett. 