Water Works, constructions for the purpose of collecting, conveying, and distributing water. They may be designed for supplying cities, single buildings, or mills, or for drainage or irrigation, and also for the purposes of navigation; and they were employed in the earliest times for all these purposes. (See Aqueduct.) In this article only those works will be considered by which cities are supplied with water. The construction of such works includes the consideration of the source of supply, its conveyance into reservoirs, and its distribution from these to the points of consumption. The supply is usually collected from springs or streams by means of dams which form reservoirs. The condition of the valley as to soil and its cultivation, and also that of the water respecting the amount of mineral and vegetable matter which it contains, should receive careful consideration. For the construction of the dam for collecting the water, see Dam. Such a reservoir formed in the stream is called a collecting reservoir, and usually empties into a second through an aqueduct; and this, called a receiving or storage reservoir, may flow into a third or distributing reservoir, or the receiving may also be a distributing reservoir.

A succession of reservoirs generally aids in the purification of the water by facilitating deposition of sediment, or by filtration. - There are three principal systems of supplying water to towns: 1, the reservoir system; 2, the stand-pipe system; 3, the Holly system. The two first are sometimes classed under one, called the gravity system; the Holly is an artificial power system. The first system was the only one employed by the ancients; but in their aqueducts they neglected the principle of hydraulic pressure, constructing them with a continuous descending grade. Reservoirs are constructed, according to their situation and service, with earth embankments and puddled bottoms and sides, or of solid masonry of stone or brick and hydraulic cement, and the latter are sometimes surrounded with earth embankments. In constructing the walls, the engineer takes into consideration the degree of hydraulic pressure to which they are to be subjected and the nature of the material of which they are constructed, and also the liability of such material to become weakened or strengthened by time, always bearing in mind the hydrostatic law that the pressure of fluids against equal lateral surfaces increases from the top downward as the odd numbers 1, 3, 5, 7, etc, and also the practical rule that the walls of such structures should be able to withstand a much greater pressure than is likely to be brought to bear against them.

In order to have the service pipes in a city freely deliver their water at all points, the surface of the water in the distributing reservoir should be considerably above the level of any of the service pipes, as the retardation of the flow and the decrease in pressure produced by the numerous discharging orifices at various levels will prevent the delivery of water in such pipes at the same level. The water is usually carried from the distributing reservoir in large mains, which are sometimes made of cement, but usually of cast iron; these mains run through the principal streets, and from them distributing pipes are carried through the different streets and are tapped by the service pipes of the several buildings. The distributing pipes are usually of iron, and in some cases also the service pipes; but the latter are generally of lead or of lead lined with tin. The reservoir system has a good and perhaps its best example in the supply of Croton water to the city of New York. Supplementary to the main system, there is a small reservoir in a tower at the High bridge, into which the Croton water is forced by two large pumping engines, for supplying the higher portions of the city adjacent.

Boston is also admirably supplied by* this system from Cochituate lake. - The standpipe system is not much used, especially in cold climates, as the water is liable to freeze in the stand pipe; but it may be employed with advantage in localities where the thermometer rarely falls below the freezing point. The system comprises a dam for the collection of water, or a large well or several wells from which the water is pumped either by steam or water power into a tall tower, usually constructed of iron, which is called a stand pipe.

This stand pipe is in fact a small reservoir, which requires to be constantly supplied in order to maintain the necessary pressure in the mains and distributing pipes; and that system which employs only a very small reservoir needing constant supply is only another form of the stand-pipe system, with the advantage of having a body of water even in its small reservoir which is not liable to be frozen. In all systems of water works it is of the greatest importance, not only on account of economy and convenience, but also of the more important subject of health, that the supply pipes to their discharging orifices should be constantly filled with water, and that they should not, as unfortunately they often do, contain air in consequence of insufficient hydrostatic pressure, so that the inner surface of the pipes becomes corroded with soluble oxides and salts derived from the material of the pipes, the oxygen of the air and of the water, and other matters. The city of Brooklyn is supplied with water from an extensive rainfall drainage basin comprising about 60 sq. m. on Long Island. The upper side of this basin begins in the range of hills on the north side of the island, the water being carried through extensive and deep beds of gravel and sand toward the southerly shore of the island, where it is discharged into natural arid artificial collecting reservoirs.

These are: Jamaica pond, 5½ m. distant from the pump well, with an area of 40 acres, a storage capacity of over 6,000,000 gallons, and a daily supply capacity of over 3,000,000; the Brookfield reservoir, 8 m. from the pump well, with an area of 8¾ acres, a storage capacity of 15,500,000 gallons, and a minimum flow of nearly 2,000,000 gallons daily; Clear Stream pond, 8| m. from the pump well, with a storage capacity of 800,000 gallons and a daily flow 750,000 gallons; Valley Stream pond, nearly 10 m. from the pump well, with an area of 17§ acres, a storage capacity of nearly 19,000,000 gallons, and a minimum flow of 2,433,000; Rockville pond, about 12 m. from the pump well, with a storage capacity of over 3,000,000 gallons, and a minimum daily flow of over 2,500,000; Hempstead pond, about 12-½- m. from the pump well, having an area of 23½ acres and a storage capacity of over 5,000,000 gallons; also Willet's and Smart's ponds, and Freeport creek, with a daily flow of 5,000,000 gallons; and One-mile pond, at the head waters of Jamaica stream. The quantity which may be supplied annually is therefore estimated in the neighborhood of 19,000,000,000 gallons.

The consumption of the water in the city in 1872 was about 8,000,000,000 gallons, so that ten or eleven millions of gallons flowed over the weirs during the year. Beginning at Hempstead, a closed conduit of masonry, 8 ft. 2 in. wide, conveys the water with a descent of 6-1/3in. per mile to Rockville, where the conduit is increased to 8 ft. 8 in. in width, at Valley stream to 9 ft. 2 in., at Clear stream to 9 ft. 4 in., and at Brookfield branch to 9 ft. 8 in., while from Jamaica pond to the pump well the width is 10 ft., and the descent 6 in. per mile. This portion of the conduit is capable of delivering, with 32 in. depth of water, 20,000,000, and with a depth of 5 ft. 47,000,000 gallons of water in 24 hours. A portion of the conduit rests upon pile foundations, and it is supported all the way by a bed of concrete 15 ft. wide. The bottom is an inverted arch of brick 4 in. thick, with a versed sine of 8 in. The top is a brick arch 12 in. thick, the height from the centre being 8 ft. 8 in. At convenient points along the line there are man holes, at the top or on the side, affording access for inspection or repairs. On this lower reach, between Jamaica and the pump well, the sides are of stone, 3 ft. high, with a lining of brickwork. Above this the brickwork is omitted.

For nearly the whole length the aqueduct is covered with 4 ft. of earth, sloping from 1 perpendicular to 1½ and 2 horizontal. At the pump well the aqueduct terminates in an arched basin 52½ ft. long, at right angles to its course, and connecting with the pump well by four sluices. The total length of the aqueduct is 12.39 m., 7½ m. of which is 10 ft. wide and 8 ft. high. The pump well is of heavy granite masonry laid in hydraulic cement. The bottom, 2 ft. below that of the aqueduct, rests upon a bed of concrete, which in turn rests upon a heavy platform of timber. From this well the pumping engines raise the water 164 vertical feet into the Ridge wood reservoir. These engines are three in number, two beam and one crank engine, their united capacity being about 32,000,000 gallons in 24 hours. The reservoir is in two divisions, one having an area of 11.85 and the other 13.73 acres; the water surface when filled to a depth of 20. ft. being 170 ft. above high-water mark. The embankments contain puddle walls carried 2 ft. higher than the level to which the reservoir is filled, and the bottom is also puddled with clay. The inner slopes are paved with broken bowlder stone upon a bed of stone chips and gravel.

The water flows into the reservoir from bellshaped mouths of the force mains into an influx chamber of heavy stone masonry, and from these over an apron into each compartment of the reservoir. In traversing a distance of 1,200 ft. in the reservoir most of the sediment is deposited. The effluent chamber, also of massive stone masonry, has four sluice ways, and is separated from the stopcock chamber by a heavy stone wall 6 ft. thick, from which issue three mains, each 36 in. in diameter. Before entering the effluent chamber, the water passes through screens of copper wire. The total capacity of the reservoir is 161,090,444 gallons. At Mt. Prospect there is a reservoir with a capacity of 20,000,000 gallons for the supply of the higher portions of the city, which is filled by a pumping engine having a capacity of 112 gallons at each stroke. The force main has a 20-inch branch connecting with the effluent main, which may be used when the reservoir needs cleaning or repair, in which case the 20inch main leading up to the influent chamber would act as a retard pipe to regulate the flow. The city of Philadelphia is supplied with water from the Schuylkill river by the Fairmount water works.

The original' works at Fairmount, driven by steam power, were commenced Aug. 1, 1812, to take the place of works which were in operation at Chestnut and Broad streets, and which were also worked by steam power. The Fairmount works were put in operation Sept. 7, 1815. At the foot of Fairmount hill there was erected a Boulton and Watt engine of 44 in. cylinder and 6 ft. stroke, working a double-acting pump of 20 in. diameter and 6 ft. stroke, raising the water through a 16-inch main 239 ft. long into a reservoir 102 ft. above low water in the Schuylkill river. Measures were taken in 1819 to use water power, and a dam was constructed across the • Schuylkill, which was completed July 28, 1821.. This dam, 1,600 ft. long, of hemlock, was rebuilt in 1842-'3 from low tide with white pine. The building of the present new dam was commenced in June, 1872, in front of the old one, upon a rock at the west end, and upon cribs at the east end. The breadth of overflow is 1,112 ft. The first wheel, a breast wheel, was put in operation July 1, 1822, and the ninth, a turbine, Dec. 16, 1851. The total quantity of water pumped in 1852 was 2,092,086,692 gallons. In 1866, 1867, and 1868, the daily average pumping was nearly 22,000,000 gallons.

Since then more than $600,000 have been expended in constructing the new dam, new wheel house, and three new turbines, but the daily average supply has never equalled 25,000,000 gallons, which demonstrates the fact that the system is not as economical as that which employs steam power. The pumpage during 1875 was 7,670,009,198 gallons, a daily average of 21,013,724. The other works which supply Philadelphia with water employ steam engines, except the syphon, which takes the water from the Wissahickon and empties it into a basin at Mt. Airy. The capacity of the Spring Garden works is 22,000,000 gallons daily. On May 10,1876, at the opening of the centennial exhibition, a new engine of 20,000,000 gallons capacity was put in operation. There are also the Delaware, Belmont, Roxborough, Chestnut Hill, and Frankford works. - The third system of water works, called the Holly system, owes one of its principal advantages to the fact that it is the best possible system for extinguishing fires, and also for keeping all the supply pipes constantly filled and maintaining a nearly equable pressure in them. It may employ steam or water as a power, and with a sufficient reserve force to allow of 100 lbs. or more to a square inch to be brought against the water in the pipes.

The city of Rochester, N. Y., is supplied by the Holly system, having a dual arrangement: 1. Water is pumped from the Genesee river by a steam engine, which throws it directly into the supply pipes. The machinery runs constantly, ordinarily with the pressure of about 60 lbs. to a square inch; but in case of fire the pressure may be increased to 100 lbs. or more. There is an automatic contrivance by which the speed of the engine is reduced in proportion to the reduction of discharge in the supply pipes, and vice versa. 2. Water is brought through iron pipes from Hemlock lake, 28 m. distant. There are two reservoirs, a storage and a distributing one. The former is 10 m. from the city, and has a capacity of 85,000,000 gallons; the latter is 1| m. from the centre of the city, and has a capacity of about 30,000,000 gallons. Hemlock lake has an elevation of 388 ft. above the city, the storage reservoir 24:6 ft., and the distributing reservoir 127 ft. The reservoirs are so arranged that they may be disconnected with the supply, and this immediately connected with the lake.

The first trial of the works was made on Feb. 18, 1874, with the following results: 14 one-inch vertical streams from different hydrants were thrown simultaneously to a height of 130 to 150 ft., then 20, and afterward 30 streams of the same size, the latter test involving the discharge of 8,220 gallons a minute; a two-inch stream was then thrown vertically 220 ft., and then a four-inch stream 465 ft. horizontally; next a three-inch stream was thrown over 285 ft. vertically; afterward a four-inch stream was thrown 297½ ft. vertically; and finally a five-inch stream was thrown to a height of 250½ ft. Long Island City and the villages of Flushing and College Point are also supplied with water by the Holly system, and it has been or is to be introduced into numerous towns in various parts of the country.