Page:The American Cyclopædia (1879) Volume I.djvu/651

 AQUEDUCT 015 diameter. The capacity of this distributing reservoir is 20,000,000 gallons. It is a stone structure 45 ft. high above the streets, and 425 ft. square at the top, covering a little more than four acres. The higher sections of the island lying north of Manhattan valley are supplied from a reservoir and tower lately erected on the high ground near 173d street, between 10th avenue and the aqueduct. The water for the supply of this high service res- ervoir and the adjacent tower tank is fur- nished by two pumping engines stationed near the lower end of the high bridge. (See WA- TER WORKS.) In 1871 the average daily de- mand was 85,000,000 gallons, which is taken mainly from the distributing reservoir and conveyed through the city in 340 m. of iron pipe ranging in diameter from 4 ft. to 4 in. The cities of Brooklyn and Jersey City re- ceive their water supply, the former from sev- eral ponds from 8 to 14 m. distant, and the latter from the Passaic river, 8 m. distant. In both cases the water enters the city upon such a level as to require the use of pumping engines for its distribution. For the plan and capacity of these engines, as also of those in operation at the famous Fairmount water works, Phil- adelphia, see WATER WORKS. The aqueduct which supplies the city of Boston leads from Cochituate lake to the receiving reservoir at Brookline, a distance of 14 m. For the greater part of the way it is a conduit of brick mason- ry. Over the valley of Charles river is a line of iron mains, and in Newton and Brookline are two tunnels. The brick conduit winds by ir- regular curves along the country, and is of such an elevation as admits of the work being most- ly beneath the natural surface. The brick- work is 8 in. thick, laid in hydraulic ce- ment, the section of the conduit being that of an egg, the larger end down. The greatest Cochituate Aqueduct. width is 5 ft. and the extreme internal height 6 ft. 4 in. This aqueduct is everywhere cov- ered by at least 4 ft. of earth, and nowhere ad- mits of a passage underneath, except by cul- verts at the crossing of Charles river and at a bridge over a valley in Needham. The two 30-inch iron pipes cross the river upon a stone bridge at a level 71 ft. above low-water mark. The whole length of each pipe is 979 ft. The tunnels are in porphyritic rock of great hardness, one 2,410 and the other 1,150 ft. in length. The city of Washington is sup- plied with water through an aqueduct con- structed by the national government, 18 m. long, leading from the Potomac falls to the receiving reservoir at Chain Bridge. On the line of this work are 11 tunnels and 6 bridges; the chief of these, over Cabin John creek, is a stone structure 100 ft. high and having a single span of 220 ft. The whole cost of the work exceeded $3,000,000. The Chicago lake tunnel, through which the waters of Lake Michigan are led into that city, was commenced March 17, 1864, and completed under the supervision of city engineer E. F. Chesborough, March 8, 1867. (See TUNNEL.) Though the Croton aqueduct is at present the greatest work of its kind in the United States, others have been projected which, if brought to successful com- pletion, will far surpass it. Among these is the plan of supplying the city of San Francisco from Lake Tahoe, a mountain reservoir of great depth and purity, located upon the boundary line between California and Nevada, and dis- tant from San Francisco about 150 m. It is also now proposed to construct an aqueduct from Lake George to the city of New York, a distance of over 200 m., the conduit to be of sufficient size to supply the many cities and villages along the route. In addition to the structures mentioned above, there are nu- merous bridges designed for the conveyance of canals across rivers and valleys. The first of these canal aqueducts built in England was constructed by the architect Brindley, under the supervision of the duke of Bridgewater. Upon it the Lancaster canal crossed the river Lune. It was composed of 5 arches of 72 ft. span each, with an average height of 65 ft. above the level of the river. The Forth and Clyde canal crosses the valley of Kelvin upon an arcade somewhat higher, though of not so great length as that across the Lune. The Pont-y-Cysyllte aqueduct conveys the waters of the Ellesmere canal across the vale of Llan- gollen in Wales. This bridge is 1,000 ft. long, built with 19 arches, each having a span of 45 ft. The canal level is 126 ft. above that of the river below. In the United States there are many structures of this character, those on the Erie canal alone numbering 32. The chief of these are the two crossing the Mohawk river, the Richmond aqueduct over the Seneca river, and the stone arcade across the Genesee at Rochester. The larger of the two Mohawk bridges, crossing the river at a point 14 m. N. W. of Albany, consists of a wooden trunk resting upon 29 stone piers ; it is 1,800 ft. long, and cost $331,000. The Richmond aqueduct is a beau- tiful stone structure 894^ ft. long, the water being also conveyed in a wooden trunk. For beauty and strength, however, the aqueduct bridge across the Genesee river at Rochester deserves special mention. It is a solid stone structure 920 ft. long, supported upon 6 cut stone arches of 52 ft. span. It is in the centre of the city, and was erected at a cost to the