Page:The American Cyclopædia (1879) Volume I.djvu/650

614 AQUEDUCT including $1,800,000 for distributing pipes, and amounts paid for right of way and other incidental charges, was $10,375,000. Includ- ing commissions and interest, the whole cost was $12,500,000. The whole length, from its source at Croton river to the distributing reser- voir on 5th avenue and 40th street, is 40| m. On this line are 16 tunnels having an aggregate length of 6,841 ft., and cut mainly through gneiss rock. A large part of the open cutting is also rock work. A dam constructed across the Croton river raised the water 40 feet, and formed the Croton lake, which covers about 400 acres. This is the collecting reservoir, and contains with a depth of 6 ft. of water 500,000,- 000 gallons. A new collecting reservoir is (1873) in course of construction at Boyd's Cor- ners, Putnam county, to be formed by building across the west branch of the Croton river a dam 700 ft. long and of sufficient height to se- cure a storage capacity of 3,000,000,000 gal- lons, flooding over 800 acres of land. From Rock Tunnel Main Aqueduct the dam to the Harlem river, nearly 33 m., the aqueduct is built of stone, brick, and cement, arched over and under, 6 ft. 9 in. wide at the bottom (this being the chord of an arc, the versed sine of which is 9 in.), 7 ft. 5 in. at the springing line of the arch, and 8 ft. 5| in. high; area of cross section, 53^ sq. ft. In rock tunnels the roofing arch is dispensed with, though the bottom and sides are as here de- scribed and illustrated. Its capacity is equal to 115,000,000 gallons daily. The inclination is 1-1088 ft. per mile, or 33*92 ft. in the 33 m. The velocity of the water is H m. an hour. Across Harlem river the aqueduct is carried 'upon the High bridge in two cast-iron pipes of 3 ft. diameter, and one wrought-iron pipe 7 ft. 6 in. in diameter, recently laid over the former. The lower pipes are 12-29 ft. lower than the bottom of the conduit on the N. side of the river, and 10 ft. below the aqueduct on the S. side. While the bridge was building, the water was conveyed in a 3-foot iron pipe down one bank of the river and up the other, and the original intention was to have had this for the permanent plan. Objections being raised that the pipe would obstruct the navi- gation of the river, and restrictions being im- posed by the state legislature as to its use, it was finally decided to build a bridge with arches 80 ft. wide and openings 100 ft. high, to admit the passage of vessels. The bridge, as now completed, is 1,460 ft. long, with 8 arches in the river of the required span, and 7 others on the banks of 50 ft. span. The whole height of the bridge above high- water mark is 116 ft. There are two receiving reservoirs in the Central Park, known as the old and the new. The former covers an area of 35 acres and has a capacity of 150,000,000 gallons; the latter 100 acres, with a capacity of 1,030,000,000 gallons.. From these reservoirs to the distributing res- ervoir, a distance of 2J m., or directly into the city, the water is conveyed in two lines of iron pipe 80 in., two lines 36 in., and one line 48 in. in High Bridge, Harlem River.