The first large aqueduct in the U

S. was that completed 1841 for supplying N. Y. from the Croton River. It was 40 m. long, of a horseshoe form, 74 ft. wide by 8t ft. high, cost $8,600,000, and supplied 60,000,000 gals. per day. This is still in use, cro ing the Harlem River over High Bridge. In 1890 a second Croton aqueduct was completed, 33 m. long and ab. 12 ft. in diameter; it cro es the Harlem River by an inverted siphon in a tunnel, and has a capacity of 320,000,000 gals. per day. Washington, Baltimore, Boston, and other cities obtain their water supply through aqueducts or tunnels which have been constructed at great expense. The amount of water furnished by an aqueduct depends not only on its size, but upon its slope or grade. The slope is usually such that the mean velocity of the water is 2 or 3 ft. per second. A steel pipe 48 inches in diameter and 21 m. long was built in 1892 for the supply of Newark, N. J.