The water is conveyed across this valley by means of iron pipes. Agate chamber is placed on each side, by which a connection is formed between the conduit of masonry and the iron pipes, and gates prepared for regulating the flow of water in the same manner as before described for Harlem River. The width of the valley is 0.7917 miles from gate chamber to gate chamber, and the depth at which the pipes are laid in the centre is 102 feet. Two cast iron pipes, each three feet in diameter, are laid down, and provision made for two more, to be laid when they shall be required for the wants of the city. In order to give the pipes sufficient capacity to discharge the quantity of water required, an extra head of three feet is given in crossing the valley.

CLENDENING BRIDGE This bridge is constructed over a valley of the same name, that is situated about equally distant between Manhattan valley and the receiving reservoir. The greatest depression is 50 feet, below top of aqueduct, and the valley is 1900 feet across. The line of aqueduct runs 100 feet westerly of, and parallel to, the 9th Avenue. In the plan of the city, streets are laid out, but not yet opened, that cross the aqueduct at right angles. For three of the streets archways are constructed under the aqueduct for their accommodation when they may be opened for use. The archways for each street are, one for carriage-way of 30 feet span, and an arch on each side for side walks of 10j feet span. The style of masonry is similar to that before described for the Sing Sing bridge, and the same method of open walls arid cast iron lining is also adopted. That part of the bridge which has no provision for street arches, is composed of a continuous wall of masonry, carried up on a bevel of one-twelfth its rise to the line of the aquegrade duct, where it is 30 feet wide the outside or face of this wall for one foot in breadth, is ;