them will probably require bearing piles to support them, and rock is expected to be found for the other. The coffer dams are all put down and embanked, and the work of emptying them is soon to commence. A temporary pipe 3 feet in diameter is laid down, (partly on the embankment of the coffer dams,) which now conveys the water across this valley. Gate chambers are arranged at each end of the bridge, with gates to regulate the

CROTON AdUEDUCt:

water, and the one on the north end has a waste weir to discharge the surplus water {hat at any time the pipes might not be able to carry. The bridge is to be constructed of well dressed granite. It may very properly be inquired, if the water can be carried temporarily across this valley by iron pipes, why construct this expensive bridge ? The reply is, that a plan was prepared, and the work put under contract, to construct a low bridge with one arch for water way but a supposed value which was attached to the future navigation of the ;

river, was so pressed upon the Legislature, as to induce them to pass a law, requiring that the under side of the arches should be 100 feet above ordinary high tide in the river. The law, therefore, and not the otherwise necessity of the case, has controlled the plan for crossing this valley.

MANHATTAN VALLEY. 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.