high water line of the river, and 149 feet above the lowest foundation of the piers that have been commenced. The width across, on the top of the parapets, is 21 feet ; the exterior of piers, spandrels and parapets has a bevel of 1 to 48, and have openings in the interior walls. The space between the parapets is arranged to receive and protect from frost two cast iron pipes, each four feet in diameter, which are to lie 12 feet below the grade line of the aqueduct, to which they will descend from the gate chambers at the ends of the bridge. The object of using pipes in this case, is, more effectually to secure the conduit from leak- age, that might eventually injure the masonry of the bridge, and it incidentally allows the bridge to be constructed of less height. To make the capacity of the pipes for conveying water equal to that of the aqueduct, an extra fall of two feet has been given across the bridge, and the aqueduct on the southern side of the river is constructed two feet lower than the regular grade, to accom- modate this arrangement. It is intended in the first place to put down pipes 3 feet in diameter, and to increase the size as the wants of the city may require. The foundations of all the land piers but two have been put down, with bearing piles to support them ; they are placed below high water line ; and 5 to 6 of the base courses of masonry have been laid on each ; the remaining land pier and both abutments will have a rock foundation. There are seven piers in the river,, the foundations of four of which have been laid; for two of them solid rock has been obtained at a depth below high water line of 17 feet for one, and 35 feet for the other. The pier next the northern shore has a piled foundation ; to prepare it, an excavation of 16 feet was made, passing through the strata of mud, sand and detached rock, whence the piles could be properly driven. The piles were of oak, from 16 to 35 feet long, and driven at 2k feet apart from centre to centre. The other pier, (called No. 10 in the general series,) for which a piled foundation has been prepared, is near the centre of the river channel. The stratum of boulders lies much lower at this place, and required an excavation to be carried 30 feet below common high water line, before a suitable stratum for driving piles could be reach- ed. When the excavation was carried to this depth, boring was made to ascertain if rock could be found for the foundation ; but after going down Avithout success to a depth of 70 feet below high water, the effort was abandoned, and the driving of piles commenced, as the only means of securing the foundation. The piles were driven at three feet apart from centre to centre, to the depth of 30 to 35 feet. It may be remarked, that all the piling for the bridge has " come home" with great regularity and firmness, and gives great confidence that it will afford an unyielding sup- port to the structure. The foundations for the water piers are yet to be put down ; two of 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