of the State having occurred, the former Commissioners were reinstated, and now have charge of the work — without any change occurring in the engineer department, other than by the re- duction consequent upon the finishing of operations. Having thus brought our narrative of the progress of the work to its conclusion, it re- mains to present, as promised, a connected view of the aqueduct, its chief and most striking constructions, its general plan, and such other details as are likely to in- terest our readers. We are permitted by Mr. Jervis to avail ourselves, for this purpose, of the descrip- tion published by him on occasion of the civic celebration of the 14th of October, to which he enables us to add some further particulars of the state of the work, up to the instant of passing these sheets through the press : * I've raised A monument more durable than brass, Which, not the wasting storm nor blast all impotent Shall e'er o'erthrow, nor yet innumerable Successive years, nor flight of time. 51 MEMOIR OF THE DESCRIPTION OF THE CROTON AdUEDUCT BY J. B. JERVIS, GENERAL DESCRIPTION OF THE LINE. The Croton Aqueduct was designed to supply the city of New York with an abun- dance of pure and wholesome water. It commences about six miles above the mouth of the Croton river, where a dam has been constructed to elevate the water of the river 40 feet, to the level of the head of the aqueduct, or 166 feet above mean tide. The course of the aqueduct passes along the valley of the Croton to near its mouth, and thence passes into the valley of the Hudson. At 8 miles from the Croton dam, it reaches the village of Sing Sing, and continues south through the villages of Tarrytown, Dobbs' Ferry, Hastings, and Yonkers. At the latter place, it leaves the bank of the Hudson, crosses the valleys of Sawmill river and Tibbits' brook, thence along the side of the ridge that bounds the southerly side of Tibbits' brook valley, to within 34 miles of the Harlem river, where the high grounds of the Hudson fall away so much as to require the aqueduct to occupy the summit of the country lying between the Hudson and East rivers. This formation of country continues to, and is terminated by, the Harlem river, at the point where the aqueduct intersects it, which is one mile northwesterly from Macombs' dam.. The length of the aqueduct from the Croton dam to Harlem river, is 32.88 miles, for which distance it is an uninterrupted conduit of hydraulic stone and brick masonry. The high ground that bounds the northerly side of the Harlem river valley, is very near the level of the aqueduct at that place ; and the width of the valley at the aqueduct level is about 1450 feet, or a little over one quarter of a mile ; over which a bridge is designed to be constructed (and is now in progress) at an elevation of 114 feet above the level of high tide in the Harlem river, on which iron pipes are to be laid to convey the water across the valley. The shore on the southerly side of the river is a bold, precipitous rock, rising at an angle of about 30 degrees, to a height of 220 feet, or about 100 feet above the level of the bottom of the aqueduct. After crossing this valley, the aqueduct of masonry is resumed, and continued 2.015 miles, to the termination of the high ground on the north side of Manhattan valley. This valley is 0.792 mile wide at the level of the aqueduct ; below which it descends 102 feet. The conduit of masonry here gives place to iron pipes, which descend into the bottom of the valley, and rise again to the proper level on the opposite side ; from which point the masonry conduit is again resumed, and crossing the Asylum ridge, and Clen- dening valley, is continued 2,173 miles,, to the receiving reservoir at Yorkville. This reservoir is bounded by 86th street on the north, 79th street on the south, 7th Avenue on the west, and 6th Avenue on the east. It is 1826 "feet long and 836 feet wide on the outside angle of the embankment; containing an area of 35 acres, divided into two divisions, and is (a little over) 5 miles from the City Hall. From the receiving reservoir, a double line of iron pipes three feet in diameter, are laid down in 80th street and 5th Avenue, to convey the water 2..176 miles to the distributing reservoir at Murray Hill. The location of this reservoir is on the 5th Avenue, between 40th and 42d streets, and is three miles from the City