averaging 45 feet below the surface, must be made from 140th to 135th street inclusive. The line then continues in the 10th avenue to 107th street, and makes a curve easterly to 104th street, and from thence runs parallel with, and 125 feet from, the northerly line of the 9th avenue to 90th street, where another curve occurs, carrying the line to 85th street, where it enters the receiving reservoir. From this reservoir it is proposed to conduct the water, through the 5th avenue, to the distributing reservoir on Murray Hill, by iron pipes. In following the line of aqueduct as above described, its grade will, in several places, be above the present surface of the ground, and from 102d to 95th street inclusive, in order to accommodate the carriageway and sidewalks, archways must be erected over the streets, and the aqueduct carried on a stone embankment of from 33 to 48 feet in height ; and in passing through the 5th avenue with the iron pipes to the distributing reservoir, a portion of the carriageway must be graded, in order that the pipes may be sunk to a pro- per depth below the surface of the street not to be out of the reach of repairs, should any be at any time required, nor so near the surface as to be exposed to the action of frost. The Commissioners submitted an estimate to your honorable body in their report of the 3d of July last, of the probable cost of completing the first and second divisions of the aqueduct, and promised to report an estimate of the total amount that would be required to complete the whole project, including the receiving reservoir between the 6th and 7th avenues and 79th and 86th streets, and the distributing reservoir on Murray Hill, in order that authority might be obtained from the Legislature to raise the additional funds required. The chief engineer has, accordingly, at the request of the Commission- ers, furnished them with his views on the subject, so far as they relate to the operations of his department of the works, including the most substantial and economical mode of con- struction, with the probable expense of such construction ; and the Commissioners have added the actual cost of the land paid for, and the probable cost of that still to be acquired ; also the sum paid for the temporary use of land for roads and embankments, and the probable expense of what may still be required, with other damages and probable charges for water and land, incident to the undertaking ; also the amount already paid for salaries and other incidental expenses of the Commissioners already incurred, and includ- ing the amount that may be incurred, the estimates thus embracing every expenditure already made and to be made, from the commencement to the final completion of the work. In bringing together the several items which compose this estimate, an attempt has been made to cover every positive and probable expense, in the hope, at the same time, that the actual cost will be less than that stated, which the Commissioners will use every means in their power to effect, and thus a third application to the Legislature be avoided. By a reference to the report of the chief engineer, alluded to above, it will be seen that the crossing of the valley at Manhattanville, with the aqueduct, and the erection of the receiving and distributing reservoirs, are works of great magnitude and cost. For 39 154 MEMOIR OF THE crossing the Manhattan Valley, three lines are designated, and an estimate furnished for carrying the aqueduct on a high bridge from the north to the south grade. The first line runs diagonally from 128th street in the 9th Avenue, to between 118th and 119th streets, in the 10th Avenue. The second line crosses the valley, and runs parallel with, and 125 feet from, the 10th Avenue. The third line continues through the centre of the 10th Avenue. The crossing of all these lines is to be effected by means of a bridge, with semi- circular arches of 50 feet span. The length of the three lines from grade on the north, to grade on the south side of the valley, are as follows : First, or diagonal line, - 3,300 feet. Second, running 125 feet east of 10th Avenue, - - 3,700 feet. Third line, running through the 10th Avenue, 3,700 feet. The maximum elevation of the bridge above the natural surface of the ground to grade line, is about 103 feet, and to the top of the parapet wall 116 feet. To erect a bridge on the first or diagonal line, as per estimate, will cost $983,000 00 The same for the second line, - 1,286,880 00 The same