salaries and other incidental expenses of the Commissioners already incurred, and including 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

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 semicircular 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 :