In reference to this work it is greatly to be regretted that Forty-second-street should have been reduced to so low a grade, which has increased very greatly the cost of the walls, without adding in any respect to the utility or beauty of the work. This location being higher than any of the adjoining lands, it is not obvious why your predecessors required it to be cut down at so great an expense to the city, and disadvantage to the reservoir, as it required the walls on Forty-second-street to be sunk nearly twelve feet lower, and on the sides, fronting the Fifth avenue and Fortieth-street, an average of eight feet lower than would otherwise have been required. The remaining work, south of the distributing reservoir, consists in laying down the large mains to supply the lower parts of the city with water, and the small pipes to distribute it through the streets, the progress of which is known to your honorable bodies.

182 MEMOIR OF THE During the last fall, the water was introduced, several times, from the Croton Lake into the aqueduct. For greater security it is made to pass through two chambers, each having nine small gates, of 16 inches by 40 inches, by which any unusual velocity, growing out of the variations in the head of the water in the lake, may be controlled or equalised. In the instances we have referred to, the water passed through the first eight miles of the aqueduct, to a waste weir at Sing Sing, where it was discharged in six hours. This strengthens the opinion, that it will certainly pass through the whole line, as fast as at the rate of one mile per hour, which is the rate calculated on. The frequent use of the thermometer has shown that the temperature of the aqueduct was fifty degrees, in our coldest days previous to the 1st of January.