The contractors urged in excuse, the great difficulty in procuring sufficient quantities of large stone, and of a suitable quality, and the consequent failure, by their sub-contractors, in the delivery of such stone ; which difficulty was enhanced by the rejection of every stone not deemed of the most durable quality. The work, on the whole, has been prosecuted, with the exception referred to, with commendable perseverance and energy, and the dam can be made to throw into the aqueduct the water required, early in the ensuing^summer, and can be conveniently completed during the summer months. It is presumed that the mason work of the dam, will derive additional strength from the extension of the time of its construction. The remaining part of the aqueduct proper, in Westchester, being the second, third, and part of the fourth divisions, is completed to the contemplated gate house at the Harlem River. HARLEM AQ.UEDUCT BRIDGE. This work has not been progressing as fast as was expected by the Commissioners and Engineers. To some extent the embarrassment has arisen by not finding a rock foundation in the bed of the river for pier No. 10 and after ;

removing the mud and boulders in the river to the depth of thirty-five feet below the sur-

MEMOIR OF THE face of the water, without finding rock, it was determined to place this pier on piles, and this work is now in progress. Although disappointed in not finding a stone foundation, we find the earth in the bed of the river of a compact character, and well suited to give security to the pier, by piling. The foundations for piers Nos. 7, 8 and 9 are, all of them, with their mason work, carried up above high water. Piers Nos. 3 and 4 have, also, been piled for masonry and ;