early in the spring, under contract, to raise the same so high by the 1st of November following, as to throw at least two feet of water into the tunnel of the aqueduct. This requirement of their contract they have not fulfilled ; which is to be regretted, mainly on the ground that the work could not be left in as secure a condition against the spring floods, as it would have been left, had this condition of the contract been complied with. The contractors urged in excuse, the great difficulty in procuring sufficient quan- tities of large stone, and of a suitable quality, and the consequent failure, by their sub-con- tractors, 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 aque- duct 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 on piers Nos. 5 and 6, the masonry has been raised to eleven feet in height. We have supposed that the details of expenditure for Harlem Bridge, would be inte- resting to your honorable bodies, and have therefore to state, that the amount paid, from the beginning, and due to the first of January inst, is $210,000. The continuation of the work, sinking the remaining piers and driving the piles, mainly necessary for the proposed temporary bringing of the water across the river, and the expense of laying the pipes for that purpose, will amount to $116,558. The estimated cost of carrying the bridge up to its contemplated height, from the point or position in which it will be, on the 1st of July next, will amount to $596,779. After the water is introduced, by these temporary means, there will be no pressing necessity for the high bridge being erected faster than is convenient for the resources of the Corporation, and the economy of its construction, provided no objection should be urged against a reasonable interruption of the river navigation, by the persons interested therein, the value of which navigation is, at present, too small to be estimated. Entertaining this view of this important subject, the Board of Water Commissioners have determined, and so instructed the contractors, that without further instructions from them, the Board of Commissioners, they, the contractors, are to do no work on the bridge, excepting such parts as may be necessary and directed by our engineers, to carry the water on the temporary plan across the river, and the erection of the piers of the bridge up to high water mark; and to accomplish this, will keep them busily employed until the 1st of January next. In giving these instructions, we considered we should best meet the views of our fellow-citizens and the Common Council. If we are mistaken in the wishes of the Common Council, we shall be glad to be informed of the same. Under this arrangement of the work, the whole amount required by this depart- ment to bring the water to Murray's Hill, will not differ materially from $650,000, which includes the settling up the demands for work already done on the several contracts not yet completed. CLENDENING VALLEY. The Common Council will recollect that we informed them, through their Committee, in July, 1840, that we proposed dispensing with the arched bridges contemplated to be made by the original plan, over