If deemed necessary to build a lock in the centre, or channel of the river, it would add to the expense from one to two hundred thousand dollars more. The advantages to be derived, Mr. Seymour states, will be, 1st. That the waters of the Hudson, coming from the high lands around the Sacondagoand Mohawk rivers, are the purest in the United States. 2d. That a hydraulic power equal to thirty thousand horses, may thus be obtained, twenty-seven thousand of which may be employed for manufacturing purposes, and three thousand used for elevating the water to the reservoir for supplying the city. 3d. That by raising the water in the city above said dam to the height he proposes, all overslaughs and bars will be removed by the down current, and any vessel capable of entering the harbor of New York, may proceed to Albany and Troy without obstruction. 4th. That a safe and easy communication between this city and Albany, on the ice, for three months in the year, may be effected. That no injury will be caused to the land on the banks of the Hudson, as the water within the dam will never be higher than it now is in high tides and freshets. Another of the advantages is, that solid and pure ice may be obtained at a small expense. On the 29th of November Mr. Seymour made a further communication, in which he states, that the grounds upon which he desires to be understood, are, that his estimate is predicated on the supposition that he is at liberty to select the site of the dam, to build the coffer-dam as he may desire, and the lock or locks of such dimensions as he may deem necessary for the useful navigation of the Hudson river. That he will build the said dam for one million five hundred thousand dollars, and the said locks for one hundred and fifty thousand dollars each, and the coffer-dam for two hundred thousand dollars.