obstruc- tion. 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. If a different site from that he has named, shall be selected, then he will build the dam for any price agreed upon by referees, composed of Civil Engineers, furnish the requisite security, and guarantee its durability for five years ; he will require two years, from the first of August next, to form the dam up to low water line ; let it settle the third year, and finish the whole by the first of August, 1839. The powers delegated to the Commissioners, and to the Common Council of this city, by the act of 2d of May, 1834, cannot extend to a project which contemplates erect- ing a dam in the Hudson river, beyond the boundary line of the State of New York. It is true, the act makes it the duty of the Commissioners to examine and consider all matters relative to the supply of this city with pure and wholesome water ; to adopt a plan, and to report it to the Common Council. If the Common Council approve the plan, it is to be submitted to the ballot-box, and if concurred in by a majority of votes, the Common Council may borrow the money, and the Commissioners may proceed to carry the plan into effect. The operation, however, must be performed within this State, and under the jurisdiction of its government, and not extend into the territory of another State, as the plan for damming the Hudson evidently does. The Commissioners have not deemed it their duty, therefore, to incur any expense, by engaging Engineers to ascertain the most eligible site for a dam, reservoir, &c., or for sounding the river, or estimating the expense of erecting the dam, locks, reservoir, milKbuildings, sluices, pumps, &c., but MEMOIR OP THE have confined themselves to a mere outline of the plan, as proposed by Mr. Seymour, and to a brief statement of some of the difficulties to be overcome, which have appeared to them inevitable, and which they will now proceed to designate. 1st. The great and leading object of the act of the Legislature is, to procure a plen- tiful supply of pure and wholesome water for the use of the inhabitants of this city. Now, although the Commissioners have no reason to doubt that the waters of the upper Hudson are perfectly pure, and that by building a water-tight dam across the river, from this city to the shores of New Jersey, the salt water will be ejected, and the fresh will take its place above the dam, yet we fear, that, in locking vessels up, more or less of the salt water below the dam will follow them, and although the quantity may be compara- tively small, the constant repetition of the operation, by the hundreds of vessels going through the locks, both day and night, may, perhaps, be the means of unfitting the water, in a measure at least, for domestic use. 2nd. The project cannot be carried into effect, except by an Act of the Legislature of New Jersey, as well as by this State, and perhaps by the Congress of the United States. If all navigable rivers are common highways, it is a question at least, whether obstruc- tions can be placed in them without interfering with the powers of Congress to regulate the Commerce of the Nation. 3rd. It must be conceded, as the Commissioners think, that the building of the pro- posed dam would be an obstruction of more or less magnitude to the navigation of the river; for although a vessel may be locked through in 10 or 15 minutes, as asserted by Mr. Seymour, still, if we revert to the great