It thus appears, if it should be deemed necessary to lay down four pipes in the firs-t instance, at a cost of $453,670, which would furnish 38 million of gallons every twentyfour hours, there would still be a saving in the expense, by carrying the water over the valley by pipes, of $734,963, adopting the average cost of carrying it by an aqueduct bridge; and comparing the cost of building the bridge on the diagonal line, which is the cheapest, with the estimate for laying two pipes that will carry 19 millions of gallons daily, there is still a saving by the latter plan of $679,074.

CROTONAdUEDUCT. 155

The Commissioners were in hopes, as they had abandoned the idea of crossing the Harlem river with an aqueduct bridge, that they would have been enabled to recommend the building of a similar structure for carrying the water over the Manhattan Valley a ;

work that must have been an ornament to the city and a credit to the Corporation, as well as to the individuals having charge of its execution ; but the vast difference in the cost, has put itentirely out of the question, and they have accordingly adopted the plan of carrying the water over the valley, by pipes, or inverted syphons. In adopting the foregoing plans, for conducting the water over the Harlem river, and in crossing the valley at Manhattanville, on the island of New York, both the Commissioners and engineers have been governed by a wish to reduce the cost of the work to the lowest possible sum, consistent with its durability and permanence. The plan, however, may be modified, both in those particulars as well as others, if deemed expedient by your honorable body, and a high bridge may be substituted, instead of the syphon at the Harlem river and Manhattanville, by incurring an additional expenditure of one million, one hundred and eighty-eight thousand, seven hundred and ninety-two dollars; and by delivering the water in the city, at a much less elevation than what has been contemplated, a lower grade may be adopted for the aqueduct, that would prevent its rising above the present surface on this island.