It thus appears that making an average of the cost of crossing the valley on an arched bridge, by the three lines designated, and continuing the aqueduct on its regular inclination, will amount to $1,188,633. An estimate is then presented, for crossing the valley with pipes, or inverted syphons, of three feet diameter. The estimate proceeds upon the principle, that only two pipes will be required at present, which will supply about nineteen millions of gallons per day, and allow thirty gallons to each person, of a population of 600,000 inhabitants and in ;

order to show the economy of the plan of crossing the valley by pipes, instead of an aqueduct bridge, a sum or capital is added to the estimate, the interest of which will pay for any additional number of pipes that may, in future be required, from time to time, as the population increases, sufficient to carry the whole produce of the Croton river to the reservoirs.

The estimate for crossing with four pipes of 3 feet diameter, all laid, amounts to $453,670 For two pipes of the same dimensions - 303,926 For five pipes, all laid down 550,988 For only two pipes of the five laid down - 346,372

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.