It is not probable that any considerable quantity of water would have escaped, if there had been no other security than the stone and brick masonry but it is hardly possible ;

to make masonry so perfectly impervious, that it will not show wet, or a sweating appearance on the exterior wall, and the action of frost in this climate, will produce in such cases a deterioration, that may be slow, but will eventually destroy the work hence the ;

importance of using every precaution to guard against the smallest leakage. This bridge was erected under the contract of Young and Scott of Philadelphia, and the work conducted by Andrew Young (of the firm), who was the first contractor to commence work on the aqueduct. It is due to Mr. Young to say, this work was thoroughly executed ;

the arch proved this, when on striking the centres, it did not settle over ^ of an inch, and has not changed since. This I consider a very small settlement for so large an arch.

HARLEM RIVER BRIDGE. The width of the river at the place where the aqueduct line crosses it, is 620 feet at ordinary high water mark as has been before stated, the shore on the southern side is a ;

bold rock rising from the water's edge, at an angle of about 30 degrees, to a height of 220 feet on the northern side, a strip of table land forms the shore, and extends back from the ;