These necessary and ornamental structures, will be placed at equal distances along the whole line. , Six of them are now complete, and seven in progress. They are built of marble, or a light colored stone, from 14 to 20 feet in in the form of a height, rising up pyramid,and may answer to point out to strangers, the line of the aqueduct, as well as vents, through which the collected air may discharge itself.

CROTON ACIUEDUCT. 173

There is, in addition to the above, a vast amount of labor which cannot be well described, except by extending this report to an inconvenient length such as the rock and earth excavation, the stone quarried and dressed, the vast embankments thrown up in the numerous valleys and ravines, over which the aqueduct has to pass, with the necessary machinery and tools prepared for carrying on the operations. Some important and expensive structures, however, which are not included in the sketch given above, ought not to be omitted, although the description must be very brief and imperfect. Take for example the following :

1st. An archway over a street, in the village of Sing Sing, of 20 feet span, and 14 feet in height.

2d. The aqueduct bridge over the Sing Sing Kill a considerable run of water, possessing several mill privileges. The arch of this bridge is 88 feet span, and about 70 feet in height from the bed of the creek. The centres for turning this large arch, have been up for some time past, and thirty courses of the arch stone laid. The aqueduct proceeds from the Sing Sing tunnel, crossing both the aforesaid street and creek, from north to south. 3d. An archway over the Highland turnpike, now highway, about eleven miles below the Croton dam, of 20 feet span, and 14 feet in height. 4th.