The culvert for the stream is 6 feet span and 148 feet

long. The larger culvert for a private road is 14 feet span and 141 feet long. The wall which supports the Aqueduct at this valley is 50 feet high. In this case, as in many others, the slope wall which covers the face of the embankment has an arch turned in it over the top of the culverts : the object of this is to

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prevent the direct pressure of the wall upon the top of the parapet wall, as it would tend to displace the coping or injure the parapet itself. After crossing Jewell's Brook the Aqueduct passes along the bank of the Hudson through the village of Dobb's Ferry, where there is a tunnel and a valley requiring a culvert, and continues from this place to the village of Hastings, where there is an Aqueduct bridge over a rail-road which is used for transporting marble from the quarry near by, to the landing on the Hudson River. Plate XVII. is a view of this bridge and the view under the arch shows the face of the quarry which is near the work ; the landing at the river is near by, giving a very rapid descent from the quarry. The arch has a span of 16 feet and a rise of 1^ foot. This bridge is twenty-one miles from the dam. From Hastings the Aqueduct continues along the bank of the Hudson until it reaches the village of Yonkers where it leaves the valley of the Hudson, and passing through a tunnel of considerable length reaches the valley of Saw-Mill River. At the crossing of this valley there is a culvert of 20 feet span for a public road to pass under the Aqueduct, and one having two arches each 25 feet span for the river.