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. Plate XVIII. is a view of the work at Saw Mill River. The water is set back at this place by a dam for a mill a short distance below, giving the stream an appearance of more magnitude than it really possesses. This point is 25 miles from the dam. The wall which supports the Aqueduct over this valley is 40 feet high. From Saw-Mill River the Aqueduct passing through one

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tunnel soon reaches Tibbit's Brook, which it crosses by means of a foundation wall about 30 feet high and a culvert of 6 feet span, and continues along the south side of the valley of this brook, thence to the Harlem River which it crosses at one mile from Mc'Comb's Dam. This crossing is thirty-three miles from the Croton Dam, and about ten miles from the City-Hall. The distance across this valley is about a quarter of a mile, and the surface of the River is 120 feet below the bottom of the Aqueduct. In all the examinations which were made with a view of bringing water from Westchester County, the crossing of this River, or arm of the sea, was regarded as the most formidable work that would be encountered ; various plans were proposed, and in presenting these plans the project was such as to call into requisition much talent and skill.