Provision is made for four pipes of 3 feet diameter, but at present only two are laid which answer the demands of the city at this time. At the bottom of the valley waste cocks are provided which discharge into a sewer leading to the Hudson River, a distance of half a mile. The lowest point in the pipes is 102 feet below the bottom of the water way of the Aqueduct on the north side of the valley. From Manhattan Valley the Aqueduct passes through a tunnel, and following its course the next work of interest is

at Clendinning Valley, which is thirty-seven miles from the Croton Dam. This valley is 1900 feet across, and the Aqueduct is supported upon a foundation wall of dry stone work having the face laid in mortar, except over three streets where bridges are built, having an arch of 30 feet span for the carriage-way and one on each side of 10i feet span for the side walks. These bridges are over 98th, 99th, and 100th streets. Plate XXI. is a view of a portion of the work at Clendinning Valley showing the three bridges ; and comprises a length of about 700 feet. The greatest height from the foundation to the top of the work is 50 feet, and the width at the bottom of the Aqueduct is 30 feet. Parapet walls are built on the sides of the wall above the bottom of the Aqueduct to support a covering of earth over it.