side of the rocky hill, and continues over an uneven surface encountering two tunnels before it reaches Manhattan Valley, which is about 35 miles from the Croton dam. This valley is four fifths of a mile wide where the Aqueduct meets it, and the depression is 102 feet below the plane of Aqueduct grade. Here was an opportunity for constructing a work of architectural beauty and boldness by building up with arcades of arches, one line above another, and thus maintain the regular inclination of the Aqueduct ; but considerations of economy forbade it. Where the Aqueduct reaches the

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north side of the valley, a gate chamber is formed, and from this, two pipes of 3 feet interior diameter descend to the bottom of the valley and ascend on the south side to another gate chamber where they connect with the Aqueduct again. 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