The height of the interior of the Aqueduct is 8 feet 5Jr inches, and the greatest width is 7 feet 5 inches. The sectional area of the interior is 53.34 square feet. On the first plane, the Aqueduct is larger ; being 2.05 feet higher at the gate chamber, 2.31 feet higher at 2244. feet from the chamber, and then diminishing, to the head of the second plane, where it assumes the size above mentioned and continues of that size throughout the remainder except in tunnels, where

it assumes the forms before described. Where the Aqueduct on the first plane is larger, the width across the interior at the spring line of the roofing arch is the same as the general width, but the increase takes place only in the height of the side walls, and the slope of the inner face of the walls being

the same, the width across at the spring line of the inverted arch will be less according to the increased height of walls. The original design was to continue the inclination which the second plane has, up to the Fountain Reservoir ; but it was considered desirable to draw from this Reservoir at a lower level, and the head of the Aqueduct was depressed for that purpose, and a less inclination adopted for the length of

the first plane. The roofing arch was left on the same inclination as was originally designed, except for the distance

of 2244. feet from the gate chamber, where it was built on a level.