The entablature which is seen on the left against the rock, is built directly over the mouth of the tunnel, and from this

the tunnel extends through the rock to the gate house, which

is seen on the right of the picture and some distance from the dam. The structure which is seen in the centre of the picture and on the ridge of the dam is a gate house over a culvert which extends through the body of the dam this ;

culvert is 30 feet below the surface of water when the Reservoir is full, and has gates which are operated by means of rods which rise to the interior of the house. During low stages of the River the water which is not drawn oft' by the Aqueduct may pass through this culvert and allow none to pass over the dam. The entrance to the tunnel is protected by a screen of timber work. Plate X. is a representation of the entablature over the mouth of the tunnel, showing the inscriptions upon it, relating to the date of the commencement of the dam and its completion, the persons who had contracts for building it, and those having charge of the work during the time. Plate XI. is a view taken from a point below the dam and shows the relative positions of the dam and the gate chamber at the head of the Aqueduct. The original channel of the River where the dam is built,

;

was about 120 feet wide ; the average depth of water at this