Plate VII. is an isometrical drawing of one of the culverts with rectangular wings and parapets ; the body of the culvert is cut in two in the drawing, showing that it may be of any length, according to the width of the embankment through which it is The length is generally constructed. arranged so that the slope of the embankment may intersect the rear of the top of the parapet and pursue a direction down, parallel with the slope of the top of the wing walls.

Gate Chamber at the Head of the Aqueduct and Grade of the Water-way of the Aqueduct.

Plate VIII. is a longitudinal section through the tunnel and gate chamber at the head of the Aqueduct showing its connection with the Fountain Reservoir. This gate chamber is not in any way connected with the dam itself but stands some distance from it, and the water reaches it by means of the tunnel which leaves the Reservoir above the dam and passes through the solid rock of the hill against which the masonry of the dam is built, a distance of over 200 feet. This tunnel descends into the Reservoir, so that

the centre of it at the mouth is about 12 feet below the sur-

face of the water ; any floating substance cannot enter it, and during the winter season when the water is frozen over no obstruction can take place to the flow into the Aqueduct, and during the summer season the water will be drawn from a level where it is cooler than at the surface. The gate chamber has two ranges, or sets of gates ; one called regulating gates, and the other guard gates : the