water are the richly cultivated slopes with the 96 neat farm houses overlooking the lake, or the hills crowned with forest trees, while at intervals a valley or ravine opens and empties in its tribituary stream. Plate IX. is a view taken above the dam showing the position of the entrance to the tunnel which leads from the Reservoir to the gate chamber at the head of the Aqueduct. 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 Re- servoir 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 com- pletion, 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, X 97 was about 120 feet wide ; the average depth of water at this place was about 4 feet ; and the greatest depth 10 feet. The left bank of the river arose abruptly with rock, the channel was gravelly, and on the right bank a sandy table land about 3 feet above the ordinary surface of water ex- tended about 80 feet ; then a sandy hill arose on a slope of about forty-five degrees. In making the plan for a dam at this place it was deter- mined to fill the main channel and the table land on the right bank with an embankment of earth ; and on the left bank where rock was found, to build a body of masonry against the slope to the requisite height for the surface of the Reservoir and connect it with the embankment in the channel ; this masonry formed the overfall for the water, and the rock in the side of the hill adjacent to it was exca- vated down to the level of the overfall, thereby extending it into the hill, making the space for the water to pass over partly of masonry and partly of rock. The embankment extended with a slope on the upstream side giving it a broad base, and the lower or downstream side was faced with a heavy wall of stone. There was a timber pier constructed in the embankment extending across the channel and faced with plank on the upstream side. The overfall was made of such length as was thought sufficient to pass all the water of the river during its highest stages, and with the view of adapting it to such purpose, examinations were made to find the highest marks of floods on the banks of the river ; and those who were engaged in determining these marks were guided also by the observations of the inhabitants of the vicinity who had long known the river in its various 25 98 stages. High freshets were witnessed during the construc- tion of the work, for in the course of two years that the work was going up, all the various changes and freshets of rainy seasons were experienced, and those in charge of it did not neglect to note the quantity of water flowing on such occasions. With such opportunities to become acquainted with the changes of the stream they could not fail to know the quantity of water flowing at periods of the highest freshets, and know- ing it, to adapt an overfall of sufficient capacity for its dis- charge. For this purpose it was thought ample provision was made ; yet at the time when the work was nearly completed such a flood occurred as could not have been anticipated from previous knowledge of the River; the water filling the entire passage at the overfall, flowed over the top