the rock, which over the whole island, presents a singularly broken and uneven formation. In almost every instance of excavation, the rock was found above the proposed bottom of the Reservoir, and the difficulty of preventing leakage along the surface of this rock may easily be conceived ; but considering that measures are taken to prevent such an occurrence, another difficulty is still presented in the formation of the rock : the veins and fissures which are frequent

in this gneiss formation would possibly afford courses for the water to escape ; the rock being unsound in many instances, would render such an occurance still more liable. A Reservoir has however, been constructed here which proved, when it was filled with water, that sufficient precaution was used to prevent leakage, and that the difficulties which presented themselves before the commencement of the work were no longer to be feared. The embankments forming the Reservoir are made of good assorted earth, and a portion of the bank is puddled, or made compact and impervious by wetting the earth and using a spade to force it into a compact state. They are about 20 feet wide on the top, and increase in thickness towards the base by a slope on both sides : the outside face of the Reservoir bank has a slope of 1 foot horizontal to 3 feet vertical : the inside has a slope of li foot horizontal to 1 foot vertical. The outside face is protected by a stone wall 4 feet thick having the face laid in mortar : the inside face is protected by a slope wall of stone laid without mortar, If foot thick. The top of the bank is 4 feet above top water line, and the inside slope wall terminates at 2 feet above top water line, leaving the remainder of the face to be covered