The constant and great expense attending steam en gines, strongly urged the substitution of water power as a less expensive and more efficient means of procuring an adequate supply of water for the use of the city and adjacent districts, who had not partaken of the benefits of that which had been already obtained. Accordingly, the watering committee were directed to take the subject into consideration ; and after consulting men of skill and science, to make a report and propose a plan to councils. This committee attended very assiduously to the duties of their appointment ; and, after consulting several dis tinguished engineers, made report, accompanied with some estimates, on the 8th of March, 1819, in which they recommended the erection of the dam locks, &c. since con structed. The best description of the different parts of the work will be found in the following extracts from the report of the watering committee, read to councils January 9th, 1823.
On the 19th of April, 1819, the work was commenced by Captain Ariel Cooley, with whom a contract was made for the erection of the clam, the locks and canal, the head arches to the race, and the excavation of the race from a solid rock, for the sum of 150,000 dollars.
" The river is about nine hundred feet in width ; one fourth of which at the bottom, on the eastern side, is sup posed to be rock, covered with about eleven feet of mud ; the remainder is of rock. The greatest depth is thirty feet at high water ; and it gradually shoals to the western shore, where the rock is left bare at low tide. The river, whose average rise and fall is six feet, is subject to sudden and violent freshets.
" Mr. Cooley determined, where rock was to be found, to sink cribs, formed of logs about fifty feet up and down stream, by 17 or 18 feet wide, which were sunk and filled with stone, securely fastened to each other above low wa ter, having the up-st•eam side planked from the bottom to the top ; and the space immediately above, filled to some extent, with earth, small stones, and other matter, to pre vent leakage. In that part where mud was found the dam is made of quarry spalls and earth, and raised about fifteen feet higher than the other part of the dam, which is an over-fall for the water ; the base of this mound is at least one hundred and fifty-feet, and its width on the top 12 fret ; and the whole of the top end of the up-stream side from the water edge is paved to the depth of 3 feet, with build ing stone, to prevent washing by water,. and injury from o ice. Between the mound dam and the over-fall, there is sunk on the rock, in 28 feet water, a stone pier, twenty eight feet by twenty-three feet, which supports the end of the mound, and protects it from injury by ice or water.
The contraction of the river by the mound dam, suggest ed to Mr. Cooley the idea of forming the dam in a diagon al line running up stream, and when nearly over to ion the rest of the distance at a right angle toward the shore, so as to join the head pier of the guard lock, on the western side, by which means a large over-fall was created, and the rise above the dam, in cases of freshet, considerably abated. The whole length of the over-fall is twelve hundred and four feet ; the mound clam, two hundred and seventy feet; the head arches, which will presently be mentioned, one hundred and four feet, making the whole extent of the clam, including the western pier, about sixteen hundred feet, and backing the water up the river about six miles. The water power thus created is calculated to be equal to raise into the reservoir, by eight wheels and pumps, upwards of ten millions of gallons: the lowest estimate of the quan tity of water afforded by the river in the dry season, is four hundred and forty millions per 24 hours, and as it is calcu lated, allowing for leakage, waste, &c. that forty gallons upon the wheel will raise one into the reservoir, the quan tity raised would be eleven millions of gallons per day.
" On the west side of the river there is erected a head pier and guard locks, whence there is a canal extending five hundred and sixty-nine feet to two chamber locks, of six feet lift each, by which the boats ascend or descend ; below these locks there is a canal into the river four hun dred and twenty feet long. The locks are built of dressed stone ; the upper canal is walled on the east side, and on the west it is rock ; the lower canal is formed of the stiff mud of the river, and covered with stone. The whole of the outer front of the locks and canal is protected by a wall on the upper part, and on the lower with stone thrown on the bank to prevent washing. On the east side of the river the whole of the bank was a solid rock, which it was necessary to excavate to the width of one hundred and for ty feet, to form a race, and a site for the Mill-houses, run ning parallel with the river. The length of the mill race is four hundred and nineteen feet ; the greatest depth of the excavation, sixty feet, and the least sixteen feet ; the gunpowder used, alone, cost the contractor upwards of twelve thousand dollars. At the upper part of this exca vation were erected the head arches, three in number, which extend from the east end of the mound darn to the rock of the bank; thus forming a continuation of the dam.