" On the west of the excavation are erected the Mill houses, forming the west side of the race, which is sup ported on the other side by the rock rising above it seven ty or eighty feet perpendicularly. The south end, or wall of the race is also of solid rock ; and the Mill-houses are founded on rock, so that nothing can be contrived more secure in all respects.
"The race is about ninety feet in width, and is furnish ed with water through the head arches, which allow a pas sage of water of sixty-eight feet in breadth, and six feet in depth, to which the race is excavated below the over-fall of the dam, and of course room is allowed for a continual passage of 408 square feet of water. These arches are on the north of the race, and the mill-buildings being on the west, the water passes from the race to the wheels, which discharge the water into the river below the dam. The gate of the centre arch is upon the principle of a lock gate, and admits the passage of boats &c. into the race; at the south end of the mill-buildings there is a waste gate, eight feet wide, by which (the upper gates being shut) the wa ter can be drawn off to the bottom of the race.
"The mill-buildings are of stone, two hundred and 38 feet long, and fifty-six feet wide. The lower section is di vided into twelve apartments, four of which are intended for eight double forcing pumps. The other apartments are for the forebays leading to the water-wheels. The pump and forebay chambers are arched with brick, and are perfectly secure from the inclemency of the winter. Those now in use are kept warm by means of two large iron stoves, heated with Schuylkill and Lehigh coal. A gallery is erected, extending the whole length of the build ing, from which all the wheels may be seen at one view. The centre part of the buildings is one hundred and nine ty feet by twenty-five feet, with circular doors to the pump chambers, and a range of circular windows over the arch ways of the wheel rooms; on a line with the cornice of the central part is the base course of two pavillions, with Do. ric porticoes, which terminate the west front. On the east front, immediately over the pumps and forebay rooms, is a terrace, two hundred and fifty,-three feet long, and twenty-six feet wide, paved with brick, and railed, forming a handsome walk along the race, and leading by steps at the end to the top of the head arches, mound, dam, and pier.
" It being ascertained, that in the whole extent of the foundation along the race, under a six feet head of water, there is no leak, it has been from the commencement de termined, for the present, to erect only 3 wheels and pumps, which are now completed. The first of the wheels is fif teen feet in diameter, and fifteen feet long, working under one foot head, and seven feet fall. This was put in opera tion on the 1st of July last ; and it raises 1 million of gal lons of water to the reservoir in twenty-four hours, with a stroke of the pump of four and a half feet, a diameter of sixteen inches, and the wheel making eleven and a half re volutions in a minute. The second wheel was put in ope ration on the 14th of September last ; and is the same length as the first, and 16 feet in diameter ; it works un der one foot head, and seven and a half feet fall, making thirteen revolutions in a minute, with a four and a half feet stroke of the pump, and raising 1 1-3 million of gallons in twenty-four hours. The third wheel, which went into operation on the 24th of December, 1822, is of the same size as the second, and works under the same head and fall, making thirteen revolutions in a minute, with a five feet stroke of the pump, and raising 11 million of gallons in twenty-four hours. The second wheel can be made to raise an equal quantity ; thus making the whole supply upwards of four millions of gallons in twenty-four hours.
"The wheels are formed of wood, and put together with great strength. The shafts are of iron, weighing about five tons each. The great size and weight of the wheel give it a momentum which adds greatly to the re gularity of its motion, so necessary to preserve the pumps from injury under so heavy a head as they are required to work, which is a weight of 7900 lbs., the height ninety-two feet.
" The wheels being sunk below the usual line of high water, it might be supposed that they would be obliged to stop at that time ; but this seldom happens, except in the spring tides, at the full change of the moon, which, upon the average stops them about sixty-four times a month. It is found that they are very little affected until the back water is about sixteen inches on the wheel.