Those now in use, are kept warm by means of two large iron stoves, heated to great advantage and economy with Schuylkill and Lehigh coal.

It has been from the commencement determined, for the present, to erect only three wheels and pumps, which are now completed, and with them the most important parts of the duty of the committee. The first of the wheels is fifteen feet in diameter and fifteen feet long, working under one foot head and seven feet fall. This was put in

78 PRELIMINARY ESSAY.

operation on the 1st of July, 1822, and it raises one and a quarter million of gallons 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 revolutions in a minute. The second wheel was put in operation on the 14th of September, and is the same length of the first, and is sixteen feet in diameter it works under 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 raises one and one third million of gallons in twenty-four hours. The third wheel went into operation on the 24th December, 1822, and 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 raises one and a half million gallons of water in twenty-four hours. It is not doubted that 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.