in 1819, a contract wasmade with Capt. Ariel Cooly, for damming the Schuylkill. For the sum of $150,000, he undertook to throw a dam of sufficient height across the river to create the requisite head of water, to construct the locks and canal for the accommodation of the navigation, to build the head arches of the race-way for the water power, and to excavate the race out of the solid rock. The whole length of the dam, including the

* Notes on Rio de Janeiro, by Jno. Luccock, 1820.

PRELIMINARY ESSAY. 77

head arches, and the water pier, exceeds 1600 feet, and it backs the water up the river about six miles.

By the water power thus created, operating upon eight wheels and pumps, it is estimated that ten million gallons may be daily thrown into the reservoirs; the flow of the river in

dry seasons was supposed to be 440,000,000 gallons in the 24 hours, and allowing for leakage, wastage, &c. it is calculated that 40 gallons upon the wheels will raise one into the reservoir which would give a result of 11,000,000 gallons a day. " 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 forty feet, to form a race as a site for the mill houses running parallel with the river. The length of the mill race is four hundred and nineteen feet, the greatest depth of excavation sixty feet, and the least sixteen feet. The gunpowder used, alone cost the contractors upwards $ 12,000. At the upper part of this excavation were erected the head arches, three in number, which extend from the east end of the mound dam, to the rock of the bank, thus forming a continuation of the dam.