Page:The fairy tales of science.djvu/382

 the bridge; but one of them deserves particular mention on account of its stupendous magnitude.

The cylinder of this Cyclopean engine was nine feet long, twenty-two inches in internal diameter, ten inches thick, and weighed fifteen tons. Allowing for the waste, twenty-two tons of fluid incandescent iron were required for this enormous casting. After having been left for seventy-two hours in the mould in which it was cast, the mould was detached from it. It was still red hot! It was then left to cool, but it was ten days before it was sufficiently cool to be approached by operatives well-inured to heat, in order to detach from it some of the sand of the mould which still adhered to it.

This vast machine was fixed upon an iron stage, near the summit of one of the towers, and to the cross-head of the ram were attached massive chains, which descended to the level of the water, and embraced the tube to be raised.

The greatest weight lifted by the press was 1144 tons, but it was capable of raising 2000 tons. The quantity of water injected into the great cylinder, in order to raise the ram 6 feet, was $81 1⁄2$ gallons. When a lift of six feet was effected, the lifting chains were seized by a set of clamps, under the lowest point to which the cross-head descended, and while they were thus held suspended, the water was discharged from the great cylinder, and the ram, with its cross-head, made to descend. Meanwhile, the lengths of the chain above the clamps were