STATIONARY ENGINES.

IS I

our coal, ironstone, and other ores. There would be great difficultyin reaching those vast Stores of hidden treasure without the power-ful aid of the steam-engine, which enables us to overcome many ofthe risks and difficulties encountered in mining operations.

The single-acting beam engine is generally adopted for pumpingthe water from great depths. These great beams of cast-iron—and in some cases of wrought-iron plates, stiffened with angle orT-iron—are supported by pillow blocks, resting on a wall of masonrycarried up to a convenient height above the top of the cylinder.The beam is in two halves, with gudgeons between them, and isconnected to the piston-rod of the steam cylinder by a crosshead

Fig. 87.—Crosshead and Side-links of Parallel Motion for Piston-rod of Cornish Engine.

a, Crosshead. b, Piston rod. c, Loose collar. d, Key. e, Links, f, Beam gudgeon.g, Bearings for parallel bars.

and parallel motion; and in some instances the crosshead of thepiston-rod works in suitable cast-iron guides, and is connected tothe beam gudgeons by plain links. This motion is not so expen-sive in first cost, and the wear and tear is greatly reduced.

The cylinder A is a plain casting with port C cast on at the top,incased in an outer cylinder B, to which it is bolted, flanges beingcast on each at the top for that purpose. The outer casing orcylinder is bolted to a separate bed-plate D at the bottom. A spaceis left between the two cylinders for the admission of steam fromthe boiler; and they are made steam-tight at the bottom, raised strips