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MODERN STEAM PRACTICE.

convenient form for transportation, as the cylinder is of smalldiameter, with a high rate of piston speed, and reducing gear forthe pumps. When the engines are of the horizontal type the wholeof the wheel gearing should be arranged on the same bed plateas the engine, and kept as compact as possible, since detachedmachinery cannot be so securely bolted down on the foundationsas when all the parts are well bonded together on a single bedplate.

PUMPING ENGINES FOR WATER-WORKS.

Having considered engines for pumping water out of mines,we now come to that dass of Cornish engine used for pumpingwater for the supply of large towns. The construction of thewater-works engine differs materially from that of ordinary mine-pumping engines. It is generally of the single-acting type; thewhole power of the engine is employed to lift a weighted plungerplaced at the end of the beam farthest from the cylinder, andwhich acts as an accumulator, forcing the water up the stand pipesto the height required for distribution through the mains. Thisheight of course depends on the altitude of the city or reservoirabove the source from which the pumps draw the water. Theengine beam is supported on columns, carrying a spring beam onwhich the main pillow blocks are securely bolted, and the endsare let into and rest on the end walls of the engine house. Theperpendicular motion of the piston rod at the one end of the beamand of the weighted plunger at the other end, is effected by meansof parallel motion of the ordinary description, with connecting linksfrom the crosshead, radius, and parallel bars. The air pump isworked off the centre of the back link for the parallel motion, atthe main pump end; while the feed pump has a shorter stroke, beingconnected by means of a long rod with a pin passing through themain beam. The plug rod for working the tappets of the valvegear is attached to the beams in like manner, the valve gear beingfitted with all the necessary cataracts, as in the mine-pumping engine.An engine house incloses all the machinery except the stand pipes,which are of great height, and require a separate tower. As thewater in these pipes is liable to become frozen in winter, objections