MODERN STEAM PRACTICE.

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suited for a 13-feet stroke. The pump rods are connected directlyto the piston rod, which is guided by means of a crosshead and cast-iron guides placed underneath the cylinder. The light wrought-ironbeam for working the plug rod, air pump, and feed pump is placedoverhead, and is worked from a continuation of the piston rod. Thevertical motion of the plug rod is maintained by means of motionrods fitted on each side of the beam, and is guided with a bracketbolted to the nozzle ehest; the other end of the beam slides in cast-iron guide bars, with gudgeon and sliding blocks fitted to it. Theair pump is placed centrally with the condenser, and is worked offa continuation of the plug rod; the air-pump bücket foot and headvalves are fitted with small disc india-rubber valves, with guardssecured by a single stud bolt in each. The feed pump has a hollowplunger, and is worked off the overhead beam directly, the pumpbeing bolted to the side of the hot well. This engine goes far tomeet the requirements of the practical miner, being well arranged,with easy access to all the parts; and it is much cheaper in first costthan some other beam engines.

The pumps for this engine consist of two lifting sets 20 inchesin diameter, and one forcing set 26 inches in diameter, placed oneabove the other, as shown in Fig. 123. In deep pits this plan isalways adopted, the lifting sets placed at the bottom of the pitdischarging into a cistern from which the forcing set draws itssupply. By this means the bücket and clack of the lifting set canbe withdrawn and replaced should anything go wrong, and thewater rise above the valve chests, which could not be done were theforcing set placed at the bottom of the pit. The pump valves areof the ordinary description, with inclined seatings; the plunger ofthe forcing set has just the necessary clearance in the barrel, thevalve chests being arranged at the bottom; the water is dischargeainto an air vessel surrounding the stand pipe, by which means theshock in forcing it up is greatly softened.

For very deep pits a series of lifts is necessary. The followingexample (Figs. 124 and 125) of pit work in Cornwall forms a goodarrangement: “The diameter of the steam cylinder is 90 inches.The stroke is 11 in and 10 out, in miners’ parlance; that is to say,

11 feet in the cylinder and 10 feet in the pumps. The first lift ofpumps from surface, or ‘grass,’ is the house lift, which is employed inlifting water from the adit to the condensing cistern of the engine.The plunger of this lift is 12 inches in diameter, and the rising main the