STATIONARY ENGINES.

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iron, and is rivetted on the under side of the front end of the boiler.The arrangement of the valves is somewhat similar to those of abath, where the hot, cold, and outlet valves all take off the samepipe. It is also important that the feed should enter the coldestportion of a boiler, which, from the action of the currents in thosewith internal flues, is just under the fire grate. When this is notattended to the seams and rivets are apt to leak from the suddenchanges of temperature to which they are subjected.

Instead of delivering the water over a stand pipe, as origi-nally in the Tettenhall engine, the Goldthorn Hill engine deliversthrough an air vessel into two reservoirs lying near the engine,holding together 1,500,000 gallons, and l'aised about 20 feet abovethe top lift. The reservoirs are arched over, and covered with2 feet of soil, for the purpose of preventing Vegetation in the waterand Variation in its temperature. These objects are well secured,as the water remains for months at the same temperature, andperfectly free from all vegetable or animal impurities. The reser-voirs are kept from being overfilled by a self-acting check valve,which shuts against any supply beyond a certain limit; and theman in Charge of any pumping engine at a distance at once knowswhen to stop work. The valve is so arranged that when the engineceases to work the supply from the reservoir to the town is main-tained through the flap valves placed underneath the self-acting stopvalve. The object of a stand pipe is that the water may be alwaysdelivered from the engine over one uniform height, and consequentlyof one uniform pressure on the engine, whatever varying circum-stances may affect the delivery after the water has once passed thetop of the stand pipe. For this purpose it is useful, but it is rathera costly and unsightly mode of attaining what in practice is foundto be an unnecessary degree of perfection, as at a tithe of its costall the necessary safety can be secured by pumping into an airvessel with a self-acting valve on the delivery side, so that, in caseof a pipe bursting, or any sudden diminution of pressure takingplace, it would be impossible for the engine to “go out of doors,”as it is technically termed, at more than a certain regulated speed,by the partial contraction of the area of discharge through meansof the check valve. Unless, too, the stand pipes are carefully casedin winter they are in great danger of being frozen, and very seriousconsequences have arisen from this cause. The great weight of thecolumn of water requiring to be set in motion from a dead stand at