HYDRAULIC RAH, a simple and conveniently applied mechanism, by which the momentum or weight of falling water can be made available for raising a portion of itself to a considerable height. In the annexed figure, which represents, a section of Montgolfier's hydraulic rain, R is the reservoir from which the water falls, RS the height of the fall, and ST the horizontal tube which conducts the water to the engine ABIITC.
E and D are two valves, the former of which closes its cavity by ascending, the latter by descending; and FG is a pipe reaching within a very little of the bottom C13. The valves arc such that the water at its normal pressure cannot support their weight; the valve E is prevented from falling below a certain point by a knob above mn. When the water is' allowed to descend from the reservoir, after filling the tube BUS, it rushes out at the aperture mn, till its velocity in descending RST becomes so great as to force up the valve E, and close the means of escape. The water being thus suddenly checked, and unable to find a passage at inn,will produce agreat action on every part of the containing vessels, and by its momentum raise the valve D. A portion of water being admitted into the vessel ABC, the impulse of the column of fluid is expended, the valves D and E fall; the opening at D being thus closed, and that at inn opened. The water now rushes
out at inn as before, till its motion is again stopped by its carrying up the valve E, when the operation is repeatdd, the fluid impulse opening the valve at D, through which a portion of the water passes into ABC. The valves at E and D thus alternately closing and opening, and water at every opening of D making its way into ABC, the air therein is condensed, for it has no com munication with the atmosphere after the water is higher than the bottom of the pipe FG. This condensed air, then, exercises great force on the siirface, op, of the water, and raises it in the tube, FG, to a height propor tioned to the elasticity of the imprisoned air. The principles of the hydraulic ram are susceptible of a very extensive application. In well-constructed rams, the mechanical effect obtained has been found to be about two-thirds of the energy in the falling water.
For raising comparatively small quantities of water, such as are necessary for the supply of single houses, farm-yards, etc.—where water at the lowerlevel is plentiful and cheap— the hydraulic ram is a most useful piece of mechanism. Its details have been greatly improved since the time of Montgolfier.