STATION AR Y ENGINES.

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varied in the height of its lift by means of a screw on the cataractgovernor valve rod, which rod is under command of the engine-driver. It is evident that the smaller the opening of ’the deliveryvalve the slower will the plunger descend, the weight forcing itbeing constant. As the plunger descends the rod A rises, and bringsthe roller shown in the front elevation to bear on the lever M, andthus releases the quadrant K. Let the cataract plunger be up, thenthe engine is at rest, and remains so until the rod A shall have raisedthe lever M and released the catch U; the weight attached to B thensuddenly falls and opens the steam valve. Steam being suddenly letin on the piston causes it to commence its indoor stroke, and in doingso to give a downward direction to the motion of the plug rod S, thetappets of which coming into contact with the steam horns depressthem, and thus raising the lever B close the steam valve, at the sametime the piston continues its stroke under the expansive force of thesteam in the cylinder, and towards the end of the stroke raises theplunger of the cataract to prepare it to repeat its functions duringthe next indoor stroke. The horn or lever of the cataract being thusdepressed whilst the steam valve is closed, the catch U falls under theinfluence of the weight of the lever M under the projection on the cir-cumference of the quadrant K, thus preventing the opening of thesteam valve when the steam tappets have been raised, during the upor outdoor stroke of the piston, above or clear of the steam horns, untilthe cataract weight shall have fallen suffidently far to release the catchU, when the steam valve suddenly opens, as before described, andthe next indoor stroke is commenced. Having described the func-tions of the steam or top arbor and tappets, we will consider nextthe equilibrium stroke. The middle is the equilibrium arbor, andthe horn is shown in the side elevation. There are two quadrants onthis arbor. The first G is released by means of a cataract constructedprecisely like the one just described. The rod of this cataract isplaced inside the gear posts, as shown on the front elevation, whereasthat of the steam cataract is placed on the outside. There is anadjusting screw A on the equilibrium cataract rod, and two such, P,on that of the steam cataract. The lever C opens and closes theequilibrium valve. The opening is done by means of a counter-weightattached to the lever E, which operates on the release of the quadrantG. At the completion of the indoor stroke the piston pauses untilthe catch 0, actuated by means of the cataract, releases the quadrantG. It will be seen that this cataract rod releases on its down stroke,