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BULLETIN 119, U. S. NATIONAL MUSEUM. 



motive power of the other, thereb}' insuring the constant action of 

 at least one pump piston upon the Avater to be raised and relieving 

 the action of the pump from shocks and concussions. 



The attachments to bring this arrangement about are alike on both 

 engines. A complete cycle is as follows : 



When steam enters the cylinder of one of the engines its piston 

 commences to move and at some fixed point in its stroke it actuates 

 the steam and exhaust valves of the other engine through a series of 



FIG. 8. CORLISS STEAM PU.MPj 1879. 



levers. Still going on, it completes its stroke and finally terminates 

 its motion by closing its own valve by means of a stopping lever. 

 Meanwhile the piston of the second engine, having been set in motion 

 by the first, has commenced its own stroke. On its way it encounters 

 and moves the valve of the first engine through a series of levers; 

 continues to the end of its stroke, closing its own valve, and rests until 

 again called upon to move by the first engine. Thus one piston is 

 put in motion, proceeds on its stroke, actuates the valve of the other 



