EXPLANATION OF THE PLATES. 341 



PLATE XIII. 



This plate represents a double acting steam engine for raising water, (art. 570, 582.) 



The steam from the boiler enters by the steam pipe S, passes through the top 

 valve a, to act on the piston p, and forces it down ; and just before it arrives at the 

 bottom of the cylinder, the plug on the rod R will come in contact with a lever, 

 and shut the valves a b, and open c d, which were shut ; the steam will now 

 continue its course down the pipe S through the valve d, act on the bottom of the 

 piston p, and again force it up to the top of the cylinder, while the steam which 

 forced it down will make its escape to the condenser B, through the valve b, by 

 a pipe which conveys the steam from the valves to the condenser. 



Having described one double stroke of the engine, it is only necessary to remark 

 that its continued motion is made of a repetition of the same thing over again. The 

 steam which passes to the condenser B meets with a jet of cold water from the 

 injection cock I, and the greater part of it is reduced to the state of water, and it 

 is the office of the air pump A to clear it away. The rod R works the air pump 

 which draws out all the injected water, air, and condensed steam, and discharges 

 it through the valve at the top of the air pump into the hot well, where a certain 

 portion of the water is again forced back to the boiler by the force pump L, and 

 the remainder runs to waste : at the same time, to the other end of the great beam 

 is attached the rod of the cold water pump N, which supplies the cistern containing 

 the condenser and air pump with cold water ; and from this source the injection 

 cock has its supply. 



The governor Q is put in motion by beveled wheels on the shaft of the fly 

 wheel P, (art. 54^0.) and regulates the throttle valve in the steam pipe S, so as to 

 close it a little for a less admission of steam when the speed is increasing ; and on 

 the contrary, when the engine relaxes in its speed, the balls will again begin to 

 fall, and open it a little so as to admit more steam ; by this means the work may 

 vary, and yet a uniform motion be kept up by the engine, (art. 550.) 



In the pumping apparatus, the rod M is the pump rod for the purpose of raising 

 water ; when the rod descends, the water will be forced through G into the upper 

 air vessel E, from whence it passes in a continued stream to the reservoir, at a 

 distance and height proportional to the power of the engine. The barrel of the 

 pump will be refilled from F, the source which communicates with the lower air 

 vessel H ; when the rod rises, the opposite valve at the top will open, and the water 



