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THE POPULAR SCIENCE MONTHLY. 



small amounts at a time. In the steam-engine, large or small, the whole 

 body of water is exposed to the action of the fire, and a considerable 

 (juantity of steam is constantly generated. In this, small quantities of 

 water are successively forced from a reservoir through coils of highly 

 heated tubing, and there flashed into steam. A force-pump driven by 

 the engine continually supplies water to the reservoir. The relation of 

 the different parts of the apparatus to each other, and the working of 

 the system, are clearly shown in Fig. 6. The long tubing, in which the 

 water is converted into steam, leads from the air-chamber to the steam- 

 chest of the engine. It is coiled first in a receptacle through which 

 the exhaust steam passes, and then in the generator, where it is as com- 

 pletely as possible exposed to the action of the fire. In starting the 

 engine, the fly-wheel is turned by hand, so as to produce a pressure in 



Fig. 7. 



the air-chamber. This forces the water into the coil, where it is rap- 

 idly converted into steam, and delivered in the steam-chest at the pres- 



g, It 



sure furnished by the pump. When the engine begins runnin 

 drives the pump and maintains the pressure. If the engine is stopped 



