3 I2 



THE POWER BEHIND THE ENGINE 



Water wheels. In Figure 183 the water of a small but rapid 

 mountain stream is made to rotate a large wheel, which in turn 



communicates its mo- 

 tion through belts to 

 a distant sawmill or 

 grinder. In more level 

 regions huge dams are 

 built which hold back 

 the water and keep it at 

 a higher level than the 

 wheel; from the dam 

 the water is conveyed 

 in pipes (flumes) to the 

 paddle wheel which it 

 turns. Cogwheels or 

 belts connect the pad- 

 dle wheel with the factory machinery, so that motion of 

 the paddle wheel insures the running of the machinery. 

 One of the most efficient forms of water wheels is that shown 

 in Figure 184, and called 

 the Pelton wheel. Water 

 issues in a narrow jet 

 similar to that of the or- 

 dinary garden hose and 

 strikes with great force 

 against the lower part of 

 the wheel, thereby causing 

 rotation of the wheel. 

 Belts transfer this motion 

 to the machinery of the 

 factory or mill. 



FIG. 183. A mountain stream turns the wheels 

 of the mill. 



FIG.- 184. The Pelton water wheel. 



Windmills. Those of us who have spent our vacation 

 days in the country know that there is no ready-made water 



