54 



SCIENCE OF HOME AND COMMUNITY 



of the running water is used to compress air and this com- 

 pressed air forces water through the pipes. The ram may 

 pump the water from the brook that operates it, or it may 

 pump water from a separate source. The advantages are 

 that it is very cheap to operate and requires no one to attend 

 to it. Its disadvantages are that there may not be enough 

 fall of water or stream flow to operate it, and that the accu- 

 mulation of air in the summer and the formation of ice in 

 the winter may interfere with its operation. 



Windmill. Another cheap source of power is the wind- 

 mill. The wheel of the windmill is made of strong blades 



of wood or steel, curved or flat, 

 and set at such an angle that the 

 wind blowing against them causes 

 the wheel to rotate. The wheel 

 must be kept at right angles to 

 the wind in order to be turned by 

 it and it is kept in this position 

 by a fan-like tail which works 



like a weathervane. When it is 



Fie. , 7 . -Pneumatic tank. durable to stop the wheel, this 

 tail can be turned by means of a 

 wire so that it is parallel with the wheel, which then turns its 

 edges toward the wind and ceases to rotate. On the axle 

 is a cogwheel that fits into another cogwheel to which is fas- 

 tened a crank. This moves the piston of the pump at the 

 base of the windmill up and down. A serious objection to 

 the windmill is that the time of its operation cannot be con- 

 trolled. There may be long periods of calm, and a large 

 tank must be provided to allow for this possibility. Water 

 may be piped directly from the elevated tank to the house. 



An objection to the outdoor tanks in the northern states, 



by whatever method filled, is the danger of freezing during 



< severest weather. Tanks are sometimes placed in the 



attic of the house, but there is always the danger of leakage 



