236 GREENHOUSES 



Double-acting rams which. will utilize the 

 water from a creek or river as power and 

 pump water from a spring or shallow well 

 may be had, but they are somewhat more 

 complicated. 



Windmills for Pumping. The chief ob- 

 jection to the windmill for pumping is its lack 

 of dependability. Where the wind is fairly 

 constant, or when a large storage capacity 

 may be had cheaply, windmills are the cheap- 

 est source of power. On the average the 

 windmills used for pumping develop about 

 three-fourths horse-power. The geared steel 

 wheel mills are more efficient and will run 

 in lighter winds than will the wood wheel 

 mills. 



Storage Tanks. Storage tanks are neces- 

 sary with most water systems, to insure a 

 constant supply and to furnish pressure. 

 They fall naturally under two heads: (i) 

 Open tanks in which pressure is obtained by 

 gravity; (2) closed tanks, usually pneumatic 

 tanks, containing air into which water is 

 forced, the compressed air in this case furn- 

 ishing the desired pressure. 



In placing tanks in the attic, or other ele- 

 vated positions, it is well to keep in mind the 



