SOME COMMON MECHANICAL MOTORS 563 



So long as the sun continues to pour its energy down upon the 

 earth, so long will evaporation continue to take place, the 

 rain will continue to fall, and running water will be available 

 to do work for mankind. The largest expense connected 

 with obtaining power from running water is the cost of con- 

 structing the necessary dams and installing the machinery of 

 the plant. This often requires a large outlay of capital. 

 The cost of producing the power after the plant is once in- 

 stalled is small. When man wishes to obtain power from 

 coal or petroleum, he must first raise them to the earth's 

 surface, and this requires much labor and expense. 



AVAILABLE WATER POWER OF THE UNITED STATES 



671. Amount of Water Power Available. The government 

 has estimated that there is sufficient available water power 

 in the United States, if it were utilized, to run every machine 

 in all our factories and mills, to propel all our railroad trains, 

 street cars, and automobiles, to light all our streets and 

 homes in fact to operate every machine in the United 

 States. Only about one-fifth of this power is, however, now 

 being utilized, the rest is running to waste. About 30,000,000 

 horse-power is now required in the United States for power 

 purposes. About 6,000,000 horse-power of water power has 

 thus far been developed. The use of water power is, how- 

 ever, growing rapidly. 



672. Distribution of Water Power. One of the principal 

 reasons why so small a portion of our available water power-has 

 been developed is the fact that generally water power can be 

 developed only in mountainous, or at least, in hilly regions. 

 Why? Most of the water power thus far developed is located 

 in New England, New York, and Pennsylvania; along the 

 Appalachian Mountains from Georgia northward; in Michigan, 

 "Wisconsin, and Minnesota; and along the Rocky and Sierra 

 Nevada Mountains in the west (Fig. 350). The largest 

 power plants in the United States are those at Niagara Falls 

 and on the Mississippi River at Keokuk, Iowa. Much of the 



