68 Our Surroundings 



Water turns to vapor because of the heat energy that comes 

 to it from the sun. This energy causes the water molecules to 

 separate and thus to form a vapor. This vapor rises into the 

 atmosphere and, if dense enough, forms clouds. When these are 

 further condensed water falls as rain. Some of it falls on hillsides 

 and higher levels and finds its way into streams. As it flows 

 down the hillside or leaps over the cliffs, the water is giving off 

 some of the energy that the sun stored in it in vaporizing it and 

 lifting it to the clouds. If, instead of flowing freely in its fall 

 to lower levels, it is made to exert pressure on a water wheel, 

 some of the energy is transformed and made available for the use 

 of man. 



In this country, and throughout the world, only an exceedingly 

 small part of the available energy of water power in streams has 

 yet been utilized. Only a small fraction of the energy stored in 

 the falls and rapids of Niagara is turned to useful purposes. 

 Engineers are now at work on plans to utilize some of the 

 power stored in the great tides of the North Atlantic. There 

 is more than enough of such power for all industrial needs. 

 Moreover, scientists and engineers are constantly improving 

 methods of conveying electricity long distances. Conse- 

 quently, by changing water power to electric energy, it is 

 possible to transport it to the points where it is needed. 

 Water power is undoubtedly the great power of the immediate 

 future. 



Water Power in the United States. New England, New 

 York, Pennsylvania, Michigan, Wisconsin, Minnesota, Iowa, and 

 some states farther west have developed large amounts of water 

 power, but there is much more available even in these sections. 

 The largest power plants in the country are at Niagara Falls, 

 New York; Keokuk, Iowa; and Big Creek, California. 

 The plant at Muscle Shoals, in Alabama, when fully de- 

 veloped, will probably be greater than these. The desira- 

 bility of developing water power is apparent when the fact is 

 known that it costs on the average only about one-half as 

 much to generate power by water as it does by the burning of 

 coal. 



