CHAPTER DC 

 WATER-POWER AND STEAM-POWER 



The power of falling water has long been used by man 

 to do various kinds of work. The grinding of grain was 

 one of the most tiresome of early occupations. No wonder 

 that some tired grinder put his wits to work to find a way 

 of getting out of this endless job. Grain was ground in 

 ancient times between stones, as it is even to-day in some 

 primitive countries. So the grinding together of stones 

 by a waterfall may have been the thing that suggested 

 having the water do this work. Water-wheels were de- 

 vised, and set up in places where falling water could be 

 easily diverted to run over them. Dams were built to 

 impound the water and make its flow over the water-wheel 

 constant. The revolving shaft of the water-wheel turned 

 the grinding stones of the early mills (see Fig. 30). 



Many American cities are where they are because they 

 grew up around old mills. Along the Connecticut River 

 in New England there are many manufacturing cities. 

 They are there simply because the many falls and rapids 

 of the river furnish the power which runs their mills. 

 To-day, however, men have learned to transform water- 

 power into electric power, and thus to transmit it over wires 

 to cities many miles away. So mills no longer need to 

 be near the falling water which furnishes power to operate 

 their industries. Niagara Falls is the source of the power 

 that runs the street-cars of cities hundreds of miles away. 

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