CHAPTER XX 

 WATER WHEELS AND WINDMILLS 



131. Water Power. Every boy who has played in 

 a running stream or with a sprinkling hose knows that 

 swiftly flowing water has considerable force. It requires 

 much greater effort to row a boat upstream than to row 

 it downstream at the same rate. Water exerts a force 

 in the direction in which it flows and so resists objects 

 moving against the current and assists the movement of 

 objects which are going in the same direction as the 

 current. If a steamboat can go upstream six miles per 

 hour when the current is moving three miles per hour, the 

 same boat can go downstream at the rate of twelve miles 

 per hour. In this case it requires twice as much work 

 for the boat to go upstream as to go down the same 

 distance. To overcome the resistance of flowing water 

 is no small task in ocean and river commerce. The 

 captains of ocean liners aim to run their vessels with the 

 ocean currents as much as possible. 



Mountain streams and waterfalls can be made to develop 

 sufficient power to run mills, factories, and street cars, 

 to light the streets and homes, and even to 'heat build- 

 ings. Niagara Falls, the greatest cataract in the world, 

 is used by both the United States and Canada for the 

 development of power, mostly in the form of electricity. 

 Every pound of water in the Niagara River does about 

 150 foot pounds of work when it plunges over the falls. 

 The millions of pounds of water of the Niagara, if utilized, 



