Water Power 



71 



Then remove the plugs and compare the force with which the water 

 runs out of the lowest hole with that of the water running 

 out of the others. What does this indicate? Adjust a rub- 

 ber inlet tube so that as much 

 water flows into the can as 

 flows out through the holes. 

 In this way the level of the 

 water in the can always stays 

 the same. Catch in separate 

 cups the water from two or 

 three of the holes. The quan- 

 tities of water caught will give 

 an approximate measure of 

 the pressures exerted. It will 

 be found that if the depth 

 below the surface is three 

 times as great at one opening 

 as at another, the pressure is 

 three times as great at that 

 opening as at the other, and if 

 the depth is four times as 

 great, the pressure is four 

 times as great. 



Water Wheels. The his- 

 tory of the development of 

 industry in all countries shows 

 that running and falling water 

 have long been used to provide 

 power and to do work for the 

 benefit of man. Various forms 

 of wheels have been invented 

 to utilize the force exerted 

 by water. These wheels, in 



turn, drive machinery used for AN APPARATUS TO SHOW WATER 



PRESSURE 

 many purposes. 



The efficiency of a water wheel depends not alone on the volume 

 of water which flows against it, but also on the height from 



