86 FIRST YEAR COURSE IN GENERAL SCIENCE 



By digging or drilling to the underground water-level, it 

 is possible to bring water to the surface by its own pressure 

 or by pumps. Wells of one or the other of these types 

 furnish water for domestic and agricultural purposes in 

 many districts. 



Many springs and wells have a uniformly cool temperature 

 at all seasons. This is because the absorption and radiation 

 of heat by the earth change the temperature for only a short 



FIG. 36. FISSURE SPRING AND WELL 



If i is a layer impervious to water, the water which has passed through 

 the porous layers (p) must rest there, or follow down the inclined layer i. 

 A fissure through the upper layers may deliver the water at s. 1. Why is 

 such a spring usually a "bubbling" spring? 2. If a tube were sunk there, 

 how high might the water rise in it? (Make no allowance for friction.) 

 3. Would making a well at w have any effect upon the spring? 4. Is there 

 any better place for a well? Why? 



distance below the surface. The cooler the water of a spring 

 is in summer, the deeper one would have to go to find its 

 supply. 



94. Pressure in Liquids. As a diver descends below 

 the surface of water, he is conscious of a pressure which 

 steadily increases with the depth. If he is to remain some 

 time below the surface, he puts on a loosely fitting rubber 

 suit, provided with a metal helmet and a rubber tube through 

 which air can be forced down to him from above. It is 

 necessary to force the air down for two reasons: first, to 



