520 WITHIN THE EARTH'S CRUST 



or crude oil as it is generally called, many different products 

 are obtained, among which are gasoline, kerosene, benzine, 

 paraffin, and various lubricating oils. 



The crude oil itself is burned in many sections to produce 

 heat and power. For many purposes it is better than coal, 



OIL WELLS 

 Tapping the rock layers containing petroleum. 



since the same amount of fuel can be carried in less space. 

 The supply of oil seems to be even more limited than that 

 of coal, but it has been wasted at times fully as recklessly. 

 In the interest of future generations, both coal and oil 

 should be more carefully conserved. 



SUMMARY 



Many excavations and borings into the earth's crust have 

 shown that temperature increases with depth. If it were 

 not for the tremendous pressure of outside layers of matter, 

 the heat at the interior of the earth would probably cause 

 the matter there to be in a molten condition. If from 



