DEPTH OF ZONE OF FLOW IN THE EARTH’S CRUST 99 
case treated by Hoskins, certain assumptions must be made and 
the result obtained varies widely with these assumptions. Conse- 
100°C 300°c 500C 700°C 
10,000 lbs. 30,000 lbs. 50,000.1bs. 70,000 lbs. 
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Fic. 1.—Showing the Pressures and Temperatures which are believed to exist 
within the Earth’s Crust at successive depths to a distance of thirteen miles from the 
the surface. The temperatures are expressed in degrees Centigrade and the pressures 
in pounds per square inch. (see pp. 98 and 110). 
quently, the figures obtained by Hoskins have not behind them 
the weight of a mathematical certainty. They are founded on 
