The Interior of the Earth 



No doubt it would be possible to sink borings 

 to depths where the temperature would exceed 

 that of boiling water, but that is not the question. 

 Whatever the temperature the amount of heat 

 available for use could never exceed the supply 

 derived from the central regions. Thus it follows, 

 from the figure given above for that amount, that 

 to develop ten horse power with a steam engine 

 of average efficiency supplied with steam by the 

 terrestrial furnace all the heat passing through 

 something like half a square mile of the earth's 

 crust would have to be intercepted. 



While we know beyond doubt that the earth 

 is cooling, it would be equally interesting to 

 determine the law of the rise of temperature 

 in its interior. Here we must leave all hope of 

 certainty and be satisfied with probabilities. 

 Our facts take us no deeper than one mile and a 

 quarter; beyond that we can only proceed by 

 induction. But the probability of this induc- 

 tion depends on the reliability of the observa- 



pass before the supply showed any signs of decrease." The 

 great chemist did not look on this as a mere fancy, because 

 this same idea of obtaining energy, cost free, from the earth's 

 central heat reappears in a more recent publication (Science et 

 Libre Penste, p. 192). 



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