many of his "conjectures" and "guesses" 

 have been confirmed in later stages of the 

 progress of science is a striking proof of 

 his rare genius. He accepted the current 

 doctrine of the day regarding the existence 

 and nature of " subterraneous fires." 

 That doctrine has long been exploded. 

 The general high temperature of the 

 deeper parts of the earth's crust has been 

 proved by abundant evidence, though the 

 problem of the cause of this internal heat 

 cannot yet be regarded as solved. 



It seems not improbable that some of 

 the earthquakes in volcanic regions may 

 be produced, as Michell suggested, by 

 the sudden descent of quantities of sur- 

 face water upon the molten magma below. 

 Extinct craters are apt to become lakes or 

 tarns by gathering into their basins the 

 results of the atmospheric precipitation 

 of moisture. The sudden collapse of the 

 floor of one of these craters, filled in this 

 way, and the descent of a large body of 

 water upon molten lava below would 



35 



