XL] GEOLOGICAL REFORM. 219 



However, I am not aware that such facts exist. As I have 

 already said, for anything I know, one, two, or three hundred 

 millions of years may serve the needs of geologists perfectly 

 well. 



III. The third line of argument is based upon the temperature 

 of the interior of the earth. Sir W. Thomson refers to certain 

 investigations which prove that the present thermal condition 

 of the interior of the earth implies either a heating of the earth 

 within the last 20,000 years of as much as 100 F., or a greater 

 heating all over the surface at some time further back than 

 20,000 years, and then proceeds thus : 



&quot; Now, are geologists prepared to admit that, at some time 

 within the last 20,000 years, there has been all over the earth 

 so high a temperature as that ? I presume not ; no geologist 

 no modern geologist would for a moment admit the hypothesis 

 that the present state of underground heat is due to a heating 

 of the surface at so late a period as 20,000 years ago. If that 

 is not admitted, we are driven to a greater heat at some time 

 more than 20,000 years ago. A greater heating all over the 

 surface than 100 Fahrenheit would kill nearly all existing 

 plants and animals, I may safely say. Are modern geologists 

 prepared to say that all life was killed off the earth 50,000, 

 100,000, or 200,000 years ago ? For the uniformity theory, the 

 further back the time of high surface-temperature is put the 

 better ; but the further back the time of heating, the hotter it 

 must have been. The best for those who draw most largely on 

 time is that which puts it furthest back ; and that is the theory 

 that the heating was enough to melt the whole. But even if 

 it was enough to melt the whole, we must still admit some 

 limit, such as fifty million years, one hundred million years, 

 or two or three hundred million years ago. Beyond that 

 we cannot go/ 1 , 



It will be observed that the &quot;limit&quot; is once again of the 

 vaguest, ranging from 50,000,000 years to 300,000,000. And 



1 Loc. cit., p. 24. 



