ON GEOLOGICAL TIME. 63 



to o. In the second, by the analytical investiga- 

 tion of antecedents it is shown that the present 

 condition implies either a heating of the surface, 

 within the last 20,000 years of as much as 100 

 degrees, Fahr., or a greater heating all over the sur- 

 face at some time farther back than 20,000 years. 3 

 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 hypo- 

 thesis 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 ad- 

 mitted we are driven to a greater heat at some 

 time more than 20,000 years ago. A greater heat- 

 ing all over the surface than 100 degrees Fahr., 

 would kill nearly all existing plants and animals, I 

 may safely say. Are 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 farther back the time of high surface ternpera- 



1 Thomson and Tait, Appendix D. (j.) 



