C. B WARRING. 103 



whole matter to Infinite power. If that is allowable, the 

 case becomes simple enough. 



The second objection which was mentioned is a very 

 serious one, and, if it could not be answered, would re- 

 quire us to give up all hope of at present solving the 

 problem of geological climate. 



It is true that, under present conditions polar re- 

 gions would be colder than they now are if the earth's 

 axis was perpendicular, because, as has been shown by 

 Mr. Meech, a smaller number of solar rays would fall 

 during the year upon each unit of polar surface. But 

 temperature depends far more upon the amount of heat 

 retained than upon the amount received. And in this 

 lies the explanation. 



Professor Tyndall, in Heat, a Mode of Motion, has 

 shown that many gases and vapors permit solar heat to 

 pass freely through them, while they largely intercept 

 heat from bodies of a low temperature ; and that some 

 other gases, notably oxygen and nitrogen, whose mix- 

 ture forms almost all the atmosphere, allow both kinds 

 of heat to pass through them with almost equal freedom. 

 Carbonic acid and aqueous vapor belong to the first 

 class. 



All the carbon in the coal, lignite, petroleum, and 

 other animal and vegetable substances in the earth's 

 crust, once existed as carbonic acid, and formed a much 

 larger part than at present of the atmosphere, — and, by 

 retaining the heat, raised the temperature. This, in its 

 turn, increased the capacity of the air for moisture. 

 The aqueous vapor taken up acted in the same sense, 

 and thus the earth was covered from pole to pole by "a 

 warm blanket." 



It was also shown by Professor Tyndall that when the 

 amount of CO 2 was large, successive increments produced 

 comparatively little effect upon the diathermanicity ; 

 but that when the amount became small, the effect upon 



