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CHAPTER I. 



THE FAILUEE OF ATTEMPTS TO ACCOUNT FOR SECULAR 

 CHANGES OF CLIMATE. 



Most important Problem in Terrestrial Physics. — Early Attempts to 

 explain Geological Climate. — Lyell's Theory. — Theory of Change 

 in Obliquity of Ecliptic. — Theory of Change in Axis of Rotation. — 

 Tendency in Geology to Cataclysmic Theories. — The True Theory 

 not Cataclysmic. — An Important Difference. 



The most important problem in terrestrial physics, in 

 so far as regards geological and palseontological science, 

 and the one which will ultimately prove the most far- 

 reaching in its consequences, is, What are the physical 

 causes which led to the Glacial Epoch and to all those 

 great secular changes of climate which are known to 

 have taken place during geological ages ? How are we 

 to account for the cold and Arctic condition of things 

 which prevailed in temperate regions during what is 

 called the Glacial Epoch, or for the warm and temperate 

 climate enjoyed by the Arctic regions, probably up to 

 the Pole, during part of the Miocene and other periods ? 

 Theories of the cause of those changes, of the most 

 diverse and opposite character, have been keenly advo- 

 cated, and one important result of the discussions which 

 have recently taken place is the narrowing of the field 

 of inquiry and the bringing of the question within 

 proper limits. 



The warm character of the climate of former ages 

 was at one time generally referred by geologists to the 

 influence of the earth's internal heat. But it was soon 



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