REVOLUTIONS OF CLIMATE. 411 



theory is not only hypothetical, but incompetent 

 to explain the phenomena. 



There is nothing so remarkable in the natural 

 history of our planet, as the great revolutions of 

 climate and organic life which it has undergone 

 during the countless ages of the past. The most 

 fertile imagination never conceived anything so 

 wonderful as the varied scenes which the surface 

 of the earth has exhibited during different epochs, 

 before it was inhabited by man, or any of the 

 higher orders of animals. The rationale of these 

 mutations is by far the most comprehensive and 

 important problem in geology ; for it involves the 

 whole theory of organic life, and its immediate 

 relation to the vast science of physical astronomy. 

 The leading facts hitherto discovered, may be 

 reduced to the following general propositions : 



1. That throughout the northern hemisphere, 

 from the shores of the Mediterranean to the north 

 of Europe and Asia, and from the southern 

 United States to Melville Island, in lat. 75 N. 

 the transition, secondary, and tertiary formations 

 are filled with the fossil remains of plants and 

 animals, which could have existed only in a uni- 

 formly warm climate, analogous to that of our 

 present tropics : 



2. That at different epochs, the land and sea 

 were inhabited by totally different orders, genera, 

 and species of organized beings, which succes- 

 sively arose, flourished for a time, and then 

 gradually passed away, leaving only their pet- 



