M. Agassiz oji Glaciers, Moraines, and Erratic BlocTcs. 377 

 now sometimes admitted, is so contrary to every physiological 

 idea, that it must be strenuously repelled, to make way for 

 another, viz. that there has been a diminution of temperature, 

 which has been accidental in relation to the development of the 

 organized beings that have appeared and disappeared one 

 after the other at determinate epochs, maintaining itself at a 

 particular mean temperature during a given era, and diminish- 

 ing at certain fixed epochs. 



As the development of individual life is always accompanied 

 with that of heat, since its continuance establishes a certain 

 equilibrium of longer or shorter duration, and since its extinc- 

 tion produces an icy coldness, I conceive I deduce only legiti- 

 mate inferences, when I conclude that the same phenomena oc- 

 curred upon the globe : that the earth, when it was formed, ac- 

 quired a certain very elevated temperature, which progressive- 

 ly diminished during the different geological formations ; that 

 during the continuance of each of them, the temperature has 

 not been more variable than that of our globe since it has been 

 occupied by its present inhabitants, but that it has been at the 

 epochs of the disappearance of these inhabitants that a fall in 

 the temperature has taken place, and that this fall has been 

 beneath the temperature which prevailed in the subsequent 

 epoch, and which re-appeared with the development of the 

 newly animated creatures which were called into existence. 



If this theory be correct, and the facility with which it explains 

 so many phenomena which have hitherto been deemed inexpli- 

 cable, induces me to believe that it is ; then it must follow that 

 there has been, at the epoch which preceded the elevation of 

 the Alps and the appearance of the existing animated world, 

 a fall of temperature far below that which prevails in our days. 

 It is to this fall of temperature that we must attribute the for- 

 mation of those immense masses of ice, which must universally 

 have covered the surface, where we find these erratic blocks 

 along with rocks which are polished as are ours. It is also, 

 unquestionably, this extreme cold which has enveloped the 

 Siberian mammoths in ice, has congealed all our lakes, and 

 accumulated the ice as high as the ridges of our Jura, which 

 existed before the elevation of the Alps. 



