VI 



Agassis 273 



to those now being scratched on the rocky floors of the 

 modern glaciers, and he inferred that the polished and 

 striated rocks of the Jura, even though now many leagues 

 from the nearest glacier, must have acquired their peculiar 

 surface from the action of ice moving over them, as modern 

 glaciers slide upon their beds. He was thus led to con- 

 clude that the Alpine ice, now restricted to the higher 

 valleys, once extended into the central plain, crossed it, and 

 even mounted to the southern summits of the Jura chain. 



Before Agassiz took up the question, there were two 

 prevalent opinions regarding the transport of the erratics. 

 One of these called in the action of powerful floods of 

 water, the other invoked the assistance of floating ice. 

 Agassiz combated these views with great skill. His 

 reasoning ought to have convinced his contemporaries 

 that his explanation was the true one. But the conclu- 

 sions to which he was led seemed to most men of the day 

 extravagant and incredible. Even a cautious thinker like 

 Lyell saw less difficulty in sinking the whole of Central 

 Europe under the sea, and covering the waters with floating 

 icebergs, than in conceiving that the Swiss glaciers were 

 once large enough to reach to the Jura. Men shut their 

 eyes to the meaning of the unquestionable fact that, while 

 there was absolutely no evidence for a marine submergence, 

 the former track of the glaciers could be followed mile 

 after mile, by the rocks they had scored and the blocks 

 they had dropped, all the way from their present ends to 

 the far-distant crests of the Jura. 



Agassiz felt that the question was connected with large 

 problems in geology. The former vast extension of the 

 Swiss glaciers could be no mere accidental or local pheno- 



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