GROWTH OF GEOLOGY. 261 



rocks beneath them to powder, striating and polish- 

 ing the immovable ; but when the Alps had been up- 

 heaved, the surface of the earth was warmed anew, 

 the ice melted, erosion valleys were formed, erratic 

 blocks were left stranded, and so on. 



Along with much truth, there was also much 

 fancy and exaggeration in this theory, and the un- 

 wholesome taint of catastrophism was especially dis- 

 tinct in his assumption of successive ages of low tem- 

 perature at the close of the various geological periods. 



Charpentier's Essai sur les Glaciers (1841) was 

 more thoroughly scientific than the work of Agassiz. 

 Von Zittel speaks of its precision recalling that 

 of de Saussure, of its thoroughness, of its basis in 

 original observations. He questioned Agassiz's 

 theory of one great northern ice-sheet, older than the 

 Alps, but pictured rather a great extension of pres- 

 ently existing glaciers, thus reacting to an opposite 

 extreme. In subsequent works, Agassiz modified 

 some of his views in deference to Charpentier, and 

 as the result of his own extended experience in 

 Scotland and in America. 



According to Agassiz the Swiss glaciers must once 

 have been large enough to reach to the Jura, a con- 

 clusion that seemed to many of his contemporaries an 

 incredible extravagance. As Sir Archibald Geikie 

 notes, " 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." ..." Men shut their eyes to the mean- 

 ing 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 



