118 Charpentier's Essay on Glaciers. 



of lateral valleys proceeding from mountains of sufficient ele- 

 vation to be still covered with glaciers. Thus the valley of 

 the Rhone receives 32 of these lateral valleys : 



The ralley of the Rhine 



18 



11 



8 



7 



7 

 2 



Reuss, . . 



Arve, . . 



Aar, . . 



Limmat, . 



Sarine, . . 



and it is found, in point of fact, that the erratic formation of 

 the valley of the Rhone is most extended, and that of the 

 Sarine least so. 



Lastly, the effect produced even in the present day by gla- 

 ciers on the rocks which form their beds, renders it easy to ac- 

 count for the marks of wear and friction presented by the 

 rocks in the neighbourhood of erratic debris. But we must 

 beware of supposing that all polished rocks have been ren- 

 dered so by glaciers ; and M. de Charpentier cannot, for ex- 

 ample, admit that the famous polished rock of the Col de la 

 Fenetre, near the Great St Bernard, is the result of the fric- 

 tion of a glacier, as M. Agassiz seems to think. He ascribes 

 it, as was done by Saussure, and more recently by M. 

 Leonhard, to the friction of the masses against each other, 

 and to a kind of vitrification consequent upon that friction. 



Now it will be asked of M. de Charpentier, how he can ex- 

 plain the existence of a climate fit to give the diluvial gla- 

 ciers of the Alps the gigantic development of that of the 

 Rhone, for example, which was of such breadth as to cover 

 all that part of Switzerland between Soleure and Geneva, 

 and must have been sixty leagues long. He is of opinion 

 that, although it may be impossible for him to reply and as- 

 sign a probable cause for this great climateric change, we 

 ought not on that account to reject his hypothesis, if in other 

 respects it affords a good explanation of all the facts, just 

 as we have not disclaimed the theory of soulevements, al- 

 though we are ignorant of their cause. But he thinks he 

 can account for the long series of cold and rainy seasons ne- 

 cessary to the development of diluvial glaciers, from the very 

 consequences of the last elevation of the Alps which imme- 



