1855.] SHARPE ELEVATION OF THE ALPS. 103 



sea, instead of 7000 or 8000, as in Switzerland." After referring to 

 an observation of M. Agassiz, that " the limit of the surfaces of fric- 

 tion coincide with the levels of ancient glaciers, above which only the 

 peaks of the higher mountains stood forth bare, or merely snow- 

 covered, but free from the abrading influence of moving ice,*' and 

 adding some remarks too long to quote, the author concludes, — 

 "adopting hypothetically, then, the theory of glaciers to account for 

 the singular configuration of the Norwegian rocks, it fits so far well 

 in its different parts as to explain plausibly the phsenomena ; and 

 whether correct or not, the analogy, on a great scale, of the line of 

 demarcation of the rugged summits and the abraded slopes of the 

 Norwegian and Swiss Alps, inclines us strongly to adopt a common 

 theory in explaining both*.*' 



In rambling over the Swiss Alps with Prof. Forbes' s remarks in 

 my mind, one of the subjects to which my attention was directed was 

 the much-disputed question of the extent to which glaciers had for- 

 merly reached ; and it was with this object in view that I first paid 

 attention to the upper limit of the erosion of the mountains ; but, as 

 all my observations led me to limit the action of ancient glaciers to a 

 degree which did not allow of considering them as the agents which 

 had produced the surfaces of erosion described, I was driven to look 

 elsewhere for an explanation. The traces of ancient glaciers seemed 

 to me to be confined to the valleys, and only to reach between 1000 

 and 3000 feet below the present glaciers j* ; but the traces of erosion, 

 up to a definite line, are seen not only on the higher snow-capped 

 mountains, but on detached hills in advance of the great chain, such as 

 the Mythen of Schwytz, and the hills which enclose the Lake of Thun, 

 which have their flanks rounded up to the height of 4700 or 4800 

 feet above the sea. For glaciers to reach to those heights would re- 

 quire a sheet of ice 3000 feet thick descending from the whole extent 

 of the Alps, and covering to nearly that height the plain between the 

 Alps and the Jura ; a supposition once thrown out by M. Agassiz 

 (* Etudes, &c.,' p. 304), but whicli found so httle favour that it is 

 not now worth combating. 



Moreover, though moving ice rounds away the projections on the 

 sides of the rocks with which it comes in contact, it is nowhere seen 

 to scoop out hollows in their sides. As soon as the surface of the 

 rocks has become pohshed, the ice can produce very little farther 

 effect upon them; its action tends to produce a uniform surface, not 

 an indented one. 



The action of water next suggested itself as the cause of the phse- 

 nomena in question : if the sea had stood for a long period at the 



* * Norway and its Glaciers visited in 1851, by James D. Forbes,' pp. 58 & 59 ; 

 and plate 2, which represents the mountains near the Folden Fiord, in illustra- 

 tion of the above remarks. 



t Many of the Swiss geologists are disposed to extend the ancient glaciers much 

 farther ; but they build their conclusions on the evidence of erratic blocks, which 

 belong to another set of operations of a period preceding that of the ancient 

 moraines. 



