122 ICE AND GLACIERS. 



are usually changed into wonderfully shaped sharp ridges 

 and pyramids, and from time to time fall into the inter- 

 jacent crevasses with a loud rumbling noise. Seen from a 

 distance such a place appears like a wild frozen waterfall, 

 and is therefore called a cascade ; such a cascade is seen in 

 the Glacier du Talefre at 1, another is seen in the Glacier 

 du Geant at g, Fig. 14, while a third forms the lower end 

 of the Mer de Glace. The latter, already mentioned as 

 the Glacier des Bois, which rises directly from the trough 

 of the valley at Chamouni to a height of 1,700 feet, the 

 height of the Konigstuhl at Heidelberg, affords at all 

 times a chief object of admiration to the Chamouni tourist. 

 Fig. 18 represents a view of its fantastically rent blocks 

 of ice. 



We have hitherto compared the glacier with a current 

 as regards its outer form and appearance. This similarity, 

 however, is not merely an external one : the ice of the 

 glacier does, indeed, move forwards like the water of a 

 stream, only more slowly. That this must be the case 

 follows from the considerations by which I have en- 

 deavoured to explain the origin of a glacier. For as the 

 ice is being constantly diminished at the lower end by 

 melting, it would entirely disappear if fresh ice did not 

 continually press forward from above, which, again, is 

 made up by the snowfalls on the mountain tops. 



But by careful ocular observation we may convince 

 ourselves that the glacier does actually move. For the 

 inhabitants of the valleys, who have the glaciers constantly 

 before their eyes, often cross them, and in so doing make 

 use of the larger blocks of stone as sign posts — detect 

 this motion by the fact that their guide posts gradually 

 descend in tlie course of each year. And as the yearly 

 displacement of the lower half of the Mer de Glace at 

 Chamouni amounts to no less than from 400 to 600 feet, 

 you can readily conceive that such displacements must 



