AND GLACIERS 341 



From these indications, geologists have been able to prove 

 that the glaciers of Chamouni, of Monte Rosa, of the St. 

 Gotthard, and the Bernese Alps, formerly penetrated 

 through the valley of the Arve, the Rhone, the Aar, and 

 the Rhine to the more level part of Switzerland and the 

 Jura, where they have deposited their boulders at a height 

 of more than a thousand feet above the present level of the 

 lake of Neufchatel. Similar traces of ancient glaciers are 

 found upon the mountains of the British Islands, and upon 

 the Scandinavian Peninsula. 



The drift ice too of the Arctic Sea is glacier ice; it is 

 pushed down into the sea by the glaciers of Greenland, 

 becomes detached from the rest of the glacier, and floats 

 away. In Switzerland we find a similar formation of drift- 

 ice, though on a far smaller scale, in the little Marjelen See, 

 into which part of the ice of the great Aletsch Glacier 

 pushes down. Blocks of stone which lie in drift-ice may 

 make long voyages over the sea. The vast number of blocks 

 of granite which are scattered on the North German plains, 

 and whose granite belongs to the Scandinavian mountains, 

 has been transported by drift-ice at the time when the 

 European glaciers had such an enormous extent. 



I must unfortunately content myself with these few refer- 

 ences to the ancient history of glaciers, and revert now to 

 the processes at present at work in them. 



From the facts which I have brought before you it results 

 that the ice of a glacier flows slowly like the current of a 

 very viscous substance, such for instance as honey, tar, or 

 thick magma of clay. The mass of ice does not merely flow 

 along the ground like a solid which glides over a precipice, 

 but it bends and twists in itself; and although even while 

 doing this it moves along the base of the valley, yet the 

 parts which are in contact with the bottom and the sides 

 of the valley are perceptibly retarded by the powerful fric- 

 tion ; the middle of the surface of the glacier, which is most 

 distant both from the bottom and the sides, moving most 

 rapidly. Rendu, a Savoyard priest, and the celebrated natural 

 philosopher Forbes, were the first to suggest the similarity 

 of a glacier with a current of a viscous substance. 



Now you will perhaps inquire with astonishment how; it is 



