of the Glaciers of the Alps. 107 



taken as a whole, are not stationaiy : going backwards many 

 centuries, we find, as a definitive result, that they encroach 

 slowly, and in the course of an age, upon the lower valleys. We 

 shall enter into some details, and cite some examples in sup- 

 port of this opinion, derived from notes made on the spots 

 last summer. 



The glacier of Aletsch, the largest of all, about 24 kilo- 

 meters* long, and 110 square kilometers of sui-face, forms a 

 mass approaching to 30 milliards of metrical cubes of ice ; 

 its direction is from north to south, its lateral expansion in 

 the course of ages pi'oduces very remarkable effects. 



On the left side, it is bounded by a chain of mountains 

 which is a continuation of the ^ggishorn. These mountains 

 are partly covered by a very dense forest of pines, and, for a 

 space of 4 kilometres of its length, measured from the ter- 

 minal talus upwards, the glacier ravages and destroys a great 

 number of these trees. The left lateral moraine reaches them, 

 and attacking them first by the roots, the tree falls, and is car- 

 ried along by the motion of the ice. Those which are caught 

 between the ice and the boundary rock are speedily torn in 

 pieces, while such as fall on the surface share in the general 

 movement, but are not long before being dragged under the 

 glacier. At the terminal talus we observe them issuing from 

 below the masses of ice, some half entangled, others com- 

 pletely free, the latter pushed forward and precipitated into 

 the torrent. All these trees are completely stripped of their 

 bark and torn, nothing remaining but the principal trunk and 

 some of the strongest branches crushed and twisted. 



With regard to the age of these pines, it may perhaps be 

 estimated at a minimum of 200 years; they are large, strong, 

 and thick, and it is well known that, in these elevated re- 

 gions, at the limit of arborescent vegetation, pines continue 

 many years before attaining a large diameter. There must, 

 therefore, have been a period of at least 200 years during 

 which the glacier did not reach the margin of the forest which 

 it now lays waste. 



If we pass from the left bank to the right, we also find proofs 

 of its dilatation. On a lateral piece of land, situate a little 



* Kiloinoter is equal to lOOSj yards. 



