Prof. Hugi uii the Glaciers of'lhe Aljjs. 75 



ordinary abode of mists. Moreover, at an elevation of from 

 10,000 to 13,000 feet above the level of the sea, the clouds are 

 no longer discharged in great flakes of snow, as happens in an 

 atmospheric region lower and more charged with vapours. The 

 snow which falls in the high regions is always fine, dry, and 

 crystalline. I have observed this every time I have been over- 

 taken by snow, or found it newly fallen. In proportion as I re- 

 descended I saw the flakes, as also the mass of deposited snow, 

 increase even to the limit of the woods where it terminated. 

 We may also infer, from some indications, that the snow does 

 not appear at this altitude but during spring and autumn, and 

 not at all in winter. The greatest quantity is found, as I shall 

 state, at the limit of the forests ; thence it diminislies much 

 more towards the higher than the lower regions. These are 

 facts perfectly known to all tlie inhabitants of the mountains. 

 Thence it happens, that the thickness of glaciers of the first 

 kind, those which cover very high peaks, is so inconsiderable, 

 although, from their undergoing but very slight changes from 

 melting, they should increase enormously ; hence it happens, 

 that avalanches rarely or ever take place in high regions.'" 



Other authors have endeavoured to explain this progressive 

 movement of the glaciers by supposing, that the crevices or 

 rents which traverse them are again filled with water, and that 

 this water expanding, in the act of congelation, pushed forward 

 the masses of ice. The sim[)le inspection of the crevices de- 

 monstrates the futility of this hypothesis ; they generally pene- 

 trate even to the soil, and consequently cannot contain water. 

 Moreover, the movement takes place chiefly in the summer, 

 that is to say, at a period when the crevices are perfectly 

 open, and, besides, the crevices are far from extending from one 

 border of the glacier to the other. 



Others conjecture that the movement is caused by the expan- 

 sion of the ice of the glacier itself; but a more attentive exami- 

 nation of the nature of the crevices, and of the difl'erent pheno- 

 mena which accompany the movement, soon overthrows this 

 explanation. It is the same respecting that hypothesis on which 

 they account for the movement of the glaciers, by saying, that 

 they melt at their under surface, and that their weight is suHi- 

 licnt to make them descend to tiic lew regions. Entirely re- 



