Glaciers of the Alps. 77 



stlow. From this contrast between the dry state of the'iipper 

 and the moist state of the lower surface, results, in my opinion^ 

 the disproportion which exists in the melting of the two surfaces. 



This, however, is the mode in which M. Hugi explains the 

 progressive movement of the glaciers. According to him, a gla- 

 cier of the second kind is produced under this form, not at the 

 place where it is found, but in high regions, under a form of a 

 glacier of the first kind ; then, by the gradual development of 

 its mass, it descends to the low regions, in which it attains the 

 last state of its constitution, and terminates by decomposition. 

 Let us pursue with our author the progress of this metamor- 

 phosis. 



" The snow which falls in the elevated regions,'"'' says he, " is 

 very different from that which falls below the limit of glaciers of 

 the first kind, and which traverses an atmosphere denser and 

 more surcharged with vapours, in a word, less pure than that of 

 the high regions. This last snow appears to be in some degree 

 more aqueous, while the first, more crystalline and purer, is of 

 a dry and light nature. This, when the temperature rises, 

 seems to evaporate rather than melt, which is owing to the pre- 

 sence of air in its composition, and above all, to the aridity and 

 levity of the atmosphere in the regions where it is deposited. 

 The truth is, that the remainder of the snow of the high i-eo-ions, 

 without becoming fluid, agglomerates under the form of groins ; 

 this agglomeration operates in a slow and irregular manner at 

 the height of 13,000 feet ; at 11,000 feet the grains are better 

 formed ; at 9000 feet they begin to be half melted. The ora- 

 nulated mass thus formed is exposed during the summer to con- 

 tinual changes of temperature. The very keen cold of the niojit 

 renders it so firm that the foot does not make any impression on 

 it, and that it follows -the same laws of expansion as the ice pro- 

 perly so called ; the intense heat of the day separates anew what the 

 night has bound together. The grains are loosened, the rain pe- 

 netrates into the interstices which are formed, and this water en- 

 larges each grain by congealing around it. This alternate ef- 

 fect of day and night, and the modifications which result from 

 it, reproduce themselves on a greater scale, and in a manner 

 more conspicuous, by the succession of opposite seasons. I'he 

 result is a state of increasing tension through the mass. EacU 



