20-1 Dr Martens on the Glaciers of Spitsbergen. 



upper glaciers, we may establish a new analogy between the 

 Mers de Glace and those of Spitzbergen.* 



The weight of the ice must necessarily draw the glaciers 

 toward the lower parts, and it acts the more powerfully dur- 

 ing summer, because nothing is then opposed to the progres- 

 sion of these lower parts. The freezing of the water in the 

 crevices is still another force of great power, as we have seen 

 above. 



Without having recourse to any hypothesis, the following is 

 my conception of the manner in which a glacier advances : — 

 In summer immense transverse crevices divide its entire mass 

 vertically into so many secondary wedge-shaped masses ; 

 consequently its surface is increased by the sum of all the 

 spaces which the crevices leave between them at their upper 

 part. The glacier resting firmly against the mountain can- 

 not be pushed backward ; it is, therefore, at its lower part, 

 when nothing arrests it, that it becomes displaced, and moves 

 forward. Winter following, these crevices are filled with 

 snow blown into them by the wind, or falling in the form of 

 avalanches. This snow becomes ice under the alternate in- 

 fluences of melting and freezing during the months of May, 

 Juno, September, and October. In the succeeding summer 

 new crevices are formed, the glacier advances, and so on suc- 

 cessively. This progression, therefore, is neither a slipping nor 

 a sinking (both of which it is difficult to admit, since the ice 

 must adhere to the ground), but a successive dismemberment. 

 A comparison will, perhaps, render my idea more intelligible : 

 If we place a portfolio with compartments on its back, and 

 rest one of its sides against some obstacle, such as a wall, 

 we cannot open it but by advancing the opposite side, which 

 is alone moveable. The obstacle is the amphitheatre of 

 mountains which bounds and arrests the glacier on the land 



* M. Biscliof even tries to prove from reasoning, experiments, and facts, 

 that the central heat of the earth has no share in the melting of glaciers in 

 general, and that the streamlets which flow from them are formed by the 

 springs which rise under the glaciers, and are increased by melting the ice 

 in contact with them. This would explain in another manner why those 

 of Spitzbergen do not produce streams, because no one has ever observed 

 springs in that island. 



