MODERN GEOLOGY 



the same time, their number indicates so many stop- 

 ping-places in the retreat of the glacier, or so many ex- 

 treme limits of its extension limits which were never 

 reached again after it had retired. I insist upon this 

 point, because if it is true that all these moraines de- 

 monstrate a larger extent of the glacier, they also prove 

 that their retreat into their present boundaries, far 

 from having been catastrophic, was marked on the 

 contrary by periods of repose more or less frequent, 

 which caused the formation of a series of concentric 

 moraines which even now indicate their retrogression. 

 "The remains of longitudinal moraines are less fre- 

 quent, less distinct, and more difficult to investigate, 

 because, indicating as they do the levels to which the 

 edges of the glacier reached at different epochs, it is 

 generally necessary to look for them above the line of 

 the paths along the escarpments of the valleys, and 

 hence it is not always possible to follow them along a 

 valley. Often, also, the sides of a valley which en- 

 closed a glacier are so steep that it is only here and 

 there that the stones have remained in place. They 

 are, nevertheless, very distinct in the lower part of the 

 valley of the Rh6ne, between Martigny and the Lake 

 of Geneva, where several parallel ridges can be ob- 

 served, one above the other, at a height of one thou- 

 sand, one thousand two hundred, and even one thou- 

 sand five hundred feet above the Rh6ne. It is between 

 St. Maurice and the cascade of Pissevache, close to 

 the hamlet of Chaux-Fleurie, that they are most ac- 

 cessible, for at this place the sides of the valley at dif- 

 ferent levels ascend in little terraces, upon which the 

 moraines have been preserved. They are also very 



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