1842.] GLACIERS NOT STATIONARY IN WINTER, 25 



M. Rendu may not avail something, I am unable to say, not yet 

 having been able to procure his work. 



It yet remains to decide, what is the cause of the succession 

 of dirt-bands at considerable distances on the surface of the 

 glacier, indicating the succession of waves of more or less com- 

 pact ice. In all the glaciers where I have yet distinctly 

 observed them, they appear to follow a regulated order of dis- 

 tances, nearly the same for a considerable space, but closer the 

 farther we ascend the glacier. I cannot help thinking that 

 they are the true annual rings* of the glacier, which mark its 

 age, like those of a tree, only increasing instead of diminishing 

 in breadth as the ice grows older, coinciding again with the fact 

 which I formerly established, that the higher part of a glacier 

 moves, generally speaking, more slowly than its lower extremity. 

 The different states of the glacier at different seasons, the 

 presence or absence of snow, or even the simple difference of 

 velocity at different seasons, would be sufficient to account for 

 this alternation of structure. There is no cause so likely to 

 produce it as some annual change. I may add, that ^some 

 observations which I have already made on the distances of 

 these bands, as well as information which I have endeavoured 

 to collect, lead me at least to have some doubt as to the correct- 

 ness of the opinion generally entertained, that the glaciers are 

 stationary in winter, perhaps even, that there is any very great 

 inequality in their march at different times of the year. I am, 

 my dear Sir, yours very truly. 



* [Originally printed annular rings, by a typographical error. See Editor's 

 Note, Edin. New Phil. Journal, April 1843, p. 382.] 



