4 STRUCTURE OBSERVED IN THE ICE OF GLACIERS. [1841. 



walk before my suspicion that it was a permanent and deeply- 

 seated structure was fully confirmed. Not only did we trace it 

 down the walls of the crevasses by which the glacier is inter- 

 sected, as far as we could distinctly see, but, coming to a great 

 excavation in the ice, at least 20 feet deep, formed by running 

 water, we found the vertical strata or bands perfectly well 

 defined throughout the whole mass of ice to that depth. An 

 attempt has been made to convey some idea of their appear- 

 ance in Plate L* Where the plane of vertical section was 

 eroded by the action of water, the harder seams of blue ice 

 stood protuberant ; whilst the intermediate ones, partaking of a 

 whitish-green colour and granular structure, were washed out. 

 We did not sleep that night until we had traced the structure 

 in all directions, even far above the position of our cabin, and 

 quite from side to side across the spacious glacier of the Finster 

 Aar. 



During the whole of our subsequent residence amongst the 

 glaciers, the phenomena and causes of this structure occupied 

 our thoughts very frequently. We had much difficulty in 

 arriving at a correct description of the manner of its occurrence, 

 and still more in forming a theory in the least plausible re- 

 specting its origin. 



Its importance, however, as an indication of an unknown 

 cause, is very great ; not only because all that can illustrate 

 what is so obscure as the manner of glacier formation and 

 movement, is so, but because it is precisely on this very point 

 of "What is the internal structure of the ice of a glacier?" 

 that the question now pending respecting internal dilatation 

 as a force producing progression, mainly hangs. Some con- 

 sider ice as compact, others as granular ; some as crystallized, 

 others as fractured into angular fragments ; some as horizon- 

 tally stratified, others as homogeneous ; some as rigid, others 

 as plastic ; some as wasting, others as growing ; some as ab- 

 sorbing water, others as only parting with it ; and yet no one 

 seems to have observed, or at least observed as an object of 



* [It has not been thought necessary to reproduce the figure.] 



