ACTION OF THE GLACIER. 165 



lower down we find that the process, on account of the larger 

 amount of moisture, becomes gradually more complete, until, 

 at the lower end of the glacier, we find that the ice is as solid 

 as frozen water. But no part of the glacier is the result of the 

 freezing of water, as such ; it is the result of the slow transfor- 

 mation of snow into ice by the process just explained. 



Now, while the loose snow resting upon the rocks fourteen 

 thousand feet above the level of the sea is brought down by its 

 own weight, (the direction of which is determined by the slope,) 

 it produces no mechanical action, in consequence of its loose- 

 ness ; it only gradually comes down. As soon, however, as the 

 snow is transformed into ice, becomes more and more solid, it 

 moves as a mass, and no longer as an accumulation of grains. 

 It is like a mass of snow which rolls gradually down to a lower 

 level vmtil it becomes like a solid mass, which is pushed forward 

 upon a solid basis, and from that time it begins to exert a me- 

 chanical action ; and that mechanical action consists in pushing 

 forward, in rolling under its mass, those loose materials which 

 are broken from the solid foundation. So we have our process 

 beginning, which consists in the grinding of the loose materials 

 which are below the ice. It would seem as if those materials 

 would soon be exhausted, and as if presently the mass of ice 

 would have nothing but a smooth surface over which to glide, 

 and no longer continue this process. But let us have a trans- 

 verse section of the same valley, [sketching it on the blackboard.] 

 We have here a mass of snow occupying the lower portion ; its 

 walls, exposed to the atmospheric agencies, are all the time dis- 

 integrating, and, in consequence of that, fragments of these 

 rocks fall down between the snow and the rock, and, as the 

 mass of ice is moving on gradually, these loose materials pass 

 between the ice and the rock, and are contributing constantly 

 to increase the amount of grinding materials which are provided 

 to enable this gigantic rasp or plough to continue its work. And 

 so we find at the lower part of the glacier an immense amount 

 of loose materials, all ground to powder, when the fragments 

 have been worked upon for a sufficient time, or reduced to 

 smaller fragments, if the process has been continued for a 

 comparatively short time. 



Now, these materials have certain characteristics by which 

 they can be easily distinguished from any loose materials 



