174 M. Desov on f he 



the movement would be facilitated by the numerous fissures 

 occasioned by this tearing. 



At any rate, I must say that this splitting supposes a de- 

 gree of rigidity entirely at variance with the theory of semi- 

 fluidity, and that it could hardly be accounted for, even by 

 tlie theory of expansion. There is, I think, a much more 

 simple way of explaining this phenomena ; it is, that the gla- 

 cier, after having passed the promontory, where it was some- 

 what compressed, comes out into a freer space, where it is 

 able to expand, and the laminae, being seen projecting one 

 beyond the other, like the leaves of a book when bent, be- 

 come more striking. The same thing takes place in the gla- 

 cier of the Rhone, where the laminated structure is more 

 striking below the fall than above ; and similar effects may 

 be observed in all the lateral expansions in the glacier of the 

 Aar. 



I come now to another point, — the appearance of stones 

 on the surface of the glacier. It is a subject upon which 

 most singular opinions have been expressed, and which ap- 

 pears, in fact, at first most enigmatical. When we examine 

 attentively the debris on the surface of one of our large gla- 

 ciers, we see frequently masses and tracks of stones, which 

 commence in the very midst of the glacier, without any ap- 

 parent connection with the mountain slopes from which the 

 lateral and medial moraines proceed. We know, also, that 

 the mountaineers pretend that the ice of the glacier is per- 

 fectly pure, including no kind of foreign body in its interior ; 

 and, in fact, it is true that we find very rarely any foreign 

 body in the walls of the crevasses. Nevertheless, these are 

 occasionally found ; and therefore I agree entirely with Mr 

 Forbes in thinking that all the stones lying on the surface 

 of the glacier " must previously have been imbedded in the 

 virgin ice." The question is, how did they reach the surface ? 

 Mr Forbes, referring to the glacier of the Rhone, which is 

 nearly destitute of stones in the upper part of its course, 

 whilst he says " they begin to appear at the surface at the 

 terminal slope," has proposed a very unexpected explanation 

 to account for their extrusion, which he has illustrated by the 

 diagram, No. 83, PI. II., fig. 7, of this Journal. He supposes 



