Professor Forbes on the Leading Phenomena of Glaciers. 245 



rated from the bed in which it was run, and divided so as ta 

 shew its various sections. ■ 



It was objected by M. Agassiz* to this theory of the veins, 

 that were it true, so soon as two glaciers united, they would 

 each lose their individual structure, and have single loops duo 

 to the union of their streams, whereas his observations led 

 him to conclude, that the loops of two united glaciers remain 

 distinct. Now, in the first place, I reply, that, though the 

 distinct structure of the double stream is maintained for a 

 time, it is always finally worn out if the glacier be long enough, 

 and the structure then forms single loops, cuttiiig at an angle 

 the medial moraine of the two glaciers ; and, secondly, I 



* Proceedings of the Ashmolean Society ; Mhenoeum Journal, February 1843. 

 In this communication, M. Agassiz confirms my observation of the " dirt-bands ;" 

 adopts the name of " annual rings" (Edin. New Phil. Journal, October 1842), and 

 endeavours to prove the conformity of their intervals to the actual motion of 

 the glacier of the Aar, as I had already done on the Mer de Glace. M. Agassiz 

 still insists, that glaciers are stratified, and he distinguishes these strata, as he calls 

 the annual rings, from the proper veined structure of the ice. Having main- 

 tained, in all his earlier writings, that a glacier is horizontally stratified through- 

 out its whole extent (Etudes, page 40), he now adopts my figure at page 237 of 

 this article, for the lower end of his glacier, and connects it with the neve, by 

 a convenient series of interposed strata, first rising, and then falling, as represented 

 in the annexed cut, which is accurately copied from the original in Leonhard and 



Bronn's Journal, 1843, Heft 1. I can only simply, but distinctly, deny the re- 

 semblance to nature of this scheme, and reiterate the observation already several 

 times made in this work, that the structure of a glacier is, and must be formed in 

 the glacier itself, not in the n6v6, from which it is often separated by an ice-fall, 

 which has ground the integrant parts of the neve to powder, as in the Glacier of La 

 Brenva, the Glacier of Miagc, the Glacier of Talefre, and of Allalein, with many 

 others. Not to mention the section of the Glacier of Macugnaga, where the two 

 structures are seen at once, and perpendicular to each other. 



Yet more extraordinary is the assmnption made by M. Agassiz, in order to 

 account for this supposed prolongation of the beds of the neve into the inferior 

 glacier. In order to explain the alternate rise and fall of the strata, he affirms, 

 that, near the origin of the glacier, the ice in contact with the bed moves fastec 

 than at the suiface, but everywhtre else slower ! 



