308 Report of the Besearches of M. Agassiz* 



whole mass is stratified, though in a manner somewhat ob- 

 scure. 



The outline of the strata is very far from being similar. If 

 the glacier moved in an equable manner throughout its whole 

 mass, we might, without doubt, expect to find all the project- 

 ing lines regular ; but if the movement occurs irregularly, and 

 the middle part moves more rapidly than the sides, or shall have 

 deep and hollow beds, and if the more rapid movement in the 

 middle continues throughout the whole extent of the glacier, 

 the curves will thereby approximate more and more, and 

 finally will assume the form of a very pointed arch, known by 

 architects under the name of ogive. Now, this is precisely 

 what takes place ; and it is this which, when it reaches a cer- 

 tain limit, makes it so difficult to recognise the outline of these 

 so greatly prolonged arches or curves. 



Another complication presents itself, when the glacier is 

 composed of several portions or tributaries. Each portion at 

 first has its own S3^stem of beds, and in the more elevated re- 

 gions, where the movement is quite regular, the outline of the 

 various portions has a considerable resemblance to that of 

 imbricated tiles. But this regularity exists only in the most 

 elevated regions. Speedily, from local causes, such as the 

 irregularity of the ground, the shape of the valleys, the rela- 

 tive position and size of the different glaciers themselves, &c., 

 the movement ceases to be equal in the different portions ; 

 some are more stationary, while the others advance more ra^ 

 pidly, and speedily the one which takes the lead so prevails 

 over the others, that it appears completely to supersede them. 

 The lower glacier of the Aar is very instructive on this point, 

 and the mutual combination of the several tributaries, as 

 they are severally encountered, is one of the most curious 

 phenomena of stratification. An examination of the chart 

 which M. Agassiz is now preparing will illustrate this matter 

 more than the most ample and detailed description. 



This, for the present, must suffice, in proof that the gla- 

 cier is really stratified ; also, that the strata correspond to 

 the beds of snow which annually fall in the most elevated 

 regions ; that these strata, at first transversal, slowly and 

 gradually become curved in consequence of the more accele- 



