1845.] PECULIARITIES IN THE MOTION OF THE AAK GLACIER. 69 



But a new fact still less reconcileable with the dilatation 

 theory resulted from the first attempt to apply geometrical 

 measurement to the motions of this glacier; viz., 



I. The glacier of the Aar moves fastest in its middle region, 

 and slower in its upper and lower regions (i. e. towards the 

 origin and termination). The slowness in the upper region does 

 not so plainly follow from the facts at present before us, but the 

 retardation towards the termination of the glacier is undoubted. 

 The following are the motions originally ascertained, in f ths of a 

 year, or, more exactly, 289 days. We prefer retaining the 

 original measures in Swiss feet ; the stations are in descending 

 order, and a quarter. of league (4000 feet) apart* (the second 

 in order indicates the rock called Hotel des Neufchatelois.) 



169.2 Swiss feet. 



177.1 



141.3 



150.1 



133.1 

 83.7 % 

 58.3 



This result is very different numerically from that which I 

 obtained on the Mer de Glace of Chamouni, but the difference 

 is of the kind which might have been expected from their great 

 diversity of situation and circumstances. I never expected, or 

 pretended to find in the Mer de Glace the same peculiarities of 

 velocity as in other glaciers ; on the contrary, I endeavoured 

 to showf what were the local peculiarities as to slope and 

 breadth, which probably produced the law of variation of the 

 motion which I observed, slowest in the middle, and quickest 

 towards either end, precisely the reverse of that observed by 

 M. Agassiz ; but I neither depreciate the accuracy of his sur- 

 veyor, nor contend that one cause of motion sways the glacier 

 of the Aar, and another that of the Montanvert. On the con- 

 trary, the difference appears to me entirely conformable to the 



* Bulletin de la Societe de Neufchatel, 8th November 1843. 

 f Travels in the Alps, p. 145, 371. 



