1842.] LAWS OF MOTION OF THE MER DE GLACE. 13 



III. SECOND LETTER on GLACIERS, addressed to 

 PKOFESSOR JAMESON.* 



The Laws of Motion of the Mer de Glace farther stated. 



CHAMOUNI, 10th August 1842. 



My Dear Sir Since I last wrote to you on the 4th July 

 from Courmayeur, I have examined, in detail, the two principal 

 glaciers of the Alice Blanche ; and having re-crossed the Alps 

 from Courmayeur by the Col du Geant, where I had the satis- 

 faction of still finding the remains of Saussure's Cabane of 1788, 

 I have pursued for a fortnight my experiments on the motion 

 of the Mer de Glace. Being composed, as you know, of several 

 tributaries which are in some degree independent, and presenting 

 also a considerable variety of surface, this glacier seems as 

 proper as any for detailed experiments, such as those which I 

 am attempting. Being about to quit this place on a tour to 

 Monte-Rosa and the glaciers east of the Great St. Bernard, I 

 wish to explain to you now in what respect my observations 

 differ from those formerly undertaken on the glaciers, and to 

 mention a few results, which, of course, being as yet only 

 partial, ought not to be considered as altogether decisive of the 

 truth or falsehood of any theory ; still I believe it will be 

 admitted that the facts established in my last (and which farther 

 experience has confirmed), militate strongly against some of the 

 received opinions as to the cause of glacier motion. 



You are aware that, in my lectures on glaciers in December 

 and January last, and in an article in the Edinburgh Review 

 for April, I insisted, and so far as I know it was for the first 

 time, on the importance of considering the glacier theory as a 

 branch of mechanical physics, by which I mean that the cause 



* Edinburgh New Philosophical Journal, October 1852. [The coincidence of 

 a few expressions with those in the First Letter will be pardoned when it is recol- 

 lected that these letters were printed precisely as written from the scene of the 

 observations described, and that any comparison of one letter with another was 

 impossible.] 



