10 FIRST LETTER ON GLACIERS. [1842. 



remained there for a week. I was fortunate enough to convey 

 all my instruments to their destination, without, I believe, 

 injury to any one of them. The Mer de Glace, so continually 

 visited by the curious, but so little studied, seemed to me to 

 offer great advantages for the prosecution of the objects which 

 I proposed to myself. At first sight it appeared .to me steeper 

 and more crevassed than I recollected it to be, and I doubted 

 for a moment whether it was adapted for my experiments ; but 

 that doubt vanished upon closer examination ; and in the course 

 of the single week which I have been able to spend there, being 

 favoured by most excellent weather, I have obtained results so 

 far definite and satisfactory, that, imperfect as they necessarily 

 are, and only the commencement of what I expect to accomplish 

 during the remainder of the season, I will state them shortly. 



You will recollect that, in my lectures on glaciers delivered 

 last December and January, and afterwards in an article 

 written by me in the Edinburgh Review,* I insisted on the 

 importance of considering the mechanism of glaciers as a ques- 

 tion of pure physics, and of obtaining precise and quantitative 

 measures as the only basis of accurate induction. I pointed 

 out, also, the several experiments of a critical kind which might 

 be made ; such, for instance, as the determination of the motion 

 of the ice at different points of its length, in order to distinguish 

 between the theories of De Saussure and De Charpentier ; for, 

 if the glacier merely slides, the velocity of all its points ought 

 (in the simplest case) to be the same ; if the glacier swells in 



* [For April 1842, as, for example, the following passages : 



" The mechanism of a glacier is a problem of natural philosophy, and one much 

 more difficult and embarrassing than it has commomy been supposed" [to be], 

 Ed. Rev., p. 52. 



" The solution of this important problem [the theory of glacier motion] would 

 be obtained by the correct measurement, at successive periods, of the spaces between 

 points marked on insulated boulders on the glacier ; or between the heads of pegs 

 of considerable length, stuck into the matter of the ice, and by the determination of 

 their annual progress." Ed. Itev., p. 77. 



The lectures referred to in the text were delivered by the author in the Uni- 

 versity of Edinburgh to a numerous audience, including many men of science. 

 They traced out mainly the same views as are embraced in the article in the Edin- 

 burgh Review, but with larger details of the author's experience of 184] .] 



