154 Prof. Forbes's Tenth Letter on Glaciers. 



deny be ultimately found correct. I trust that the results 

 I have now stated will not deter others interested in disco- 

 vering the truth, from prosecuting the subject. It is one 

 well worthy of prosecution ; and it is to be hoped, ere aban- 

 doned as useless, will be put to the severest scrutiny. Not- 

 withstanding the little encouragement I have received, I 

 shall not be deterred, should time and opportunity permit, 

 from renewing my trials, at the proper season, and, if pos- 

 sible, on a more extended scale. 



Tenth Letter on Glaciers. Addressed to Professor Jameson. 

 M, Agassiz's Adoption of the Plastic Theory — Peply to M.. 

 Martins. By Professor J. D. FORBES. Communicated 

 by the Author. 



Edinburgh, 24f^ Novemher 1845. 



My dear Sir, — I trust I may be allowed to call the atten- 

 tion of such of your readers as have had the patience to follow 

 me in the details of the explanation of the theory of glaciers, 

 which I have attempted to bring forward through the medium 

 of your Journal, to a statement which appears by authority* in 

 the last number of the Bibliotheque Universelle^ amongst the^ 

 res gestw of the meeting of Swiss naturalists at Geneva, in 

 August last. The passage alluded to is extracted from an 

 article under the title, Sur les Theories relatives aux Gla- 

 ciers, Bibl. Univ. Aout 1845 {Publie 4 Octobre), p. 347, 

 and may be thus translated : — " M. Agassiz considers 

 ** a glacier as formed of a combination of angular fragments 

 '^ of ice, between which water circulates, in which living ani- 

 " malculae may be seen to swim. When we pour coloured 

 " liquids on the surface of the glacier, they are seen to re- 

 " appear at great depths in the bottom of crevasses, but they 

 " cannot penetrate the interior of the fragments of ice. The 

 " quantity of water which gorges the glacier, seems to be the 

 " cause of its motion, in consequence of the hydrostatic pres- 

 " sure which it exerts on the mass. For this motion becomes 



* I say under authority, because the BibliotUque is edited by M. de 

 b, Rive, the President of the meeting ; and the article in question is 

 signed with the initials of M. Macaire, one of its prominent members. 



