220 SIXTEENTH LETTER ON GLACIERS. [i860. 



XIX. SIXTEENTH LETTER ON GLACIERS. Addressed 

 to PROFESSOR JAMESON.* 



Observations on the Movement of the Mer de Glace down to 1850. Observations 

 by Balmat, at different seasons, in continuation of those formerly detailed. On 

 the gradual passage of Ice into the Fluid State ; observations of M. Person- 

 Notice of an undescribed Pass of the Alps, from Chamouni to Orsieres by the 

 Glaciers of Tour and Salena. 



My dear Sir Having had the good fortune once more 

 to spend a few (though very few) days amongst the glaciers of 

 Chamouni last summer, I avail myself of your kind permission 

 to carry forward the account of my observations, which has 

 now, for a period of eight years, been regularly communicated 

 to the readers of your Journal. As my stay was limited by 

 imperative engagements to little more than a week, I was pre- 

 vented from undertaking a continuous series of observations on 

 the movement of the ice. I was fortunate, however, in obtain- 

 ing materials for the correction and extension of certain parts 

 of my Map of the Mer de Gflace, which were deficient in my 

 former observations, especially as to the exact form of the basin 

 of the great Glacier du Gtant, which I had only visited once 

 before, on occasion of the passage of the Col of that name in 

 1842. This year I traversed again all the difficult part of that 

 glacier, and took angles with the theodolite from the upper part 

 of the basin, immediately under the Aiguille du Geant. But 

 as these observations can have little interest until reduced into 

 the form of a corrected edition of the Map, I shall say nothing 

 of them here.f 



It will be recollected by some of your readers that a re- 

 markable stone called " La Pierre platte,"J: was one of the 



* Edinburgh New Philosophical Journal for January 1851. 



-j- [These corrections were introduced into the new edition of my Map of the Mer 

 de Glace (including also the Glacier of Bossons), accompanying the small abridg- 

 ment of my " Travels," published in 1855 by Messrs. Black under the title of " Tour 

 of Mont Blanc and of Monte Rosa."] 



| Lying on the surface of the Glacier de LGchaud (in the upper part of the 

 Mer de Gkice), and carried along by the motion of the ice. It is marked C in my 

 Map of the Glaciers. 



