318 



THE LIFE OF JAMES D. FORBES. 



[CHAP. 



' The last two columns/ he writes to Professor Jame- 

 son, * show the effects of the ablation and subsidence in 

 hundredth parts of the whole depression. As we do not 

 know correctly the slope of the bottom or bed of the 

 glacier, it is impossible to estimate how much of the sub- 

 sidence is owing to the declivity. ... It is probable, 

 however, that the greater part of it may be thus accounted 

 for/ l 



While engaged in these operations a remarkable cir- 

 cumstance occurred, the results of which enabled Forbes 

 to calculate the mean annual, velocity of the steep and 

 rugged icefall which forms the outflow of the glacier 

 basin of the Taldfre. He was working on the Mer de 

 Glace with his instruments, when he was accosted by a 

 guide of Chamounix, named David Couttet, who informed 

 him that, while searching for crystals on the moraines of 

 the Glacier de Taldfre, he had that very day discovered, 

 at the bottom of its icefall, the fragments of a knapsack 

 which he at once recognized as one lost ten years before 

 on the glacier above the icefall. The next day, accord- 

 ingly, Forbes went to the spot, accompanied by Couttet 

 and by his invariable companion Auguste Balmat, who 

 also, curiously enough, was able to assist in identifying 

 the lost knapsack. 



' Now, to explain how Couttet and Balmat were in a 

 position to speak so positively to the identity of the frag- 

 ments/ he writes, ' I must observe that David Couttet 

 was then, and has been ever since, lessee of the Pavilion 

 on the Montanvert, and -that the knapsack in question 

 1 Eleventh Letter on Glaciers. 



