42 FIFTH LETTER ON GLACIERS. [1844. 



shown to belong to the canal-shaped glacier, with branches ; so 

 the upper glacier is an exact representative, in its lower part, 

 of the oval glacier, for which I have taken that of the Rhone 

 as a type ; whilst many of the tributary glaciers of Grindelwald 

 and the Jungfrau bear ample testimony to the general fact, that 

 the structure of glaciers is developed during their progression, 

 and after their primitive stratification has been annihilated, 

 by their being projected in avalanches over appalling preci- 

 pices. 



To these brief notes, I have only to add one interesting 

 discovery, though of a somewhat local importance, which I 

 made at Chamouni. The ancient lateral moraine of the Glacier 

 des Bois is acknowledged by De Saussure, and all subsequent 

 writers, to be found in the barrier of debris which crosses the 

 valley of Chamouni, at Les Tines ; but very feeble traces have 

 (I believe) been observed of the corresponding lateral moraine 

 of the left bank of the glacier, excepting those between the 

 Chalet of Montanvert, and the descent of La Filia. I have 

 ascertained, however, that a good part of the ascent to the 

 Montanvert, and especially near the chalets of Planaz, passes 

 over a vast accumulation of debris, whose nature corresponds 

 to that of the granites of the central chain, and which lies to 

 an immense thickness against the rocky slopes of the valley, 

 at the foot of the Aiguille de Blaitiere. The resistance offered 

 by this mass of debris to the progress of the torrents, which 

 descend from the glaciers of Grepon and Blaitiere towards 

 the Arve, has diverted their course in a direction parallel to 

 that of the valley of Chamouni, and it was the observation of 

 this singularity which led me to the detection of the moraine 

 first mentioned, which I could hardly believe had escaped me 

 so long. 



