116 ICE AND GLACIEKS. 



vegetation, which divides the glacial current of the Gla- 

 cier du Talefre into two branches ; and bolder still they 

 ascend yet higher, to the Col du Geant (11,000 feet above 

 the sea), and down the Italian side to the valley of Aosta. 



The surface of the Mer de Glace shows four of the 

 rocky walls which we have designated as medial moraines. 

 The first, nearest the east side of the glacier, is formed 

 where the two arms of the Glacier du Talefre unite at the 

 lower end of the Jardin ; the second proceeds from the 

 union of the glacier in question with the Glacier de 

 Lechaud ; the third, from the union of the last with the 

 Glacier du Geant ; and the fourth, finally, from the top of 

 the rock ledge which stretches from the Aiguille du 

 Geant towards the cascade (g) of the Glacier du Geant. 



To give you an idea of the slope and the fall of the 

 glacier, I have given in Fig. 15 a longitudinal section of 

 it according to the levels and measurements taken by 

 Forbes, with the view of the right bank of the glacier. 

 The letters stand for the same objects as in Fig. 14 ; p is 

 the Aiguille de Lechaud, q the Aiguille Noire, r the 

 Mont Tacul, f is the Col du Geant, the lowest point in 

 the high wall of rock that surrounds the upper end of 

 the snow-fields which feed the Mer de Glace. The base 

 line corresponds to a length of a little more than nine 

 miles : on the right the heights above the sea are given in 

 feet. The drawing shows very distinctly how small in 

 most places is the fall of the glacier. Only an approxi- 

 mate estimate could be made of the depth, for hitherto 

 nothing certain has been made out in reference to it. But 

 that it is very deep is obvious from the following indivi- 

 dual and accidental observations. 



At the end of a vertical rock wall of the Tacul, the 

 edge of the Glacier du Geant is pushed forth, forming an 

 ice wall 140 feet in height. This would give the depth 

 of one of the upper arms of the glacier at the edge. In 



