THE MASSIF OF MONT BLANC. IO7 
surface of the land is lowered in the drainage area 
of the Rhone about i foot in 1500 years,* though 
no doubt the rate would be greater in the more 
mountainous parts. 
The valley of Chamouni presents grand evidence 
of glacier action. It contains numerous erratic blocks 
and several moraines. That of Argenti^ire almost 
closes the upper valley. It has a height of over 
100 metres, and was the right lateral moraine of the 
Glacier d’Argenti^re. The right lateral moraine of 
the Glacier de Bois does not stop with the glacier, 
but is prolonged in the form of an immense lam- 
part, which formerly extended right across the valley, 
damming back the river, and forming a lake. It 
has now, however, been cut through by the Aive, 
forming the Passage des Tines. It has a height of 
* Penck, Morphologic der Erdoherfldche, vol. 11. 
