Ancient Extent of the Glaciers of Chamonix, 69 



5. Of the ancient Extension of the Glaciers of Mont Blanc from 

 Chamonix to Geneva, 



Before giving an idea of the extent of the antediluvian 

 glaciers, I have thought that it would be of advantage to fol- 

 low one of these glaciers throughout its whole length, from 

 its origin to its terminal moraine. In this journey, we shall 

 everywhere meet with marks which it has left in its passage, 

 and we shall easily establish the identity of these marks with 

 those found in the vicinity of actual glaciers. I choose, as 

 an example, the glaciers of Mont Blanc, which formerly filled 

 all the valley of the Arve, and extended from Chamonix to 

 Geneva. 



Let us transport ourselves to Montanvert, 850 metres 

 above the village of Chamonix. The Mer de Glace is at our 

 feet, it descends from the vast amphitheatres of the Jardin 

 and the Aiguille du Geant. Without being bold mountaineers, 

 we can pass the Fonts, cross the left lateral moraine, and 

 advance to the promontory of the Angle. The whole surface 

 of this promontory is polished and striated above as well as 

 below the surface of the glaciers. Of this we may convince 

 ourselves by looking between the ice and the wall of the 

 granite. If we carry this examination further, we shall see 

 that the rocks are polished and striated to a great height, and 

 that the traces of the glaciers' action only cease at the foot 

 of the high aiguilles which overlook it. Now, the striae which 

 the ice has engraved under our eyes being iaentical with 

 those which are 300 metres above our heads, we are entitled 

 to conclude that the thickness of the glacier, or its puissance 

 (to use the language of the continental geologists), was for- 

 merly much greater than it is now. But if that thickness 

 was greater, so also was its length ; for a necessary relation 

 exists between the three dimensions of a glacier. Thus, 

 then, the terminal moraine, instead of being at the hamlet of 

 Bois, 3 kilometres in advance of Chamonix, was at that time 

 much more remote. We thus see that without quitting the 

 surface of an existing glacier, we can be certain that its ex- 

 tent was formerly more considerable than in our day. But 

 other proofs are not wanting. 



