Beinarks on Glaciers. 389 



These phenomena, at once well known and easily observed, 

 afford us the means of ascertaining the former existence of 

 glaciers at a remote period, in places where they do not now 

 occm'. When a glacier advances, it rolls before it all the blocks 

 accumulated at its extremity, and which fonn around it a more 

 or less semicirculai" mound. But many glaciers, on parting 

 from the moraine which borders their extremity, present seve- 

 ral others, concentric to the first and of a like structure ; of 

 these, the most remote is necessarily the most ancient, and the 

 intennediate ones mark so many epochs of the successive re- 

 cedence of the glacier. It is thus that Saussm-e formerly de- 

 tected moraines in the valley of Chamouni, although they were 

 partly covered by vegetation. From the extremity of the gla- 

 cier des Bois or of the Mer de Glace, we can, in fact, enume- 

 rate seven concentric moraines, as far as the village of Tines, 

 which is built on the lixst and largest, at the height of more 

 than 200 feet. Ascending towards the Col de Balme, ten or 

 eleven others are distinguishable, although many causes are 

 continually in operation to obliterate them. These collections 

 of rolled stones undoubtedly indicate the ancient extent of the 

 glaciers. We see, in the pai'ticular case alluded to, that the 

 valley of Chamouni was occupied by an immense glacier, re- 

 ceiving in its course those of Argentiere and of Tour, and 

 moving towards the Col de Balme, in order, probably, to de- 

 bouche in the Valais by the Col de la Tete-Nou'e. 



Polished and rounded surfaces, with furrows and striae still 

 remaining, particularly on hard rocks, notwithstanding the de- 

 structive influence of the atmosphere, serve even now as guides 

 to the site of ancient glaciers, in places where they would never 

 have been supposed to exist. Saussure, whose eye nothing 

 escaped, had long since remarked them on the extensive po- 

 lished rock of St Bernard (see vol. ii. p. 451. 4to ed.), as well 

 ajs in other places, but he failed in divining the causes of 

 these appearances. They are seen to exist beneath the ice, 

 withhi the moraines ; they also appear on the outside on the 

 ground, and on the declivities and sides of the valleys, ac- 

 companied, often to a great height, with old lateral moraines. 

 It is thus that we can follow the stria.' beneath the ice of the Aar 

 almost without interruption as far a« the Hospice de la Grim- 



