THE FORMER EXTENSION OF GLACIERS. 
145 
which nature employs are the glaciers, those lakes 
or rivers of ice which are formed in the highest 
valleys of the Alps, and other mountains of the first 
order. These great masses are in perpetual motion, 
together with the innumerable fragments of rock 
with which they are loaded. These fragments they 
gradually transport to their utmost boundaries, where 
a formidable wall ascertains the magnitude, and 
attests the force, of the great engine by which it 
was erected.” The immense quantity and size of the 
rocks thus transported have been remarked with 
astonishment by every observer. Perraudin, a Chamois 
hunter of the Val de Bagnes, subsequently but inde- 
pendently made the same suggestion to Charpentier. 
It also occurred to, and was proposed in more detail 
by Venetz, and at length in 1829 worked out by 
Charpentier with masterly ability. Agassiz compared 
the Swiss phenomena with those presented in the 
north of Europe, and showed that in both cases the 
country was covered by a sea of ice, from which the 
highest summits alone emerged. 
Charpentier , * and subsequently Guyot,** traced 
the course of many erratic blocks, and pointed out 
that as we proceed from the place of origin they 
* Essai sur les Glaciers. 
** Bull. Soc. Sci. Nat. Neuchdtel , vol. I. 
Scenery of Switzerland. I. I O 
