CHAP. xv. GREAT ICE-SHEET OF SWITZERLAND. 295 



of so many leagues, has justly excited wonder, for hundreds 

 of them are as large as cottages ; and one in particular, com 

 posed of gneiss, celebrated under the name of Pierre a Bot, 

 rests on the side of a hill about 900 feet above the lake of 

 Neufchatel, and is no less than forty feet in diameter. But 

 there are some far-transported masses of granite and gneiss 

 which are still larger, and which have been found to contain 

 50,000 and 60,000 cubic feet of stone ; and one limestone block 

 at Devens, near Bex, which has travelled thirty miles, contains 

 161,000 cubic feet, its angles being sharp and unworn. 



Von Buch, Escher, and Studer inferred, from an exami 

 nation of the mineral composition of the boulders, that those 

 resting on the Jura, opposite the lakes of Greneva and Neuf- 

 chatel, have come from the region of Mont Blanc and the 

 Valais, as if they had followed the course of the Bhone, to the 

 lake of Greneva, and had then pursued their way uninter 

 ruptedly in a northerly direction. 



M. Charpentier, who conceived the Alps in the period of 

 greatest cold to have been higher by several thousand feet 

 than they are now, had already suggested that the Alpine 

 glaciers once reached continuously to the Jura, conveying 

 thither the large erratics in question.* M. Agassiz, on the 

 other hand, instead of introducing distinct and separate 

 glaciers, imagined that the whole valley of Switzerland might 

 have been filled with ice, and that one great sheet of it ex 

 tended from the Alps to the Jura, the two chains being of the 

 same height as now relatively to each other. To this idea it 

 was objected that the difference of altitude, when distributed 

 over a space of 50 miles, would give an inclination of 

 two degrees only, or far less than that of any known 

 glacier. In spite of this difficulty, the hypothesis has since 

 received the support of Professor James Forbes, in his very 

 able work on the Alps, published in 1843. 



* D'Arduac, Histoire des Progress, &c. torn. ii. p. 249. 



