28 A Period in the History of our Planet, 



heights of the British islands, the Alps, the Vosges, and pro- 

 bably most chains similar to these last in height and situa- 

 tion, presented those groups of glaciers, the traces of which 

 have not yet been sufficiently followed to afford a perfect chart, 

 if I may so express myself, of the glacier groups of the re- 

 treat. The whole plain of Switzerland was still filled with 

 ice, for its space is too circumscribed, the distance betwixt the 

 two ranges which encircle it, the Alps on one side, and the 

 Jura on the other, being too small in comparison with the 

 height of these mountain-chains, to admit the supposition of 

 a simultaneous thawing of these plains with those of other 

 countries lying lower and of greater extent. The elevation of 

 the Alps is indeed so considerable, that the masses of ice which 

 proceeded from them overflowed, even at the outset, the in- 

 dependent glaciers of the Jura, and that the collective glacier 

 groups which covered Switzerland took a direction from south- 

 east to north-west, that is, an opposite one to that of the gla- 

 cial movement proceeding from Sweden and Norway. The 

 most evident proofs of this superior grandeur of the alpine 

 ice-masses are afforded by the blocks formed of granitic and 

 other plutonic rocks, which have been deposited principally 

 on the southern declivity of the Jura, and even likewise in its 

 inner valleys, and which bear obtious testimony to the fact, 

 that the motion proceeding from the Alps was continued to 

 the inner chains of the Jura. The level of the Swiss glacier 

 groups sank only by degrees, and from the distribution of the 

 different rocks, the origin of which, in the alpine chain, can bo 

 determined with the greatest exactness, especially from that of 

 the very strikingly peculiar conglomerate of Valorsine, toler- 

 ably certain data may be collected with respect to the height 

 of the different levels of the ice-masses. Step by step, how- 

 ever, the ice faded away likewise from the plains of our native 

 land before the quickening influence of heat ; the blue waters 

 of its lakes rolled their waves unfettered ; the molasse hills were 

 denuded of their covering, only the highest peaks of the Jura, 

 as the Dent de Vaulion, and several others, still retained some 

 independent glaciers. But the beautiful alpine valleys, whoso 

 wild scenery attracts so many admirers of the sublime, were 

 still filled by the glaciers, which were always becoming more 



