Erratic Blocks of Northern Europe. 145 



than the pebbles, it is because, from their weight, they were 

 less exposed to being moved and rolled. It is very natural in 

 Switzerland, where the action of the waters has been less 

 manifest and less prolonged, that the striated pebbles should 

 be more numerous. Thus you do not find there, or only oc- 

 casionally, distinct beds in the properly glacial deposits. 

 Those which are met with, ordinarily occur in the neighbour- 

 hood of torrents.* 



After this epoch of immersion, even the proximate dura- 

 tion of which it is impossible at present to ascertain, the 

 country of Scandinavia was again elevated. The shores bor- 

 dering the high central regions, the plains of Sweden, and 

 those of Finland, were successively raised from the bosom of 

 the waters, bringing back with them to the surface the same 

 mud, the same diluvial gravel, which had been deposited by 

 the glaciers, and which had undergone no other change in 

 the interval than that of being irregularly stratified and 

 mingled with shells. The depressions of the land alone re- 

 mained covered with water, and formed the lakes of Sweden 

 and Finland, as well as the Gulf of Bothnia. The last, iso- 

 lated from the ocean by the uprising of the intermediate 

 land, has lost, by degrees, its saltness ; and this explains the 

 character of its fauna, which is rather the fauna of brackish 

 water than that of the sea. The interior lakes, also, were 

 transformed completely into fresh water, and here and there 

 may parhaps be found some indications of their ancient con- 

 dition. It appears that certain fishes, in particular, have re- 

 sisted these changes in the water; and, according to re- 

 searches of Scandinavian zoologists, especially of Mr Esmark, 

 the trout of Swedish lakes {Salmo trutta^ L.) is only a species 

 of salmon, like the Salmo salar, L. But as the salmon of the 

 coast does not ascend into the lakes, we are naturally led to 

 the conclusion, that this fish has resisted the modifications 

 that have occurred where it dwells. The emersion of land 

 does not take place alike in all parts ; the beautiful observa- 

 tions of Messrs Keilhau and Bravais upon the ancient marks 

 of the level of the Scandinavian sea, teach us that there it was 



* Voy. Rod. Blanchet, Terrain erratique alluvien du Oassin du Leman. 

 VOL. XLTII. NO. LXXXV. — .TULY 1847. K 



