THE HUMAN SPECIES. 57 



submersions in the southern Baltic, already observed, 

 from the year 830, such as those resulting from the 

 great storm, when the island of Rugen was separated 

 from the German shore, and' the successive marine de- 

 pressions of the commercial republics of Winetha, Ar- 

 kona, and Jomsberg, near Wollin ; some enduring to the 

 twelfth century, when their ruin, effected by the hand 

 of man, was followed by submersion beneath the waves. 

 Continuous denudations of the sea shore, or erosions of 

 rivers, furnished the amber of the Baltic from very 

 early ages ; and the check of that trade is now only as 

 it respects discovery of it at sea, but not inland. A 

 prolonged depression on this coast alone accounts for 

 the absence of deltas at the mouths of the Vistula and 

 the Oder, and may be in combination with the changes 

 of surface, which, while the real plane of declivity of 

 the two last mentioned rivers became greater towards 

 the north, did not affect their watershed, and aided 

 in throwing the masses of the Lagoon Sea down the 

 western Russian rivers into the Euxine. 



