22 THE NORTH-EAST ATLANTIC. 



water-line is often displaced several hundred yards according to the direction of 

 the winds. 



Like all land-locked basins, the Baltic is much influenced by atmospheric 

 changes, producing the so-called seiches, analogous to those of Lakes Neuchâtel 

 and Geneva. Schulten was the first to explain these phenomena, showing their 

 coincidence with the movements of the barometer. The waters rise in propor- 

 tion to the depression of the air, often attaining an elevation of 3 to 6 feet. 

 This happens most frequently in spring and autumn, but the phenomenon takes 

 place also in winter beneath the frozen surface, which is then upheaved and even 

 burst asunder with a terrific report by the force of the rising waters. Other 

 and not yet explained movements also occur, though at long intervals, in the 

 Baltic. We read that at times the sea roars in fine weather, rises, and floods the 

 shores, as in 1779, when it deluged the town of Leba, in East Pomerania, rising- 

 IB feet above its usual level. These phenomena are called " sea-bears," not 

 perhaps so much on account of the accompanying noises as of their analogy to 

 the " bores " of marine estuaries. Formerly the process was reversed, the sea 

 receding without any apparent cause to a great distance along the flat shores of 

 the Baltic* 



It is certain that during recent geological epochs the Baltic has greatly 

 changed in form, and observations now being made show that it is still changing. 

 It roughly occupies a long valley parallel to the Scandinavian table-land, but its 

 outlet towards the ocean has been shifted. The channels of the Sound and the 

 Belts have been opened through rocks which at one time formed continuous land. 

 At various points along these straits the opposite sides are seen to correspond, 

 showing that they have been forced open by the action of the water. The 

 marine deposits left in the interior of Sweden also prove that the Baltic com- 

 municated directly with the Kattegat through the great Lakes Wenern and 

 Wettern, at present connected by the Goteborg Canal. At considerable depths 

 in these lakes the naturalist Loven has fished up various species of arctic marine 

 Crustacea belonging, some to the Polar Sea, others to the Gulf of Bothnia. t The 

 presence of these animals shows that in the glacial period the Swedish lakes 

 communicated with the Baltic, and were not sweet, but vast salt straits winding 

 from sea to sea. Owing to the upheaval of the Scandinavian peninsula which is 

 still going on, they were transferred to land-locked basins, and their waters, con- 

 tinually fed by rain and river, lost all their saline character. Most of their 

 fauna perished, but some became acclimatized, and it is these that are now dis- 

 covered at the lowest depths of the Swedish lakes. + 



In animal species the Baltic is one of the poorest seas, the mingling of 

 sweet and salt waters and the great variability of the yearly temperature being 

 unfavourable to the development of life, According to Nilsson there are not thirty 

 species of salt-water fishes, and the only cetacea are the seal and dolphin. All 



* Glohis, No. 22, 1872. 



f Mémoires de V Académie des Sciences de Suède, 1861. 



X Ch. Martins, " Du Spitzberg au Sahara." 



