THE BALTIC. 21 



No mountains of floating ice are seen in tlie Baltic, as in the polar seas ; 

 but here and there detached masses rising from 14 to IG feet above the 

 surface present a faint image of the fragments of glaciers met with in the waters 

 to the south of Spitzbergen and Greenland. These masses, like those of the 

 glacial epoch, are occasionally charged with stones and other detritus, thus on a 

 small scale continuing the transport of erratic boulders, at one time of such 

 importance in the geological history of Scandinavia, Finland, and Germany. 

 Scientific records quote a great number of facts bearing witness to this displace- 

 ment of rocks borne southwards by the broken masses of ice. Blocks of granite, 

 weighing many millions of pounds, have been thus transported from the coast of 

 Finland to Hogland Island.* 



The law of decreasing temperature observed in the Atlantic prevails also in 

 the Baltic, at least in summer. But the transition is here much more rapid, the 

 inland sea being but slightly affected by the action of the warm currents which 

 temper the waters of the northern seas. The lower strata vary in temperature, 

 as in the Atlantic, and are usually very near freezing point. Thus the plummet 

 reaching the bottom in a depth of 50 to 100 fathoms in a very short space traverses 

 liquid strata varying at least 18°. 



The Baltic is nowhere as deep as the Skager Rak. Between Copenhagen 

 and Bornholm the line never reaches a depth of 32 fathoms ; east of Bornholm, 

 and in the same latitude, it falls to 66 ; but the average is about 44, with 

 no more than 8 fathoms on the Stolpe and some other submarine banks. 

 Farther north, where the Baltic is widest, the depth increases with its 

 area. The greatest depression discovered by the Pomemnia in 1871 lies between 

 Gotland and Windau, where a depth of 126 fathoms was reached, previous but 

 incorrect soundings having given 200 fathoms. All the harbours, both in the 

 south and north, are shallow, being inaccessible to vessels drawing over 16 

 to 20 feet. Still, as a whole, the Baltic is deeper than the North Sea.f Its 

 bed has, so to say, not yet been levelled, still presenting numerous inequalities, 

 in this respect resembling the beds of the countless fresh- water lakes in Sweden 

 and Finland. 



There are no appreciable tides in the Baltic. South of the Straits navigation 

 takes no account of them, though naturalists are able to verify their presence 

 in the Mecklenburg and Pomeranian ports, determining their rise to within 

 a fraction of an inch. Thus in the harbour of Wismar the difference between 

 ebb and flow is estimated at about 3| inches. The variation diminishes 

 continually eastwards, at last escaping the most careful observations. Such 

 faint oscillations are as nothing compared with the changes produced by the 

 atmospheric currents. The strong and continuous west winds cause the water 

 to fall from 4 to 5 feet t in Kiel Harbour, and on the low shores of the Baltic the 



* Von Baer ; Forchhammer ; Ant. von Etzel, " Die Ostsee." 



t Area of the Baltic 138,230 square miles. 



Mean depth (Meyer) 207 feet. 



Approximate contents 29,544,.506 cuhic yards. 



j MiJbius, "Das Thierleben am Boden der deiitschiu Ost and Nord See." 



