THE BALTIC SEA PART OF THE ATLANTIC The Baltic Sea lies in the north-west of Europe, and is bounded by Russia on the east, Prussia on the south, and Sweden and Denmark on the west. It has an area of about 160,000 square miles, and an extreme length and breadth of 900 and 200 miles respectively. On the south it extends in an easterly direction for 300 miles, and then turns almost due north. It communicates with the North Sea by three narrow channels—the Sound (2 miles wide), between Sweden and Zealand ; the Great Belt (8 miles), between Zealand and Funen ; and the Little Belt (i mile), between Funen and Jutland. The most frequented of these passages is the Sound; but all three open into the southern end of the winding and deep channel which separates Jutland from Sweden and Norway, of which the southern part, between Sweden and Jutland, is known as the Kattegat, and the northern part, between Jutland and Norway, as the Skager-rack.
The Baltic terminates to the north in the Gulf of Bothnia, an arm nearly 400 miles long, and from 40 to 120 miles broad; to the east in the Gulf of Finland, which runs nearly due east for 280 miles, with an average breadth of 60 miles. Further south is the Gulf of Riga, and a bend in the southern shore forms the Gulf of Danzig. The principal islands are—the Aland Islands, at the entrance to the Gulf of Bothnia ; Dago and Oezel, at the month of the Gulf of Riga ; Gothland, (Eland, and Bornholm, off the coast of Sweden ; Rugen, off the Prussian coast ; Zealand, Funen, Laaland, and other islands of the Danish Archipelago. Of the numerous rivers entering it, the principal are—the Tomes, Pitea, Dal, &c., on the west ; the Neva, Dwina, and Niemen, on the east; and the Vistula and Oder, on the south. The drainage area of the Baltic is estimated at 717,000 square miles—i.e. about one-fifth of the entire area of Europe, or nearly two and a-half times the area drained into the vastly greater Mediterranean Sea. The im mense amount of fresh water discharged into the Baltic renders its waters comparatively fresh, the average proportion of saline ingre dients being scarcely one-third that of oceanic water. The degree of salinity is least when the supply of river-water is greatest, the specific gravity of water in the Gulf of Bothnia being then only The comparatively slight loss by evaporation being more than balanced by the supply of fresh river-water, there is conse quently an ouViote of the surface-water through the Baltic Strait.
into the North Sea, but compensated to some extent by an inflow from the latter as an under-current.
As regards depth, the Baltic is throughout shallow in com parison with the open ocean, the deepest part being only 690 feet. The average depth is only 10 fathoms in the north, and 50 in the south. The debris discharged by numerous rivers entering it has so accumulated, that many river-mouths and harbours, formerly accessible, cannot now be approached by any but the smallest vessels. The Gulfs of Finland and Bothnia are also shallow, and obstructed by numerous islands and sandbanks. The navigation of the Baltic is, at the best, difficult and dangerous, and is entirely stopped during the winter, when the greater part of it is frozen over. The Baltic Straits are generally closed from December to April ; and even the port of Christiania, in Norway, is occasionally ioe-bound for four months. It is only in very severe winters that the southern parts of the Baltic proper are continuously frozen over. The shores of the Baltic are generally low—sandy in the south, and rocky round the Gulfs of Finland and Riga. On the south are several fresh water lagoons, or hails, separated from the sea by narrow tongues of land called nehrungs.
Two remarkable physical phenomena in connection with the Baltic deserve notice—viz., the formation of bottom ice, and the upheaval of its northern, and subsidence of Its southern, shores. Thin cakes of ice form on the bottom, and rise edgeways to the surface, sometimes in such numbers that the whole surface is rapidly covered with continuous sheets of ice. The raised beaches of Norway, and the occurrence of deposits of shells at elevations of 200 feet and upwards, both on the Swedish and Finnish shores of the Gulf of Bothnia, prove that the whole country to the north of the Baltic has been upheaved within a com paratively recent period. In the south, on the contrary, no raised beaches or elevated shell-deposits are met with ; on the con trary, there seems to be undoubted proof of a general subsidence of South Sweden. Linnaeus, in 1749, measured the exact distance of a certain stone from the sea. In 1836, the same stone was found to be 100 feet nearer the water than in 1749. The periodical rise and fall of the water known as the tides is inappreciable in this sea, if not altogether absent.