The denomination of the Baltic, applied to the inland sea which forms the subject of this article, is first found in the work entitled Chorographia Scandinavie, by Adam of Bremen, who was canon of that city at the close of the eleventh century. The etymology of the name has given rise to many conjectures. The Swedes derive it from the Scandinavian word baell, a girle, because of its peculiar form; the Prussians, from the Saxonian or Lettonian word balt, white, from its being frozen part of the year, or from Baltus, one of their kings; while by others it is derived from Baltea, the name of an island mentioned by Pytheas, a merchant of Marseilles, who, in the second or third century before the Christian era, is supposed to have sailed as far north as this sea. In the countries which bound it, its ancient name was Variatshkoe More, or the Sea of Variahti; by the modern Russians it is called Baltiskoe More; and by the Swedes, Danes, and Germans, the East Sea.
The Baltic is inclosed by Sweden, Russia, Prussia, Mecklenburg, and Denmark; and it communicates with the North Sea by the Skager-Rack, Categat, Sound, and Great and Little Belts. From Swinemunde in the S., to Tornea in the N., its length is 770 geographical miles; and its width from Karlskrona to Memel is not less than 180 miles. Its whole area, including the Gulf of Bothnia, is about 125,000 geographical square miles. It runs first in an easterly direction as far as Memel, a distance of 300 miles, and then northwards as far as Lat. 59. 21. N., a distance of 350 miles, at which point it separates into two great gulfs. One of these, the Gulf of Finland, runs nearly due E.; the other, the Gulf of Bothnia, almost N. The Gulf of Bothnia is 400 miles in length, with an average breadth of 120 miles, but where narrowest it does not exceed 40 miles. Baltic Sea. The archipelago of Aland lies at its entrance. The Gulf of Finland is 200 miles in length, with a mean breadth of 60 or 70 miles. Numerous rocky islands and reefs, many of them level with the water, render the navigation of this sea extremely dangerous.
The greatest depth of the Baltic rarely exceeds 100 fathoms. On the western side it is not more than 15 fathoms; and, in general, it is only from 8 to 10 fathoms. On the S., it nowhere exceeds 50 fathoms. The Gulf of Finland suddenly shallows from 50 or 60 fathoms to 5, or even less. The average depth of the Gulf of Bothnia is not greater than that of the rest of the sea.
It has long been a generally received opinion that the waters of the Baltic are gradually diminishing. Celsius, a learned Swede, who flourished towards the middle of last century, advances this hypothesis; and, from observations made on the coasts of the Baltic, he estimated the diminution at 45 inches in a hundred years. This hypothesis was supported by Linnæus, who founded on it a theory of the earth. M. Otto, in his physical observations on this sea, has suggested another theory to account for its apparent decrease. He supposes that, instead of really subsiding, it may be only shifting its position, and gaining in one quarter what it loses in another; and this he ascribes to the large and rapid rivers, which carry along with them an immense quantity of earth and sand, by which the beds at their mouths are raised, and their banks extend towards the sea.
The views of Celsius have been confirmed by the observations of Von Buch, who also discovered at several places on the western shores of Scandinavia, and at considerable elevations, deposits of sand and mud containing numerous marine shells of species still existing in the neighbouring ocean. Mr Lyell at first entertained doubts of these phenomena; but on subsequent inspection he was led to concur in the opinion of Von Buch. Mr Lyell found the marks which were cut in the rocks at water-line some years previous to his visit, to be actually several inches above the level of the Baltic. From these observations, that eminent geologist concludes, that in several parts of Sweden a gradual elevation of the land is taking place. (Lyell's Principles of Geology.)
The great quantity of sand and mud carried down by the rivers has considerably raised the bottom of this sea, and affected its navigation, so that the mouths of rivers formerly navigable are now inaccessible.
In the Baltic, the tides are scarcely, if at all, perceptible. There are sensible tides in the Skager-Rack; but these begin to diminish in the Cattgat, and are very trifling in the Sound and Belts. There are, however, irregular variations in the level of the waters of the Baltic which bear some resemblance to tides. These elevations generally occur in autumn, when the weather threatens rain; and they last sometimes a few days, sometimes several weeks. The maximum rise is three feet and a half; and the low shores are occasionally inundated. They also render brackish the freshwater lakes which communicate with the sea. In the Gulf of Bothnia, the subsidence of the waters is usually succeeded by north winds; whereas, near Stockholm, these winds usually follow their rise. M. Kraft, formerly professor of experimental philosophy in the Imperial Academy of Sciences at Petersburg, in his treatise on the inundations of the Neva at the autumnal equinox, observes, that three or four days before or after the full or new moon, a violent N.W. wind drives the waters of the Northern Ocean, during the influx of the tide, into the Baltic, and is accompanied or immediately succeeded by a south wind in that sea and the Gulf of Finland. By Schultens, a learned Swede, who paid particular attention to the physical geography of the Baltic, the irregular elevations of this sea are attributed to the state of the atmosphere. He had observed that when the waters were about to rise the barometer fell, and that when they were about to fall it rose. Hence he inferred that the unequal pressure of the atmosphere on different portions of Baltic Sea, the water deranged the level of the waters. The difference between the greatest and the least rise of the barometer in the northern parts of Europe is two and a half inches, which answers to three and a half feet of water, or the difference of the elevation of the waters at their extremes.
In the Sound there are superior and inferior currents. Superior These were first observed by some Englishmen, who, being in a boat in the middle of the channel, found that they drifted towards the Cattgat; but having let down a loaded bucket to the depth of four or five fathoms, the boat became stationary; and when the bucket was sunk deeper, the boat drifted against the superficial current. The general currents of the Baltic are strong, and evidently occasioned by the vast number of rivers and streams that pour their waters into it, many of which, especially towards the north, rise thrice in the course of the year. At the northern extremity of the Island of Bornholm, a violent agitation of the waters, or kind of whirlpool, called by the Swedes malt-quern, or the grinding-mill, is occasioned by the current rushing over a circular cluster of sunken rocks. The waves of the Baltic are short and broken, in consequence of sudden changes of wind, irregular depths, and strong currents.
The waters of this sea are not nearly so salt as those of the ocean; and when the wind blows strong from the north they become so fresh as to be fit for drinking or cooking meat. The degree of their saltness varies in different parts, and even in the same parts, according to the season or wind. According to Bergman, in his Physical Geography, the waters near the south coast of Norway, at the entrance of the Skager-Rack, contain from $\frac{1}{3}$th to $\frac{1}{4}$th part of their weight of salt; in the Cattgat $\frac{1}{9}$th; in the Baltic $\frac{1}{10}$th; and in the Gulf of Bothnia from $\frac{1}{10}$th to $\frac{1}{12}$th. The S.W. and W. winds augment the saltness, by introducing the waters of the ocean. In the summer it requires 300 tons of the water of the Gulf of Bothnia to produce one ton of salt, but in the winter only 50 tons. This difference is caused by congelation, and by the diminished flow of fresh water.
The analysis of three pounds of water taken up from the British Sea, on the coast of East Friesland, and the same quantity from near Rostock in the Baltic, gave
| Substance | British Sea | Baltic | |--------------------|-------------|--------| | Muriate of soda | 322 | 263 | | Muriate of magnesia| 196$\frac{1}{2}$ | 111 | | Sulphate of lime | 23 | 12 | | Sulphate of soda | 1$\frac{1}{2}$ | 1 | | Residue | 1$\frac{1}{2}$ | 1 |
The following are the results of some experiments made by Dr Thomson on the specific gravity of the water in the Firth of Forth, the Baltic off Tunaberg, the Sound, and off the Skaw Point; and also on the comparative weight of salt obtained from 1000 grains of each of the waters evaporated.
| Water | Specific Weight of gravity | salt | |-------------------|----------------------------|------| | Firth of Forth | 1-02900 | 38-6 | | Baltic off Tunaberg| 1-00476 | 7-4 | | Sound | 1-00701 | 11-2 | | Skaw | 1-02057 | 32-0 |
In the salt obtained from the water off the Skaw, he found
| Substance | Specific Weight of gravity | salt | |--------------------|----------------------------|------| | Muriate of soda | 55-7 | | | Sulphate of magnesia| 25-0 | | | Muriate of magnesia| 19-3 | |
Wilcke ascertained that the specific gravity of the water of the Baltic was much influenced by the wind. When the wind was at
| Direction | Specific Weight of gravity | |------------------|----------------------------| | East | 1-0039 | | West | 1-0067 | | North-west | 1-0098 | | Storm at West | 1-0118 | There is great difference in the temperature in different parts of the Baltic. The general temperature of the Gulf of Bothnia in July is from $48^\circ$ to $56^\circ$, but it is sometimes heated to $70^\circ$; the medium of the thermometer throughout the year at Uleborg is $29^\circ$, and at Stockholm $42^\circ$. Near the land in the Gulf of Bothnia the temperature of the atmosphere in the month of July was observed to be $68^\circ$, while the temperature of the surface of the water was $63^\circ$; and in October the temperatures of both were respectively $39^\circ$ and $46^\circ$. In the Sound, the temperature of the atmosphere in the month of August was $70^\circ$; on the surface of the water $68^\circ$; and at three fathoms $66^\circ$. On the 10th of October 1813, Dr Thomson found the temperature of the Sound to be $54^\circ$. The Skager-Rack and Gulf of Norway are open to navigation all the winter, whereas several portions of the Baltic are covered with ice in a very moderate degree of cold; and generally the bays and channels are encumbered with ice at the latter end of December. The waters towards the heads of the Gulfs of Bothnia and Finland are first frozen; and the ice being conveyed by the currents to the south, the masses of it are united by the increasing cold into vast fields, which become stationary on the west towards Stockholm, and in the east towards the islands of Dagø and Æsel. In the southern parts of the sea the ice begins to break up in April, but the Gulfs of Bothnia and Finland often continue closed till May. The rigour of the climate in the Baltic is supposed to be considerably diminished by the clearing of the forests and the progress of cultivation; at least the frosts during the fourteenth and fifteenth centuries appear in their intensity and long continuance to have exceeded those of the severest seasons in more recent times.
The winds are extremely variable in the Baltic, but they blow most commonly from the E. in the spring, and from the W. in autumn. Calms are seldom experienced except in the middle of summer.
There is historical evidence that the herring fishery was a branch of national industry in the Sound as early as the year 1168, and in 1389, according to Philip de Mezieres, such vast shoals of herrings crowded into the Sound, that 40,000 boats, with from six to ten men each, were employed in the fishery, besides 900 large vessels, in which the herrings were salted. This important branch of industry, however, no longer exists. Salmon ascend the rivers from April to June, according as they are free from ice. On the S. they abound most in the Oder, Vistula, Dîna, and Narrova; on the N., in the Motala, Dalecarlia, Ulea, Kemi, Tornæa, and Keymen. Salmon-trout is taken in some bays of the Baltic. In the middle of the River Kemi is a small island where an annual salmon fair is held.
Whales very rarely enter the Baltic. The common porpoise is the only one of the lesser species of cetaceous animals that lives habitually in this sea; and at Middlefahrt, in Fumén, is a company which enjoys the exclusive privilege of taking it. There are two varieties of the common seal, which are hunted for their oil in March and April by the peasants of the Isle of Gotland, and of the islands in the Gulfs of Bothnia and Finland.
The trade of the Baltic is of great extent and importance. In 1852, 17,563 ships passed up and down the Sound, of which 3902 were British vessels. The internal trade is also very considerable. The exports consist of the various productions of the countries on its coasts, and include corn, timber, pitch and tar, hemp, flax, tallow, hides, linseed, bristles, wool, &c. Its imports are colonial products, manufactured goods, dry stuffs, wines, salt, coal, &c. The most important ports are St Petersburgh, Riga, Königsberg, Danzig, Swinemünde, Lübeck, Copenhagen, Karlskrona, and Stockhalm. By means of numerous large rivers and canals a considerable trade is carried on with the interior. (See Thomson's Travels in Sweden; Tableau de la Mer Baltique, par Catteau; Tableau des États Danois, par Catteau.)