Mediterranean Sea, the great midland sea separating the southern shores of Europe from the north coast of Africa, and bounded E. by part of Asia. It was not known to the ancients by its present name. It is called the Great sea in the Scriptures, " the sea within the columns" by Strabo. By the Romans it was called mare internum or mare nostrum. The Mediterranean forms a deep gulf which communicates with the Atlantic through the narrow strait of Gibraltar; it is separated from the Red sea by the isthmus of Suez, now pierced by a canal, and penetrates deeply inland through the Adriatic, and still more so through the Black sea and sea of Azov. - The N. and S. shores of the Mediterranean present a strong contrast; the former is greatly diversified by bays and peninsulas, sinuosities, and islands, while the latter is comparatively uniform. The main body of the sea is divided into two principal basins, each with numerous subdivisions. The western is the smaller, and extends from Gibraltar to the strait between Sicily and the coast of Tunis, the shallowest part of which is called the Adventure bank. The eastern and greater extends from this to the coast of Syria. The subdivisions of these basins have received different names.
The westernmost, reaching from Gibraltar to the islands of Corsica and Sardinia, is sometimes called the Balearic sea, or sea of Majorca or of Valencia; by some it is divided into the Iberic, Sardic, and Gallic seas, the last including the gulf of Lyons. The body of water between the above named islands and Italy is known as the Tyrrhenian sea, also called the Ligurian, Tuscan, or Italian. The Sicilian sea washes the island of Sicily on the south, and joins the Ionian sea, embraced between south Italy and Greece, and communicating through the strait of Otranto with the Adriatic, On the opposite side the African coast is indented by the gulf of Libya, with the Greater and Lesser Svrtis of the ancients. Between Greece and Asia Minor lies the Aegean sea or Archipelago, the White sea of the Turks, whence the Hellespont or strait of the Dardanelles loads into the sea of Marmora (the Pro-pontis of the ancients), which communicates through the Bosporus or strait of Constantinople with the Black sea or Euxine, the latter in its turn communicating through the strait of Yenikale or Kertch (the Cimmerian Bosporus of the ancients) with the sea of Azov. The eastern part of the Mediterranean hears among sailors the general name of the Levant; it was formerly subdivided into the Pamphylian, Syrian, and Phoenician seas. - Five large islands and a great number of smaller ones are scattered through the Mediterranean. The former are Corsica. Sardinia, Sicily, Candia or Crete, and Cyprus. They are all mountainous, the summits rising to considerable heights.
The principal of the smaller islands are the Baleares with Iviza and Formentera, the Tuscan islands between Corsica and the Italian mainland, the Lipari or .Eolian islands, Malta and its smaller neighbors, the Ionian islands, the Dalmatian islands in the Adriatic, and the islands of the Archipelago (the Cyclades and Sporades of the ancients), the largest of which are Negropont (Eubceai. Rhodes, and Samos. Volcanic phenomena are well developed in southern Italy and Sicily, where Vesuvius and Etna are frequently active, and Stromboli in constant eruption. In the Archipelago the island of Santorin is a partly submerged volcano, occasionally active and forming new islets. (See Graham Island.) Only four rivers of importance empty into the Mediterranean: the Ebro, Rhone, and Po on the N. shore, and the Nile in Egypt. Besides these may be mentioned the Guadalaviar, Tiber, Adige, Maritza, Maean-der, and Orontes. - The Mediterranean is noted for its bright and deep blue color, when undisturbed, though probably it does not differ much from the ocean in that respect. Prof. Tyndall attributes this tint to minute particles in suspension, the existence of which he proved by optical experiment.
Carpenter found by filtration that these particles were inorganic, and much more abundant than in the Atlantic. According to Admiral Smyth, a greenish tinge is prevalent in the Adriatic; it borders on purple in the Levant basin, while the Black sea often has the dark aspect from which it derives its name. - The eastern basin is very deep; S. E. of Candia 1,600 fathoms have been sounded, and in a line from Candia to Malta the greatest depth is about 2,000 fathoms. The alluvium of the Nile forms a submarine promontory in front of the delta. In the Archipelago the islands rise steeply out of deep water, as much as 600 fathoms being found between them. The Adriatic is shallow in its northern part, but in the south lias a depression of 500 fathoms. The bottom of the Sicilian sea forms a plateau of less than r,(io fathoms, with several shoals. The depth of the Tyrrhenian sea is probably great, though not known in much detail. The Balearic sea reaches 2,000 fathoms in its deepest parts, the bottom rising toward the strait of Gibraltar, which measures a little more than 900 fathoms in its deepest part. - Although the Mediterranean is usually said to be tide-less, this is not strictly true; tidal motions are noticed in several localities, though small and irregular, and modified by the force and direction of the wind.
The Atlantic tide wave can be directly followed but a short distance along the coast of Spain; on the coasts of France and Italy a small rise and fall occurs, though not regular enough to be formulated in the absence of accurate observations. In the strait of Messina the tidal current, according to Admiral Smyth, runs alternately six hours north and six hours south, though the vertical rise and fall is only a few inches. In the Adriatic the tide is felt sensibly at Venice, but is exceedingly weak in the southern part. On the coast of Africa, Admiral Smyth has observed tides fairly developed in the Lesser Syrtis. A connected study of the tides of the whole basin by means of good instruments, such as modern self-registering tide gauges, is still a desideratum. The local currents of the Mediterranean are partly tidal, and partly due to the winds. At the strait of Gibraltar, however, a strong and constant current runs in from the Atlantic, which cannot be attributed to either of those causes, which merely modify it. This current occupies the middle of the channel, and has a mean velocity of 3 or 4 m. an hour. On either side of it a tidal current is observed, which runs alternately with and against the main current. The true cause of the latter has given rise to much speculation among physicists.
That it is due to the evaporation in the Mediterranean being in excess of the river supply has been generally admitted; but this would imply a constant increase of salinity, unless this increase were kept in check. An undercurrent carrying out the denser water had to be almost necessarily admitted, hut its actual existence was not proved until the experiments of Prof. Carpenter, in the cruise of the Porcupine, showed it conclusively. This physicist has observed that the water of the Mediterranean contains more salt than that of the Atlantic, that this excess of salinity is greater in bottom water than at the surface, and that in the strait of Gibraltar this denser water flows out into the Atlantic, thus restoring the equilibrium of density between the two seas. Observations in the Hellespont and Bosporus have shown that a surface current flows out of the Black sea, and an undercurrent in. The relation of densities is here reversed, the Black sea having the least; but the evaporation being less in proportion to the river supply, the current is due less to a restoration of level than to the difference of densities. - The prevailing winds are mostly from the north and west.
Some of them are known by specific names, such as the mistral, a cold wind blowing from the Alps along the valley of the Rhone to the sea; its opposite, the sirocco, a scorching hot wind carrying the dry heat of the African deserts over Sicily and all Italy; and the bora (Boreas of the ancients), a north wind usually accompanied by terrible thunderstorms. These winds, with waterspouts, which are very frequent, especially in the western basin, render the navigation of the Mediterranean rather dangerous during certain seasons. One of the peculiarities of the Mediterranean is the frequent occurrence of remarkable electrical phenomena, known as the St. Elmo's fire, being balls of fire playing in mid air around the masts of ships, and called by the ancients Castor and Pollux. - The diminution of the temperature of the water with the depth follows entirely different rules in the Mediterranean from those found in the open ocean. Dr. Carpenter's observations have shown that the surface temperature, variable according to the seasons, and sometimes reaching 78° in summer, falls gradually to 54° or 55° at a depth of 100 fathoms; below this depth no further diminution is observed down to the greatest depths at which observations were made (1,743 fathoms). This represents the constant temperature of the great body of water occupying the Mediterranean basin, the upper 100 fathoms alone being influenced by the sun's rays.
In the ocean the cold influx from the polar regions underlies the warmer strata, and reduces the bottom temperature to about 36° even under the tropics. To this influx a barrier is opposed by the comparatively shallow ridge in the strait of Gibraltar. The uniform temperature of so large a mass of water in a nearly closed basin implies an almost entire absence of circulation and probably of aeration; hence a great scarcity of organized life on the bottom in great depths, in fact an almost entire absence of it when compared with the ocean. (See Atlantic Ocean, and Dkedg-ing, Deep Sea.) The dredging of the Porcupine showed that, except near the coast, the bottom consists of a tenacious mud, composed of fine yellowish sand mixed with a bluish clay, the proportions varying according to localities. It yielded nothing but fragments of shells and a few foraminifera. On the generally rocky bottom nearer shore the dredge brought up richer harvests. - The fauna of the Mediterranean presents a number of northern types whose occurrence has been attributed to a former direct communication between it and the bay of Biscay, which geology shows to have been closed since the eocene period.
A few cetaceans and one species of seal inhabit this sea, but are of no commercial importance; the same remark applies to the loggerhead and leather turtles. The tunny, the sardine, and the anchovy among fishes form important articles of trade. Of the lower animals, mollusks, Crustacea, and even radiates, all that are possibly eatable are used as articles of food by the inhabitants of southern Europe. The red coral is found in deep water in most parts of this sea, but the principal fisheries are carried on along the coasts of Algeria, Tunis, and Sicily. The pink variety comes chiefly from that region, while the deep red coral is more prevalent on the east coast of Spain. The finest variety of sponge (the so-called Turkey sponge) is obtained chiefly in the Archipelago and in the Adriatic. In the latter the Austrian government has recently tried its artificial propagation with success. - The shores of the Mediterranean have been the nursery of civilization, the cradle of which was further east. The nations that early established themselves on its borders, particularly on the indented and diversified northern ones, founded there centres sufficiently isolated to foster national feelings, and at the same time near enough to their neighbors for frequent and easy intercourse.
Thus commercial relations were early established between Egypt, Phoenicia, Greece, and Rome, carrying with them arts and literature, and developing these very early to a standard which still serves us as a model. The Roman empire brought the entire coast of this sea under its sway, rendering it thus an open channel for the spread of Christianity from the land of its origin toward the west, where it was to receive its highest development. Afterward the Mohammedan religion overspread the eastern and southern shores, and ultimately covered them with comparative darkness, into which the light of modern progress is but slowly beginning to penetrate at a few points.