Fig. 5.—THE DEPTH OF THE MEDITERRANEAN.

From a Chart by M. Delesse.

From an examination of the coasts, as well as from the traditions of the people inhabiting them, we learn that the Me­di­ter­ra­nean has varied frequently in its contours and extent. The straits which connect its waters with those of the ocean have frequently changed their position. At a time when peninsulas like Greece, and even islands like Malta, formed part of continental masses—and that they did so in a comparatively recent geological epoch is proved by their fossil fauna—the waters of the Me­di­ter­ra­nean covered large portions of Africa, of Southern Russia, and even of Asia. The researches of Spratt, Fuchs, and others have satisfactorily proved that towards the close of the miocene age a vast {24} fresh-water lake stretched from the banks of the Aral, across Russia, the plains of the Danube and the Archipelago, as far as Syracuse in Sicily. Then came the briny waters of the ocean. There was a time when the Black Sea and the Caspian connected the Archipelago with the Gulf of the Obi. At another epoch the gulfs of the Syrtes penetrated far inland, and a large portion of what is now the Libyan and Saharan desert was then covered with water. The Strait of Gibraltar, which was torn asunder by Hercules according to the traditions of the ancients, is in reality but of recent origin, and has taken the place of a more ancient strait which joined the Me­di­ter­ra­nean to the Red Sea and Indian Ocean: this strait has been restored by human hands, and is known now as the Suez Canal. The coast-lines of the Me­di­ter­ra­nean are undergoing perpetual change, owing to the upheaval or subsidence of the countries surrounding it. The Nile, the Po, the Rhone, and other rivers incessantly enlarge the alluvial plains at their mouths, and still further encroach upon the sea. Actually the Me­di­ter­ra­nean, with its subordinate seas from the Strait of Gibraltar to the Sea of Azof, covers an area about thirty times that of the British Islands. This area is small if we compare it with the immense development of the coasts and the wealth in peninsulas, which impart an aspect of life and independence to at least one-third of the ancient world. The Me­di­ter­ra­nean, though it takes precedence of all the oceans, in consequence of the part it has played in history, nevertheless only covers an area one-seventieth that of the Pacific.[6] It is broken up, moreover, into several separate seas, some of them so small in extent that the navigator hardly ever loses sight of the land. In the {25} east we have the Black Sea, with its two dependencies, the Seas of Azof and of Marmara. The Ægean Sea, or Archipelago, with its numerous islands, extends between the deeply indented coasts of Greece, Asia Minor, and Crete. The Adriatic stretches towards the north-west, between the Balkan peninsula and Italy; and the Me­di­ter­ra­nean proper is divided into two separate basins, which might appropriately be called the Phœnician and Carthaginian Seas, or the Greek and Roman Me­di­ter­ra­neans. Each of these basins is again subdivided, the one by Crete, the other by the two islands of Sardinia and Corsica. These various subdivisions of the Me­di­ter­ra­nean differ in area, and still more in depth. The Sea of Azof almost deserves the name of “Swamp,” which was bestowed upon it by the ancients, for if a ship sinks in it the masts remain visible above the water. The Black Sea has a maximum depth of over 1,000 fathoms, but the narrow strait which joins it to the Sea of Marmara is shallower than many a European river. The cavity filled by the Sea of Marmara is far inferior to that of many an inland lake; and the Dardanelles, like the Bosphorus, are hardly wider than a river. In the Archipelago and the eastern basin of the Me­di­ter­ra­nean proper the depth corresponds with the protuberance of the land. Abyssal depths and “pits” of 260 and even of 540 fathoms are to be found in close proximity to the scarped mountain islands of the Cyclades, whilst on the low coasts of Egypt the water deepens only gradually, until in the centre of the Levantine Sea it attains a depth of 1,750 fathoms. The maximum depth—2,170 fathoms—is attained between Crete and Malta. If the whole of the waters of the Me­di­ter­ra­nean were to be collected into an aqueous sphere, the latter would have a diameter of 90 miles; if it fell down upon the earth, it would not even wholly cover a country like Switzerland.

The Ionian Sea is separated from the Adriatic by a submarine ridge rising in the Strait of Otranto, and bounded on the west by a shoal or submarine isthmus, already referred to by Strabo, which joins Sicily to Tunis. This isthmus forms the true geological boundary between the western and eastern basins of the Me­di­ter­ra­nean, which are connected here by a narrow breach only, the depth of which hardly exceeds 100 fathoms. The western of these basins is the smaller and shallower of the two, but nevertheless it attains a depth of 1,100 fathoms in the Tyrrhenian, and of 1,360 fathoms and even 1,640 in the Balearic Sea, and is separated from the waters of the Atlantic by a submarine ridge lying outside the Strait of Gibraltar, and joining Europe to Africa.[7]

This subdivision of the Me­di­ter­ra­nean into separate basins, divided from each other by shoals or submarine ridges, by islands and promontories, sufficiently explains the contrasts between the phenomena of the open ocean and those observed here. In the Me­di­ter­ra­nean, it is well known, the tides are almost everywhere irregular and uncertain. To the east of the Narrows of Gibraltar, in the sea extending between Andalusia and Morocco, the tides are hardly felt at all, and {26} they are, moreover, interfered with to such an extent by currents that it is exceedingly difficult to determine their amplitude, or the establishment of the various ports. Nevertheless the rise and fall of the tidal wave are sufficiently marked to have attracted the attention of Greek and Italian navigators. On the coasts of Catalonia, France, Liguria, Naples, Asia Minor, Syria, and Egypt the oscillation is hardly perceptible, but on those of Eastern Sicily and of the Adriatic the tide sometimes rises three feet, and, if accompanied by storms, may even attain a height of ten feet in certain localities. The Straits of Messina and of Euripo (Eubœa) have their regular tides, and in the Gulf of Gabes the waters rise and fall with the same regularity as in the open ocean. In the Black Sea, however, no tidal movements whatever have been discovered hitherto. It is nevertheless probable that more careful observations will lead to the discovery of a feeble tide, for it is believed that this phenomenon exists even on Lake Michigan, which has only one-fifth the area of the Black Sea.

[Μ]

Fig. 6.—THE STRAIT OF GIBRALTAR.

According to Robiquet, Randegger, and others. Scale 1 : 750,000.