482 



NATURE 



[Si;PTEMBER II, 1890 



estimated at upwards of a million square miles, and the volume 

 of the rivers which are discharged into them at 226 cubic miles. 

 All this and much more is evaporated annually. There are two 

 constant currents passing through the Straits of Gibraltar, super- 

 imposed on each other ; the upper and most copious one flows 

 in from the Atlantic at a rate of nearly three miles an hour, or 

 140,000 cubic meti-es per second, and supplies the difference 

 between the rainfall and evaporation, while the under-current 

 of warmer water, which has undergone concentration by evapo- 

 ration, is continually flowing out at about half the above rate of 

 movement, getting rid of the excess of salinity ; even thus, how- 

 ever, leaving the Mediterranean salter than any other part of the 

 ocean except the Red Sea. 



A similar phenomenon occurs at the eastern end, where the 

 fresher water of the Black Sea flows as a surface current through 

 the Dardanelles, and the salter water of the Mediterranean pours 

 in below it. 



The general temperature of the Mediterranean from a depth 

 of fifty fathoms down to the bottom is almost constantly 56°, 

 whatever may be its surface elevation. This is a great contrast 

 to that of the Atlantic, which at a similar depth is at least 3° 

 colder, and which at 1000 fathoms sinks to 40°. 



This fact was of the greatest utility to Dr. Carpenter in con- 

 nection with his investigations regarding currents through the 

 Straits, enabling him to distinguish with precision between 

 Atlantic and Mediterranean water. 



For all practical purposes the Mediterranean may be accepted 

 as being, what it is popularly supposed to be, a tideless sea, but 

 it is not so in reality. In many places there is a distinct rise 

 and fall, though this is more frequently due to winds and 

 currents than to lunar attraction. At Venice there is a rise of 

 from one to two feet in spring tides, according to the prevalence 

 of winds up or down the Adriatic, but in that sea itself the tides 

 are so weak that they can hardly be recognized, except during 

 the prevalence of the Bora, our old friend Boreas, which gene- 

 rally raises a surcharge along the coast of Italy. In many straits 

 and narrow arms of the sea there is a periodical flux and reflux, 

 but the only place where tidal influence, properly so called, is 

 unmistakably observed is in the Lesser Syrtis, or Gulf of Gabes ; 

 there the tide runs at the rate of two or three knots an hour, and 

 the rise and fall varies from three to eight feet. It is most 

 marked and regular at Djerba, the Homeric island of the 

 Lotophagi ; one must be careful in landing there in a boat, so 

 as not to be left high and dry a mile or two from the shore. 

 Perhaps the companions of Ulysses were caught by the receding 

 tide, and it was not only a banquet of dates, the " honey-sweet 

 fruit of the Lotus," or the potent wine which is made from it, 

 which made them " forgetful of their homeward way." 



The Gulf of Gabes naturally calls to mind the proposals 

 which were made a few years ago for inundating the Sahara, 

 and so restoring to the Atlantic region the insular condition 

 which it is alleged to have had in prehistoric times. I will not 

 allude to the English project for introducing the waters of the 

 Atlantic from the west coast of Africa ; that does not belong to 

 my subject. The French scheme advocated by Commandant 

 Roudaire, and supported by M. de Lesseps, was quite as 

 visionary and impracticable. 



To the south of Algeria and Tunis there exists a great depres- 

 sion stretching westward from the Gulf of Gabes to a distance 

 of about 235 miles, in which are several chotts or salt lakes, 

 sometimes only marshes, and in many places covered with a 

 saline crust strong enough to bear the passage of camels. Com- 

 mandant Roudaire proposed to cut through the isthmuses which 

 separated the various chotts, and so prepare their basins to 

 receive the waters of the Mediterranean. This done, he intended 

 to introduce the sea by a canal, which should have a depth of 

 one metre below low-w^ater level. 



This scheme was based on the assumption that the basin of 

 the chotts had been an inland sea within historic times ; that, 

 little by little, owing to the difference between the quantity of 

 water which entered and the amount of evaporation and absorp- 

 tion, this interior sea had disappeared, leaving the chotts as an 

 evidence of the former condition of things ; that, in fact, this 

 was none other than the celebrated Lake Triton, the position of 

 which has always been a puzzle to geographers. 



This theory, however, is untenable ; the isthmus of Gabes is 

 not a mere sandbank ; there is a band of rock between the sea 

 and the basin of the chotts, through which the former never 

 could have penetrated in modern times. It is much more 



NO. 1089, VOL. 42] 



probable that Lake Triton was the large bight between the 

 island of Djerba and the mainland, on the shores of which are 

 the ruins of the ancient city of Meninx, which, to judge by the 

 abundance of Greek marble found there, must have carried on 

 an important commerce with the Levant. 



The scheme has now been entirely abandoned ; nothing but 

 the mania for cutting through isthmuses all over the world which 

 followed the brilliant success achieved at Suez can explain its 

 having been started at all. Of course, no mere mechanical 

 operation is impossible in these days, but the mind refuses to 

 realize the possibility of vessels circulating in a region which 

 produces nothing, or that so small a sheet of water in the 

 immensity of the Sahara could have any appreciable effect in 

 modifying the climate of its shores. 



The Eastern Basin is much more indented and cut up into 

 sepai-ate seas than the Western one ; it was therefore better 

 adapted for the commencement of commerce and navigation ; 

 its high mountains were landmarks for the unpractised sailor, 

 and its numerous islands and harbours afforded shelter for his 

 frail barque, and so facilitated communication between one point 

 and another. 



The advance of civilization naturally took place along the 

 axis of this sea, Phoenicia, Greece, and Italy being successively 

 the great nurseries of human knowledge and progress. Phoenicia 

 had the glory of opening out the path of ancient commerce, for 

 its position in the Levant gave it a natural command of the 

 Mediterranean, and its people sought the profits of trade from 

 every nation which had a seaboard on the three continents 

 washed by this sea. Phoenicia was already a nation before the 

 Jews entered the Promised Land, and when they did so they 

 carried on inland traffic as middlemen to the Phoenicians. Many 

 of the commercial centres on the shores of the Mediterranean 

 were founded before Greece and Rome acquired importance in 

 history. Homer refers to them as daring traders nearly a 

 thousand years before the Christian era. 



For many centuries the commerce of the world was limited to 

 the Mediterranean, and when it extended in the direction of the 

 East it was the merchants of the Adriatic, of Genoa, and of Pisa 

 who brought the merchandise of India, at an enormous cost, to 

 the Mediterranean by land, and who monopolized the carrying 

 trade by sea. It was thus that the elephant trade of India, the 

 caravan traffic through Babylon and Palmyra, as well as the 

 Arab kafilehs, became united with the Occidental commerce of 

 the Mediterranean. 



As civilization and commerce extended westwards, mariners 

 began to overcome their dread of the vast solitudes of the ocean 

 beyond the Pillars of Hercules, and the discovery of America by 

 Columbus, and the circumnavigation of Africa by the Portu- 

 guese, changed entirely the current of trade as well as increased 

 its magnitude, and so relegated the Mediterranean, which had 

 hitherto been the central sea of human intercourse, to a position 

 of secondary importance. 



Time will not permit me to enter into further details regarding 

 the physical geography of this region, and its history is a subject 

 so vast that a few episodes of it are all that I can possibly attempt. 

 It is intimately connected with that of every other country in 

 the world, and here were successively evolved all the great 

 dramas of the past and some of the most important events of less 

 distant date. 



As I have already said, long before the rise of Greece and 

 Rome its shores and islands were the seat of an advanced civili- 

 zation. Phoenicia had sent out her pacific colonies to the 

 remotest parts, and not insignificant vestiges of their handicraft 

 still exist to excite our wonder and admiration. We have the 

 megalithic temples of Malta sacred to the worship of Baal, the 

 generative god, and Ashtoreth, the conceptive goddess, of the 

 universe. The three thousand nurhagi of Sardinia, round towers 

 of admirable masonry, intended probably for defence in case of 

 sudden attack, and the so-called giant graves, were as great a 

 mystery to classical authors as they are to us at the pi-esent day. 

 Menorca has its talayots, tumuli somewhat analogous to, but of 

 ruder construction than, the nurhagi, more than 200 groups of 

 which exist in various parts of the island ; with these are 

 associated subordinate constructions intended for worship ; altars 

 composed of two immense monoliths, erected in the form of a 

 X ; sacred enclosures and megalithic habitations. One type of 

 talayot is especially remarkable, of better masonry than the 

 others, and exactly resembling inverted boats. One is tempted 

 to believe that the Phoenicians had in view the grass habitations 



