According to Tournefort, (Voyage an Lerant, torn. ii. p. 121, 125, Sce.,) the Black Sea appears to have been an immense lake, formed by the waters of innumerable rivers, and unconnected with the Medi terranean, and could only empty itself through the Thracian Bosphorus. The mountains which are interposed between it and the Caspian Sea, prevent any opening towards the cast. The waters of the Sea of Azof fall into the Black Sea, from north to south, and oppose any passage in that direction., Therivers of Asia push the waters of the Blaek Sea from south to north. The Danube impels them from the west. It is therefore at the isles of Cya neme alone, between the lighthouses of Europe and Asia, which are situated at the mouth of the Bos phorus, where the waters of the Black Sea could hollow out the earth, and force a passage into .the Propontis: Buffon (Hist. Nat. torn. ix.) has adduced innu merable facts to prove,,that the Mediterranean Sea, the Black Sea, the Caspian Sea, and the Sea of Aral, have at one time been immense lakes ; that the ,Cas pian Sea was formerly of great extent, and that the Mediterranean was once much smaller than it is at present ; • that the. Aral, the Caspian, and the Black Sea, formed only one lake before the opening of the Bosphorus ; and that the Mediterranean, atter this opening, was augmented in the same _proportion as that lake had diminished.
" Siberia, Asia, the Red Sea, Gm," says Pallas, (Travels, torn. ix. p. 163.) " present evident marks of this deluge, of which all the ancient people of Asia, the Chaldeans, the Persians, the Indians, the Thi• betans, and the Chinese, have preserved the remem brance, and which they have fixed within a few years of the Mosaic deluge. Europe, and the low lands of Asia,' have since 'suffered ' considerable clianges by other inundations, sometimes arising from submarine eruptions, sometimes from the sudden overflow of the great inland seas, as the .Mediterra. 'Ilan and the Euxine, which have left dry extensive plains covered with mud • and sometimes to irrup. tions of the sea, increased by enormous submarine eruptions. • . . . • 7 " The opinion of the indefatigable Tournefort Buffon," the same naturalist elsewhere observes, upon the ancient state of the Black. Sea, and it's 'communication with the Caspian, has been more and more confirmed• by the •observations of travellers. The sea monsters, the fish, and the marine shells, which the Caspian has in common with . the Black Sea, render this communication extremely probable ; and tlte same facts proVe also, that the lake of Aral was once joined to the Caspian. In the 3d and 7th vo• lumesof my Travels, I have traced the ancient ex tent of this sea oiler all the desert of Astracan and that of Jaik ; by that appearance of coasts with which the elevated plains of Russia limit the desert, by the state and the fossil productions of this ancient coast, and by the salted mud mixed with calcined sea shells which cover all the surface of the desert."
The Cyanean Isles, at the mouth of the Bospho rus, have been recently examined by Olivier and Choiseul Guuffier, who discovered that these islands were volcanic. " At the mouth of the canal, on both sides of the Bosphorus," says Olivier,( Voy age, torn. p. 69.) " we were struck with the marks of a volcano of several leagues in extent. Every where we observed the rocks more or less al tered or decomposed ; every where we found incon testible marks of the action of subterranean fires. We observed jaspers of different colours, earnelians, agates, and chalcedonies, among porphyries, more or less changed ; a breccia, with little solidity, and` almost decomposed, formed by fragments of trap, agglutinated by calcareous spar ; a beautiful por phyry at the base of a rock of greenish trap, colour ed by copper ; and through an extent of half a league we saw a hard rock of trap, of a greenish blue, equally coloured with copper." In quoting this able traveller, on the volcanic nature of the banks of the Bosphorus, we ought at the same time to state, that he entertains a different opinion from other naturalists' respecting the formation of that strait: He does not believe that the waters of the Black Sea were once more elevated, and that they opened for themselves a passage by the Bosphorus ; but he supposes, ,that the Propontis, the Euxine, and the Mediterranean, always communicated with .each other. , He is of opinion, that the Caspian was ,of much greater extent ; that,it communicated with .the of Azof, and that their waters had the same level ; and he attributes to the currents of the Don, the Kouban, and the, Wolga, filling up of the canal, and the consequent separation of the two seas. After this separation, he supposes that the Black Sea has not changed its level, because it receives more water than it by evaporation • and,that the Caspian Sea has sunk above 60 feet, because it does not receive a quantity of water sufficient to sup ply what is lost by evaporation ; and that it gradually diminished, till an equilibrium existed the supply and the evaporation.
M. Bergman,* who travelled into the country of . the Calmues in 1802 and 1803, has collected a ,vast number of facts, to prove that the Asiatic part. of the steppes of the Calmues was once covered with water, and that the Caspian and Black Seas were formerly united.