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in that direction ; neither can we assign with precision its extreme eastern limit, since the country beyond the Caspian and the Sea of Aral is little known. Capt. A. Burnes, in his recent expedition through the valley of the Oxus, found that the whole basin of that river had, a few weeks before he passed through it, been convulsed by a tremendous earthquake, which had thrown down buildings and obstructed the courses of rivers. The great steppe of Tartary is unexplored; and we are almost equally ignorant of the physical constitution of China, in which country many violent earthquakes have been felt. The southern boundaries of the region include the most northern parts of Africa, and part of the Desert of Arabia.” We may trace, through the whole area comprehended within these extensive limits, numerous points of volcanic eruptions, hot springs, gaseous emanations, and other signs of igneous agency; while few tracts, of any extent, have been entirely exempt from earthquakes throughout the last 3000 years. Borders of the Caspian.—To begin on the Asiatic side, we find that, on the western shores of the Caspian, in the country round Baku, there is a tract called the Field of Fire, which continually emits inflammable gas, while springs of naphtha and petroleum occur in the same vicinity, as also mud volcanos. In the chain of Elburs, to the south of this sea, is a lofty mountain, which, according to Morier, sometimes emits smoke, and at the base of which are several small craters, where sulphur and saltpetre are procured in sufficient abundance to be used in commerce. Violent subterranean commotions have been experienced along the borders of the Caspian ; and, according to Engelhardt and Parrot, the bottom of that sea has, in modern times, varied in form ; and they say that, near the south-coast, the Isle of Idak, north from Astrabat, formerly high land, has now become very low.f Any indications of a change in the relative levels of the land in this part of Asia, are of more than ordinary interest; because it has been supposed that the level of the Caspian is much lower than that of the Black Sea, although much doubt has recently been thrown on the observations from which this conclusion was deduced.[ Steppes of the Caspian—A low and level tract, called the Steppe, abounding in saline plants, and composed of tertiary strata containing many shells of species now common in the adjoining sea, skirts the north-western shores of the Caspian. This plain often terminates abruptly by a line of inland cliffs, at the base of which runs a kind of beach, consisting of fragments of limestone and sand, cemented together into a conglomerate. Pallas has endeavoured to show that there is an old

" Von Hoff, vol. ii. p. 99.

* Travels in the Crimea and Caucasus, in 1815, vol. i. pp. 257.264—Von Hoff, vol. i. p. 137. : See Book iv. chap. 19.

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line of sandy country, which indicates the ancient bed of a strait, by which the Caspian was once united to the sea of Azof. On similar grounds, it is inferred that the salt lake Aral was formerly connected with the Caspian. Tradition of deluges on the shores of the Bosphorus, &c.—The convulsions which have produced the phenomena of the steppes may be very modern in the earth's history, and yet a small portion of them only may have happened in the last twenty or thirty centuries. Remote traditions have come down to us of inundations, in which the waters of the Euxine were forced through the Thracian Bosphorus, and through the Hellespont, into the AEgean; and in the deluge of Samothrace, it appears that that small island, and the adjoining coast of Asia, were inundated. In the Ogygian also, which happened at a different time, Boeotia and Attica were overflowed. Notwithstanding the mixture of fable, and the love of the marvellous, in those rude ages, and the subsequent inventions of Greek poets and historians, it may be distinctly perceived that the floods alluded to were local and transient, and that they happened in succession near the borders of that chain of inland seas. They may, perhaps, have been nothing more than great waves, which, about fifteen centuries before our era, devastated the borders of the Black Sea, the Sea of Marmora, the Archipelago, and neighbouring coasts, in the same manner as the western shores of Portugal, Spain, and Northern Africa were inundated, during the great earthquake at Lisbon, by a wave which rose in some places, to the height of fisty or sixty feet; or as happened in Peru, in 1746, where 200 violent shocks followed each other in the space of twentyfour hours, and the ocean broke with impetuous sorce upon the land, destroying the town of Callao, and four other seaports, and permanently converted a considerable tract of inhabited country, which had perhaps sunk down below its former level, into a bay. Diodorus Siculus in his account of the Samothracian deluge, informs us that the inhabitants lad time to take refuge in the mountains, and save themselves by flight; he also relates that, long after the event, the fishermen of the island drew up in their nets the capitals of columns, which, he says, were the remains of cities submerged by that terrible catastrophe.” These statements scarcely leave any doubt that the event consisted of a subsidence of the coast, accompanied by a series of earthquakes, and successive inroads of the sea. In the country between the Caspian and the Black Seas, and in the chain of Caucasus, numerous earthquakes have, in modern times, caused fissures and subsidences of the soil, especially at Tiflis.f The Caucasian territories abound in hot-springs and mineral waters. So late as 1814, a

* Book v. chap. 46. See letter of M. Virlet, Bulletin de la Soc. Géol. de France, vol. ii. p. 341. t Von Hoff, vol. ii. p. 210.

new island was raised by volcanic explosions, in the Sea of Azof; and Pallas mentions that, in the same locality, opposite old Temruk, a submarine eruption took place in 1799, accompanied with a dreadful thundering, emission of fire and smoke, and the throwing up of mire and stones. Violent earthquakes were felt at the same time at great distances from Temruk. The country around Erzerum exhibits similar phenomena, as does that around Tauris and the Lake of Urmia, in which latter we have already remarked the rapid formation of travertin. The lake of Urmia, which is about 280 English miles in circumference, resembles the Dead Sea, in having no outlet, and in being more salt than the ocean. Between the Tigris and Euphrates, also, there are numerous springs of naphtha, and frequent earthquakes agitate the country. Syria and Palestine abound in volcanic appearances, and very extensive areas have been shaken, at different periods, with great destruction of cities and loss of lives. Continual mention is made in history of the ravages committed by earthquakes in Sidon, Tyre, Berytus, Laodicea, and Antioch, and in the island of Cyprus. The country around the Dead Sea appears evidently, from the accounts of modern travellers, to be volcanic. A district near Smyrna, in Asia Minor, was termed by the Greeks Catacecaumene, or the burnt, where there is a large arid territory, without trees, and with a cindery soil.” Periodical alternation of Earthquakes in Syria and Southern Italy.— It has been remarked by Von Hoff, that from the commencement of the thirteenth to the latter half of the seventeenth century, there was an almost entire cessation of earthquakes in Syria and Judea ; and, during this interval of quiescence, the Archipelago, together with part of the adjacent coast of Lesser Asia, as also Southern Italy and Sicily, sufsered greatly from earthquakes ; while volcanic eruptions were unusually frequent in the same regions. A more extended comparison, also, of the history of the subterranean convulsions of these tracts seems to confirm the opinion, that a violent crisis of commotion never visits both at the same time. It is impossible for us to declare, as yet, whether this phenomenon is constant in this and other regions, because we can rarely trace back a connected series of events farther than a few centuries; but it is well known that, where numerous vents are clustered together within a small area, as in many archipelagos for instance, two of them are never in violent eruption at once. If the action of one becomes very great for a century or more, the others assume the appearance of spent volcanos. It is, therefore, not improbable, that separate provinces of the same great range of volcanic fires may hold a relation to one deep-seated socus analogous to that which the apertures of a small group bear to some more superficial rent or cavity. Thus, for example, we may conjecture that, at a comparatively small distance from the surface, Ischia and Vesuvius mutually communicate with certain fissures, and that each affords relief alternately to elastic fluids and lava there generated. So we may suppose Southern Italy and Syria to be connected, at a much greater depth, with a lower part of the very same system of fissures; in which case any obstruction occurring in one duct may have the effect of causing almost all the vapour and melted matter to be forced up the other, and if they cannot get vent, they may be the cause of violent earthquakes. Grecian Archipelago.—Proceeding westwards, we reach the Grecian Archipelago, where Santorin, afterwards to be described, is the grand centre of volcanic action. To the north-west of Santorin is another volcano in the island of Milo, of recent aspect, having a very active solfatara in its central crater, and many sources of boiling water and steam. Continuing the same line, we arrive at that part of the Morea, where we learn, from ancient writers, that Helice and Bura were, in the year 373 B.C., submerged beneath the sea by an earthquake; and the walls, according to Ovid, were to be seen beneath the waters. Near the same spot, in our times (1817), Vostizza was laid in ruins by a subterranean convulsion.” At Methone, also (now Modon), in Messenia, about three centuries besore our era, an eruption threw up a great volcanic mountain, which is represented by Strabo as being nearly 4000 feet in height; but the magnitude of the hill requires confirmation. Some suppose that the accounts of the formation of a hill near Troezene, of which the date is unknown, may refer to the same event. It was Von Buch's opinion that the volcanos of Greece were arranged in a line running N. N. W. and S. S. E., as represented in the Map, Pl. III., facing p. 295; and that they afforded the only example in Europe of active volcanos having a linear direction.f But observations made during the late French expedition to the Morea have by no means confirmed this view. On the contrary, M. Virlet announces as the result of his investigations, that there is no one determinate line of direction for the volcanic phenomena in Greece, whether we follow the points of eruptions, or the earthquakes, or any other signs of igneous agency. Macedonia, Thrace, and Epirus, have always been subject to earthquakes, and the Ionian Isles are continually convulsed. Respecting Southern Italy, Sicily, and the Lipari Isles, it is unnecessary to enlarge here, as the existence of volcanos in that region is known to all, and I shall have occasion again to allude to them. I may mention, however, that Dr. Daubeny has traced a band of volcanic action across the Italian Peninsula, from Ischia to Mount Vultur, in Apulia, the commencement of the line being found in the hot springs of Ischia, after which it is prolonged through Vesuvius to the Lago d'Ansanto, where gases similar

* Strabo, Ed. Fal., p. 900.

* Von Hoff, vol. ii. p. 172. 1 See Plate of Volcanic Bands, facing p. 295.

to those of Vesuvius are evolved. Its further extension strikes Mount Vultur, a lofty cone composed of tuff and lava, from one side of which carbonic acid and sulphuretted hydrogen are emitted.” The north-eastern portion of Africa, including Egypt, which lies six or seven degrees south of the volcanic line already traced, has been almost always exempt from earthquakes: but the north-western portion, especially Fez and Morocco, which fall within the line, suffer greatly from time to time. The southern part of Spain also, and Portugal, have generally been exposed to the same scourge simultaneously with Northern Africa. The provinces of Malaga, Murcia, and Granada, and in Portugal, the country round Lisbon, are recorded at several periods to have been devastated by great earthquakes. It will be seen, from Michell's account of the great Lisbon shock in 1755, that the first movement proceeded from the bed of the ocean ten or fifteen leagues from the coast. So late as February 2, 1816, when Lisbon was vehemently shaken, two ships felt a shock in the ocean west from Lisbon ; one of them at the distance of 120, and the other 262 French leagues from the coast,f—a fact which is the more interesting, because a line drawn through the Grecian archipelago, the volcanic region of Southern Italy, Sicily, Southern Spain, and Portugal, will, if prolonged westward through the ocean, strike the volcanic group of the Azores, which has, therefore, in all probability, a submarine connexion with the European line. How far the island of Madeira, which has been subject to violent earthquakes, and the Canary Islands, in which volcanic eruptions have been frequent, may communicate beneath the waters with the same great region, must for the present be mere matter of conjecture. Besides the continuous spaces of subterranean disturbance, of which we have merely sketched the outline, there are other disconnected volcanic groups, of which the geographical extent is as yet very impersectly known. Among these may be mentioned Iceland, which belongs, perhaps, to the same region as the volcano in Jan Mayen's Island, situated 5° to the north-east. With these, also, part of the nearest coast of Greenland, which is sometimes shaken by earthquakes, may be connected. In another hemisphere the island of Bourbon belongs to the theatre of volcanic action, of which Madagascar probably forms a part, if the alleged existence of burning volcanos in that island shall, on further examination, be substantiated. In following round the borders of the Indian Ocean, to the north, we find the volcano of Gabel Tor, within the entrance of the Arabian Gulf. In the province of Cutch earthquakes are frequent, and at Mhurr, twenty-five miles from Luckput, there is an

* Daubeny on Mount Vultur, Ashmolean Memoirs. Oxford, 1835. t Verneur, Journal des Voyages, vol. iv. p. 111. Von Hoff, vol. ii. p. 275.

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