same time. Thus the Pyrenees and Apennines, the mountains of Dalmatia and Croatia, and the Carpathians, which belong to the same system,- -as may be deduced from the descriptions given of them by various geologists, are all disposed parallel to an arc of a great circle, which passes through Natchez and the mouth of the Persian Gulf. Thus, whatever may have been the cause, the mountains in Europe, which have issued from the earth at the same period, form chains at the surface of the globe,-that is to say, longitudinal projections, all parallel to a certain circle of the sphere. If we suppose, as is natural, that this rule may be applicable beyond the limits within which it has been determined, the Alleghanies of North America, since their direction is also parallel to the great circle which joins Natchez and the Persian Gulf,-would seem to belong, in respect to date, to the Pyrenean system. Elie Beaumont has been able to verify the accuracy of this inference by a careful examination of the descriptions of American geologists. It would appear from this statement that we might venture to conclude that the mountains of Greece, the mountains situated to the north of the Euphrates, and the chain of Gates in India, which also come under this condition of parallelism already indicated, must have risen, like the Alleghanies, along with the Pyrenees and Apennines. If we apply this reasoning to the Atlas, which we find to have the same general direction as the Alps of Switzerland, from the Valais to Styria, and with that of the Caucasus, the Balkan Mountains, and the Himmaleh Mountains, we infer that these vast ranges, and also the Atlas, may have risen at the same period. But at what period did this elevation take place? This can be answered in a general way, by remarking, that in Switzerland the principal chain of the Alps appears to have upraised all the secondary, and also the tertiary strata; hence, according to the opinion already stated, these Swiss mountains, and consequently the Atlas and other ranges, already mentioned, may have risen from below at a comparatively recent period, after the deposition of the tertiary rocks. Allowing this hypothesis to be plausible, it could be showr that an opinion of the ancients,-that, namely, which main tains that the whole country between the Syrtis and th

Atlantic, over which the Atlas chain extends, was formerly insulated, and in that state formed the celebrated Atlantis, -is not destitute of geological probability.*

2. Geology of the Desert, or Sahara Region.-The second, or Sahara region, is eminently characterized by its vast desert of sand, the greatest and most frightful on the face of the earth. On the east it is bounded by a rocky limestone wall to the west of the Nile, and a series of oases and deserts extending from Darfur to the Libyan Desert: on the north by a range of oases and the flat and interesting country along the southern foot of the Atlas chain: on the west by the ocean: and, towards the south, it ceases in about 15° Ñ. lat., sloping gradually down to the fertile and well-watered country of Bornou on the east, Houssa in the centre, and the regions to the westward of Timbuctoo. Houssa and Bornou comprehend that region of Africa known by the name Soudan, or Land of the Blacks.

water.

The Sahara may be considered as divided into an eastern and a western half. Its eastern and smaller halt is more varied by rocks, and cliffs, and oases, than the western and larger, which forms a vast sea of moving sand, well meriting the Arabian name, Sahara Bela-ma, or sea without The Western Sahara is bounded on the east in a line which passes through Fezzan, extending towards the south into Soudan, and towards the north to the Atlas. On many parts of the seacoast it extends under the sea, forming enormous sand banks; and along the coast there are extensive ranges of downs or sand hills. The coast is very dangerous, and much dreaded by seamen. Shipwrecks frequently take place, and the unfortunate survivors are carried off by the savages into a state of the most deplorable slavery. Cape Blanco, so well known to mariners, is not a rocky headland, but a flat sandy projecting white tongue of land, destitute of vegetation. The sand hills continue down to Cape Verde,-a promontory distinguished by its two lofty hills of sand, rising to a height of 600 feet, and overlooking the smaller surrounding downs, and forming a warning landmark, seen by sailors at a great distance.

* The particular geology of the Northern Region, which will include descriptions of Morocco, Fez, Algiers Tunis, and Tripoli, will appear in a future volume of this Library, the present volume being confined prin. cipally to the Central and Southern Regions of Africa.

From the entrance of Gonzalo da Cintra, on the coast of Barbary, to Cape Verde, all the elevated points of solid rock are said to be of igneous origin: thus Cape Barbas, Cape Blanco, Cape Manuel, and Cape Verde are composed of basalt and lava. All the islands, too, along this west coast are of igneous origin.

In this vast waste there are a few oases and wadeys, or valleys, in which springs of water are found, and shrubby plants, chiefly acacias, and tufts of grass. It is inhabited only by pastoral tribes, who roam about from one oasis to another, where a little verdure may be found. Some of these tribes add to their scanty means of subsistence the plunder of such feeble caravans as they may venture to attack; and others are employed in collecting salt and natron for the markets of Bornou and Soudan. For hundreds of miles not an oasis is seen, the surface being one continued plain; in some places blown up into high ridges, in others presenting undulations like the waves of the sea. In parts of the Desert, insulated hills, or ridges of hills of naked sandstone, sometimes also of granite, rise through the sandy surface, appearing like so many islands in the ocean.

Account of the Line of Desert from Tripoli to the Lake Tchad. The line of desert, extending from Tripoli by Mourzouk to Kouka, has been described by our former pupil the late excellent and intelligent traveller Dr. Oudney, and by his enterprising fellow-travellers Clapperton and Denham. As the account is novel and interesting, we shall now lay some details illustrative of it before our readers; occasionally, also, referring to the observations of another well-known African traveller, Captain Lyon.*

Subterranean Villages. All around Tripoli the prevailing rocks are of limestone,-partly of secondary, partly, it is said, of tertiary formation. The Arab inhabitants of the Gharian limestone mountains in Tripoli live under ground, -a circumstance worthy of being particularly recorded, on account of its connexion with the ancient history of man,

* To those interested in African adventure, we recommend an interesting little volume just published, entitled, "A Biographical Memoir of the late Dr. Walter Oudney and Captain Hugh Clapperton, both of the royal navy, and Major Alexander Gordon Laing, all of whom died amid their active and enterprising endeavours to explore the interior of Africa. By the Rev. Thomas Nelson, Member of the Wernerian Society, &c 12mo. Edinburgh, 1830, by Waugh and Innes.

SUBTERRANEAN VILLAGES NEAR TRIPOLI. 251

and also his present condition in some countries. Captain Lyon says, "We stopped at a nest, I cannot call it à village, where all the habitations are under ground. The sheik, on hearing we were under the protection of the bashaw, came to welcome us, and gave us the only hut the place afforded, in which we placed our people and camelloads. As for ourselves, we preferred clearing part of the farm-yard, and pitching our tent in it, surrounded by our horses and camels. This place is called Beni-Abbās. As the natives live, as I have observed, under ground, a person unacquainted with the circumstance might cross the mountain without once suspecting that it was inhabited. All the dwelling-places being formed in the same manner, a description of the sheik's may suffice for the rest. The upper soil is sandy earth, of about four feet in depth; under this sand, and in some places limestone, a large hole is dug, to the depth of twenty-five or thirty feet, and its breadth in every direction is about the same, being, as nearly as can be, a perfect square. The rock is then smoothed so as to form perpendicular sides to this space, in which doors are cut through, and arched chambers excavated, so as to receive their light from the doors. The rooms are sometimes three or four of a side; in others, a whole side composes one, the arrangements depending on the number of inhabitants. In the open court is generally a well, water being found at ten or twelve feet below the base of the square. The entrance to the house is at about thirty-six yards from the pit, and opens above ground. It is arched overhead, is generally cut in a winding direction, and is perfectly dark. Some of these passages are sufficiently large to admit a loaded camel. The entrance has a strong wall built over it, something resembling an ice-house. This is covered overhead, and has a very strong heavy door, which is shut at night, or in cases of danger. At about ten yards from the bottom is another door, equally strong; so that it is impossible to enter these houses should the inhabitants determine to resist. Few Arab attacks last long enough to end in a siege. All their sheep and poultry being confined in the house at night, the bashaw's army, when here, had recourse to suffocating the inmates, being unable to starve them out." Again, at page 29, he says,-" At noon, we arrived at a cluster of

nests about six miles from Beni-Abbās: all the habitations of this place are of the same kind as those already described."

Colonel Silvertop, in an interesting memoir on the Lacustrine Basins of Baza and Alhama, in the New Edinburgh Philosophical Journal, vol. ix., gives an account of a subterranean village called Benamaurel, in Granada in Spain, which is on a larger scale than those mentioned by Captain Lyon. It would probably be a difficult antiquarian investigation to trace the origin of these Spanish subterranean dwellings, inhabited by a considerable population of the poorer classes in various parts of the province of Granada. They may be observed in the outskirts of the cities of Granada, Guadiz, and Baza; but are most numerous in the villages of Benamaurel, Castillejos, Caniles, and Cullar, where they have been excavated in the marl strata, so extensively deposited in that basin, and in those of Benabra, and another in the valley of Guadiz. In Benabra, the entire population lives in caves,-the church, the curate's house, and the venta being the only edifices seen above ground. In the neighbourhood of Bagnovea, in the pope's territories, there is a village, of which an Italian traveller has observed, that a few stones for the purpose of closing the entrance of the cavern, a hole for the smoke to go out of, and an aperture to admit the light, suffice to complete each habitation. In the Isle of Ponza, near the Bay of Naples, is another town of the same description, the inhabitants preferring to reside in caves, although the island abounds in good building materials. In France, many villages of inhabited caverns still exist. Swinburne describes a village of the same kind, which occurs in the province of Andalusia in Spain. The natives of New-Holland and other countries still shelter themselves in caves and caverns, and in the hollows of trees. At an early period, the inhabitants of Europe appear also to have lived principally in natural caves and caverns, or in such as they dug in soft rocks.

The subject of caves has recently attracted considerable attention; but more on the part of the geologist than of the antiquarian. It has been ascertained that in caves in the south of France human remains had been found along with bones of quadrupeds, now no longer met with in a living