overwhelmed, and that a submerged country, once fertilized by the streams which descend from the southern skirts of Atlas, is now covered by sand possessing a depth not to be ascertained.* But, leaving these general reflections, which partake too much of conjecture to recommend to our belief any inferences founded upon them, we proceed to give an outline of the geological structure of those sections of the country which have been actually examined. We find, then, that the following formations have been distinctly ascertained: the transition; the secondary; the tertiary; the volcanic; the alluvial or diluvian; to which may be added those minor results springing from causes still in operation, as connected with the agency of the sea, rivers, and the action of the atmosphere. 1. The transition-rocks are observed on the shore near Algiers, where the tertiary lime and sandstone are seen reposing on talc-slate, similar to that which is found on the coast of France, in the neighbourhood of Toulon. This slate forms the principal mass of the mountain called Bou Zaria, and of the hill on which the capital is built, extending as far as Cape Matafuz. It presents itself in strata very much inclined to the horizon and dipping towards the south, but never in beds; and in some parts it is seen passing into a well-characterized mica-schist; while in others the feldspar predominates so entirely as to give rise to a distinct species of gneiss. There are also certain strata of limestone subordinate to the slate, having a gray colour and a saccharoid appearance. This rock often becomes schistose, and then it passes by an easy change into slate. Throughout these compound masses are discovered veins of quartz, portions of iron-pyrites, and lead-glance. At Cape Matafuz, where the talc-slate passes into mica-slate, there are still beds of limestone placed at a great inclination, denoting the extent of the power by which they have been elevated from their horizontal posture. On the same line of coast, the talc-schist, by insensible degrees, passes into a brown mica-slate containing thin layers of white feldspar, some of which, by an additional quantity of mica, become gneiss-a result which is also produced * Keatinge's Travels in Africa, vol. i., p. 215. when the mica-slate, in its turn, combines with feldspar. Thus, gneiss appears in a variety of instances as the principal member of the formation, being distinguished by an excess of feldspar, usually white and of a large leaf or lamina. The stratification is very irregular, and presents unequivoca marks of a violent action, occasioned, it is probable, by the insertion of some subordinate rocks. It is not particularly rich in the mineral species which are diffused in it; the chief of which are white and smoke-coloured quartz, pure feldspar, crystals of tourmaline, and some fine specimens of white mica. The gneiss does not afford any traces of organic remains; and it is remarked that, though the mountains composed of it are less elevated than those of slate, the form of both is almost entirely the same. 2. The secondary formation in the Algerine territory seems to reduce itself chiefly to what is called the lias member, comprehending limestone-shales, inarlstones, and some sandstones, which occur along with them. The marls are sometimes very bituminous, and contain beds of lignite or brown coal, and also fossil-shells, and occasionally beds of gypsum, fossil-wood, with silicious impressions of ferns, cycadacea, and fuci. The animal remains are numerous and interesting, comprising bones and skeletons of extinct tribes, such as the genera geosaurus, ichthyosaurus, and plesiosaurus. In particular, the lias contains an immense quantity of fossil-shells, of which the predominating one is the Gryphaa arcuata; and hence the marlstones of this formation have occasionally been named gryphite limestones.* The Little Atlas, which is said to extend six hundred miles in length and about eight in breadth, is described as consisting principally of slaty marl, alternating with strata of calcareous matter. The former, which appears to prevail, is quite the same as that found in the lias-beds of Europe, and is associated with calcareous sandstone, and sometimes with a whitish rock, extremely hard, styled a calcariferous silex. In the Mountains of Beni Sala, these marls are intersected by veins of white quartz; and near the summit they are seen gradually becoming harder, till they pass into a slate resembling that of the transition series, and which no longer effer Jameson, in Murray's Encyclopædia of Geography, p. 223. Dd vesces in nitric acid. The organic remains are not so abundant in the African as in the European lias; the specimens mentioned by M. Rozet not exceeding some fragments of oysters, some pectenes, belemnites, a small ammonite, but not a single vegetable impression. Copper appears in considerable quantities, and might in some places be wrought to advantage; but no attempt towards such an object could be made in the midst of a desert country, and exposed to the continued assault of the most cruel and faithless hordes on the face of the earth. 3. In regular succession, the tertiary rocks rest upon the chalk or uppermost member of the secondary class; and though, generally speaking, they are looser in texture than the foregoing, they are, in some cases, not less compact. They abound in fossil remains of the animal and vegetable kingdoms, of which the genera are commonly the same with those now in existence, though many of the species are different. In this division of the mineral world are included some clays, calcareous sandstones, and trap-rocks, such as porphyry, dolerite, greenstone, and basalt. To these may be added, as it respects Africa, beds of sand more or less impregnated with iron, which alternate with sandstone, or a ferruginous limestone, known to the French as "calcaire grossier," and in England by the familiar appellation of London-clay. In the vicinity of the Little Atlas this aggregation of beds rests upon a blue marl a little paler than that which belongs to the lias formation. On the southern side of the range, especially, there appears an immense group of hills, extending to a great distance in all directions, and some of them rising nearly to the height of 5,000 feet above the level of the sea; all of which are composed of the rocks now described, constituting a formation quite similar to that found in Italy on either declivity of the Apennines. The blue marl is covered by a great depth of calcareous sandstone, as also of London-clay, with corals, alternating with sand, both yellow and red. The sandstone, also, when much impregnated with iron, assumes the same colour. The beds which compose it incline to the north at an angle which never exceeds 20°; they are even sometimes quite horizontal. This tertiary formation contains an immense quantity of large oysters-ostria elongata-entirely identical with those which are found in the corresponding position in Provence and Italy. No fragment, however, has been discovered of the bones of fish or quadrupeds. The limestone, which is frequently compact, presents in its composition a great number of corals, as is the case in Austria and Hungary. The oysters lie in the mass of sandstone, but more particularly in the sand itself, which is interposed between the beds. They are found grouped together, several in one place, and most of them retain their two valves or shells-a proof that they are still in the place in which they were when alive, however distant the period. All the country that the French army have hitherto passed over southward of the Little Atlas, consists of this tertiary formation; and, in judging by analogy from the form of the hills as they appeared to the eye at a distance, it was concluded that the same rocks prevail to a great extent, both towards the east and the west, comprehending all the basins invested by the several chairs of mountains to the border of the Sahara. The sands of that desert, it is conjectured by M. Rozet, are nothing different from the sand which is sometimes found in the higher parts of this formation, and beneath which the sandstone and lime exist in horizontal beds covering the blue marl. Hence, it is not improbable, that a similar succession obtains throughout the whole of the dreary waste which separates Barbary from the regions of the Senegal and Niger. It is a little remarkable, that though the rocks which skirt the northern edge of the great plain of the Metijah are the same, and arranged in the same order with those on the south side of the Little Atlas, the inclination, as well as the fossil remains, are different. These last are much more abundant in the hills near the coast, and the shellfish are often seen distinguished by families; consisting usually of the pectenes, the gryphites-ostria navicularis-large oysters, but very different from those of the southern range, terebratuli, echinites, and several polypi. 4. Of volcanic rocks there is no trace in all the portion of the Minor Atlas visited by the enterprising Frenchman, nor in any part of the great plain already so often mentioned. It was only at Cape Matafuz, in the neighbourhood of the fort, that trachyte was observed as having issued from under the tertiary formation. A very curious fact was also noticed in the same place. All the beds of limestone which repose upon the blue marl are perfectly horizontal; but at the place where the porphyry has forced its way through the strata there is a depression, and the beds are there found inclined to the horizon at an angle of from 15° to 20°. The trachyte of Matafuz is a petro-silicious rock, enclosing small crystals of white feldspar, with minute plates of brown mica, and we need not add that it belongs to the family of the porphyries. Small fragments of porous lava were picked up, but could not be traced to their site. There is hardly any doubt that basaltic formations will be detected at no great distance from the spot, so soon as the zeal of science can be separated with impunity from the vigilance of military life, and the student of nature can venture to go abroad without the protection of a regular escort carrying ball-cartridge. 5. The diluvian formation, as the phrase is used by French authors, seems to denote those changes on the face of the earth produced by a great rush of waters, whether that recorded in Sacred Writ, or any subsequent flood which may have since affected particular localities. The whole soil of the plain of Metijah is said to consist of alluvial matter, usually displayed in horizontal beds of an argillaceous marl, and of rolled pebbles, greatly water-worn, but among which are never found large blocks of stone. Everywhere are seen the deserted beds of spacious rivers, the steep banks of which afford a good opportunity for studying the geognostic constitution of the country. Copious streams must formerly have flowed along these channels, and given to the adjoining districts the geological character they still retain. The nature of the marl, it is observed, is nearly the same throughout, but that of the pebbles often changes, both in quality and magnitude. Near the foot of the mountains, the hollows, once occupied by torrents, display large masses of quartz, black and gray limestone, and numerous portions of slate, which must have been brought down by the weight of water acting on the declivities. The bed of vegetable earth, still in many places several feet thick, is always composed of the alluvial marl, which is compact in its structure, and not easily penetrated by water; and hence the origin of the springs and rivulets that are occasionally observed while crossing the plain. The level of the ground, too, is perceived to rise gradually as the traveller approaches the Atlas. At Mazafran the soil is only sev |