Where the earth is blessed with copious showers, vegetation will abound; grass, and herb, flower, bush, and tree;
“Fields of grain
Will bend their tops
To the numberless beating drops.”
To meet with the true Desert we must, therefore, direct our steps in a north-westerly course, and penetrate into The Sahara.
M. Charles Martins, in his elaborate monograph on this remarkable region, divides it into three distinct sub-regions: the Desert of the Table-lands, the Desert of Erosion, and the Sandy Desert.[53]
In Algeria, and in Barbary generally, the Mediterranean littoral does not come into immediate contact with the Sahara; but is separated from it by the Atlas chain. But the Atlas does not rise abruptly from the plain: on either side it ascends by a succession of rocky steps or terraces, which form the sub-region of the elevated Table-lands. Vast denuded surfaces, sprinkled with chotts, or salt lakes, deprived of all arborescent vegetation, traversed in summer by immense herds which feed on the plants even to their very roots, bare mountains starting abruptly from these horizontal surfaces; such is the general aspect of the landscape. The richly-varied culture of the Mediterranean littoral has disappeared, and barley is the only cereal which the husbandman relies upon for his harvest. At many points, however, the “purple vine” and “golden olive” succeed admirably, and are destined one day to clothe the nakedness of these plateaux which the free-pasturing herds and the careless Arab have stripped of their blooming verdure.
Descending these rocky terraces of gray old Atlas, we enter the desert region in its first phase: the Desert of the Table-lands, or Saharan Steppe.
Here, horizontal strata of mud and gypsum, or sulphate of lime, are deposited upon the shores, as it were, of the great Sandy Sea. The gypsum reposing on the mud is composed of plates in such close juxtaposition as to resemble an artificial pavement. “It covers the surface of vast plateaux which have not been encroached upon by the waters; whether those waters were marine currents at the epoch when the Sahara was a vast sea, or diluvian torrents which descended from the mountains after their elevation, little matters; the gypsum, produced by the violent evaporation of the Saharan sea, has withstood their operation, and composes the plateaux of which we are speaking. Their surface is so smooth, that vehicles might roll for leagues upon this natural pavement, which echoes like a vault under the horses’ hoofs. A plateau of this kind, the small Desert of Mourad, extends from Biskra to the banks of the great salt lake called Chott Mebrir by the Arabs. The gypseous surface is not everywhere exposed: most frequently it is covered by a layer of small rounded pebbles, nearly all quartzose, exhibiting the greatest variety of tints, from the purest white to the most vivid red; they are mixed with black calcareous stones split on the surface. Whence came these pebbles, which have evidently been ‘rolled’ by the waters? We know not. They are the mysterious witnesses of those grand diluvian torrents which have left the traces of their passage over the surface of the whole earth, though the geologist cannot always discover the mountains or rocks that furnished the materials of this diluvium.”[54]
From the Desert of the Table-lands we must needs make another descent. The town of Batna is situated at the extremity of the lowest of the Atlantean terraces, whose elevation is still some 3300 feet above the level of the sea. To the north-west rise the lofty spires of the colossal chain, with their diadems of cedars sharply defined in black upon the azure of the sky. Loftiest of all soars the Jebel-Tougour, or “Peak of Cedars,” reminding the spectator of the Pyrenean crests. Towards the south-east stretch the rounded shoulders of the mountains of the Aurès, clad with dense dark forest of oak and pine. In a fold of the mountains lurk the ancient Lambessa and the mouldering ruins of a Roman camp. Four miles to the south of Batna is a large depressed hill, whose base mingles with the table-land, above which it rises only three hundred and thirty feet. This ridge marks the watershed; all the streams on the north flowing towards the Mediterranean, and, on the south, gradually disappearing in the arid bed of the ancient Saharan sea. On the frontier line, like a Cyclopean landmark, is planted the Peak of Cedars, while from its loins a torrent issues, and through a deep ravine whirls and leaps and flows towards the desert. Springs, abundant and warm, bubble up through the chalky marls, and take the same direction. Beyond the French military post, called Les Tamarins, the road descends the ravine-cloven mountain-slopes, and passes over the torrent which bifurcates at the foot of the majestic Metlili. On the left is seen a steep wall of rock, the Jebel-Gaouss, cleft midway by a chasm, or breach, which the Arabs expressively designate “The Mouth of the Desert,” and which, gradually enlarging, opens upon the first oasis of the Sahara, El Kantara (“the bridge,” from a Roman arch which spans the torrent), the most northerly limit of the palm-tree. “A magnificent, semi-alpine, semi-tropical scene. Below, a tumultuous foaming stream, its banks on either side clad with palms bending their feathery foliage towards the river, and sheltering fig, apricot, peach, almond, and pomegranate trees.”[55] Above, a range of snowy heights, wreathed in ever ascending and descending clouds.