THE SAHARA.
This is a vast sandy desert, which occupies the central parts of northern Africa. It extends from east to west not less than 2650 miles, and from north to south it varies from 700 to 1200 miles; and this immense region perhaps enjoys a smaller share of the gifts of nature than any other known portion of the globe. Even the Libyan desert, which is considered superior to the latter, is strongly impressed with all the characteristics of sterility. Its surface is formed of a hard sandstone rock, as "smooth and level as a bowling green, not exhibiting the least furrow or depression of the surface for hundreds of miles. Nothing is to be seen but the hard pavement under foot, and the cloudless sky overhead. At last the scene changes. The sandstone is succeeded by gravel, frequently interspersed with rounded pebbles. The surface continues to be flat, but is frequently furrowed by ravines and glens, sinking sometimes to thirty feet below the general level, and in these depressions a few bushes are met with. Round these bushes the finer sand, brought by the easterly winds, frequently collects, so as to form small sand-hills." Some portions of these gravelly plains are covered with incrustations of salt, which look like ice; and in others there are whole rows of sand-hills, which look like miniature ranges of mountains. The other portion of the great desert is nearly all sand, the sand being occasionally raised into hills, which are moveable, and rise and fall in the wind like the waves of the sea. Sometimes when a mighty wind arises, the violent gales raise up "the loose sand in such quantities that a layer of nearly equal portions of sand and air, and rising about twenty feet above the surface of the ground, divides the purer atmosphere from the solid earth. This sand, when agitated by whirlwinds, sometimes buries whole caravans, and frequently puts them into the greatest confusion." "One of the largest of these pillars of sand," says Caillie, "crossed our camp, overset all the seats, and whirling us about like straws, threw one of us on the other in the utmost confusion. We knew not where we were, and could not distinguish anything at the distance of a foot. The sand wrapped us in darkness like a fog, and the sky and the earth seemed confounded and blended in one. Whilst this frightful tempest lasted we remained stretched on the ground motionless, dying of thirst, burned by the heat of the sand, and buffeted by the wind. We suffered nothing, however, from the sun, whose disk, almost concealed by the clouds of sand, appeared dim and deprived of its rays." There are but few wild beasts in the desert: lions and panthers are met with occasionally, as are gazelles and antelopes; but the only living creatures that are common in the desert are ostriches, which are seen scudding by with almost as much rapidity as the whirlwinds. No other birds are seen except vultures and ravens. It is only along the boundaries that trees are occasionally found, and they are principally acacias or mimosas of different kinds, which almost all produce abundantly what is called gum arabic. It would be impossible to cross the deserts if it were not for the camels, as no other beast of burthen could possibly endure the heat, the fatigue, and the want of water. One of the peculiarities of the Sahara is that there is occasionally found in it a little spot of fertile soil called an oasis, where trees and grass grow with the greatest luxuriance. These little spots are always where there happens to be a spring, as the desolation of the desert is principally produced by its excessive dryness. Throughout the greater parts of the desert, no water is to be procured, and consequently there is no oasis; but on the eastern side, these spots are more abundant, and, indeed, the whole kingdom of Fezzan, which is nearly surrounded by the desert, may almost be regarded as one vast oasis. It is probable that the beauty of these little fertile places may have been exaggerated, as we can easily conceive the rapture with which shady trees and fresh grass must be hailed by a traveller who has been passing several days over burning sands.
THE DESERTS OF SOUTH AFRICA.
The principal of these is the desert called the Great Karoo; Karoo in the Hottentot language signifying dry or arid. The Cape territory consists of three successive ranges of mountains running parallel to each other, and the space enclosed between the last two of these is the desert in question. It consists of a vast plain, 300 miles in length, and nearly 100 in breadth, the soil of which is of such a hard impenetrable nature as to bear scarcely any trace of vegetation.
It is supposed that there are numerous other tracts of arid clay in the interior of South Africa, as the natives, when describing the interior of the country to the settlers, frequently mentioned the word Karoo; but they have not as yet been explored by human beings.
THE DESERTS OF ASIA.
The principal of these are in Tartary, that is, the highlands of central Asia, where there are extensive arid plains, and occasionally, for the space of a thousand miles, great deserts of loose sand, which, being carried about by the winds, is raised aloft in drifting clouds, as in the great desert of Africa. To the north of the Altai Mountains the country subsides into the low ground of Siberia, which, with occasional ranges of hills, extends in one vast plain to the Arctic Sea. These steppes, as they are generally called, are usually barren, but some of them are covered with deep forests, and others abound in rock salt and salt lakes, very few portions being fitted for agriculture or pasturage. "They are of the most dreary aspect, and as they advance into the northern latitudes, they combine the double evil of a barren soil and a severe climate."
There are many other deserts in Asia, but none of any great consequence except the Deserts of Arabia. Arabia may be described as a vast collection of rocky and precipitous mountains, encircled by a border of low, barren, and sandy plains. From the sea-coast these plains extend from 100 to 200 miles into the interior as far as the hills. On the north the deserts extend from the hills to Syria, over Arabia Petræa or Stony Arabia; and on the south they reach as far as the mountains which overlook the Indian Ocean. "The great characteristic of those vast tracts of desert, which frequently extend on a dead level for several hundred miles, is aridity, and its necessary consequence barrenness. They consist either of bare rocks or of hard or loose sand, and are almost destitute of fresh water. There is no eminence to arrest the clouds as they sweep along the sky, and whole years frequently pass away without rain. The drought is consequently extreme; vegetation withers under the fierce influence of a scorching sun; and the burning sands, reflecting the solar rays, occasion such intense heat as is not felt even in countries that lie directly under the equator. There are no rivers, the mountain torrents being speedily imbibed by the sandy soil; and the scanty supplies afforded by deep wells and springs, scattered at distant intervals, are the sole dependence of the fainting traveller for refreshment, and frequently for life. Without this resource these deserts must have for ever remained impervious to man. The aspect of desolation is sometimes relieved by verdant spots, which appear like islands on the trackless ocean; and some rare and hardy plants, such as the tamarind and the acacia, which strike their roots into the clefts of the rocks, find here a congenial soil, and flourish amid the surrounding waste." In the Arabian plains the thermometer is generally above 100° during the night; and this excessive sultriness renders the whole atmosphere almost insupportable, particularly as refreshing breezes are rarely felt, no change of temperature occurring to set the winds in motion; and dead calms occur, which sometimes continue for sixty days without interruption. Even when the winds resume their activity, this country is seldom visited by any but the simoom or hot blast of the desert, under the withering influence of which all nature seems to languish. It is said, indeed, to have the quality of extracting from whatever it touches every trace of moisture; and it produces, when inhaled by either men or animals, a painful feeling of suffocation. When the camels feel it approaching, they lie down and bury their noses in the sand, to save themselves from its destructive effect; and the travellers, also, who meet it, throw themselves on their faces until it has passed. The approach of the simoom is indicated by an unusual redness in the sky, which, during the prevalence of the wind, seems to be all on fire.
The wells which are found sprinkled throughout the Deserts of Arabia are of great antiquity, and generally from twenty-five to thirty fathoms deep. They are lined with stone, and are believed by the inhabitants to be the work of a primæval race of giants.
DESERTS OF AUSTRALIA.
These are comparatively little known, but as it has been ascertained that the greater part of the interior of Australia is flat and almost destitute of water, it is most probable that it contains vast sandy deserts: and, in fact, every attempt that has been hitherto made to explore the interior of the country confirms the idea of its desolation. Near the central mountains are extensive plains which have been partially cultivated; though they are rendered almost uninhabitable by the frequent seasons of drought to which they are exposed.
PLAINS OF EUROPE.
There are no tracts of land in Europe which deserve the name of desert, though there are some which cover a vast extent of country without any hills. The most extensive of these tracts are the Steppes of Russia, which extend almost from the Baltic Sea to the Black Sea, with scarcely any undulations of surface. The large plain in the north of Germany, which lies at the foot of the Hartz Mountains, is another extensive tract of level ground, but it is highly cultivated.
Nearly one half of France is flat; and one portion of it is occupied with the vast sandy plains called the Landes, which are extensive tracts of sandy deserts producing nothing but broom, heath, and juniper. The most extensive are the Landes of Bordeaux, which are about sixty miles long and forty broad. On these plains some sheep are kept, and the shepherds belonging to them, whether walking or at rest, live, during the day, entirely upon stilts. It is said that this extraordinary custom, which raises their feet three or four feet from the ground, was adopted to enable them to see their sheep, which, from the scantiness of the herbage, frequently wander very far apart; and other reasons no doubt, are, the facilities which the stilts afford for passing over a great extent of country, which is frequently marshy, in an incredibly short space of time. Each peasant always carries a long stick, which serves as a third leg, and enables him, when he stops, to support himself without fatigue. The singular effect produced by these peasants, when seen for the first time, particularly if it chances to be by an imperfect light, is the most extraordinary that can possibly be imagined, as they look like mighty giants rushing through the country with a supernatural speed.
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PEASANTS OF THE LANDES.
In England there are some extensive plains, such as the Downs in Sussex, Salisbury Plain, the Fens of Lincolnshire, the Downs of Devonshire, Dartmoor, and some others. Salisbury Plain is the largest, as it extends twenty-two miles from east to west, and fifteen from north to south.