In the Rainless Districts vegetation is a nullity; it becomes reduced to a very small number of saline plants and dwarf bushes, nourished by the brackish waters which, the soil conceals. Finally, the desert region may not only be compared to a sea in its aspect and immensity, but it is a true sea, or at least the bed of an ancient sea, which formerly communicated, and, perhaps, was confounded with the Mediterranean, and whose drying up, though still incomplete, took place at a recent geological epoch. We may reasonably conclude that, owing to a series of gradual upheavals, this sea was at first broken up into vast lagoons; that most of these successively disappeared, but not without leaving some certain evidences of the primitive submersion of the continent. "If we might hazard a conjecture," says a recent writer,[41] "it would be that the same convulsions and upheavals which at the close of the tertiary epoch indented the southern coasts of Europe, at the same time drained the ocean which hitherto had rolled over the plains of the Sahara, and submerged the low-lying lands, which probably united the Canaries and Madeira to the mainland." To a similar cause must be attributed the existence of the subterranean waters, springs, ponds, and salt lakes, of which I have already spoken, and of the inland seas--the Caspian, the Sea of Aral, and the Dead Sea; while the Black Sea and its offshoots, the Sea of Azov and the Sea of Marmora, must have had the same origin. I shall discuss this subject further when describing the Great Sahara. In Eastern and Central Asia, the Sandy or Salt Deserts alternate with the Steppes, and with lands susceptible of a certain amount of cultivation. The vast region which geographers designate the Great Gobi, or the Shamo, is intersected by many grassy Steppes and even by fertile fields, where the sedentary Mongols, and especially the Artons, yearly sow and gather hemp, millet, and buckwheat. The sombre picture of "a barren plain of shifting sand blown into high ridges where the summer sun is scorching, no rain falls, and when thick fog occurs it is only the precursor of fierce winds,"[42] is true only of special districts, such as the Han-hai, or "Dry Sea," or the Desert of Sarkha. There, for instance, we meet with no other vegetable than the salsolæ, or salt-worts, which flourish around the small saline pools. Of these pools, when seen from a distance, Mr. Atkinson notices a remarkable characteristic: the salt crystals which accrete upon their banks frequently reflect the orange or crimson hues of flowers, and resemble glowing rubies set in a rich mounting. As we advance in a south-easterly direction, we find the features of the desert region more prominently marked.