THE DESERTS OF AFRICA AND ASIA. 373 



After all I have said, it is superfluous to add that the upheaval of 

 those deserts did not take place at once, but successively, as we have 

 seen in the Sahara-Lybian desert, where the cretaceous and tertiary rocks 

 appeared, one after the other, leaving still large tracts occupied by 

 sea- or fresh-water basins, which were filled up only during the quater- 

 nary epoch, or even in a more recent one. Therefore, it is highly pro- 

 bable, that like the Sahara-Lybian desert, the Asiatic deserts were also 

 crossed, long after the upheaval of their chief portions, by gulfs, or con- 

 tained numerous fresh-water basins — a supposition which, in reference to 

 the Gobi, is supported by the interesting considerations of E. Regel, on 

 the character of the flora of Central Asia.' The learned director of the 

 Botanical Garden of St. Petersburg, says : 'The salt steppes and sand 

 deserts of the lower regions of Central Asia suggest the conclusion 

 that, even at the beginning of the present epoch, consequently during the 

 diluvial period. Central Asia was covered by a large fresh-water lake, 

 throngh which the mountains rose as so many islands, until the time 

 when the waters cut their way through the mountains, and were con- 

 veyed to the sea by the river Obi and perhaps the Amur, having left 

 behind them large dry salt and sand steppes, which contain now an uni- 

 form flora, composed of halophytes and palnstrian species, a flora which 

 has probably opposed serious impediments to the migration of plants. 

 As a striking exemplification of this fact we may quote the entire 

 absence in Central Asia of any rhododendron and of any lily, whereas 

 both these are copiously represented on the Caucasus, the Altai, in the 

 Baikalian and Dahurian regions, on the northern declivities of the 

 Tibetan Alps, and particularly in the Himalayan system. On the con- 

 trary. Central Asia appears a real vegetable centre for the genera 

 Tidi'im, Allium, Eremurus, Elymus, &c., and particularly for the family of 

 Saholacece.^ 



The still unknown part of the Gobi desert belonging to the most 

 important regions of Central Asia, is so large, that all geographers and 

 natural philosophers must hail with joy any undertaking capable of 

 unveiling this terra incognita, particularly the mysterious western portion 

 of it, containing the extensive lake Lob (Lob-Nor), which receives so 

 many considerable rivers, like the Ak-su, Yarkand, Kashgar, and Kothan 

 rivers. The intrepid traveller, who recently explored for the first time 

 the Kuku-Nor lake, is certainly entitled, more than anybody else, to add 

 to his important discoveries this new revelation of Central Asia. 



The name of Colonel Prejevalsky is suflBciently known to all 

 geographers ; but what is perhaps not generally known and what en- 

 hances greatly the merit of this distinguished man, is the fact, that one 

 of the most remarkable explorations of modern times has been carried 

 out, with means the smallness of which would appear quite fabulous, had 

 he not himself mentioned them. Now, Colonel Prejevalsky informs us,^ 

 that the whole amount of money he i-eceived from the Russian Govern- 

 ment in order to meet all the expenses of three years of exploration in un- 

 known and barbarous countries, was only 9,500 roubles, or about 1,100L 

 With this scanty support he crossed (from jSTovember 17, 1870, to Sep- 

 tember 19, 1873) nearly 18,000 miles, of which he mapped almost 9,000 

 miles. 



But how could he, under such conditions, perform such a task, 



' Petermann's MUthcilungen, 1882, vol. xxviii. p. 65. 

 ' Loc. cit. p. 80. 



