H. H, Hoirorth — Course of the Rivers of Siberia. 7 



any postulate demanding a land-bridge between Siberia and America 

 in the Mammoth age. 



If the conclusion be sound, we ought to be able to apply an easy 

 test to it, and to find abundant traces of the fact (if not, in the river- 

 beds themselves, where the evidence might easily be obliterated), in 

 the Central Asiatic area, for assuredly such a reversal of the flow of 

 these enormous water-ways must have ci'eated an immense Mediter- 

 ranean Sea in Central Asia. 



Evidences of this sea are not only forthcoming, but they are so 

 palpable and plain that it has become an axiom of physical geography 

 that such a sea existed at no distant date. The proofs of it are 

 various and converging. In the first place, the scattered lakes which 

 dot this part of Asia from the Caspian to Lake Balkhash, whose 

 common fauna can only be explained on the hypothesis that they 

 are the fragments of a once continuous sheet of water, " Relikten 

 seen " as the Germans call them, and secondly the great stretches of 

 arid sand containing semi-fossil shells of species still living in the 

 lakes referred to, and marked by saline deposits, sands known to the 

 natives as the Karakum or black sands, Kizilkum or red sands, etc. 1 



Here then we get a double argument in favour of the contention 

 I am arguing for. The a priori argument deducible from the effects 

 of the rise of the Arctic sea-bed and the a posteriori argument 

 deducible from the actual state of things in Central Asia, the latter 

 being an argument universally conceded and hitherto needing only 

 a rational explanation. While every one allows that a great sea 

 once occupied the Aralo-Caspian depression, it has hitherto been 

 a desideratum to know how this sea could have been supplied with 

 its water, and how it resisted the desiccating effects of the Siberian 

 climate, which are now so obvious. If, as we contend, the great 

 rivers Obi and Yenissei at this date poured their waters into the 

 Asiatic Mediterranean, the whole problem is explained. 



I would add as a curious corollary, that the great plain of European 

 Eussia, which is in many ways a mere prolongation of Asia, and 

 which was in the Mammoth age still more closely united with it in 

 its physical characteristics, still retains its ancient slope, and its great 

 rivers, the Volga, the Don, the Dnieper, and the Dniester still flow 

 southwards. In the Mammoth age their waters were probably 

 further recruited by that which goes to form the Petchora and the 

 Neva. Apart from this last divergence, it seems rational to conclude 

 that Eastern Europe at this moment presents a very close type of 

 what Western Siberia once presented, and that the whole continent 

 from the Caspian to the valley of the Yenissei then had a southern 

 slope and was bounded on the south by a continuous sheet of water, 

 of which the Black Sea and Lake Balkhash are the terminal relics. 



I have limited my induction in regard to Asia to Western Siberia, 

 but I have small doubt that what was true of the Obi and the 

 Yenissei was true of the Lena also ; but here the change that has 

 since occurred in the contour of the country is greater and more 

 complicated, and I will defer its discussion to another occasion. 



1 See S. P. Woodward, Manual of the Mollusca, p. 291, on the range of Cardium 

 rusticum, ibid. Proc. Zool. Soc. July 8, 1856, part II. 



