THE HUMAN SPECIES. 123 



The Oxus was stated already, in antiquity, to have changed 

 her course ; probably because the bed of the stream shifted 

 repeatedly ; for undeniable vestiges of a broad river course, 

 with upright water-worn banks, occur between Khiva and the 

 Caspian, and notably near Old Ourgengj. Both streams now 

 hasten the repletion of the Aral, already of small depth and 

 full of islands ; and these noble rivers, at some future period, 

 may be lost in the sand, or take a course still further north, to 

 Lake Aksakal, or ultimately reach the Tobol or the Ichim, and 

 terminate in the Polar Sea. 



Such are the abstracts of statements, and the inferences 

 which establish the existence of an Asiatic Mediterranean, or, 

 rather, a lagoon sea, in the earlier period of man's presence on 

 the earth ; for until ages after, though in a gradual progress of 

 evanescence, desiccation was not effected till the bed and 

 mouth of the Obi were elevated, when the mass of waters in 

 the lagoons, no longer fed by external supplies, and being 

 of themselves insufficient to maintain the equilibrium against 

 percolation and the power of solar heat upon sand and hard 

 clay, absorbed such an amount of moisture that the level of the 

 dry plains is now far below the surface of the ocean. But so 

 long as there was a sea, Northern Europe was insulated, inac- 

 cessible to migration, excepting on the winter's ice, and in the 

 skin or birchen kayaks of polar nations. Geographically, our 

 best course is now to continue the description of the progres- 

 sive rising of the Arctic soil in Europe, and to return by the 

 Mediterranean to Western Asia; because the chief phenomena 

 affecting changes on the earth's surface are again common to 

 both quarters of the world ; in the north referring mainly to 

 the same effects as already noticed in Asia, but with more 

 undeniable proof; and, in the south-east of the Mediterranean, 



statement is countenanced by the appearance above noticed, and perhaps 

 still more by the prodigious number of Indo-German and Tahtar invaders, 

 which broke in upon Europe about that period. They could not remain 

 in a land without water. 



