THE HUMAN SPECIES. 49 



sand, blown from the north, whole districts are now 

 uninhabitable; and ruins of ancient farms, rendered 

 desolate by a bed of this destroying substance, attest 

 the progress and influence of the northern upheaving. 

 The dust comes up from the Obi ; and the results are 

 comparatively recent, though their commencement must 

 date back to a remote period. They were, no doubt, 

 early a cause of the destruction of the caravan trade, 

 already on the decline during the Roman Empire ; and 

 show that the efforts of Russia to revive it are unavail- 

 ing, because the course of the Oxus being changed, trade 

 no longer reaches the Caspian by boats ; and moreover, 

 water becoming annually more scarce, the nomad hordes 

 of the desert, gradually deprived of cultivation by the 

 inroads of the sea sand, and driven eastward by the 

 want of that necessary element, are necessitated to live 

 by rapine wherp the earth grants no subsistence.* 



Rivers like the Jaxartes, now denominated the Syr- 

 deriah or Syhoun, and the Oxus, since called Jeyhoun 

 and Amou, which, according to the ancients, originally 

 flowed more directly westward to the Caspian, are now 

 turned into the Aral a result which changes in the 

 plane of declivity alone could produce, although the fact 

 has been repeatedly ascribed to the labours of a poor, 

 idle, and scanty population, destitute of mechanical skill, 

 and almost of property in the soil. The Jaxartes now 

 reaches Lake Aral through a sedgy bed, filling the 



* See Report to the Acad. des Sciences, Paris, by M. 

 Hommaire Deliel, on the levels of the Caspian and Aral, 

 and on the decrease of the Oxus and Volga. April, 1843. 



D 



