THE HUMAN iSPECIES. 121 



Aral, though higher, is still known to be below the level of the 

 Euxine. Both are, with the exception of the Caucasian moun- 

 tain system, and the Elburs chain, entirely surrounded by 

 saline plains of hard clay, and low sandy steppes ; on the west, 

 extended to the Sea of Azoph and the Euxine, and between 

 the Kama, Don, Wolga, Jaik, Lake Aksakal, the lower Ichim, 

 and the Amoo, covering a space of 18,000 square leagues. In 

 addition to the inland seas already mentioned, on the south- 

 east is the desert of Karakoum, or of black sand, estimated, 

 alone, at 150 miles in length, by 100 in breadth, forming a 

 plain without a tree, — the floor of an evaporated and perco- 

 lated sea. 



With the exception of the Oulon-tag, the Ildiglis, and the 

 low Monghogar hills, the surface extends north-eastward, with 

 scarcely an undulation. It is studded, in all directions, with 

 smaller lakes, sedgy pools, morasses, and temporary rivers, 

 which now terminate in small water basins, or are lost in the 

 sand ; and the occasional more elevated spaces are always 

 edged by water-worn indications. The vast lake, which for- 

 merly covered a great space on the south of Khiva, in long. 

 59°, lat. 41° 15", has disappeared, all but a few pools, where 

 the whole region is intersected with vestiges of ancient canals 

 of irrigation, now dried up. These show a second stage, or 

 era, when the sea had departed, and rivers still flowed onwards 

 to the Caspian. So, also, the Kirguise steppe, forming the 

 northern portion of the depressed region, is composed of a cold 

 clay, which, notwithstanding, was anciently productive of a 

 remunerating income to the cultivator; but husbandry con- 

 tinuing to be invaded by a black sea-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 

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