138 G. F. WRIGHT LOESS IN NORTHERN CHINA AND CENTRAL ASIA 



liar manner indicated and filling the central depression of Mongolia with 

 an interior sea. 



Additional confirmatory Evidence 



This theory has the advantage of accounting at the same time for the 

 peculiar distribution of arctic species of seal from the elevated basin of 

 lake Baikal (1,600 feet above the sea) to the isolated Aral and Caspian 

 seas in western Turkestan. It also helps to account for the innumerable 

 evidences that, up to comparatively recent times, there was an immensely 

 greater rainfall over central and western Asia than there is at the present 

 time. For example, it is above all question that up to a comparatively 

 recent time, say 10,000 or 15,000 years ago, the depression of the Jordan 

 valley was filled with water 750 feet above the present level of the Dead 

 sea. The comparative freshness of lake Balkash and of the Aral and 

 Caspian seas likewise indicate a recent rainfall in that region far in excess 

 of the present. In the absence of glacial conditions in the proximity of 

 these seas, this would seem to be best accounted for by the"additional 

 supply of moisture to the atmosphere which would have been furnished 

 from the evaporating surface of extensive inland seas in the center of 

 Mongolia and in other depressed areas in Asia. 



The discussion should not be closed, however, without remarking that 

 ample credit must still be given to the wind as an agency which is still 

 at work distributing the loess and producing many minor modifications 

 which are plainly visible in northeastern China, where many of the ex- 

 tensive deposits are clearly drifted material brought in by the wind in 

 recent times. This may be freely granted without admitting that wind 

 is competent to account for all the phenomena presented. 



