4 EVOLUTION OF THE ENVIRONMENT OF CENTRAL-ASIAN CIVILIZATIONS. 
vegetation and heated by the sun of spring and summer, prevents local rainfall, and 
the residuum of moisture that escaped condensation on the mountains is carried 
on to the colder regions of the north. It is only during the winter that this resid- 
uum is precipitated on the plains as snow, and even this melts away by March, 
awaking to life a varied desert flora, which in turn vanishes under the burning 
April sun. Thus, excepting the relatively ineffective winter snows, the whole of 






























































































































































































































































































































































































110° E. of Greenwich 
Tracts with no outlet seawards Ss 
500 1 1000 2000 miles 

Fig. 1.—Undrained Parts of Asia. (From Elisée Reclus, The Earth and its Inhabitants.) 
this vast inner-continental region receives waters only from the precipitation over 
the high mountains that separate it from the peripheral zone, and from such moun- 
tains as rise sufficiently high within its own area. 
Central Asia, from the western border of Manchuria to the western end of the 
Black Sea, is a series of great and small landlocked basins. From these no water 
flows to the ocean, excepting that which the Black Sea loses through the canyon 
of the Bosporus, which was not opened to the Mediterranean until the present 

