2^6 The National Geographic Magazine 



immobile type, in which fluctuations of 

 surface have long since reached a com- 

 parative equilibrium . Where the coast 

 is mobile, changes in the coast con- 

 stantly occur. There the coast will be 

 irregular, and the approaching and pene- 

 trating sea will carry 



Into every bare inlet and creek and bay 



contact and the seeds of development. 

 The northern coast of the Eurasian re- 

 gion is bounded by an immobile coast- 

 line, and its area for 2,000 miles inland 

 is of a monotonous character, which ren- 

 ders communication or the diversifica- 

 tion of type difficult. The development 

 of any race comes where there is a diver- 

 sity of physiographic conditions. It is 

 therefore significant that the three city 

 regions already noted are joined at only 

 one point along southwestern Asia by a 

 strip of territory under physiographic 

 conditions similar to their own. This 

 is, of course, only another way of saying 



that the Taurus, Caucasus, and other 

 ranges of the region are part of that same 

 new uplift which decides the northern 

 outlines of the Mediterranean and fixes 

 the sources of the great river systems of 

 Asia. In its fundamental character- 

 istics, therefore, this region partakes of 

 those coast conditions which exist in the 

 three regions of which it is a link. It 

 is provided with mountain ranges of a 

 similar structure, running in the same 

 general direction, presenting the same 

 general aspect, and furnishing, there- 

 fore, the soil for transmission of common 

 ideas and a similar social structure. 



RAINFAIvI. AND DEVELOPMENT 



Rainfall determines the limits of hu- 

 man development. The rainfall of the 

 world extends from a precipitation of 

 from three to five inches up to ten feet; 

 but the limits of this rainfall within 

 which any civilization is possible are 

 narrow. They extend practically from 



Map Showing Distribution of Atlantic and Pacific Coast Types 



