4 ASIA 



chains is thus seen to be double, as being expressed in 

 abundant summer pastures on the upper slopes, and in 

 gardens and winter pastures on the lower slopes and the 

 adjacent belt. Correspondingly there originates a double 

 influence on man and animals in quest of food: first, 

 a yearly migration of populations between the lowlands 



FIG. 2. Mean Annual Rainfall of Asia. 



and the highlands, between the drought and the snow : 

 second, larger movements of nations along the fertile 

 piedmont belts, which naturally became the highways 

 of history, as peoples were forced by various causes 

 to migrate, and trekked between the deserts on one hand 

 and the mountain wildernesses on the other. 



