139 



rainy Northwest, which resembles his native habitat, he 

 thrives both in body and estate. 20 



Besides the climatic gradations in temperature which 

 are found in different latitudes, there is climatic varia- 

 tion in temperature correlated with altitude. There are 

 zones of latitude and zones of altitude. 21 Miss Sem- 

 ple tells us that the southern slope of the Monte 

 Rosa Alps, from glacier cap at 4,500 meters to the banks 

 of the Po River, yields within certain limits a zonal epit- 

 ome of European life from Lapland to the Mediter- 

 ranean. 22 Climate changes with altitude in much the 

 same way as with latitude. Generally speaking, heat 

 and absolute humidity diminish as height increases, while 

 rainfall becomes greater up to a certain level. "The 

 effect of ascending and descending currents of air is to 

 diminish the range of temperature on mountain slopes 

 and produce rather an oceanic type of climate." 23 Uni- 

 form climate is usually found in a land of monotonous 

 relief, while a region rich in vertical articulations is rich 

 also in local varieties of climate. Plant and animal life 

 conform to the climatic levels at different altitudes. 



"Central Asia has a threefold cultural stratification 

 of its population, each attended by the appropriate den- 

 sity, according to location in steppe, piedmont and moun- 

 tain. The steppes have their scattered pastoral nomads ; 

 the piedmonts, with their irrigation streams, support 

 sedentary agricultural peoples, concentrated at focal 

 points in commercial and industrial towns; the higher 

 reaches of the mountains are occupied by sparse groups 



20 Huntington, H. "Changes of Climate and History," Amer. Hist. Re- 

 view, vol. 18, no. 2, Jan. 1913, p. 231. 



21 See figure 52. 



22 Semple, op. cit., p. 557. 23 Ibid., p. 558. 



