320 PHYSIOGRAPHY 



land will maintain 2,630 sheep per square mile. 1 These figures do 

 not take account of differences of soil. 



Climate and life. The distribution of life is controlled very 

 largely by climate. The dry deserts of low latitudes, the deserts 

 in the lee of lofty mountains, and the snow deserts of polar regions 

 are essentially climatic. Where rainfall is adequate and where 

 temperature favors, life abounds wherever there is a proper soil; 

 and even the accumulation of a proper soil is influenced by climate. 

 The best soil is worthless where water is wanting, or where the tem- 

 perature is too low for plant life. 



Of Australia it has been said: "Land without rain is worth 

 nothing; and land in an Australian climate, with less than 10 inches 

 a year, is worth next to nothing. Rain-water, without land, if the 

 water can be stored in a reservoir and sent along a canal, is worth 

 a great deal." 2 



It has been pointed out on earlier pages that great progress 

 has been made in the last few years in learning how to cultivate 

 land which has scanty rainfall in such a way that it becomes pro- 

 ductive, even where it cannot be irrigated. These results have 

 nowhere been more successful than in eastern Colorado and western 

 Nebraska. 



From the human point of view, winds are an important element 

 of climate. Calms are enervating and winds stimulating. Winds 

 are of great importance to health where population is dense, for 

 they blow away the dust and other impurities which tend to gather 

 about cities. 



Changes of Climate 



Within historic time. The records of climate, covering as much 

 as a century for some parts of our country, afford little basis for 

 the popular notion, especially among elderly people, that the climate 

 is changing. One reason for this rather common idea is that there 

 seems to be a tendency to exaggerate the striking features of ex- 

 ceptional seasons. The winters of heavy snow, or of intense cold, 

 are the winters which are best remembered. Another reason for the 

 notion that climate is changing is that people change their place 



1 Wills, cited by Hann. 



2 Wills, cited by Hann. 



