ii] FEATURES OF ENVIRONMENT 43 



average sum-total of the characteristic colours, lights 

 and shades of its usual environment. The main 

 advantage of this harmony is protection. This does 

 not mean only concealment and protection from 

 enemies, from other creatures ; to an equally great 

 extent it means protection from elemental influences, 

 as temperature and sun rays, also from the colours 

 reflected by the environment. The prevailing colours 

 of the desert being shades of brown, reddish and 

 yellow, only a dress of the same tints can possibly be 

 in physical equilibrium with the desert ; and there 

 is no vivid white, black, blue or green, because those 

 colours are physically impossible in the desert. 



High Mountains and Vertical Distribution. 



A universal feature of mountains is the decrease 

 of temperature with increasing height, the result 

 being a so-called arctic climate if the mountain is 

 high enough, with preponderance of snow and subse- 

 quent suspension, or suppression of life. 



Since, as a general proposition, temperature de- 

 creases also from the equator to the poles there is a 

 fixed correlation in the temperature of a mountain 

 station between its latitude and its height. This law 

 of latitudinal equivalent in altitude has been formu- 

 lated by A. von Humboldt, the father of the study 

 of vertical or altitudinal distribution. 



