ANIMAL LIFE IN DESERTS 



CHAPTER I 

 THE DESERT CLIMATE 



i. General, ii. Water, iii. Heat. iv. Relative Humidity. 

 V. Wind. vi. Evaporation, vii. Light, viii. Summary. 



i. General 

 A prominent authority has stated that the desert 

 occupies one-fifth of the surface of the globe, an 

 area equal to that of Africa. It is probable that 

 the word desert was used in rather a wide sense, 

 and it is certain that no one has yet arrived at a 

 definition of the word which would be acceptable 

 either to the biologists or to the meteorologists. 

 One is accustomed to think of the desert as an 

 area of the earth rendered unfit for normal life by 

 its climate, but, as I hope to show later, there is 

 no climatic factor, or combination of climatic fac- 

 tors, which invariably produces desert ; in fact, a 

 few deserts exist by reason of their geological 

 constitution, though their climate is not particu- 

 larly unfavourable to plant and animal life. As the 

 causes which result in desert are diverse, it follows 

 that the term is not capable of strict definition : 

 the definition which I now put forward is admittedly 



1 B 



