THE DESERT CLIMATE 



21 



may be as cold as — 16° F. (—26-5° C.) in winter. 

 The highest readings which have so far been taken 

 of the surface of the soil were taken on bare sand ; 

 e.g. readings of 183° F. (84° C.) on the Loango 

 Coast, close to the Equator, and Augieras' record of 

 172° F. (78° C.) on a sand dune in the Sahara. The\ 

 surface soil reaches such a high temperature by day 



F XII I II III IV V VI VII VIII IX X XI XII 



El Arish, Sinai. Aden, Arabia. 



Bahrein, Persian Gulf. 



Fig. 6. — Monthly Mean Maximum and Mean Minimum Shade Tem- 

 peratures OF Three Places situated on the Sea Coast of the 

 Great Paljearctic Desert. 



that it does not cool completely during the ensuing 

 night : as a result the minimum temperature 

 reached by the surface of unshaded soil at night may 

 be several degrees above the minimum temperature 

 of the air (C. B. WilHams). It is only the superficial 

 layer of the soil which is liable to these great fluctua- 

 tions of temperature. 



