20 ANIMAL LIFE IN DESERTS 



11 a.m. Shade temperature 104° F. (40-0° C). Sun tempera- 

 ture 122° F. (50° C.) 

 3 p.m. Shade temperature 109° F. (43-0° C). Sun tempera- 

 ture 129° F. (54° C.) 



It wiU be noticed that enormous fluctuations in 

 the temperature of the day, and of the year, are 

 generally recorded from such places as Kasalinsk, 

 Petroalexandrovsk, and Tashkent, in which the 

 effect of desert conditions is reinforced by a position 

 in the centre of a great land mass. On the other 

 hand, certain places which are close to the sea are 

 not liable to extremes of temperature, but are 

 veritable deserts. Fig. 6 shows the monthly average 

 maximum and minimum temperatures of El Arish, 

 Aden, and Bahrein, all of which are in desert areas, 

 on the coast of the sea. One concludes that great 

 daily and annual range of temperature is a common 

 element of desert climates, but not an essential 

 characteristic. The bright sun shining unimpeded 

 on the desert soil heats it very rapidly, so that 

 by midday the temperature of its surface greatly 

 exceeds that of the air above it. 



Our knowledge of the temperature reached by 

 the surface of the soil is slight, but I hope shortly 

 to publish records which show that in summer in 

 South Palestine the surface of clay desert rises about 

 36° F. (20° C.) beyond the shade temperature at 

 midday. Nearer the Equator no doubt even higher 

 readings would be secured, but in Palestine surface 

 readings of 122-140° F. (50-60° C.) are normal. 

 Prezhevalsky has recorded similar figures for the 

 Gobi Desert, and adds that the surface of the soil 



