INTRODUCTION 



II 



and Dorsale, in the center; Matmata, in the south. While the 

 effect of each of these mountain chains is important climati- 

 cally, the ranges of Mogod and Matmata have perhaps the 

 greatest direct influence of all, from the foresters' standpoint, 



FIG. 2. Map of Tunisia and Algeria. 



by protecting local forests from the devastating dry winds of 

 the desert. 



Winds, Temperature, Humidity. - - The direction of the 

 winds of Tunisia may in general be predicted in their seasons 

 with reasonable accuracy. In winter the dominant wind is 

 from the northwest; in the spring, from the northwest with a 

 tendency to north. In summer it changes to northeast, es- 

 pecially in the south, where this is the prevailing direction in 

 autumn, though above the Dorsale the autumn winds arise 

 more often from the northwest. 



The temperature in Tunisia is high to moderate, in summer 

 reaching an average of 28 C. (82 F.) to 32 C. (90 F.) ; in winter 

 a minimum of from 3 C. (37 F.) to 8 C. (46 F.). As a matter 

 of fact it varies according to the elevation above sea level as 

 is shown by the following table: 



