GENERAL SUMMARY AND CONCLUSIONS. 7 1 



made by the writer in the open desert between Ouargla and Touggourt, 

 in November, 19 10, showed a variation of temperature of 24.7 C. between 

 3 o'clock in the afternoon and 6 o'clock the following morning. 



The absolute maximum temperatures in southern Algeria are fairly high. 

 At El Golea, for example, they are 47°, 46. 5 , 48 , and 49. 2 C, while at 

 In Salah, about 700 miles from Algiers, the maximum temperatures for 

 four years have been found to be 50 , 49. 2 , 50 , and 48 C. It is interest- 

 ing to note that at Ouargla, which is much nearer the coast than In Salah, 

 even higher temperatures have been recorded. The maxima for as many 

 years are as follows: 50. 2 , 51. o°, 52 , 49°, and 48. 4 C. Usually in winter 

 freezing temperatures are experienced at all stations in southern Algeria. 



Very little has been done on the soil temperatures in the desert region, 

 but at Ghardaia, in July, 191 1, the temperature of the soil 15 cm. beneath 

 the surface of the soil ranged, maximum from 3 6° to 37 C, minimum 

 from 31 to 33 C, giving an absolute range of 6° C. 



In addition to the rainfall, the evaporation, and the temperature, there 

 is another important climatic factor which should be taken into account, 

 but which can not be stated in accurate terms, i.e., air-currents. It is a 

 matter of common experience that one rarely observes a calm day on the 

 desert, but that usually the wind, which is often of considerable force, is 

 found to be blowing. This is unquestionably an important factor in raising 

 the total of evaporation and therefore in increasing the arid conditions of 

 this region. The winds which are most effective in the direction mentioned 

 are those which come from the desert and are known as the "sirocco;" 

 these are most likely to blow in spring and summer, although they occur 

 in autumn also, and to a very limited degree in winter. When the winds 

 blow from the north cooler conditions occur, the relative humidity is lower, 

 and therefore the evaporation rate is less. The sirocco, or desert wind, 

 crosses the Mediterranean and is sometimes felt in southern Europe. It 

 does not generally last more than three days at one time, but at Batna, in 

 July, 1902, it was reported for eight consecutive days. When the sirocco 

 blows the humidity is likely to be markedly affected; for example, at Batna 

 during the eight-day sirocco alluded to, the relative humidity fell from 25.6 

 to 16 per cent on the first day. 



SOME EFFECTS OF TEMPERATURE AND RAINFALL IN SOUTHERN ALGERIA. 



While it is recognized that, generally speaking, climate shapes the char- 

 acter of the vegetation, its immediate effects can not well be measured, or, 

 at least, have not been accurately measured, so that it seems necessary to 

 confine one's observations to supposed or probable effects, however unsatis- 

 factory this may be. So far as suits the present purpose, climatic effects 

 may conveniently be separated into those which are direct and those which 

 are not direct, remembering at the same time that the division is purely 



