CLIMATE OF ALGERIA. 



13 



maxima are 50.2", 51°, 52°, 49°, and 48.4° C. On account of the fact that 

 in the western Sahara at these stations in \\dnter there are usually freezing 

 temperatures, the yearly range of temperature is 50.0° C, or over. The 

 greatest range reported for the western Sahara is that for Ghardaia as 

 given by Engler, namely, 57°, from -7° to 50° C. At Timmimoun, 1904, 

 the range was from -3 .0° to 53 . 1° C, or one of 56. 1° C. The extreme abso- 

 lute daily range in temperature on the desert appears not to exceed that 

 of certain stations on the High Plateau, although, as shown below, the 

 temperature variations on the desert may be much larger than the records 

 indicate. At Laghouat and at Ghardaia the thermometers which I exposed 

 showed a daily range of from 10.5° to 12.5° C. only. The instruments 

 were placed on the outside of buildings, and usually on the second story. 

 As a contrast to this observed diurnal variation, an opportunity was given 

 to take temperatures on the open desert at a time when the days were 

 fairly warm and the nights were rather cold. The place was between Toug- 

 gourt and Ouargla. At 3 o'clock on the afternoon of November 26, 1910, 

 the shade temperature at the place in question was 23° C. During the 

 night the thennometer registered -1.7° C. as the minimum, thus showing 

 a drop of 24.7° C. in something over 12 hours. Table 9 gives the extreme 

 daily range in temperature for three years observed at the stations named. 



A further examination of the maximum temperatiu-es shows certain cli- 

 matic features of interest and of great importance as factors in the environ- 

 ment of the desert plants, especially the high average maxima and the 

 large amount of heat received in the desert, as indicated by a summation 

 of the maximal temperatures. That the greatest daily temperatures must 

 be high is indicated by table 10, which gives the average maxima for three 

 to five years at three typical desert stations. 



The maximum temperatures show that the total amount of heat re- 

 ceived on the desert, as compared to that received in the climatic provinces 

 nearer the sea, is not only great, but also that the amount is variable on 



