Figure 2. 

 Hour by Hour Changes in Temperature 



Fig. 3 shows the range of combined temperatures and relative humidities covere 

 by hourly observations in the shade on the south side of the wady, calculated from 

 sling- psychrometer readings. In August air temperatures ranged from 21° to nearly 

 37°C and relative humidity from 95% in the early morning to 17% in the late afternoon. 

 The range of humidity was slightly less (with distinctly lower temperatures) in March, 

 but reached almost to saturation in December. In this latter week there was, however, 

 a sudden change of air moisture resulting in an unusual range of combined temperature 

 and humidity. 



For comparison with the extreme desert conditions in August there is shown the 

 range covered by 24 hourly records taken at sea in the Mediterranean one day in August. 

 The contrast speaks for itself. 



As some insects and other animals are known to be active in the low light inten- 

 sity both at dusk and at dawn, the dusk and dawn records are shown individually in 

 Fig. 3, indicating the very wide difference between the cool damp morning and the warm 

 dry evening conditions. 



As many animals burrow in the sand in deserts by day time, perhaps to escape ex- 

 treme conditions, special attention was paid to changes in temperature at different 

 depths in the flat topped sandy areas which were found here and there along the dried 



21 



