ARID PORTIONS OF SOUTH AUSTRALIA. 



15 



The region having the highest rate of evaporation is in the western 

 part of the central portion of the continent. At Cue, for example, 

 there is a record of 156.02 inches in one year. This amount far exceeds 

 that reported for Aden, on the Indian Ocean, and Calexico, Cahfornia 

 (MacDougal, 1914:6), but is not so great as reported for Ghardaia, 

 Algeria, which is 5,309.7 mm. or 17.5 feet (Cannon, 1913:9). 



Fig. 6. — Graphs, after Hunt, showing average monthly rainfall and mean monthly evaporation, 

 in inches, for various places in Australia. 



Relative Humidity. 

 The relative humidity isopleths when plotted on a map of Australia 

 parallel fairly closely the coast-line (Taylor, 19182:8). Hence they are 

 concentric. Other interesting features are the relatively large area 

 which hes within the 40 per cent relative humidity isopleth, which is 

 approximately 27 per cent of the continent, and the changes in area of 

 the region included within this isopleth with its north-south seasonal 

 movement. These features are illustrated in figures 7a and 76. 



