CLIMATE OF AUSTRALIA. 



369 



long succession of graduated isothermal lines, with a mean temperature ranging 

 from 78° or 80° F. in the extreme north to not more than 54° in the extreme 

 south. But this gradual decrease does not correspond uniformly with the change 

 of latitude, for the normal averages are often greatly modified, raised in one place, 

 lowered in another, by the influence of the prevailing winds, marine currents, and 

 mountain ranges. Thus the temperature is diversely affected by the backward 

 flow of the equatorial and polar currents, which meet on the coasts of Queensland 

 and New South Wales. The contrasts are also always great between the opposite 

 slopes of the higher ranges, while in the deserts of the interior, as in the African 



Fig. 159. ISOTHEEMALS OF AUSTRALIA. 



Scale 1 : 45,000,000. 



900 Miles. 



Sahara, the extremes of heat and cold present enormous discrepancies, according 

 to Sturt as much as from 16° to 122° F. and even more.* 



In Australia the normal wind is the south-east trade, which prevails in the 

 lower, while the opposite north-west trade sets regularly in the higher atmospheric 



* Climate of various Australian towns : — 



