Bain Producing Influences in South Australia. 97 



most frequent towards evening, and widespread rains of tropical 

 origin seem to be helped by the atmospheric cooling during 

 night-hours. Thus the effects of lake evaporation might be post- 

 poned for several hours, and be first felt one or two hundred 

 miles away. 



Map showing percentage departures of the mean rainfall of the last 

 10 years, 1910-1919, from that of the 30 year period, 1885-1914. 



Rainfall Incongruities. 



The apparently haphazard mixing of small plus and minus 

 departures may often be due to difiference in elevation and 

 aspect of the rain stations used. For example, south from Lake 

 Torrens and west from the Willochra valley is some fairly moun- 

 tainous country on which the bulk of the rain would be caused 

 by ''southern" disturbances and accompanied by wind, whereas 

 on the lower ground or in lee of the ranges, the rains would be 

 more of "monsoonar' type. The latter would show the influence 

 of the lakes, the former might not. Then, of course, we have 

 to put up with the occasional neglect of the rain guage, 

 observers' carelessness, varying faults in the exposure of the 

 :gauge, etc. 



