Rain Producing Influences in South Australia. 101 



should be done to revive the ''dead heart of Australia." Without 

 any far-seeing policy or consciously-directed effort on our part,, 

 it is probable that the great inland lakes will gradually store 

 more and more water ; but surely the process is worth hastening. 

 For example, it might even be worth while to keep Lake Torrens 

 at least partially suppHed from Spencer Gulf. An improvement 

 of 20 per cent, in the rainfall of 20,000 square miles of country 

 is worth much money, a practical example of which is to hand. 

 The counties Granville, Hanson, Herbert and Lytton, which 

 form only a part of the improved rainfall area under discussion, 

 in 1918 carried 387,000 sheep and nearly 11,000 cattle and 400a 

 horses, numbers practically equal to those of 1891, the record 

 stock year for Australia. 



Storage Gains from Clearing. 



The preceding study teaches two important lessons. One is 

 that the clearing away of the forest covering from the whole of 

 our hilly areas, at all events, of those portions of the inland 

 foothills and mountain slopes in any way suitable for pasturage, 

 is distinctly beneficial, not only to its stock-carrying capacity, 

 but to inland climatic conditions as well, inasmuch as it greatly 

 increases the amount and constancy of the flow of the rivers. It 

 thus releases from day to day for storage in inland lakes and 

 reservoirs vast quantities of water which otherwise would be 

 thrown into the mountain, atmosphere, and to a large extent 

 cross the hills, eastwards and southwards, without condensation, 

 and so escape. A reason for thinking this is that the transpira- 

 tion and evaporation from the leaves of the upland trees must be 

 Uttle or none during the times of atmospheric saturation, but 

 are probably most vigorous during the bright sunshine and 

 drier air of the anticyclonic periods. This seems contrary to the 

 behaviour of the drought-resistant vegetation of the plains, which 

 has to adapt itself to extreme conditions, but it is not really so. 

 By mountain vegetation, more especially that of Victoria and 

 New South Wales, the strain of drought and heat is rarely felt 

 and so definite drought resistance is not often called for ; whereas 

 saturated air is a rare experience to the Mallee eucalypts and 

 their fellow strugglers, and heat and aridity so often have to be 

 endured that transpiration, if not checked, would exceed the 

 powers of their roots to make good. From the former, evapora- 

 tion is inopportune, both in time and place — from the latter in 

 time. 



