1 04 E. T. Quayle : Rain Producing Influences. 



Now it is more than probable that in the struggle for existence 

 our perennial vegetation has been its own undoing. The very 

 means it has been compelled to take for its own protection 

 have made the climatic environment progressively worse. 

 Whether distinctly drought-resistant or not, it must regulate 

 transpiration so that it is never unduly accelerated with the result 

 that the hot spells leading up to rainy conditions find inadequate 

 response in evaporation from the country beneath, while the 

 comparative coolness of the shaded land surface helps to prevent 

 convectional action and lessen the frequency of thunder-showers. 

 Moreover, the blocking of the water channels and the prevention 

 of erosion, the drying of the subsoil, and consequent lessened 

 flow from springs owing to the large moisture requirements of 

 the trees all tend to hold the water up against the eastern moun- 

 tain slopes, where its evaporation is comparatively ineffective in 

 rain production, and away from the depressions in the interior 

 where its evaporation would be most effective in rain production. 

 Hence the increasing dryness of the interior and the gradual 

 contraction of the belt of perennial vegetation towards the inland 

 slopes and foothills. 



It therefore follows that pastoral occupation must be assisting 

 to reverse the process of dessication. The destruction of the 

 forest trees in the more favoured belts, and the substitution of 

 grass and annuals for the more drought-resistant trees, and even 

 for the scrub and herbage perennial growths inland, are aids in. 

 the local production of rain, while the firming of the surface soil 

 and the formation of tracks! to water by stock help to make 

 surface drainage better. Then the tapping of artesian and sub- 

 artesian water supplies, though probably only a minor influence,, 

 must help to increase atmospheric vapour supplies and tend to 

 rain production. Much injury is in parts unfortunately being 

 done to the fine surface soil covering of the plains, but where the 

 plough is used this is arrested. 



The filling of Lake Eyre though a most attractive proposition, 

 is perhaps an impracticable one, but water storage and irrigation 

 for large portions of the north-western and western divisions of 

 New South Wales seem possible, and if carried out whole- 

 heartedly, would surely have beneficial results to the inland 

 climate of that State almost incalculably great. The addition of 

 two inches of rain annually seems quite possible, and that would 

 carry wheat cultivation westwards to the Darling River. 



