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ALEX. L. DU TOIT. 



definite enough to enable practical use to be made of it t 

 though the principle of absorption is not denied. 



The figures quoted by Pittman 1 certainly show that the 

 respective run-offs of the two rivers are very different, yet a 

 closer examination of the data reveals certain discordances. 

 The twofold table that he presents, supplies figures for the 

 Darling, both at Wentworth and at Bourke for the years 

 1895-1903, and a comparison of the readings indicates 

 that there must be large losses in the flow between these 

 two points (outside the Basin) due to evaporation and 

 soakage. 



Secondly, the catchment of the Darling has a mean annual 

 temperature of fully 6° F. higher than that of the Murray, 

 while a relatively larger proportion of it lies within the 

 region of lower rainfall, where presumably the mean 

 humidity is less. Until the relative value of each of these 

 factors can be more correctly gauged, the lower discharge 

 of the Darling ought not to be presumed as wholly or even 

 in part due to the absorption of head-water run-off by the 

 intake beds. 



Certainly the reasoning of Mr. L. A. B. Wade "that the 

 losses by evaporation, absorption and other causes on the 

 Darling catchment, exceed by more than three and a half 

 times the losses on the Mildura (Murray) catchment" is 

 fallacious. Actually the annual "total loss" on the Darling 

 for the period 1891-1911 is 20*56 inches of rainfall (2266 

 -21) out of 22*66 or 91%, that of the Murray similarly is 

 64%; their ratio is therefore 1-J to 1 nearly, but how far 

 this inequality may be due primarily to absorption and not 

 to evaporation is still left undecided. 



That the rainfall could be rapidly absorbed by the porous 

 sandstones with their overlying sandy soils along the eastern 



1 E. F. Pittman, The Great Australian Artesian Basin, pp. 8 - 12, 1914. 



