200 ALEX. L. DU TOIT. 



gradually displaced the residual waters, that had been 

 throughout Cretaceous and early Tertiary times either 

 stagnant or imperceptibly circulating through the sand- 

 stones, this action being hastened by the westerly tilt that 

 in late Pliocene or Early Pleistocene times produced a 

 movement of the water-body in that direction. At the 

 same time, as erosion laid bare the intake beds by stripping 

 off the cover of basalt and Desert Sandstone, a progressively 

 greater area would become exposed and available there- 

 fore for the absorption of the rainfall, and it might be 

 remarked that in a rough manner the marginal waters are 

 fresher opposite those sections of the intake, off which the 

 volcanic rocks have been denuded. 



It was moreover just then that glacial conditions set in 

 over Australia, whereby heavier precipitation was brought 

 about upon the Main Eastern Divide and the intake area 

 more fully supplied. 



The static pressures induced over the centre and further 

 side of the Basin became excessive, and, taking advantage 

 of the contact of the Mesozoic strata with the older rocks, 

 and of the marginal coarseness of the Cretaceous beds 

 along both the main boundary of the Basin and the borders 

 of any inliers, the water burst up to the surface over more 

 than half of the periphery, and a steady flow was established 

 with concomitant westerly fall of the potential surface. 



The process of elimination of the saline "residual water" 

 would be effected by these, the Mound Springs, while in 

 their turn the magmatic waters would be in process of 

 replacement at the intake by rainfall ; when the Salinity 

 Diagram is compared with that showing the Isopotentials 

 (and therefore the direction of flow), the general correct- 

 ness of this reasoning is strikingly confirmed. 



The fresh meteoric additions make their appearance due 

 north of Richmond, between Barcaldine and Charleville, 



