131 



the ranges increases. The waters tapped at limited depths in 

 such Tertiary plains are derived from soakage from the surface, 

 and vary considerably in the amount of saline matter contained 

 arising from local lithological features. The deeper-seated 

 supply is derived from waters flowing over the surface of the 

 rocks of the hills flanking the plain, meeting in their descent 

 permeable beds of the Tertiary cover, along which they are 

 conducted further and deeper into the plain. In both cases the 

 waters acquire in their passage the objectionable solid ingre- 

 dients, from which we may conclude that the saline property 

 increases with the increasing depth from the surface and with 

 the increasing distance from the hills. It yet remains to be 

 proved if a supply of better water may not be met with at the 

 base of the Tertiary strata, conducted there from the hilly 

 tracts along the slopes of the subterranean valley, which have 

 been rendered impervious to water by the decomposition of the 

 slaty rocks, and by the grouting over of the less impervious sur- 

 faces by the material thus formed. It is highly probable that 

 better water may be obtained there than in the other deeper 

 parts of these drifts, because the basal and marginal beds of 

 the Tertiary basin are for the most part composed of coarse 

 sands and gravel. It is extremely likely that the deeper- seated 

 waters in our Tertiary basins are impounded as in a lake, and 

 are consequently gaining in saline strength. Theoretically 

 such stores by being drawn upon should improve in quality. 



Waters when obtainable in the marine Miocenes are highly 

 contaminated with saline matter, if we except those regions 

 where from stratigraphical peculiarities and a large rainfall, 

 the saline ingredients of the water-bearing strata are as it were 

 constantly being flushed out. In other areas, as also in the 

 Pliocene drifts, where a horizontal impervious stratum lies near 

 the surface, the soakage of water becomes stagnated thereon, 

 and by evaporation through the overlying surface there is an 

 increasing tendency towards an accumulation of saline matter. 

 The influence of local lithological peculiarities on the character 

 of the subterranean water is well exemplified where gyspiferous 

 beds are intercalated among the sands and clays. Such con- 

 ditions, which largely prevail in the central districts of this 

 continent, as also in parts of the Murray Plain, must preclude 

 all hope of finding in them a water fit for use. The cause of 

 the superior quality of the water issuing from the Upland 

 Miocenes has been explained by Mr. Scoular, Trans. Eoy. Soc, 

 vol. iii., p. 110. 



Our chief water-bearing strata, both as regards quantity and 

 quality of supply, are of Palaeozoic age. These are for the 

 most part w^ell elevated, absorb a considerable share of the 

 rainfall, and represent at their outcrop about one-fourth of 



