PROBLEM OF THE GREAT AUSTRALIAN ARTESIAN BASIN. 205 



accession of surface water, which is not only in its turn 

 displacing the earlier accumulation, but also carrying salts 

 in and downwards from the actual outcrop. Whether this 

 stage is marked by the eastern edge of the belt of moder- 

 ately high salinity running from Winton to Oharleville is 

 problematical, but to the east of Roma, little water seems 

 to be passing westwards into the reservoir, and probably 

 for this reason the beds have remained saline there. 



In opposition to Gregory, however, the meteoric supply 

 is believed to be the predominant one, and the contribution 

 from plutonic sources subordinate in amount at the present 

 day, yet of the water actually stored, and now available, 

 quite a large, possibly the greater, proportion may have 

 been derived from other than meteoric sources, as 

 suggested. 



In concluding, a few words might be said in reference to 

 some of the problems of the Basin that await investigation. 



One of the most important of these is the delimitation of 

 the Cretaceous and the Jurassic beneath the surface, and 

 the probable existence and distribution of Lower Cretaceous 

 Artesian horizons. A second is the nature of the Artesian 

 series on the eastern and south-eastern margin, and their 

 stratigraphical relationship to the Triassic and Permo- 

 carboniferous strata there. A third is the investigation 

 of the Tertiary igneous lavas, intrusions and volcanic 

 centres, both with special reference to their behaviour 

 towards the Jurassics, and regarded as a source of deep- 

 seated waters and of carbon dioxide gas. The geological 

 survey of the two high potential areas ought to furnish 

 valuable data on a number of points. 



On the physical side numerous lines of inquiry suggest 

 themselves, such as the downward rate of temperature 

 increment, both of the strata and the waters they yield, 

 the variations just above or within the main flow, the 



