194 ALEX. L. DU TOIT. 



X. The Relation between Volcanism and the Artesian 



Supply. 



The suggestion made by Gregory of a probable intercon- 

 nection between the Artesian water and Tertiary volcanicity 

 is a fruitful one and worthy of elaboration, for it is worth 

 observing that De Launay 1 has shown how in Europe there 

 is an almost absolute restriction of springs with free C0 2 

 to the regions of Tertiary and recent volcanic activity, e.g., 

 the Auvergne, Bohemia, the Carpathians, Appennines, etc. 



It is not surprising, therefore, to find both high potential 

 areas in Queensland still possessing considerably developed 

 though now much dissected cappings of the presumably 

 earlier Tertiary basalts (Diag. III). In the northern area 

 the lavas stretch westwards across the Rolling Downs 

 series for some distance down the Flinders valley, and in 

 the opposite direction cover a wide region about the head- 

 waters of the Burdekin river. They are linked to the 

 southern area by the flows around Clermont and Springsure. 2 



Further to the south-east again basalts crown the Bunya- 

 Toowoomba watershed, and are represented in New South 

 Wales, between Yetman and Warialda, Moree and Narrabri 

 and around Dubbo. 



There can be no doubt from the number of outliers scat- 

 tered around each of these detached centres, that these 

 basalts must have had in Miocene times a very much wider 

 distribution, and it would appear not unreasonable to sur- 

 mise that they formed a belt — interrupted perhaps only 

 here and there — extending the full length of the present 

 eastern margin of the Basin. 



It is significant again that, while they lie upon palaeozoic 

 rocks now and then outside the Basin and within it upon 



1 L. De Launay, Recherche, Captage et Anienagement des Sources 

 Thermes Minerales, Paris, p. 130, 1899. 



2 Jack and Etheridge, Geol. and Palffiont. Queensland, pp. 581-6, 1892* 



