172 THE GEOLOGY OP DUBBO, 



" The country between Diibbo and the Castlereagh appears to be 

 formed of a coal basin, the centre of which is situated a few miles 

 north of Dubbo, and it is quite probable that the thin seams of 

 coal seen in the cliff at Ballimore may overlie others of a payable 

 chai-acter." 



In February 1883 the Rev. J. E. Tenison- Woods describes some 

 fossils from this district. [L. S., N.S.W.] This with my own 

 short paper (read on the 26th March) seems to be all at present 

 known of the Geology of Dubbo. 



Distribution of Rocks. — Sandstone is the prevailing formation. 

 It is not known exactly how far it extends towards the north-east. 

 Due east from Dubbo it extends about 30 miles and then gives 

 place to Silurian limestones and slates. The sandstones differ very 

 much in texture and composition in different localities. Generally 

 it is hard and durable when it lies under, or is in close proximity 

 to basalt. At Barbigal and at Troy a quartzite with a scarcely 

 perceptible granular structure is developed in this way, while in 

 many other place it is so friable as to weather into a shapeless mass 

 after a few months exposure. 



When exposed along creeks or in cuttings it presents all the 

 peculiar characteristics of the Hawkesbury sandstone. The faces 

 of the rocks are excavated by atmospheric influences and the 

 rending effects of crystallising salts, into caves and hollows ; the 

 false bedding, peculiar ironstone bands, and concretions, are 

 strongly suggestive of the sandstones on the eastern slopes of 

 the mountains. 



Conglomerates are met with at various levels in the series but 

 never preserving their character over any considerable area. The 

 shingle of an old water-course is exposed on the Talbragar near 

 Murrungundy. The deposition and " lie " of the shingle show— if 

 a solitary instance is of any value — the drainage to have been in the 

 same direction as in the existing river systeni. A thick bed of 

 conglomerate caps the hills over the coal at Ballimore. 



Surface indications of conglomerates are apt to mislead casual 

 observers in the country about Dubbo. In travelling over the 



