BY W. N. BENSON, 579 



sometimes occur in the igneous materail itself. There is thus less 

 reason in this case to doubt the possibility of a volcanic cone rising 

 above the surface of the sea. It must be noted, however, that there 

 is not any great thickness of agglomerate, uninterrupted by inter- 

 calations of radiolarian mudstone, so that the sea-floor must have 

 been sinking rapidly, and the islands, if formed, would not be of 

 long duration. The largest rounded boulders are in the base of 

 the series, lying on undisturbed claystones. The intercalated mud- 

 stones were not deposited on steep slopes, but are quite conform- 

 able with the claystones below^ the agglomerates, so far as can be 

 determined; and the upper members of the agglomerate series 

 show little or no sign of water-erosion. 



The mudstones, and pyroclastic rocks have a varying degree of 

 resistance to erosion. Strongly resistant bands, forming well 

 marked outcrops, may often be traced for some distance, others 

 die out rather irregularly. The map, in this region, does not pre- 

 tend to have more than a general accuracy. 



The mass on Cleary's Hill, which is taken to represent the base 

 of the series, owes its great width of outcrop, not to its thickness, 

 but to the fact that it slopes down the face of the hill. A certain 

 amount of faulting occurs where Cleary's Gully debouches on to 

 the Common, which makes estimates of thickness in this region very 

 unreliable. 



A second occurrence of the Baldwin Agglomerates is indicated 

 by the rocks west of the limestones in Spring Creek, forming the 

 ridge between the Manilla and Moore Creek roads. Here the 

 coarse conglomeratic character has quite disappeared; the rock is 

 merely a breccia, of medium grain-size, and the interbedded mud- 

 stones greatly predominate over the pyroclastic rock. The several 

 bands of the agglomerate occupy the whole of the western part of 

 the Tamworth Common, and, on the fextreme west, are bent into an 

 anticline. This anticline maj^ be traced northwards to Moore 

 Creek, but becomes rather flattened out. While much of the 

 material in the agglomerate in this region, may have been derived 

 from the centre of eruption near Cleary's Hill, there was evidently 

 another point of eruption towards which these rocks may be traced, 



