BY THE REV. J. MILNE CURRAN. 217 



more water-worn pebbles can be found, it may be taken for granted 

 that the highest point of the drift and the lowest point of the 

 basalt have been reached. The weathered surfaces of the rock on 

 the hill tops show no evidence of the prismatic structure under- 

 neath. This prismatic structure may be seen in the quarries 

 referred to. They are situated on the line A — B. The columns 

 are utilised in their natural state for kerb stones. They break in 

 some directions with a conchoidal fracture, while in other directions 

 the stone can be broken in parallel flakes. From Perth the basalt 

 may be followed without a break to the point marked L. Here 

 there is an isolated hill with a basaltic cap, known as the Pinnacle. 

 The table-topped hill overlooking Evans' Plains is the next remnant 

 of the once continuous sheet. Then there is a long break to Mt. 

 Pleasant, near Mr. Stewart's residence. Perth and Mt. Pleasant 

 are the extreme points of the basaltic flow around Bathurst. Of 

 course these points were not the original limits of the basalt 

 plateaux. Allusion has been already made to the source of this 

 basalt. Mr. Wilkinson pointed out that the stream came down 

 from the neighbourhood of Swatch field. Possibly a microscopic 

 examination of the Swatchfielcl basalts could throw light on 

 this question. It is certain, however, that no volcanic " neck " or 

 traces of a crater exist within a radius of ten miles of Bathurst. 



Very little has been done to expose the drifts under the basalt, 

 so that some idea may be gathered as to the nature of the old 

 valley. Along some points, where the basalt has been entirely 

 worn away, there is an abundance of silicified wood strewn about 

 the surface. This, no doubt, has been derived from the drift, and 

 shows that the river valley flowed through a forest-clad region. 

 At the present time the ridge of basalt forming the Bald Hills 

 stands from 400 to 600 feet above the surrounding country. In 

 the pre-volcanic days it was of course the lowest point. We have 

 here, then, a splendid example of the effects of subaerial denuda- 

 tion. The old mountains and valley have both disappeared, and 

 the untiring hand of Nature has spread out the material of which 

 they were composed over the great tertiary plains of the interior. 

 In this connection I must draw attention to a fact oftentimes 



