BY VV. G. WOOLNOUGH. 793 



converted into a dense, glassy quartzite. This effect is very 

 -well marked in Portion 15, Parish Bumballa, at a spot called 

 ^* Devil's Hole"; and again, some distance further to the east, 

 near the sumaiit of Badgery's Track. 



At a local ceutre of eruption on Portion 16, Parish Wiugello, 

 basaltic tuffs are developed, which, by alteration, have given rise 

 to pisolitic bauxite. In these tuffs Tertiary leaves are preserved.^ 



Dykes are not very numerous in the district, but one occurs 

 at Badgery's Lookdown. Where it intersects the hard Permo- 

 Carboniferous sandstones and breccias, it has yielded to atmos- 

 pheric influences more readily than the surrounding rocks, and 

 forms a deep cleft in the pinnacle which constitutes the Look- 

 down. Below the Permo-Carboniferous rocks it forms a structure 

 which resists denudation better than the OrdovicianC?) slates, 

 and is responsible for the long spur by means of which Badgery's 

 Track descends to the Shoalhaven River. The continuation of 

 this dyke on the southern side of the river has not been traced. 



Contact- Metamorphism at the grano-diorite boundary. 



The contact-phenomena round the margins of the plutonic 

 massif are very striking. As we should naturally expect, it is 

 chiefly at the limestone-contact that the greatest effect is 

 produced. 



At Hogg's lime-kilns the limestones, though moderately crys- 

 talline, have scarcely been converted into marble. Remains of 

 fossils are still indistinctly visible. Following the western lime- 

 stone belt northwards to its contact with the eruptive mass, no 

 very great alteration is noticeable until that point is almost 

 reached. At the actual junction between the marble and the 

 eruptive rock, the latter is somewhat fine-grained and porphyritic, 

 and one does not meet true grano-diorite for nearly 100 yards. 

 The alteration in the limestone has followed parallel bands, 2-10 

 centimetres wide, converting them into fine-grained grey chert. 



•Deane, H., Records of Geol. Survey of N. S. Wales, Vol. vii., Pt.2, 

 j)p.59-65, Pis. 16,17(1902). 



