110 ira. w. j. cluNtes ross on thb [May 1894, 



Scattered through the mass of the rock are patches of fine-grained 

 granite, largely composed of black mica. The rock is traversed, 

 moreover, b) r veins of a granite differing considerably from that 

 which surrounds them. These veins are common in the decomposed 

 granite, but have themselves apparently undergone very little. decay. 

 Some are very fine-grained, while others are excessively coarse, and 

 these often occur very close together. All are alike made up of 

 quartz and pink orthoclase, often coated with scales of nearly white 

 mica. 



Near the boundary of the granitic area there is a change in the 

 rock, and it approaches in character that found in the veins, the 

 biotite and hornblende disappearing or becoming scarce, the former 

 being replaced by muscovite, and the felspar being of a reddish 

 tint. 



At certain localities in the district several other varieties of 

 granite occur. Thus, at Locksley, about 15 miles east of Bathurst, 

 there is a fine porphyritic granite, very similar in appearance to the 

 Shap granite of Westmoreland, and at Sarana, still farther east, 

 there is a rock composed of white felspar and quartz, with little 

 mica, approaching a pegmatite in appearance. The granite near 

 the boundary of the metamorphic area affords good examples of 

 granophyric or micro-pegmatitic structure. 



2. The Age of the Granite. 



One can hardly speak with much confidence as to the age of the 

 granite. It is clearly newer than the Silurian rocks, since it sends 

 veins into them, and there is a broad zone of rocks altered by 

 contact-metamorphism surrounding the granite. Whether it is 

 newer, as a whole, than the Devonian rocks is doubtful. The latter 

 are certainly folded to some extent, but not nearly so much as the 

 Silurian. They are traversed in places by what appear to be 

 intrusive dykes of felstone, highly siliceous, and often porphyritic. 

 In some cases they rest directly on the granite, and at Bydal the 

 late C. S. Wilkinson described them as being altered at the 

 contact. Near Lithgow the granite is overlain by rocks of Carboni- 

 ferous and Permian age. 



On the whole, the writer is inclined to think that the granite is 

 not all of the same age. The first intrusion may have taken place 

 subsequent to the deposition of the Silurian, but prior to that of the 

 Devonian rocks, and there may have been a second intrusion, 

 accompanied by further tilting and crumpling of the Silurian and 

 disturbance of the Devonian strata, which sent veins of felstone 

 into them, and converted many of the sandstones into quartzite. 

 The different character of the granite at the centre and near the 

 boundary of the area seems to support this view, although it is not 

 easy to draw any boundary-line between the two types ; but this 

 may be owing to the fact that most of the country is covered with 

 soil and under cultivation, so that good exposures are only attain- 

 able at places some distance apart. The series of veins which 



