390 W. R. BROWNE AND A. B. WALKOM. 



andesite, and dacite, with patches of Permo-Carboniferous 

 quartz-porphyry conglomerate dipping off the eruptives or 

 filling in old valleys. The tuffs or breccias are of a some- 

 what different variety from those occurring at Drake's Hill 

 and Mount Bright. They are medium in texture, the 

 fragments being up to about two inches long, and ranging 

 down to microscopic dimensions. The inclusions comprise 

 fragments of cherty rock, rhyolite of various colours, 

 trachyte of a kind not met with in the flows of the district 

 and therefore probably of much earlier date, and fine-grained 

 green siliceous-looking rock probably closely related to the 

 green tuff of Drake's Hill and to another tuff found else- 

 where in the Matthews' Gap area. The latter seems to be 

 a variety of the rhyolite tuff. It is extremely fine-grained, 

 of a blue-green colour, hard and compact. Its chief differ- 

 ence from the Drake's Hill green tuff consists in the 

 presence of abundant felspars, largely idiomorphic, but 

 often with the appearance of angular fragments, suggesting 

 that they are of extraneous origin — not crystallised in the 

 tuff. 



Some other very fine grained tuffs are found occurring on 

 top of the coarser rhyolite tuffs, in particular that already 

 referred to as containing the Carboniferous plant fossils 

 Rhaoopteris and Cardiopteris, also an extremely fine- 

 grained greenish-white cherty tuff which is to be found on 

 the N.W. end of Mount Bright. Both of these are stratified, 

 and the Rhacopteris tuff is in places fractured and shattered; 

 the pieces having slipped on each other, excellent miniature 

 examples of different kinds of faulting have been produced. 



Trachyte is very abundant, and has followed directly on 

 the rhyolite and tuffs. It may be divided into two varieties, 

 leucocratic and melanocratic, this division being based on 

 a microscopic comparison of the two types. It is more 

 fully discussed below. The leucocratic trachyte is of a 



