;334. Albert V. James: 



the quartz by its cleavage, ■which is easily picked out, and by 

 the numerous and characteristic inclusions. A little tourmaline 

 is found in a f&\\ sections, but secondary quartz is present in 

 abundance in all. 



The hornfels close to the contact is very much coarser than that 

 some distance away. 



Owing to the quantity of sandstone which characterises the palaeo- 

 zoic rocks of this area, a considerable amount of quartzite has been 

 formed, much of it being tliermal metamorphic in type. 



It is interesting to note the difference between the action of run- 

 ning water and the weather on these metamorphosed sediments. 

 They appear to be highly resistant to the latter, but readily suc- 

 cumb to the former, owing to the presence of three sets of joint 

 planes, which divide the^ rocks into variously shaped rliombohedra. 

 The result is that the stream in flood can break out the rhombs 

 and thus deepen its bed, whereas the ordinary atmosi^heric agents 

 are not so succes-^ful. The importance of jointing is shown near 

 Hanging Valley, where a metamorphosed fault rock of the same 

 material as the hornfels around it has more sucessfuUy resisted 

 •destruction by Deep Creek. The fault rock is not jointed, and the 

 normal hornfels is, thus enabling the stream to remove it block by 

 block. 



Granod/orite. 



Six outci-ops are mapped, three large and three small, and they 

 roughly form a ring round Bulla. 'Ihe boundary of the north- 

 -east outcrop is hidden ])y later detritus, that has gravitated down 

 h-om the east. The five outcrops to the north stood out as islands 

 in t])e lava flood, but the most southerly Avas overwhelmed by it. 



(liemical Character. — The material for analysis was obtained 

 from fresh rock that had been " plug and>-feathered " on the main 

 ^outcrop soutliwest of Bulla. 



It was analysed by Mr. F. Watson, and the analysis is given 

 in the following table, together with analyses of other similar 

 vTOcks for comparison : — 



