704 SUBANTARCTIC ISLANDS OF NEW ZEALAND. [Oeohgy. 



in abrupt cliffs almost everywhere. The smaller south-west portion of the island 

 is united to the main portion by a razorback ridge. The surface of this portion 

 is almost fiat, and is elevated about 500 ft. above sea-level. It appears to be an 

 old plain of marine erosion, and indicates a former lower level of the land. 



The only rock found on the island is a moderately coarse muscovite granite 

 of an even-grained character throughout. In colour it is almost white, but where 

 weathered it acquires a pink or even red tint. In section the structure is gneissic, 

 and many crystals show strain-shadows. The feldspar is mostly orthoclase, but 

 there is much oligoclase and a very little perthite. In a few spots a little micro- 

 graphic structure is to be seen. The muscovite is in large plates, sometimes bent, 

 and there are a few plates of biotite and a few crystals of garnet. 



Though this particular type of granite has not been recorded from Stewart 

 Island or elsewhere in New Zealand, it is not fundamentally different from many 

 of them, especially from some of those in Stewart Island, and it is reasonable to 

 regard the Snares as part of the same plutonic complex of which Stewart Island 

 and the south-west of Otago are composed. 



The greater portion of the island was traversed in search of specimens, but only 

 the one type of rock was found, and specimens from different localities were remark- 

 ably similar. The west coast in particular was visited, and it was found that the 

 columnar structure remarked by Hector was a result of the jointed structure of the 

 granite. 



