Physiography, Geology.] SUBANTARCTIC ISLANDS OF NEW ZEALAND. 



737 



DISAPPOINTMENT 

 ISLAND. 



Disappointment Island 

 (fig. 15) is a small island, 

 from one and a half to two 

 miles across, lying five miles 

 to the west of Auckland 

 Island. It is not so high as 

 Auckland Island, but the 

 coast-line is, in general, bold 

 and precipitous. The sea be- 

 tween it and the mainland is 

 comparatively shallow, with 

 one prominent reef rising well 

 above sea-level, about half- 

 way across. The general 

 physiographical conditions 

 are the same as those of the 

 mainland. 



The island was visited 

 by Dr. Marshall during the 

 course of the expedition, 

 and the following statements 

 are based upon his notes. 

 Sir James Hector assumed 

 that the island represented 

 the centre, or core, of a great 

 volcano, and its preservation 

 was due to the greater power 

 of resistance of the plutonic 

 mass forming that core. This 

 is apparently not the case. 

 The main mass of the island 

 appears to consist of diabases 

 and melaphyres somewhat 

 similar to those at Musgrave 

 Peninsula. The structural 

 planes visible at the landing- 

 place have in general an east- 

 and-west strike, and a dip to 

 the south of 60°. In other 

 places these beds appear flat, 

 and then again bent into 

 folds. Cutting these rocks 

 there are nearly vertical 

 dykes of white rock striking 

 north-west and south-east. 



The petrological character 

 of the rocks makes it almost 

 certain that they belong to 

 48— S. 



