Physiography, Geology.] SUBANTARCTIC ISLANDS OF NEW ZEALAND, 725 



hood of the phenocrysts. The microlites are of a pale-green, alkaHne augite, with 

 high extinction- angle. They are elongated and straight, frequently with sheaf-like 

 termination, or with a ragged border along one side. The phenocrysts are of an 

 oligoclase-andesine, a green slightly pleochroic augite in fairly large crystals, and 

 with included grains of magnetite. An analysis of this rock is given above (C). 

 It shows distinct relationship to the trachytes, but is less alkaline in character and 

 more basic, with a very high percentage of ferrous iron and the very low percentage 

 of alumina which apparently characterizes rocks of this series. This rock is ex- 

 tremely like a trachytic pitchstone which occurs as a small dyke at Governor's Bay, 

 near Lyttleton, New Zealand ; in fact, the trachytes of Carnley Harbour show a 

 close resemblance to certain alkaline trachytes from this locality. 



There occur in the trachyte at times dark-coloured bands, apparently com- 

 posed of coarse black augites and small decomposed olivines, in a black crystalline 

 base. Under the microscope the groundmass of the rock is even-grained and fairly 

 coarse, with an ophitic structure in places. It is composed of long narrow twinned 

 laths of labradorite, grains of violet augite, and grains of olivine with borders and 

 seams of limonite, and a good deal of magnetite in squares and irregular grains. 

 The phenocrysts are of augite, in coarse, fresh, pleochroic crystals, with occasional 

 inclusions of small plates of feldspar, of olivine altered to serpentine and iron- 

 oxides, and feldspar as occasional small rectangles of fresh labradorite. This rock 

 is mineralogically a dolerite, and may be a dyke, but its field occurrence did not 

 suggest this as at all likely. 



In Hartmann's account of the basalt of Auckland Island he mentions the 

 occurrence of a series of trachyte older than the basalts, but without giving the 

 locality.* As the German expedition had its headquarters at Port Ross, and as 

 he does not mention the presence of gabbro or granite, it seems to be a safe inference 

 that there is an exposure of a trachyte near Port Ross in the same stratigraphical 

 position as that at Carnley. Want of time and adverse weather-conditions pre- 

 vented a thorough examination of the northern end of the main island. 



Specimens of trachytes evidently derived from dykes were picked up on the 

 shore of Coleridge Bay, but they could not be traced to their origin. The anortho- 

 clase in some of the specimens is very apparent. Another small specimen which 

 evidently belongs here, though it is more decidedly basic, contains numerous crystals 

 of a rhombic pyroxene ; this is the only case noted of the occurrence of this mineral 

 in the volcanic rocks of the group. The fragment was very vesicular, and deeply 

 weathered. Other specimens were found in the same locality with much chalcedonic 

 quartz filling vesicles, and the feldspars completely altered and partly replaced 

 by small crystals of epidote. Some of these specimens undoubtedly belong to the 

 trachytes, but others belong to the lower basic series, the underlying gabbro being 

 in close proximity to the place where the specimens were found. 



(3.) Camp Cove Conglomerate. 



The next formation in point of age is a conglomerate which is best developed 

 at Camp Cove, but extends in a northerly direction through the peninsula behind 

 the depot. The conglomerate is apparently an old river-deposit, or perhaps a shore- 



* " Ueber Basalte der Aucklands Inseln," by Max Hartmann : L.J., 1878. 



