258 Geology of 



since my last journey in 1868 to the "West Coast, from which it 

 appears that the silky clay slates are altered in many localities by the 

 intrusion of granites and syenites into micaceous and gneissic schist, 

 the change from the one to the other being gradual and very 

 instructive, as may be seen from a series of specimens. 



It thus appears that there are at least two series of beds included 

 in my Westland formation. Owing, however, to the short time at my 

 disposal when at the West Coast, I was unable to separate these. 

 One is probably of the same age as my gneiss granite formation, 

 forming the western base of the Southern A]ps, and the other of 

 much later origin, the slates and sandstones belonging to it having, in 

 their turn, become changed into metamorphic schists in many localities, 

 by plutonic action. 



Igneous Rocks. 



The Canterbury Museum possesses a series of igneous rocks 

 collected in this zone, which are very varied, ranging from a coarse- 

 grained granite to a very fine-grained petrosilex. In the Geological 

 Map, I have indicated the occurrence of granite in the isolated 

 Mosquito Hill on the northern banks of the Haast river, but Mr. Gr. 

 Mueller informs me that, according to his observations, the whole hill 

 consists of blue clay slates with a capping of alluvium on the very 

 summit. In 1S63, when passing along the northern banks of 

 this river, which, for some distance from the western base of the 

 Southern Alps, had consisted of alluvium, I came, opposite the Mosquito 

 Hill where I camped, upon a number of very large blocks of granite, 

 mixed with some smaller fragments of clay-slate, showing convincingly, 

 from their sharp edges and the manner of deposition, that they had 

 not travelled any distance. Some of the blocks consisted of a very 

 fine white hornblende granite with black and silvery mica, the latter 

 in large concretions, and the hornblende crystals, also large and 

 needle-shaped, which, from the contrast of colour, gave a very fine 

 appearance to this rock. Another good-sized block with large crystals 

 of felspar (orthoclose) and plates of mica, was traversed by veins of a 

 fine-grained granite, the whole again crossed by veins of quartz. The 

 clay slates were of the usual silky nature. The whole appeared to 

 have either been brought by a slip from Mosquito Hill, or to be perhaps 

 the remnant of a ridge which had once united that hill with a similar 

 isolated hill lying opposite to it on the southern bank of the Haast. 



