98 
GEOLOOT. 
part of the island would not permit me to stay there lor the time 
necessary for exploring more closely the structure of these chains. j 
By examining the angular pieces of rock brought down by the 
mountain torrents, I obtained, however, an insight into, the 
formation of that wild mountain region. This central chain is 
flanked on its eastern side, as far south as Lake Roto-roa, by 
granite and gneiss granite, and has there been more denuded than 
on its western side, where, in the Tasman mountains, the Lyell | 
and Brunner ranges, Mount Alexander on the southern bank of 
the Inangahua, and Black-hill on the southern bank of the Grey, it 
forms, as before described, a wall of rocky mountains from G,000 to 
G,500 feet high, striking nearly north and south. The whole chain 
on its western side, where I ascended Black-hill, consists of gneiss , 
granite. In advance of this chain, and running parallel with it 
along the line of the Grey plains, we find conical hills and 
mountains, composed of a red porpliyritic granite, which has 
protruded into the chain, many remarkable examples of which are 
visible. Some of these mountains reach, as for instance in Mount 
Gore, to a considerable altitude, and I noticed that where these 
hills were highest, the gneiss granite chain to the east of them 
also attained its greatest elevation, and became distinguished by 
the ruggedness of its outlines and by its needles and peaks. This 
granite, probably of secondary age, as I shall show when I treat 
of the Grey and Buller coal-fields, breaks through the central 
chain in all directions, but without disturbing materially its 
general strike. It surrounds like a framework the sedimentary 
rocks, which tower amongst it in rugged masses, and it is in the 
lines of this framework that the courses of the principal rivers 
which traverse the mountain chain occur; and as my route led me 
mainly along the river courses, it will be seen that, with a very 
trifling exception, I travelled entirely over granitic ground. The 
only point on the western side of the chain, north of the Buller, 
where I saw this gneiss granite in situ, was at the Tata Island, 
whilst assisting my friend Dr. Hochstetter in collecting details for 
the geological map prepared by him. I am not able to say 
whether the porphyritic granite also exists near Separation Point, 
but, from what I have seen of the country, I infer that it will be 
found at the Wangapeka, in the great break which there occurs 
in the chain, the hills in the gap very much resembling in form ' 
those in the Grey plains. At the head of the River Owen, it is ;! 
seen protruding through the chain, and continuing in a southerly 
direction, flanking Mount Murchison on its western side, and is ' 
there lost sight of, being for the most part covered by tertiary 
deposits. On the eastern side of the Lyell range it again rises in 
large mountain masses, of which Mount Newton, about 4,500 feet 
high, lying on the right bank of the Matiri, is the highest. i| 
Thence, running in a northerly direction, in hills of smaller k 
dimensions, it divides the Lyell range from the Tasman mountains, , 
i 
