I 
GEOLOGY. 95 
• • 
west to north-east, without breaking through them, as is the ease 
with the rivers on the western side of the island. It is therefore 
. certain that all the chains, without exception, on the eastern side 
of the longitudinal fissure, the Spencer mountains as well as the 
seaward Ivaikoras and their branches, both towards the north and 
the south, mantle round the inland Kaikoras, by which they have 
been upheaved; and this event occurred probably at the begin¬ 
ning ot the tertiary period, to which 1 shall refer when treating 
of the extensive tertiary strata which cover the longitudinal 
fissure. In what connection the eruptive and volcanic rocks 
stand to each other can only be determined when these mountains 
are thoroughly examined by the field geologist. 
Returning to the central granitic mountains, we meet, on their 
eastern side, to the north of the Buller, in the Owen river, a 
magni ficent porphyritic granite, with large rose-coloured orthoklas 
crystals, which protrudes into the other granite in large veins. 
This newer granite forms, more towards the north, low round- 
topped hills, which lie at the foot of the older white-coloured 
granites. At the head of the River Owen this porphyritic granite 
(which played, as I shall hereafter show, such an important 
part in the formation of the eastern side of this island) strikes 
towards the north, between the rocky mountain chains on both 
sides of the low saddle between this .river and the Wangapeka. 
In the eastern chain, a range of from 5,500 to 6,000 feet high, 
we not only find large beds of white crystalline granular marble, 
sometimes sacharoid, alternating with quartz schists, similar to 
those in the range between the Rivers Takaka and Riwaka (and 
also observed by Dr. Hochstetter in the gorge of the Wangapeka), 
but we also meet with some varieties with parallel lying mica, 
cipollin, and others with hornblende, &c. 
Some of the limestone strata do not exhibit the same highly 
crystalline structure; they are more compact, and show such a 
variety of colours, that no doubt in future years they will be highly 
valued as marbles for artistical purposes. Mount Owen itself, 
now isolated, but in reality the southerly continuation of the 
dividing range between the Buller and Wangapeka valleys, 
consists of old clay slates of a bluish grey colour; here and there 
a rock occurs, a metamorphic rock of the slate formation, which 
shows, by its dull greenish or brownish colours, and its intricate 
scaly structure, that it belongs to the cornubianites. Round 
Mount Owen, and at the western foot of the granitic ranges, we 
meet with tertiary strata of large extent, forming mountains, 
which reach in some places to an altitude of 2,500 feet above the 
level of the sea. On the northern side of the Buller, as well as 
near hlount JVfurchison, and near the Tiraumea plains, these strata 
st ri he very regularly, nearly north and south, with a dip of from 
fifty-two to sixty-eight degrees towards the west. The same 
strike is also observed in the Tutaki, but both there and at its 
