496 Transactions.—Geology. 
deep indentations, forming splendid harbours, enter far into the outer rim 
of the mountains, passing for a considerable distance along the higher 
central range. Similar indentations are also found to exist towards the 
Canterbury plains, but they have either been already filled by alluvial 
deposits forming fertile valleys, such as the Kaituna valley, or they appear 
in the form of a lake (Lake Forsyth). In examining the nature of the rocks 
of which the system under consideration is composed, we find that, with 
the exception of a small zone at the head of Lyttelton Harbour, the whole 
is composed of volcanic rocks ; that the deep indentations are ancient crater 
walls, so-called calderas, into which a channel with precipitous walls, the 
barranco, leads; and that they consist of a series of lava streams, with 
agglomerates consisting of scoriæ, lapilli, ashes, and tufas interstratified 
with them. These beds have alla qua-qua versal dip, that is to say, they 
all incline outwards from the centre of the cavity. The higher mountains 
in the centre consist also of voleanie rocks of a similar composition, which 
appear either horizontal or, when the direction of the lava-streams com- 
posing them can be ascertained, are found to flow into the calderas 
previously formed, from which we can at once conclude that they are of 
younger origin. Finally, we find mostly in or near the centre of these deep 
cavities, or calderas, either a small island or a peninsula stretching so far 
into these harbours. They consist also of voleanie rocks, having been 
preserved above the last centre of eruption. This last sign of vuleanicity is 
on a smaller scale than the previous ones. The whole of Banks Peninsula, 
measuring along its longest axis from north-west to south-east, has a length 
of 31 miles, with a greatest breadth of 20 miles, and if we do not take the 
numerous indentations into account, it has a circumference of 88 miles, 
which corresponds closely with that of the base of Mount Etna. 
Having thus given an outline of the general features of the volcanic 
system under consideration, I shall now proceed to offer a short history of 
its origin. 
The oldest rocks in Banks Peninsula form a small zone of paleozoic 
sedimentary strata, possessing a slightly altered structure, many of them 
forming beds of chert, others, peculiar light-coloured brecciated schists ; 
however, sandstones and dark clay-slates are also represented. This zone 
has a north and south direction, and reaches to the southern watershed of 
McQueen’s Pass, which leads from the head of Lyttelton Harbour to Lake 
Ellesmere. Near this pass, slates appear as high as 600 feet above the 
sea-level. On the western slopes of Castle Hill, the south-western cotinua- 
tion of Mount Herbert, 2,900 feet high, which rises so conspicuously above 
Lyttelton Harbour, they reach an altitude of nearly 1,000 feet, where they 
are overlaid by the older lavas, forming the Lyttelton Harbour caldera, 
NL ML V MM RL ie or ca eR EI Mari ca 
RR bene Carer Se re ee ee D d 
