500 Transactions, == Geology. 
Returning to the orifice or orifices from which the material for the for- 
mation of the caldera wall was ejected, and to which also the numerous dykes, 
mostly having a vertical position, intersecting it, can be traced, it appears 
that the principal focus of eruption was situated a little to the south-wést of 
Quail Island, as the greatest portion of the dykes radiate from here, and 
tho eastern and southern sides of Quail Island, and the shores near 
Charteris Bay, are formed of tufaceous agglomeratie and brecciated beds, in 
which a number of angular blocks of rock are enclosed, having all a very 
bleached appearance. 
It would go beyond the limits of this address were I to follow the further 
genetic history of Banks Peninsula in all its details. I can, therefore, only 
indicate here in a few words how the whole, in course of time, has been 
built up. Simultaneously with, or shortly after, the Lyttelton caldera, the 
Little River caldera, of which only a small portion remains, was formed in 
the same manner. The formation of the largest of the whole series, the 
Akaroa caldera, is next in age, which, with the exception of a small portion 
of its northern rim, is perfectly well preserved. After their formation, new 
eruptions, and of a different form, took place south of the Lyttelton caldera 
and north of the Little River and Akaroa calderas, during which the highest 
portion of Banks Peninsula was built up—Mount Herbert, 8,050; Castle- 
hill, 2,900 ; and Mount Sinclair, 2,800 feet; only portions of the craters of 
these younger systems are still affi but easily recognized when 
standing on the summits of these mountains. The southernmost portion 
of the Lyttelton caldera was partly destroyed or covered by lava-streams 
belonging to the Mount Herbert system, also of a basic (basaltic) nature, of 
which a whole series flowed into it, now forming the huge spurs descending 
from the summit of Mount Herbert into the harbour between Charteris 
and Rhodes Bays. The last eruption, of a submarine character, took 
place in the centre of the Lyttelton caldera, by which Quail Island was 
formed. 
I shall now proceed to offer you some observations on the system of 
dykes, which are so well developed in the Lyttelton caldera. The most strik- 
ing facts in connection ud wA system of dykes of the caldera, and to 
which I have devoted id ttention, are their size, longitudinal extent, 
and constancy in direction. From the Wi of numerous observers, 
it has been proved that all the dykes of Mount Vesuvius and Mount Etna 
do not extend much beyond the centres of eruption, so that they advance 
only a short distance, and, rapidly thinning out, soon disappear, a fact 
which my own observations along the crater walls of both mountains have 
amply confirmed. However, I have no doubt that other volcanoes similar 
in construction to Banks Peninsula, and differing as considerably from 
