Haast,—On the Geological Structure of Banks Peninsula, 507 
showing some remarkable irregularity, is the one in which the so-called 
Ellis Quarry is situated.. This dyke, which strikes nearly east and west, 
goes out about 400 feet below the summit, where a saddle intersects the 
spur. Shortly above its lower termination it sends off a smaller branch in 
a south-west direction, also ceasing after a short course. Whilst the main 
dyke does not appear any more above the surface, the smaller south-western 
branch crops up again on the other side of the depression, now gradually 
changing its direction, so that, in its lower course, about 800 feet above the 
plains, it crosses the spur in a south-east and north-west direction. The 
whole system of dykes in the Lyttelton caldera wall is thus very different 
from the dykes of Mount Somma, of which, in his paper, Mr. R. Mallet 
gives us such a lucid and suggestive account, and of which many are 
fractured, displaced, and crushed, and have at the same time a wedge- 
shaped form. We can, therefore, assume that the fissures and dykes in the 
Lyttelton caldera were only formed after the latter had been so thoroughly 
consolidated that, after the formation of the fissures and their filling up by 
the principal dykes, no more changes of any importance took place in them ; 
and that, moreover, the forces by which the walls of the volcano were 
starred from top to bottom, must have been far deeper-seated and more 
effective than the agencies by which Mount Somma was rent, 
In conclusion, I wish to lay before you a few notes on the geological 
features of the Lyttelton and Christchurch railway tunnel, of which I made 
a careful survey during a number of years, as the work of the miner 
advanced. I watched this interesting and instructive work with great 
attention, this being the first time that a caldera wall of a large extinct 
voleano was to be pierced through. I prepared at the time a section on a 
scale of lin. to 20ft., which I have great pleasure in laying before you. 
The direction of the tunnel is N. 14° W. The first trial shaft was 
commenced in January, 1860, and the permanent works under contract 
with Messrs. Holmes and Co., began in July, 1861. The tunnel was laid 
out, and its execution solely superintended by Mr. Edward Dobson, C.E., 
Provincial Engineer. It was brought to a successful termination on May 
25, 1866, when both adits met near the centre. The opening for railway 
traffic took place on December 9, 1867. The total length of the tunnel is 
8,598 feet, and if we deduct from this 365 feet on the northern or outer 
side, and 105 feet on the southern or inner side, formed by slope deposits 
and loess, there remains 8,128 feet of rock of voleanic origin, of w. 
caldera wall has been built up. Classifying the rocks according to their 
lithological character, we find that the crater above the present waterline 
61 lava- , haying the character of a stony compact c or me T 
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