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GEOLOGY. 
123 
and as to the periods when the different changes before referred 
to took place. 
The first great change which I was able to trace occurred when 
the porphyritic granite was protruded, and which, at the western 
side ot the island, appears in such predominant masses. Before 
this event, which changed the whole form of the country, it 
appears that large tracts of level land existed, as indicated by 
extensive coal-fields, and thick deposits of grits and shales, in the 
formation of which large rivers had a considerable share. 
That huge masses of granite had previously existed is evident, 
seeing that in some places a granitic rock of greater age is 
traversed in tortuous veins by the porphyritic granite, and seeing 
also that the grits and shales of the coal formation are principally 
derived from the decomposition of that older rock. After this 
period of great disturbance, in the progress of which the moun¬ 
tains of the central chain took nearly their present forms, a long 
space of time evidently elapsed without any further great dis¬ 
turbance, as proved by the thick cretaceous deposits on the West 
Coast. These deposits were probably formed in a bay of con¬ 
siderable size, or between extensive islands, as shown by the 
breccia at Te-ana-o-Matuku and the remains of old sedimentary 
rocks near Cape Eoulwind. 
During that time the whole eastern side of the island was pro¬ 
bably also in the condition of dry land, no signs of cretaceous 
rocks having as yet been found there. But the quiet state of the • 
island which immediately succeeded the formation of the por¬ 
phyritic granites was at length again invaded. Eruptions of 
plutonic rocks took place, and whilst the western side of the 
island was raised high above the sea level, its centre became sub¬ 
merged. It was then that in all probability the eruptive masses 
of the Kaikoras made their appearance. 
Another long interval of repose succeeded, during which the 
large accumulations of the tertiary (miocene ?) period, which we 
find in the longitudinal fissure, and round Blind Bay, took place. 
These deposits were again upheaved by a fresh protrusion of 
eruptive rocks, diabases and porphyries, near Nelson and all 
along the western side of the Spencer mountains. It was then 
that the island assumed nearly its present physical character. 
We also have evidence of another disturbance which took place 
in the glacial period, during which the country sunk, as in other 
countries in the same latitudes, and afterwards, rising again, re¬ 
assumed its present position. % 
After the last-mentioned eruption of crystalline rocks, volcanic 
agencies began to work on the eastern side of the island, and 
thence an important change took place in the level of the 
country. These agencies are still at work, upheaving young ter¬ 
tiary strata and alluvial deposits, the former of which have already 
been raised to an altitude of nearly 2,000 feet, and the latter to 
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