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Geology and Physical Geography : 
rock masses through fissures, and generally against the overlying 
sediments. This pressure, produced by the contracting crust, 
would suffice to produce volcanic outbreaks, without calling in 
aid ‘ waves of the molten interior/ &c. Nor could steam ho 
called in to produce the upward motion of the molten rock until 
it, (the rock) roso to within such a distance of the surface that 
the pressure of the column of rock (or of molten rock) was no 
longer sufficient to keep water fluid/’ 
The occurrence of auriferous quartz-veins in bolts may — assum- 
ing the above supposition to be correct — be duo to the circum- 
stance that a greater amount of gold was deposited in certain sets 
of layers than in others, and that when the rocks were uplifted 
from a horizontal to a vertical position, those bands which con- 
tained most gold yielded the largest supply for deposition in the 
quartz-veins, while in others containing little or no gold only poor 
or barren quartz -veins were formed. I am aware that many diffi- 
culties will have to bo surmounted before the above theory can 
take the position of an universally accepted explanation ; but. in 
the meantime it claims to be a good working hypothesis, founded 
on well-digested information, and likely at no distant date to rank 
— subject to a few modifications — among the established deductions 
of science. 
With regard to the occurrence in alluvial deposits of nuggets or 
masses of gold, far exceeding iu sizo any found in the quartz-reefs 
themselves, and the consequent difficulty of reconciling this cir- 
cumstance with the belief that all alluvial gold has resulted from 
the degradation of quartz reefs, it may be observed that many of 
the large nuggets found in alluvial deposits have been intimately 
mixed with vein-quartz in such a manner as to leave no room for 
doubt as to the latter having formed portion of the original matrix. 
Some nuggets have been found on which distinct impressions of 
quartz crystals were visible, aud in nearly all large nuggets 
there is a certain “ honeycombed or “ragged” appearance in 
those portions that have not been smoothed externally by 
attrition. 
I do not lose sight of the hypothesis formed by Mr. Selwyn, that 
pieces of gold disintegrated from quartz reefs may have been 
.subsequently added to in the drifts by deposit of gold from solu- 
tion by meteoric waters. This was supported by the experiments 
of Sir It. Daintree and Mr. C. S. Wilkinson, who proved that the 
presence of organic matter or pyrites caused the deposit of metallic 
gold from solution. It has also been urged in support of this 
belief, that the largest nuggets were found where volcanic erup- 
tions, as at Ballarat, had favoured the development of highly 
mineralized waters, aud that in parts of Gippsland aud other 
places where there has been no volcanic activity, pieces of gold 
above a few ounces in weight are rare. 
