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Geology and Physical Geography: 
segregated in portions of the quartz reefs which have since been 
entirely removed, leaving their disintegrated gold to drop gradu- 
ally as the surface became lower by abrasion. 
Much has been said about the alleged prediction of Mr. Selwyn, 
and other geologists, to the effect that quartz reefs would cease 
to be auriferous below a depth of 400 feet. The general opinion 
which has been tortured so industriously into a dictum, was pub- 
lished many years ago when quartz mining, both in California 
and in Australia, was in its infancy, and this opinion was simply 
to the effect that, in the light of experience obtained in European 
and Asiatic gold mining, auriferous quartz lodes were more likely 
to decrease than to increase in richness as followed downwards, 
aud would probably become unremunerative within limited depths. 
Mr. Selwyn personally, however, maintained the view that such 
decrease would be inappreciable within the limits attainable by 
human skill. The opinion has happily proved correct; our sub- 
sequently acquired experience here shows that many of the lodes 
yield good returns from depths exceeding 1,000 feet, and, at 
Stawell and Sandhurst, rich yields have been obtained from double 
that depth, so that the question as to whether deep quartz mining 
will pay is practically answered in the affirmative as far as our 
more important quartz mining districts aro concerned. Mr. Selwyn 
did not fail to record his conviction that there was no reason to 
doubt but that quartz gold mining would prove as permanent a 
source of wealth here as tin or copper mining in England. In 
some places, however, quartz reefs, payably auriferous while in 
Silurian rock, have been followed down to subjacent granite, and 
have there been found to thin out and become unprofitable; so 
that there is evidence, at all events in some cases, of the grauite, 
at whatever depth it may be encountered, forming one limit to the 
successful downward prosecution of quartz mining. I here refer 
to granite as a mass or portion of the hypogene rock foundation, 
and not as a dyke or injected vein; in the latter form granite or 
some kindred rock may bo found to contain payably auriferous 
quartz-veins to indefinite depths while traversing Silurian rocks. 
Admitting that there is nothing to preclude the hope that many 
of our quartz mines may yield profitable returns from the utmost 
depths to which human skill can penetrate, the first portion of the 
opinion above referred to — as to probable decrease in richness of 
the lodes as followed down — has not so far been refuted by 
experience, though it is no doubt amenable to considerable modi- 
fication. The fact cau hardly be gainsaid — giving due credit for 
exceptional rich yields from great depths — that, on the average, 
richer quartz has been obtained from the surface portions of the 
reefs generally than has been met with in the deep levels, and 
though our lodes may be practically inexhaustible, thore is nothing 
to justify the expectation of an increased yield from them as 
followed downwards. 
