File:The Quarterly journal of the Geological Society of London (12961349113).jpg

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PEOCEEDIN'GS OF THE GEOLOGICAL SOCIETY.
.June 9,
apparently a number of branches entering the country (fig*. 4). From
this vein likewise the reef has not suflfered any displacement or
change. On being sunk through, the granite was observed to have,
Fig. 4. — Section of Reef, showing second Granite-vein.
in a line with the smooth eastern wall of the reef, a distinct joint
or crack, filled with black clayey matter. This feature was so de-
ceptive that the miners believed the vein really terminated right at
the eastern wall ; and as a similar joint, though not so marked, was
observed on the western wall also, the belief generally gained
ground, and it was at last positively asserted, that this second gra-
nite-vein did not penetrate into the country, but formed, so to
speak, an intrinsic portion of the reef. However, through a late
break in the mine, causing a great portion of the reef and country
to cave in at the surface, the fallacy of this assertion is clearly
proved, since the branches into which the vein divides can plainly
be seen entering the country. The sinking through this granite
vein, in the Speculation Company's ground, led principally to the
proper understanding of the nature of the previously mentioned
" horse," and, in consequence, to the discovery of the easterly vein
of the reef. Not knowing that the "horse" expands, and thus
causes the easterly vein to disappear towards the surface, the com-
pany worked down the westerly vein and penetrated through the
granite. But on finding the reef beneath of a far greater width,
save a thin parting of metamorphic sandstone in the centre, and
also striking the smooth eastern wall, that had not been observed
above the granite, it was at once rightly supposed that what had
been thus far considered the country was in reality the " horse,"
which suddenly contracted beneath the granite vein, thereby causing
the eastern and western quartz-veins to join. A cross cut and a