Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/440

330 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 9, apparently a number of branches entering the country (fig. 4). From this vein likewise the reef has not suffered 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 deceptive 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 granite- 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 company 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 rise through the granite up the eastern wall were, as already men-