Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/438

328 PROCEEDINGS OF THE GEOLOGICAL SOCIETY, [June 9, an extremely uneven face, ramifying very frequently into the country and the horse (fig. 1). With regard to its auriferous contents, the eastern vein stands far behind the western in richness: although the yields of gold from certain parts have been very fair, still, on the average, they were low, and the character of the vein became irregular in depth; whilst the western vein contained the gold more richly and evenly distributed, and showed a more regular course on being followed downward. It was rarely less than 3 feet, but increased in places to 20 feet and more in width (Crystal's Claim).

Next southward of the Alliance Company, in the ground worked by the Speculation Company, a great alteration is apparent in the character of the horse separating the two veins. It becomes, from the surface downward, gradually more thickly traversed by quartz-strings, which are mostly auriferous, and at about 200 feet in depth it represents in reality a close irregular network of quartz and metamorphic sandstone. One of these strings, near the centre of the "horse," increases to several feet in thickness, becomes well defined in dip and strike, and, being also more auriferous than the rest, is advantageously worked and called the "middle vein." The eastern vein is in this ground not visible on the surface, and was for several years, in fact, not supposed to exist, till, through some workings, to be mentioned further on, and certain features in the neighbouring ground of the Alliance Company, it became clear that the horse expands towards the surface to such a degree as to squeeze the vein to (what the miners term) a "feather-edge," and to make it quite disappear at the surface. On piercing the horse, however, at a lower level by a cross cut, it was soon discovered, and produced some very rich quartz for a certain extent in length and depth, but gradually became poor afterwards. At 240 feet from the surface the western vein showed in this mine the peculiar feature of becoming nearly flat for a distance in strike of about 100 feet, and in dip nearly 40 feet, and then assuming its normal course again (fig. 2). The thickness of the vein at this place is 3-5 feet, and the quartz yielded on an average nearly two ounces of gold per ton.

Proceeding again southward of the Speculation Company's mine, the reef shows a further change. The eastern vein, hitherto less important than the western one, continues profitably auriferous for a considerable extent in strike, and, ultimately disappearing at the surface, still exists in depth, always distinguished by its fine smooth eastern wall; the western vein, on the contrary, soon dies out both in depth and strike.

Having thus given a short sketch of the reef with regard to its development in the principal mines opened upon it, I will now describe some peculiarities observed in the Alliance Company's mine, in connexion with the interesting feature of the intersection of the reef by different granite-veins. The relative positions of these with reference to the company's engine-shaft are as follows:—

The first vein traverses the reef diagonally, entering it close south of the shaft, and running northward through it for a distance