Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/182

 170 that have been found to accompany the veins are, arseniate of iron in the mines of Carrarack and Huel Gorland, oxide of uranium in the state of ochre, in Tin Croft mine; bismuth and nickel at Dolcoath, spathose iron at Cook's-Kitchen, and native silver united with decomposed galena in the mine of copper and silver at Herland. Judging of this formation of copper from its being accompanied by bismuth and uranium, we should be led to consider it as very old. Uranium and bismuth being found in this district proves, that those metals may, contrary to the opinion of Werner, be met with in secondary mountains. The nickel, cobalt, silver, and especially the spathose iron, would lead us on the contrary to refer that formation to a much more recent epoch, insomuch, that we must perhaps admit, that in the deposits of copper in Cornwall, there are veins of different ages.

It may be possible also, and this idea seems to me the most probable, that the accompanying substances which contradict the uniformity of age in veins of copper, are met with in rents formed at a later period, or in the veins called cross-courses, of a still more recent date. It is only however from practical miners, that we can hope to obtain information on this head.