Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/163

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153
Mr. William Phillips on the Veins of Cornwall.

found to traverse a mass of it at about 73 fathoms from the surface, above and beneath which schist only was observed.

The veins of this mine are worthy of attention in regard to their number, underlie, dimensions, and contents. In number they are seven; the other two may rather be called off-sets from a vein than veins. If however they be considered as veins, there are in this mine five of copper, three of tin, and one of tin and copper, in about a furlong and half of country from north to south. The general irregularities of their underlie, both individual and regarding each other, are very remarkable: only the Old Tin vein and Bodilly's vein proceed in a straight line, and it will be noticed that the New Tin vein proceeds in five directions, the second more inclining to the perpendicular than the first, the third more than the second, and so on. The South vein varies in width from one to six feet, and was rich in copper from about 35 fathoms until about 70 fathoms from the surface; that is, through the lower part of the upper deposition of granite, and the subjacent schist; but at about the place where it entered the granite again it was hard and poor. It was pursued for about 100 fathoms in depth. The ore was a mixture of yellow and grey, and like that of every other vein in the mine, was so extremely bunchy, that a regular course of ore, as it is technically termed, could scarcely be said to have existed in any part of it. Dunkin's vein varied from one to twelve feet in width, and its general underlie differed so little from the perpendicular, that advantage was taken of that circumstance to sink the shaft on its course. It was poor at the points of junction with Martin's and Bodilly's veins, but some ore was found in it between them. It was richer below the latter, and was worked to the depth of about 125 fathoms from the surface. Martin's vein was from about 3 to 6 feet wide, and yielded abun-

Vol. II.U