Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/152

 a little yellow copper ore, accompanied by quartz, chlorite and iron pyrites to a considerable depth. Both the tin and copper veins have been traced for about a mile in length.

The two slides which run parallel with the metalliferous veins afforded no trace of either copper or tin. The northernmost of the two is from 4 to 12 inches wide; the southernmost from 2 to 3 inches. They were found to consist wholly of an argillaceous 3 clay, called by the miner flucan. These veins, as will hereafters seen, notwithstanding their poverty, were one principal cause of the remarkable incidents attending this mine.

It will be seen by the ground plan that the eastern cross course x, (which was about 4 feet wide, consisting of 3$$\scriptstyle \frac 12$$ feet of quartz on the western side, and 6 inches of flucan on the eastern,) traversed the channel of porphyry, the tin and copper veins, as well as the two slides, heaving them all 54 fathoms to the north on its western side, where they maintain the same distance from one another as on the eastern side. The cross vein y next on the west, which consisted of the same substances as the cross vein x, and on the surface where it cut the tin vein at P was distant from it only about 26 fathoms, had precisely the same effect on all the east and west veins, except that the distance of the heave north was only 18 fathoms, so that the tin vein, at its place of contact with the west side of the cross vein y at P was exactly 72 fathoms north of that part of it in contact with the eastern side of the cross vein x at Q. Of the cross vein at the western extremity of the mine, (as has before been noticed) little is known. But the two former have been traced nearly five miles in length intersecting every tin and copper vein, and from every observation, it seems probable that they extend from the Bristol to St. George's Channel, and are very distinctly seen in the digs near Porthtowan on the northern coast.