Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/180

 168

Of the mines of copper and tin, there are four in each of the parishes of Redruth and Gwennap, three in St. Agnes, and two in St. Neot.

The two mines of lead marked in the above-mentioned map, occur in the parish of Sithney, in a situation which is nearly of the same elevation, as the lead mines of Beer-alston in Devonshire.

The mine of lead and silver is found in the parish of Wendron, and that of silver in the parish of Cubert.

The mine of copper and silver is in the parish of Gwinear; the antimony at St. Austle and Endellyon; copper and cobalt in Camborne; tin and cobalt in Madron; manganese near Launceston and the Indian Queen.

If we examine these localities it will appear, that the copper and tin which either singly or combined form four-fifths at least of the mines in Cornwall, are met with near the junction of the granite grauwacke: but it also appears, that tin may, contrary to the opinion of Werner, be sometimes found in secondary stratified mountains. It is true that at Kithill, and in the islands of Scilly, it is found in the true granite.

When the tin is not combined with copper, it usually forms a constituent part of the granite, and in this case it is often accompanied by wolfram in the matrix of the vein.