distinct. Where covered by the soil, the granite is generally found decayed or pulverulent on the surface, and in many places exhibits, under these circumstances, a stratified appearance. But this is only a superficial, and, I believe, an adventitious feature. The whole of this district, both in the granite and slaty parts, is traversed by an infinity of metalliferous veins. These, in general, run east and west. They vary extremely in their size and length, and also in the character of their contents. The principal metallic ores contained in them are tin and copper; but they contain many other metals, besides a great variety of other simple minerals. In some parts of the district these veins are much more plentiful and productive than in others, and are, consequently, much more worked.
The quantity of tin and copper annually raised in this district is immense. In 1822, the amount of tin exported from the hundred was calculated, by a most intelligent friend, there resident, at about 1,200 tons, valued at about £120,000. In the same year, the amount of copper exported from the district, was estimated at 40,000 tons of ore, containing about 3,000 tons of copper, and producing about £215,000.[1] This district is extremely rich in simple minerals, a list of which will be found in the Appendix to this paper.─(See Appendix, No. 1)
- ↑ In the year 1831, the total amount of tin raised in Great Britain, was 4,176 tons, the whole of which, with the exception of about 80 tons, from Devon, was raised in Cornwall. In the same year, the total copper raised in Great Britain was 14,465 tons; of this, 12,099 were raised in Cornwall, and sold for £835,912 One-third part, at least, of the tin and copper raised in Cornwall, is produced in the Hundred of Penwith.─Transactions of the Royal Geological Society of Cornwall, Vol. iv. p. 491.
