mentioned, I cannot say. Manganese as well as antimony occurs in primitive and in secondary mountains, and the different formations of it appear to belong to a middle age.
The lead formation is of very small extent in Cornwall, it is confined to the low parts of the county. This metal is known to occur particularly in calcareous countries, rarely in primitive rocks; it is one of those metals most universally spread over the surface of the globe, especially in the state of galena. Werner conceives that the munerous formations of this metal are of very different ages.[1]
The ferriferous oxide of titanium belongs almost exclusively to primitive countries. The locality of the menachanite proves nevertheless, that it may also be met with in secondary countries. The naturalist, to whose accurate researches we are indebted for the discovery of the menachanite, has also observed it in a kind of sonorous petrosilex, which I consider as the clinkstone of Werner, and which had been picked up in the neighbourhood of south Brentor in Devonshire, where it is found in blocks on the surface of the fields. We know in fact, that the oxide of titanium exists in a great number of rocks, even in granite.
With the exception of platina, mercury, molybdena, tellurium, tantalum, columbium and cerium, Cornwall affords indications of all the other known metals, in one shape or other, in mass, forming deposits, or as adventitious substances in the veins.[2]
- ↑ Galena in large cubes is found at Treseavan, with copper pyrites: at Poldice mixed at the same time with cupreous and arsenical pyrites in quartz and killas: and at Penrose there is a rich vein of it which opens upon the surface, Klaproth's Miner. Obsr. p. 30.
- ↑ Becker in his remarkable dedicatory epistle to the famous Boyle of his mineralogical alphabet which he wrote at Truro, says, The earth is here so abundant in different kinds of fossils that I believe there is no place in the world which excels Cornwall in the quantity and variety of than. Klaproth's Miner. Obser. Introd. p.3.
