of Devonshire and Corn wall. 11 S 



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 con- 

 fined 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 

 numerous formations of this metal are of very different ages.* 



The ferriferous oxide of titanium belongs almost exclusively to 

 primitive countries. The locality of the menachanite proves never- 

 theless, that it may also be met with in secondary countries. The 

 naturalist, to whose accurate researches we are indebted for the dis- 

 covery of the menachanite, has also observed it in a kind of sono- 

 rous 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, 

 tantalium, columbium and cerium, Cornwall affords indications 

 of all the other known metals, in one shape or other, in mass, form- 

 ing deposits, or as adventitious substances in the veins, f 



* Galena in large cubes is found at Treseavan, with copper pyrites : at Poldice mixed 

 at the same time with cupreous and arsenieal pyrites in quartz and killas : and at Penrose 

 there is a rich rein of it which opens upon the surface. Klaproth's Miner. Obser. 

 p. 30. 



f Becher in his remarkable dedicatory epistle to the famous Boyle of his raineralogi- 

 cal alphabet which he wrote at Truro, says, The earth is here so abundant iu different 

 kinds of fossils that I believe there is no place in the world which excels Cornwall in the 

 quantity and variety of them. Klaproth's Miner. Obser. Introd. p. 3. 



