1822.] On a Section of the Strata, 8^t. 22a- 



The tin of Cornwall and Devon was reduced in quantity about 

 this period by a great depression in price, but it may be esti- 

 mated at 



3000 tons block and grain at ^70. 210000 



The total value of these metals of the kingdom may, therefore, 

 be stated to be : 



^ .s d. 



Copper 974736 



Lead 733736 



Tin 210000 



1918472 



To this ought to be added the value of silver, manganese, 

 antimony, cobalt, zinc, but of which no probable estimate caa 

 be made. 



So that the real proportion of the mineral treasures of the king- 

 dom of this sort to be assigned to the district which Mr. Forster 

 treats of, is about one-seventh of the whole. 



Now as to its equalling or excelhng in productiveness any part, 

 yet discovered in the world, we might mention the value of pro-, 

 ducts of each of the three principal mining districts of Mexico, 

 where we are told by Humboldt, that one mine only called Valen-; 

 ciana, yielded from the year 1771 to the time at which he was 

 writing the annual amount of 600,000/. 



But not to leave our own country, it will be seen in Mr. Tho- 

 mas's short account of the mines, appended to his excellent map 

 of the principal, mining district in Cornwall, and which takes ia 

 only about 26 square miles, that the mines in that space produced 

 in 1818, 55,920 tons of copper ore, which being reduced into 

 copper at a medium rate of produce, and then valued, would 

 amount to 516,656/. to which he mentions, in addition for tin, 

 41,880/. (valued in ore only, and this district not including the 

 principal mines of this metal), and we have 558,536/. or just 

 double the produce of all the Cumberland and Durham mines* 

 and raised in a much smaller space. 



In the compass of Mr. Thomas's survey are mentioned (table,. 

 p. 74) two mines, Dolcoath, and the United Mines, as producing 

 the one 850, and the other 950 tons of copper ore per month ^ 

 these together would make 1780 tons of fine copper in the year,, 

 worth near 200,000/. We do not know what the produce o£. 

 that extraordinary spot in Anglesea, the Paris mine, at its best, 

 time, may have amounted to, but we conceive that if the copper 

 then raised in a year was valued at present prices, which are not 

 high ones, the money would be as much as that of a year's lead, 

 of Cumberland, &c. 



In comparing individual mines with other lead mines, Mr, 

 Forster unfortunately gives us but few dat^i; he meutious, p, 274*. 



