652 C. LE NEVE EOSTEK ON THE GREAT FLAT LODE 



I have endeavoured to show in paragraph II. that the Great Flat 

 Lode is, in the main, a band of altered rock. Much of the veinstone 

 extracted from some of the largest Cornish mines, such as Dolcoath, 

 Cook's Kitchen, Tincroft, Cam Brea, and Phoenix, for instance, 

 closely resembles the contents of the Great Plat Lode, and was pro- 

 bably formed in a similar manner ; indeed I question very much 

 whether at least half the tin-ore of the county is not obtained from 

 tabular masses of stanniferous altered granite. If, then, many of 

 the most important lodes of such classic ground as Cornwall do not 

 satisfy the common definition, one of two things ought to be done : 

 either the miner should give up the term lode for these repositories, 

 or else the meaning attached to the word by geologists should be 

 extended. I need hardly say that the first alternative is not likely 

 to be adopted ; nor do I think it is one to be recommended ; for I 

 believe that one and the same fissure traversing killas and granite 

 may produce the two kinds of lodes. In the non-homogeneous 

 killas the fissure would be more or less jagged, and a shift of the 

 strata would produce open spaces ; whereas the same rent passing 

 through the underlying granite of uniform texture would be much 

 straighter, and a shift would cause much smaller openings. The 

 upper part of the lode, resulting from the filling up of the open 

 crack, would satisfy the ordinary definition ; whereas the lower part 

 would not, if it merely consisted of altered rock on the sides of the 

 narrow fissure. I should propose, therefore, that the term lode or 

 mineral vein should include not only the contents of fissures, but 

 also such tabular masses of metalliferous rock as those I have been 

 describing near Redruth and Camborne. If, however, this course 

 should be thought on the whole undesirable, the geologist and miner 

 must agree to differ in their language, and some of the lodes of the 

 latter will have to be designated as tabular stockworhs by men of 

 science. 



V. Statistics oe the Output oe Tin- ore from the 

 Great Flat Lode. 



I must now call attention to the value of the Great Flat Lode as 

 shown by the following figures : — 



Tinstuff. Clean tin-ore. 



Wheal Uny in 1876 produced 



South Cam Brea . . . 



"West Basset 



West Wheal Frances 

 South Condurrow . 

 Wheal Grenville . . . 



Totals 83,452 1846 



The six mines, Wheal Uny, South Cam Brea, West Basset, West 





tons. 



tons. 



duce 



d 17,702 



349 



?5 



2,040 



30 



It 



29,144 



618 



75 



6,652 



123 



J> 



19,414 



588 



" 



8,500 



138 



