Observations on a remarkable Deposit of Tin-Ore. 69 



At about 105 fathoms deep this lode is connected with one of 

 those curious deposits of tin-ore locally called (i Carbonas,"* as yet 

 unknown in any other part of Cornwall. The union takes place 

 about 14 fathoms south of the contact between the Wheal Comfort 

 and the Wheal Laity lodes; and for 10 fathoms above and 20 

 fathoms below, as well as for the whole distance between the Wlieal 

 Laity lodes and the Carbona, the Wheal Comfort lode, when alone, 

 is very productive : but immediately as the Wheal Comfort lode 

 and the " Carbona" separate in descending, — each taking its own 

 downward course, — the lode becomes unproductive, and so also re- 

 mains as far southward as it has yet been traced. 



At the northern contact of the Wheal Comfort lode and the Car- 

 bona Ji there is a rich mass of quartz, felspar, schorl, and tin-ore, at 

 least 15 feet in width for about 5 fathoms in length: both south- 

 ward of and below this spot the lode preserves its usual direction 

 and dip; but the " Carbona'" southward bears about 5° east of the 

 course of the lode, and holds nearly perpendicularly downward. 

 Descending about 5 fathoms, it abuts on the granite rock, and is 

 seen no deeper ; except that as it is pursued southward the irregular 

 granitic bed on which it rests declines at an angle of about 8°. 

 With the exception of a single short string or pipe no trace whatever 

 of the " Carbona" has rewarded the numerous researches which 

 have been made at greater depths. Nothing can, however, be more 

 irregular than its size and various ramifications. Though the upper 

 edge of the " Carbona" generally continues to touch the lower side 

 {foot- wall) of the lode, in some places the contact is only a few 

 inches, but in others as much as two fathoms and a half wide. 

 Again, in some cases the continuity of the " Carbona" where it 

 joins the lode, is almost entirely cut off by intervening masses of 

 granite ; the union with the main body being still preserved, though 

 merely by " pipes" or " pillars'' of lode-like matter. Many portions 

 of the " Carbona" are as much as five or six fathoms high ; others 

 not more than four or five feet ; some parts are two fathoms and a 

 half wide ; whilst others do not exceed six inches. The largest 

 portions are, however, seldom or never entirely separated from each 

 other by the containing rock ; for there is always a sufficient connec- 

 tion to conduct tj^e miner from one large and rich mass to another. 



The composition of the Wheal Comfort lode has been already 

 noticed : but, notwithstanding their intimate connection, that of the 

 " Carbona" is widely different, as its tin- ore occurs chiefly in 

 quartz and schorl, which minerals, either separate or mixed, consti- 

 tute the far greater portion of this remarkable deposit. 



* Some persons pretend to derive this term from the ancient Cornish lan- 

 guage, whilst others suppose it to have heen recently coined hy the miners. 

 Both the word itself and the metalliferous deposit it is meant to designate are, I 

 believe, confined to the St Ives mining district. Corn. Geo. Trans., v., p. 21, 

 note. 



