ORIGIN AND DEVELOPMENT OF ORE-DEPOSITS. 145 



Early workings on the various lodes, ") ^.^nn nnn 

 estimated at j i.500,000 



Produce of first great working previous to ) 



letting in the water in 1778, estimated | £2,000,000 

 by Capt. Chas. Thomas . . . ) 



Produce from re-opening in 1800 to 1870 » „. 



according to Capt. Josiah Thomas . . J ^^'^""."^^ 



Produce 1870 to 1890, estimated at . . £2,000,000 



£10,000,000 

 Of course this 10 millions has not all come from the great 

 lode, — a considerable portion was yielded by the caunter lode, 

 Harriett's lode, and others ; but if we allow the liberal amount 

 of two millions for these there still remain 8 millions as the 

 produce of a length of 550 fathoms on the main lode, — with 

 perhaps an average depth of 350 fathoms, — or say £40 per square 

 fathom of lode (one fathom in height and length and the width 

 of the lode). 



The lode however has been worked on more or less for a 

 total length of at least 1800 fathoms, and, excluding the 550 

 fathoms in Dolcoath, to an average depth of perhaps 250 fathoms • 

 we have therefore about 312,500 square fathoms of lode worked 

 or explored in the other mines for which we can hardly assume 

 the produce in tin and copper at a less value than 5 millions 

 sterling, giving for the whole lode to the present average depth 

 of less than 300 fathoms, a produce of 13 millions sterling, or 

 over £25 per square fathom of lode.* 



The average width of the lode is certainly much greater 

 than the average of the lodes of tin and copper in the West of 

 England as given by Mr. Henwood. Prom the 66 to the 197 in 

 Dolcoath it was about 6 feet, but narrowing in places to 1 foot 

 and widening in others to 16 feet. At the present bottom of the 

 mine it varies between 2 to 4 fathoms, with perhaps 16 feet for 

 an average ; the tinny portions being mostly wider than those 

 containing only copper as already stated. In Cook's Kitchen, 

 Tincroft, and Cam Brea mines the present average is somewhat 



*0f this large amount perhaps about 4 millions have been yielded by copper 

 ores and 9 millions by tin ores, equal to 570,000 tons of copper ores at ^67, and 

 170,000 tons of black tin at .£53, which are pretty near the average prices 

 realized. 



