192 DESCRIPTION OF THE OPERATIONS AT DOLCOATH MINE. 



paper furnished to the excursionists, it will not be necessary to 

 add much on those points. I may remark, however, that although 

 all the lodes which have been extensively worked have produced 

 large quantities of co'p'per ore, yet only the main lode and those 

 lodes to the south immediately connected with it, and which fall 

 into it, have been rich for tin. The other lodes which are smaller, 

 or not connected with the main lode, have nowhere, so far as 

 explored, produced tin enough to be profitably worked. 



It would probably be difficult to find a richer piece of mining 

 ground than this. The sett, which is about 550 fathoms in length, 

 has already produced copper and tin ores to the value of five and 

 half millions sterling; being about £5000 for every yard, or nearly 

 £140 for every inch in length. The mine too is still in a prosper- 

 ous condition, and bids fair to continue so for many years to come. 

 I believe at the present time we are working to a greater depth, 



second to those of the Consolidated mines only. After a while the deepest 

 works began to give gradually diminishing returns of copper ore ; and 

 notwithstanding the appearance of tin-ore in them, they were at length 

 suspended. After a considerable interval, the superintendency devolved on 

 the late manager, who resumed operations at greater depths, and brought them 

 to a successful issue. Dolcoath having been formerly the richest copper 

 mine, is now the most productive tin mine in Cornwall. It may not be 

 unworthy of remark that the upper part of this deeply-seated tin-ore, like 

 the shallower portions of the copper dejjosit above it, afforded an abundance 

 of crystallized mineral. Ores of cobalt and bismuth have been obtained in 

 small qi;antities from the ^^rincipal southern and central lodes ; whilst in the 

 northern part of the mine Entral south lode has afforded a large amount of 

 silver. 



But the lodes as well as the rocks are traversed by another system of 

 veins (the cross-veins). These usually range from N. to S., to perhaps .SO 

 degs. S. of E., N. of W. ; and dip, whether E. orW., at a considerably higher 

 angle than the lodes or the elvans. With the exception of the cross-course 

 which divides Dolcoath from Cook's-kitchen, they measure from less than an 

 inch to about three feet, and average, say one foot and a half in width. 

 Their principal ingredients are quartz and clay ; but on passing from one 

 rock to another their mineral character — like that of the lodes — undergoes a 

 change, and they assume a certain resemblance to the rock adjoining. 



Where two lodes of different series interfere, the one of them which 

 intersects at one level is, sometimes, itself intersected at another. 



The lodes interfere with numerous cross-veins, which produce simple 

 intersections in some, but displacements (heaves) in other places. Such, 

 however, we have not opportunity to describe here. 



The works of Dolcoath are about 550 fms. in length, 

 by 150 ,, in breadth. 



In 1758 they were some 88 ,, in depth, 



„ 1788 „ „ 183 „ 



„ 1824 „ „ 240 „ 



And now they are 340 ,, ,, 



