1814.1 Northumberland, Durham, &c. 343 



removal of the fluor spar is to be accounted for I cannot conceive. 

 The odIv substances present were fluorspar, quartz, and galena. 

 The change took place in the centre of a solid vein, a hundred 

 fathoms below the surface of the earth, surrounded on all sides by 

 walls of solid stone, and quite impervious both to air and moisture. 

 There cannot be the slightest doubt that the fluor spar once existed, 

 and filled up these cavities. By what agent has it been removed, 

 and what has become of it ? This problem is well worth the con- 

 sideration of geologists. It shows us that we are much farther horn 

 an accurate knowledge of the constituents of bodies than is gene- 

 rally believed, and that several of our elements are undoubtedly 

 compounds. It shows us also that changes are still going on m the 

 internal parts of the earth which are totally beyond our compre- 



'Traav mention another appearance equally unaccountable, which 

 I observed in some of the lead-mines on the banks ol the Weare, 

 The catena has lost its usual form, and has all the appearance of 

 having been recently in a state of fusion. Its surface has a glassy 

 lustre! its corners are rounded, and it is suspended like icicles in 

 the cavities of the vein. This change must have happened Ion- 

 after the formation and filling up of the vein, and long after every 

 thing had assumed nearly its present state. We know of no other 

 agent to which this fusion can be ascribed than electricity; and as 

 we know nothing respecting the limits of this agent, it is employed 

 without scruple by geologists to solve similar appearances. 



The lead-mines at present working in these counties cannot be 

 fewer than 100. The veins were first discovered in the beds ot the 

 rivers of the country, the Tync, the Nent, the Allen, the Weare, 

 and the Tees. Accordingly it is on the banks ot these rivers, and 

 hills between them, that most of the mines are situated ; but as 1 

 did not visit the mines on the banks of the Tees, 1 had no oppor- 

 tunity of acquiring much information respecting them. 



Besides the minerals already mentioned, there are several others 

 found in these veins. One of the most common is blende, the 

 never-failing companion of galena. The blende is always brown, 

 and it, quantity, at least in the veins which I examined is not 

 great But I was told of a vein of considerable thickness filled with 

 blende, lately discovered in the tract of country belonging to the 

 Greenwich Hospital j and I understand there is an jntentioi 

 raising this ore, and extracting zinc horn it. Calamine sometimes 

 occurs but it is scarce, except in one mine at Nent Head, wheie 

 I saw a considerable quantity of h, and understood that it was 

 occasionally collected and sold, Chalcedony occurs likewise in 

 Borne veins, not in any great quantity, accept: in two very 

 mines near Blanchland, called Ramshaw and bkueldon, 

 D ,in« ■ formerly ve.y rich, and were v. rough, for man/ years 



with great profit by the British Lead Mining Company. But alter 

 the veins had penetrated through the Great Lfme-stone into rad- 

 stone, they became very poor, and were in consequence neglected. 



