Mr. R. W. Fox's Remarks on Mineral Veins, Sfc. 19 



information extends ; and I believe the fact of some other me- 

 talHc ores being arranged at right angles to the former, is not 

 peculiar to Cornwall. 



In the latter district the E. and W. veins are usually inter- 

 sected and broken by the cross veins ; and instead of being 

 continued in straight lines, the parts are more or less widely 

 separated. And as the cross veins commonly consist of clay 

 or quartz, or of both together, the insulation seems almost 

 complete as it respects water and electricity. The clay being 

 found to dam up the water effectually even in the immediate 

 neighbourhood of deep excavations ; and the quartz, which is 

 an imperfect conductor of electricity, appears to me to be ren- 

 dered more effectually so by its radiated texture, — a forma- 

 tion which I believe is peculiar to quartz found in cross veins. 

 Sometimes the quartz is on one side of the clay, and in others 

 included in the middle of it. 



Nor must I omit to allude to veins of another kind (if they 

 may be so termed), which more easily approach an horizontal 

 position, and are usually in an E. and W. direction, and are 

 called "slides" by the miners, from their separating the veins 

 at different depths under the surface. These slides are also 

 mostly impervious to water. 



There seems, in fact, to be a remarkable analogy between 

 the arrangement of veins and some electrical combinations. 

 The high temperature of the earth varying as it seems to do 

 at different places, and the salts contained more or less in 

 water, tend to strengthen the resemblance. 



The arrangement of ores in the veins also affords evidence, 

 I think, in many ways, of the presence of electricity, either as 

 cause or effect. I may instance the regular disposition and 

 aggregation of different kinds of ores in the same veins, and 

 the frequent accumulation of metallic ores in parallel veins in 

 places at right angles to their direction*. 



The principal mining districts in Cornwall are usually near 

 the places of junction of granite and clay-slate. 



It has been observed that nearly parallel E. and W. veins 

 often become more productive when they unite either hori- 

 zontally or in depth, and the reverse frequently happens when 

 veins descending into the earth at oj)positc inclinations inter- 

 sect each other. 



Instances are occasionally, but very rarely, met with of E. 



• My friend R. Trcgaskis, of Perran, iicai- this place, who is well ac- 

 quainted with the practical part of milling, has remarked to nic, that vein:, 

 are imiallv found most iirocUutivc of ore near the inltrstction of cross, 

 veins, and J believe this observation to he well founded. 



D 'J and 



