'S^'-yK^ in Metalliferous Veins. ' 269 



iiimiersed in rain-water for more than a fortnight, and then 

 compared, may be classed in the following order : 



-r Zinc, + Sulphuret of Silver, 

 Copper, Copper-Pyrites,* 



Copper Nickel, Iron-Pyrites,* 



Vitreous Copper, Ai-senical Pyrites,* 



Purple Copper, Loadstone, 



Galena, Peroxide of Manganese. 



My experiments in mines appeared to indicate a general 

 tendency in the electric ciurents to take a westerly du'ection, 

 in veins incUning or dipping towards the north, and an east- 

 erly one, in those dipping towards the south ;i whilst down- 

 ward currents were mostly obtained where masses of ore at 

 different depths were connected. It is true that such results 

 were not without exceptions ; and W. J. Kenwood's researches 

 in mines, as well as those of Professor Reich, would seem to 

 render it premature, at least, to form any general conclusions 

 on the subject. Local causes may, however, often supersede 

 those of a more general character ; thus, for example, if a mass 

 of copper-pyrites, or iron-pyrites, were connected with ano- 

 ther of vitreous copper, or galena, the currents Avould probably 

 pass through the apparatus towards the latter, especially if 

 not very distant from the former ; and even differences in ores 

 of the same name may more or less influence the directions of 

 the currents where small insulated portions of ore are con- 

 nected, whereas, where the masses of ore are large and far 

 asunder, the more general law, if such there be, may predomi- 

 nate. 



This point will not probably be decided without more ex- 

 tended researches ui different mining districts ; and these, it 

 may be hoped, will be undertaken, not for this reason only, 

 but also for the purpose of determining whether the electro- 



* These tliroe * * * difier very little from each other, or from platina or 

 palladium, in their electrical relations, and they often change places, espe- 

 cially iron and arsenical pyrites. 



t It may be remarked, that, in this latitude, veins, having an inclination 

 towards the south of 40° from the vortical, are parallel to the axis of the 

 e.irtii ; and thoy are nearly peii)cndicular to it, when they have the same de- 

 gWe of incliuHtion towards the south. It is true tliat veins have seldom so 

 great an iuclination as this in Cornwall, but very commonly as much as 30'. 



VOL. xxviii. NO. I.VI. — Ai'Rir. 1H40. t 



