1 3S ElectrO'Tnagnetic properties in the mines of Cornivall. 



power of the vein ; but where a cross vein of quartz or clay hap- 

 pened to be between the plates under similar circumstances, the ac- 

 tion was unusually great. 



When the communication w^as established between two plates at 

 different depths on the same vein, or between different veins, V\7hether 

 at the same level or otherwise, the electrical action was in general 

 the most decisive. In fact, veins, which in some instances were al-- 

 most destitute of ore, and did not affect the needle, per se, did so, 

 though perhaps in a shght degree, v^hen electrical communications 

 were made between them. 



The direction of the positive electricity was in some cases from 

 east to west, and in others from west to east ; and when parallel 

 veins were compared, its general tendency was, the author thinks, 

 from north ta south, though in several instances it was the reverse. 

 In veins having an underlie towards the north, the east was commonly 

 positive with respect to the west ; but in veins dipping towards the 

 south, the contrary was observed, with one exception only, and that 

 under rather unusual circumstances. In comparing the relative 

 states of veins at different depths, the lower stations appeared to be 

 negative to the upper ; but exceptions sometimes occurred when a 

 cross vein of quartz or clay intervened between the plates, and the 

 higher one was on the negative side with respect to the horizontal 

 currents. 



In such cases it may be supposed that there is an accumulation of 

 electricity in different states, on the opposite sides of the non-con- 

 ducting vein. Such intersections of ore veins, and their being often 

 very rich to a great depth in one direction and not in another, added 

 to their varying underlie at different depths, which is not unfre-^ 

 quently reversed, may tend to produce apparent anomalies in exper- 

 iments of this nature. 



At Huel Jewel mine, the author obtained results between a heap 

 of copper ore at the surface, and a plate fixed at different depths 

 against the ore in the vein ; the latter becoming negative, in propor- 

 tion to the depth at which it was placed. Piles of copper ore at 

 the surface did not act on the needle when tried together, independ- 

 ently of veins, nor was it to be anticipated that they would. 



It is not improbable that the progressive increase of negative elec- 

 tricity observed in descending into mines, if hereafter confirmed, 

 may be found to be connected with the progressive increase of tem- 

 perature. The author has not discovered any distinct connection 



