400 
MR. R. W. FOX ON THE ELECTRO-MAGNETIC PROPERTIES 
The accompanying sketches are intended to represent the plans adopted, 
and the results obtained in various mines, and under different circumstances. 
In some instances nearly 300 fathoms of copper wire were employed*. 
The intensity of the electro-magnetic action differed greatly in different 
places : — in some cases the deviation of the needle was inconsiderable, in others 
it went completely round the circle. In general it was greater, cseteris paribus, 
in proportion to the greater abundance of copper ore in the veins, and in some 
degree perhaps to the depth of the stations ; — and where there was little or no 
ore, there was little or no action. Hence it seems likely that electro-mag- 
netism may become useful to the practical miner in determining with some 
degree of probability at least, the relative quantity of ore in veins, and the 
directions in which it most abounds. 
When the distance of the plates from each other in a horizontal direction 
was only a few fathoms, and the copper ore between them was plentiful, and 
uninterrupted by non-conducting substances, or the workings in the mine, no 
action occurred, owing no doubt to the good conducting power of the vein ; 
but where a cross vein of quartz or clay happened to be between the plates 
under similar circumstances, the action was usually great. 
When the communication was established between two plates at different 
depths on the same vein, or between different veins, whether at the same level 
or otherwise, the electrical action was in general the most decisive. In fact, 
veins which in some instances were almost destitute of ore, and did not affect 
the needle per se, did so, though perhaps only in a slight degree, when elec- 
trical communications were made between them. 
It will be seen that 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, I think, from north to south, though 
in several instances it was the reverse. In veins having an underlie towards 
• I am indebted to the kindness of my brother, Lewis Fox, for the experiments referred to in 
Fig. 3, 13, & 22 ; to W. J. IIenwood for those in Fig. 8, 25, & 26, and to Richard Tregaskis 
for those represented in Fig. 16, 17, & 27. They moreover all assisted me materially on several 
occasions in making my experiments, especially my brother, who was my companion in most of my 
descents into the mines. To the various mine agents I am also under particular obligations, for their 
great attentions and personal assistance ; some of them having remained with us underground ten or 
eleven hours together. 
