235 



The best conductor among the natural sulphides appeared to be mispickel, 

 which vies in this respect with some of the metals. 



As to the intensity of the electro-motive or electrolytic power which some 

 of these sulphides ai-e capable of developing, in contact with the exciting 

 solutions instanced, I should think it to be little, if anything, inferior to that 

 of zinc in like solutions ; and, while this development would be slower, the 

 absolute quantity of electricity producible should be much greater, weight for 

 weight, as compared with that yielded by zinc, under similar conditions, 

 if, as appears very probable, the oxydation of their sulphur also developes 

 electricity. If such development is in proportion to the quantity of oxygen 

 requisite to oxydize the sulphur to sul^ihuric acid, the electro-motive power of 

 common iron pyrites as compared to that of zinc qtiantitatively would be 

 abovit as four to one, since pyrites requires its own weight of oxygen to oxy- 

 dize both its constituents to oxides permanent under ordinary conditions, while 

 zinc barely uses one quarter of its weight for the same purpose. 



"Whether or not, however, the sulphur of these various sulphides participates 

 to any extent in the production of the electrotypic deposit referred to, the know- 

 ledge that such kind of metallic depositions ai-e possible in a natural way, 

 is exceedingly suggestive in regard to the manner in which some metals 

 have assumed the metallic form. 



These results, taken in connection with the abundance of metallic sulphides 

 in many of our mineral veins and rocks, make it appear very probable that 

 much of our native gold, silver, and platinum, have been electro-deposited 

 from saline solutions by voltaic action set up by the contact of dissimilar 

 sulphides, or sulphides with more negative substances, such as hematite, 

 magnetite, or ferruginous rocks. 



Besides the bearing these results would seem to have in relation to the 

 manner in which metals have been deposited, they tend, I think, to throw 

 a light upon the mode in which those currents of electricity are produced and 

 kept up in the crust of the earth, traces of which were discovered by Mr. 

 Fox, about forty years ago, and afterwards by others, includiug Professor 

 Reich, in verification of the correctness of Mr. Fox's assertions. 



This discovery of Mr. Fox's, has such an intimate connection with the 

 subject of this paper, that it is a matter of regret that I cannot refer to 

 the particular volume of the Transactions of the Royal Society in which it 

 was announced ; but from what I gather from the works of those authors 

 who have quoted from this paper, the most important points established by 

 Mr. Fox were, — that these currents varied in intensity, also in direction, 

 running east to west and west to east, and when stations at different depths 

 were connected, the current was generally downward; the whole of his 

 experiments being, I think, carried on in mineral veins. 



It will be immediately seen how well this agrees with what we should 



