336 ORIGIN AND DEVELOPMENT OF ORE-DEPOSITS. 



on a small scale with, tlie larger observed association of tin with 

 E.W. veins, and of iron and the rarer metals, such as uranium, 

 cobalt, nickel, &c. with N.S. veins, is obvious, and the causes are 

 probably similar if not identical in character. These electrical 

 experiments of Fox and others, though arising from Mr. Fox's 

 acquaintance with Ampere's hypothesis, have not shown any 

 particular connexion of the veins and rocks and their local 

 currents with Ampere's general currents ;* and Mr. Fox's first 

 idea, that the stratification of rocks, &c., were connected with or 

 due to such general currents was soon given up by him, as well 

 as by others. Although he was able to produce schistosity in 

 well-kneaded clay by electrical means, yet except perhaps for 

 such local phenomena as the sheeting already mentioned and the 

 local laminations of clays, we must look to mechanical causes for 

 large scale stratification, lamination, and schistosity. And further, 

 although given such longitudinal structure, and its accompanying 

 longitudinal jointing, electricity might convert some of these 

 joints into lodes, yet the proof of an absolute fissure in a great 

 majority of cases was soon admitted by him. 



Another of Mr. Fox's anticipations has also not been realized 

 up to the present. He hoped to discover great bodies of 

 ore by means of their electrical indications ; but although the 

 existence of masses of magnetic iron-ore has been ascertained in 

 Sweden, Canada, and the United States, by the somewhat 

 analagous use of his dipping needle, I believe no such practical 

 applications have hitherto been made of the galvanometer, 

 and bearing in mind the difficulties of the problem, it is hard to 

 have hope of ultimate success in this direction. 



* It may, however, be remarked that Mr. Henwood's experiments, and his 

 conclusions recorded in 1843 {Trans. R.G.S.O.,v.) in no way negative the existence 

 of such general currents, it is merely that the far stronger currents were not 

 eliminated To detect general currents in the neighbourhood of metalliferous 

 deposits must be as difficult as to ascertain the directive effect of the earth on a 

 magnet in the immediate neighbourhood of masses of magnetite. It may 

 perhaps be granted that the influence of general currents in forming valuable 

 metalliferous deposits is small, perhaps even insignificant except as a start, and 

 this, I believe, was pretty much Mr. Fox's final conclusion. A similar difficulty 

 exists in determining the normal increase of subterranean temperature, since 

 hitherto all observations have been made in places where abnormal conditions 

 exist ; yet few will doubt that there is such a normal increase. 



