ORIGIN AND DEVELOPMENT OF ORE-DEPOSITS. 335 



changes, without being in somewhat different electrical states. 

 This being so, there must be constantly in action direct currents 

 from one to the other, across the run of their junctions. Some 

 of the effects of such transverse continuous currents are illus- 

 trated by Mr. Fox's experiment with the clay enclosed between 

 metal plates already alluded to. Does not this mode of viewing 

 the subject explain in some degree the frequent occurrence of rich 

 parts in or near contact zones, and the reasonableness of the miner's 

 universal belief in the beneficial effect of a juxtaposition of dis- 

 similar rocks in a mining district ? It is in fact the great constantly 

 acting deposition battery. Of course it cannot make metallifer- 

 ous deposits if the region contains no soluble metal, any more 

 than the battery of the electro-plates can go on depositing after 

 its solutions are exhausted ; but given suitable solutions, and 

 every mineralized region supplies such ; suitable places for 

 deposit, and these we get in disturbed and fissured country ; and 

 a sufficient battery, which is supplied by the juxtaposition of 

 dissimilar rocks ; and we have all the favourable elements for the 

 formation of rich parts. It seems to me that, from the electrical 

 point of view more than any other, it may be possible to study 

 the mutual relations of ore deposits and country rock with 

 advantage. 



An interesting illustration of what is apparently the directive 

 force of electricity is afforded by another phenomenon. It is a 

 matter of the commonest observation that certain minerals are 

 often deposited in joints of definite direction, and not in others 

 having different directions, or on certain planes of a crystal in a 

 vein, and not on other planes differently oriented. Thus, at the 

 Treskerby Quarry, in so-called "primary granite," schorl and 

 chlorite are deposited in E.W. joints, but not in those running 

 N.S.*' Similarly at Carn Marth, joints running 25°S of W. have 

 amethyst, fluor, and chlorite, while those running 10° W. of N. 

 carry schorl and oxide of iron ; and in the Trelubbus Quarry 

 joints 20° S. of W. have chlorite, chalcopyrite, mispickel, and 

 blende, while the approximate N.S. joints contain schorl and oxide 

 of iron as at Carn Marth. f The parallelism of such phenomena 



* Notes of Excursions, Rev. M.it.,1864. 

 t Ibid. 



