456 



THE GEOLOGIST. 



portion of the actual vein, and wliy does its decomposition so speedily 

 commence when removed from its primal condition ? Is not the cause 

 evidently to be found in the fact, that the vital forces of the vein are still 

 m operation, and that they possess the power of resisting decay ? Above 

 the water-level we find this decomposing action pervading the entire scope of the 

 vein ; below that point the oxidation has not progressed. The water evidently 

 claims a preservative influence over the constituents of the vein. So long as the 

 ■"^ater procolates freely through the interstices of the vein, so long will a medium 

 exist through which and by which the electro-magnetic forces will act, and the 

 decomposition of the vein be held in abeyance. While those forces continue in 

 full activity, aided by the solvent and mechanical action of the water, the deposi- 

 tion will progress, and the vein continue to accumulate its mineral wealth. As the 

 vital principle of the plant or animal does not create any new material in the 

 growth of its subject,. but augments its quantity by the process of assimilation, so 

 the vital forces of the vein do not create the metal, but act by transposition of 

 metallic substances from the depths of the earth and the surrounding wall-rocks, 

 to the body of the vein. For the verity of this assertion we appeal to the 

 practical facts of the laboratory. Crosse has produced various metallic salts 

 by electric action. The deposition of metal by the electrotype process is too 

 familiar to all to require description ; and the labours of Fox and others, in the 

 direct application of electro-magnetic force upon mineral veins, should satisfy even 

 the most sceptical, by the clear, broad light of truth which surrounds them." 



The consideration of the fourth point is reserved by Mr. Leeds for a future number. 



The other articles on gold-mines and the distribution of that precious metal in this 

 number of the " IS^'ew York Mining Magazine," will be perused also with interest, 

 especially in regard t® the question of the extension downwards into the solid rock 

 of the gold-bearing veins ; practical facts seeming to prove that, at any rate in 

 some instances, the vein continues actually as rich, or richer even, in gold in its 

 downward progress ; but that the rock not having undergone the decomposition 

 usually attendant on its upper portion, the metal is not so visible or so easy of 

 extraction. 



In the report of the Pascoe Gold-mines in Georgia by C. H. Shepard, for example, 

 we are told that the quartz- veins exhibit the usual phenomena of lodes, and that, 

 although gold occurs in places inclosed directly in the quartz, " it is nevertheless true 

 that its chief repository is in the pyrites," which occurs " not only in the joints of 

 the quartz- rock but is diffused through its entire substance. Sometimes its pro- 

 portion rises to one-quarter part of the veins ; and rarely it constitutes large 

 wedges and ovoidal masses in a state of almost absolute purity." The reader may 

 hnd some interesting and confirmatory remarks on the subject of the derivation 

 of gold from the pyrites, by i\Ir. Odernheimer, in the Geological Society's Journal, 

 vol. xi. p. 401. 



"There is no foundation whatever," Dr. Shepard adds, "for the opinion 

 that the quartz veins grow poorer in gold with their depth, at least in the 

 usual repositories where it is associated with pyrites. The contrary would rather 

 seem to be the fact, although it is undoubtedly true, that, as the shafts and 

 galleries penetrate deeper, and enter the region beyond the decomposing influence 

 of the atmosphere, the gold becomes more and more inaccessible to the old method 

 employed for obtaining it." We do not pretend to enter into the discussion on 

 this point, which is one, however, so important in its geologica,! bearings, that 

 the statements on both sides deserve careful consideration. 



