76 AMERICAN ASSOCIATION FOR THE ABVANCEMENT OF SCIENCE. 



than attempt to maintain it by keeping these opposing conditions out of sight, or 

 by wilfully ignoring their yalue. Now, my object in the present brief communi- 

 cation, is simply to bring before the notice of the Section, certain facts, experi- 

 mental and otherwise, which appear to me to prove most incontestibly, that, in 

 nine cases out of ten, the so-called electro-chemical theory as explanatory of the 

 origin of native metals in veins, is entirely fallacious. 



We will take the case of native copper, under its known conditions of occur- 

 rence in the Lake Superior District and other parts of North America. The 

 electro-chemical theory is constantly being brought forward in explanation of thia 

 particular case. As the copper is here, normally, in intimate association with vast 

 masses of erupted trap, it might naturally be inferred that the presence of both 

 trap and copper was equally due to igneous action ;* or, where the copper occurs in 

 small strings and arborescent masses apart from the trap, to a modification of this 

 action, in volatilization and subsequent reduction of chloride of copper or some 

 other volatile compound. But the upholders of the electro-theory, find these views 

 apparently too simple for their approval. It is very possible that the copper may 

 have originated by some other agency ; but the following facts will, I think, shew 

 that this unknown agency was not the electro-chemical principle, whatever else it 

 may have been. The copper is very constantly found in the interior of zeolites or 

 calc-spar, or surrounding crystals of the latter substance in such a manner as to 

 shew that the calc-spar was solid before the solidification of copper — the copper 

 often presenting the most sharply-cut impressions, even to the minutest striae of 

 the crystals of the calcareous spar. I mention this well known condition of occur- 

 rence first, because it is commonly referred to as affording a strong proof of the 

 deposition of the copper according to the electro-chemical theory, although nothing 

 can really be more fatal to the reception of this hypothesis. 



The conditions of occurrence just alluded to, may, in the estimation of some, 

 disprove the igneous origin of the copper; but equally do these conditions dis- 

 prove its origin according to the other view. • In the first place, it must be remem- 

 bered that the zeolites, and carbonate of lime also, are non-conducting bodies ; and 

 hence that no deposition of metal can be made to take place upon them, by the 

 electro-chemical process, unless their surfaces be first coated with graphite or 

 Bome other conducting substance. This may be readily shown by the simple 

 method of ascertaining the conduetibility or non-conductibility of mineral bodies, 

 employed by Von-Kobell. The substance under examination is to be placed in a 

 solution of sulphate of copper, and touched by a slip of zinc, or a piece of zinc bent 

 into a kind of tongs may be used to hold the mineral. A deposition of metallic 

 copper will rapidly take place upon conducting bodies, such as pyrites, galena, 

 graphite, anthracite, (fee, <fee. ; but not upon non-conductors, as quartz, the feldspars, 

 garnet, calc-spar, malachite, and other similar minerals. 



This fact, when forced upon the attention of those who maintain the electro- 

 chemical theory, has been allowed to be " an objection ;" but that is not the pro- 

 per term. It is an insuperable obstacle — nothing less — to the legitimate adoption 



*In support of this view, see Agassiz, " Lake Superior ;" Dana, " Manual of Mineralogy ;" Na- 

 tive Copper ; Burat, " Geologie Appliqu^e ;" Fournet, and other observers. It should also be 

 remembered, in connection with this inquiry, that native copper occurs likewise in other truly 

 erupted trap rocks of different ages and localities ; as, for example, in Connecticut, New Jersey, 

 Nova Scotia, Rhenish Prussia, the Faroe Isles, Barrhead in Scotland, and elsewhere. E. J. C. 



