160 PROCEEDINGS OF SECTION B. 



I shall now pass on to a consideration of the objections that 

 may be raised to my theory, that the metallic sulphides are 

 commonly the reducers of our native gold. 



Mr. Newbery remarks that were this theory correct, we should 

 have gilded pyrites occurring naturally, whereas this is not the 

 case. 



Salts of gold are not the only oxidizers of our sulphides, nor 

 must it be supposed that they have advanced to the attack 

 singlehanded. 



I conceive that the oxidizing agents which must necessarily 

 accompany gold salts, and that too in proportionately large 

 quantities, would eat into pyritous nuclei and thus undermine 

 most of the gold which had deposited thereon ; in fact isolate the 

 bulk of it as fine spangles, so that everything like a complete 

 coating or film of gold over any mass of sulphide would be 

 impossible. The fine particles thus released would, of course, be 

 out of electric circuit, and therefore subject to the solvent power 

 of the surrounding liqviid, and would thus be re-dissolved, 

 perchance to be re-deposited upon some piece of gold which, 

 having preserved contact, has remained nuclear as being the 

 negative element of a voltaic pair. 



Grains of gold might lodge upon the upper surface of the 

 sulphide, and by outside pressure, or by their own weight, keep 

 up electric contact, and thus form by accretion the coarser or 

 more nuggety gold which has to be accounted for. 



Again, pyrites is never equally exposed to the flow of aqueous 

 currents on all sides ; frequently but one side is exposed to the 

 action of the auriferous solution. 



There is another and still more serious objection to be en- 

 countered. It is held by many scientists that the gold and 

 metallic sulphides were deposited simultaneously, and if this 

 theory be correct, I know of no process of deposition that v,'ould 

 satisfy such a condition. 



There is one important consideration which should always be 

 kept in view before giving our adhesion to any theory. It is this — • 

 our native gold is always alloyed with silver, sometimes with 

 copper, bismuth and platinum ; allowing, however, that the three 

 latter require exceptional circumstances to favour their deposition 

 with gold, there still remains silver to be considered. 



Any theory then must be such that it will satisfactoi'ily explain 

 the constant association of silver with gold, or at any rate gold 

 derived from reefs. 



It might fairly be asked, is organic matter as competent, as 

 metallic sidphides, to precipitate and concentrate silver along with 

 gold ? I think it will be generally admitted that it is not. ^ 



As regards the metal copper in native gold, I own that my 

 theory cannot account for it. I have tried to get such a combi- 

 nation by means of metallic sulpliides, but have entirely failed as 

 yet. On the other hand, silver alloys are easily formed. 



