ON GOLD : ITS FORMATION IN OUR REEFS. 157 



In tliese tliree experiments there was no discernil)le difference 

 in results to those obtained in experiment No. 1. 



So far, therefore, as is shown by tliese results gold reduced 

 from a solution of its chloride, by aid of such kinds of organic 

 matter as cork or wood, does not in the manner of its deposition 

 exhibit such a notable selective power for metallic gold as the 

 description of Mr. Daintree's results would lead us to suppose. 

 It does not, indeed, show any selective process at all, that is to a 

 greater extent than can be attributed to the action of surfaces 

 generally, regardless of their nature ; and in support of this, T 

 believe I am correct in stating that the whole sum of our 

 experiences (omitting those of Mr. Daintree) is directly against 

 this theory, as to the rapid and marked deposition of gold on gold 

 in the manner stated ; indeed, so far as I am aware, we only 

 produce by these means fine incoherent powder — minute crystals, 

 or films of exceeding thinness — nothing nuggety. We get a 

 certain size of grain or crystal, or a certain thickness of film, 

 ■which our eftbrts have hitherto failed to enlarge. 



The correctness of my results have been corroborated by Mr. 

 Cosmo Newbery. 



c. That it is organic matter in covjunction loith Tnetallic 

 sulphides. In 1868, Mr. C. S. Wilkinson, Government 

 Geologist of New South Wales, sought for other substances besides 

 gold that would attract to themselves gold as liberated from 

 soluble salts by organic matter. In this he appears to have been 

 very successful, for shortly afterwards he read a paper " On 

 the formation of Nuggets," in which he gave the results of his 

 experiments. He stated that in solutions of chloride of gold, 

 metallic sulphides were in a short time beautifully gilded. At 

 the same time he exhibited specimens of several sulphides to 

 illustrate this property of gold as liberated by organic matter. 



d. That it is metallic sulphides alone. I had found that the 

 metallic sulphides were very fair conductors of electricity, that 

 in fact tliey can be used in a voltaic circuit as the negative pole 

 with zinc. The kind of phenomena appears to have some relation 

 to the formation and decomposition of metallic lodes. Also that 

 "it is pretty certain analogically considered that these sulphides 

 should be able among themselves to form voltaic pairs in presence 

 of sea-water as they dift'er from each other in respect to their 

 affinities for oxygen." 



With these facts in my mind, I was therefore prepared to see 

 Mr. Wilkinson's results in a difierent light to that in which he 

 saw them, so I repeated his experiments in every detail excei^t 

 using organic matter. 



The case, therefore, as far as these results of Mr. Wilkinson 

 are concerned, is reduced to one in which there only remains to 

 consider the metallic sulphides and arsenides — minerals both 

 chemically and mineralogically related to each other. 



