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battery, the conducting power necessary for this decomposition might well 

 have progressed around, from this point or line of contact by the liberation of 

 copper ; while, in case of the other piece of pyrites, all the conducting power 

 necessary for the production of the phenomena desci'ibed may, with propriety, 

 be referred to the wire bound around it. 



I would also state, that in repeating this experiment of Mr. Hunt's I find 

 that, different to his own observations as stated, both the pieces of pyrites are 

 chemically affected, while it is not that in contact with the copper of the 

 battery which displays su.ch marked iridescence, but that communicating with 

 the zinc ; and it passes into this state not by an oxydation process, but by a 

 desulphurizing one, brought about by the liberation of hydrogen vij)on its 

 surfaces ; this gas, when freshly liberated, having a desulphurizing effect upon 

 sulphides generally, as I have clearly shown above. 



Art. XL. — On the Reduction of Certain Metals from their Solutionis by 

 Metallic Sulphides, and the relation of this to the occurrence of such 

 Metals in a Native State. By W. Skey, Analyst to the Geological 

 Survey of New Zealand. 



[Read before the Wellington Philosophical Society, Novemter 12, 1870.] 



In a paper read by Mr. C. Wilkinson before the Royal Society of Victoria, 

 " Upon the Formation of G-old Nuggets," publicity is given to the fact, first 

 observed by Mr. Daintree, that gold when placed in a solution of its chloride, 

 undergoing decomposition by contact with organic matter, determines the 

 deposit of much, or all, the liberated gold upon itself. 



In the same pages, the author states that he finds copper, iron and arsenical 

 pyrites, galena, zinc blende, stibnite, wolfram, and molybdenite, also act as 

 nuclei for gold thus reduced ; but that brown iron ore and quartz do not. 



The general correctness of these statements has been verified by the results 

 of a critical enquiry, conducted by Mr. Cosmo Newberry, Analyst to the 

 Geological Survey of Victoria ; but I notice that there has not been any 

 attempt on the part of either of these authors to explain these very singular 

 phenomena. 



That gold itself should be nuclear to gold slowly precipitating from its 

 solution, is by no means abnormal or unrelated to other phenomena ; it is, in 

 fact, just what we should expect from a consideration of the mode of deposit 

 of numerous other substances from their solutions, whether such deposits are 

 crystalline or amorphotxs, they generally tend to aiTange themselves round a 

 nucleus of their own substance ; but that substances so chemically dissimilar as 

 those specified by Mr. Wilkinson, both as compared among themselves and to 

 gold, should also be nuclear under these circumstances, appeared altogether so 



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