408 Proceedings. 



One of the subjects of most general interest on whicli Mr. Skey has 

 written disproves the view generally held that gold is nnaftected by sulphur 

 or sulphuretted hydrogen gas, and shows on the other hand that these 

 elements combine with avidity, and that the gold thus treated resists amalga- 

 mation with mercury, a most important fact, which, it will be remembered, 

 was strikingly illustrated by experiment after one of our meetings. The author 

 has also proved this act of absorption of sulphur by gold to be a chemical act, 

 as he has shown that electricity is generated in sufficient quantity and 

 intensity during the process to decompose metallic solutions. He thinks 

 further that much native gold is thus sulpliurized, and that this circumstance 

 is the greatest obstacle to its thorough amalgamation in ordinary quartz mills. 



Mr. Skey was led to this interesting observation while investigating the 

 Ciiuses of the loss of gold experienced in the Thames district, and the object of 

 his inquiry must be held to have been satisfactorily accomplished by the 

 discovery of this important fact. 



He was aware that sulphur in certain forms has long been known to 

 exercise a prejudical effect upon the amalgamation of gold, but this has always 

 been attributed to the combination of the sulphur with the quicksilver used; 

 now, however, it is certain that the sulphurizing of the gold itself must be 

 taken into account. So lono- as our chemical books described sold as beinar 

 unaffected by sulphuretted hydrogen it appeared as if in the ordinary amalga- 

 mating process we had nothing to fear from this gas, except its effect upon the 

 mercury, but now that it is proved that gold itself is also readily attacked by 

 this compound we must take the circumstance also into account that the 

 particles of gold in the stone may be enveloped with a film of auriferous 

 sulphide, by which they are protected from the solvent action of the mercury. 



The merit of this discovery, from an experimental point of view, is that 

 the sulphurization of the gold gives no ocular manifestation by change of 

 colour or perceptible increase of weight, as in the case of the formation of 

 sulphides of silver, lead, and other metals, on account of the extremely 

 superficial action of the sulphur, and hence probably the existence of the gold- 

 sulphide hitherto escaped detection by chemists. 



Closely allied to this subject is the investigation of the mode in which 

 certain metals are reduced from their solutions by metallic sulphides, or, in 

 common language, the influence which the presence of such substances as mundic 

 and galena may exercise in effecting the deposit of pure metals such as gold in 

 mineral lodes. As this investigation has a very direct bearing on the discus- 

 sions relative to the origin of large gold nuggets and the heavy masses of gold 

 that are sometimes found in reefs formed by hydrothermic agencies, I will 

 take this opportunity of stating the position of the question. 



The close relation w-hich the richness of gold veins beai-s to the prevalence 



