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affected by such solutions, not even when these are applied at the temperature 

 of their boiling points. 



This vulnerability of combined sulphur as against the invulnerability of 

 free sulphur, suggests that the former may in the first place have been set free 

 by the oxydation of the metallic portion, and being set free in a nascent form, 

 it might, by virtue of this, combine with oxygen as hydrogen, when in the 

 same state it combines with it, as shown in a former paper of mine. 



At the same time, it appears that su.lphur can be oxydized by these salts, 

 while it is in combination, — as in the case of the auriferous sulphide for 

 instance, — the metallic portion, of course, remaining throughout unattached, 

 and so iiltimately becoming quite reduced. 



Chromic acid, and cold nitric acid too, I may mention incidentally, aifect 

 this sulphide, as also the others, exactly as chloride of gold does, though 

 neither of them appear to have any action on native or precipitated sulphur at 

 common temperatures. 



The oxydation of sulphur in these cases it is more difficult to give a 

 reasonable explanation for, but probably as combined with the metals, it takes 

 quite a different form and characters to any of those yet known to be possessed 

 by it while in a free state. 



In conclusion, I would ask leave to observe in relation to these oxydizing 

 effects of gold solutions upon metallic sulphides, the rather singular circum- 

 stance that in full cognizance of the great oxydizing power of such solutions, 

 and also that of the proneness to oxydize exhibited by certain metallic 

 sulphides, the fact of the general association of gold with such sulphides did 

 not before suggest, rightly or wrongly, that such association had been due to 

 some mutual chemical interaction, obtaining between sohible auriferous salts 

 and those metallic sulphides in which gold occurs. 



This omission to apply the knowledge of such well known facts to the 

 explanation of the singular association of gold with these minerals — a problem 

 which has engaged so much attention — is encouraging in the extreme to those 

 who, like us, are cut off by our geographical position from the use of those 

 refinements of scientific research, and the inspiring contact with those great 

 master-minds enjoyed by others occupying more favourable positions ; since it 

 shows, that notwithstanding the great progress which has been made, and is 

 daily making, in scientific knowledge generally, the easier and more simple 

 applications of known facts to the interpretation of phenomena hitherto 

 unexplained, are not yet exhausted ; and it shows besides that there is still, 

 for those who wish it, work to do, and work which requires for its successful 

 prosecution only the simplest appliances, and very ordinary investigating 

 power. 



