224 



pei'fectly bright and mobile in presence of sulphides, or the products of their 

 natural metamorphoses. 



Whether or no such an amalgam could ever be profitably substituted for 

 sodium amalgam in our gold batteries, has yet to be determined. I am 

 afraid that the continual addition of sulphuric acid to the water conveying the 

 auriferous stufi" to the plates, etc., which the use of this amalgam necessitates, 

 would increase so much the cost of extraction as to render it unprofitable ; 

 still, as the water need only be very slightly acidified, it may be well to keep 

 the fact thus arrived at in mind, when projecting intended improvements in 

 the amalgamation of the gold from auriferous reefs. 



In conclusion, I will only now remark, that the kind of phenomena just 

 described appear to have some relation to the formation and decomposition of 

 metalliferous lodes. 



It is pretty certain, analogically considered,* that these sulphides should be 

 able to foi-m among themselves a series of voltaic pairs in presence of saline 

 solutions, as they differ from each other in respect to their affinities for 

 oxygen. Galena and copper pyrites, for instance, should form a voltaic pair, 

 in which the galena would be the negative element ; sulphide of silver and 

 galena again should furnish another pair, in which the galena would have its 

 function reversed, and so on for the rest, according to their relative proneness 

 to change. 



In a natural way, therefore, the contact of dissimilar sulphides generally 

 should set wp galvanic action and chemical decomposition, and by setting 

 up this action, we might have a sulphide decomposed by saline solutions, 

 which it would be able to resist if it stood alone ; or, on the other hand, we 

 might have an easily decomposable sulphide preserved by the association with 

 it of one still more ready to decomjDOse. 



Since the results just detailed were arrived at, I have been referred by Dr. 

 Hector to a paper by Mr. Robert Hunt, entitled, " Researches on the Influence 

 of Magnetism and Voltaic Electricity on Crystallization and Conditions of 

 Matter," given in Memoirs of Geological Survey of Great Britain, Vol. i. 



The subject of that "paper is similar in part to this under consideration, 

 but I do not see that the author has anticipated any portion of the results 

 stated here ; he certainly does not demonstrate the actual and continuous pro- 

 duction of electricity by the contact of sulphides with positive bodies in saline 

 solutions ; nor does he show that copper pyrites conducts electricity, the water- 

 line being, as you will observe by reference to his diagram 14, page 457, above 

 the point of contact between the pyrites and the battery, so that the change or 

 decomposition of the ore need not involve the necessity of conducting power 

 in the pyrites, as in the case of that connected with the positive end of the 



* Since determined to be the case. — See Art. XLI. 



