W. Sxey.—Auriferous Alloys. 371 
occurrence in our reefs), we obtain that mixed deposit or alloy we are seeking 
to produce. 
The only condition which appears to me from the results of numerous 
experiments necessary in regard to such metallic solutions is that they should 
be not only alkaline, but alkaline from presence of a fixed alkali or alkaline 
earth, and it will be remembered, perhaps, in connection with this circum- 
stance, that this alkaline condition is one which I have recently shown* to 
be that of our silicates generally, whether simple or compound, with the 
exception of silicate of alumina and other corresponding silicates of the 
sesqui-oxides, while quartz itself, whether free or in combination, is either 
quite neutral or of such very feeble acidic powers as regards intensity that 
when united, even in very greatly disproportionate quantity, with alkalies or 
alkaline earth the resulting compound gives an alkaline reaction. 
If such then are the conditions (alkalinity or neutrality) of our surface 
rocks generally, it is clear that the condition of the water permeating them 
at some distance from the surface would be alkaline, the intensity of which 
would be largely increased were the retaining rock subjected to those hydro- 
chemical influences popularly supposed to have operated for the deposition 
of their older vein matters and their metallic contents. 
The fact that many mine waters are acid does not affect the truth of the 
conclusion thus drawn as to the general alkaline condition of the waters 
charging our rocks, since this acidity is, as is well known, brought about by 
the contact of air with pyritous matters, metallic sulphates thus being formed 
which communicate an acid reaction to water dissolving them. This is a 
mere surface affair as it were, and is besides in its manner of production 
entirely distinct from, if not antagonistic to that by which gold has been 
deposited in the pyritous portions, for a slight examination of these shows 
that the gold present in them has been deposited there before they were 
oxidized by atmospheric agency. 
Alkalinity being then certainly the general condition of our waters per- 
meating rocks, closed, or partially so, against the atmosphere, and this con- 
dition of liquids appearing essential for the production of alloys by humid 
methods, as shown here, it does seem highly probable that our native alloys 
of gold and silver have been deposited from alkaline solutions, and by such 
agents as I have suggested, viz, the metallic sulphides. 
I will only add, in reference to the mode in which our deposits of native 
gold have been formed, that while the number of substances capable of pre- 
cipitating this metal from solution is many, the number of those at all likely 
to have been actually concerned in the production of these deposits is very 
small indeed. As far as at present appears, the substances capable of reducing 
* Trans. N.Z., Inst., Vol. IV., Art. LVI. 
