Wellington Philosophical Society. 409 
of pyrites has been long familiar both to scientific observers and practical 
miners, and I remember in 1860 specimens of quartz were given to me in 
California having cavities left by the decomposition of cubic pyrites, and which 
contained only a brown powder of oxide of iron and thin films of gold, as 
showing that the pyrites and not the quartz was the true matrix of gold. 
This view, however, has not proved to be the correct one, the gold having 
been shown to be an after deposit to the pyrites, and, as Mr. Skey has been 
the first to explain, due to its direct reducing influence. It appears that in 
the first place my friend Mr. Daintree, who is now Agent-General for the 
Colony of Queensland, at the time he was on the geological survey staff of 
Victoria, pointed out that a nucleus of gold, when placed in a solution of 
chloride of gold undergoing decomposition by organic matter, is increased in 
bulk by a deposit of pure gold. Following up this hint, Mr. Wilkinson, also 
a Victorian chemist, found that many other substances, chiefly metallic 
sulphides, would also act as nuclei, but that quartz does not-do so; and Mr. 
Cosmo Newbury afterwards indorsed the correctness of these results. Tn this 
state of the question Mr. Skey took up the subject, and by-a series of 
experiments, which are detailed in our Transactions, proved that the organic 
matter is not at all necessary to produce the reduction of the metal, but that 
it is due to the direct action of the sulphide, and showed that each grain of iron 
pyrites, when thoroughly oxidised, will reduce 12} grains of gold from its 
solution as chloride, which is a proportion far beyond that which could be 
effected by the same weight of organic matter. He also included. salts of 
platina and silver in this general law, and demonstrated that solutions of any 
of these metals traversing a vein rock containing certain sulphides would be 
decomposed and the pure metal deposited. 
We are thus enabled to-comprehend the constant association of gold, or 
native alloys of gold and silver, in veins which traverse rocks containing an 
abundance of pyrites, whether they have been formed as the result of either 
sub-aqueous volcanic outbursts or by the metamorphism of the deeper-seated 
strata which compose the superficial crust of the earth. 
Still following the same line of induction, Mr. Skey has also shown by 
very carefully conducted experiments that the metallic sulphides are not only 
better conductors of electricity than bas hitherto been supposed, but that when 
paired they are capable of exhibiting strong electro-motive power. Thus, if 
galena and zinc-blende in acid solutions be connected in the usual manner of a 
voltaic pair, sulphuretted hydrogen is evolved from the surface of the former, 
and a current generated which is sufficient to reduce gold, silver, or copper 
from their solutions in coherent electro-plate films. 
By pairing the different metallic sulphides Mr. Skey was further able to 
construct a table of their relative value as electro-motors and conductors 
B 2 
