vestigation 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. The close relation which
the richness of gold veins bears to the prevalence of pyrites has been
long familiar both to scientific observers and to practical miners. The
gold is an after deposit to the pyrites, and, as Mr. Skey was the
first to explain, due to its direct reducing influences. By a series of
experiments Mr. Skey proved that the reduction of the metal was due to
the direct action of the sulphide, and showed that each grain of iron
pyrites, when thoroughly oxidised, will reduce 12 1/4 grains of gold
from its solution as chloride. 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 outburst or by the metamorphism of the
deeper-seated strata which compose the superficial crust of the earth.

Mr. Skey also showed by very carefully conducted experiments that the
metallic sulphides are not only better conductors of electricity than
has hitherto been supposed, but that when paired they were capable of
exhibiting strong electro-motive power. Thus, if galena and zinc blende
in acid solutions be connected in the usual manner by 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. The attributing
of this property of generating voltaic currents, hitherto supposed to
be almost peculiar to metals, to such sulphides as are commonly found
in metalliferous veins, further led Mr. Skey to speculate how far the
currents discovered to exist in such veins by Mr. E. F. Fox might be
produced by the gradual oxidation of mixed sulphides, and that veins
containing bands of different metallic sulphides, bounded by continuing
walls, and saturated with mineral waters, may constitute under
s