bout. Instances are not wanting of the growth of
silica on the sides of the drives in mines. This was so in some of the
mines on the Thames, New Zealand, previously mentioned, where in some
cases the deposition was so rapid as to be noticeable from day to day,
whilst the big pump was actually choked by siliceous deposits. In old
auriferous workings which have been under water for years, in many parts
of the world, formations of iron and silica have been found on the
walls and roof, while in mining tunnels which have been long unused
stalactites composed of silica and calcite have formed. Then, again,
experiments made by the late Professor Cosmo Newbery, in Victoria,
showed that a distinctly appreciable amount of gold, iron, and silica
(the latter in granular form) could be extracted from solid mine timber;
which had been submerged for a considerable time.

This reaction then must be in progress at the present time, and
doubtless under certain conditions pyrites would eventually take
the place of the timber, as is the case with some of the long buried
driftwood found in Victorian deep leads. Again, we know that the water
from some copper mines is so charged with copper sulphate that if scrap
iron be thrown into it, the iron will be taken up by the sulphuric acid,
and metallic copper deposited in its place. All this tends to prove that
the deposition of metals from their salts, though probably not now
as rapid as formerly, is still ceaselessly going on in some place or
another where the necessary conditions are favourable.

With regard to auriferous pyritic lodes, it does not appear even now to
be clear, as some scientists assert, that their gold is never found
in chemical combination with the sulphides of the base metals. On the
contrary, I think much of the evidence points in the other direction.

I have long been of opinion that it is really so held in many of the
ferro-sulphides and arsenio-ferro sulphides. On this subject Mr. T.
Atherton contributed a short article in 1891 to the _Australian Mining
Standard_ which is worthy of notice. He says, referring to an occurrence
of a Natural Sulphide of Gold: "The existence of gold, in the form of
a natural sulphide in conjunction with pyrites, has often been advanced
theoretically, as a possible occurrence; but up to the present time
has, I believe, never been established as an actual fact. During my
investigation on the ore of the Deep Creek mines, Nambucca, New South
Wal