ould be heavy then the
fall must be steeper. A fair average drop is 3/4 inch to the foot. Be
careful that your copper tables are thoroughly water-tight, for remember
you are dealing with a very volatile metal, quicksilver; and where water
will percolate mercury will penetrate.

The blanket tables are simply a continuation of the mercury tables, but
covered with strips of coarse blanket, green baize, or other flocculent
material, intended to arrest the heavier metallic particles which, owing
to their refractory nature, have not been amalgamated.

The blanket table is, however, a very unsatisfactory concentrator
at best, and is giving place to mechanical concentrators of various
descriptions.

An ancient Egyptian gold washing table was used by the Egyptians in
treating the gold ores of Lower Egypt. The ore was first ground, it is
likely by means of some description of stone arrasts and then passed
over the sloping table with water, the gold being retained in the
riffles. In these the material would probably be mechanically agitated.
Although for its era ingenious it will be plain to practical men that if
the gold were fine the process would be very ineffective. Possibly, but
of this I have no evidence, mercury was used to retain the gold on the
riffles, as previously stated. This method of saving the precious metal
was known to the ancients.

At a mine of which I was managing director the lode was almost entirely
composed of sulphide of iron, carbonate of lime or calcspar, with a
little silica. In this case it has been found best to crush without
mercury, then run the pulp into pans, where it is concentrated. The
concentrates are calcined in a common reverberatory furnace, and
afterwards amalgamated with mercury in a special pan, the results as to
the proportion of gold extracted being very satisfactory; but it does
not therefore follow that this process would be the most suitable in
another mine where the lode stuff, though in some respects similar, yet
had points of difference.

I was lately consulted with respect to the treatment of a pyritic ore
in a very promising mine, but could not recommend the above treatment,
because though the pyrites in the gangue was similar, the bulk of the
lode consisted of silica, consequently there would be a great waste of
power in triturating the whole of the stuff to what, with regard to much
of it, would be an unnecessary degree of fineness. I am of opinion
that in cases such as