borax ready in which soak strips of old "table blanket," laying these
over the plate and sprinkling them with the borax solution when the
plate gets too hot. After a time the deposit of mercury and gold on
the plate will assume a white, efflorescent appearance, and may then be
readily parted from the copper.

_Another Method_

Heat the plate over an open fire, to drive off the mercury; after which,
let it cool, and saturate with dilute sulphuric acid for three hours,
or longer; then sprinkle over the surface a mixture of equal parts of
common salt and sal ammoniac, and heat to redness; then cool, and the
gold scale comes off freely; the scale is then boiled in nitric or
sulphuric acid, to remove the copper, previous to melting. Plates may be
scaled about once in six months, and will under ordinary circumstances
produce about one ounce of clean gold for each superficial foot of
copper surface employed. I always paint the back of the plate with
a mixture of boiled oil and turpentine, or beeswax dissolved in
turpentine, to prevent the acid attacking the copper.

HOW TO SUPPLY MERCURY TO MORTAR BOXES

I am indebted for the following to Mr. J. M. Drake, who, speaking of his
experience on the Wentworth Mine, N.S.W., says:

"Fully 90 per cent of the gold is saved on the outside plates, only a
small quantity remaining in the mortar. The plates have a slope of 2
in. to 1 ft. No wells are used, the amalgam traps saving any quicksilver
which may leach off the plates. The quicksilver is added every hour
in the mortar. The quantity is regulated by the mill manager in the
following manner: Three pieces of wood, 8 in. wide by 12 in. long by 2
in. thick, have 32 holes 1 in. deep bored in each of them. These holes
will just take a small 2 oz. phial. The mill manager puts the required
quantity of quicksilver in each bottle and the batteryman empties one
bottle in each mortar every hour; and puts it back in the hole upside
down. Each block of wood lasts eight hours, the duration of one man's
shift." This of course is for a 20-head mill with four mortars or
"boxes."

I commend this as an excellent mode of supplying the mercury to the
boxes or mortars. The quantity to be added depends on circumstances. A
careless battery attendant will often put in too much or too little
when working without the automatic feeder. I have known an attendant
on suddenly awaking to the fact half through his shift, that he had
forgotten to put in any mer