ls withdraw the magnet and drop the adhering
fragments into a receptacle by automatically switching off the electric
current. A powerful ordinary horseshoe magnet might probably do just as
well, but would require to be re-magnetised from time to time.

TO SILVER COPPER PLATES

To silver copper plates, that is, to amalgamate them on the face with
mercury, is really a most simple operation, though many batterymen make
a great mystery of it. Indeed, when I first went into a quartz mill the
process deemed necessary was not only a very tedious one, but very dirty
also.

To amalgamate with silver, in fact, to silver-plate your copper without
resort to the electro-plating bath, take any old silver (failing that,
silver coin will do, but is more expensive), and dissolve it in somewhat
dilute nitric acid, using only just sufficient acid as will assist the
process. After some hours place the ball of amalgam in a piece of strong
new calico and squeeze out any surplus mercury.

About an ounce of silver to the foot of copper is sufficient. To apply
it on new plates use nitric acid applied with a swab to free the surface
of the copper from oxides or impurities, then rub the ball of amalgam
over the surface using some little force. It is always well when coating
copper plates with silver or zinc by means of mercury to let them stand
dry for a day or two before using, as the mercury oxidises and the
coating metal more closely adheres.

Only the very best copper plate procurable should be used for battery
tables; bad copper will always give trouble, both in the first "curing,"
and after treatment. It should not be heavily rolled copper, as the
more porous the metal the more easily will the mercury penetrate and
amalgamate. I cannot agree that any good is attained by scouring the
plates with sand and alkalies, as recommended in some books on the
subject; on the contrary, I prefer the opposite mode of treatment, and
either face the plates with nitrate of silver and nitrate of mercury,
or else with sulphate of zinc and mercury, in the form of what is
called zinc amalgam. If mine water, which often contains a little free
sulphuric acid, is being used, the latter plan is preferable.

The copper should be placed smoothly on the wooden table and secured
firmly thereto by copper tacks. If the plate should be bent or buckled,
it may be flattened by beating it with a heavy hammer, taking care to
interpose a piece of inch-thick soft wood bet