e,
an impression of it is taken in a composition resembling wax which is
spread upon a metal slab to the thickness of about one-twelfth of an
inch. Both the surface of the type and of the wax are thoroughly
coated with plumbago or black lead, which serves as a lubricant to
prevent the wax from adhering to the type.

As the blank places in the form would not provide sufficient depth in
the plate, it is necessary to build them up in the wax mould by
dropping more melted wax in such places to a height corresponding to
the depth required in the plate, which is, of course, the reverse of
the mould, and will show corresponding depressions wherever the mould
has raised parts. If great care is not taken in this operation of
"building-up," wax is apt to flow over into depressions in the mould,
thereby effacing from it a part of the impression, and the plate
appears later without the letters or words thus unintentionally
blotted out. The reviser of the plate-proofs must watch carefully for
such cases.

The mould is now thoroughly brushed over again with a better quality
of black lead than before, and this furnishes the necessary metallic
surface without which the copper would not deposit. Then it is
"stopped out" by going over its edges with a hot iron, which melts the
wax, destroys the black-lead coating, and confines the deposit of
copper to its face.

After carefully clearing the face of the mould of all extraneous
matter by a stream of water from a force-pump, it is washed with a
solution of iron filings and blue vitriol which forms a primary copper
facing. It is then suspended by a copper-connecting strip in a bath
containing a solution of sulphate of copper, water, and sulphuric
acid. Through the instrumentality of this solution, and the action of
a current of electricity from a dynamo, copper particles separate
from sheets of copper (called "anodes," which are also suspended in
the bath) and deposit into the face of the mould, thus exactly
reproducing the elevations and depressions of the form of type or
illustrations of which the mould is an impression. After remaining in
the bath about two hours, when the deposit of copper should be about
as thick as a visiting card, the mould is taken from the bath and the
copper shell removed from the wax by pouring boiling hot water upon
it. A further washing in hot lye, and a bath in an acid pickle,
completely removes every vestige of wax from the shell. The back of
the shell is