has been introduced in which there is added finely pulverized tin to
the graphite for facing the wax mould; the effect in the sulphate of
copper bath is to cause a rapid deposition of copper by the
substitution of copper for the tin, the latter being seized by the
oxygen, while the copper is deposited upon the graphite. The film is
after increased by the usual means. Knight's expeditious process
consists in dusting fine iron filings on the wet graphite surface of
the wax mould, and then pouring upon it a solution of sulphate of
copper. Stirring with a brush expedites the contact, and a
decomposition takes place; the acid leaves the copper and forms with
the iron sulphate a solution which floats off, while the copper is
freed and deposited in a pure metallic form upon the graphite. The
black surface takes on a muddy tinge with marvelous rapidity. The
electric-connection gripper is designed to hold and sustain the
moulding pan and make an electric connection with the prepared
conducting pan of the mould only, while the metallic pan itself is out
of the current of electricity, and receives no deposit.