of copper.

On September 13, 1839, Spencer read a paper before the Polytechnic
Institution of Liverpool, which he accompanied with specimens of both
electrotypes made by this process and of printing from these
electrotypes. The publication of this paper acted like an electric
shock upon society.

Developing his process, Spencer first used lead as the plastic medium
in which to mold printing surfaces, and it is to be noted in this
connection that in doing so he anticipated Dr. Albert's lead mold by
considerably over three quarters of a century.

Spencer impressed a form of type on a planed piece of sheet-lead and
subjected both of them to the action of a screw-press. A perfectly
sharp mold of the type form was thus made in the lead. This lead mold
was placed in a battery, and at the end of _eight days_ a copper shell
one eighth of an inch in thickness had been deposited. It was then
removed from the apparatus and the rough edge of the deposited copper
filed off. Being subjected to heat, the copper shell loosened from the
lead-mold. Spencer called this a "copper stereotype."

[Illustration]

The next step in developing the electrotyping process, after Spencer
had demonstrated the practical application of the electro-chemical
deposition of a copper shell on a mold, was made by a Mr. Robert
Murray. Mr. Murray was the first to use plumbago, or black-lead, to
give the surface of non-metallic bodies electro-conductive properties.
He discovered that he could coat a mold of bees-wax with black-lead
and deposit thereon a copper shell. This was in 1840.

In the same year Smee's battery was invented. This was a marked
improvement and was a most important step towards making electrotyping
a commercial possibility.

Thus in 1840, four hundred years after the probable date of the
invention of printing from individual movable cast-metal type, and
over forty years after the foundation of electrotyping was laid by
Volta, electrotyping, as a practical method of reproducing a
commercial typographical printing surface, came into existence.

Mr. E. Palmer, in England, using Spencer's method, was the first to
receive a patent for producing a metallic printing plate with the
printing surfaces in relief. This patent is dated 1841. Palmer
followed this in the succeeding year by a further patent for engraving
through a wax-coated matrix-plate to form the printing surfaces in the
_positive_ electrotype taken from it. This process was te