machine which is in common use today.

In 1871, Silas P. Knight, of Harper & Bros., New York, invented the
wet black-leading process, and in 1872 took out another patent for an
improvement on this process. Mr. Knight's method of wet black-leading
was not generally adopted by the electrotypers of that time and
gradually became almost unknown.

Undoubtedly, the cause of this was that the method of dry
black-leading was good enough for type and woodcut work. The half-tone
had not been invented at that time, and it was only after the
invention of the half-tone that a better method of black-leading
became necessary.

Thirty-seven years after Mr. Knight had successfully used his process
of wet black-leading a patent was granted to Frank L. Learman, of
Buffalo, New York, for a wet black-leader. Since that time numerous
patents have been taken out on different methods of using the wet
process, which is universally recognized today as the best method of
graphiting the surface of a mold.

In 1870, Joseph A. Adams patented a process for covering the surface
of the mold after it had been black-leaded with powdered tin. This was
for the purpose of quickening the deposition of the copper shell when
the molds were in the batteries, and from this undoubtedly came the
oxidizing process of coating the surface of the molds with chemical
copper invented by Silas Knight, which has long been and is now in
use.

Perhaps one of the greatest forward steps in the development of
electrotyping was made when the plating dynamo was invented. The first
adoption of a dynamo in place of Smee's battery took place in 1872.
With the Smee type of battery it required from thirty to forty-eight
hours to deposit a copper shell thick enough for commercial use. With
the invention of the plating dynamo and its improvements, the time of
depositing the shell was reduced so that now two hours is the common
time that a mold is kept in the tubs or batteries. This quickening of
the time required to deposit the shell was one of the most essential
features in the development of commercial electrotyping.

From the first hand-screw presses, which were successfully used for
molding, to the modern high-power, motor-driven, hydraulic presses,
for working either in wax or lead, is a far cry.

The invention of the half-tone, together with the invention of the
modern two-revolution cylinder press which has brought printing into
its present state of perfection, made nec