in and the drum were respectively connected so as to
be in circuit with the transmission line and batteries. As the principle
involved in the receiving operation was electrochemical decomposition,
the paper tape upon which the incoming message was to be received was
moistened with a chemical solution readily decomposable by the electric
current. This paper, while still in a damp condition, was passed
between the drum and stylus in continuous, progressive motion. When an
electrical impulse came over the line from the transmitting end, current
passed through the moistened paper from the iron pin, causing chemical
decomposition, by reason of which the iron would be attacked and would
mark a line on the paper. Such a line would be long or short, according
to the duration of the electric impulse. Inasmuch as a succession of
such impulses coming over the line owed their origin to the perforations
in the transmitting tape, it followed that the resulting marks upon the
receiving tape would correspond thereto in their respective lengths.
Hence, the transmitted message was received on the tape in visible dots
and dashes representing characters of the Morse alphabet.

The system will, perhaps, be better understood by reference to the
following diagrammatic sketch of its general principles:

Some idea of the rapidity of automatic telegraphy may be obtained when
we consider the fact that with the use of Edison's system in the early
seventies it was common practice to transmit and receive from three to
four thousand words a minute over a single line between New York and
Philadelphia. This system was exploited through the use of a moderately
paid clerical force.

In practice, there was employed such a number of perforating machines
as the exigencies of business demanded. Each machine was operated by
a clerk, who translated the message into telegraphic characters and
prepared the transmitting tape by punching the necessary perforations
therein. An expert clerk could perforate such a tape at the rate of
fifty to sixty words per minute. At the receiving end the tape was taken
by other clerks who translated the Morse characters into ordinary words,
which were written on message blanks for delivery to persons for whom
the messages were intended.

This latter operation--"copying." as it was called--was not consistent
with truly economical business practice. Edison therefore undertook the
task of devising an improved system whereby the me