per minute between New York and Washington, and thirty-five hundred
words per minute to Philadelphia. Ordinary manual transmission by key
is not in excess of forty to fifty words a minute. Stated very briefly,
Edison's principal contribution to the commercial development of the
automatic was based on the observation that in a line of considerable
length electrical impulses become enormously extended, or sluggish, due
to a phenomenon known as self-induction, which with ordinary Morse work
is in a measure corrected by condensers. But in the automatic the aim
was to deal with impulses following each other from twenty-five to one
hundred times as rapidly as in Morse lines, and to attempt to receive
and record intelligibly such a lightning-like succession of signals
would have seemed impossible. But Edison discovered that by utilizing
a shunt around the receiving instrument, with a soft iron core, the
self-induction would produce a momentary and instantaneous reversal of
the current at the end of each impulse, and thereby give an absolutely
sharp definition to each signal. This discovery did away entirely with
sluggishness, and made it possible to secure high speeds over lines of
comparatively great lengths. But Edison's work on the automatic did
not stop with this basic suggestion, for he took up and perfected the
mechanical construction of the instruments, as well as the perforators,
and also suggested numerous electrosensitive chemicals for the
receivers, so that the automatic telegraph, almost entirely by reason of
his individual work, was placed on a plane of commercial practicability.
The long line of patents secured by him in this art is an interesting
exhibit of the development of a germ to a completed system, not, as
is usually the case, by numerous inventors working over considerable
periods of time, but by one man evolving the successive steps at a white
heat of activity.

This system was put in commercial operation, but the company, now