composed of dots and dashes. On this point, priority has been claimed by
Swaim in a book that appeared at Philadelphia in 1829 under the title of
_The Mural Diagraph_, and in a communication inserted in the _Comptes
Rendus_ of the Academic des Sciences for Nov. 27, 1865.

[Illustration: FIG. 3.]

In 1828, likewise, Victor Triboaillet de Saint Amand proposed to
construct a telegraph line between Paris and Brussels. This line was to
be a subterranean one, the wire being covered with gum shellac, then
with silk, and finally with resin, and being last of all placed in glass
tubes. A strong battery was to act at a distance upon an electroscope,
and the dispatches were to be transmitted by the aid of a conventional
vocabulary based upon the number of the electroscope's motions.

Finally, in 1844, Henry Highton took out a patent in England for a
telegraph working through electricity of high tension, with the use of
a single line wire. A paper unrolled regularly between two points, and
each discharge made a small hole in it, But this hole was near one
or the other of the points according as the line was positively or
negatively charged. The combination of the holes thus traced upon two
parallel lines permitted of the formation of an alphabet. This telegraph
was tried successfully over a line ten miles long, on the London and
Northwestern Railway.

[Illustration: FIG. 4.]

We have followed electrostatic telegraphs up to an epoch at which
telegraphy had already entered upon a more practical road, and it now
remains for us to retrace our steps toward those apparatus that are