The telegraph manual: a complete history and description of the semaphoric, electric and magnetic telegraphs of Europe, Asia, Africa, and America, ancient and modern.

398 THE HOUSE PRINTING TELEGRAPH.
escapement wheel to move the escapement and piston twentyeight times, and allows one revolution of the escapement wheel
for one of the circuit wheel at the transmitting station.
A steel type wheel, fig. 5, A, B, c, D, two inches in
diameter, is fixed above and revolves on the same shaft with
the escapement wheel; it has on its circumference twentyeight equi-distant projections, on which are engraved in order
the alphabet, a dot, and a dash. The fourteen notches of the
escapement wheel cause twenty-eight vibrations of the escapement in a revolution, that correspond to the characters on the
type wheel. Every vibration of the escapement, therefore,
makes the type wheel advance one letter; these letters correspond to those on the keys of the composing machine. If any
desired letter on the type wheel is placed in a certain position,
and a corresponding key in the composing machine is depressed,
by raising that key, and again depressing it, the circuit wheel
at one station, and the escapement and type wheels at the
other station, all make a single revolution, which brings that
letter to its former position. Any other letter is brought to
this position by pressing down its key in the composing
machine, the circuit being broken and closed as many times
as there are letters from the last one taken to the letter
desired.
THE MANIPULATION.
To form the letters into words, it is necessary that the
printing and composing machines should correspond, and for
this purpose a small break and thumb screw, 9 and 10, fig. 5,
can be made to stop the type wheel at any letter. In sending
messages, they usually commence at the dash or space; if,
by accident, the type wheel ceases to coincide with the
distant composing machine, the printing becomes confused,
the operator stops the type wheel, sets it at the dash, and the
printing goes on as before.
Above the type wheel, on the same shaft, is the letter wheel
E, fig. 5, on the circumference of which the letters are painted
in the same order with those on the type wheel below. It is
incased in a steel hood, having an aperture in it directly over
where the letters are printed, so that when the type wheel
stops to print a letter, the same letter is made stationary for
a moment at the aperture, and is readily distinguished; hence
messages can be read, thus making it a visual telegraph.
The type wheel has twenty-eight teeth arranged on the
outer edge of its upper surface; near it, on the opposite side
from where the printing is done, is the shaft T, fig. 5,