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

THE PRINTING APPARATUS AND MANIPULATION. 279
a vacuum is made in the chamber c c', and the water comes
suddenly and fills it; when, on the contrary, the piston descends, the water can only with difficulty escape from the
chamber d' d, its passage consequently becomes very slow, and
the movement is thus retarded, as it is required, in order that
the telegraph may work perfectly.
Everything being arranged as I have just said, and the
electric communication being established, if the operator of the
sending station presses one of the keys with his finger, the key
A, for example, the type-wheel will stop, when the same letter
A arrives in front of the paper; then the lever L Li, fig. 3, will
turn, bring the cylinder in contact with the wheel, and press
the letter against the paper, which will receive the impression of that letter. As it withdraws, the cylinder will turn
upon its axis, and will present-on being brought back by the
movement of the axis and of the cranks-a new white space
to the new letter to be printed.
The mechanism for sounding the bell is very simple. AI, fig.
3, is a bell, N is the clapper, borne upon a rod or spring fixed
to the frame by an axis, around which it turns, and of which
the lower part is a small lever-arm, resting upon a pin about
one fifth of an inch long, when the eccentric turns, raises the
little lever-arm of the spring, and causes the clapper to descend
and strike the bell.
I have said nothing yet of the other portion of fig. 3. This
portion represents another manner of employing the Fig. 7
voltaic action. The rod or lever-arm T is now hori-
zontal; it is fastened on the one part to one of the
arms of the escapement, by means of a pin, upon
which it works, on the other part to an eccentric
placed upon a horizontal axis b', represented with
the eccentric in fig. 7. This same axis b bears a
lever, e', represented in fig. 8, and furnished with
points g and g', designed to stop the crooked parts to the
right and left of b, in fig. 7. B B B B B, fig. 3, Fi
are hollow bobbins or spools, magnets which
attract when the current traverses them;,
these little vertical magnets a a, are attached i
to the armature A A, of B, B, B, B,, another I
but a similar system of magnets; A, A, is the i
armature, E, E, are the extremities of the wire' 0
of the second system. When the first circuit is
closed by the armature A A, the extremity E,
is then in contact with E1 and the second circuit is closed in its
turn. The two circuits are also opened at the same time.