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 MANIPULATION. 399
Lying in an opposite direction. A steel cap x, fig. 5, two
inches in diameter, is so attached to the top of this shaft that
friction carries it along with it, but it can be moved in the
opposite direction; it has a small steel arm, three fourths of
an inch long, projecting from its side, and playing against the
teeth on the type wheel; while the latter is revolving, its
teeth strike this arm, and give the cap a contrary motion to its
shaft. There is a pulley on this shaft, below the plate, connected by a band to M, fig. 1; its speed is less than that of
the type wheel. When the type wheel comes to rest, the arm
falls between the teeth, but it has not time to do so when
they are in motion. On the opposite side of the cap to where
the arm is attached are two raised edges, called detent pins,
against which the detent arm u, fig. 5, alternately rests, as
the position of the cap is altered by the small arm that plays
on the teeth of the type wheel.
Between the type wheel and cap is a small lever and thumbscrew, 9, fig. 5, which acts as a break on the cap; its motion
can be stopped by it, while the type wheel revolves; it is used
merely to arrest the printing, though the message may be read
from the letter wheel.
The detent arm revolves in a horizontal direction about the
vertical shaft, which is also driven by a pulley beneath the
steel plate; when the type wheel is at rest, the detent arm
rests on one of the detent pins, but when it moves, the teeth
on its upper surface give the arm and cap a reverse direction
to its shaft, which alters the position of the detent points, so
that the detent arm is liberated from this first pin, and falls
upon the second, where it remains until the escapement and
type wheels again come to rest; when this happens, the arm
falls between two of the teeth, the cap resumes its first position,
the detent is let loose, makes a revolution, and stops again on
the first pin.
The shaft that carries the detent arm has an eccentric wheel,
K, fig. 5, on it, above the arm; an eccentric wheel is one that
has its axis of motion nearer one side than the other, and,
while revolving, operates like a crank; from this eccentric is
a connecting rod, s, which draws a toothed wheel against the
type; this toothed wheel is supported in an elastic steel arm
(shut out of view by the coloring band), on the opposite side of
the type wheel from that of the eccentric, and revolves in a
vertical direction; the band E, fig. 1, carrying the coloring
matter to print with, passes between this and the type; the
dots seen represent small teeth that catch the paper and draw
it along, as the wheel revolves, between itself and a steel clasp,