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

316 SEIMENS AND HALSKIE S GERMANIC TELEGRAPH.
tally exactly at the middle of the lever-arm L L1; its foot at n,
rubs, in the least degree possible, upon the band which supports it; and, in order that the shuttle may be completely insulated from the metallic plate Pi, this foot is covered at its
lower extremity with an agate stone. The movement of the
shuttle, always quite circumscribed, is limited by the screws
e el, and these screws are borne by two uprights, fixed to the
plates Pi p, and, their heads being rounded, they fit into the
cavities of the metallic appendages a a,; by means of these
screws, the movement of the shuttle n n1 can be regulated.
When the appendage a, touches the screw e,, the appendage a
is at a, small distance from the screw e, and reciprocally; a
wire spring, slightly stretched at fi, fixed to the shuttle itself,
and which is shown by the dotted lines in the figure, tends to
keep the appendage a1 constantly in contact with el, and prevents the little jars and oscillations of the shuttle from ever
occasioning a momentary separation of a, and el. It is then
the appendage a1 and the screw e1, which establishes the
metallic contact necessary for the closing of the circuit. The
only function of a and e is to circumscribe the movement of
the shuttle. The nut m is connected in the movement of the
lever L L,, and presses, alternately, sometimes upon a. and
sometimes upon a,; but as it is a trifle shorter than the distance between a and a1, it cannot move between a and a, without taking the shuttle with it in its movement. In the figure,
m presses against a, if the lever-arm moves from the side of
a1, the shuttle will, at first, remain immoveable, but a moment
before the hook tj engages above the following tooth, the nut m
presses against a, and at that instant it displaces the shuttle;
there is then no longer communication between a1 and el; a is
then in non-metallic contact with e1. The shuttle remains in
this position until the armature, dropping down, makes the nut
m press against 1a, and re-establishes the metallic contact between a, and el, by separating a from e; it will be seen that
the extent of the movement of the lever-arm L L1 is much
greater than that of the shuttle, and that it is only at the moment that the lever has arrived at its maximum, right or left
point of separation, that the shuttle makes a very small movement, first to the one side and then to the other.
One of the ends b1 of the wire of the electro magnet connects
with a pressure screw, the other end of the wire traverses the
hole T1, and connects at b, with the support s1 of the shuttle;
another wire is screwed to the plate p1, and has metallic communication with el, which also traverses the hole T1, and is
fixed to a pressure screw. If, then, bi and a'2 are united to