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 FRENCH PARATONNERRE. 579
another plate E, with saw-teeth, fastened so that the teeth of
the two former almost touch the teeth of plate E. From P P'
the wires 1 1' run and connect with the telegraph apparatus.
The wires I I' are connected to the plates L L/ by means of the
binding posts P PV. The middle plate E is connected with the
earth by a large copper wire e. The voltaic current follows
the metallic circuit L/ 1, the apparatus I and L, or vice versa.
The atmospheric electricity escapes through the plate E and
wire e to the earth.
THE FRENCH PARATONNERRES.
Fig. 15 represents a form used on the French railway lines.
It is composed of a small wooden plate Al N, upon which are
placed binding screws, B and c, from Fi 1
two and a half to three inches apart. A
A very fine iron or platina wire, A
fixed at its two extremities in two
copper posts, and placed in a glass M I
tube, connects these two binding
screws or posts. i
The upper part B communicates
with the line A; the lower part c
communicates with the wire of the
station D. The current coming from
the line must traverse the fine wire,
B C, so that if the electric discharge
is strong enough, this wire will melt P
and interrupt the communication
between the line and the apparatus.
In front of the upper binding D T
screw B is a metallic piece, E, communicating with the earth. Copper points placed in front
permit the electricity accumulated on the line wire to pass
into the earth whenever the small wire is burnt.
It sometimes happens that the wire contained in the glass
tube is volatilized by the effect of the discharge, and is precipitated against the tube so as to form a sort of conducting
lining. The glass tube, however, is frequently dispensed with,
as the sole object of its use is to protect the wire which it contains. When the wire is melted by the electric discharge, it
must be replaced in order to re-establish electric communication. The French are of the opinion that these paratonnerres
should be placed as much as possible outside the station-houses,
in order that the line may be completely separated from the,