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 PARATOTNERRE..)81
communicator which puts in communication this wire either
with the strip N, or with the strip x Y z, or finally with the
copper plate w, which is in communication with the earth
wire.
In the first case, the current of the line must traverse the.
wire of the paratonnerre; in the Fig. 17.
second, it goes directly to the apparatus; and, in the third, it goes to L
the earth.
Whenever the weather is stormy,
this latter communication ought
always to be established. The W
plates w and L are furnished with
points, the use of which is the same
as that of the paratonnerre hereinbefore described. When there is a x
prospect of a storm, the spring of I
the commutator u should be placed
upon the strip x Y, but if the silk M
covered wire surrounding the rod
M N is laid bare at certain points,
the current, instead of traversing
the wire of the apparatus, which
offers a great resistance, goes di- R
rectly to the earth by means of the
support R. In order to prevent all
communication between the plate
x Y z and the earth, the rod must
be removed. 0 Q
Attempts have been made in
France to avoid this inconvenience,
by giving to the paratonnerre the
following form, which has been z
recently adopted on some of the
lines (fig. 18).
This apparatus consists of a little
vertical column, at the base of {
which are attached three little copper binding screws. At T,
the wire of the earth is connected; at L, the line wire; and at
A, the wire of the telegraph apparatus.
The binding screw L communicates with the axis ii of a
three-pronged commutator, which can be moved by means of
the lever or arm K. The plate A represents'" with paratonnerre, B represents "earth," and c represents " without
paratonnerre."