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

574 PARATONNERRE, OR LIGHTNING ARRESTER.
top of the house is fastened an arrangement consisting of two
copper plates PF P, to each of which the wire is attached; the
wire on the right being fastened to the middle of the right-hand
plate, and the wire on the other side fastened to the left-hand
plate.. These copper plates are about six inches in diameter,
and between them is laid a thin piece of silk cloth, so adjusted
that there can be no metallic connection between them. They
are held in a vertical position, as seen in the figure on the roof
of the station-house, by means of insulated supports, and they
are protected from the weather by means of a small roof
covering not placed in the figure.
By this means the large metallic circuit is interrupted or
made incomplete, the silk between the plates serving as a nonconductor. From the brass plate P, the line wire b is extended
down to the telegraph apparatus, and after traversing the coils
or bobbins, it returns at b', and is fastened to the plate P'.
When the line is charged, the voltaic current passes over
the wire to the plate P; thence over b to the apparatus;
thence over b' to plate P'; and thence over the line to the
next station. Atmospheric electricity will not pursue the
same course. It will not follow the wires b b' except in a
very small quantity. It passes from one plate to the other,
traversing the silk cloth, and then it follows the wire until it
becomes dissipated through proximate conductors to the earth.
The atmospheric electricity that passes over the wires b bY
and through the apparatus is but little, and can do no damage.
I was informed at many of the telegraph stations in Germany
that this form of paratonnerre has proved to be a perfect pro.
tection to the apparatus.
FARDLEY S PARATONNERRE.
Fig. 9. In the summer of 1847, Mr.
MD'' a Do Fardley constructed a paratonnerre on a stretch of fifty-six
__\ ________, \miles of line in the form repre.
sented by fig. 9.'|j^ — ^y'\^ A short distance from the
11 I- l-~ <s \ station-house the line wire was
I,^^ - divided into two parts, D D',
and on one side of the station
t, rP/t was placed a post, upon the
top of which the twro divided
ends of the line wire were
brought within one fiftieth of
an inch of each other. This
place of separation was covered