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 SARDINIAN INSULATOR. 551
seen as many as twelve wires on the same line of poles. They
were but a few inches apart. In the working of these wires
no difficulties were experienced. It must be borne in mind
that in France the battery current is not constantly on the line.
If the wires were continually charged, as they are in America,
it is possible, and very probable that the wires arranged as above
described, would be more or less subjected to cross or induced
currents as experienced on many of the duplicate wire lines
of America.
THE SARDINIAN INSULATOR.
Fig. 55 represents the insulation now used on the Sardinian
telegraph lines. It is made of glass, earthenware, or porcelain,
generally, however, of the latter. It is made with a circular
groove around its middle, in which Fig. 55
is placed an iron clamp, and the
clamp or staple is fastened to a perpendicular wooden beam. An iron.,
hook, in which is fastened the line F ull
wire, is cemented to the interior of
the porcelain. This hook, enlarged, A
is represented by the letter A to the i l 11
right and at the top of the figure.
To this hook is attached a binding
screw, which holds the line wire.
The perpendicular beams are fast-' 1 l
ened to the posts above and below
with iron bolts, fastening between i
the beam and the post large porcelain cylinders, as seen in the figure.
By this arrangement it is intended i
to have a double insulation, and I
have been informed that it fully
accomplishes the end contemplated.
In order to further perfect this insulation, it is proposed to place over
the porcelain a cap to serve as a roof. Each pole has its top
covered with a wooden or zinc cap, and to each too is attached
a lightning rod as seen in the figure. It consists of a large
iron. wire, made sharp at top and extending above the post
about six inches. It is conducted down the post into the earth.
Lightning rods similar to the above are also used upon some of
the lines in Holland. The extent of their usefulness has not
yet been determined. The earth connections have been frequently found to be imperfect. If the rods be connected with