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

550 TELEGRAPH INSULATION.
Fig. 49. Fig. 50.
porcelain or glass, and it is moulded with two side pieces or
ears, through each of which is a hole traversed by a screw
about three inches long, which fastens the insulator to the post.
The line wire is held by the hook suspended from the interior
of the bell. The iron hook is fastened by sulphur into the
highest part of the cavity, as seen in fig. 50.
Fig. 51 represents an insulator used on the early lines in
France. A slot was made in the insulator, in which was placed
the line wire, and then the insulator was fastened to the post.
Fig. 52 represents another form, through which there was a
hole for the line wire. It had to be threaded on the wire and
then fastened to the post as seen in the figure. This was
Fig. 51. Fig. 52. Fig. 53. Fig. 54.
called the ring or eye insulator. They have been considered
as inferior to the bell form, and are only used at obtuse angles
on the line. On the lines examined by me in France, I saw
but few of these insulators in use. Fig. 53 is another form of
insulation. The line wire is fastened to the bell-formed porcelain by being wound around it and tied by another wire. Each
bell or porcelain insulator is fastened lo an iron arm with
cement. Fig. 54 represents another form. The line wire is
wound around the grooved drum or cylinder.
The insulator most common in France is that represented by
fig. 49. They are fastened on each side of the pole. I have