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

554 TELEGRAPH INSULATION.
seen in the figure, and the line wire is fastened to the cone
with tie wires. On the top of the pole is fitted an iron or
earthen covering, through which projects the iron pin for the
upper insulator. In its use it has proved to be a good insulator,
though the porcelain is very liable to be broken. When the
insulating cap breaks, the wire remains suspended to the iron
arm, and during wet weather the line is interrupted in its
working. These annoyances have been frequent, and to
remedy them other contrivances have been invented.
SEIMENS AND HALSKIE'S RUSSIAN INSULATOR.
Until the year 1S52, the insulators used on the continent
were made of glass, porcelain, or burnt clay. At that time
Messrs. Seimens &c Halskie proposed the bell-shaped insulator,
protected by an iron shield. Those then in use were fragile
and easily broken, even after they had been placed upon the
poles. Many of them would crack and absorb water, which
gave a conductor for the electric current, the means of passing
from the wire to the earth, or to the next wire on the same
line of poles. These cross currents were very great hinderances
to the successful working of the lines, and it naturally became
Fig. 61.
aDB-l =f v g i t t m t l h
a matter of very great importance to remedy the evil with all
the speed possible. To this end Messrs. Seimens & Halskie,
gentlemen distinguished for their great telegraphic skill, applied
their ingenious minds to the perfection of an insulator that
would more substantially subserve the purposes of the telegraphic service. After various improvements in the form and
insulating properties of materials, and their combinations, those