a.—Its liability to become hard and brittle when exposed to dry heat, and consequently it requires to be stored under water.
b.—It becomes comparatively a bad dielectric at 100° F.
c.—It becomes plastic at high temperatures, which causes the conducting wire to alter its position.
In some particulars ordinary india rubber is a better insulator than gutta percha, but this substance is equally inferior to Hooper's material, &c. The advantages possessed by this substance are:—
a.—It is not easily affected by a dry heat.
b.—It is a very excellent dielectric.
The defects of this mode of insulation are:—
a.—It must be put on the conducting wires in a series of jointed pieces.
b.—It does not cling to the conducting wire, so that if the electric cable be cut, and any strain be brought on it (cable), the previous fault is increased.
c.—It absorbs 25 per cent. of water.