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

PROPERTIES OF GUTTA-PERCHA. 527
"The tubes were three fourths inch bore, the material one
eighth thick. They were tested by the Water Company's
proving pump, with its regular load of 250 pounds to the
square inch; afterward we added weight up to 337 pounds,
and I wished to have gone to 500 but the lever of the valve
would bear no more weight; we were unable to burst the
pipe." Another gentleman, Mr. Andrew Robertson, of Stirling,
says: " I am of opinion that no other material is so well fitted
for the above purposes" (extinguishing fires and watering the
streets in dry weather) " as gutta-percha; for, although our
pressure is perhaps the greatest in the kingdom, being upward
of 450 feet, not the slightest effect could be discovered on the
tube or joints, while the same pressure on our leather hose
sends the rivets in all directions."
The application of heat to this crude material makes it soft
and plastic, and in a temperature of about 200 degrees it becomes quite ductile, when it is capable of being moulded into
any desired shape, which it will retain when cool. It can be
dissolved by sulphurct of carbon, or chloroform, or if immersed for a time in spirits of turpentine. It is repellant of
and completely unaffected by cold water, but is softened and
made adhesive by warm water. It is a a non-conductor of heat
and electricity; is proof against alkalies and acids, being only
affected by the sulphuric or nitric in a highly concentrated
state; while the most powerful acetic, hydrofluoric or muriatic
acids or chlorine have no perceptible effect upon its structure
or capabilities. This gum has qualities entirely differing from
the India-rubber. It cannot be worn out. It can be melted
and remelted, and repeatedly remoulded without changing its
properties for manufacture or losing its virtue. It is lighter than
rubber, of finer grain, and possesses certailmarepellant properties unknown to that material, and is extremely tough. It
disregards frost and displays remarkable acoustic qualities.
In its crude state gutta-percha has no resemblance whatever to India-rubber in appearance, nor are its chemical or
mechanical properties the same, nor does the tree from which
it is taken belong to the same botanical family, or grow in the
same latitudes or soil; yet, from the fact that it could be dissolved and wrought into water-proof wares, many have inclined
to the belief that the two materials are identically or nearly
the same.
Gutta-percha when immersed in boiling water, contracts in
bulk.
India-rubber when immersed in boiling water, expands and
increases in bulk.