_Mucilaginous_, consisting of mucilage.

_Tenacious_, adhering closely.

What is the character of Gum?

Gum is capable of being dissolved in water, and forming with it a
viscid transparent fluid; but not in vinous spirits or oil; it burns
in the fire to a black coal, without melting or catching fire; and
does not dissolve in water at boiling heat. The name of _gum_ has been
inaccurately given to several species of gum-resins, which consist of
resin and various other substances, flowing from many kinds of trees,
and becoming hard by exposure to the air. These are soluble in dilute
alcohol. Gum is originally a milky liquor, having a greater quantity
of water mixed with its oily parts, and for that reason it dissolves
in either water or oil. Another sort is not oily, and therefore
dissolves in water only, as gum Arabic, the gum of the cherry-tree,
&c.

_Viscid_, thick, ropy.

_Vinous_, having the qualities of wine.

Are the last-mentioned sorts properly called Gums?

No, though commonly called gums, they are only dried mucilages, which
were nothing else than the mucilaginous lymph issuing from the vessels
of the tree, in the same manner as it does from mallows, comfrey, and
even from the cucumber; the vessels of which being cut across, yield a
lymph which is plainly mucilaginous, and if well dried, at length
becomes a kind of gum, or rather, a hardened mucilage.

_Lymph_, transparent fluid.

What is Gum Arabic?

The juice of a small tree of the Acacia tribe, growing in Egypt,
Arabia Petraea, Palestine, and in different parts of America.

Are there other plants or trees which produce Gum, besides those
already mentioned?

A great number, though not all commonly in use. The leaves of rhubarb,
the common plum, and even the sloe and the laurel, produce a clear,
tasteless gum; there are also a number of different gums, brought from
foreign countries, of great use in medicine and the arts. Most of the
Acacias produce gums, though the quality of all is not equally good.

What is Rhubarb?

A valuable root growing in China, Turkey, and Russian Tartary.
Quantities of it are imported from other parts of the world: that from
Turkey is esteemed the best. Rhubarb is also cultivated in our
gardens, and the stalks of the leaves are often used in tarts; but the
root, from the difference of climate, does not possess any medicinal
virtue.

CHAPTER XII.

SPECTACLES, MARINER'S C