sed; where the
wear is considerable, a larger proportion is employed.[38] White clay is
sometimes added to give body to the product; coloring matter is also
sometimes added.

By far the greater part of the crude rubber comes from the Amazon
forests. Brazil produces about one-half, but a considerable quantity is
obtained in Acre, the territory formed where the borders of Brazil,
Bolivia, and Peru meet, and now ceded to Brazil. Nearly all this
product, that of the Ceara region excepted, is marketed at Para and is
known as Para rubber. It is the best produced. The African product,
mainly from the forests of the Kongo, and Madagascar, and nearly all the
East Indian product is sent to Europe.

[Illustration: REGIONS YIELDING RUBBER]

The world's product is about one hundred and thirty-three million pounds
of crude rubber. Of this product the United States takes nearly
one-half. The greater part is used in the manufacture of pneumatic
tires, hose, and overshoes. A large part is used for making water-proof
cloth,[39] and considerable is made into the small elastic bands for
which there is a growing use.

=Gutta-Percha.=--Gutta-percha is obtained from the juices of several
plants (chiefly _Dichopsis gutta_ and _Supota muelleri_) both of which
abound in the Malay peninsula and the East Indies. It is prepared in a
manner somewhat similar to that employed in making crude rubber; it is
also easily vulcanized by heating with sulphur. It is used to a limited
extent in the manufacture of golf-balls, but mainly as the insulating
cover of copper wires used in ocean telegraph cables. For this purpose
it has no known substitute, and its essential merit is the fact that it
is not altered by salt water. Nearly all the product is shipped from
Singapore to England.

=Pine-Tree Products.=--The various members of the pine and cone-bearing
trees yield valuable essential oils and oleo-resins that are very
important in the arts and sciences. These, in nearly every instance, are
prepared from the sap of the tree.

_Oil of turpentine_ is known as an "essential oil," and in chemical
structure and properties it does not differ from the various essential
oils, such as lemon, orange, peppermint, etc. Commercial turpentine is
generally made from the sap of the long-leafed pine of the Atlantic
coast-plain.

The bark of the tree is cut near the foot, and the sap that oozes from
the scar quickly hardens into a gum. The gum, generally known as "crud