peans
continued ignorant of its origin until a deputation of the French
Academicians undertook a voyage to South America in 1735, for the
purpose of obtaining the correct admeasurement of a degree of the
meridian. These philosophers did not confine their attention to the
one great object of their pursuit, but among other interesting
discoveries made themselves acquainted with that peculiar
substance--caoutchouc. These Academicians discovered at Emeralds, in
Brazil, trees called by the natives _heve_, whence flowed a juice,
which, when dried, proved to be what is called India Rubber. The
_heve_ was also found growing in Cayenne, and on the banks of the
Amazon river. It has since been discovered that caoutchouc may be
obtained from another species of tree growing in South America, called
_jatropha elastica_. If these trees are punctured, a milky juice flows
out, which, on exposure to the air, thickens into a substance of a
pure white color, having neither taste nor smell. The hue of the
caoutchouc of commerce is black in consequence of the method employed
in drying it. The usual manner of performing this operation is to
spread a thin coating of the milky juice upon the moulds made of clay,
and fashioned into a variety of figures. These are then dried by
exposure to the heat of a smoke-fire: another layer is then spread
over the first, and dried by the same means; and thus layer after
layer is put on, until the whole is of the required thickness. While
yet soft it will receive and retain any impression that may be given
to if on the outside. When perfectly dry the clay within is broken
into small fragments by percussion, and the pieces are drawn out
through the aperture which is always left fur the purpose. The common
bottle of India Rubber, therefore, consists of numerous layers of pure
caoutchouc, alternating with as many layers of soot.

The natives of those parts of South America to which these trees are
indigenous, convert the juice to a variety of purposes. They collect
it chiefly in the rainy season, because, though it will exude at all
times, it flows then most abundantly. Boots are made of it by the
Indians, through which water cannot penetrate; and the inhabitants of
Quito prepare a kind of cloth with it, which they apply to the same
purposes as those for which oil-cloth or tarpaulin, it used here.
This, no doubt, is similar to the cloth now prepared with this
substance in America, the use of which yields so man