Common resin is obtained by distilling the exudation of different species
of fir; oil of turpentine passes over, and the resin remains behind.

_Why are the varieties of the cashew tribe, called varnish-trees?_

Because their large flowers abound in a resinous, sometimes acrid, and
highly poisonous juice, which afterwards turns black, and is used for
varnishing in India. One kind is the common cashew nut. All these
varnishes are extremely dangerous to some constitutions; the skin, if
rubbed with them, inflames, and becomes covered with pimples that are
difficult to heal; the fumes have also been known to produce painful
swelling and inflammation.

_Why do these varnishes, at first white, afterwards turn black?_

Because the recent juice is an organized substance, consisting of an
immense congeries of small parts, which disperse the sun's rays in all
directions, like a thin film of unmelted tallow; while the varnish which
has been exposed to the air loses its organized structure, becomes
homogeneous, and then transmits the sun's rays, of a rich, deep, uniform,
red colour.

The leaves of some species of Schinus are so filled with a resinous fluid,
that the least degree of unusual repletion of the tissue causes it to be
discharged; thus, some of them fill the air with fragrance after rain; and
other kinds expel their resin with such violence when immersed in water,
as to have the appearance of spontaneous motion, in consequence of the
recoil. Another kind is said to cause swellings in those who sleep under
its shade.--_Brewster's Journal._