eing seen through.

_Resinous_, containing resin, a gummy vegetable juice.

Name a few substances possessing this remarkable property.

Silks of all kinds; the hair and fur of animals, paper, sulphur, and
some other minerals; most of the precious stones; the paste of which
false gems are made; and many other substances used by us in the
common affairs of life, are susceptible of electrical excitement;
among domestic animals the cat furnishes a remarkable instance. When
dry and warm, the back of almost any full-grown cat (the darker its
color the better) can be excited by rubbing it with the hand in the
direction of the hair, a process which is accompanied with a slight
snapping noise, and in the dark by flashes of pale blue light. When a
piece of glass is rubbed with silk, or a stick of red sealing-wax with
woollen cloth, each substance acquires the property of attracting and
repelling feathers, straws, threads of cotton, and other light
substances; the substances just mentioned as highly electric are,
however, merely specimens. All objects, without exception, most
probably are capable of being electrically excited; but some require
more complicated contrivances to produce it than others.

_Electric_, having the properties of electricity.

_Susceptible_, disposed to admit easily.

_Repelling_, the act of driving back.

_Complicated_, formed by the union of several parts in one.

Is there not a machine by which we are enabled to obtain large
supplies of electric power at pleasure?

Yes; the electrical machine. It is made of different forms and sizes:
for common purposes those of the simplest form are the best. A common
form of the machine consists of a circular plate of glass, which can
be turned about a horizontal axis by means of a suitable handle. This
plate turns between two supports, and near its upper and lower edges
are two pairs of cushions, usually made of leather, stuffed with
horse-hair and coated with a mixture of zinc, tin, and mercury, called
an _amalgam_. These cushions are the rubbers for producing friction,
and are connected with the earth by means of a metal chain or rod. Two
large hollow cylinders of brass with globular ends, each supported by
two glass pillars, constitute the reservoir for receiving the
electricity. They are called the _prime conductors_, and are supplied
with U-shaped rods of metal, furnished with points along their sides,
called _combs_, for th