both. From all which it appears that kindred electricities repel, and
opposite attract, each other.

Two pieces of gold leaf suspended from a metal rod, inserted at the top
of a glass shade full of perfectly pure, dry air, will separate if we
rub our foot on the carpet, and touch the top of the rod with one of our
fingers; for the motion of the body, as in walking, always excites
electricity, and it is this which, as it passes through the finger,
causes the phenomenon; though the least sensation of damp in the glass
would, by instantly draining off the electricity, defeat the experiment.
What happens in this case is, that one kind of electricity passes from
the finger to the leaves, while another kind, to make room for it,
passes from the leaf to the finger; and the leaves separate because they
are both more or less charged with the same kind of electricity, and
kindred electricities repel each other. Ribbons, particularly of white
silk, when well washed, are similarly susceptible of electrical
excitation; and they behave very much as the gold leaf does when they
are rubbed sharply through a piece of flannel. Gutta-percha is another
substance which, when similarly treated, is similarly affected.

This power is a very mysterious one, and of a nature to perplex even the
philosophic observer. Certain bodies, such as the metals, convey it, and
are called conductors; certain others, such as glass and porcelain,
arrest it, and are called insulators. It is for this reason that the
wires of the telegraph are supported by a non-conductor, for if not, the
electric current would pass into the earth by the first post and never
reach its final destination. Glass being an insulator, it was found
that, if a glass bottle was filled with water, and then corked up with a
cork, through which a nail was passed so that the top of it touched the
water, it would receive and retain a charge as long as it was held in