ty 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
the hand; and this observation led to an invention of some account in
the subsequent applications of electricity, known, from the place of its
conception, as the Leyden jar. This is a glass jar, the inside of which
is coated with tinfoil, and the outside as far as the neck, and into
which, so as to touch the inside coating, a brass rod with a knob at
the top is inserted through a cork, which closes its mouth. By means of
this, in consequence of the isolation of the coatings by the glass,
electricity can, in a dry atmosphere, be condensed, and stored up and
husbanded till wanted.

A series of eggs, arranged in contact and in line, give occasion to a
pretty experiment. In consequence of the shells being non-conductors,
and the inside conducting, it happens that a current of electricity,
applied to the first of the series, will pass from one to another in a
succession of crackling sparks, in this way forcing itself through the
obstructing walls. This effect of electricity in making its way through
non-conducting obstructions accounts for the explosion which ensues when
a current of it comes in contact with a quantity of gunpowder; as it
also does for the fatal consequence