d collected over our heads._ We set it
in motion, and obtain it _by heating_ different metals in connection, or
the same metal unequally; and from certain animals--like the torpedo and
the gymnotus--whose organization is such as to enable them to evolve it.
In all these cases, and they constitute an epitome of the principal
methods by which we obtain it in a distinct form, it is made to flow in
currents. When thus obtained, and imprisoned in non-conductors, it may be
discharged, and with somewhat different effect, as it is discharged in a
mass, disruptively, as it is called, as from the clouds in lightning, or
permitted to flow convectively, in currents, along the wires of a galvanic
apparatus, or in heated air, as from the earth to a cloud in the tornado.

It is, moreover, capable of division into positive and negative, and when
concentrated or disturbed in one body, it tends to create a similar
disturbance or division in a contiguous mass. To this action of
electricity, the term static induction is applied. Thus, a positively
electrified body _induces_ a division of the electricity in a contiguous
body, if both are insulated or surrounded by a non-conducting medium; the
negative electricity of the contiguous body being attracted by, and
tending to pass to, the positive of the adjoining body, and the positive
being repelled to the opposite side. That, in its turn, if sufficiently
powerful, tends to disturb the electricity of its neighbor, and attract
away its negative electricity; or, if the body which contains it is free
to move, to attract that. Thus, by the conflicting action of a positive
atmosphere, and a negative earth, and perhaps counter-trade, influenced by
magnetism and the solar rays, the currents and winds of the atmosphere are
produced, the atmosphere moving with exceeding ease and rapidity.
Electricity, excited into currents, or obtained and discharged in either
of the methods enumerated, is identical in character, and produces certain
well-known effects:

1st. Physiological.--Shocking and convulsing the animal system; producing
a peculiar sensation on the tongue, and a flash before the eyes, and in
sufficient quantity destroying life.

2d. Magnetic.--_Deflecting the needle_, and, by a suitable arrangement of
wire into helices, _conferring magnetic power_, or constituting magnets.

3d. Luminous.--Producing light--by a spark, as it does in natural
phenomena--by the glow, the brush discharge, the ball of