Ordinary Electricity 7

rather than an arrangement) but I am anxious to avoid stating
unnecessarily what will occur to others at the moment.

II. Ordinary Electricity

20. By ordinary electricity I understand that which can be
obtained from the common machine, or from the atmosphere,
or by pressure, or cleavage of crystals, or by a multitude of
other operations; its distinctive character being that of great
intensity, and the exertion of attractive and repulsive powers,
not merely at sensible but at considerable distances.

21. Tension. — The attractions and repulsions at sensible
distances, caused by ordinary electricity, are well known to be
so powerful in certain cases, as to surpass, almost infinitely,
the similar phenomena produced by electricity, otherwise
excited. But still those attractions and repulsions are exactly
of the same nature as those already referred to under the head
Tension, Voltaic electricity (4); and the difference in degree
between them is not greater than often occurs between cases
of ordinary electricity only. I think it will be unnecessary to
enter minutely into the proofs of the identity of this character
in the two instances. They are abundant; are generally
admitted as good; and lie upon the surface of the subject:
and whenever in other parts of the comparison I am about to
draw, a similar case occurs, I shall content myself with a mere
announcement of the similarity, enlarging only upon those
parts where the great question of distinction or identity still
exists.

22. The discharge of common electricity through heated air
is a well-known fact. The parallel case of voltaic electricity
has already been described (8, etc.).

23. In motion: i. Evolution of heat.—The heating power of
common electricity, when passed through wires or other sub-
stances, is perfectly well known. The accordance between it
and voltaic electricity is in this respect complete. Mr. Harris
has constructed and described1 a very beautiful and sensible
instrument on this principle, in which the heat produced in a
wire by the discharge of a small portion of common electricity
is readily shown, and to which I shall have occasion to refer
for experimental proof in a future part of this paper (So).

24. ii. Magnetism.—Voltaic electricity has most extraordinary

1 Philosophical Transactions, 1827, p. 18. Edinburgh Transactions, 1821.
Harris on a New Electrometer, etc., etc '-' Hiii