114 Faraday's Researches

electrolytical will be understood at once: muriatic acid is electro-
lytical, boracic acid is not.

401. Finally, I require a term to express those bodies which
can pass to the electrodes, or, as they are usually called, the
poles. Substances are frequently spoken of as being electro-
negative, or electro-positive, according as they go under the
supposed influence of a direct attraction to the positive or nega-
tive pole. But these terms are much too significant for the
use to which I should have to put them; for though the mean-
ings are perhaps right, they are only hypothetical, and may be
wrong; and then, through a very imperceptible, but still very
dangerous, because continual, influence, they do great injury to
science, by contracting and limiting the habitual views of those
engaged in pursuing it. I propose to distinguish such bodies
by calling those anions ^ which go to the anode of the decom-
posing body; and those passing to the cathode, cations ; 2 and
when I have occasion to speak of these together, I shall call
them ions. Thus, the chloride of lead is an electrolyte, and when
electrolysed evolves, the two ions, chlorine and lead, the former
being an onion, and the latter a cation.

402. These terms being once well defined, will, I hope, in
their use enable me to avoid much periphrasis and ambiguity of
expression. I do not mean to press them into service more
frequently than will be required, for I am fully aware that names
are one thing and science another.3

403. It will be well understood that I am giving no opinion
respecting the nature of the electric current now, beyond what
I have done on former occasions (19, 253); and that though
I speak of the current as proceeding from the parts which are
positive to those which are negative (399), it is merely in accord-
ance with the conventional, though in some degree tacit, agree-
ment entered into by scientific men, that they may have a
constant, certain, and definite means of referring to the direction
of the forces of that current.

1 dvL&v that which goes up. (Neuter participle.)

- KOLTL<JL>V that which goes down.

3 Since this paper was read, I have changed some of the terms which
were first proposed, that I might employ only such as were at the same
time simple in their nature, clear in their reference, and free from
hypothesis. of electricity: it is analogous in its sense and sound