_may_ be consequent on the difference of
action of two interposed bodies which it would not show. As time enters as
an element into these actions[A] (125.), it is very possible that the
induced actions on the helices or cores A, B, though they rise to the same
degree when air and copper, or air and lac are contrasted as intervening
substances, do not do so in the same time; and yet, because of the length
of time occupied by a vibration of the needle, this difference may not be
visible, both effects rising to their maximum in periods so short as to
make no sensible portion of that required for a vibration of the needle,
and so exert no visible influence upon it.

[A] See Annnles de Chimie, 1833, tom. li. pp. 422, 428.

* * * * *

1731. If the lateral or transverse force of electrical currents, or what
appears to be the same thing, magnetic power, could be proved to be
influential at a distance independently of the intervening contiguous
particles, then, as it appears to me, a real distinction of a high and
important kind, would be established between the natures of these two
forces (1654. 1664.). I do not mean that the powers are independent of each
other and might be rendered separately active, on the contrary they are
probably essentially associated (1654.), but it by no means follows that
they are of the same nature. In common statical induction, in conduction,
and in electrolyzation, the forces at the opposite extremities of the
particles which coincide with the lines of action and have commonly been
distinguished by the term electric, are polar, and in the cases of
contiguous particles act only to insensible distances; whilst those which
are transverse to the direction of these lines, and are called magnetic,
are circumferential, act at a distance, and if not through the mediation of
the intervening particles, have their relations to ordinary matter entirely
unlike those of the electrical forces with which they are associated.

1732. To decide this question of the identity or distinction of the two
kinds of power, and establish their true relation, would be exceedingly
important. The question seems fully within the reach of experiment, and
offers a high reward to him who will attempt its settlement.

1733. I have already expressed a hope of finding an effect or condition
which shall be to statical electricity what magnetic force is to current
electricity (1658.). If I could have p