e sensibly behind the two former in time,
they being by the conditions of the experiment simultaneous. Hence a proof
of retardation; and what reason can be given why this retardation should
not be of the same kind as that in spermaceti, or in lac, or sulphur? But
as, in them, retardation is insulation, and insulation is induction, why
should we refuse the same relation to the same exhibitions of force in the
metals?

[A] Philosophical Transactions, 1834, p. 583.

1329. We learn from the experiment, that if _time_ be allowed the
retardation is gradually overcome; and the same thing obtains for the
spermaceti, the lac, and glass (1248.); give but time in proportion to the
retardation, and the latter is at last vanquished. But if that be the case,
and all the results are alike in kind, the only difference being in the
length of time, why should we refuse to metals the previous inductive
action, which is admitted to occur in the other bodies? The diminution of
_time_ is no negation of the action; nor is the lower degree of tension
requisite to cause the forces to traverse the metal, as compared to that
necessary in the cases of water, spermaceti, or lac. These differences
would only point to the conclusion, that in metals the particles under
induction can transfer their forces when at a lower degree of tension or
polarity, and with greater facility than in the instances of the other
bodies.

1330. Let us look at Mr. Wheatstone's beautiful experiment in another point
of view, If, leaving the arrangement at the middle and two ends of the long
copper wire unaltered, we remove the two intervening portions and replace
them by wires of iron or platina, we shall have a much greater retardation
of the middle spark than before. If, removing the iron, we were to
substitute for it only five or six feet of water in a cylinder of the same
diameter as the metal, we should have still greater retardation. If from
water we passed to spermaceti, either directly or by gradual steps through
other bodies, (even though we might vastly enlarge the bulk, for the
purpose of evading the occurrence of a spark elsewhere (1331.) than at the
three proper intervals,) we should have still greater retardation, until at
last we might arrive, by degrees so small as to be inseparable from each
other, at actual and permanent insulation. What, then, is to separate the
principle of these two extremes, perfect conduction and perfect insulation,
from each othe