given is generally very
great. Water is that body in which this acquired power is feeblest. In the
various oxides, chlorides, salts, &c. &c., it is given in a much higher
degree. I have not had time to measure the conducting power in these cases,
but it is apparently some hundred times that of pure water. The increased
conducting power known to be given to water by the addition of salts, would
seem to be in a great degree dependent upon the high conducting power of
these bodies when in the liquid state, that state being given them for the
time, not by heat but solution in the water[A].

[A] See a doubt on this point at 1356.--_Dec. 1838._

411. Whether the conducting power of these liquefied bodies is a
consequence of their decomposition or not (413.), or whether the two
actions of conduction and decomposition are essentially connected or not,
would introduce no difference affecting the probable accuracy of the
preceding statement.

412. This _general assumption of conducting power_ by bodies as soon as
they pass from the solid to the liquid state, offers a new and
extraordinary character, the existence of which, as far as I know, has not
before been suspected; and it seems importantly connected with some
properties and relations of the particles of matter which I may now briefly
point out.

413. In almost all the instances, as yet observed, which are governed by
this law, the substances experimented with have been those which were not
only compound bodies, but such as contain elements known to arrange
themselves at the opposite poles; and were also such as could be
_decomposed_ by the electrical current. When conduction took place,
decomposition occurred; when decomposition ceased, conduction ceased also;
and it becomes a fair and an important question, Whether the conduction
itself may not, wherever the law holds good, be a consequence not merely of
the capability, but of the act of decomposition? And that question may be
accompanied by another, namely, Whether solidification does not prevent
conduction, merely by chaining the particles to their places, under the
influence of aggregation, and preventing their final separation in the
manner necessary for decomposition?

414. But, on the other hand, there is one substance (and others may occur),
the _per-iodide of mercury_, which, being experimented with like the others
(400.), was found to insulate when solid, and to acquire conducting power
when fluid; yet it