mind
as to the identity of the electricity of the torpedo with common and
voltaic electricity; and I presume that so little will remain on the minds
of others as to justify my refraining from entering at length into the
philosophical proofs of that identity. The doubts raised by Sir H. Davy
have been removed by his brother Dr. Davy; the results of the latter being
the reverse of those of the former. At present the sum of evidence is as
follows:--

[A] Philosophical Transactions, 1773, p. 461.

[B] Ibid. 1775, p. 1.

[C] Ibid. 1776, p. 196.

[D] Ibid. 1829, p. 15.

[E] Ibid. 1832, p. 259.

352. _Tension._--No sensible attractions or repulsions due to tension have
been observed.

353. _In motion_: i. Evolution of Heat; not yet observed; I have little or
no doubt that Harris's electrometer would show it (287. 359.).

354. ii. _Magnetism._--Perfectly distinct. According to Dr. Davy[A], the
current deflected the needle and made magnets under the same law, as to
direction, which governs currents of ordinary and voltaic electricity.

[A] Philosophical Transactions, 1832, p. 260.

355. iii. _Chemical decomposition._--Also distinct; and though Dr. Davy
used an apparatus of similar construction with that of Dr. Wollaston
(327.), still no error in the present case is involved, for the
decompositions were polar, and in their nature truly electro-chemical. By
the direction of the magnet it was found that the under surface of the fish
was negative, and the upper positive; and in the chemical decompositions,
silver and lead were precipitated on the wire connected with the under
surface, and not on the other; and when these wires were either steel or
silver, in solution of common salt, gas (hydrogen?) rose from the negative
wire, but none from the positive.

356. Another reason for the decomposition being electrochemical is, that a
Wollaston's apparatus constructed with _wires_, coated by sealing-wax,
would most probably not have decomposed water, even in its own peculiar
way, unless the electricity had risen high enough in intensity to produce
sparks in some part of the circuit; whereas the torpedo was not able to
produce sensible sparks. A third reason is, that the purer the water in
Wollaston's apparatus, the more abundant is the decomposition; and I have
found that a machine and wire points which succeeded perfectly well with
distilled water, failed altogether when the water was rendered a good
conductor b