Animal Electricity 25

have little or no doubt that Harris's electrometer would show

ft (23*95)-

90. ii. Magnetism.—Perfectly distinct. According to Dr.

Davy/ the current deflected the needle and made magnets
under the same law, as to direction, which governs currents of
ordinary and voltaic electricity.

91. iii. Chemical decomposition.—Also distinct; and though
Dr. Davy used an apparatus of similar construction with that
of Dr. Wollaston (63), 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.

92. Another reason for the decomposition being electro-
chemical is, that a Wollaston's apparatus constructed with wires,
coated by sealing-wax, would most probably not have decom-
posed water, even in its own peculiar way, unless the elec-
tricity 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 by
sulphate of soda, common salt, or other saline bodies. But in
Dr. Davy's experiments with the torpedo, strong solutions of salt,
nitrate of silver, and superacetate of lead were used success-
fully, and there is no doubt with more success than weaker ones.

93. iv. Physiological effects.—These are so characteristic, that
by them the peculiar powers of the torpedo and gymnotus are
principally recognised.

94. v. Spark.—The electric spark has not yet been obtained,
or at least I think not; but perhaps I had better refer to the
evidence on this point. Humboldt, speaking of results obtained
by M. Fahlberg, of Sweden, says, " This philosopher has seen
an electric spark, as Walsh and Ingenhousz had done before
him at London, by placing the gymnotus in the air, and inter-
rupting the conducting chain by two gold leaves pasted upon

1 Philosophical Transactions, 1832, p. 260.r. Barry, communicating by a wire insertedole. The whole instrument was protected