343. _Tension_.--The attractions and repulsions due to the tension of
ordinary electricity have been well observed with that evolved by
magneto-electric induction. M. Pixii, by using an apparatus, clever in its
construction and powerful in its action[A], was able to obtain great
divergence of the gold leaves of an electrometer[B].
[A] Annales de Chimie, l. p. 322.
[B] Ibid. li. p 77.
344. _In motion_: i. _Evolution of Heat._--The current produced by
magneto-electric induction can heat a wire in the manner of ordinary
electricity. At the British Association of Science at Oxford, in June of
the present year, I had the pleasure, in conjunction with Mr. Harris,
Professor Daniell, Mr. Duncan, and others, of making an experiment, for
which the great magnet in the museum, Mr. Harris's new electrometer (287.),
and the magneto-electric coil described in my first paper (34.), were put
in requisition. The latter had been modified in the manner I have elsewhere
described[A] so as to produce an electric spark when its contact with the
magnet was made or broken. The terminations of the spiral, adjusted so as
to have their contact with each other broken when the spark was to pass,
were connected with the wire in the electrometer, and it was found that
each time the magnetic contact was made and broken, expansion of the air
within the instrument occurred, indicating an increase, at the moment, of
the temperature of the wire.
[A] Phil, Mag. and Annals, 1832, vol. xi. p. 405.
315. ii. _Magnetism._--These currents were discovered by their magnetic
power.
346. iii. _Chemical decomposition._--I have made many endeavours to effect
chemical decomposition by magneto-electricity, but unavailingly. In July
last I received an anonymous letter (which has since been published[A],)
describing a magneto-electric apparatus, by which the decomposition of
water was effected. As the term "guarded points" is used, I suppose the
apparatus to have been Wollaston's (327. &c.), in which case the results
did not indicate polar electro-chemical decomposition. Signor Botto has
recently published certain results which he has obtained[B]; but they are,
as at present described, inconclusive. The apparatus he used was apparently
that of Dr. Wollaston, which gives only fallacious indications (327. &c.).
As magneto-electricity can produce sparks, it would be able to show the
effects proper to this apparatus. The apparatus of M. Pixii already
referred to (343.) has however, in the hands of himself[C] and M.
Hachctte[D], given decisive chemical results, so as to complete this link
in the chain of evidence. Water was decomposed by it, and the oxygen and
hydrogen obtained in separate tubes according to the law governing
volta-electric and machine-electric decomposition.
[A] Lond. and Edinb. Phil. Mag. and Journ., 1832, vol. i. p. 161.
[B] Ibid. 1832. vol. i. p. 441.
[C] Annales de Chimie, li, p. 77.
[D] Ibid. li. p. 72
347. iv. _Physiological effects._--A frog was convulsed in the earliest
experiments on these currents (56.). The sensation upon the tongue, and the
flash before the eyes, which I at first obtained only in a feeble degree
(56.), have been since exalted by more powerful apparatus, so as to become
even disagreeable.
348. v. _Spark._--The feeble spark which I first obtained with these
currents (32.), has been varied and strengthened by Signori Nobili and
Antinori, and others, so as to leave no doubt as to its identity with the
common electric spark.
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