.

[A] Philosophical Transactions, 1807.

[B] Ibid. 1826, p. 383.

[C] Ibid. 1826, p. 389.

[D] I at one time intended to introduce here, in the form of a note, a
table of reference to the papers of the different philosophers who
have referred the origin of the electricity in the voltaic pile to
contact, or to chemical action, or to both; but on the publication of
the first volume of M. Becquerel's highly important and valuable
Traite de l'Electricite et du Magnetisme, I thought it far better to
refer to that work for these references, and the views held by the
authors quoted. See pages 86, 91, 104, 110, 112, 117, 118, 120, 151,
152, 224, 227, 228, 232, 233, 252, 255, 257, 258, 290, &c.--July 3rd,
1834.

P ii. _On the Intensity necessary for Electrolyzation._

966. It became requisite, for the comprehension of many of the conditions
attending voltaic action, to determine positively, if possible, whether
electrolytes could resist the action of an electric current when beneath a
certain intensity? whether the intensity at which the current ceased to act
would be the same for all bodies? and also whether the electrolytes thus
resisting decomposition would conduct the electric current as a metal does,
after they ceased to conduct as electrolytes, or would act as perfect
insulators?

967. It was evident from the experiments described (904. 906.) that
different bodies were decomposed with very different facilities, and
apparently that they required for their decomposition currents of different
intensities, resisting some, but giving way to others. But it was needful,
by very careful and express experiments, to determine whether a current
could really pass through, and yet not decompose an electrolyte (910.).

968. An arrangement (fig. 84.) was made, in which two glass vessels
contained the same dilute sulphuric acid, sp. gr. 1.25. The plate _z_ was
amalgamated zinc, in connexion, by a platina wire _a_, with the platina
plate _e_; _b_ was a platina wire connecting the two platina plates PP';
_c_ was a platina wire connected with the platina plate P". On the plate
_e_ was placed a piece of paper moistened in solution of iodide of
potassium: the wire _c_ was so curved that its end could be made to rest at
pleasure on this paper, and show, by the evolution of iodine there, whether
a current was passing; or, being placed in the dotted position, it formed a
direct communication with the platina