374.  When the platina wire was connected with the prime conductor of the machine, and the spatula with the discharging train, ten turns of the machine had such decomposing power as to produce a pale round spot of iodine of the diameter of the wire; twenty turns made a much darker mark, and thirty turns made a dark brown spot penetrating to the second thickness of the paper.  The difference in effect produced by two or three turns, more or less, could be distinguished with facility.

375.  The wire and spatula were then connected with the voltaic apparatus (369.), the galvanometer being also included in the arrangement; and, a stronger acid having been prepared, consisting of nitric acid and water, the voltaic apparatus was immersed so far as to give a permanent deflection of the needle to the 5-1/3 division (372.), the fourfold moistened paper intervening as before[A].  Then by shifting the end of the wire from place to place upon the test paper, the effect of the current for five, six, seven, or any number of the beats of the watch (369.) was observed, and compared with that of the machine.  After alternating and repeating the experiments of comparison many times, it was constantly found that this standard current of voltaic electricity, continued for eight beats of the watch, was equal, in chemical effect, to thirty turns of the machine; twenty-eight revolutions of the machine were sensibly too few.

  [A] Of course the heightened power of the voltaic battery was
  necessary to compensate for the bad conductor now interposed.

376.  Hence it results that both in magnetic deflection (371.) and in chemical force, the current of electricity of the standard voltaic battery for eight beats of the watch was equal to that of the machine evolved by thirty revolutions.

377.  It also follows that for this case of electro-chemical decomposition, and it is probable for all cases, that the chemical power, like the magnetic force (36.), is in direct proportion to the absolute quantity of electricity which passes.

378.  Hence arises still further confirmation, if any were required, of the identity of common and voltaic electricity, and that the differences of intensity and quantity are quite sufficient to account for what were supposed to be their distinctive qualities.

379.  The extension which the present investigations have enabled me to make of the facts and views constituting the theory of electro-chemical decomposition, will, with some other points of electrical doctrine, be almost immediately submitted to the Royal Society in another series of these Researches.

Royal Institution, 15th Dec. 1832.

Note.—­I am anxious, and am permitted, to add to this paper a correction of an error which I have attributed to M. Ampere the first series of these Experimental Researches.  In referring to his experiment on the induction of electrical currents (78.), I have called that a disc which I should have called a circle or a ring.  M. Ampere used a ring, or a very short cylinder made of a narrow plate of copper bent into a circle, and he tells me that by such an arrangement the motion is very readily obtained.  I have not doubted that M. Ampere obtained the motion he described; but merely mistook the kind of mobile conductor used, and so far I described his experiment erroneously.