481.  Grotthuss, in the year 1805, wrote expressly on the decomposition of liquids by voltaic electricity[A].  He considers the pile as an electric magnet, i.e. as an attractive and repulsive agent; the poles having attractive and repelling powers.  The pole from whence resinous electricity issues attracts hydrogen and repels oxygen, whilst that from which vitreous electricity proceeds attracts oxygen and repels hydrogen; so that each of the elements of a particle of water, for instance, is subject to an attractive and a repulsive force, acting in contrary directions, the centres of action of which are reciprocally opposed.  The action of each force in relation to a molecule of water situated in the course of the electric current is in the inverse ratio of the square of the distance at which it is exerted, thus giving (it is stated) for such a molecule a constant force[B].  He explains the appearance of the elements at a distance from each other by referring to a succession of decompositions and recompositions occurring amongst the intervening particles[C], and he thinks it probable that those which are about to separate at the poles unite to the two electricities there, and in consequence become gases[D].

  [A] Annales de Chimie, 1806, tom, lviii. p. 64.

  [B] Ibid. pp. 66, 67, also tom. lxiii. p. 20.

  [C] Ibid. tom. lviii. p. 68, tom, lxiii. p. 20.

  [D] Ibid. tom. lxiii. p. 34.

482.  Sir Humphry Davy’s celebrated Bakerian Lecture on some chemical agencies of electricity was read in November 1806, and is almost entirely occupied in the consideration of electro-chemical decompositions.  The facts are of the utmost value, and, with the general points established, are universally known.  The mode of action by which the effects take place is stated very generally, so generally, indeed, that probably a dozen precise schemes of electro-chemical action might be drawn up, differing essentially from each other, yet all agreeing with the statement there given.

483.  When Sir Humphry Davy uses more particular expressions, he seems to refer the decomposing effects to the attractions of the poles.  This is the case in the “general expression of facts” given at pp. 28 and 29 of the Philosophical Transactions for 1807, also at p. 30.  Again at p. 160 of the Elements of Chemical Philosophy, he speaks of the great attracting powers of the surfaces of the poles.  He mentions the probability of a succession of decompositions and recompositions throughout the fluid,—­agreeing in that respect with Grotthuss[A]; and supposes that the attractive and repellent agencies may be communicated from the metallic surfaces throughout the whole of the menstruum[B], being communicated from one particle to another particle of the same kind[C], and diminishing in strength from the place of the poles to the middle point, which is necessarily neutral[D].  In reference to this diminution of power at increased distances from the poles, he states that in a circuit of ten inches of water, solution of sulphate of potassa placed four inches from the positive pole, did not decompose; whereas when only two inches from that pole, it did render up its elements[E].