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.