519. In this view the effect is considered as _essentially dependent_ upon the _mutual chemical affinity_ of the particles of opposite kinds. Particles _aa_, fig. 53, could not be transferred or travel from one pole N towards the other P, unless they found particles of the opposite kind _bb_, ready to pass in the contrary direction: for it is by virtue of their increased affinity for those particles, combined with their diminished affinity for such as are behind them in their course, that they are urged forward: and when any one particle _a_, fig. 54, arrives at the pole, it is excluded or set free, because the particle _b_ of the opposite kind, with which it was the moment before in combination, has, under the superinducing influence of the current, a greater attraction for the particle _a'_, which is before it in its course, than for the particle _a_, towards which its affinity has been weakened. 520. As far as regards any single compound particle, the case may be considered as analogous to one of ordinary decomposition, for in fig. 54, _a_ may be conceived to be expelled from the compound _ab_ by the superior attraction of _a'_ for _b_, that superior attraction belonging to it in consequence of the relative position of _a'b_ and _a_ to the direction of the axis of electric power (517.) superinduced by the current. But as all the compound particles in the course of the current, except those actually in contact with the poles, act conjointly, and consist of elementary particles, which, whilst they are in one direction expelling, are in the other being expelled, the case becomes more complicated, but not more difficult of comprehension. 521. It is not here assumed that the acting particles must be in a right line between the poles. The lines of action which may be supposed to represent the electric currents passing through a decomposing liquid, have in many experiments very irregular forms; and even in the simplest case of two wires or points immersed as poles in a drop or larger single portion of fluid, these lines must diverge rapidly from the poles; and the direction in which the chemical affinity between particles is most powerfully modified (519. 520.) will vary with the direction of these lines, according constantly with them. But even in reference to these lines or currents, it is not supposed that the particles which mutually affect each other must of necessity be parallel to them, but only that they shall accord generally with their direction. Two particles, placed in a line perpendicular to the electric current passing in any particular place, are not supposed to have their ordinary chemical relations towards each other affected; but as the line joining them is inclined one way to the current their mutual affinity is increased; as it is inclined in the other direction it is diminished; and the effect is a maximum, when that line is parallel to the current[A].