“When two bodies repellent of each other act upon the same body with different degrees of the same electrical attracting energy, the combination would be determined by the degree; and the substance possessing the weakest energy would be repelled; and this principle would afford an expression of the causes of elective affinity and the decompositions produced in consequence.” “Or where the bodies having different degrees of the same energy, with regard to the third body, had likewise different energies with regard to each other, there might be such a balance of attractive and repellent powers as to produce a triple compound; and by the extension of this reasoning, complicated chemical union may be easily explained.” As the combined effect of many particles possessing a feeble electrical energy may be conceived equal or even superior to the effect of a few particles possessing a strong electrical energy, the same principle may explain the influence of mass action, as elucidated by Berthollet. He conceives also that it may be possible to obtain a _measure_ of chemical affinity founded upon the energy of the voltaic apparatus required to destroy the chemical equilibrium. He points out that, as light and heat are the common consequences of the restoration of the equilibrium between bodies in a high state of opposite electricities, so it is perhaps an additional circumstance in favour of his theory to state that heat and light are likewise the result of all intense chemical action. And as in certain forms of the voltaic battery when large quantities of electricity of low intensity act, heat is produced without light; so in slow combinations there is an increase of temperature without luminous appearance. The effect of heat in producing combination may, he assumes, be also explained according to these ideas. It not only gives more freedom of motion to the particles, but in a number of cases--_e.g._ tourmaline, sulphur, etc.--it seems to exalt the electrical energies of bodies. In the eighth section he seeks to apply these principles to the mode of action of the voltaic pile, and to explain the nature of the changes which occur between the plates and the exciting fluid, and he points out that the theory in some measure reconciles the hypothetical principles of the action of the pile adopted by its inventor with the opinions concerning the chemical origin of galvanism held by the majority of British men of science at that period. At the same time, Davy argues that the facts are in contradiction to the assumption that chemical changes are the _primary_ causes of the phenomena of galvanism. Moreover, in mere cases of chemical change--as in iron burning in oxygen, the deflagration of nitre with charcoal, the combination of potash with sulphuric acid, the amalgamation of zinc,--electricity is never exhibited.