480 Electrolytic Theory of Dielectrics. 



I am able to judge. With Method V., however, acceptance of 

 the formula seems to necessitate acceptance of initial charges ; 

 and this is still more the case with Methods I. and II., where 

 electrification is produced without the application of any- 

 apparent electrostatic field. 



So far, at any rate,, as the results of the table are concerned, 

 I think it will be admitted that the hypothesis of initial ionic 

 charges is the simplest and most consistent method of ex- 

 plaining them. Indeed, if it were not for the difficulties met 

 with in the consideration of elementary substances, and espe- 

 cially of metals, one would be almost tempted to imagine that 

 chemical affinity and ionic attraction were one and the same 

 thing. The difficulty, however, of accounting for opposite 

 charges in similar particles — the fact that the pairing ten- 

 dency is so small in metals that monatomic vapours are the 

 rule — the low compressibility of liquid mercury, which also 

 points to incomplete pairing — and especially the fact that 

 metals conduct without any apparent convection of their par- 

 ticles — all these points are clearly opposed to the idea that the 

 particles of metals are oppositely and permanently charged. 



It is true that the phenomena of thermo-electricity, like all 

 other cases where electricity is produced by apparently non- 

 electrical means, are likely to find an easy explanation if the 

 previous existence of electricity, as such, in the substance is 

 postulated. So, too, magnetic permeability might conceivably 

 be due to the spinning of permanently charged atoms. But 

 these are the only indications of internal charges in metals 

 that I know of, and they are very slight. 



On some grounds it almost seems as if the force of chemical 

 affinity in some way passes over into that of ionic attraction 

 either during, or after, or even just before the act of combina- 

 tion of unlike particles, while, from symmetry, it remains 

 unaltered in the case of like particles. The possible equality, 

 mentioned above, of the two forces, lends some colour to the 

 idea. There is, however, plenty to be said against it. If 

 more were known of the manner in which monatomic vapours 

 conduct, there would be a better chance of coming to a con- 

 clusion on this question. As it is, it must be left for the 

 present as a serious, but perhaps not insurmountable difficulty 

 from the point of view of this paper. 



One other point I may refer to. For convenience, the 

 word pairing has been used to indicate the combining 

 tendency of oppositely electrified particles, or, rather, the 

 reluctance of the two electricities to part company while the 

 substance expands and disintegrates under the action of heat. 

 Of course, it is not necessary that this process should be 



