428 Mr. J. Larmor on the Molecular 



volved in this discussion to find that, notwithstanding the 

 large factors occurring in the calculation, such as the ratio of 

 the electrostatic and electro-magnetic units, it yet agrees so 

 closely in order of magnitude with the result 1 x 10" 10 metre, 

 obtained by Helmholtz from actual measurement of the polari- 

 zation capacity of platinum plates. 



5. But, on the principles we have been following, w r e may 

 carry the analysis of the phenomenon still further. The 

 polarization consists in the transfer of charged particles to- 

 wards the electrode under the action of the electromotive 

 force, and they are finally brought to equilibrium at a distance 

 from the electrode, whose order of magnitude has just been 

 determined. As these equally charged particles repel one 

 another, they w r ill tend to settle down in equidistant positions 

 along the electrode surface. Instead therefore of two elec- 

 trified sheets analogous to an ordinary condenser, we have 

 really two sheets, one consisting of equidistant electrified par- 

 ticles, and the other of the charges brought opposite to them 

 on the electrode by induction. Each charged particle and its 

 corresponding induced charge will be brought by their mutual 

 attraction so close together that this attraction will just be 

 balanced by the chemical forces which hold them apart. 



For polarizations of sufficiently small amount, the sidelong 

 action of the neighbouring particles will be so small as to 

 have no appreciable effect on the distance of any one particle 

 from the electrode surface ; because, in the first place, the 

 distances of neighbouring particles must be at first large com- 

 pared with the distance of two opposed charges, and, in the 

 second place, the smaller forces exerted by these neighbouring 

 particles must be resolved along the normal to the surface, in 

 which direction they have no appreciable component. The 

 radii of curvature of the surfaces are of course extremely 

 great compared with the distance between opposed charges. 



It follows that as the polarization is increased the number 

 of charged particles over unit area of electrode increases in 

 the same proportion, and these particles all come to rest at 

 the same distance from the electrode surface, whatever be the 

 amount of the polarization. And we can clearly expect this 

 uniformity of distance to hold good until the neighbouring 

 particles come within a distance of one another which is of the 

 same order as the distance of a pair of the opposed charges. 



The pair of opposed surfaces which is thus arrived at, not 

 uniformly charged, but each with a system of equal isolated 

 point-charges arranged uniformly all over it, does not, of 

 course, act as an ordinary condenser in the sense of pro- 

 ducing a constant fall of potential in crossing it at all points, 

 in positions whose distances from it are of the same order as 



