Prof. Norton on Molecular Physics. 105 



pressing action about n is but the result of the repulsive energy 

 of the free electricity which has determined the polarization. 



The outer circle in the figure represents the surface of the 

 undisturbed atmosphere (inner envelope). When the molecule 

 becomes polarized, the surface of its atmosphere takes, or tends 

 to take, the spheroidal form, with the centre of figure lying on 

 the side negatively polarized. At points near this surface, about 

 midway between p and n, and indefinitely beyond the surface, 

 there will be a resultant force, as shown in the figure, tending 

 to check the flow of free electricity around or past the molecule, 

 in the direction of n toward p. 



It does not follow, because the lines of direction of the attrac- 

 tion and repulsion meet at s under a small angle, that the result- 

 ant s t may not be equal to, or greater than, the force of tension 

 of the free electricity that may reach the molecule, since the 

 absolute intensities of these forces must be very great. Besides, 

 whatever may be the intensity of this resultant, it must be of a 

 corresponding order of magnitude with the tension of free elec- 

 tricity, since it is precisely the resistance exerted by the polarized 

 molecules of air contiguous to an electrized surface that deter- 

 mines the tension of the statical electricity collected upon it. 



When a discharge takes place through an imperfect conductor, 

 as rarefied air, the contiguous particles of air are first polarized 

 by the repulsion of the electrized surface propagated by the uni- 

 versal aether. This determines the escaping electricity to fall 

 upon their nearer negative sides ; the molecular resistance con- 

 sidered above then comes into play ; and if the elastic tension of 

 the electricity is sufficient to overcome this resistance, a conduct- 

 ing discharge takes place ; otherwise the electric movement can 

 only be after the manner explained on p. 101 — that is, as in the 

 process of induction. According to these views, the greater 

 resistance offered by dense than rarefied air is to be explained by 

 the smaller number of resisting particles encountered in the latter, 

 together with the diminished resistance of each particle. For it will 

 be evident, on referring to fig. 7, that if the molecular atmosphere 

 expands, as it will if the air be rarefied, the resistance at s will 

 be diminished. Thus air rarefied to a certain degree should 

 become a conductor of electricity. For a similar reason the sur- 

 faces of solid or liquid bodies should conduct electricity better 

 than the internal portions, since the molecular atmospheres are 

 more expanded there*. It will also be observed, in view of the 

 results obtained, that imperfect conduction and non-conduction 

 depend upon certain effects resulting from the polarization of 



* Surfaces of non-conductors resist the flow of free electricity after the 

 same manner as the internal mass; that is, by their molecules becoming 

 polarized. 



