The Discharge of Electricity through Gases. 559 



we may take them to be really only surface electrifications between tlie 

 atoms and the medium. 



I have offended in another manner against so-called modern views 

 of electricity, for I have spoken of positive and negative electricity 

 as real substances possessing a separate existence. I have tried to 

 place myself, however, under the shelter of recognised authority by 

 quoting at the top of this lecture Helmholtz's saying that we have as 

 much ground for the supposition that electricity has an atomic con- 

 stitution as we have for the atomic constitution of matter. We must 

 trust to the future to bring this view into harmony with the electro- 

 magnetic theory of light, which may be accepted now as an established 

 fact. There is no real antagonism between the two views. If ever we 

 are able to explain chemical and gravitational attraction by the 

 stresses in a medium, we shall still find it convenient to speak of 

 atoms and molecules ; and in the same way the belief in an electric 

 strain and stress is consistent with a belief in something in the atom 

 from which the strain proceeds, and which may be taken as the 

 elementary quantity of electricity. Even taking the extreme view 

 that electric stress is due to vortex filaments in the ether, we need 

 only assume all these filaments to have the same intensity, and some to 

 end at the surface of atoms, in order to reconcile apparently antago- 

 nistic views. But there is no need to commit ourselves at present to 

 any particular ideas. In some electric phenomena we shall find it 

 most convenient to speak of electric strain and stress (displacement I 

 think to be a misleading term, which, however, has come too much 

 into use to be dispensed with) ; in other, and at present more 

 numerous, cases, we shall still continue the old nomenclature, and 

 speak of positive and negative electricity as real quantities. The 

 subject of electro-chemistry is one of primary importance in the pre- 

 sent state of science. The different behaviour of positively and nega- 

 tively electrified particles points, as I have tried to explain, to an 

 unsymmetrical modification of molecular forces by electrification. It 

 is not sufficient to add geometrically the effects of molecular and elec- 

 trical action, but it is necessary to take account of the interference 

 between chemical and electrical forces. The exact nature of this 

 interference must partly be solved by chemical investigation, but the 

 discharges of electricity through gases still promise a rich harvest to 

 the investigator. 



Appendix. 



H The Discbarge of Electricity from Glowing Metals." By 

 Arthur Stanton, B.A. 



It has long been known that certain bodies undergoing chemical 

 decomposition are capable of discharging electricity through the 



