322 Lord Kelvin on the Motions of Ether 



successive collisions. We may indeed suppose it to be more 

 frequently the immediate result of a collision than the wilder 

 vibration described in § 15, which, however, must undoubtedly 

 be an occasional, though probably a rare, condition immediately 

 after a collision. 



§ 17. We are not bound to assume that a single electrion is 

 the saturating quantum of any particular ponderable atom : 

 nor are we bound to suppose that it is electrically neutralized 

 by any integral number of electrions*: The most general 

 supposition we can make is that, with j electrions to each 

 atom, the atom and electrions act externally as a vitreously 

 electrified body, and, with j-{- 1 electrions, the atom and 

 electrions act as a resinously electrified body. 



§ 18. It seems to me indeed exceedingly probable that the 

 persistence of the two-atom molecule in the common diatomic 

 gases, 2 , N 2 , H 2 , Cl 2 , is due to the impossibility of electrically 

 neutralizing the ponderable atom by any integral number of 

 electrions. Suppose for example that one electrion suffices 

 to electrically neutralize two atoms of Nitrogen. A monatomic 

 Nitrogen gas (N), if non -electrified as a whole, would have 

 half of its atoms without electrions, and therefore vitreously 

 electric, with electric quantity equal and opposite to half that 

 of a single electrion. Each of the other half of its whole 

 number of atoms would have one electrion within it, and 

 therefore its external action would be resinous, with half the 

 potency of a single electrion. Thus there would be a strong 

 electric attraction between the atoms destitute of electrions 

 and the atoms each containing one electrion, within it. This 

 attraction would tend to bring the atoms together in pairs, N 2 , 

 each pair containing one electrion, of which one position of 

 equilibrium would be at the middle of the line joining the 

 centres of the two ponderable atoms. In seems quite probable 

 that this is the real condition of ponderable atoms and elec- 

 trions, in the ordinary diatomic gases. 



§ 19. The dissociation of a considerable number of such pairs 

 of atoms would be exactly the " ionization " by which, following 

 Schuster's and J. J. Thomson's theory of the conduction of 

 electricity through gases, the latest developed theories of radio- 

 activity explain the specially induced electric conductivity of 

 diatomic gases, such as Lenard found to be produced in air by 

 ultra-violet light traversing it, and Becquerel found in air all 

 round an apparently inert piece of metallic Uranium, or a 

 Uranium salt. 



§ 20. But, to give electric conductivity to a monatomic gas, 



* "Aepinus Atomized," §§ 5, 6; Baltimore Lectures, Appendix E. 



