Chemical Combination of Gases. 235 



two vortex-rings p Tired in the way we have described are 

 subjected to any disturbing influence, such as the action due 

 to other vortex-rings in their neighbourhood, their radii will 

 be changed by different amounts ; thus their velocities of 

 translation will become different and they w^ill separate. 

 We are thus led to take the view of chemical combination 

 put forward by Clausius and Williamson, according to which 

 the molecules of a compound gas are supposed not to always 

 consist of the same atoms of the elementary gases, but that 

 these atoms are continually changing partners. In order, 

 however, that the compound gas should be something more 

 than a mechanical mixture of the elementary gases of which 

 it is composed, it is evidently necessary that the mean 

 time during which an atom is paired with another of a dif- 

 ferent kind, which we shall call the paired time, should be 

 large compared with the time during which it is alone and 

 free from other atoms, which we shall call the free time. If 

 we suppose that the gas is subjected to any disturbance, then 

 this will have the effect of breaking up the molecules of the 

 compound gas sooner than would otherwise be the case. It 

 will thus diminish the ratio of the paired to the free time ; 

 and if the disturbance is great enough the value of this ratio 

 will be so much reduced that the substance will no longer 

 exhibit the properties of a chemical compound, but those of 

 its constituent elements. We should thus have the pheno- 

 menon of dissociation or decomposition It is 



clear, too, that the value of the ratio of the paired to the 

 free time for the atoms of an elementary gas will have a very 

 great effect on the chemical properties of the gas ; thus if 

 the ratio of the free to the paired times for the atoms of the 

 gas be very small the gas will not enter into combination 

 with other gases, for it will only do so to any great extent 

 when the ratio of the free to the paired time for the com- 

 pound is less than for the atoms in the^molecule of the ele- 

 mentary gas ; thus we should expect that this ratio would 

 be very small for the atoms of a gas like nitrogen, which 

 does not combine readily with other gases. The value of this 

 ratio would afford a very convenient measure for the affinity 

 of the constituents of a compound for each other. It is also 

 conceivable that this ratio might affect the physical properties 

 of a gas ; and in a paper in the ' Philosophical Magazine ' 

 for June 1883, I suggested that differences in the value of 

 this ratio might account for the differences in the electric 

 strength of gases. 



" Two vortex-rings will not remain long together unless the 

 shortest distance between the central lines of their vortex- 



R2 



