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LXIV. On a Theory of the Electric Discharge in Gases. By 

 J. J. Thomson, M.A., Fellow of Trinity College, Cambridge*. 



THE aim of the following article is to give an account of 

 a theory which seems to explain some of the more pro- 

 minent phenomena of the electric discharge in gases, and 

 which also indicates the presence in the electric field of 

 stresses consisting of tension along the lines of force combined 

 with pressures at right angles to them. Maxwell, as is well 

 known, showed that stresses of this character would explain 

 the mechanical actions between electrified bodies. 



I shall take the vortex-atom theory of gases as the basis of 

 the following remarks, as it possesses for this purpose advan- 

 tages over the ordinary solid-particle theory; though much 

 of the reasoning will hold whichever theory of gases be as- 

 sumed. As the vortex-atom theory of gases is not very gene- 

 rally known, I shall begin by quoting the more important 

 consequences of this theory which are required in this article. 

 According to this theory, the atoms of gases consist of ap- 

 proximately circular vortex rings. When two vortex rings 

 of equal strength, with (as we shall suppose for simplicity) 

 their planes approximately parallel to each other and approxi- 

 mately perpendicular to the line joining their centres, are 

 moving in the same direction, and the circumstances are 

 such that the hinder ring overtakes the one in front, then if, 

 when it overtakes it, the shortest distance between the circular 

 axes of the rings be small compared with the radius of either 

 ring, the rings will not separate, the shortest distance between 

 their circular axes will remain approximately constant, and 

 these circular axes will rotate round another circle midway 

 between them, while this circle moves forward with a velocity 

 of translation which is small compared with the linear velocity 

 of the vortex rings round it. We can prove that in this case 

 the product of the momentum and velocity of the rings is 

 greater than the sum of the products of the same quantities 

 for the rings when they were separated by a distance great 

 compared with the radius of either. We may suppose that 

 the union or pairing in this way of two vortex rings of dif- 

 ferent kinds is what takes place when two elements of which 

 these vortex rings are atoms combine chemically; while, if the 

 vortex rings are of the same kind, this process is what occurs 

 when the atoms combine to form molecules. If two vortex 

 rings paired 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 

 * Communicated by the Author. 



