4 Larmor, Physical Aspect of the Atomic Theory. 



traneous dust or mist whirled in the wind. For an 

 adequately exact type of unifying conception of the 

 relation between matter and aether, of their structural 

 connexion, science had to wait until the middle of the 

 nineteenth century. The profound analysis of Helmholtz 

 had revealed the unexpectedly simple scope of the 

 principles determining the interactions of vortexes in 

 fluid — one of the most brilliant of the achievements of 

 mathematical reasoning, whose highest function must 

 always be to condense the unmanageable mass of 

 relevant particulars into the practicable limits of general 

 principles. His main result was that, in the entire 

 absence of friction in the fluid, each vortex ring would 

 be a permanent state of motion, capable of temporary 

 modification (distortion, vibration, etc.), through inter- 

 action across the fluid with other vortexes which come 

 within its range, but always in the end recovering its 

 original condition, and thus retaining its individuality 

 through unlimited time. We can well imagine the keen 

 interest excited by Lord Kelvin's rapid apercu that such 

 vortexes may represent in essential features the atoms 

 of matter. For here we have a type of atom that is not 

 something foreign to the aether, merely immersed in it 

 and pushed about by it, but a permanent located whirl 

 or stable state of motion which subsists in the aether 

 itself, and is of its very essence. 



Here was suggested a mode of unification of a duality 

 previously unresolvable ; and we can appreciate the zeal 

 with which the problem of the investigation of this vivid 

 image of one of the fundamental modes of inter- 

 connexion in the scheme of nature was attacked by 

 mathematical physicists. Its development, in which 

 alongside the name of Helmholtz that of Lord Kelvin 

 will ever stand, has constituted, as we all know in this 



