JAMES CLERK MAXWELL 



1831-1879 



Clerk Maxwell summed up our whole knowledge of the 

 ether as far as it went in his time, and further made so 

 fortunate a use of knowledge then existing only in the form of 

 general indications, that a well finished structure resulted, 

 which - as experience later showed - really corresponds in a 

 very wide degree to the facts. This structure has a mathe- 

 matical form; it consists of certain equations, which state 

 quantitative connections between the states of the ether in 

 space, measurable in the form of electrical and magnetic 

 forces, and the constants representing the properties of the 

 matter likewise present in space. ^ 



Along with these appears, as a constant of the ether, the 

 velocity of light. The equations are differential equations; 

 that is to say, they relate only to a volume element of space 

 and to its immediate neighbourhood, and also only to ele- 

 ments of time. This entirely corresponds to Faraday's idea, 

 derived from all his experience, that it is not forces at a dis- 

 tance - which leap over all volume elements - that are active 

 in the ether, but that everything occurring in it acts only 

 from point to point. ^ Altogether, Maxwell founded his 

 equations entirely upon Faraday's conceptions. He 

 summarised in them everything fundamentally known 

 concerning light, electricity and magnetism, that is to say, 

 all that taken together, constituted the knowledge of ether at 

 that time. The fact that he was able to include the pheno- 

 mena of light, which had been since Huygens' time the 

 starting point of the physics of the ether, although only 



1 These material constants are: (i) the dielectric constant or specific 

 inductive capacity introduced by Faraday; (2) a constant analogous to 

 the latter, but referring to the magnetic force - the magnetic permea- 

 bility; (3) the electric conductivity. 



2 Wilhelm Weber likewise cairied out a magnificent summary, but one 

 founded on the assumption of action at a distance; facts later showed that 

 it did not correspond with reality. 



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