366 GREAT MEN OF SCIENCE 



certainly say that electric lines of force have striking simi- 

 larity with vortex filaments or threads, and magnetic forces 

 with lines of flow in liquids or gases - which gives a useful 

 basis for considering many problems; but no material body 

 can be described which would behave exactly as the ether of 

 electro-magnetic fields of force, and of light. It has thus 

 become clear that ether and matter are things very difi^erent 

 from one another. The first does not consist of the atoms 

 known since Dalton's time; the laws of mechanics, which 

 are all derived from the observation of matter, cannot be 

 applied to the ether at all, or at least only to a limited degree. 

 The ether is not a mechanism of a material nature, but has 

 peculiar properties which go beyond those given by our 

 experience with matter, and can only be studied in con- 

 nection with the ether itself.^ 



After Hertz's time, new information concerning the 

 electro-magnetic field arrived when the investigation of 

 cathode rays, begun by Hittorf and Crookes, led us to the 

 knowledge that electro-magnetic fields also exist in the 

 interior of the atoms of matter; and the question arises 

 whether these fields also behave in accordance with 

 Maxwell's equations. This question must be answered in 

 the negative, since we have obtained knowledge of the 

 quantum-like behaviour of the atoms, which goes back to 

 Boltzmann. The ether inside the atoms does not however 

 appear to behave entirely differently from that outside 



^ In this connection, Tyndall's description of his impression of Fara- 

 day's remarks concerning the behaviour of ether, as regards lines of force, 

 is very remarkable. Tyndall says that Faraday often used peculiar, and 

 sometimes obscure, turns of speech, to describe this behaviour, as though 

 he were not in a position to make use of expressions which would be intel- 

 ligible to anyone with a knowledge of mechanics (Tyndall, Faraday as a 

 Discoverer, London, 1807, page 88). Tyndall would surely be able to say 

 to-day that Faraday's remarks were the more correct, since the mechanical 

 mode of expression, which he did not use, could not be suitable for ex- 

 pressing reality. It was simply the materialistic preconception, which is 

 still not yet completely eradicated, which prevented Faraday's point of 

 view, in spite of its correctness, from being followed. 



