TENDENCIES OF MODERN PHYSICS 41 



cated as to destroy its value. In the last century the 

 idea was revived by Lord Kelvin in his celebrated 

 vortical theory of matter. He used only the main ideas 

 of Descartes, and, from a better mathematical knowl- 

 edge of the properties of vortices, was able to sim- 

 plify their character and to account for many of the 

 attributes of matter. We may then say that the dis- 

 similarity in the two theories consists in the doctrine 

 that empty space is a vacuum or an imaginary entity 

 called the ether, as opposed to the postulate of Des- 

 cartes that space is true material substance ; while both 

 theories suppose that the smallest particles of sensible 

 matter are indivisible, the atomistic school considers 

 them to be atoms, inherently indivisible and essen- 

 tially different from space, but Descartes declared 

 them to be variations of a substance, itself infinitely 

 divisible, although they might not be further divisible 

 by our present experimental ability. With this under- 

 standing of Descartes's hypothesis, we are in a posi- 

 tion to show how closely modern views of matter and 

 electricity are concurring in this idea. 



From the large number of physicists now writing on 

 the theory of physics, three names stand out promi- 

 nently as originators of the modern conceptions of 

 electricity and matter. Professor H. A. Lorentz, Sir 

 Joseph Larmor, and Sir Joseph Thomson are certainly 

 the men who will be most prominently associated with 

 this movement; others have aided, but mainly in the ex- 



