ELECTRIC THEORY OF MATTER 303 



Fifteen years ago the theory of matter as we 

 find it to-day might have been ruled out of 

 court. But the work of Professor Larmor at 

 Cambridge and of Lorenz at Leyden made it 

 quite clear that the radiation from the atom could 

 be accounted for by the rotation of negative electrons 

 round the atom and that the atom itself is made up of 

 electrons ; whilst that of Zeeman tended to confirm 

 the view that the mass of these electrons is much 

 smaller than that of the atom. There were many 

 reasons as well for supposing that cathode rays 

 are also of this nature, since it was known from 

 the researches of Lenard that they could penetrate 

 thin sheets of metal, and that their magnetic deflec- 

 tion is independent of the gas in the tube which 

 they traversed ; whilst their absorption by matter is 

 directly proportional to the density. The more acute 

 thinkers already perceived that electrons were on the 

 horizon. Some workers were already engaged in 

 determining the ratio of the charge carried by the 

 cathode ray to its mass. Almost simultaneously 

 J. J. Thomson in England and Kauffmann in 

 Germany published independently within a few 

 days similar results, which seemed to identify 

 the cathode rays with electrons. The latter, 

 indeed, has since shown that the mass depends 

 upon the velocity and is thus a variable quantity. 

 Thomson, on the other hand, has identified the 

 charge on the cathode rays with that of the 

 electron, or unit charge of electricity. His deter- 

 minations were those of the charge carried by the 



