Cathode , Lenard, and Rontgen Rays. 279 



like so sudden as that which Thomson has to contemplate for 

 his charges : this of course only makes a difference in the 

 degree of intensity of the phenomena resulting from the 

 stoppage. There has as yet been no systematic proof that 

 the properties of a train of impulses would be the same as 

 those of the Rontgen rays in the matter of the absence of 

 refraction and reflexion. Again, it is recognized that the 

 Rontgen rays and the Becquerel rays from uranium are very 

 similar, but it would be hard to imagine the Becquerel rays 

 to be due to thin impulses. On these grounds it seems to 

 me that Thomson's suggestion as to the cause of the Rontgen 

 rays, although exciting one's admiration by its clear con- 

 sistency, does not lead to the desired end ; and therefore I 

 will try to follow out the premisses of this paper to such 

 conclusions as may relate to phenomena like those of the 

 Rontgen rays. 



To the electrons we have assigned inertia and size, and we 

 must therefore ascribe to them shape ; but a general con- 

 ception of shape involves also the notion of deformability, 

 which, therefore, we must consider as a possible property of 

 the electron. The electron is therefore to be supposed 

 capable of emitting vibrations due to the relative motions of 

 its parts ; as light is supposed to be due to the motion of 

 electrons as wholes, we see that the internal vibrations 

 of electrons will have this much in common with light, that 

 they are transmitted by the same sether, but they need have 

 nothing else in common. We propose, then, to identify the 

 Rontgen rays with these internal vibrations of our electrons. 

 It might be expected that the electron, in executing the 

 motions which cause light, would get strained and thrown 

 into internal vibration, so that Rontgen rays would accom- 

 pany ordinary light ; but the fact that Rontgen rays cannot 

 be detected in association with light shows that the motion 

 of the electron occurs either so that it is very free from shock 

 and strain, or so that atoms promptly damp any internal 

 vibrations of adjacent electrons. The way in which matter 

 absorbs the energy of Rontgen rays shows that we may rely 

 on atoms to suppress any small amount of Rontgen radiation 

 that might tend to accompany ordinary light as emitted by 

 electrons. Thus, then, appreciable Rontgen radiation is to be 

 looked for only when free electrons are thrown into vigorous 

 internal vibration. Now the encounter of an electron with 

 an atom, in which it gives up a part of its kinetic energy to 

 the atom as heat, is precisely the sort of action by which we 

 should expect the electron to be thrown into internal vibration. 

 Internal vibrations should originate where cathode or Lenard 



