Cathode, Lenard, and Rontgen Rays. 283 



plana tion of this fundamental fact. The theory of vibrating 

 electrons requires that, in addition to the fundamental mode 

 of vibration, we must contemplate a number of harmonics 

 associated with it ; various combinations of fundamental and 

 harmonics will be associated with different conditions of 

 generation of the vibrations, and these will correspond to the 

 Rontgen rays of different penetrative power. 



An interesting observation of Swinton's, that two colliding 

 cathode streams do not give rise to Rontgen rays, is explained 

 by our hypothesis, because the electrons are so small and so 

 far apart that an appreciable number of collisions between 

 the electrons of two colliding streams cannot occur. 



Some consequences of our line of reasoning, to which as 

 yet no corresponding experimental results have been obtained, 

 may now be indicated. The difference between cathode and 

 anode is due to the fact that the attraction of metallic atoms 

 for positive electrons is stronger than for negative ones, so 

 that under a given electrical stress negative electrons break 

 away as a cathode stream more easily than positive ones as 

 an anode stream. But still, under strong enough electric 

 stress at the anode, it ought to be possible to get an anode 

 stream or anode rays similar to the cathode rays, but carry- 

 ing positive electricity. These on encountering atoms, espe- 

 cially the atoms of a solid body, should cause the emission of 

 rays similar to the Rontgen, but possibly very different in 

 detailed properties, such as wave-length. It is possible that 

 the Becquerel rays may be examples of what we may call 

 positive Rontgen rays, because, while we have seen that, in 

 the majority of cases, electrons move relatively to atoms in 

 the production of light, in such a manner that they do not 

 experience shocks throwing them into internal vibration, the 

 uranium atom may be so formed that it periodically collides 

 with its satellite electron or electrons, in which case the atoms 

 of uranium would be a source of radiation analogous to the 

 Rontgen. 



According to our theory the velocity of the cathode stream 

 is not a physical constant like the velocity of light through 

 the aether, but ought to vary greatly according to the history 

 of the stream, which starts with zero velocity and ends with 

 the same. The velocity of the Rontgen rays should be of 

 the order of that of light : we cannot assert that it should be 

 exactly equal to that of light, because to waves of so short a 

 length the neutrons may act as if they loaded the aether, so 

 that Rontgen rays may suffer a refraction in aether in com- 

 parison with light. The fact that the experimental velocities 

 found for the cathode rays are of the order of the velocity of 



