308 Sir J. J. Thomson on a Theory of 



If the corpuscle is reduced to rest, the energy possessed by 

 it before it was stopped was equal to 



2-re 2 u 2 



a) era 



hence the fraction a/cr of the energy is radiated away. I 

 regard this radiation as constituting the Rontgen rays. I 

 gave a similar theory when the electric force was supposed 

 uniformly distributed round the corpuscle. In that case the 

 energy or the corpuscle is radiated in all directions, and is 

 diffused throughout a very large volume. In the theory just 

 given, however, the energy is not diffused but is concentrated 

 in a kink in a single tube of force. Thus when a number of 

 cathode particles bombard an anti-cathode the resulting 

 Rontgen radiation is concentrated into small patches which 

 possess momentum and energy, in fact we have a condition 

 of things much more closely represented in many respects by 

 the old emission theory of light than by the wave theory in 

 the form in which it is usually represented. A corpuscle 

 when it strikes the anti-cathode is not reduced to rest by the 

 first collision it makes with a molecule, but rebounds from 

 one molecule to another. The tube of force attached to it is 

 jerked spasmodically by the collisions and a series of small 

 discrete transverse pulses travel outwards along it with the 

 velocity of light ; the condition of the tube is very analogous 

 to that of a stretched string the end of which is spasmodically 

 jerked backwards and forwards. 



I pointed out several years ago that the properties of the 

 Rontgen rays, especially those concerned with the ionization 

 of gases through which they pass, suggested that the electric 

 and magnetic forces constituting these rays are not uniformly 

 distributed through space, but are concentrated in regions 

 whose volume is a very small fraction of the space through 

 which the rays are passing. 



If we suppose, as in the usual explanation of the forces in 

 the electric field by the tensions along the lines of force and 

 the pressures at right angles to them, that there is a repulsion 

 between tubes of force running in the same direction ; we 

 can see that the energy radiating out into space along tubes 

 of force may be communicated to charged bodies in the 

 region traversed by the tubes, and that when two pulses come 

 close together the energy in one may increase at the expense 

 of that in the other. 



The energy radiated resides, as we have seen, in the kink 

 in the tube of force produced by the stoppage of the corpuscle, 

 and remains constant as the kink travels outwards into space 



