22 . Stokes, on the Nature of the Rontgen Rays. 



moriiously together. But in the case of the Rontgen 

 rays, if the nature of them be what I have explained, 

 you have a constant succession of pulses independent 

 of one another. Consequently there is no chance to get 

 up harmony between the vibrations of the ether and the 

 vibrations of the body. 



Go back to the case of light passing through glass. 

 When the regular combined vibration is established you 

 have a kinetic energy, due partly to the motion of the 

 ether and partly to the motion of the molecules. If you 

 make abstraction of the loss of energy by reflection, the 

 rate at which the energy passes within the glass must 

 be the same as it has outside, and consequently there 

 must be the same energy for one wave length, which 

 corresponds to one period of the vibration, inside as 

 outside. But if the kinetic energy of the ether is the 

 same for the same volume inside and outside, and you 

 have in addition inside a certain amount of kinetic 

 energy due to the motion of the molecules, the two 

 taken together can only make the energy for a wave 

 inside the same as for a wave outside on the condition 

 that the velocity of propagation inside is less than the 

 velocity of propagation outside. That is the theory I 

 have been forced to adopt as to the nature of refraction 

 in consequence of the ideas I hold as to the nature 

 of the Rontgen rays ; and if you adopt that theory I 

 think everything falls into its place. When you have the 

 Rontgen rays falling on a body, the motion of the ether 

 due to them is interfered with by the molecules of the 

 body, more or less. No body is perfectly transparent to 

 these rays, and on the other hand perhaps we may say 

 no body is perfectly opaque. That all falls into its 

 place on this supposition as to the nature of the action 

 of the ether on the molecules. Now, why is it that 

 the Rontgen rays do not care whether you present them 



