Interaction between Radiation and Electrons. 1065 



The equations used by Jeans were originally derived with 

 reference to the motion of a charged particle, the mass being 

 that of the particle, the electrical inertia of the charge being- 

 negligible. In applying the equations to the electron, the 

 material mass of the particle is dispensed with and the 

 electrical inertia of the charge substituted. 



If, instead of dealing only with mathematical equations, we 

 picture the charge as consisting of radiating Faraday lines 

 which extend indefinitely through the aether — and which 

 presumably are states of the aether itself, — this picture at once 

 suggests the question whether the radiation acts directly on 

 the lines, the centre or body moving as a result of motion 

 first imparted to the lines, or whether, on the other hand, 

 the motive force is applied directly on the centre or body of 

 the electron and the lines are dragged after it. In the 

 theory of the effect of an acceleration applied to a charged 

 body as causing emission of radiation, it is always conceived 

 that the force is applied to the body and the lines of the 

 charge dragged after it. When there is no material " body/' 

 it may still be the case that that is the mode of application 

 of an acceleration to a negative electron when the force is 

 the attraction of a positive, which is conceived as a tension 

 along the length of some of the lines. It is rather to be 

 expected, however, that when one negative electron acts on 

 another, by radiation, the case will be substantially different, 

 and the action may be directly on the lines of the receiving 

 electron. The centre may then move in conformity with the 

 motion already imparted to the lines, and it may be quite 

 inadmissible to infer that acceleration of the centre so 

 produced would result in the emission of radiation in the 

 manner in which emission would result if the acceleration 

 of the centre has been produced by a force acting directly on 

 that centre. 



It may be objected that the radiation, on first approaching 

 the electron, must reach the centre at least before it has 

 reached the lines which extend in the direction away from 

 that in which the emitting electron lies. 



In reply it may be pointed out that the first arrival of the 

 front of a wave of radiation is a very brief moment. 

 Actually, in all experimental work, we have to deal with a 

 long train of radiation, and the question what exactly 

 happens just at the moment of the arrival of the first wave 

 is relatively unimportant. The receiving electron is very 

 soon surrounded on all sides equally by aether affected by the 

 radiation, and it is suggested that, for a free electron, the 

 receipt of radiation is the converse of the emission. In the 



