Mass, Energy, and Radiation. 683 



participate in the motion of A had the means of comparing 

 the mass of an electron in his. region with that of one in A, 

 he would find that the ratio depended on the velocity of 

 translation of A. 



Following the ideas suggested by these illustrations we 

 get what I think is a consistent scheme for visualizing 

 physical processes, if we assume the existence : — 



1. Of particles all of the same kind and with the same 

 mass. These particles all move with the velocity of light. 

 Since the mass particles are moving with the velocity of 

 light they would on the Lorenztian transformation have this 

 velocity whatever might be the axes to which their motion 

 was referred. Any force on a particle due either to other 

 particles or to the electric field is always at right angles to 

 the direction of motion of the particle. Thus, though a 

 particle may be deflected its velocity remains unaltered. 



The mass of one of these particles must, as we shall see, 

 he exceedingly small compared with that of an electron. 



All mass, whether of electrons or atoms or radiant energy, 

 arises from the presence of these particles, and inasmuch 

 as each particle possesses an invariable amount of energy, 

 wherever there is mass there is an amount of energy pro- 

 portional to it. 



The distribution of these particles and their movement 

 from one place to another is determined by the, distribution 

 of the lines of electric force. For we assume that in addition 

 to the mass particles we have in the universe : 



2. Lines of electric force spreading through space. These 

 lines may be closed or they may begin or end at definite 

 points. These points are the seats of what we call electrical 

 charges, the electron being at one end of a line of force and 

 a unit of positive electricity at the other. Each electron 

 and each unit of positive electricity forms the end of an 

 invariable number of lines of electric force. The connexion 

 between the distribution of the mass particles and the lines 



"o£ force is given by the rule that the mass per unit volume 

 at any point P is proportional to 



which is also proportional to the energy per unit volume. 

 /, g, It are the number of lines of force passing through a 

 unit area at P at right angles to the axes of x, y, z respectively, 

 a, /3, 7 are the components of the magnetic force, c is the 

 velocity of light through a vacuum. 



2 Y2 



