Recent Theories of Electricity. 215 



and external attracting force are all finite, attains an infinite 

 momentum and kinetic energy. We are compelled to say 

 that the velocity of light is unattainable by matter, because 

 the aether is then impenetrable or that the electromagnetic 

 mass becomes infinite. 



All these theories and experiments are based on the 



experimental fact that — has been found to be 1*865 x 10 7 

 m 



approximately. It is then assumed that e is a constant and 



equal to the charge on the hydrogen electrolytic ion ; with 



this value, the mass m is about the one-thousandth part of the 



mechanical mass of the hydrogen atom. How can we 



account for this mass when the theorists claim that the 



mechanical mass is entirely electromagnetic ? We know 



what the transverse electromagnetic mass is from Abraham's 



formula ; it is equal to m" '= 3 where v is a constant 



velocity of changeable direction. Substituting we obtain 

 the formula already given, 



This mass m' is evidently not the denominator of the 



,. e 

 ratio, — . 

 m 



To say that e is a constant is an assumption based solely on 



an analogy to the experimental laws of electrolysis ; but in 



electrolysis, when we obtain equal electric charges we also 



find equivalent masses of matter. In the discharge of 



electricity through gases and in radioactivity the matter 



deposited is too small to be measured. This is a fundamental 



difference, and vitiates an analogy between the two. For 



example, we measure the amount of current in a vacuum 



tube by an electrical device, and at the same time we 



measure the deflexion of the current by an electric and 



magnetic field ; in other words, all quantities and forces are 



electrical, and we say that equal currents in this case require 



equivalent quantities of matter. But it has not been shown 



to be impossible or even improbable that electrons, associated 



with equal quantities of matter but having different velocities, 



might show different electrical charges ; or that electrons 



producing equal electrical charges, might deposit different 



amounts of matter if it were sufficient in quantity to be 



detected by chemical or mechanical reactions. Thus we may 



imagine the following experiment : — Suppose all conditions 



ill a vacuum tube to remain the same, except that the velocity 



