﻿428 
  Mr. 
  E. 
  Cunningham 
  on 
  the 
  Principle 
  of 
  Relativity. 
  

  

  motion, 
  a 
  conclusion 
  scarcely 
  consonant 
  with 
  a 
  principle 
  of 
  

   relativity. 
  

  

  If 
  we 
  revert 
  to 
  the 
  ordinary 
  theory 
  as 
  applied 
  to 
  the 
  same 
  

   illustration, 
  the 
  field 
  due 
  to 
  one 
  electron 
  in 
  the 
  neighbourhood 
  

   of 
  the 
  other 
  consists 
  of 
  an 
  electric 
  intensity 
  

  

  (>-?) 
  

  

  a/2 
  

  

  o/i 
  u 
  • 
  2 
  V 
  

   in 
  the 
  direction 
  of 
  r, 
  and 
  a 
  magnetic 
  intensity 
  

   qu 
  sin 
  0(l-^2 
  ) 
  

  

  vr 
  

  

  (l-jj«ia» 
  7 
  ) 
  

  

  at 
  right 
  angles 
  to 
  r 
  and 
  to 
  u. 
  

  

  Combining 
  these, 
  the 
  mechanical 
  force 
  on 
  the 
  second 
  

   electron 
  is 
  made 
  up 
  of 
  a 
  component 
  

  

  g»coB*(l-g) 
  

  

  3/2 
  

  

  in 
  the 
  direction 
  of 
  motion, 
  and 
  a 
  component 
  

  

  (l-JsinV) 
  

  

  3,2 
  

  

  perpendicular 
  to 
  this 
  direction. 
  

  

  Thus, 
  the 
  only 
  theory 
  which 
  would 
  give 
  an 
  acceleration 
  in 
  

   the 
  direction 
  of 
  r 
  is 
  one 
  in 
  which 
  the 
  ratio 
  of 
  the 
  transverse 
  

  

  to 
  the 
  longitudinal 
  mass 
  is 
  (1 
  — 
  j 
  as 
  in 
  the 
  Lorentz 
  theory. 
  

  

  Taking 
  the 
  Abraham 
  values 
  of 
  the 
  masses 
  the 
  line 
  joining 
  the 
  

   electrons 
  will 
  rotate 
  as 
  before. 
  

  

  