﻿658 
  Prof. 
  8. 
  B. 
  McLaren 
  on 
  a 
  

  

  (60) 
  gives 
  by 
  equating 
  to 
  zero 
  the 
  coefficient 
  of 
  Sco, 
  

  

  nH 
  = 
  0; 
  

  

  or 
  the 
  normal 
  component 
  of 
  H 
  is 
  zero. 
  The 
  same 
  condition 
  

   recurs 
  on 
  equating 
  to 
  zero 
  the 
  coefficient 
  of 
  the 
  normal 
  

   component 
  of 
  SA. 
  And 
  (60) 
  then 
  gives 
  that 
  the 
  tangential 
  

   components 
  of 
  

  

  E 
  + 
  c-^uH] 
  

  

  are 
  zero, 
  where 
  u 
  is 
  any 
  velocity 
  whose 
  component 
  normal 
  

   to 
  the 
  surface 
  is 
  the 
  same 
  as 
  the 
  normal 
  velocity 
  of 
  the 
  

   surface 
  itself. 
  The 
  conditions 
  thus 
  determined 
  are 
  just 
  those 
  

   which 
  hold 
  at 
  a 
  perfect 
  reflector. 
  

  

  In 
  assuming 
  (52) 
  as 
  the 
  conditions 
  under 
  which 
  the 
  

   Electromagnetic 
  Lagrangian 
  function 
  is 
  

  

  -L(H 
  2 
  -E 
  2 
  ) 
  

  

  we 
  are 
  following 
  Larmor 
  ('iEther 
  and 
  Matter 
  '). 
  This 
  

   procedure 
  makes 
  the 
  magnetic 
  energy 
  kinetic 
  in 
  ordinary 
  

   space. 
  

  

  I 
  now 
  deduce 
  the 
  equations 
  of 
  motion 
  in 
  matter 
  and 
  in 
  

   sether 
  by 
  variation. 
  I 
  shall 
  assume 
  that 
  the 
  variation 
  con- 
  

   sidered 
  begins 
  and 
  ends 
  either 
  in 
  matter 
  or 
  in 
  sether, 
  and 
  

   that 
  t 
  is 
  not 
  varied. 
  I 
  shall 
  distinguish 
  matter 
  and 
  sether 
  by 
  

   suffixes. 
  

  

  The 
  equations 
  of 
  motion 
  are 
  

  

  lr\ 
  dr 
  J 
  dsV 
  b7r 
  07r 
  / 
  

  

  dr 
  

  

  A 
  

  

  dr 
  

  

  (61) 
  

  

  Remembering 
  that 
  

  

  dr' 
  

   (61) 
  reduces 
  to 
  

  

  ^7 
  (dv 
  ds) 
  = 
  — 
  (Air) 
  *m 
  dv 
  ds 
  

  

  

  (62) 
  

  

  