﻿656 
  Prof. 
  S. 
  B. 
  McLaren 
  on 
  a 
  

  

  destroyed 
  or 
  created. 
  The 
  one 
  state 
  excludes 
  the 
  other, 
  and 
  

   at 
  the 
  frontiers 
  of 
  the 
  regions 
  occupied 
  by 
  matter 
  and 
  aether 
  

   the 
  fluid 
  passes 
  from 
  one 
  state 
  to 
  the 
  other. 
  When 
  matter 
  

   is 
  regarded 
  as 
  a 
  sink 
  it 
  is 
  understood 
  that 
  the 
  momentum 
  

   of 
  the 
  substance 
  removed 
  at 
  any 
  point 
  is 
  added 
  to 
  that 
  which 
  

   remains. 
  

  

  The 
  whole 
  body 
  of 
  formulae 
  used 
  will 
  be 
  strictly 
  deduced 
  

   from 
  the 
  principle 
  of 
  least 
  action 
  

  

  S^Ldvdsdt 
  = 
  (50) 
  

  

  L 
  =W-%i) 
  + 
  h^-^- 
  v 
  - 
  ■ 
  ■ 
  (51) 
  

  

  V 
  here 
  denotes 
  potential 
  energy. 
  I 
  shall 
  have 
  more 
  to 
  say 
  

   of 
  it 
  later. 
  

  

  The 
  quantities 
  E 
  and 
  H 
  are 
  connected 
  by 
  the 
  relations 
  

  

  DivE 
  = 
  0, 
  ^=CurlH 
  (52) 
  

  

  as 
  

  

  These 
  are 
  to 
  be 
  treated 
  as 
  " 
  geometrical 
  restraints/' 
  H 
  and 
  

   E 
  exist 
  only 
  in 
  " 
  aether/' 
  The 
  equation 
  of 
  continuity 
  requires 
  

   as 
  in 
  last 
  section 
  

  

  B(dvdse^ 
  mT 
  '\ 
  = 
  0, 
  (53) 
  

  

  where 
  m 
  is 
  zero 
  in 
  aether 
  and 
  a 
  constant 
  different 
  from 
  zero 
  

   in 
  matter. 
  Thus 
  so 
  long 
  as 
  the 
  time 
  t 
  is 
  not 
  varied 
  

  

  B(dvds) 
  = 
  0. 
  . 
  .... 
  . 
  (54) 
  

  

  In 
  applying 
  (50) 
  let 
  E 
  and 
  H 
  first 
  be 
  varied 
  leaving 
  

   undisturbed 
  the 
  boundaries 
  of 
  matter 
  and 
  aether 
  and 
  their 
  

   motion. 
  

  

  Then 
  (50) 
  and 
  (51) 
  give 
  

  

  WL-l&m)dvdsdT=0, 
  . 
  . 
  (55) 
  

   under 
  the 
  conditions 
  that 
  

  

  DivSE 
  = 
  and 
  ^8E 
  = 
  CurloH. 
  . 
  . 
  . 
  (56) 
  

  

  Further, 
  the 
  equation 
  

  

  ^=CurlH 
  

  

  as 
  

  

  shows 
  that 
  

  

  where 
  dS 
  is 
  an 
  element 
  of 
  area 
  of 
  any 
  closed 
  material 
  

  

  