﻿660 
  Prof. 
  S. 
  B. 
  McLaren 
  

  

  on 
  a 
  

  

  Using 
  (40) 
  in 
  (51) 
  we 
  are 
  to 
  find 
  the 
  condition 
  that 
  (50) 
  

   should 
  hold 
  

  

  WsW-sS'tis^^W 
  

  

  ( 
  

  

  Hence 
  we 
  have 
  

  

  1 
  CCCCfr-r 
  TV-,CW 
  dj 
  d 
  

  

  (^.H 
  2 
  - 
  8^ 
  E2 
  - 
  V 
  «+ 
  V^)Kdvds)±0'.. 
  (67) 
  

  

  The 
  values 
  of 
  V 
  a 
  and 
  V 
  m 
  may 
  not 
  be 
  continuous 
  at 
  the 
  

   surface. 
  

  

  Now 
  J 
  and 
  BJ 
  being 
  continuous 
  as 
  well 
  as 
  their 
  first 
  

   differentials, 
  (67) 
  can 
  be 
  written 
  by 
  partial 
  integration 
  

  

  But 
  (V- 
  ~^J^AirBm=0. 
  

  

  The 
  variation 
  8m 
  is 
  finite 
  — 
  from 
  zero 
  to 
  m 
  — 
  and 
  hmdvds 
  is 
  

   m§(dvds). 
  

  

  So 
  (68) 
  gives 
  finally 
  

  

  Hence 
  

  

  (J~ 
  H 
  2 
  - 
  ^ 
  E2 
  ~ 
  V 
  a 
  + 
  ^ 
  - 
  ™J) 
  WV 
  ds 
  = 
  0. 
  

  

  l-W-~W-V 
  a 
  +V 
  m 
  -mJ=0.. 
  . 
  . 
  (69) 
  

  

  57T 
  07T 
  

  

  (69) 
  used 
  in 
  (65) 
  and 
  (66) 
  shows 
  that 
  

  

  Pa 
  Pin 
  = 
  c 
  a 
  C 
  m- 
  

  

  Without 
  loss 
  of 
  generality 
  the 
  pressures 
  p 
  a 
  and 
  p 
  m 
  may 
  be 
  

   made 
  equal 
  and 
  c 
  a 
  equal 
  to 
  c 
  m 
  . 
  

  

  § 
  7. 
  Energy, 
  Momentum, 
  and 
  Stress. 
  

  

  Independently 
  of 
  Max 
  Abraham 
  (" 
  Sulla 
  Teoria 
  della 
  

   Gravitazione" 
  Atti 
  dellaR. 
  Ace. 
  del 
  Lincei),! 
  had 
  reached 
  (in 
  

   1911) 
  results 
  equivalent 
  to 
  his 
  lor 
  the 
  energy 
  and 
  momentum 
  

   of 
  the 
  gravitational 
  field. 
  Writing 
  after 
  Abraham 
  it 
  is 
  now 
  

   unnecessary 
  for 
  me 
  to 
  do 
  more 
  than 
  merely 
  to 
  state 
  the 
  most 
  

   important 
  formulae. 
  

  

  