﻿666 
  Prof. 
  S. 
  B. 
  McLaren 
  on 
  a 
  

  

  And 
  the 
  true 
  stresses 
  form 
  the 
  system 
  (83) 
  : 
  

  

  W 
  e 
  -~(W-W), 
  cM 
  m 
  cM 
  e3 
  , 
  cM 
  ez 
  , 
  

   cM 
  el 
  , 
  P 
  e 
  +i_(E 
  2 
  -H 
  2 
  ), 
  U 
  e 
  , 
  T 
  e 
  , 
  

  

  (83) 
  

  

  cM 
  ey 
  , 
  U 
  e 
  , 
  Q 
  e 
  +^-(W-W), 
  S, 
  

  

  Sit 
  

  

  v 
  

  

  cM 
  ez 
  , 
  T„ 
  S„ 
  R 
  e 
  +^(E'-W), 
  

  

  This 
  system 
  of 
  stresses 
  may 
  be 
  submitted 
  to 
  a 
  Lorentz- 
  

   Einstein 
  substitution. 
  The 
  simplest 
  results 
  are 
  obtained 
  

   when 
  we 
  so 
  transform 
  that 
  the 
  new 
  electric 
  and 
  magnetic 
  

   vectors 
  

  

  E 
  and 
  H 
  

  

  became 
  parallel, 
  as 
  with 
  Cunningham. 
  

  

  Then 
  [E 
  H 
  ]=Q, 
  

  

  and 
  the 
  three 
  components 
  of 
  momentum, 
  the 
  " 
  shears 
  " 
  

  

  cM 
  ex 
  , 
  cM 
  ey 
  , 
  cM 
  ez 
  , 
  

   in 
  (83) 
  all 
  vanish. 
  

  

  Next 
  take 
  the 
  ^-axis 
  in 
  the 
  direction 
  of 
  E 
  or 
  H 
  , 
  then 
  

   the 
  shears 
  m 
  TT 
  

  

  &e> 
  I 
  e, 
  U 
  e 
  

  

  vanish, 
  as 
  appears 
  from 
  (76). 
  There 
  are 
  left, 
  therefore, 
  only 
  

   the 
  principal 
  stresses 
  in 
  (83). 
  

  

  Using 
  again 
  the 
  values 
  in 
  (76), 
  we 
  have 
  

  

  a 
  pressure 
  (4tt) 
  -1 
  H 
  2 
  along 
  the 
  transformed 
  time-axis, 
  

  

  a 
  tension 
  (4tj-) 
  _1 
  H 
  2 
  along 
  the 
  direction 
  of 
  H 
  , 
  

  

  and 
  in 
  directions 
  perpendicular 
  to 
  E 
  a 
  pressure 
  (47r 
  -1 
  ) 
  E 
  2 
  . 
  

   The 
  values 
  of 
  E 
  and 
  H 
  are 
  easily 
  calculated, 
  

  

  E 
  2 
  ~H 
  2 
  =E 
  2 
  -H 
  2 
  ? 
  E 
  H 
  =EH. 
  

  

  For 
  the 
  difference 
  of 
  the 
  squares 
  of 
  E 
  and 
  H 
  and 
  their 
  scalar 
  

   product 
  are 
  invariant. 
  

  

  With 
  the 
  stress 
  system 
  of 
  (83) 
  it 
  appears 
  that 
  all 
  stresses 
  

   across 
  the 
  surface 
  of 
  matter 
  vanish. 
  For 
  this 
  surface 
  will 
  

   have 
  some 
  such 
  equation 
  as 
  

  

  f{xyzs) 
  = 
  0. 
  

  

  By 
  transforming 
  to 
  the 
  local 
  time 
  and 
  to 
  axes 
  moving 
  with 
  

  

  