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  XXXVIII. 
  Radiation 
  in 
  a 
  Magnetic 
  Field. 
  

   By 
  A. 
  A. 
  Michelson 
  *. 
  

  

  FURTHER 
  analysis 
  of 
  the 
  radiations 
  emitted 
  in 
  a 
  magnetic 
  

   field 
  shows 
  that 
  the 
  phenomenon 
  is 
  much 
  more 
  complex 
  

   than 
  was 
  supposed. 
  An 
  examination 
  of 
  the 
  separate 
  com- 
  

   ponents 
  of 
  the 
  " 
  triplet 
  " 
  brings 
  out 
  the 
  fact 
  that 
  in 
  general 
  

   these 
  are 
  multiple 
  lines. 
  

  

  The 
  laws 
  may 
  be 
  summarized 
  as 
  follows 
  : 
  — 
  

  

  A. 
  

  

  1. 
  All 
  spectral 
  lines 
  are 
  tripled 
  when 
  the 
  radiations 
  emanate 
  

   in 
  a 
  magnetic 
  field. 
  

  

  2. 
  The 
  separation 
  is 
  proportional 
  to 
  the 
  strength 
  of 
  field 
  

   and 
  is 
  approximately 
  the 
  same 
  for 
  all 
  colours 
  and 
  for 
  all 
  

   substances. 
  

  

  3. 
  Viewed 
  in 
  a 
  plane 
  perpendicular 
  to 
  the 
  magnetic 
  field, 
  

   the 
  outer 
  lines 
  are 
  polarized 
  parallel 
  to 
  the 
  field, 
  and 
  the 
  

   central 
  line 
  is 
  polarized 
  at 
  right 
  angles 
  with 
  the 
  field. 
  

  

  4. 
  Viewed 
  in 
  a 
  direction 
  parallel 
  with 
  the 
  magnetic 
  field, 
  

   the 
  central 
  line 
  vanishes, 
  while 
  the 
  outer 
  ones 
  are 
  circularly 
  

   polarized 
  ; 
  the 
  shorter 
  waves 
  in 
  the 
  direction 
  of 
  the 
  magne- 
  

   tizing 
  current, 
  the 
  longer 
  waves 
  in 
  the 
  opposite 
  sense. 
  

  

  To 
  these 
  laws 
  (which 
  were 
  verified 
  by 
  the 
  examination 
  of 
  a 
  

   dozen 
  or 
  more 
  lines) 
  the 
  following 
  must 
  now 
  be 
  added 
  : 
  — 
  

  

  B. 
  

  

  1. 
  The 
  " 
  middle 
  line 
  " 
  is 
  a 
  symmetrical 
  triple, 
  the 
  distance 
  

   between 
  the 
  components 
  being 
  one-fourth 
  that 
  of 
  the 
  " 
  outer 
  

   lines/' 
  and 
  hence 
  also 
  proportional 
  to 
  the 
  strength 
  of 
  field. 
  

  

  2. 
  The 
  relative 
  intensity 
  of 
  the 
  components 
  varies 
  for 
  dif- 
  

   ferent 
  substances 
  and 
  for 
  different 
  lines 
  of 
  the 
  same 
  substance 
  ; 
  

   and 
  accordingly 
  the 
  group 
  may 
  appear 
  as 
  a 
  single 
  line 
  or 
  a 
  

   double 
  or 
  a 
  triple. 
  

  

  3. 
  The 
  " 
  outer 
  lines" 
  are 
  unsym 
  metrical, 
  but 
  are 
  sym- 
  

   metrically 
  placed 
  with 
  respect 
  to 
  the 
  " 
  middle 
  Jine." 
  The 
  

   distance 
  between 
  the 
  components 
  is 
  usually 
  one-fourth 
  that 
  

   between 
  the 
  " 
  outer 
  lines/' 
  but 
  is 
  in 
  some 
  cases 
  one-sixth. 
  

  

  4. 
  The 
  intensity 
  of 
  the 
  components 
  varies 
  for 
  different 
  

   spectral 
  lines, 
  and 
  these 
  variations 
  do 
  not 
  always 
  correspond 
  

   to 
  those 
  of 
  the 
  " 
  central 
  line." 
  The 
  outer 
  groups 
  may 
  accor- 
  

   dingly 
  appear 
  as 
  single 
  or 
  double 
  or 
  triple 
  or 
  multiple 
  lines. 
  

  

  Fig. 
  1 
  represents 
  a 
  plan 
  of 
  the 
  arrangement 
  of 
  apparatus 
  

   * 
  Communicated 
  by 
  the 
  Author. 
  

  

  