﻿in 
  the 
  Magnetic 
  Field. 
  337 
  

  

  of 
  the 
  electromagnetic 
  theory. 
  Indeed 
  all 
  the 
  main 
  facts 
  

   were 
  sufficiently 
  accounted 
  for 
  by 
  Dr. 
  Zeeman 
  * 
  as 
  deductions 
  

   from 
  the 
  theory 
  of 
  Lorenz. 
  The 
  foregoing 
  measurements, 
  

   however, 
  when 
  taken 
  into 
  consideration 
  with 
  the 
  formula 
  

   deduced 
  theoretically 
  throw 
  important 
  light 
  on 
  the 
  quantities 
  

   involved 
  in 
  the 
  theoretical 
  calculation. 
  Thus 
  if 
  T 
  be 
  the 
  

   periodic 
  time 
  corresponding 
  to 
  any 
  spectral 
  line, 
  and 
  if 
  ST 
  be 
  

   the 
  difference 
  in 
  period 
  between 
  the 
  side 
  lines 
  of 
  a 
  triplet 
  

   produced 
  by 
  a 
  magnetic 
  field 
  of 
  strength 
  H, 
  then 
  the 
  formula 
  

   yielded 
  by 
  theory 
  is, 
  in 
  electromagnetic 
  units, 
  

  

  ST_ 
  eR_ 
  

  

  T 
  2 
  "2irm 
  J 
  

  

  where 
  e 
  is 
  the 
  ionic 
  charge 
  and 
  m 
  the 
  inertia. 
  Expressed 
  in 
  

   terms 
  of 
  the 
  wave-length 
  this 
  becomes 
  

  

  h\_e_ 
  JE 
  

  

  where 
  v 
  is 
  the 
  velocity 
  of 
  light. 
  

  

  Now 
  the 
  foregoing 
  measurements 
  show 
  that 
  8\ 
  does 
  not 
  

   vary 
  as 
  X 
  2 
  , 
  nor 
  apparently 
  according 
  to 
  any 
  simple 
  law, 
  so 
  

   that 
  at 
  present 
  the 
  ratio 
  of 
  e 
  to 
  m 
  has 
  to 
  be 
  determined 
  as 
  a 
  

   function 
  of 
  \ 
  for 
  each 
  substance, 
  and 
  accordingly 
  we 
  must 
  

   write 
  

  

  m 
  J 
  v 
  " 
  

  

  where 
  the 
  form 
  of 
  the 
  function 
  remains 
  to 
  be 
  determined. 
  

  

  It 
  is 
  possible, 
  however, 
  that 
  the 
  lines 
  of 
  any 
  one 
  substance 
  

   may 
  be 
  thrown 
  into 
  groups 
  for 
  each 
  of 
  which 
  B\ 
  varies 
  as 
  

   X 
  2 
  , 
  and 
  each 
  of 
  these 
  groups 
  might 
  be 
  produced 
  by 
  the 
  motion 
  

   of 
  a 
  single 
  ion. 
  The 
  number 
  of 
  such 
  groups 
  in 
  a 
  given 
  

   spectrum 
  would 
  then 
  determine 
  the 
  number 
  of 
  different 
  kinds 
  

   of 
  ions 
  in 
  the 
  atom 
  or 
  molecule. 
  

  

  Homologous 
  relations 
  may 
  also 
  exist 
  between 
  the 
  groups 
  

   in 
  different 
  spectra, 
  but 
  all 
  this 
  still 
  remains 
  for 
  complete 
  

   investigation. 
  

  

  Appendix. 
  

   The 
  following 
  extract 
  f 
  cannot 
  fail 
  to 
  be 
  of 
  considerable 
  

  

  * 
  Zeeman, 
  Phil. 
  Mag. 
  loc. 
  cit. 
  

  

  t 
  M. 
  Ch. 
  JFievez 
  (Astronome 
  a 
  l'Observatoire 
  Royal 
  de 
  Bruxelles), 
  

   Bulletins 
  de 
  VAcademie 
  Royale 
  de 
  Belgique, 
  3rd 
  se>ie, 
  tome 
  ix. 
  p. 
  381 
  

   (1885). 
  See 
  also 
  in 
  the 
  same 
  volume, 
  p. 
  327, 
  the 
  report 
  on 
  this 
  work 
  by 
  

   M. 
  Stas. 
  

  

  