﻿252 
  Profs. 
  Wood 
  and 
  Kirmira 
  on 
  the 
  

  

  The 
  separation 
  of 
  the 
  components 
  of 
  the 
  doublets 
  excited 
  

   by 
  the 
  5790*7 
  line 
  varied 
  in 
  an 
  irregular 
  manner 
  from 
  2*1 
  

   to 
  5' 
  6 
  AU. 
  In 
  the 
  case 
  of 
  the 
  excitation 
  by 
  the 
  5769*6 
  line 
  

   we 
  have 
  also 
  a 
  series 
  of 
  doublets, 
  though 
  the 
  companion 
  line 
  

   is 
  missing 
  at 
  the 
  zero 
  order, 
  in 
  other 
  words 
  the 
  R.R. 
  line 
  

   has 
  no 
  companion. 
  The 
  separation 
  of 
  the 
  components 
  of 
  the 
  

   doublets 
  is 
  less 
  irregular 
  in 
  this 
  case, 
  varying 
  from 
  4*8 
  to 
  

   5*4 
  AU. 
  The 
  table 
  of 
  wave-lengths 
  will 
  be 
  given 
  in 
  th* 
  

   communication 
  following 
  this 
  one. 
  

  

  XXVIII. 
  The 
  Series 
  Law 
  of 
  Resonance 
  Spectra. 
  By 
  Prof. 
  It. 
  

   W. 
  Wood, 
  Johns 
  Hopkins 
  University, 
  and 
  Prof. 
  M. 
  Kimura, 
  

  

  University 
  of 
  Kyoto*. 
  

  

  IN 
  the 
  previous 
  communication 
  a 
  general 
  account 
  of 
  the 
  

   results 
  which 
  have 
  been 
  obtained, 
  up 
  to 
  the 
  present 
  time,, 
  

   on 
  the 
  resonance 
  spectra 
  of 
  iodine 
  has 
  been 
  given. 
  

  

  The 
  present 
  paper 
  will 
  deal 
  with 
  the 
  measurements 
  of 
  

   wave-length 
  of 
  the 
  lines 
  in 
  the 
  groups, 
  and 
  the 
  subject 
  of 
  the 
  

   series 
  law 
  which 
  governs 
  their 
  spacing. 
  

  

  The 
  wave-lengths 
  in 
  the 
  lines 
  in 
  the 
  groups 
  of 
  and 
  +1 
  

   order 
  were 
  determined 
  from 
  plates 
  made 
  in 
  the 
  fourth 
  order 
  

   spectrum 
  of 
  a 
  large 
  plane 
  grating 
  with 
  a 
  telescope 
  of 
  3 
  metres 
  

   focus. 
  They 
  are 
  correct 
  probably 
  to 
  0*01 
  AU. 
  The 
  groups 
  

   -f-2, 
  H-3, 
  and 
  4 
  4 
  were 
  made 
  in 
  the 
  second 
  order 
  spectrum, 
  

   and 
  the 
  higher 
  order 
  groups 
  in 
  the 
  first 
  order 
  spectrum. 
  

  

  The 
  series 
  which 
  has 
  been 
  most 
  definitely 
  determined, 
  and 
  

   to 
  which 
  the 
  greatest 
  amount 
  of 
  study 
  has 
  been 
  given, 
  is 
  

   the 
  series 
  of 
  strong 
  doublets 
  excited 
  by 
  the 
  Cooper-Hewitt 
  

   lamp. 
  

  

  The 
  two 
  components 
  of 
  each 
  doublet 
  appear 
  to 
  be 
  of 
  equal 
  

   intensity, 
  although, 
  in 
  the 
  case 
  of 
  two 
  or 
  three, 
  a 
  different 
  

   ratio 
  appears 
  in 
  the 
  photograph 
  as 
  a 
  result 
  of 
  absorption. 
  It 
  

   was 
  found, 
  as 
  has 
  been 
  stated 
  in 
  earlier 
  papers, 
  that 
  the 
  first 
  

   order 
  group, 
  which 
  is 
  usually 
  recorded 
  with 
  the 
  component 
  

   of 
  shorter 
  wave-length 
  three 
  or 
  four 
  times 
  as 
  intense 
  as 
  the 
  

   other, 
  comes 
  out 
  with 
  its 
  lines 
  of 
  nearly 
  equal 
  intensity 
  if 
  

   the 
  lateral 
  branch 
  of 
  the 
  iodine 
  tube 
  is 
  cooled 
  to 
  zero, 
  while 
  

   the 
  right 
  hand 
  component 
  disappears 
  entirely 
  if 
  the 
  light 
  

   from 
  the 
  tube 
  is 
  passed 
  through 
  a 
  large 
  glass 
  bulb 
  containing 
  

   iodine 
  vapour 
  before 
  it 
  enters 
  the 
  spectroscope. 
  

  

  In 
  studying 
  the 
  series 
  law 
  it 
  has 
  been 
  found 
  necessary 
  to 
  

  

  * 
  Communicated 
  by 
  the 
  Authors. 
  

  

  