﻿Lines 
  in 
  the 
  Spectrum 
  of 
  IS 
  eon. 
  983 
  

  

  These 
  two 
  series 
  with 
  a 
  common 
  limit 
  at 
  X 
  4119-8 
  resemble 
  

   two 
  subordinate 
  series, 
  but 
  all 
  efforts 
  to 
  find 
  the 
  principal 
  

   which 
  might 
  be 
  expected 
  to 
  accompany 
  them 
  have 
  so 
  far 
  

   failed. 
  It 
  would 
  appear 
  that 
  they 
  do 
  not 
  correspond 
  to 
  any 
  

   of 
  the 
  helium 
  subordinate 
  series 
  ; 
  for 
  though 
  they 
  are 
  nearer 
  

   to 
  the 
  red 
  end 
  of 
  the 
  spectrum, 
  as 
  one 
  would 
  expect, 
  the 
  

   approximate 
  relation 
  between 
  the 
  separation 
  of 
  doublets 
  and 
  

   the 
  square 
  of 
  the 
  atomic 
  weights 
  does 
  not 
  hold. 
  

  

  For 
  the 
  search 
  of 
  the 
  principal 
  series 
  which 
  ought 
  

   eventually 
  to 
  accompany 
  the 
  series 
  of 
  doublets 
  it 
  was 
  

   thought 
  advisable 
  to 
  investigate 
  the 
  neon 
  spectrum 
  further 
  

   to 
  the 
  ultraviolet 
  than 
  had 
  hitherto 
  been 
  attempted. 
  For 
  

   this 
  purpose 
  a 
  quartz 
  " 
  end-on 
  " 
  spectrum-tube 
  filled 
  with 
  

   neon 
  at 
  about 
  4 
  mm. 
  pressure 
  was 
  used 
  as 
  source 
  of 
  light. 
  

   A 
  copper 
  arc 
  was 
  used 
  for 
  the 
  comparison 
  spectrum. 
  The 
  

   spectrograph 
  was 
  a 
  concave 
  grating 
  of 
  radius 
  1 
  metre, 
  the 
  

   dispersion 
  on 
  the 
  plate 
  being 
  16*8 
  A.U. 
  per 
  millimetre. 
  The 
  

   following 
  new 
  lines 
  were 
  obtained, 
  the 
  chief 
  impurities 
  

   being 
  hydrogen, 
  mercury 
  vapour, 
  and 
  carbon 
  monoxide, 
  and 
  

   traces 
  of 
  argon 
  and 
  krypton. 
  

  

  ave-lengths. 
  

   2352-0 
  

  

  Intensity 
  

  

  

  

  2396*5 
  

  

  2 
  

  

  2464-0 
  

  

  1 
  

  

  2639-9 
  

  

  1 
  

  

  2660-0 
  

  

  

  

  The 
  error 
  of 
  these 
  wave-lengths 
  probably 
  lies 
  within 
  

  

  •1A.U. 
  

  

  A 
  photograph 
  was 
  also 
  taken 
  with 
  a 
  jar 
  and 
  spark-gap 
  in 
  

   circuit, 
  but 
  as 
  in 
  the 
  less 
  refrangible 
  region 
  * 
  no 
  change 
  took 
  

   place 
  in 
  the 
  spectrum. 
  

  

  As 
  stated 
  before, 
  the 
  principal 
  series 
  of 
  neon 
  could 
  

   not 
  be 
  found, 
  but 
  a 
  series 
  of 
  a 
  few 
  ultraviolet 
  lines 
  was 
  

   isolated. 
  

  

  The 
  formula 
  is 
  

  

  1 
  =40929-1- 
  109675 
  

  

  (m 
  + 
  r00657) 
  2 
  ' 
  

   * 
  E. 
  C. 
  C. 
  Baly, 
  Phil. 
  Trans. 
  Eoy. 
  Soc. 
  A. 
  vol. 
  ccii. 
  p. 
  183 
  (1903). 
  

  

  