﻿Spectra 
  of 
  Iodine 
  under 
  High 
  Dispersion. 
  843 
  

  

  In 
  the 
  above 
  table 
  are 
  given 
  the 
  wave-lengths 
  of 
  the 
  

   lines 
  o£ 
  the 
  complete 
  resonance 
  spectrum 
  excited 
  by 
  the 
  green 
  

   Hg 
  line 
  with 
  the 
  quartz 
  arc 
  operating 
  with 
  a 
  potential 
  drop 
  

   of 
  150 
  volts. 
  The 
  numbers 
  at 
  the 
  left 
  of 
  the 
  wave-lengths 
  

   correspond 
  to 
  the 
  numbers 
  given 
  on 
  fig. 
  2 
  (p. 
  834), 
  and 
  serve 
  

   to 
  identify 
  the 
  lines 
  of 
  the 
  group 
  with 
  those 
  on 
  the 
  diagram. 
  

   The 
  numbers 
  to 
  the 
  right 
  of 
  the 
  wave-lengths 
  are 
  roughly 
  

   proportional 
  to 
  the 
  intensity 
  of 
  the 
  lines, 
  1 
  signifying 
  very 
  

   faint, 
  and 
  10 
  very 
  strong. 
  In 
  the 
  case 
  of 
  the 
  groups 
  of 
  the 
  

   orders 
  0, 
  1, 
  and 
  3 
  the 
  wave-lengths 
  were 
  determined 
  from 
  

   photographs 
  made 
  in 
  the 
  fourth 
  order 
  spectrum 
  of 
  the 
  large 
  

   grating, 
  and 
  they 
  can 
  be 
  considered 
  correct 
  to 
  within 
  

   0-02 
  Ang. 
  Un. 
  

  

  These 
  wave-lengths 
  were 
  determined 
  with 
  reference 
  to 
  the 
  

   new 
  standards 
  of 
  iron, 
  molybdenum, 
  and 
  neon. 
  On 
  Plate 
  XV. 
  

   fig. 
  3 
  a 
  portion 
  of 
  the 
  spectrum 
  with 
  the 
  iron 
  spectrum 
  in 
  

   coincidence 
  is 
  reproduced. 
  

  

  Excitation 
  by 
  the 
  Yellow 
  Lines. 
  

  

  The 
  excitation 
  by 
  the 
  yellow 
  mercury 
  lines 
  is 
  best 
  studied 
  

   by 
  removing 
  the 
  green 
  light 
  of 
  the 
  lamp 
  with 
  a 
  solution 
  of 
  

   eosine 
  placed 
  in 
  a 
  large 
  glass 
  cell 
  between 
  the 
  condensing 
  

   lens 
  and 
  the 
  iodine 
  tube. 
  

  

  I 
  have 
  not 
  yet 
  obtained 
  records 
  for 
  the 
  Cooper-Hewitt 
  

   excitation, 
  with 
  the 
  green 
  light 
  removed, 
  but 
  we 
  can 
  trace 
  

   the 
  series 
  excited 
  by 
  the 
  line 
  of 
  shorter 
  wave-length 
  on 
  

   Plate 
  XV. 
  fig. 
  1, 
  since 
  the 
  groups 
  excited 
  by 
  this 
  line 
  lie 
  well 
  

   to 
  the 
  left 
  of 
  the 
  groups 
  excited 
  by 
  the 
  green 
  line. 
  The 
  

   groups 
  excited 
  by 
  the 
  other 
  yellow 
  line 
  are 
  covered 
  by 
  the 
  

   much 
  stronger 
  groups 
  due 
  to 
  the 
  green 
  line 
  excitation, 
  and 
  

   can 
  be 
  uncovered 
  only 
  by 
  the 
  use 
  of 
  the 
  eosine 
  screen. 
  The 
  

   resonance 
  spectrum 
  excited 
  by 
  the 
  yellow 
  lines 
  of 
  the 
  Cooper- 
  

   Hewitt 
  lamp 
  is 
  very 
  faint, 
  and 
  long 
  exposures 
  will 
  be 
  re- 
  

   quired 
  with 
  the 
  iodine 
  tube 
  painted 
  with 
  gelatine 
  stained 
  

   with 
  eosine. 
  With 
  the 
  quartz 
  lamp 
  at 
  140 
  volts 
  the 
  spectrum 
  

   is 
  strongly 
  developed 
  and 
  there 
  is 
  no 
  difficulty 
  in 
  photo- 
  

   graphing 
  the 
  paired 
  groups 
  due 
  to 
  the 
  two 
  yellow 
  lines. 
  

   These 
  form 
  one 
  of 
  the 
  prettiest 
  resonance 
  spectra 
  thus 
  far 
  

   obtained. 
  A 
  portion 
  of 
  the 
  spectrum 
  (six 
  pairs 
  of 
  groups) 
  is 
  

   reproduced 
  on 
  PL 
  XVI. 
  fig. 
  2, 
  the 
  yellow 
  Hg 
  lines 
  (or 
  R.P. 
  

   lines) 
  being 
  the 
  second 
  pair 
  from 
  the 
  left. 
  On 
  PI. 
  XV. 
  fig. 
  5 
  

   we 
  have 
  a 
  smaller 
  portion 
  of 
  the 
  same 
  spectrum 
  made 
  with 
  

   a 
  finer 
  slit 
  and 
  showing 
  better 
  definition. 
  The 
  companion 
  

   lines 
  which 
  accompany 
  the 
  R.R. 
  lines 
  (0 
  Order) 
  come 
  out 
  

   beautifully 
  in 
  this 
  photograph, 
  and 
  show 
  that 
  we 
  are 
  dealing 
  

  

  