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  LIX. 
  Tlie 
  Ultra-violet 
  Absorption^ 
  Fluorescence^ 
  and 
  Magnetic 
  

   Rotation 
  of 
  Sodium 
  Vapour. 
  By 
  R. 
  W. 
  WoOD, 
  Professor 
  

   of 
  Experimental 
  Physics, 
  Johns 
  Hopkins 
  University 
  *. 
  

   [PLates 
  XV. 
  & 
  XVI.] 
  

  

  r'pHE 
  present 
  paper 
  deals 
  with 
  the 
  optical 
  properties 
  o£ 
  

   i 
  sodium 
  vapour 
  in 
  the 
  ultra-violet, 
  and 
  forms 
  a 
  con- 
  

   tinuation 
  of 
  an 
  extended 
  series 
  of 
  papers 
  already 
  published 
  

   regarding 
  this 
  remarkable 
  metallic 
  vapour. 
  

  

  For 
  a 
  proper 
  understanding 
  of 
  its 
  behaviour 
  in 
  the 
  ultra- 
  

   violet, 
  a 
  brief 
  review 
  of 
  its 
  properties 
  in 
  the 
  visible 
  region 
  

   will 
  be 
  necessary. 
  

  

  The 
  absorption 
  is 
  of 
  two 
  types. 
  A 
  Balmer 
  series 
  of 
  double 
  

   lines, 
  beginning 
  with 
  the 
  D 
  lines 
  and 
  extending 
  into 
  the 
  

   remote 
  ultra-violet. 
  Of 
  these 
  but 
  seven 
  members 
  were 
  known 
  

   previous 
  to 
  the 
  publication 
  of 
  my 
  last 
  paper 
  on 
  the 
  subject 
  in 
  

   this 
  journal 
  f. 
  At 
  that 
  time 
  I 
  had 
  succeeded 
  in 
  raising 
  the 
  

   number 
  to 
  about 
  thirty, 
  since 
  which 
  time, 
  by 
  employing 
  a 
  

   larger 
  quartz 
  spectrograph, 
  I 
  have 
  raised 
  the 
  iiumber 
  to 
  

   forty-eight. 
  The 
  wave-lengths, 
  as 
  measured 
  from 
  the 
  new 
  

   plates, 
  are 
  given 
  in 
  the 
  following 
  table, 
  and 
  full 
  details 
  of 
  

   the 
  work 
  will 
  be 
  found 
  in 
  the 
  Astro-physical 
  Journal 
  for 
  

   March 
  1909. 
  This 
  forms 
  the 
  most 
  complete 
  Balmer 
  series 
  

   thus 
  far 
  observed, 
  only 
  12 
  lines 
  appearing 
  in 
  terrestrial 
  

   hydrogen, 
  and 
  30 
  in 
  solar. 
  

  

  Wave-lengths 
  of 
  Lines 
  in 
  Balmer 
  Series 
  of 
  Sodium 
  Yapour. 
  

  

  3 
  

   4 
  

  

  5 
  

  

  6 
  

  

  7 
  

  

  8 
  

  

  9 
  

  

  10 
  

  

  11 
  

  

  12 
  

  

  13 
  

  

  14 
  

  

  15 
  

  

  16 
  

  

  17 
  

  

  X. 
  

  

  5896-16^ 
  

   90-19 
  I 
  

   3303-07 
  

   02-47 
  

   2852-91 
  

   2680-46 
  I 
  

   2594-05; 
  

   43-82 
  

   12-15 
  

   24'.)0-70 
  

   75-60 
  

   64-53 
  

   56-02 
  

   49-46 
  

   44-24 
  

   4006 
  

   36-70 
  

  

  y. 
  m 
  

  

  n. 
  

  

  X. 
  

  

  2433-85 
  

   31-43 
  

   29-42 
  

   27-72 
  

   26-28 
  

   25-00 
  

   23-88 
  

   22-90 
  

   22-04 
  

   21-29 
  

   20-60 
  

   20-02 
  

   19-50 
  

   1900 
  

   18-44 
  

   38-09 
  

   17-71 
  

  

  n. 
  

  

  X. 
  

  

  18 
  .... 
  

  

  35 
  

  

  2417-38 
  

   17-10 
  

   16-80 
  

   16-56 
  

   16-33 
  

   16-11 
  

   15-89 
  

   15-70 
  

   15-52 
  

   15-37 
  

   15-21 
  

   1506 
  

   14-94 
  

   14-78 
  

   14-64 
  

   34-50 
  

  

  19 
  

  

  36 
  

  

  20 
  

  

  37 
  

  

  21 
  

  

  38 
  

  

  22 
  

  

  39 
  

  

  23 
  

  

  40 
  

  

  1 
  24 
  

  

  41 
  

  

  42 
  

  

  25 
  :.:::.::: 
  

  

  1 
  26 
  

  

  43 
  

  

  27 
  

  

  44 
  

  

  1 
  28 
  

  

  ! 
  29 
  

  

  45 
  

  

  46 
  

  

  30 
  

  

  47 
  

  

  31 
  

  

  48 
  

  

  32 
  

  

  49 
  

  

  33 
  

  

  50 
  

  

  34 
  

  

  i 
  

  

  

  * 
  Communicated 
  by 
  the 
  Author. 
  

  

  t 
  '^ 
  An 
  Extension 
  of 
  the 
  Principal 
  Series 
  of 
  Sodium," 
  Phil. 
  Mag. 
  Dec. 
  

   1908. 
  

  

  