﻿462 
  

  

  G. 
  E. 
  Hale 
  — 
  The 
  Ultra- 
  Violet 
  Spectrum 
  

  

  have 
  added 
  Cornu's 
  measures 
  of 
  the 
  hydrogen 
  lines,* 
  and 
  Dr. 
  

   Hoggins' 
  wave-lengths 
  of 
  lines 
  in 
  the 
  hydrogen 
  stellar 
  series,! 
  

   both 
  reduced 
  to 
  the 
  scale 
  of 
  Rowland's 
  map. 
  

  

  Prominences. 
  

  

  Hydrogen. 
  

  

  Calcium 
  

  

  . 
  

  

  Hydrogen. 
  

  

  First 
  Typ 
  

   Stars. 
  

  

  Hale. 
  

  

  Ames. 
  

  

  Rowlanc 
  

  

  i. 
  

  

  Cornu. 
  

  

  Huggius. 
  

  

  3968-56 
  

  

  

  

  3968-61 
  

  

  (H) 
  

  

  

  

  3933-86 
  

  

  

  

  3933-80 
  

  

  (K) 
  

  

  

  

  3888.73 
  

  

  

  

  

  

  

  

  

  3970-11 
  (?) 
  

  

  3970-25 
  

  

  

  

  

  3969-6 
  

  

  3969-6 
  

  

  3889-14 
  

  

  3889-15 
  

  

  

  

  

  3888-5 
  

  

  3888-2 
  

  

  3835-54 
  

  

  3835-6 
  

  

  

  

  3835-1 
  

  

  3834-6 
  

  

  3798-1 
  

  

  3798-0 
  

  

  

  

  

  3797-5 
  

  

  3795 
  6 
  

  

  3770-8 
  

  

  3770-7 
  

  

  

  

  

  3770-0 
  

  

  3768-1 
  

  

  

  

  3750-15 
  

  

  * 
  

  

  

  3749-9 
  

  

  3746-1 
  

  

  

  

  3734-15 
  

  

  

  

  

  3734-2 
  

  

  3730-6 
  

  

  

  

  3721-8 
  

  

  

  

  

  3721-1 
  

  

  3717-9 
  

  

  

  

  3711-9 
  

  

  

  

  

  3711-1 
  

  

  3707-9 
  

  

  

  

  

  

  

  

  

  _ 
  _ 
  . 
  _ 
  

  

  3699-4 
  

  

  Let 
  us 
  first 
  consider 
  the 
  prominence 
  lines 
  which 
  lie 
  near 
  the 
  

   centers 
  of 
  the 
  broad 
  dark 
  shades 
  at 
  H 
  and 
  K. 
  In 
  his 
  observa- 
  

   tions 
  of 
  the 
  chromosphere 
  and 
  prominence 
  spectrum 
  at 
  Mount 
  

   Sherman, 
  in 
  1872, 
  Professor 
  Young 
  succeeded 
  in 
  seeing 
  these 
  

   reversals 
  in 
  a 
  number 
  of 
  cases, 
  but 
  the 
  character 
  of 
  the 
  bright 
  

   lines 
  could 
  not 
  be 
  made 
  out, 
  and 
  it 
  was 
  considered 
  probable 
  

   that 
  the 
  broad 
  dark 
  bands 
  were 
  included 
  in 
  the 
  reversal, 
  only 
  

   the 
  brighter 
  central 
  portions, 
  however, 
  being 
  strong 
  enough 
  to 
  

   affect 
  the 
  eye. 
  We 
  now 
  find, 
  on 
  the 
  contrary, 
  that 
  the 
  sub- 
  

   stance 
  producing 
  the 
  bright 
  prominence 
  lines 
  may 
  possibly 
  be 
  

   entirely 
  distinct 
  from 
  that 
  causing 
  the 
  broad 
  bands 
  in 
  the 
  solar 
  

   spectrum, 
  for 
  though 
  the 
  lines 
  certainly 
  do 
  lie 
  near 
  the 
  centers 
  

   of 
  the 
  bands, 
  they 
  are 
  narrow 
  and 
  sharp, 
  and 
  it 
  is 
  easily 
  con- 
  

   ceivable 
  that 
  their 
  position 
  may 
  be 
  simply 
  the 
  result 
  of 
  chance, 
  

   though 
  perhaps 
  probability 
  would 
  point 
  the 
  other 
  way. 
  We 
  

   are 
  hardly 
  in 
  a 
  position 
  to 
  discuss 
  the 
  cause 
  of 
  the 
  unique 
  ap- 
  

   pearance 
  of 
  the 
  dark 
  H 
  and 
  K 
  bands, 
  but 
  it 
  may 
  be 
  that 
  we 
  

   may 
  learn 
  something 
  in 
  tnis 
  connection 
  from 
  Dr. 
  Huggins' 
  im- 
  

   portant 
  investigations 
  of 
  stellar 
  spectra. 
  It 
  will 
  be 
  remembered 
  

   by 
  everyone 
  that 
  in 
  his 
  memoir 
  " 
  On 
  the 
  Photographic 
  Spectra 
  

   of 
  Stars" 
  communicated 
  to 
  the 
  Royal 
  Society 
  in 
  1880, 
  Dr. 
  

   Huggins 
  arranged 
  the 
  stars 
  observed 
  in 
  a 
  series, 
  in 
  which 
  the 
  

   principal 
  criterion 
  of 
  position 
  was 
  the 
  character 
  of 
  the 
  K 
  line. 
  

   In 
  Arcturus, 
  for 
  instance, 
  this 
  line 
  is 
  broader 
  and 
  more 
  diffuse 
  

   than 
  in 
  the 
  sun 
  itself, 
  while 
  in 
  Sirius 
  it 
  has 
  narrowed 
  down 
  to 
  

  

  * 
  Journal 
  de 
  Physique, 
  18 
  

  

  f 
  Phil. 
  Trans., 
  Part 
  II, 
  18S0, 
  p. 
  669. 
  

  

  