﻿Trowbridge 
  and 
  Richards 
  — 
  Multiple 
  Spectra 
  of 
  Gases. 
  119 
  

  

  to 
  consist 
  of 
  bands 
  similar 
  to 
  that 
  of 
  nitrogen, 
  as 
  well 
  as 
  of 
  

   bright 
  lines 
  ; 
  but 
  when 
  the 
  slit 
  is 
  narrowed 
  every 
  band 
  is 
  

   resolved 
  into 
  a 
  multitude 
  of 
  sharp 
  lines 
  of 
  varying 
  intensities,* 
  

   among 
  which 
  the 
  four 
  usual 
  hydrogen 
  lines, 
  although 
  present, 
  

   are 
  by 
  no 
  means 
  especially 
  prominent. 
  A 
  large 
  capacity 
  is 
  

   required 
  to 
  change 
  this 
  spectrum 
  into 
  the 
  familiar 
  four-line 
  

   spectrum 
  which 
  is 
  comparable 
  with 
  the 
  blue 
  spectrum 
  of 
  

   argon. 
  The 
  change 
  is 
  marked 
  by 
  a 
  sharp 
  alteration 
  in 
  the 
  

   color 
  of 
  the 
  glow 
  from 
  white 
  to 
  a 
  deep 
  red. 
  In 
  the 
  process, 
  

   the 
  bluish 
  green 
  line 
  (H/3) 
  as 
  well 
  as 
  the 
  two 
  in 
  the 
  violet, 
  

   which 
  retain 
  their 
  early 
  position 
  unaltered, 
  become 
  nebulous 
  

   at 
  their 
  edges 
  ;f 
  while 
  the 
  red 
  line 
  Ha 
  remains 
  sharp 
  and 
  clear. 
  

   The 
  most 
  marked 
  change 
  in 
  the 
  spectrum, 
  however, 
  is 
  the 
  com- 
  

   plete 
  obliteration 
  of 
  all 
  the 
  host 
  of 
  other 
  lines 
  covering 
  the 
  

   whole 
  spectrum, 
  and 
  the 
  obvious 
  contrast 
  between 
  the 
  oscilla- 
  

   tory 
  and 
  non- 
  oscillatory 
  spectrum 
  of 
  this 
  gas 
  is 
  quite 
  as 
  strik- 
  

   ing 
  as 
  in 
  the 
  case 
  of 
  nitrogen, 
  although 
  somewhat 
  different 
  in 
  

   nature. 
  This 
  four-line 
  deep 
  red 
  glow 
  appears 
  satisfactorily 
  in 
  

   a 
  tension 
  of 
  gas 
  of 
  about 
  a 
  millimeter, 
  — 
  when 
  the 
  tension 
  of 
  

   the 
  gas 
  is 
  much 
  higher 
  or 
  lower 
  the 
  resistance 
  is 
  increased, 
  the 
  

   oscillations 
  are 
  damped, 
  and 
  other 
  lines 
  begin 
  to 
  appear. 
  Curi- 
  

   ously 
  enough, 
  however, 
  the 
  damping 
  of 
  the 
  oscillatory 
  dis- 
  

   charge 
  does 
  not 
  at 
  first 
  replace 
  all 
  the 
  lines 
  which 
  were 
  extin- 
  

   guished 
  by 
  the 
  introduction 
  of 
  the 
  condenser. 
  At 
  first 
  only 
  a 
  

   sharp 
  line 
  in 
  the 
  yellow 
  and 
  one 
  in 
  the 
  green 
  begin 
  to 
  appear, 
  

   and 
  gradually 
  others 
  are 
  added 
  as 
  the 
  impedance 
  is 
  increased. 
  

  

  The 
  relation 
  of 
  these 
  conclusions 
  to 
  the 
  varying 
  spectra 
  of 
  

   hydrogen 
  observed 
  in 
  stars 
  leads 
  to 
  interesting 
  speculations 
  

   regarding 
  the 
  nature 
  of 
  the 
  electrical 
  and 
  thermal 
  conditions 
  

   in 
  the 
  photospheres 
  of 
  these 
  bodies.^ 
  

  

  Each 
  of 
  the 
  halogens 
  gives 
  two 
  spectra, 
  one 
  with 
  and 
  one 
  

   without 
  the 
  condenser. 
  With 
  iodine, 
  if 
  any 
  of 
  the 
  solid 
  -itself 
  

   is 
  present 
  in 
  the 
  tube, 
  the 
  vapor 
  tension 
  is 
  so 
  soon 
  altered 
  by 
  

   the 
  heat 
  of 
  the 
  discharge 
  that 
  the 
  oscillatory 
  discharge 
  is 
  

   damped 
  and 
  the 
  non 
  oscillatory 
  substituted. 
  Hence 
  the 
  former 
  

   can 
  be 
  obtained 
  only 
  for 
  a 
  few 
  moments. 
  

  

  A 
  tube 
  of 
  helium 
  made 
  by 
  Professor 
  Ramsay, 
  the 
  kind 
  gift 
  

   of 
  the 
  Hon. 
  R. 
  J. 
  Strutt, 
  gave 
  a 
  brilliant 
  yellow 
  glow 
  under 
  

   the 
  influence 
  of 
  the 
  continuous 
  discharge, 
  and 
  a 
  brilliant 
  blue 
  

   with 
  the 
  condenser 
  discharge, 
  but 
  since 
  the 
  bright 
  helium 
  

   lines 
  remained 
  in 
  each, 
  and 
  every 
  other 
  important 
  line 
  in 
  the 
  

   blue 
  spectrum 
  proved 
  to 
  be 
  an 
  argon 
  line, 
  it 
  is 
  evident 
  that 
  the 
  

   oscillations 
  produced 
  no 
  considerable 
  effect 
  upon 
  the 
  helium. 
  

  

  * 
  Smyth. 
  Wied. 
  Ann. 
  Beiblatter 
  (2), 
  vii, 
  p. 
  286. 
  Wiillner 
  observed 
  this 
  spec- 
  

   trum 
  but 
  did 
  not 
  measure 
  the 
  lines. 
  

   f 
  E. 
  Villari, 
  Fievez, 
  and 
  Salet. 
  

   % 
  E. 
  Ebert, 
  Wied. 
  Ann., 
  liii, 
  1894. 
  

  

  