﻿18 
  Trowbridge 
  and 
  Richards-^— 
  The 
  Spectra 
  of 
  Argon. 
  

  

  Kayser* 
  criticises 
  Crookes's 
  statement 
  that 
  a 
  condenser 
  and 
  a 
  

   spark 
  gap 
  are 
  necessary 
  for 
  the 
  production 
  of 
  the 
  blue 
  spec- 
  

   trum. 
  He 
  finds 
  that 
  with 
  a 
  lower 
  pressure 
  in 
  the 
  tube 
  than 
  

   2 
  mm 
  the 
  blue 
  spectrum 
  can 
  be 
  readily 
  obtained 
  without 
  con- 
  

   densers 
  and 
  spark 
  gaps. 
  He 
  also 
  states 
  that 
  it 
  is 
  much 
  easier 
  

   to 
  produce 
  the 
  pure 
  blue 
  spectrum 
  than 
  the 
  pure 
  red. 
  In 
  

   order 
  to 
  obtain 
  the 
  red 
  spectrum 
  the 
  strength 
  of 
  the 
  current 
  

   must 
  be 
  adapted 
  to 
  the 
  gas 
  pressure. 
  Kayser 
  employed 
  an 
  

   induction 
  coil. 
  The 
  condenser, 
  however, 
  in 
  the 
  primary 
  of 
  an 
  

   induction 
  coil 
  sends 
  an 
  oscillatory 
  discharge 
  through 
  the 
  sec- 
  

   ondary. 
  Although 
  Kayser 
  did 
  not 
  employ 
  a 
  condenser 
  in 
  the 
  

   manner 
  recommended 
  by 
  Crookes, 
  he 
  still 
  had 
  a 
  condenser 
  in 
  

   his 
  electrical 
  system 
  and 
  the 
  resistance 
  of 
  his 
  Geissler 
  tube 
  was 
  

   probably 
  so 
  proportioned 
  that 
  the 
  secondary 
  circuit 
  was 
  in 
  

   resonance 
  with 
  the 
  primary 
  circuit. 
  To 
  prove 
  this 
  we 
  placed 
  a 
  

   tube 
  containing 
  argon 
  across 
  the 
  terminals 
  of 
  the 
  secondary 
  of 
  

   an 
  induction 
  coil, 
  and 
  having 
  removed 
  the 
  condenser 
  attached 
  

   to 
  the 
  primary, 
  we 
  sent 
  the 
  discharge 
  through 
  the 
  tube 
  by 
  means 
  

   of 
  a 
  break 
  in 
  the 
  induction 
  coil. 
  The 
  light 
  of 
  the 
  discharge 
  

   was 
  red, 
  and 
  when 
  it 
  was 
  examined 
  by 
  a 
  revolving 
  mirror 
  no 
  

   trace 
  of 
  blue 
  was 
  seen 
  in 
  the 
  capillary 
  portion 
  of 
  the 
  tube. 
  

   An 
  adjustable 
  condenser 
  and 
  a 
  variable 
  induction 
  were 
  then 
  

   placed 
  in 
  the 
  primary 
  circuit. 
  By 
  varying 
  the 
  amount 
  of 
  the 
  

   capacity 
  together 
  with 
  the 
  self-induction 
  in 
  the 
  primary 
  sys- 
  

   tem, 
  the 
  discharge 
  in 
  the 
  secondary, 
  when 
  examined 
  by 
  a 
  

   revolving 
  mirror, 
  was 
  seen 
  to 
  consist 
  of 
  both 
  red 
  and 
  blue 
  dis- 
  

   charges. 
  The 
  red 
  glow 
  was 
  evidently 
  due 
  to 
  a 
  unidirectional 
  

   discharge 
  and 
  the 
  blue 
  to 
  an 
  oscillatory 
  discharge. 
  The 
  unidi- 
  

   rectional 
  discharge 
  was 
  caused 
  by 
  the 
  failure 
  of 
  the 
  breaks 
  to 
  

   charge 
  the 
  condenser 
  to 
  the 
  primary, 
  or 
  by 
  increased 
  resistance 
  

   in 
  the 
  tube. 
  When, 
  however, 
  the 
  condenser 
  was 
  charged, 
  it 
  

   immediately 
  discharged 
  in 
  an 
  oscillatory 
  manner; 
  and 
  the 
  sec- 
  

   ondary 
  coil 
  responded 
  by 
  resonance. 
  The 
  rarified 
  argon 
  thus 
  

   shows 
  in 
  an 
  interesting 
  manner 
  what 
  is 
  the 
  function 
  of 
  the 
  

   condenser 
  in 
  the 
  primary 
  of 
  an 
  induction 
  coil. 
  It 
  serves 
  to 
  

   send 
  oscillatory 
  discharges 
  through 
  the 
  primary 
  circuit 
  ; 
  and 
  

   the 
  greatest 
  effect 
  is 
  obtained 
  in 
  the 
  secondary 
  circuit 
  when 
  it 
  

   is 
  in 
  resonance 
  or 
  in 
  tune, 
  so 
  to 
  speak, 
  with 
  the 
  primary. 
  

  

  The 
  presence 
  of 
  a 
  condenser 
  was 
  necessary 
  to 
  form 
  the 
  blue 
  

   glow 
  in 
  Kayser's 
  work, 
  only 
  when 
  the 
  resistance 
  of 
  his 
  tube 
  

   and 
  the 
  self-induction 
  of 
  his 
  coil 
  together 
  were 
  enough 
  to 
  

   damp 
  the 
  discharge 
  of 
  the 
  small 
  capacity 
  of 
  the 
  coil. 
  He 
  

   could 
  have 
  obtained 
  the 
  pure 
  red 
  in 
  any 
  case 
  by 
  interposing, 
  as 
  

   we 
  have 
  done, 
  a 
  resistance 
  or 
  self-induction 
  between 
  the 
  con- 
  

   denser 
  and 
  the 
  tube, 
  although 
  our 
  other 
  resource 
  for 
  obtaining 
  

  

  * 
  Sitzungsberichte 
  der 
  koniglich 
  preussischen 
  Akad. 
  der 
  Wisseuschaften 
  zu 
  

   Berlin, 
  May 
  7, 
  1896. 
  

  

  