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  THE 
  

   LONDON, 
  EDINBURGH, 
  and 
  DUBLIN 
  

  

  PIEILOSOPHICAL 
  MAGAZINE 
  

  

  AND 
  

  

  JOURNAL 
  OF 
  SCIENCE. 
  

  

  — 
  " 
  — 
  ' 
  f<> 
  ^-. 
  

  

  [SIXTH 
  SERIES.] 
  j 
  q 
  ' 
  ^-^ 
  ^^• 
  

  

  OCIOBER 
  1909. 
  ^ 
  ^^ 
  /^ 
  

  

  LII. 
  On 
  Striations 
  in 
  the 
  Electric 
  Discliarge^.^ 
  // 
  

  

  By 
  Sir 
  J. 
  J. 
  Thomson, 
  M,A,, 
  F.B.S^ 
  ' 
  - 
  

  

  ONE 
  o£ 
  the 
  most 
  conspicuous 
  features 
  of 
  the 
  electric 
  dis- 
  

   charge 
  throuoh 
  gases, 
  when 
  the 
  pressure 
  is 
  within 
  

   certain 
  limits, 
  is 
  the 
  exceedingly 
  well-marked 
  alternations 
  of 
  

   light 
  and 
  darkness 
  which 
  occur 
  in 
  the 
  positive 
  column. 
  

   These 
  alternations, 
  which 
  are 
  called 
  striations, 
  are 
  so 
  varied 
  

   and 
  beautiful 
  that 
  since 
  their 
  discovery 
  by 
  Abria 
  in 
  1843 
  

   they 
  have 
  attracted 
  the 
  attention 
  of 
  many 
  physicists. 
  Grove, 
  

   Gassiott, 
  Spottiswoode 
  and 
  Moulton, 
  De 
  la 
  Rue 
  and 
  Miiller, 
  

   Crookes, 
  ^\"ood. 
  Skinner, 
  H. 
  A. 
  Wilson, 
  and 
  Willows 
  have 
  

   published 
  important 
  researches 
  on 
  the 
  conditions 
  under 
  which 
  

   the 
  striations 
  are 
  produced 
  ; 
  on 
  the 
  influence 
  upon 
  them 
  of 
  

   such 
  things 
  as 
  the 
  nature 
  and 
  pressure 
  of 
  the 
  gas, 
  the 
  size 
  

   of 
  the 
  tube, 
  the 
  current 
  passing 
  through 
  it; 
  and 
  on 
  the 
  dis- 
  

   tribution 
  of 
  the 
  electric 
  force 
  in 
  the 
  neighbourhood 
  of 
  a 
  

   striation. 
  The 
  investigations 
  described 
  in 
  the 
  followino- 
  

   paper 
  relate 
  for 
  the 
  most 
  part 
  to 
  the 
  last 
  of 
  these 
  questions, 
  

   and 
  were 
  made 
  with 
  the 
  object 
  of 
  testing 
  a 
  theory 
  of 
  the 
  

   striations 
  which 
  I 
  gave 
  in 
  my 
  Treatise 
  on 
  the 
  Conduction 
  of 
  

   Electricity 
  through 
  Gases. 
  For 
  these 
  experiments 
  I 
  used 
  

   tubes 
  fitted 
  with 
  Wehnelt 
  cathodes, 
  i. 
  e. 
  the 
  cathode 
  was 
  a 
  

  

  * 
  Communicated 
  by 
  the 
  Author. 
  A 
  Discourse 
  given 
  at 
  the 
  Royal 
  

   Institution 
  on 
  Friday 
  evening, 
  April 
  2, 
  1909. 
  

  

  Phil. 
  Mag. 
  S. 
  6. 
  Vol. 
  18. 
  No. 
  106. 
  Oct. 
  1909. 
  2 
  H 
  

  

  