﻿INDEXED. 
  

  

  LONDON, 
  EDINBURGH, 
  and 
  DUBLIN 
  

  

  PHILOSOPHICAL 
  MAGAZINE 
  

  

  AND 
  

  

  JOURNAL 
  OF 
  SCIENCE. 
  

  

  [SIXTH 
  SERIES.] 
  

  

  JUNE 
  1902.^ 
  

  

  LXVI. 
  The 
  Conductivity 
  produced 
  in 
  Gases 
  by 
  the 
  

   of 
  Ultra-Violet 
  Light. 
  By 
  John 
  S. 
  Townsend, 
  M.A,, 
  

   Wykeham 
  Professor 
  of 
  Physics, 
  Oxford*. 
  

  

  1. 
  TN 
  some 
  previous 
  papers 
  on 
  the 
  electrical 
  conductivity 
  

   _I_ 
  of 
  gases 
  it 
  has 
  been 
  proved 
  that 
  a 
  number 
  of 
  com- 
  

   plicated 
  phenomena 
  can 
  be 
  explained 
  by 
  the 
  theory 
  of 
  the 
  

   genesis 
  of 
  ions 
  by 
  collision. 
  In 
  those 
  experiments 
  which 
  

   were 
  designed 
  to 
  test 
  the 
  theory 
  the 
  conductivity 
  was 
  started 
  

   in 
  the 
  gas 
  by 
  Rontgen 
  rays. 
  (J. 
  S. 
  Townsend, 
  Phil. 
  Mag. 
  

   Feb. 
  1901; 
  J. 
  S. 
  Townsend 
  & 
  P. 
  J. 
  Kirkby, 
  Phil. 
  Mag. 
  

   June 
  1901 
  ; 
  P. 
  J. 
  Kirkby, 
  Feb. 
  1902.) 
  

  

  The 
  electric 
  forces 
  which 
  were 
  used 
  were 
  such 
  that 
  the 
  

   potential-differences 
  between 
  the 
  electrodes 
  were 
  not 
  sufficient 
  

   of 
  themselves 
  to 
  produce 
  or 
  maintain 
  a 
  continuous 
  discharge. 
  

  

  A 
  number 
  of 
  interesting 
  results 
  obtained 
  by 
  Stoletow 
  f 
  

   with 
  ultra-violet 
  light 
  can 
  also 
  be 
  explained 
  by 
  the 
  same 
  

   theory, 
  but 
  as 
  his 
  experiments 
  are 
  not 
  arranged 
  so 
  as 
  to 
  give 
  

   an 
  accurate 
  test 
  of 
  the 
  theory, 
  and 
  were 
  made 
  with 
  air 
  alone, 
  

   it 
  was 
  considered 
  desirable 
  to 
  make 
  some 
  new 
  experiments 
  

   with 
  air 
  and 
  other 
  gases. 
  

  

  It 
  is 
  easy 
  to 
  devise 
  experiments 
  so 
  as 
  to 
  obtain 
  a 
  simple 
  

   test 
  of 
  the 
  theory 
  of 
  the 
  genesis 
  of 
  ions 
  by 
  collision, 
  when 
  

   the 
  conductivity 
  is 
  started 
  by 
  means 
  of 
  ultra-violet 
  light. 
  

   In 
  the 
  experiments 
  which 
  are 
  here 
  described 
  the 
  conductivities 
  

  

  * 
  Communicated 
  by 
  the 
  Author. 
  

  

  f 
  Stoletow, 
  Journal 
  de 
  Physique, 
  ser. 
  2, 
  vol. 
  ix. 
  1890. 
  

  

  Phil. 
  Mag. 
  S. 
  6. 
  Vol. 
  3. 
  No. 
  18. 
  June 
  1902. 
  2 
  P 
  

  

  $51 
  

  

  