﻿Discharging 
  Action 
  of 
  Ultra-violet 
  Light. 
  273 
  

  

  the 
  electrometer 
  showed 
  that 
  G 
  was 
  receiving 
  a 
  negative 
  

   charge. 
  

  

  The 
  deflexion 
  increased 
  continuously 
  until 
  it 
  passed 
  off 
  

   the 
  scale. 
  

  

  When, 
  however, 
  another 
  plug 
  of 
  glass 
  wool 
  was 
  introduced 
  

   into 
  the 
  tube 
  at 
  B, 
  no 
  charge 
  whatever 
  reached 
  G, 
  showing 
  

   that 
  here 
  also, 
  as 
  with 
  gases 
  charged 
  under 
  the 
  action 
  of 
  

   Rontgen 
  rays 
  (J. 
  J. 
  Thomson 
  and 
  E. 
  Rutherford, 
  Phil. 
  Mag. 
  

   Nov. 
  1896, 
  p. 
  393), 
  a 
  plug 
  of 
  glass 
  wool 
  completely 
  discharges 
  

   the 
  gas. 
  

  

  It 
  was 
  found 
  that 
  even 
  with 
  a 
  fairly 
  strong 
  blast 
  only 
  a 
  

   small 
  part 
  of 
  the 
  charge 
  lost 
  by 
  D 
  reached 
  G. 
  The 
  much 
  

   larger 
  part 
  wont 
  to 
  the 
  walls 
  of 
  the 
  tube 
  T. 
  

  

  This 
  was 
  shown 
  by 
  noting 
  the 
  rate 
  of 
  leak 
  under 
  the 
  

   action 
  of 
  the 
  light 
  when 
  first 
  1) 
  was 
  connected 
  to 
  a 
  pair 
  of 
  

   charged 
  quadrants 
  and 
  G 
  was 
  to 
  earth 
  ; 
  and 
  next 
  when 
  both 
  

   D 
  and 
  G 
  were 
  connected 
  to 
  the 
  same 
  charged 
  quadrants. 
  In 
  

   the 
  latter 
  case 
  any 
  charge 
  that 
  reached 
  G 
  went 
  to 
  replenish 
  

   the 
  original 
  charge. 
  

  

  It 
  was 
  further 
  found, 
  when 
  a 
  source 
  of 
  Rontgen 
  rays 
  

   (replacing 
  A 
  and 
  L, 
  and 
  tinfoil 
  being 
  placed 
  over 
  P) 
  was 
  so 
  

   arranged 
  as 
  to 
  discharge 
  the 
  plate 
  D 
  at 
  the 
  same 
  rate 
  as 
  did 
  

   the 
  ultra-violet 
  light, 
  that 
  by 
  using 
  the 
  same 
  blast 
  of 
  air 
  and 
  

   having 
  the 
  same 
  negative 
  charge 
  on 
  D, 
  the 
  quantity 
  of 
  

   positive 
  electrification 
  which 
  reached 
  G 
  w 
  r 
  as 
  considerably 
  less 
  

   than 
  the 
  quantity 
  of 
  negative 
  obtained 
  by 
  the 
  use 
  of 
  the 
  

   light. 
  

  

  The 
  gas 
  blown 
  away 
  from 
  the 
  plate 
  had 
  a 
  proportionally 
  

   greater 
  density 
  of 
  free 
  electrification 
  when 
  ultra-violet 
  light 
  

   was 
  u. 
  c 
  ed 
  than 
  was 
  obtained 
  by 
  the 
  use 
  of 
  the 
  Rontgen 
  rays. 
  

   In 
  the 
  case 
  when 
  light 
  is 
  used 
  the 
  negative 
  carriers 
  start 
  

   from 
  the 
  negative 
  plate 
  and 
  enter 
  the 
  stream 
  of 
  air. 
  With 
  

   Rontgen 
  rays, 
  however, 
  the 
  positive 
  ions, 
  though 
  distributed 
  

   throughout 
  the 
  whole 
  gas, 
  are 
  free 
  from 
  the 
  negative 
  ions 
  

   only 
  when 
  near 
  the 
  plate 
  towards 
  which 
  they 
  are 
  moving, 
  

   and 
  so 
  are 
  less 
  easily 
  blown 
  away. 
  In 
  addition 
  some 
  of 
  the 
  

   free 
  negative 
  ions 
  near 
  the 
  walls 
  of 
  the 
  tube 
  are 
  carried 
  into 
  

   the 
  glass 
  wool 
  and 
  diminish 
  the 
  resultant 
  charge. 
  

  

  These 
  experiments 
  were 
  performed 
  last 
  June 
  at 
  the 
  Physical 
  

   Institute 
  in 
  Berlin, 
  and 
  other 
  work 
  prevented 
  a 
  more 
  thorough 
  

   consideration 
  of 
  the 
  subject. 
  

  

  Cavendish 
  Laboratory, 
  

   Dec. 
  30, 
  1897. 
  

  

  