﻿Recombination 
  of 
  Ions 
  made 
  by 
  a 
  Rays. 
  993 
  

  

  be 
  maintained 
  at 
  any 
  desired 
  potential. 
  To 
  prevent 
  diffusion 
  

   o£ 
  the 
  ions, 
  another 
  sheet 
  of 
  gauze, 
  g^ 
  which 
  was 
  earthed 
  was 
  

   placed 
  parallel 
  to 
  the 
  high 
  potential 
  gauze 
  and 
  on 
  the 
  side 
  

   remote 
  from 
  the 
  plate. 
  The 
  a 
  rays 
  were 
  canalised 
  by 
  a 
  set 
  

  

  Fig. 
  1. 
  

  

  £/!ffTH<r- 
  

  

  or 
  n 
  or 
  

  

  •S 
  9i 
  

  

  ^R 
  

  

  u 
  

  

  1} 
  

  

  o£ 
  copper 
  tubes, 
  T, 
  1 
  cm. 
  long 
  by 
  1 
  mm. 
  diameter 
  placed 
  

   over 
  the 
  radium. 
  A 
  screen, 
  8, 
  could 
  be 
  brought 
  over 
  the 
  

   radium 
  to 
  cut 
  off 
  these 
  ol 
  rays, 
  so 
  that 
  the 
  ionization 
  due 
  to 
  

   the 
  ft 
  and 
  <y 
  rays 
  might 
  be 
  measured. 
  The 
  whole 
  of 
  this 
  

   apparatus 
  was 
  enclosed 
  in 
  a 
  nearly 
  gas-tight 
  vessel, 
  which 
  

   in 
  turn 
  was 
  enclosed 
  in 
  an 
  outer 
  vessel. 
  Both 
  were 
  filled 
  

   with 
  the 
  gas 
  under 
  examination, 
  the 
  outer 
  vessel 
  serving 
  to 
  

   prevent 
  diffusion 
  o£ 
  air 
  into 
  the 
  inner. 
  

  

  The 
  ionization 
  current 
  was 
  measured 
  by 
  the 
  method 
  used 
  

   by 
  Bragg. 
  On 
  the 
  tick 
  o£ 
  a 
  clock 
  the 
  key 
  k± 
  was 
  pressed, 
  

   which 
  operated 
  an 
  electromagnet 
  E 
  x 
  and 
  so 
  disconnected 
  the 
  

   electrometer 
  and 
  plate 
  Q 
  from 
  earth. 
  After 
  20 
  ticks 
  of 
  

   the 
  clock 
  (10 
  sees.) 
  or 
  other 
  convenient 
  interval 
  a 
  key 
  k 
  2 
  was 
  

   pressed, 
  which 
  disconnected 
  the 
  plate 
  from 
  the 
  electrometer 
  

   by 
  the 
  agency 
  of 
  another 
  electromagnet, 
  E 
  2 
  . 
  The 
  mean 
  of 
  

   the 
  two 
  ends 
  of 
  the 
  first 
  swing 
  of 
  the 
  needle 
  was 
  taken 
  to 
  be 
  

   proportional 
  to 
  the 
  current. 
  In 
  an 
  experiment 
  on 
  any 
  pure 
  

   gas, 
  the 
  chamber 
  was 
  first 
  exhausted 
  in 
  order 
  to 
  get 
  rid 
  of 
  

   any 
  emanation 
  which 
  chanced 
  to 
  have 
  escaped 
  from 
  the 
  

   radium. 
  The 
  chamber 
  was 
  then 
  filled 
  slowly 
  with 
  dry 
  air 
  

  

  