﻿992 
  Mr. 
  H. 
  Off 
  den 
  on 
  the 
  

  

  & 
  

  

  the 
  pair 
  o£ 
  ions 
  to 
  recombine 
  before 
  they 
  could 
  be 
  separated 
  

   by 
  the 
  field. 
  

  

  The 
  matter 
  has 
  been 
  further 
  studied 
  by 
  Langevin, 
  Moulin, 
  

   and 
  others, 
  and 
  attempts 
  have 
  been 
  made 
  to 
  dispense 
  with 
  

   any 
  special 
  hypothesis 
  concerning 
  the 
  recombination 
  of 
  ions 
  

   produced 
  by 
  a 
  rays 
  by 
  attributing 
  the 
  difference 
  in 
  the 
  

   field 
  required 
  to 
  produce 
  saturation 
  entirely 
  to 
  the 
  differ- 
  

   ence 
  in 
  the 
  initial 
  distribution 
  of 
  the 
  ions. 
  Ionization 
  by 
  

   « 
  rays 
  is 
  " 
  columnar 
  " 
  ; 
  the 
  ions 
  are 
  not 
  distributed 
  uniformly 
  

   through 
  the 
  gas 
  but 
  concentrated 
  along 
  the 
  path 
  of 
  the 
  rays 
  

   The 
  effective 
  intensity 
  of 
  the 
  ionization 
  determining 
  the 
  

   amount 
  of 
  recombination 
  is 
  much 
  greater 
  than 
  the 
  average 
  

   intensity. 
  The 
  difference 
  between 
  the 
  effective 
  and 
  the 
  

   average 
  intensities 
  of 
  ionization 
  will 
  be 
  much 
  less 
  if 
  the 
  field 
  

   acts 
  perpendicular 
  to 
  the 
  column 
  of 
  ions, 
  and 
  tends 
  to 
  destroy 
  

   the 
  column 
  by 
  separating 
  the 
  opposite 
  charges, 
  than 
  if 
  it 
  acts 
  

   parallel 
  to 
  the 
  column. 
  The 
  view 
  that 
  the 
  magnitude 
  of 
  the 
  

   saturation-field 
  in 
  the 
  case 
  of 
  a 
  rays 
  could 
  be 
  explained 
  

   on 
  this 
  hypothesis 
  of 
  columnar 
  ionization 
  received 
  support 
  

   when 
  Moulin 
  * 
  found 
  that 
  the 
  saturation-field 
  was 
  less 
  when 
  

   it 
  acted 
  perpendicular 
  than 
  when 
  it 
  acted 
  parallel 
  to 
  the 
  path 
  

   of 
  the 
  rays. 
  

  

  However, 
  this 
  hypothesis 
  of 
  columnar 
  ionization 
  does 
  not 
  

   seem 
  capable 
  of 
  explaining 
  the 
  whole 
  matter. 
  Wheelockf 
  

   concludes 
  that 
  the 
  saturation-field 
  parallel 
  to 
  the 
  rays 
  is 
  

   greater 
  than 
  that 
  predicted 
  by 
  theory. 
  Moreover 
  the 
  theory 
  

   does 
  not 
  seem 
  capable 
  of 
  explaining 
  the 
  very 
  great 
  difference 
  

   observed 
  by 
  Bragg 
  (' 
  Studies 
  in 
  Radioactivity,' 
  vii.) 
  in 
  the 
  

   degree 
  to 
  which 
  Initial 
  Recombination 
  is 
  displayed 
  in 
  dif- 
  

   ferent 
  gases. 
  It 
  appeared, 
  therefore, 
  that 
  a 
  further 
  inves- 
  

   tigation 
  of 
  the 
  problem 
  was 
  desirable, 
  especially 
  in 
  the 
  

   direction 
  of 
  observations 
  with 
  different 
  gases. 
  

  

  The 
  apparatus 
  used 
  was 
  the 
  same 
  as 
  that 
  used 
  by 
  Bragg 
  J 
  

   in 
  his 
  experiments 
  on 
  the 
  ranges 
  of 
  alpha 
  particles 
  from 
  

   radium 
  and 
  its 
  products, 
  and 
  was 
  only 
  altered 
  in 
  a 
  few 
  minor 
  

   details 
  to 
  meet 
  the 
  climatic 
  conditions 
  which 
  in 
  Leeds 
  differ 
  

   from 
  those 
  in 
  Australia, 
  where 
  the 
  apparatus 
  was 
  first 
  used. 
  

   Only 
  a 
  brief 
  description 
  is 
  therefore 
  necessary. 
  A 
  layer 
  of 
  

   radium 
  R 
  (fig. 
  1) 
  was 
  used 
  as 
  the 
  source 
  of 
  a 
  rays. 
  The 
  gas 
  

   of 
  which 
  the 
  ionization 
  was 
  measured 
  was 
  contained 
  between 
  

   an 
  insulated 
  brass 
  plate, 
  Q, 
  connected 
  through 
  a 
  key-box 
  to 
  

   a 
  Dolezalek 
  electrometer, 
  and 
  a 
  sheet 
  of 
  gauze, 
  g 
  g, 
  parallel 
  

   to 
  the 
  plate 
  and 
  distant 
  2*1 
  mm. 
  from 
  it, 
  This 
  gauze 
  could 
  

  

  * 
  Moulin, 
  Comptes 
  Rendus, 
  cxlviii. 
  p. 
  1757 
  (1909). 
  

   t 
  Wheelock, 
  Am. 
  J. 
  Sci. 
  [4 
  J 
  xxx. 
  p. 
  233 
  (1910). 
  

   % 
  Phil. 
  Mag. 
  x. 
  p. 
  318 
  (1905). 
  

  

  