﻿226 
  Wellisch 
  and 
  Woodroiv 
  — 
  Columnar 
  Ionization. 
  

  

  obtained 
  by 
  Moulin, 
  although 
  the 
  method 
  of 
  canalizing 
  the 
  

   rays 
  was 
  quite 
  different 
  (in 
  the 
  present 
  case 
  the 
  extreme 
  rays 
  

   made 
  an 
  angle 
  with 
  the 
  normal 
  less 
  than 
  two-thirds 
  the 
  cor- 
  

   responding 
  angle 
  in 
  Moulin's 
  experiments), 
  suggests 
  that 
  the 
  

   longitudinal 
  field 
  does 
  play 
  a 
  part 
  in 
  preventing 
  recombina- 
  

   tion. 
  

  

  As 
  stated 
  previously, 
  the 
  curve 
  A, 
  fig. 
  5, 
  gives 
  us 
  the 
  ' 
  ideal 
  ? 
  

   curve 
  corresponding 
  to 
  the 
  ionization 
  produced 
  by 
  a 
  single 
  

   alpha 
  particle 
  in 
  a 
  longitudinal 
  tield. 
  The 
  fact 
  that 
  a 
  very 
  

   small 
  field 
  whose 
  value 
  is 
  just 
  large 
  enough 
  to 
  direct 
  the 
  ions 
  

   brings 
  74 
  per 
  cent 
  of 
  the 
  ions 
  to 
  the 
  electrodes 
  shows 
  that 
  this 
  

   percentage 
  of 
  the 
  ions 
  must 
  escape 
  quickly 
  from 
  the 
  column 
  

   as 
  a 
  result 
  of 
  diffusion 
  and 
  molecular 
  agitation. 
  

  

  Let 
  us 
  draw 
  through 
  the 
  point 
  D, 
  where 
  the 
  curve 
  A 
  inter- 
  

   sects 
  the 
  axis 
  of 
  ordinates, 
  a 
  straight 
  line 
  DE 
  parallel 
  to 
  

   the 
  axis 
  of 
  X. 
  If 
  we 
  now 
  refer 
  the 
  curve 
  A 
  to 
  DE 
  and 
  

   DY 
  as 
  axes, 
  we 
  may 
  regard 
  this 
  curve 
  as 
  being 
  a 
  new 
  satura- 
  

   tion 
  curve 
  resulting 
  from 
  the 
  application 
  of 
  increasing 
  lon- 
  

   gitudinal 
  fields 
  to 
  those 
  ions 
  in 
  the 
  column 
  which 
  have 
  not 
  

   been 
  separated 
  by 
  the 
  process 
  of 
  diffusion. 
  Langevin's 
  theory 
  

   of 
  recombination 
  affords 
  a 
  ready 
  means 
  of 
  testing 
  the 
  truth 
  of 
  

   this 
  supposition. 
  According 
  to 
  this 
  theory, 
  if 
  the 
  gas 
  between 
  

   two 
  parallel 
  electrodes 
  is 
  ionized 
  by 
  a 
  single 
  flash 
  of 
  rays 
  of 
  

   very 
  short 
  duration, 
  then 
  the 
  quantity 
  of 
  electricity 
  Q 
  received 
  

   at 
  the 
  electrodes 
  corresponding 
  to 
  any 
  field 
  X 
  = 
  \ira 
  is 
  given 
  

  

  by 
  

  

  ^ 
  = 
  log.(i 
  + 
  ^) 
  (1) 
  

  

  where 
  Q 
  is 
  the 
  total 
  quantity 
  of 
  electricity 
  liberated 
  per 
  sq. 
  

   cm. 
  of 
  cross 
  section 
  and 
  e 
  is 
  a 
  proper 
  fraction 
  which 
  Langevin 
  

   found 
  by 
  experiment 
  to 
  have 
  the 
  value 
  # 
  27 
  for 
  air 
  at 
  a 
  

   pressure 
  of 
  one 
  atmosphere. 
  If 
  we 
  revert 
  to 
  the 
  case 
  of 
  a 
  

   single 
  alpha 
  particle 
  the 
  time 
  which 
  it 
  spends 
  in 
  ionizing 
  is 
  

   extremely 
  small, 
  and 
  if 
  we 
  suppose 
  the 
  initial 
  separation 
  of 
  the 
  

   ions 
  due 
  to 
  molecular 
  agitation 
  to 
  be 
  extremely 
  rapid 
  we 
  have 
  

   the 
  ideal 
  conditions 
  for 
  applying 
  Langevin's 
  theory 
  of 
  recom- 
  

   bination. 
  

  

  In 
  order 
  to 
  test 
  the 
  applicability 
  of 
  this 
  theory, 
  Langevin's 
  

   equation 
  was 
  put 
  in 
  the 
  form 
  

  

  y 
  = 
  ^-log.(i+«) 
  (2) 
  

  

  where 
  

  

  =0. 
  

  

  y 
  = 
  Q/Q 
  and 
  x 
  

  

  