﻿524: 
  Prof. 
  Wellisch 
  and 
  Dr. 
  Woodrow 
  : 
  Experiments 
  

  

  manner 
  in 
  which 
  the 
  ionization 
  curve 
  may 
  be 
  explained 
  by 
  

   introducing 
  the 
  part 
  played 
  by 
  a 
  strictly 
  longitudinal 
  field 
  

   in 
  preventing 
  recombination. 
  The 
  fact 
  that 
  the 
  shape 
  of 
  

   the 
  curve 
  obtained 
  experimentally 
  by 
  us 
  when 
  the 
  longi- 
  

   tudinal 
  field 
  was 
  employed 
  is 
  in 
  such 
  good 
  agreement 
  with 
  

   that 
  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 
  

   corresponding 
  angle 
  in 
  Moulin's 
  experiments), 
  suggests 
  that 
  

   the 
  longitudinal 
  field 
  does 
  play 
  a 
  part 
  in 
  preventing 
  re- 
  

   combination. 
  

  

  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 
  field. 
  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 
  

   intersects 
  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 
  

   saturation 
  curve 
  resulting 
  from 
  the 
  application 
  of 
  increas- 
  

   ing 
  longitudinal 
  fields 
  to 
  those 
  ions 
  in 
  the 
  column 
  which 
  

   have 
  not 
  been 
  separated 
  by 
  the 
  process 
  of 
  diffusion. 
  Lan- 
  

   gevin'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 
  correspond- 
  

   ing 
  to 
  any 
  field 
  X 
  = 
  47r<r 
  is 
  given 
  by 
  

  

  <7 
  

  

  log.(l+^) 
  , 
  . 
  . 
  . 
  . 
  (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 
  0*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 
  ex- 
  

   tremely 
  rapid 
  we 
  have 
  the 
  ideal 
  conditions 
  for 
  applying 
  

   Langevin's 
  theory 
  of 
  recombination. 
  

  

  