﻿on 
  Columnar 
  Ionization. 
  527 
  

  

  determinations 
  thus 
  made 
  o£ 
  e 
  from 
  the 
  equation 
  e 
  = 
  xy-^\ 
  

  

  (in 
  arbitrary 
  units) 
  for 
  different 
  values 
  o£ 
  X 
  are 
  given 
  in 
  

   Table 
  IX. 
  From 
  this 
  mean 
  value 
  of 
  e 
  = 
  2032, 
  it 
  was 
  

   possible 
  to 
  determine 
  by 
  the 
  use 
  of 
  equation 
  (1) 
  the 
  value 
  of 
  

   the 
  saturation 
  current. 
  The 
  value 
  given 
  in 
  Table 
  IX. 
  for 
  

  

  Table 
  IX. 
  

  

  X 
  

  

  200 
  

  

  400 
  

  

  600 
  

  

  800 
  

  

  1000 
  

  

  1 
  

  

  CO 
  

  

  , 
  Q 
  

  

  0181 
  

  

  0-260 
  

  

  0-301 
  

  

  0-331 
  

  

  0356 
  

  

  0-525 
  

  

  e 
  

  

  2030 
  

  

  1930 
  

  

  2050 
  

  

  1960 
  

  

  2190 
  

  

  

  X=cc 
  was 
  obtained 
  in 
  this 
  way 
  ; 
  and 
  this 
  value 
  was 
  

   employed 
  in 
  plotting 
  the 
  curve 
  0, 
  fig. 
  5, 
  which 
  is 
  seen 
  to 
  

   intersect 
  the 
  axis 
  of 
  ordinates 
  at 
  the 
  point 
  corresponding 
  to 
  

   the 
  fraction 
  0*41. 
  

  

  The 
  value 
  Q 
  of 
  the 
  saturation 
  current 
  per 
  sq. 
  cm. 
  for 
  a 
  

   single 
  column 
  can 
  be 
  readily 
  deduced 
  after 
  the 
  curve 
  has 
  

   been 
  plotted. 
  Langevin 
  found 
  that 
  for 
  C0 
  2 
  at 
  a 
  pressure 
  of 
  

   one 
  atmosphere 
  e 
  = 
  0*51 
  ; 
  the 
  values 
  of 
  y 
  and 
  x 
  were 
  ob- 
  

   tained 
  corresponding 
  to 
  a 
  field 
  of 
  200 
  volts 
  per 
  cm. 
  and 
  Q 
  

  

  was 
  then 
  deduced 
  by 
  means 
  of 
  the 
  relation 
  x 
  = 
  — 
  ^ 
  . 
  The 
  

  

  value 
  obtained 
  was 
  '551 
  E. 
  S. 
  unit. 
  The 
  ionization 
  current 
  

   in 
  C0 
  2 
  was 
  measured 
  at 
  the 
  same 
  relative 
  part 
  of 
  the 
  range 
  

   of 
  the 
  alpha 
  particle 
  as 
  that 
  in 
  air 
  : 
  and 
  assuming 
  that 
  the 
  

   total 
  ionization 
  in 
  C0 
  2 
  is 
  1*03 
  times 
  that 
  in 
  air, 
  it 
  was 
  easy 
  

   to 
  calculate 
  the 
  number 
  of 
  ions 
  produced 
  by 
  each 
  alpha 
  

   particle 
  within 
  the 
  ionization 
  vessel. 
  The 
  calculation 
  gave 
  

   the 
  area 
  of 
  cross-section 
  S 
  = 
  l"42x 
  10~ 
  5 
  cm. 
  2 
  and 
  the 
  radius 
  

   of 
  the 
  column 
  R 
  = 
  0'0021 
  cm. 
  

  

  The 
  large 
  values 
  obtained 
  for 
  the 
  mean 
  cross-section 
  of 
  

   the 
  columns 
  may 
  at 
  first 
  appear 
  surprising. 
  Professor 
  Bum- 
  

   stead 
  * 
  has 
  already 
  suggested 
  that 
  a 
  considerable 
  part 
  of 
  the 
  

   ionization 
  in 
  the 
  columns 
  may 
  be 
  indirect 
  and 
  be 
  due 
  to 
  the 
  

   action 
  of 
  electrons 
  liberated 
  from 
  the 
  atoms 
  by 
  the 
  action 
  of 
  

   the 
  alpha 
  particle. 
  These 
  electrons 
  would 
  have 
  a 
  range 
  of 
  

   the 
  order 
  of 
  0*1 
  mm. 
  in 
  air 
  at 
  a 
  pressure 
  of 
  one 
  atmosphere. 
  

   Apart 
  from 
  this 
  suggestion, 
  however, 
  it 
  should 
  be 
  remem- 
  

   bered 
  that 
  the 
  cross-section 
  is 
  that 
  of 
  the 
  column 
  after 
  

   the 
  ions 
  have 
  in 
  considerable 
  measure 
  been 
  separated 
  by 
  

   the 
  processes 
  of 
  diffusion 
  and 
  molecular 
  agitation. 
  After 
  the 
  

  

  * 
  Bumstead 
  & 
  McGougan, 
  Phil. 
  3Iao-. 
  [6] 
  xxiy. 
  p. 
  482 
  (1912). 
  

   2X2 
  

  

  