﻿224 
  Welliseh 
  and 
  Woodrow 
  — 
  Columnar 
  Ionization. 
  

  

  stated 
  above, 
  especially 
  those 
  curves 
  corresponding 
  to 
  small 
  

   values 
  of 
  the 
  field 
  : 
  however 
  those 
  points 
  which 
  were 
  of 
  the 
  

   most 
  importance 
  for 
  our 
  subsequent 
  calculations 
  were 
  those 
  

   which 
  were 
  most 
  readily 
  obtained 
  by 
  this 
  method. 
  Moreover 
  

   other 
  considerations 
  made 
  it 
  highly 
  probable 
  that 
  the 
  curves 
  

   corresponding 
  to 
  the 
  small 
  values 
  of 
  the 
  electric 
  field 
  inter- 
  

   sected 
  the 
  axis 
  of 
  ordinates 
  at 
  points 
  close 
  to 
  one 
  another. 
  

  

  In 
  fig. 
  5 
  the 
  limiting 
  values 
  of 
  i/I 
  obtained 
  as 
  above 
  

   described 
  are 
  plotted 
  against 
  the 
  corresponding 
  values 
  of 
  the 
  

   electric 
  field. 
  This 
  curve 
  refers 
  to 
  the 
  longitudinal 
  field 
  in 
  air 
  

   at 
  a 
  pressure 
  of 
  760 
  mm 
  of 
  mercury 
  and 
  may 
  be 
  considered 
  as 
  

   giving 
  the 
  fraction 
  of 
  the 
  total 
  ionization 
  produced 
  by 
  a 
  single 
  

  

  1.0 
  

   .9 
  

  

  .8 
  

  

  

  

  

  Fig 
  

  

  5. 
  

  

  

  

  1 
  —3 
  1 
  

  

  y 
  

  

  

  O^A 
  

  

  

  AIR 
  

  

  — 
  o 
  

  

  

  

  X 
  

  

  

  

  

  

  

  

  

  f 
  

  

  

  

  

  co 
  2 
  

  

  

  

  

  .7 
  

   ,6 
  

   .5 
  

  

  

  

  

  £>^c 
  

  

  

  

  

  

  C 
  

  

  

  

  

  

  

  

  

  

  / 
  

  

  

  

  

  

  

  

  

  f 
  

  

  

  

  

  

  

  

  

  .3 
  

   .2 
  

  

  r 
  

  

  

  

  

  

  

  

  G 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  j 
  

  

  

  

  X 
  

  

  200 
  40O 
  600 
  600 
  1000 
  .1200 
  1400 
  1600 
  

  

  Volts 
  per 
  cm. 
  

  

  alpha 
  particle 
  which 
  is 
  carried 
  over 
  to 
  the 
  electrodes 
  by 
  the 
  

   corresponding 
  electric 
  field. 
  The 
  curve 
  is 
  practically 
  identical 
  

   with 
  that 
  obtained 
  by 
  Moulin 
  ;* 
  it 
  intersects 
  the 
  axis 
  of 
  

   ordinates 
  at 
  a 
  point 
  represented 
  by 
  the 
  fraction 
  0*74. 
  The 
  

   ideal 
  curve 
  for 
  the 
  transverse 
  electric 
  field 
  could 
  not 
  be 
  

   obtained 
  with 
  the 
  same 
  degree 
  of 
  accuracy, 
  but 
  it 
  is 
  approx- 
  

   imately 
  a 
  straight 
  line 
  parallel 
  to 
  the 
  X-axis 
  and 
  with 
  1*0 
  

   as 
  ordinate, 
  indicating 
  that 
  a 
  very 
  small 
  value 
  of 
  the 
  field 
  is 
  

   sufficient 
  to 
  prevent 
  recombination 
  of 
  the 
  ions. 
  

  

  In 
  fig. 
  5 
  is 
  also 
  given 
  a 
  curve 
  obtained 
  by 
  the 
  direct 
  measure- 
  

   ment 
  of 
  the 
  ionization 
  current 
  in 
  the 
  longitudinal 
  field 
  when 
  

   the 
  gas 
  in 
  the 
  vessel 
  was 
  C0 
  2 
  (carefully 
  dried) 
  at 
  a 
  pressure 
  of 
  

  

  * 
  Moulin, 
  loc. 
  cit., 
  p. 
  99. 
  

  

  