﻿216 
  Wellisch 
  and 
  Woodrow 
  — 
  Columnar 
  Ionization. 
  

  

  On 
  the 
  hypothesis 
  of 
  Wellisch 
  and 
  Bronson 
  it 
  was 
  to 
  be 
  ex- 
  

   pected 
  that 
  r 
  ( 
  would 
  be 
  greater 
  than 
  r 
  t 
  for 
  large 
  values 
  of 
  the 
  

   field 
  ; 
  whereas 
  on 
  the 
  Langevin-Moulin 
  theory 
  ?\ 
  should 
  be 
  

   less 
  than 
  r 
  t 
  , 
  except 
  when 
  saturation 
  was 
  attained, 
  in 
  which 
  case 
  

   we 
  should 
  have 
  r 
  x 
  = 
  r 
  t 
  . 
  

  

  In 
  order 
  to 
  determine 
  the 
  value 
  of 
  r 
  t 
  corresponding 
  to 
  any 
  

   value 
  of 
  the 
  field, 
  the 
  ionization 
  currents 
  due 
  to 
  the 
  alpha 
  rays 
  

   from 
  a 
  polonium 
  source 
  were 
  measured 
  in 
  a 
  longitudinal 
  field 
  

   for 
  air 
  at 
  one 
  atmosphere 
  and 
  for 
  air 
  at 
  a 
  lower 
  pressure 
  p. 
  

   The 
  ratio 
  of 
  these 
  currents 
  gives 
  the 
  value 
  of 
  r 
  l 
  and 
  is 
  inde- 
  

   pendent 
  of 
  the 
  actual 
  number 
  of 
  alpha 
  particles 
  entering 
  the 
  

  

  Fig. 
  1. 
  

  

  To 
  Battery 
  

  

  ToPump 
  

  

  & 
  Gauge 
  

  

  measuring 
  apparatus 
  and 
  also 
  of 
  the 
  electrical 
  capacity 
  of 
  the 
  

   system 
  : 
  in 
  fact 
  it 
  is 
  the 
  ratio 
  which 
  would 
  be 
  obtained 
  for 
  the 
  

   ionization 
  due 
  to 
  a 
  single 
  alpha 
  particle. 
  

  

  The 
  ratio 
  r 
  t 
  was 
  obtained 
  in 
  a 
  similar 
  manner 
  by 
  obtaining 
  

   the 
  corresponding 
  currents 
  in 
  the 
  transverse 
  field. 
  

  

  Description 
  of 
  Apparatus 
  and 
  Experimental 
  Procedure. 
  

  

  3. 
  By 
  the 
  kind 
  permission 
  of 
  Prof. 
  Bumstead 
  we 
  were 
  en- 
  

   abled 
  to 
  avail 
  ourselves 
  of 
  the 
  ionization 
  vessel 
  which 
  had 
  pre- 
  

   viously 
  been 
  employed 
  by 
  Wheelock* 
  in 
  his 
  experiments 
  on 
  

   alpha-ray 
  ionization. 
  A 
  general 
  idea 
  of 
  the 
  apparatus 
  and 
  the 
  

   general 
  scheme 
  of 
  connections 
  may 
  be 
  obtained 
  from 
  ^. 
  1. 
  

   For 
  the 
  vertical 
  longitudinal 
  field 
  the 
  ionization 
  vessel 
  consisted 
  

   of 
  a 
  wire 
  gauze 
  B, 
  7'5 
  cm 
  in 
  diameter, 
  situated 
  4 
  mrn 
  below 
  a 
  cir- 
  

   * 
  Wheelock, 
  this 
  Journal 
  (4), 
  xxx, 
  p. 
  233, 
  1910. 
  

  

  