﻿230 
  Wellisch 
  and 
  Woodrow 
  — 
  Columnar 
  Ionization. 
  

  

  /Summary. 
  

  

  (1) 
  A 
  method 
  was 
  devised 
  to 
  compare 
  the 
  ionization 
  due 
  to 
  

   a 
  single 
  alpha 
  particle 
  when 
  measured 
  in 
  a 
  longitudinal 
  and 
  

   transverse 
  field. 
  The 
  results 
  confirm 
  the 
  view 
  of 
  Moulin 
  and 
  

   Langevin 
  that 
  the 
  upward 
  slope 
  characteristic 
  of 
  the 
  alpha-ray 
  

   ionization 
  curve 
  when 
  a 
  longitudinal 
  field 
  is 
  employed, 
  is 
  due 
  

   entirely 
  to 
  recombination 
  of 
  ions 
  in 
  the 
  column. 
  The 
  sugges- 
  

   tion 
  of 
  Wellisch 
  and 
  Bronson 
  that 
  the 
  slope 
  is 
  due 
  in 
  part 
  to 
  

   ionization 
  by 
  collision 
  is 
  shown 
  to 
  be 
  untenable. 
  

  

  (2) 
  It 
  is 
  shown 
  that 
  Langevin's 
  theory 
  of 
  recombination 
  

   appears 
  to 
  be 
  applicable 
  to 
  the 
  ionization 
  produced 
  by 
  a 
  single 
  

   alpha 
  particle 
  ; 
  also 
  the 
  theory 
  enables 
  an 
  estimate 
  of 
  the 
  

   mean 
  cross-section 
  of 
  the 
  column 
  to 
  be 
  computed. 
  

  

  Sloane 
  Laboratory, 
  Yale 
  University, 
  June 
  4, 
  1913. 
  

  

  