﻿Positive 
  Rays. 
  691 
  

  

  primary 
  and 
  secondary 
  cathode 
  rays 
  were 
  rolled 
  up 
  into 
  a 
  

   small 
  bundle 
  at 
  the 
  mouth 
  of 
  the 
  tube, 
  from 
  which 
  they 
  

   emerge 
  just 
  above 
  the 
  aluminium 
  foil. 
  In 
  this 
  case 
  the 
  

   length 
  ot 
  the 
  path 
  of 
  the 
  rays 
  after 
  coming 
  through 
  the 
  tube 
  

   was 
  only 
  2 
  or 
  3 
  mm., 
  and 
  there 
  was 
  hardly 
  any 
  luminosity 
  

   in 
  the 
  tube. 
  The 
  aluminium 
  foil 
  prevents 
  the 
  ionization 
  in 
  

   the 
  side 
  tube 
  in 
  this 
  case, 
  for 
  if 
  the 
  foil 
  is 
  removed 
  the 
  gas, 
  

   as 
  we 
  have 
  already 
  stated, 
  is 
  ionized. 
  

  

  The 
  preceding 
  experiments 
  are 
  in 
  harmony 
  with 
  the 
  view 
  

   that 
  neutral 
  doublets 
  are 
  one 
  of 
  the 
  stages 
  in 
  the 
  process 
  of 
  

   ionization; 
  they 
  must, 
  however, 
  be 
  regarded 
  as 
  only 
  preli- 
  

   minary. 
  More 
  extended 
  experiments 
  are 
  necessary 
  before 
  

   we 
  can 
  be 
  certain 
  that 
  the 
  effects 
  are 
  not 
  due 
  to 
  some 
  very 
  

   •easily 
  absorbed 
  kind 
  of 
  radiation 
  or 
  to 
  the 
  diffusion 
  of 
  very 
  

   slowly 
  moving 
  ions. 
  

  

  We 
  have 
  hitherto 
  considered 
  the 
  case 
  when 
  the 
  primary 
  

   ionization 
  was 
  due 
  to 
  cathode 
  rays, 
  but 
  there 
  are 
  reasons 
  for 
  

   thinking 
  that 
  similar 
  doublets 
  are 
  produced 
  when 
  the 
  ionization 
  

   is 
  produced 
  by 
  positive 
  rays. 
  Thus 
  Fiichtbauer 
  (loc. 
  cit.) 
  found 
  

   that 
  the 
  velocity 
  of 
  the 
  secondary 
  cathode 
  rays 
  from 
  metals 
  

   was 
  the 
  same 
  whether 
  they 
  were 
  produced 
  by 
  cathode 
  rays 
  

   or 
  Canalstrahlen. 
  It 
  is 
  sometimes 
  argued 
  that 
  the 
  much 
  

   greater 
  difficulty 
  experienced 
  in 
  saturating 
  a 
  gas 
  ionized 
  by 
  

   « 
  particles 
  than 
  one 
  ionized 
  in 
  any 
  other 
  way, 
  shows 
  that 
  

   results 
  of 
  ionization 
  are 
  different 
  in 
  the 
  two 
  cases 
  : 
  this 
  result 
  

   is, 
  however, 
  exactly 
  what 
  we 
  should 
  expect 
  if 
  there 
  were 
  no 
  

   such 
  difference. 
  For 
  when 
  a 
  gas 
  is 
  ionized 
  by 
  a. 
  rays, 
  each 
  

   a 
  particle 
  produces 
  an 
  enormous 
  number 
  of 
  ions, 
  but 
  there 
  

   are 
  comparatively 
  few 
  particles, 
  and 
  these 
  are 
  widely 
  separated. 
  

   Thus 
  in 
  a 
  gas 
  ionized 
  by 
  a 
  rays 
  we 
  have 
  intense 
  ionization 
  in 
  

   some 
  localities 
  and 
  very 
  weak 
  ionization 
  in 
  others, 
  while 
  

   other 
  methods 
  give 
  much 
  more 
  uniform 
  ionization. 
  Now 
  the 
  

   electric 
  force 
  required 
  to 
  saturate 
  a 
  gas 
  depends 
  upon 
  the 
  

   maximum 
  density 
  of 
  ionization 
  as 
  well 
  as 
  upon 
  the 
  average 
  ; 
  

   thus 
  it 
  will 
  require 
  a 
  more 
  intense 
  field 
  to 
  saturate 
  a 
  gas 
  

   ionized 
  by 
  a 
  particles 
  than 
  a 
  gas 
  where 
  the 
  total 
  ionization 
  

   is 
  the 
  same 
  but 
  the 
  ionization 
  is 
  uniformly 
  distributed 
  

   through 
  the 
  gas. 
  The 
  researches 
  of 
  Moulin 
  (Le 
  Radium, 
  

   t. 
  v. 
  March 
  1908) 
  on 
  the 
  ionization 
  by 
  a. 
  rays, 
  show 
  that 
  the 
  

   differences 
  between 
  this 
  kind 
  of 
  ionization 
  and 
  others 
  can 
  

   be 
  explained 
  as 
  arising 
  from 
  the 
  want 
  of 
  uniformity 
  in 
  the 
  

   distribution 
  of 
  the 
  a 
  ionization. 
  

  

  I 
  have 
  much 
  pleasure 
  in 
  thanking 
  Mr. 
  E. 
  Everett 
  and 
  

   Mr. 
  G. 
  W. 
  C. 
  Kaye 
  for 
  the 
  assistance 
  they 
  have 
  given 
  me 
  in 
  

   this 
  investigation. 
  

  

  2Z2 
  

  

  