﻿Positive 
  Rays. 
  685 
  

  

  Nature 
  of 
  Ionization 
  by 
  Cathode 
  Rays. 
  

  

  If, 
  as 
  seems 
  most 
  probable, 
  the 
  positively 
  charged 
  particles 
  

   are 
  produced 
  from 
  the 
  ionization 
  of 
  the 
  gas 
  by 
  cathode 
  rays, 
  

   the 
  study 
  of 
  the 
  processes 
  by 
  which 
  this 
  ionization 
  is 
  accom- 
  

   plished 
  may 
  be 
  expected 
  to 
  throw 
  considerable 
  light 
  on 
  the 
  

   nature 
  of 
  the 
  positive 
  rays. 
  When 
  a 
  gas 
  is 
  ionized 
  by 
  

   cathode 
  rays, 
  secondary 
  cathode 
  rays 
  are 
  generated, 
  and 
  the 
  

   author 
  has 
  recently 
  shown 
  (Proc. 
  Camb. 
  Phil. 
  Soc. 
  xiv. 
  

   p. 
  540, 
  1908) 
  that 
  the 
  maximum 
  velocity 
  of 
  the 
  secondary 
  

   rays 
  is 
  independent 
  of 
  the 
  velocity 
  of 
  the 
  primary 
  rays. 
  

   A 
  comparison 
  of 
  the 
  velocity 
  of 
  the 
  secondary 
  rays 
  from 
  

   gases, 
  as 
  determined 
  in 
  my 
  experiments, 
  with 
  those 
  from 
  

   metals, 
  measured 
  by 
  Fiichtbauer 
  (Phys. 
  Zeits. 
  vii. 
  p. 
  748, 
  

   1908) 
  shows 
  that 
  there 
  is 
  not 
  much 
  difference 
  between 
  the 
  

   two. 
  The 
  velocity 
  of 
  the 
  rays 
  from 
  gases 
  was 
  that 
  due 
  to 
  a 
  

   potential-difference 
  of 
  40 
  volts, 
  of 
  those 
  from 
  metals 
  that 
  

   due 
  to 
  a 
  potential-difference 
  of 
  33 
  volts 
  ; 
  the 
  difference 
  

   between 
  these 
  results 
  is 
  not 
  greater 
  than 
  could 
  be 
  explained 
  

   by 
  errors 
  of 
  experiment. 
  Thus, 
  as 
  far 
  as 
  our 
  present 
  know- 
  

   ledge 
  goes, 
  the 
  velocity 
  of 
  a 
  secondary 
  cathode 
  ray 
  is 
  

   independent 
  both 
  of 
  the 
  velocity 
  of 
  the 
  primary 
  ray 
  and 
  

   varies 
  but 
  little 
  with 
  the 
  nature 
  of 
  the 
  molecule 
  from 
  which 
  

   the 
  secondary 
  ray 
  is 
  projected. 
  The 
  first 
  result 
  shows 
  that 
  

   the 
  energy 
  of 
  the 
  secondary 
  ray 
  is 
  not 
  acquired 
  by 
  a 
  corpuscle 
  

   in 
  the 
  primary 
  rays 
  striking 
  against 
  one 
  in 
  a 
  molecule 
  of 
  a 
  

   gas 
  and 
  imparting 
  to 
  it 
  sufficient 
  energy 
  to 
  force 
  it 
  out 
  of 
  

   the 
  molecule, 
  for 
  if 
  this 
  were 
  the 
  case 
  we 
  should 
  expect 
  the 
  

   energy 
  of 
  the 
  secondary 
  ray 
  to 
  vary 
  quickly 
  with 
  that 
  of 
  the 
  

   primary. 
  Neither 
  does 
  it 
  seem 
  likely 
  that 
  the 
  energy 
  in 
  

   the 
  secondary 
  ray 
  is 
  due 
  to 
  a 
  general 
  explosion 
  of 
  the 
  

   molecule 
  of 
  the 
  gas 
  produced 
  by 
  a 
  gradual 
  accumulation 
  of 
  

   energy 
  in 
  the 
  molecule 
  from 
  impacts 
  with 
  the 
  primary 
  rays, 
  

   for 
  then 
  we 
  should 
  expect 
  the 
  energy 
  in 
  the 
  secondary 
  

   rays 
  to 
  depend 
  largely 
  on 
  the 
  chemical 
  nature 
  of 
  the 
  

   molecules. 
  

  

  As 
  a 
  working 
  hypothesis 
  to 
  account 
  for 
  these 
  very 
  striking 
  

   properties 
  of 
  the 
  secondary 
  rays 
  I 
  would 
  suggest 
  that 
  perhaps 
  

   the 
  first 
  stage 
  is 
  ionization 
  by 
  cathode 
  rays, 
  may 
  be 
  the 
  

   separation 
  from 
  the 
  molecule, 
  not 
  of 
  a 
  single 
  corpuscle, 
  but 
  

   of 
  an 
  electrically 
  neutral 
  doublet 
  consisting 
  of 
  a 
  negatively 
  

   electrified 
  corpuscle 
  in 
  rapid 
  rotation 
  round 
  a 
  much 
  more 
  

   massive 
  particle 
  with 
  a 
  positive 
  charge, 
  and 
  that 
  these 
  

   doublets 
  may 
  be 
  the 
  same 
  from 
  whatever 
  molecule 
  they 
  may 
  

   be 
  ejected. 
  The 
  secondary 
  cathode 
  rays 
  are 
  due 
  to 
  the 
  

   subsequent 
  breaking 
  up 
  of 
  this 
  doublet, 
  their 
  energy 
  being 
  

   the 
  kinetic 
  energy 
  possessed 
  by 
  the 
  corpuscle 
  when 
  rotating 
  

  

  