﻿92: 
  

  

  Dr. 
  Norman 
  Campbell 
  on 
  a 
  

  

  of 
  high 
  pressures 
  when 
  X 
  rays 
  are 
  used 
  than 
  when 
  a 
  rays 
  

   are 
  used, 
  it 
  would 
  seem 
  likely 
  that 
  the 
  limit 
  to 
  the 
  range 
  on 
  

   the 
  side 
  of 
  high 
  pressure 
  is 
  set 
  by 
  the 
  increasing 
  effects 
  of 
  

   recombination 
  and 
  the 
  failure 
  of 
  condition 
  (A). 
  Table 
  IX. 
  

  

  Table 
  IX. 
  

  

  

  A. 
  

  

  B. 
  

  

  c. 
  

  

  Table 
  I 
  

  

  0001 
  

   0-015 
  

  

  o-ooi 
  

  

  0-023 
  

  

  o-ooi 
  

   o-ooo 
  

  

  0'004 
  

   0-126 
  

   003 
  

   0036 
  

   0-003 
  

   0-006 
  

  

  0-0028 
  

   00102 
  

   0-0024 
  

   0045 
  

   0-0034 
  

   0-0071 
  

  

  „ 
  II 
  

  

  „ 
  III 
  

  

  „ 
  IV 
  

  

  V 
  

  

  „ 
  YI 
  

  

  

  appears 
  rather 
  to 
  show 
  that 
  it 
  is 
  condition 
  (B) 
  which 
  fails, 
  

   but 
  in 
  calculating 
  the 
  figures 
  of 
  Table 
  IX. 
  it 
  is 
  assumed 
  that 
  

   the 
  ionization 
  is 
  uniform. 
  This 
  assumption 
  is 
  doubtless 
  not 
  

   true, 
  especially 
  when 
  a 
  rays 
  are 
  used, 
  and 
  a 
  lack 
  of 
  uni- 
  

   formity 
  in 
  the 
  ionization 
  would 
  certainly 
  make 
  condition 
  (A) 
  

   fail 
  for 
  lower 
  pressures. 
  Nevertheless 
  it 
  is 
  surprising 
  to 
  

   find 
  a 
  number 
  as 
  large 
  as 
  0*126 
  in 
  column 
  B 
  ; 
  but 
  remember- 
  

   ing 
  that 
  the 
  numbers 
  in 
  each 
  column 
  are 
  extreme 
  numbers, 
  

   I 
  do 
  not 
  think 
  that 
  they 
  need 
  throw 
  any 
  doubt 
  on 
  the 
  view 
  

   that 
  the 
  form 
  of 
  conduction 
  studied 
  in 
  these 
  experiments 
  is 
  

   indeed 
  that 
  to 
  which 
  the 
  theory 
  of 
  § 
  2 
  applies, 
  and 
  that 
  the 
  

   limit 
  to 
  the 
  range 
  of 
  its 
  applicability 
  on 
  the 
  side 
  of 
  high 
  

   pressure 
  is 
  set 
  by 
  the 
  effects 
  of: 
  recombination. 
  

  

  The 
  limitation 
  of 
  the 
  range 
  on 
  the 
  side 
  of 
  low 
  pressure 
  

   cannot 
  be 
  accounted 
  for 
  on 
  the 
  theory 
  given. 
  It 
  is 
  probably 
  

   connected 
  with 
  the 
  emihsion 
  of 
  S 
  rays 
  with 
  finite 
  velocities 
  

   from 
  the 
  plates 
  of 
  the 
  condenser 
  and 
  from 
  the 
  gas. 
  When 
  

   the 
  mean 
  free 
  path 
  of 
  the 
  electrons 
  becomes 
  comparable 
  with 
  

   the 
  distance 
  between 
  the 
  plates, 
  their 
  initial 
  velocities 
  in- 
  

   crease 
  the 
  proportion 
  which 
  travel 
  across 
  the 
  condenser 
  

   against 
  the 
  field 
  ; 
  the 
  coefficient 
  of 
  diffusion 
  of 
  the 
  ions 
  

   appears 
  to 
  be 
  increased. 
  And 
  it 
  might 
  be 
  expected 
  that 
  this 
  

   effect 
  would 
  show 
  itself 
  first 
  for 
  the 
  higher 
  values 
  of 
  V 
  

   corresponding 
  to 
  electronic 
  velocities 
  comparable 
  with 
  those 
  

   of 
  the 
  8 
  rays, 
  for 
  so 
  long 
  as 
  V 
  is 
  small 
  compared 
  with 
  these 
  

   velocities 
  it 
  can 
  have 
  no 
  effect 
  in 
  producing 
  a 
  current 
  carried 
  

   by 
  § 
  rays. 
  Further 
  consideration 
  will 
  be 
  given 
  in 
  a 
  later 
  

  

  