﻿916 
  

  

  Dr. 
  Norman 
  Campbell 
  on 
  a 
  

  

  made 
  by 
  purifying 
  the 
  hydrogen 
  by 
  passing 
  it 
  over 
  charcoal 
  

   cooled 
  in 
  liquid 
  air. 
  

  

  5. 
  Preliminary 
  experiments 
  with 
  a 
  rays 
  showed 
  that 
  for 
  

   each 
  gas 
  and 
  tor 
  each 
  distance 
  between 
  the 
  plates 
  there 
  was 
  

   a 
  range 
  of 
  pressure 
  within 
  which 
  the 
  relation 
  between 
  i/l 
  

   and 
  V 
  was 
  approximately 
  independent 
  of 
  the 
  pressure 
  ; 
  and 
  

   that, 
  further, 
  this 
  relation 
  within 
  this 
  range 
  was 
  approxi- 
  

   mately 
  the 
  same 
  whatever 
  the 
  gas 
  and 
  whatever 
  the 
  distance 
  

   between 
  the 
  plates. 
  Accordingly 
  a 
  series 
  of 
  experiments 
  was 
  

   undertaken 
  in 
  which 
  the 
  whole 
  curve 
  relating 
  ijl 
  to 
  V 
  was 
  

   not 
  traced, 
  but 
  the 
  values 
  of 
  that 
  ratio 
  were 
  measured 
  for 
  

   only 
  two 
  values 
  of 
  Y 
  (O'l 
  and 
  0'2 
  volt), 
  while 
  the 
  pressure, 
  

   the 
  nature 
  of 
  the 
  gas, 
  and 
  the 
  distance 
  between 
  the 
  plates 
  

   was 
  varied 
  *. 
  In 
  all 
  cases 
  i/l 
  appeared 
  independent 
  of 
  the 
  

   sign 
  of 
  Y 
  ; 
  the 
  mean 
  of 
  the 
  values 
  for 
  opposite 
  signs 
  is 
  given 
  

   in 
  the 
  following 
  tables 
  I.-YL, 
  which 
  show 
  the 
  results 
  

   obtained. 
  The 
  horizontal 
  lines 
  bound 
  the 
  range 
  over 
  which 
  

   i/l 
  appears 
  to 
  be 
  independent 
  of 
  the 
  pressure, 
  and 
  the 
  means 
  

   at 
  the 
  bottom 
  of 
  each 
  table 
  are 
  those 
  taken 
  over 
  this 
  range. 
  

   I 
  is 
  taken 
  as 
  the 
  value 
  corresponding 
  to 
  Y 
  = 
  40; 
  within 
  the 
  

  

  Table 
  I. 
  

   Air; 
  2l 
  = 
  0'9 
  mm. 
  Ijp^ 
  1*0 
  x 
  lO" 
  15 
  amp./cm. 
  2 
  . 
  

  

  p 
  (in 
  mm.). 
  

   7 
  

  

  i/I. 
  

  

  Y=0.1 
  volt, 
  

  

  0-39 
  

   0-476 
  

  

  0-477 
  

   0-485 
  

  

  V=0'2 
  volt. 
  

  

  0-58 
  

   0-692 
  

   0-709 
  

   0-713 
  

  

  33 
  

  

  46 
  

  

  81 
  

  

  

  122 
  

  

  0-504 
  

   0-492 
  

   0500 
  

   0-492 
  

   0-500 
  

  

  0-730 
  

   0-727 
  

   0-725 
  

  

  0-736 
  

   0-730 
  

  

  162 
  

  

  180 
  

  

  202 
  

  

  220 
  

  

  

  302 
  

  

  0474 
  

   0-466 
  

   0-366 
  

  

  0-498 
  

  

  0-717 
  

   0-680 
  

   0-558 
  

  

  0-730 
  

  

  374 
  

  

  752 
  

  

  Mean 
  

  

  

  * 
  It 
  was 
  found 
  almost 
  impossible 
  to 
  get 
  satisfactory 
  measurements 
  

   when 
  V 
  was 
  less 
  than 
  - 
  l 
  volt. 
  

  

  