﻿1042 
  Mr. 
  F. 
  W. 
  Wheatley 
  on 
  Ionization 
  of 
  

  

  For 
  this 
  purpose 
  the 
  pressure 
  was 
  reduced 
  to 
  2*84 
  mm., 
  

   and 
  readings 
  were 
  taken 
  with 
  the 
  plates 
  at 
  distances 
  of 
  *2, 
  

   *3, 
  and 
  *4 
  cm. 
  apart. 
  The 
  electromotive 
  force 
  was 
  increased 
  

   in 
  each 
  case 
  until 
  sparking 
  took 
  place. 
  This 
  occurred 
  for 
  

   •2 
  cm. 
  at 
  2140 
  volts 
  per 
  cm., 
  for 
  *3 
  cm. 
  at 
  1600 
  volts 
  per 
  

   cm., 
  and 
  for 
  '4 
  cm. 
  at 
  1250 
  volts 
  per 
  cm. 
  

  

  The 
  values 
  of 
  a 
  for 
  *2 
  and 
  '4 
  cm. 
  were 
  calculated 
  by 
  the 
  

   method 
  described 
  on 
  page 
  1036. 
  For 
  "2 
  and 
  *3 
  cm. 
  a 
  some- 
  

   what 
  similar 
  method 
  was 
  adopted 
  as 
  follows. 
  

  

  I 
  Z 
  -3 
  

  

  * 
  5 
  

  

  a 
  1 
  

  

  * 
  , 
  

  

  

  

  

  

  

  

  Let 
  a 
  and 
  b 
  be 
  the 
  two 
  observed 
  current 
  readings 
  for 
  

   distances 
  *2 
  and 
  *3 
  cm. 
  

  

  Let 
  x 
  be 
  the 
  unknown 
  reading 
  if 
  the 
  plates 
  were 
  *1 
  cm. 
  

   apart. 
  Then 
  we 
  have 
  the 
  following 
  relations 
  : 
  — 
  

  

  (1) 
  a 
  = 
  xe' 
  la 
  + 
  x. 
  

  

  //la 
  

  

  + 
  .z. 
  

  

  (2) 
  b 
  

  

  (3) 
  b 
  = 
  xe" 
  2a 
  + 
  a. 
  

  

  By 
  substituting 
  the 
  value 
  of 
  x 
  — 
  —^ 
  — 
  r 
  from 
  equation 
  (1) 
  

  

  in 
  equations 
  (2) 
  or 
  (3), 
  we 
  get 
  the 
  following 
  equation 
  for 
  

   determining 
  « 
  : 
  — 
  

  

  (4) 
  ae 
  2a 
  +{a-b) 
  e 
  la 
  + 
  (a-6)=0. 
  

  

  The 
  values 
  of 
  a, 
  cx.jp, 
  and 
  X/p 
  are 
  given 
  in 
  Table 
  IV. 
  

  

  Two 
  curves 
  have 
  been 
  drawn 
  for 
  the 
  equation 
  ot/p=f(X/p). 
  

  

  4 
  A 
  gives 
  values 
  of 
  X/p 
  up 
  to 
  528, 
  and 
  4 
  b 
  up 
  to 
  90. 
  

  

  In 
  4 
  b 
  there 
  seems 
  to 
  be 
  a 
  distinct 
  change 
  in 
  the 
  nature 
  

   of 
  the 
  curve 
  between 
  65 
  and 
  70, 
  and 
  in 
  1 
  there 
  is 
  a 
  similar 
  

   change 
  at 
  about 
  50. 
  It 
  will 
  be 
  interesting 
  to 
  determine 
  

   whether 
  this 
  is 
  due 
  to 
  the 
  velocity 
  of 
  agitation 
  of 
  the 
  electrons 
  

   at 
  low 
  electric 
  forces 
  or 
  not. 
  

  

  