﻿Positive 
  Ions 
  emitted 
  fr^om 
  various 
  Hot 
  Bodies. 
  667 
  

  

  Without 
  going 
  into 
  any 
  further 
  discussion 
  here 
  it 
  is 
  also 
  

   improbable 
  that 
  the 
  lack 
  of 
  uniformity 
  in 
  the 
  electric 
  potential 
  

   of 
  the 
  disk 
  could 
  explain 
  the 
  variations. 
  

  

  After 
  removing 
  the 
  silv^er 
  disk 
  it 
  was 
  noted 
  that 
  a 
  spot 
  of 
  

   some 
  impurity 
  covered 
  about 
  one-fifth 
  of 
  the 
  area 
  of 
  the 
  disk. 
  

   The 
  thermions 
  that 
  penetrated 
  this 
  layer 
  would 
  probably 
  

   have 
  had 
  their 
  total 
  energy^ 
  diminished. 
  Thus 
  the 
  relative 
  

   number 
  of 
  low-energy 
  ions 
  over 
  the 
  whole 
  surface 
  would 
  

   have 
  been 
  too 
  great 
  and 
  the 
  value 
  of 
  R 
  would 
  have 
  been 
  

   too 
  low. 
  This 
  is 
  the 
  most 
  plausible 
  explanation 
  for 
  the 
  low 
  

   values 
  given 
  by 
  silver. 
  

  

  In 
  some 
  instances 
  at 
  least 
  some 
  ions 
  escaped 
  to 
  the 
  upper 
  

   disk 
  from 
  the 
  heater 
  by 
  going 
  between 
  the 
  radiating 
  disk 
  and 
  

   the 
  lower 
  disk, 
  or 
  by 
  going 
  between 
  the 
  lower 
  disk 
  and 
  the 
  

   guard-ring. 
  But 
  the 
  number 
  was 
  probably 
  small. 
  It 
  is 
  

   difficult 
  to 
  say 
  just 
  what 
  correction 
  should 
  be 
  applied 
  for 
  

   such 
  conditions. 
  

  

  It 
  was 
  considered 
  possible 
  that 
  the 
  high 
  values 
  of 
  R 
  

   obtained 
  in 
  some 
  instances 
  might 
  be 
  accounted 
  for 
  in 
  the 
  

   fact 
  that 
  the 
  disks 
  do 
  not 
  fulfil 
  the 
  conditions 
  of 
  infinite 
  

   planes 
  which 
  is 
  required 
  of 
  them 
  in 
  order 
  to 
  apply 
  the 
  

   formula 
  

  

  »eV 
  

  

  ^ 
  = 
  e 
  Kd 
  . 
  

  

  Particularly 
  in 
  the 
  experiments 
  with 
  iron, 
  which 
  were 
  the 
  

   last 
  performed, 
  there 
  was 
  the 
  most 
  probability 
  of 
  a 
  large 
  

   number 
  of 
  ions 
  escaping 
  to 
  the 
  guard 
  -ring, 
  because 
  of 
  the 
  

   large 
  distance 
  existing 
  between 
  the 
  thermionic 
  radiator 
  and 
  

   the 
  upper 
  disk. 
  Therefore 
  the 
  error 
  that 
  should 
  accrue 
  if 
  

   the 
  distance 
  of 
  the 
  radiator 
  to 
  the 
  upper 
  disk 
  were 
  2 
  mm. 
  

   was 
  calculated. 
  In 
  equation 
  (8), 
  as 
  given 
  in 
  the 
  paper 
  by 
  

   Richardson 
  and 
  Brown 
  {loc. 
  cit.), 
  the 
  current 
  to 
  the 
  upper 
  

   disk 
  is 
  expressed 
  as 
  

  

  i 
  = 
  ne\ 
  ^ 
  F(«o)rf«o\ 
  'r'(W)iW, 
  

  

  ^ 
  7/1 
  

  

  where 
  pQ 
  is 
  the 
  radius 
  of 
  the 
  upper 
  disk 
  and 
  Xq 
  is 
  the 
  distance 
  

   between 
  the 
  upper 
  disk 
  and 
  the 
  thermionic 
  radiator. 
  

  

  By 
  substituting 
  Kmu^ 
  = 
  x 
  and 
  y 
  = 
  y/Km, 
  after 
  putting 
  in 
  

   the 
  values 
  of 
  F(uo)<:^'^o 
  and 
  F'(W)c^W, 
  the 
  above 
  equation 
  

   may 
  be 
  put 
  in 
  the 
  form 
  

  

  2y 
  2 
  

  

  