﻿Positive 
  Ions 
  emitted 
  from 
  various 
  Hot 
  Bodies. 
  661 
  

  

  surface 
  was 
  about 
  0*6 
  mm.^ 
  The 
  fall 
  of 
  potential 
  across 
  this 
  

   surface 
  was 
  approximately 
  0'05 
  volt, 
  and 
  no 
  portion 
  of 
  it 
  

   probably 
  differed 
  from 
  zero 
  potential 
  by 
  more 
  than 
  0*025 
  

   volt. 
  The 
  effect 
  of 
  the 
  fall 
  of 
  potential 
  along 
  the 
  strip 
  

   was 
  investigated 
  by 
  shifting 
  the 
  potential 
  of 
  the 
  centre 
  of 
  the 
  

   strip 
  from 
  zero 
  to 
  +*02 
  volt. 
  Thereby 
  the 
  thermionic 
  

   current 
  was 
  increased 
  by 
  10 
  per 
  cent. 
  This 
  does 
  not 
  

   necessarily 
  indicate 
  that 
  there 
  would 
  be 
  an 
  error 
  as 
  large 
  as 
  

   this 
  in 
  the 
  value 
  of 
  R, 
  because 
  R 
  depends 
  on 
  the 
  way 
  in 
  

   which 
  the 
  current 
  falls 
  off 
  as 
  the 
  upper 
  plate 
  acquires 
  a 
  

   potential. 
  It 
  is 
  not 
  easy 
  to 
  say 
  how 
  a 
  small 
  fall 
  of 
  potential 
  

   would 
  influence 
  the 
  distribution 
  of 
  energy. 
  

  

  Fig. 
  5. 
  

  

  Potential 
  - 
  uolts. 
  

  

  From 
  observations 
  taken 
  in 
  the 
  same 
  way 
  that 
  the 
  previous 
  

   ones 
  were, 
  the 
  current-potential 
  and 
  the 
  logarithm 
  of 
  the 
  

   current-potential 
  curves 
  were 
  plotted. 
  These 
  are 
  respectively 
  

   5 
  and 
  5 
  6 
  in 
  fig. 
  5. 
  The 
  temperature 
  was 
  1120 
  degrees 
  

  

  