﻿Positive 
  Ions 
  emitted 
  from 
  various 
  Hot 
  Bodies, 
  651 
  

   Theory 
  of 
  the 
  Method. 
  

  

  Stated 
  briefly 
  the 
  underlying 
  theory 
  of 
  the 
  method 
  used 
  

   in 
  these 
  investigations 
  is 
  the 
  same 
  as 
  that 
  presented 
  in 
  the 
  

   paper 
  by 
  Richardson 
  and 
  Brown 
  [loc. 
  cit.]. 
  The 
  hot 
  body, 
  

   or 
  thermionic 
  radiator, 
  comprised 
  a 
  plane 
  o£ 
  from 
  0*2 
  to 
  

   *0*3 
  mm.2 
  area, 
  located 
  in 
  the 
  centre 
  of 
  a 
  disk 
  of 
  13 
  mm. 
  

   diameter. 
  The 
  ions 
  emitted 
  impinged 
  on 
  a 
  parallel 
  disk 
  less 
  

   than 
  1 
  mm. 
  distant, 
  which 
  for 
  reference 
  we 
  may 
  call 
  the 
  

   upper 
  disk. 
  

  

  On 
  the 
  view 
  outlined 
  above, 
  the 
  thermionic 
  current 
  * 
  

   to 
  the 
  upper 
  disk 
  is 
  expressed 
  by 
  the 
  equation, 
  , 
  

  

  _neV 
  

  

  i 
  = 
  i^e 
  ^^ 
  , 
  

   •which 
  is 
  equivalent 
  to 
  

  

  R 
  = 
  ^<^i::^Zi) 
  (2) 
  

  

  6'(l0gg2i-l0geZ2) 
  

  

  The 
  working 
  method 
  consisted 
  in 
  applying 
  different 
  

   potentials 
  to 
  the 
  upper 
  plate 
  and 
  then 
  measuring 
  the 
  rate 
  of 
  

   charging 
  up. 
  There 
  are 
  several 
  advantages 
  of 
  this 
  method 
  

   over 
  the 
  one 
  given 
  in 
  previous 
  papers, 
  which 
  always 
  required 
  

   merely 
  the 
  recording 
  of 
  the 
  potential 
  to 
  which 
  the 
  upper 
  

   plate 
  changed 
  in 
  a 
  given 
  time. 
  The 
  chief 
  advantages 
  of 
  the 
  

   present 
  method 
  are, 
  that 
  time 
  is 
  saved 
  in 
  the 
  taking 
  of 
  

   the 
  observations^ 
  the 
  calculations 
  are 
  shortened 
  and 
  simpli- 
  

   fied, 
  and 
  inaccuracies 
  due 
  to 
  any 
  changes 
  in 
  the 
  electrometer 
  

   constant 
  are 
  avoided. 
  Prom 
  the 
  data, 
  curves 
  were 
  made 
  

   showing 
  the 
  thermionic 
  current 
  for 
  different 
  potentials 
  and 
  

   also 
  curves 
  showino- 
  the 
  looarithms 
  of 
  the 
  current 
  for 
  these 
  

   same 
  potentials. 
  In 
  general 
  the 
  curves 
  permitted 
  a 
  quicker 
  

   .and 
  more 
  accurate 
  verification 
  of 
  formula 
  (2) 
  than 
  was 
  

   obtained 
  without 
  them. 
  From 
  the 
  curves 
  the 
  value 
  of 
  the 
  

   kinetic 
  energy 
  of 
  the 
  ions 
  due 
  to 
  the 
  velocity 
  components 
  

   normal 
  to 
  the 
  surface 
  of 
  the 
  thermionic 
  radiator 
  was 
  readily 
  

   determined, 
  by 
  making 
  use 
  of 
  the 
  methods 
  previously 
  given. 
  

  

  Experimental 
  Arrangements, 
  

  

  The 
  special 
  part 
  of 
  the 
  apparatus 
  used 
  in 
  these 
  investigations 
  

   is 
  shown 
  in 
  fig. 
  1. 
  It 
  was 
  put 
  together 
  in 
  three 
  parts, 
  a 
  glass 
  

   tube 
  of 
  20 
  mm. 
  diameter 
  and 
  two 
  well-ground 
  glass 
  stoppers. 
  

   Into 
  the 
  upper 
  stopper 
  were 
  fitted 
  a 
  brass 
  rod 
  Ei 
  and 
  a 
  brass 
  

   tube 
  E2. 
  The 
  tube 
  and 
  the 
  rod 
  were 
  separated 
  and 
  insulated 
  

   from 
  each 
  other 
  by 
  glass 
  tubing 
  g. 
  These 
  parts 
  were 
  fixed 
  and 
  

  

  * 
  For 
  justification 
  for 
  this 
  and 
  similar 
  new 
  terminology 
  used 
  in 
  this 
  

   paper, 
  see 
  paper 
  by 
  0. 
  W. 
  Kichardson, 
  Phil. 
  Mag. 
  June 
  1909, 
  

  

  2X2 
  

  

  