﻿694 
  Kinetic 
  Energy 
  of 
  Ions 
  emitted 
  hy 
  Hot 
  Bodies, 
  

  

  box 
  would 
  probably 
  reach 
  the 
  outside 
  o£ 
  it. 
  As 
  the 
  exact 
  

   amount 
  o£ 
  this 
  correction 
  is 
  somewhat 
  uncertain, 
  it 
  will 
  be 
  

   most 
  satisfactory 
  to 
  see 
  first 
  what 
  is 
  obtained 
  when 
  it 
  is 
  dis- 
  

   regarded 
  alto^-ether. 
  Let 
  us 
  calculate 
  the 
  values 
  o£ 
  lol>h 
  tor 
  

   <3ach 
  of 
  the 
  three 
  sets 
  of 
  experiments 
  recorded 
  in 
  fig. 
  3. 
  For 
  

   the 
  observations 
  with 
  the 
  current 
  direct 
  marked 
  x 
  the 
  

   capacities 
  were 
  "(U 
  microfarad 
  for 
  the 
  slit 
  and 
  "3 
  microfarad 
  

   for 
  the 
  plates. 
  The 
  ratio 
  of 
  the 
  deflexions 
  at 
  the 
  centre 
  of 
  

   the 
  scale 
  was 
  1*39. 
  The 
  value 
  of 
  Io/??i 
  is 
  therefore 
  

  

  _-,.,. 
  9x10^ 
  + 
  180 
  _.A,.o 
  

  

  --• 
  ^^^ 
  27xW+ 
  9x103 
  + 
  180" 
  

  

  With 
  the 
  current 
  reversed 
  and 
  the 
  same 
  capacities, 
  points 
  

   marked 
  0, 
  the 
  maximum 
  was 
  1'39/*81, 
  so 
  that 
  

  

  Io/?2^ 
  = 
  -0564. 
  

  

  With 
  the 
  current 
  reversed 
  and 
  the 
  capacities 
  '04 
  microfarad 
  

   and 
  1 
  microfarad 
  respectively 
  points 
  marked 
  A 
  the 
  maximum 
  

   was 
  1'30, 
  so 
  that 
  

  

  Io/ni 
  = 
  -0502. 
  

  

  The 
  mean 
  of 
  the 
  two 
  values 
  of 
  l^jn^ 
  with 
  reversed 
  current 
  

   is 
  '0534, 
  and 
  of 
  this 
  with 
  the 
  value 
  with 
  the 
  current 
  in 
  the 
  

   opposite 
  direction 
  '0496. 
  

  

  The 
  value 
  of 
  ij'lz 
  in 
  this 
  experiment 
  was 
  '04/2 
  x 
  '4 
  = 
  '050. 
  

  

  Thus 
  without 
  allowing 
  for 
  the 
  correction 
  considered 
  above, 
  

   there 
  is 
  complete 
  agreement 
  between 
  the 
  two 
  sides 
  of 
  the 
  

   equation. 
  As 
  the 
  correction 
  will 
  probably 
  amount 
  to 
  20 
  per 
  

   cent, 
  and 
  possibly 
  somewhat 
  more 
  than 
  that, 
  it 
  seems 
  clear 
  

   that 
  for 
  some 
  reason 
  or 
  other 
  the 
  slit 
  is 
  receiving 
  more 
  than 
  

   its 
  share 
  of 
  the 
  thermions 
  as 
  compared 
  with 
  the 
  plates. 
  

   This 
  result 
  is 
  readily 
  explained 
  on 
  the 
  supposition, 
  that 
  some 
  

   of 
  these 
  electrons 
  are 
  reflected 
  when 
  they 
  strike 
  the 
  plates, 
  

   which 
  was 
  made 
  to 
  explain 
  the 
  divergence 
  between 
  the 
  expe- 
  

   rimental 
  values 
  and 
  the 
  calculated 
  curve 
  in 
  fig. 
  3. 
  These 
  

   results 
  would 
  suggest 
  that 
  from 
  20 
  to 
  40 
  per 
  cent, 
  of 
  these 
  

   low-speed 
  electrons 
  are 
  reflected 
  when 
  they 
  strike 
  the 
  plates, 
  

   but 
  the 
  arrangement 
  used 
  was 
  not 
  suitable 
  for 
  obtaining 
  an 
  

   exact 
  numerical 
  estimate. 
  

  

  Finite 
  Electric 
  Field. 
  

  

  A 
  great 
  many 
  experiments 
  have 
  been 
  made 
  with 
  this 
  appa- 
  

   ratus 
  with 
  a 
  difference 
  of 
  potential 
  applied 
  between 
  the 
  plates 
  

   A 
  and 
  B. 
  As 
  regards 
  agreement 
  with 
  theory, 
  the 
  results 
  

   obtained 
  do 
  not 
  show 
  any 
  improvement 
  over 
  those 
  recorded 
  

   in 
  the 
  previous 
  paper. 
  In 
  fact, 
  with 
  the 
  improved 
  apparatus 
  

  

  