﻿692 
  Prof. 
  0. 
  W. 
  Richardson 
  on 
  the 
  Kinetic 
  

  

  Reverting 
  to 
  fig. 
  3, 
  we 
  see 
  that 
  the 
  points 
  A 
  and 
  are 
  

   identical 
  within 
  the 
  limits 
  o£ 
  experimental 
  error. 
  This 
  justifies 
  

   the 
  reduction 
  to 
  a 
  common 
  scale 
  by 
  multiplying 
  each 
  series 
  

   o£ 
  observations 
  by 
  a 
  suitable 
  factor. 
  We 
  also 
  notice 
  that 
  a 
  

   smooth 
  curve 
  drawn 
  through 
  the 
  points 
  O 
  and 
  A 
  would 
  also 
  

   include 
  the 
  points 
  x 
  within 
  the 
  limits 
  of 
  experimental 
  error. 
  

   This 
  proves 
  that 
  the 
  percentage 
  change 
  in 
  the 
  ratios 
  produced 
  

   by 
  reversing 
  the 
  heating 
  current 
  is 
  independent 
  of 
  the 
  position 
  

   of 
  the 
  slit 
  ; 
  or, 
  in 
  other 
  words, 
  the 
  ratios 
  I/Iq 
  of 
  the 
  thermionic 
  

   current 
  I 
  through 
  the 
  slit 
  in 
  any 
  position 
  to 
  its 
  value 
  Iq 
  in 
  the 
  

   central 
  position 
  is 
  independent 
  of 
  the 
  direction 
  of 
  the 
  heating- 
  

   current. 
  This 
  fact 
  has 
  already 
  been 
  stated 
  in 
  a 
  rather 
  different 
  

   manner. 
  

  

  It 
  will 
  be 
  observed 
  that 
  the 
  ditferent 
  observations 
  shown 
  

   not 
  only 
  agree 
  with 
  one 
  another, 
  but 
  they 
  also 
  agree 
  fairly 
  

   well 
  with 
  the 
  theoretical 
  curve. 
  In 
  fact, 
  in 
  the 
  central 
  part 
  

   of 
  this 
  figure 
  from 
  x 
  = 
  12 
  to 
  x=.'2& 
  turns 
  the 
  agreement 
  is 
  

   within 
  the 
  limit 
  of 
  the 
  errors 
  of 
  observation. 
  Outside 
  these 
  

   limits 
  the 
  deviation 
  is 
  too 
  great 
  to 
  be 
  explained 
  in 
  this 
  way, 
  

   and 
  it 
  is 
  found 
  that 
  in 
  this 
  case 
  the 
  observed 
  current 
  through 
  

   the 
  slit 
  is 
  invariably 
  greater 
  than 
  the 
  calculated. 
  

  

  There 
  are 
  several 
  ways 
  in 
  w^hich 
  the 
  current 
  at 
  some 
  

   distance 
  from 
  the 
  centre 
  might 
  become 
  too 
  big. 
  The 
  normal 
  

   thermionic 
  current 
  is 
  much 
  greater 
  near 
  the 
  centre, 
  and 
  

   scattering 
  of 
  the 
  ions 
  by 
  the 
  small 
  quantity 
  of 
  gas 
  present 
  

   would 
  have 
  the 
  effect 
  of 
  making 
  the 
  current 
  through 
  the 
  slit 
  

   too 
  big 
  at 
  points 
  further 
  off. 
  However, 
  a 
  comparison 
  of 
  the 
  

   experimental 
  results 
  failed 
  to 
  reveal 
  any 
  connexion 
  between 
  

   the 
  divergence 
  of 
  the 
  curves 
  and 
  the 
  gas 
  pressure, 
  which 
  

   varied 
  considerably 
  in 
  the 
  different 
  experiments. 
  It 
  is 
  im- 
  

   portant 
  to 
  notice 
  also 
  that 
  after 
  the 
  platinum 
  strips 
  have 
  been 
  

   heated 
  for 
  a 
  little 
  while 
  their 
  surfaces 
  are 
  no 
  longer 
  plane, 
  

   owing 
  to 
  a 
  recrystallization 
  of 
  the 
  metal. 
  Under 
  the 
  micro- 
  

   scope 
  the 
  originally 
  smooth 
  rolled 
  foil 
  is 
  found 
  to 
  have 
  

   developed 
  a 
  well-defined 
  crystalline 
  structure, 
  which 
  begins 
  

   to 
  make 
  its 
  appearance 
  after 
  the 
  foil 
  has 
  been 
  heated 
  a 
  very 
  

   short 
  time. 
  It 
  is 
  difficult 
  to 
  decide 
  how 
  much 
  ought 
  to 
  be 
  

   allowed 
  for 
  this 
  ; 
  it 
  will 
  evidently 
  become 
  much 
  more 
  im- 
  

   portant 
  when 
  there 
  is 
  a 
  normal 
  electrostatic 
  field 
  between 
  the 
  

   two 
  planes. 
  The 
  writer 
  is 
  inclined 
  to 
  the 
  view 
  that 
  the 
  effect 
  

   arises 
  from 
  the 
  scattering 
  of 
  the 
  electrons 
  by 
  the 
  plates 
  rather 
  

   than 
  the 
  gas. 
  It 
  seems 
  quite 
  possible 
  that 
  a 
  much 
  more 
  

   marked 
  efifect 
  when 
  a 
  normal 
  electric 
  field 
  is 
  present 
  arises 
  in 
  

   the 
  same 
  way, 
  and 
  the 
  question 
  will 
  be 
  reconsidered 
  later 
  on 
  

   in 
  that 
  connexion. 
  

  

  Our 
  general 
  conclusion, 
  then, 
  from 
  the 
  results 
  exhibited 
  in 
  

  

  