﻿Energy 
  of 
  Negative 
  Electrons 
  emitted 
  by 
  Hot 
  Bodies. 
  375 
  

  

  instance 
  be 
  an 
  effect 
  of 
  the 
  radiant 
  energy 
  o£ 
  the 
  metal 
  

   analogous 
  to 
  the 
  photoelectric 
  effect. 
  In 
  this 
  case 
  the 
  kinetic 
  

   energy 
  would 
  probably 
  be 
  much 
  greater 
  than 
  the 
  thermal 
  

   value. 
  We 
  hope 
  that 
  further 
  research 
  will 
  throw 
  light 
  on 
  

   this 
  point. 
  

  

  It 
  seems 
  to 
  us 
  an 
  important 
  point 
  to 
  have 
  established 
  that 
  

   in 
  one 
  case 
  at 
  any 
  rate, 
  that 
  of 
  platinum 
  heated 
  in 
  air 
  at 
  

   low 
  pressure, 
  the 
  distribution 
  of 
  the 
  square 
  of 
  the 
  velocity 
  

   component 
  normal 
  to 
  the 
  surface 
  among 
  the 
  electrons 
  emitted 
  

   is 
  identical 
  with 
  Maxwell's 
  law 
  of 
  distribution 
  of 
  the 
  same 
  

   quantity 
  for 
  a 
  gas 
  at 
  the 
  temperature 
  of 
  the 
  metal. 
  It 
  has 
  

   been 
  suggested 
  to 
  us 
  that 
  experiments 
  of 
  this 
  kind 
  do 
  not 
  

   necessarily 
  enable 
  us 
  to 
  deduce 
  the 
  law 
  of 
  distribution 
  of 
  

   velocity 
  among 
  the 
  emitted 
  particles, 
  for 
  the 
  reason 
  that 
  

   formulae 
  similar 
  to 
  those 
  on 
  which 
  our 
  conclusion 
  is 
  based 
  

   might 
  be 
  deduced 
  by 
  a 
  purely 
  hydrodynamical 
  kind 
  of 
  

   treatment 
  assuming 
  that 
  the 
  particles 
  exerted 
  a 
  pressure 
  

   which 
  was 
  related 
  to 
  the 
  temperature 
  according 
  to 
  the 
  law 
  

   pv 
  = 
  R0. 
  Since 
  this 
  kind 
  of 
  treatment 
  supposes 
  the 
  matter 
  

   concerned 
  to 
  behave 
  as 
  though 
  it 
  were 
  continuous 
  it 
  would 
  

   follow 
  that 
  the 
  experiments 
  would 
  not 
  warrant 
  any 
  conclusion 
  

   as 
  to 
  the 
  distribution 
  of 
  velocity 
  among 
  the 
  particles. 
  It 
  

   appears 
  to 
  us, 
  however, 
  that 
  this 
  is 
  an 
  unfair 
  view 
  of 
  the 
  

   question 
  to 
  take. 
  It 
  is 
  now 
  well 
  established 
  that 
  the 
  electric 
  

   currents 
  under 
  investigation 
  are 
  carried 
  by 
  charged 
  particles 
  

   whose 
  charge 
  and 
  mass 
  are 
  known. 
  Admitting 
  for 
  the 
  

   moment 
  our 
  interpretation 
  of 
  the 
  experiments, 
  it 
  follows 
  that 
  

   at 
  1650° 
  absolute 
  the 
  mean 
  value 
  of 
  u, 
  the 
  component 
  of 
  the 
  

   velocity, 
  perpendicular 
  to 
  the 
  plate, 
  of 
  the 
  ions 
  emitted 
  is 
  

   about 
  1*5 
  x 
  10 
  7 
  cm. 
  per 
  sec. 
  The 
  distance 
  between 
  the 
  

   plates 
  being 
  2 
  millims., 
  the 
  average 
  time 
  occupied 
  by 
  the 
  

   ions 
  in 
  crossing 
  under 
  zero 
  field 
  would 
  be 
  1*3 
  X 
  10 
  -s 
  sec. 
  

   The 
  maximum 
  current 
  in 
  any 
  of 
  the 
  experiments 
  was 
  

   4' 
  7 
  x 
  10 
  -11 
  ampere, 
  which 
  corresponds 
  to 
  an 
  emission 
  of 
  

   3*6 
  x 
  10 
  8 
  ions 
  per 
  sec. 
  The 
  number 
  of 
  ions 
  present 
  at 
  any 
  

   instant 
  between 
  the 
  two 
  plates 
  would 
  therefore 
  be 
  comparable 
  

   with 
  5. 
  The 
  average 
  distance 
  between 
  them 
  would 
  be 
  so 
  great 
  

   that 
  their 
  mutual 
  forces 
  would 
  be 
  entirely 
  negligible. 
  On 
  

   these 
  grounds 
  it 
  appears 
  to 
  us 
  that 
  the 
  only 
  reasonable 
  view- 
  

   to 
  take 
  is 
  that 
  the 
  current 
  is 
  carried 
  by 
  discrete 
  charged 
  

   particles 
  whose 
  motion 
  after 
  they 
  have 
  left 
  the 
  plate 
  is 
  

   determined 
  solely 
  by 
  the 
  magnitude 
  of 
  the 
  electric 
  field 
  and 
  

   their 
  initial 
  velocity. 
  Unless 
  we 
  are 
  prepared 
  to 
  deny 
  the 
  

   atomic 
  theory 
  of 
  electricity 
  there 
  appears 
  to 
  be 
  no 
  escape 
  

   from 
  the 
  conclusion 
  that 
  the 
  distribution 
  of 
  velocity 
  amono; 
  

  

  