﻿350 
  Emission 
  of 
  Electrons 
  from 
  Tungsten. 
  

  

  electrons 
  can, 
  under 
  favourable 
  circumstances, 
  exceed 
  that 
  of 
  

   the 
  tungsten 
  lost 
  proves 
  that 
  the 
  loss 
  of 
  tungsten 
  is 
  not 
  the 
  

   cause 
  of 
  the 
  electronic 
  emission. 
  

  

  (4) 
  The 
  only 
  remaining 
  process 
  of 
  a 
  similar 
  nature 
  to 
  those 
  

   already 
  considered 
  which 
  has 
  not 
  been 
  discussed 
  is 
  the 
  bare 
  

   possibility 
  that 
  the 
  emission 
  is 
  due 
  to 
  the 
  interaction 
  of 
  the 
  

   tungsten 
  with 
  some 
  unknown 
  condensable 
  vapour 
  which 
  does 
  

   not 
  affect 
  the 
  McLeod 
  gauge. 
  This 
  possibility 
  is 
  cut 
  out 
  by 
  

   the 
  fact 
  that 
  the 
  thermionic 
  emission 
  is 
  not 
  affected 
  when 
  the 
  

   liquid 
  air 
  and 
  charcoal 
  is 
  cut 
  off 
  and 
  the 
  vapours 
  allowed 
  to 
  

   accumulate 
  in 
  the 
  tube, 
  and 
  by 
  the 
  fact 
  that 
  very 
  considerable 
  

   changes 
  in 
  the 
  amount 
  and 
  nature 
  of 
  the 
  gases 
  present 
  (as 
  

   by 
  the 
  admission 
  of 
  mercury 
  vapour) 
  have 
  no 
  effect 
  on 
  the 
  

   emission. 
  

  

  Taken 
  together, 
  these 
  experiments 
  prove 
  that 
  the 
  emission 
  

   of 
  electrons 
  does 
  not 
  arise 
  from 
  any 
  interaction 
  between 
  the 
  

   hot 
  filament 
  and 
  surrounding 
  gases 
  or 
  vapours, 
  nor 
  from 
  any 
  

   process 
  involving 
  consumption 
  of 
  the 
  material 
  of 
  the 
  filament. 
  

   It 
  thus 
  follows 
  that 
  the 
  emission 
  of 
  electrons 
  from 
  hot 
  

   tungsten, 
  which 
  there 
  is 
  no 
  reason 
  for 
  not 
  regarding 
  as 
  

   exhibiting 
  this 
  phenomenon 
  in 
  a 
  typical 
  form, 
  is 
  not 
  a 
  

   chemical 
  but 
  a 
  physical 
  process. 
  This 
  conclusion 
  does 
  not 
  

   exclude 
  the 
  possibility 
  that, 
  under 
  other 
  circumstances, 
  

   electrons 
  may 
  be 
  emitted 
  from 
  metals 
  under 
  the 
  influence 
  

   of 
  various 
  chemical 
  reagents 
  — 
  a 
  phenomenon 
  which 
  would 
  be 
  

   expected 
  to 
  exhibit 
  the 
  same 
  law 
  of 
  dependence 
  upon 
  tem- 
  

   perature 
  ; 
  but 
  it 
  does 
  involve 
  a 
  denial 
  of 
  the 
  thesis 
  that 
  this 
  

   emission 
  is 
  invariably 
  caused 
  by 
  processes 
  involving 
  changes 
  

   of 
  material 
  composition. 
  

  

  The 
  experiments 
  also 
  show 
  that 
  the 
  electrons 
  are 
  not 
  

   created 
  either 
  out 
  of 
  the 
  tungsten 
  or 
  out 
  of 
  the 
  surrounding 
  

   gas. 
  It 
  follows 
  that 
  they 
  flow 
  into 
  the 
  tungsten 
  from 
  outside 
  

   points 
  of 
  the 
  circuit. 
  The 
  experiments 
  therefore 
  furnish 
  a 
  

   direct 
  experimental 
  proof 
  of 
  the 
  electron 
  theory 
  of 
  conduction 
  

   in 
  metals. 
  

  

  I 
  wish 
  to 
  express 
  my 
  appreciation 
  of 
  the 
  assistance 
  I 
  have 
  

   received 
  from 
  Mr. 
  K. 
  K. 
  Smith, 
  Instructor 
  in 
  the 
  Laboratory, 
  

   in 
  the 
  preparation 
  of 
  the 
  tubes 
  and 
  in 
  carrying 
  out 
  some 
  of 
  

   the 
  measurements. 
  Mr. 
  Smith 
  and 
  I 
  are 
  engaged 
  in 
  a 
  more 
  

   detailed 
  quantitative 
  study 
  of 
  the 
  emission 
  of 
  electrons 
  from 
  

   tungsten, 
  the 
  results 
  of 
  which 
  we 
  hope 
  shortly 
  to 
  publish. 
  

   I 
  also 
  wish 
  to 
  thank 
  Dr. 
  W. 
  It. 
  Whitney 
  and 
  Dr. 
  I. 
  Langmuir, 
  

   of 
  the 
  General 
  Electric 
  Company, 
  both 
  for 
  supplying 
  the 
  

   specimens 
  of 
  ductile 
  tungsten 
  used 
  and 
  also 
  for 
  giving 
  me 
  

   the 
  benefit 
  of 
  their 
  invaluable 
  experience. 
  

  

  Palmer 
  Physical 
  Laboratory, 
  

   Princeton, 
  N.J. 
  

  

  