﻿670 
  Dr. 
  F. 
  C. 
  Brown 
  on 
  the 
  Kinetic 
  Energy 
  of 
  the 
  

  

  difference 
  in 
  the 
  results. 
  The 
  apparatus 
  mentioned 
  here 
  was 
  

   encased 
  entirely 
  in 
  glass 
  with 
  ground 
  joints. 
  The 
  joints 
  

   were 
  made 
  air-tight 
  by 
  vaseline. 
  The 
  vaseline 
  is 
  no 
  doubt 
  

   what 
  formed 
  the 
  insulating 
  layer. 
  For 
  when 
  an 
  entirely 
  

   new 
  apparatus 
  was 
  made 
  o£ 
  platinum 
  and 
  glass 
  and 
  the 
  

   whole 
  was 
  boiled 
  in 
  nitric 
  acid, 
  it 
  was 
  impossible 
  to 
  obtain 
  

   the 
  effect, 
  even 
  after 
  several 
  days' 
  intermittent 
  heating. 
  

  

  In 
  the 
  work 
  described 
  in 
  our 
  former 
  paper 
  there 
  was 
  

   probably 
  a 
  greater 
  chance 
  for 
  errors 
  arising 
  from 
  the 
  high 
  

   ])otential 
  effect 
  than 
  there 
  was 
  in 
  this 
  work. 
  In 
  some 
  of 
  

   the 
  series 
  of 
  observations 
  we 
  noted 
  that 
  the 
  current 
  fell 
  off 
  

   more 
  rapidly 
  than 
  the 
  theory 
  warranted. 
  This 
  would 
  have 
  

   resulted 
  had 
  the 
  condenser 
  been 
  charged 
  almost 
  to 
  its 
  

   capacity. 
  Had 
  the 
  capacity 
  been 
  much 
  smaller 
  the 
  errors 
  

   might 
  have 
  proved 
  serious. 
  

  

  The 
  Charge 
  carried 
  hy 
  the 
  Thermions. 
  

  

  It 
  is 
  interesting 
  to 
  note 
  that 
  we 
  can 
  determine 
  from 
  the 
  

   experimental 
  curves 
  the 
  charge 
  carried 
  by 
  the 
  thermions. 
  

   To 
  do 
  this, 
  however, 
  we 
  must 
  assume 
  that 
  the 
  translational 
  

   kinetic 
  energy 
  of 
  the 
  ions 
  has 
  the 
  same 
  mean 
  value 
  as 
  would 
  

   the 
  molecules 
  of 
  a 
  gas 
  at 
  the 
  same 
  temperature. 
  

  

  In 
  curve 
  2, 
  to 
  which 
  we 
  have 
  already 
  referred, 
  is 
  given 
  a 
  

   current-potential 
  curve 
  for 
  the 
  thermions 
  from 
  gold. 
  The 
  

   area 
  of 
  this 
  curve 
  gives 
  the 
  total 
  energy 
  of 
  all 
  the 
  ions 
  

   which 
  are 
  emitted 
  at 
  zero 
  potential. 
  By 
  dividing 
  this 
  value 
  

   by 
  the 
  number 
  of 
  ions, 
  the 
  mean 
  kinetic 
  energy 
  is 
  obtained 
  

   in 
  the 
  form 
  

  

  eV 
  = 
  ex 
  -11 
  volt, 
  

   then 
  

  

  ^nmv^ 
  = 
  nYe, 
  (1) 
  

  

  where 
  n 
  is 
  the 
  number 
  of 
  molecules 
  of 
  a 
  gas 
  in 
  unit 
  volume 
  

   at 
  0° 
  centigrade 
  and 
  one 
  atmosphere 
  pressure. 
  

  

  By 
  the 
  well-known 
  formula 
  of 
  the 
  kinetic 
  theory 
  of 
  gases 
  

  

  7ilie 
  = 
  }mv\ 
  (2) 
  

  

  where 
  

  

  R=9-6x 
  10-17*. 
  

   From 
  equations 
  (1) 
  and 
  (2) 
  we 
  find 
  the 
  value 
  of 
  the 
  

  

  * 
  See 
  Jeans, 
  ^Dynamical 
  Theory 
  of 
  Gases,' 
  p. 
  113. 
  

  

  