﻿366 
  Prof. 
  Richardson 
  and 
  Mr. 
  Brown 
  on 
  the 
  Kinetic 
  

  

  out 
  to 
  some 
  extent 
  by 
  taking 
  the 
  current 
  thus 
  obtained 
  to 
  

   correspond 
  to 
  the 
  potential 
  at 
  the 
  middle 
  of 
  the 
  interval. 
  In 
  

   some 
  o£ 
  the 
  experiments 
  a 
  different 
  method 
  of 
  reducing 
  the 
  

   observations 
  was 
  made 
  use 
  of. 
  The 
  observations 
  of 
  potential 
  

   and 
  time 
  were 
  used 
  to 
  plot 
  a 
  curve 
  connecting 
  these 
  two 
  

  

  variables. 
  The 
  values 
  of 
  — 
  r- 
  were 
  then 
  obtained 
  from 
  this 
  

  

  at 
  

  

  curve 
  by 
  geometrical 
  differentiation. 
  This 
  method 
  was 
  not 
  

  

  found 
  to 
  give 
  results 
  which 
  were 
  either 
  more 
  consistent 
  or 
  

  

  more 
  accurate 
  than 
  those 
  given 
  by 
  the 
  other, 
  so 
  that 
  as 
  it 
  

  

  was 
  much 
  more 
  laborious 
  it 
  was 
  discarded. 
  

  

  The 
  maximum 
  potential 
  of 
  the 
  upper 
  plate 
  against 
  which 
  

   a 
  measurable 
  current 
  would 
  go 
  was 
  always 
  about 
  *6 
  of 
  a 
  volt. 
  

   With 
  potentials 
  of 
  this 
  magnitude 
  the 
  current 
  was 
  small, 
  and 
  

   the 
  rate 
  of 
  change 
  of 
  voltage 
  was 
  only 
  measurable 
  when 
  

   either 
  a 
  very 
  small 
  capacity 
  or 
  no 
  capacity 
  at 
  all 
  was 
  added 
  

   to 
  that 
  of 
  the 
  electrometer. 
  Generally 
  speaking 
  it 
  was 
  found 
  

   that 
  the 
  insertion 
  of 
  two 
  capacities 
  which 
  changed 
  the 
  total 
  

   capacity 
  in 
  a 
  ratio 
  of 
  about 
  50 
  to 
  1 
  enabled 
  the 
  currents 
  to 
  

   be 
  measured 
  conveniently 
  throughout 
  the 
  whole 
  range. 
  Two 
  

   series 
  of 
  readings 
  were 
  usually 
  taken 
  with 
  the 
  heating 
  current 
  

   in 
  opposite 
  directions. 
  By 
  taking 
  the 
  mean 
  of 
  two 
  deflexions 
  

   corresponding 
  to 
  any 
  given 
  potential 
  any 
  error 
  arising 
  from 
  

   the 
  central 
  point 
  of 
  the 
  hot 
  strip 
  not 
  being 
  connected 
  to 
  earth 
  

   was 
  eliminated. 
  

  

  As 
  the 
  potential-difference 
  between 
  the 
  two 
  plates 
  was 
  

   always 
  small, 
  the 
  fall 
  of 
  potential 
  along 
  the 
  hot 
  strip 
  itself 
  

   is 
  of 
  considerable 
  importance. 
  It 
  was 
  not 
  possible 
  to 
  deter- 
  

   mine 
  what 
  this 
  amounted 
  to, 
  but 
  it 
  was 
  estimated 
  to 
  be 
  

   between 
  *08 
  and 
  *012 
  volt, 
  and 
  was 
  probably 
  nearer 
  the 
  

   lower 
  than 
  the 
  higher 
  of 
  these 
  two 
  limits. 
  Assuming 
  that 
  

   the 
  middle 
  of 
  the 
  strip 
  was 
  at 
  zero 
  potential 
  the 
  greatest 
  

   potential 
  at 
  any 
  point 
  of 
  the 
  hot 
  metal 
  would 
  lie 
  between 
  

   the 
  limits 
  fOi 
  volt 
  and 
  ±'006 
  volt. 
  It 
  is 
  difficult 
  to 
  be 
  

   quite 
  certain 
  how 
  the 
  results 
  would 
  be 
  affected 
  by 
  the 
  

   existence 
  of 
  this 
  external 
  field 
  along 
  the 
  strip. 
  

  

  A 
  large 
  number 
  of 
  series 
  of 
  observations 
  were 
  taken 
  in 
  

   the 
  manner 
  indicated 
  with 
  slightly 
  varied 
  conditions. 
  The 
  

   numbers 
  recorded 
  in 
  one 
  of 
  them 
  are 
  shown 
  in 
  the 
  accom- 
  

   panying 
  table. 
  It 
  will 
  be 
  noticed 
  that 
  with 
  the 
  same 
  mean 
  

   potential-difference 
  ('11 
  volt) 
  between 
  the 
  plates 
  the 
  currents 
  

   measured 
  were 
  independent 
  of 
  the 
  capacity 
  used. 
  The 
  actual 
  

   determinations 
  were 
  21*5 
  x 
  10~ 
  12 
  ampere 
  with 
  *001 
  micro- 
  

   farad 
  and 
  22xl0~ 
  12 
  ampere 
  with 
  -1 
  microfarad. 
  The 
  

   temperature 
  in 
  this 
  experiment 
  was 
  1283° 
  C. 
  

  

  