﻿364 
  Prof. 
  Richardson 
  and 
  Mr. 
  Brown 
  on 
  the 
  Kinetic 
  

  

  This 
  is 
  not 
  in 
  agreement 
  with 
  the 
  known 
  variation 
  o£ 
  the 
  

   resistance 
  of 
  platinum 
  with 
  temperature. 
  Presumably 
  the 
  

   discrepancy 
  arises 
  from 
  a 
  change 
  in 
  the 
  relative 
  distribution 
  

   of 
  the 
  heat 
  along 
  the 
  strip 
  as 
  the 
  temperature 
  changes. 
  The 
  

   experimental 
  temperatures 
  were 
  obtained 
  from 
  the 
  measured 
  

   resistances 
  by 
  reference 
  to 
  a 
  chart 
  constructed 
  in 
  the 
  above 
  

   way. 
  We 
  believe 
  that 
  this 
  method 
  of 
  getting 
  the 
  temperature 
  

   is 
  trustworthy 
  though 
  not 
  very 
  accurate. 
  

  

  The 
  electrometer 
  and 
  everything 
  connected 
  with 
  it 
  were 
  

   insulated 
  on 
  blocks 
  of 
  paraffin 
  or 
  ebonite, 
  so 
  that 
  the 
  rate 
  of 
  

   leak 
  to 
  or 
  from 
  the 
  upper 
  plate 
  could 
  be 
  measured 
  when 
  it 
  

   was 
  charged 
  to 
  any 
  desired 
  potential. 
  Potentials 
  as 
  high 
  as 
  

   400 
  volts 
  were 
  used 
  in 
  some 
  of 
  the 
  experiments. 
  

  

  Results 
  of 
  tlie 
  Experiments. 
  

  

  In 
  the 
  earlier 
  experiments 
  trouble 
  was 
  experienced 
  on 
  

   account 
  of 
  the 
  occurrence 
  of 
  positive 
  ionization 
  as 
  well 
  as 
  

   negative. 
  With 
  a 
  new 
  wire, 
  as 
  is 
  well 
  known, 
  the 
  positive 
  

   ionization 
  is 
  large 
  compared 
  with 
  the 
  negative, 
  but 
  decays 
  

   away 
  with 
  time, 
  so 
  that 
  after 
  long 
  continued 
  heating 
  the 
  

   positive 
  ionization 
  becomes 
  small 
  compared 
  with 
  the 
  negative. 
  

   The 
  latter 
  was 
  found 
  to 
  remain 
  practically 
  constant 
  under 
  

   comparable 
  conditions 
  throughout 
  the 
  experiments. 
  In 
  order 
  

   to 
  get 
  rid 
  of 
  the 
  positive 
  ionization 
  it 
  was 
  found 
  necessary 
  

   to 
  heat 
  the 
  platinum 
  strip 
  from 
  ten 
  to 
  thirty 
  hours 
  before 
  

   taking 
  readings. 
  In 
  these 
  experiments 
  it 
  was 
  never 
  found 
  

   possible 
  to 
  get 
  rid 
  of 
  the 
  positive 
  ionization 
  completely 
  ; 
  a 
  

   considerable 
  leak 
  was 
  always 
  obtained 
  if 
  the 
  upper 
  plate 
  was 
  

   charged 
  to 
  a 
  high 
  negative 
  potential. 
  We 
  think 
  that 
  most 
  

   of 
  this 
  positive 
  ionization 
  was 
  caused 
  by 
  gas 
  evolved 
  from 
  

   the 
  apparatus 
  when 
  the 
  metal 
  strip 
  was 
  heated. 
  Fortunately 
  

   the 
  positive 
  leak 
  was 
  small 
  when 
  the 
  negative 
  potential 
  

   applied 
  to 
  the 
  upper 
  plate 
  was 
  small. 
  In 
  the 
  experiments 
  it 
  

   was 
  found 
  that 
  the 
  negative 
  ionization 
  emitted 
  by 
  the 
  strip 
  

   was 
  never 
  able 
  to 
  charge 
  the 
  upper 
  plate 
  to 
  a 
  potential 
  

   greater 
  than 
  one 
  volt. 
  If, 
  therefore, 
  the 
  positive 
  leak 
  when 
  

   the 
  upper 
  plate 
  was 
  charged 
  to 
  a 
  potential 
  of 
  —2 
  volts 
  was 
  

   inappreciable 
  compared 
  with 
  the 
  negative 
  leaks 
  against 
  the 
  

   potential 
  which 
  were 
  measured, 
  it 
  was 
  taken 
  that 
  the 
  positive 
  

   leak 
  had 
  been 
  sufficiently 
  got 
  rid 
  of. 
  Great 
  care 
  was 
  taken 
  

   to 
  ensure 
  that 
  this 
  condition 
  was 
  always 
  fulfilled 
  in 
  practice. 
  

  

  One 
  of 
  the 
  authors 
  (Mr. 
  F. 
  C. 
  Brown) 
  observed 
  that 
  the 
  

   positive 
  leak 
  could 
  be 
  got 
  rid 
  of 
  more 
  quickly 
  by 
  charging 
  

   the 
  upper 
  plate 
  to 
  a 
  high 
  negative 
  potential, 
  for 
  example 
  

   200 
  volts. 
  This 
  procedure 
  was, 
  however, 
  found 
  to 
  entirely 
  

   alter 
  the 
  nature 
  of 
  the 
  subsequent 
  discharge 
  of 
  the 
  negative 
  

  

  