﻿420 
  Dr. 
  Hodgson 
  and 
  Mr. 
  Mainstone 
  on 
  Heating 
  

  

  that 
  is 
  only 
  1/18 
  of 
  the 
  length 
  of 
  the 
  cathode 
  dark 
  space. 
  

   The 
  probability 
  of 
  passing 
  this 
  distance 
  without 
  a 
  collision 
  

   is 
  still 
  an 
  extremely 
  small 
  quantity, 
  and 
  this 
  would 
  account 
  

   for 
  the 
  ratio 
  having 
  the 
  value 
  TO. 
  

  

  §8- 
  

  

  Results 
  in 
  Air 
  and 
  Nitrogen. 
  

   Table 
  IV. 
  

   3 
  — 
  Air. 
  

  

  Cathode. 
  

  

  Gas 
  pressure 
  

   in 
  mm. 
  Hg. 
  

  

  M 
  -dt' 
  

  

  iY. 
  

  

  «//?. 
  

  

  B. 
  

  

  Cu 
  

  

  310 
  

   273 
  

   219 
  

   303 
  

   3-06 
  

   ]'80 
  

   0-55 
  

   055 
  

   0-87 
  

   0-80 
  

  

  1-20 
  

   1-18 
  

   1-13 
  

   730 
  

   5-29 
  

   1-19 
  

   3-23 
  

   3-44 
  

   4-13 
  

   413 
  

  

  100 
  

   100 
  

   1-00 
  

   4-02 
  

   300 
  

   0-81 
  

   203 
  

   2-26 
  

   349 
  

   3-49 
  

  

  1-20 
  

   1-18 
  

   113 
  

  

  T82 
  

   V76 
  

   1-46 
  

   1-59 
  

   1-52 
  

   1-18 
  

   1-18 
  

  

  1-38 
  

   1-38 
  

   1-38 
  

   1-79 
  

   1-79 
  

   1-79 
  

   1-47 
  

   1-47 
  

   1-33 
  

   1-33 
  

  

  Cu 
  

  

  On 
  

  

  Pb 
  

  

  Pb 
  

  

  Pb 
  

  

  Ni 
  

  

  Ni 
  

  

  Ag 
  

  

  Ag 
  

  

  

  Table 
  V. 
  

  

  Gas- 
  

  

  -Nitrogen. 
  

  

  Cathode. 
  

  

  Gas 
  pressure 
  

   in 
  mm. 
  Hg. 
  

  

  ™ 
  d9 
  

   M 
  'df 
  

  

  iY. 
  

  

  alii. 
  

  

  A. 
  

  

  Pb 
  

  

  375 
  

   234 
  

   1-35 
  

   1-68 
  

  

  2-28 
  

  

  760 
  ! 
  5-15 
  

   4 
  08 
  ! 
  2-56 
  

   3-53 
  1 
  2-47 
  

   4-06 
  ! 
  2-56 
  

   4-67 
  I 
  3-03 
  

  

  1-48 
  

   1-59 
  

   1-42 
  

   1-58 
  

   1-54 
  

  

  1-76 
  

   1-68 
  

   1-68 
  

   1-59 
  

   1-59 
  

  

  m 
  

  

  Ni 
  

  

  Ag 
  

  

  Ag 
  

  

  

  

  

  It 
  will 
  be 
  seen 
  that 
  in 
  air 
  and 
  nitrogen 
  the 
  ratio 
  has 
  in 
  

   general 
  a 
  value 
  much 
  higher 
  than 
  1*0. 
  The 
  method 
  of 
  pre- 
  

   paring 
  nitrogen 
  is 
  not 
  free 
  from 
  objection 
  : 
  the 
  compound 
  

   used 
  contains 
  oxygen, 
  some 
  of 
  which 
  is 
  liberated 
  with 
  the 
  

   nitrogen 
  ; 
  and 
  Warburg* 
  has 
  shown 
  that 
  a 
  trace 
  of 
  oxygen 
  

   has 
  the 
  effect 
  of 
  increasing 
  considerably 
  the 
  cathode 
  fall. 
  

   The 
  sixth 
  column 
  (Table 
  V.) 
  gives 
  the 
  ratio 
  

  

  cathode 
  fall 
  in 
  oxygen 
  _ 
  . 
  

   cathode 
  fall 
  in 
  nitrogen 
  

  

  which 
  is 
  the 
  maximum 
  value 
  that 
  ajj3 
  can 
  assume 
  under 
  

   these 
  circumstances. 
  The 
  value 
  u//3 
  in 
  each 
  case 
  approaches 
  

   the 
  value 
  A. 
  

  

  * 
  Warburg, 
  Ann. 
  d. 
  Phys. 
  xl. 
  p. 
  1 
  (1890). 
  

  

  