﻿Special 
  Case 
  of 
  Gaseous 
  Conduction, 
  923 
  

  

  paper 
  to 
  the 
  influence 
  of 
  the 
  finite 
  velocity 
  of 
  the 
  S 
  rays 
  on 
  

   conduction 
  at 
  very 
  low 
  pressures. 
  

  

  11. 
  One 
  remarkable 
  observation 
  must 
  now 
  be 
  mentioned. 
  

   It 
  has 
  been 
  stated 
  that 
  similar 
  results 
  were 
  obtained 
  whether 
  

   X 
  rays 
  or 
  <x 
  rays 
  were 
  used 
  ; 
  different 
  results 
  were 
  obtained 
  

   when 
  the 
  ft 
  and 
  y 
  rays 
  from 
  Ra 
  were 
  used. 
  The 
  experi- 
  

   ments 
  were 
  more 
  difficult 
  because 
  of 
  the 
  smallness 
  of 
  the 
  

   currents 
  which 
  could 
  be 
  obtained, 
  but 
  it 
  was 
  found 
  again 
  

   that, 
  within 
  a 
  certain 
  range 
  of 
  pressure 
  for 
  each 
  gas, 
  the 
  

   values 
  of 
  i/I 
  were 
  independent 
  of 
  the 
  pressure 
  and 
  the 
  same 
  

   for 
  all 
  gases. 
  But 
  these 
  values 
  were 
  certainly 
  smaller 
  than 
  

   those 
  obtained 
  with 
  a 
  or 
  X 
  rays. 
  The 
  relation 
  between 
  i/I 
  

   and 
  V 
  agreed 
  best 
  with 
  that 
  predicted 
  by 
  (15) 
  if 
  X 
  were 
  taken 
  

   to 
  be 
  0*031 
  instead 
  of 
  0*025, 
  but 
  the 
  agreement 
  between 
  the 
  

   observed 
  and 
  predicted 
  values 
  was 
  not 
  nearly 
  so 
  good 
  as 
  that 
  

   shown 
  in 
  Table 
  VIII. 
  The 
  numbers 
  corresponding 
  to 
  those 
  

   in 
  Table 
  IX. 
  were 
  all 
  very 
  much 
  smaller 
  than 
  those 
  in 
  that 
  

   table. 
  The 
  values 
  of 
  i/I 
  were 
  unaltered 
  if 
  the 
  total 
  current 
  

   was 
  diminished 
  by 
  moving 
  the 
  Ra 
  further 
  from 
  the 
  chamber, 
  

   but 
  they 
  were 
  decreased 
  still 
  further 
  if 
  it 
  was 
  diminished 
  by 
  

   interposing 
  absorbing 
  screens. 
  The 
  general 
  results 
  may 
  be 
  

   summarized 
  by 
  saying 
  that, 
  when 
  these 
  very 
  penetrating- 
  

   rays 
  were 
  used, 
  \ 
  appeared 
  to 
  increase 
  with 
  the 
  hardness 
  of 
  

   the 
  rays. 
  

  

  These 
  observations 
  were 
  made 
  when 
  the 
  electrodes 
  were 
  

   covered 
  with 
  aluminium. 
  The 
  measurements 
  were 
  repeated 
  

   when 
  the 
  electrodes 
  were 
  covered 
  with 
  soot, 
  and 
  it 
  was 
  then 
  

   found 
  that 
  the 
  anomaly 
  had 
  disappeared 
  ; 
  the 
  measurements 
  

   with 
  ft 
  rays 
  gave 
  exactly 
  the 
  same 
  results 
  as 
  those 
  with 
  a 
  rays 
  

   or 
  X 
  rays. 
  The 
  maximum 
  values 
  of 
  ijl 
  were 
  the 
  same 
  what- 
  

   ever 
  kind 
  of 
  ionizing 
  rays 
  was 
  used, 
  there 
  being 
  only 
  a 
  

   difference 
  in 
  the 
  range 
  of 
  pressure 
  over 
  which 
  these 
  maximum 
  

   values 
  obtain. 
  A 
  comparison 
  of 
  these 
  ranges 
  is 
  not 
  possible, 
  

   for 
  the 
  extent 
  of 
  the 
  range 
  depends 
  on 
  the 
  intensity 
  of 
  the 
  

   ionization, 
  and 
  the 
  source 
  of 
  ft 
  rays 
  used 
  was 
  so 
  feeble 
  that 
  

   the 
  limit 
  of 
  the 
  range 
  on 
  the 
  side 
  of 
  high 
  pressure 
  could 
  not 
  

   be 
  observed. 
  

  

  The 
  influence 
  of 
  the 
  surface 
  of 
  the 
  electrodes 
  is 
  remark- 
  

   able 
  and 
  perhaps 
  deserves 
  further 
  investigation. 
  It 
  appears 
  

   that 
  the 
  influence 
  is 
  different 
  according 
  to 
  the 
  hardness 
  of 
  

   the 
  rays 
  used 
  ; 
  this 
  fact 
  indicates 
  that 
  an 
  explanation 
  of 
  it 
  

   cannot 
  be 
  found 
  in 
  a 
  mere 
  failure 
  of 
  the 
  electrodes 
  to 
  absorb 
  

   all 
  the 
  ions 
  falling 
  on 
  them. 
  Again, 
  the 
  effect 
  can 
  hardly 
  

   be 
  due 
  to 
  differences 
  of 
  the 
  surfaces 
  in 
  the 
  power 
  of 
  emitting 
  

   £ 
  rays, 
  for 
  in 
  all 
  these 
  experiments 
  the 
  S-ray 
  current 
  was 
  

   quite 
  inappreciable 
  compared 
  with 
  the 
  current 
  due 
  to 
  the 
  

  

  