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  Prof. 
  McLennan 
  and 
  Mr. 
  Keys 
  on 
  the 
  Electrical 
  

  

  III. 
  Electrical 
  Conductivity 
  imparted 
  to 
  Liquid 
  Air 
  

   by 
  Alpha 
  rays. 
  

  

  (a). 
  After 
  we 
  were 
  satisfied 
  from 
  these 
  preliminary 
  experi- 
  

   ments 
  that 
  the 
  liquid 
  air 
  as 
  used 
  was 
  quite 
  free 
  from 
  any 
  

   contamination 
  which 
  might 
  impart 
  a 
  conductivity 
  to 
  it, 
  a 
  set 
  

   of 
  measurements 
  was 
  made 
  with 
  the 
  apparatus 
  shown 
  in 
  

   fig. 
  1. 
  In 
  this 
  apparatus 
  two 
  copper 
  plates, 
  A 
  and 
  B, 
  were 
  

  

  

  risr. 
  l, 
  

  

  To 
  Battery 
  

  

  CI 
  

  

  

  

  supported 
  by 
  two 
  thick 
  copper 
  wires 
  EA 
  and 
  FB. 
  The 
  

   former 
  was 
  surrounded 
  with 
  a 
  glass 
  tube, 
  and 
  the 
  latter 
  with 
  

   a 
  tube 
  of 
  clear 
  fused 
  quartz. 
  Both 
  were 
  supported 
  by 
  pieces 
  

   of 
  ebonite 
  carried 
  by 
  two 
  metal 
  rods, 
  G 
  and 
  H, 
  attached 
  to 
  

   an 
  earthed 
  metal 
  case 
  which 
  was 
  large 
  enough 
  to 
  contain 
  all 
  

   the 
  apparatus. 
  The 
  wires 
  EA 
  and 
  FB 
  were 
  made 
  about 
  

   60 
  cm. 
  long, 
  so 
  that 
  when 
  the 
  lower 
  ends 
  were 
  immersed 
  in 
  

   liquid 
  air 
  their 
  insulating 
  supports, 
  carried 
  by 
  the 
  rods 
  G 
  

   and 
  H, 
  were 
  sufficiently 
  far 
  removed 
  to 
  prevent 
  moisture 
  

   depositing 
  on 
  them 
  through 
  their 
  being 
  cooled 
  below 
  the 
  dew- 
  

   point 
  and 
  so 
  spoiling 
  the 
  insulation 
  at 
  G 
  and 
  H. 
  

  

  The 
  electrode 
  EA 
  was 
  connected 
  to 
  a 
  battery 
  of 
  small 
  

   storage-cells, 
  and 
  the 
  electrode 
  FB 
  to 
  the 
  free 
  quadrants 
  of 
  

   an 
  electrometer. 
  Before 
  being 
  used 
  the 
  electrodes 
  and 
  their 
  

   supporting 
  wires 
  were 
  all 
  carefully 
  cleaned. 
  

  

  In 
  carrying 
  out 
  these 
  experiments 
  the 
  liquid 
  air 
  was 
  

   always 
  carefully 
  filtered 
  and 
  the 
  measurements 
  were 
  made 
  as 
  

  

  