﻿Conductivity 
  imparted 
  to 
  Liquid 
  Air 
  by 
  Alpha 
  Rays. 
  889 
  

  

  putting 
  this 
  apparatus 
  together 
  to 
  see 
  that 
  the 
  boss 
  CD 
  did 
  

   not 
  touch 
  either 
  the 
  plate 
  MN 
  or 
  the 
  ebonite 
  plate 
  EF. 
  

   The 
  diameter 
  of 
  the 
  opening 
  in 
  EF 
  was 
  1*06 
  cm., 
  and 
  the 
  

   distance 
  between 
  the 
  boss 
  CD 
  and 
  the 
  face 
  o£ 
  the 
  plate 
  PQ 
  

   towards 
  it 
  was 
  1 
  cm. 
  This 
  apparatus 
  was 
  placed 
  in 
  a 
  strong 
  

   steel 
  cylinder 
  and 
  air 
  was 
  pumped 
  into 
  the 
  latter 
  until 
  the 
  

   pressure 
  stood 
  at 
  120 
  kilograms 
  per 
  sq. 
  cm. 
  The 
  plate 
  AB 
  

   was 
  attached 
  to 
  an 
  insulated 
  wire 
  leading 
  through 
  the 
  

   cylinder 
  and 
  passing 
  on 
  to 
  the 
  quadrants 
  of 
  a 
  Dolezalek 
  

   electrometer. 
  The 
  plate 
  M 
  was 
  connected 
  directly 
  to 
  the 
  

   steel 
  cylinder, 
  which 
  was 
  kept 
  joined 
  to 
  earth, 
  and 
  the 
  plate 
  

   GH 
  was 
  connected 
  by 
  an 
  insulated 
  wire 
  passing 
  through 
  the 
  

   cylinder 
  to 
  a 
  battery 
  of 
  storage-cells. 
  It 
  should 
  be 
  added 
  

   that 
  the 
  apparatus 
  was 
  put 
  together 
  initially 
  without 
  the 
  

   polonium-coated 
  plate 
  PQ 
  in 
  position 
  and 
  was 
  found 
  to 
  

   insulate 
  perfectly 
  when 
  surrounded 
  with 
  air 
  in 
  the 
  steel 
  

   cylinder 
  at 
  120 
  kilograms 
  per 
  sq. 
  cm. 
  pressure. 
  

  

  With 
  the 
  polonium-coated 
  plate 
  in 
  position 
  one 
  had 
  with 
  

   this 
  arrangement 
  a 
  layer 
  of 
  highly 
  ionized 
  air 
  close 
  to 
  the 
  

   plate 
  PQ. 
  Moreover, 
  the 
  field 
  between 
  the 
  plate 
  PQ 
  and 
  

   the 
  boss 
  CD 
  w^as 
  a 
  uniform 
  one, 
  and 
  the 
  dimensions 
  of 
  

   the 
  field 
  through 
  which 
  conduction 
  could 
  take 
  place 
  to 
  the 
  

   electrode 
  CD 
  were 
  perfectly 
  defined. 
  

  

  When 
  this 
  apparatus 
  was 
  put 
  together 
  and 
  air 
  pumped 
  

   into 
  the 
  cylinder 
  it 
  was 
  left 
  intact 
  for 
  a 
  period 
  of 
  over 
  five 
  

   months, 
  and 
  at 
  intervals 
  during 
  this 
  time 
  sets 
  of 
  readings 
  on 
  

   the 
  current 
  between 
  CD 
  and 
  PQ 
  were 
  taken 
  with 
  series 
  of 
  

   gradually 
  increasing 
  potentials 
  both 
  positive 
  and 
  negative 
  

   applied 
  to 
  GH. 
  Throughout 
  the 
  whole 
  of 
  this 
  period 
  the 
  

   currents 
  for 
  selected 
  fields 
  up 
  to 
  about 
  750 
  volts 
  remained 
  

   practically 
  the 
  same, 
  which 
  showed, 
  since 
  the 
  intensity 
  of 
  

   the 
  radiation 
  from 
  the 
  polonium 
  must 
  have 
  diminished 
  by 
  

   over 
  one 
  half 
  in 
  this 
  time, 
  that 
  the 
  current 
  was 
  independent 
  

   of 
  any 
  variations 
  which 
  took 
  place 
  in 
  the 
  ionization 
  layer. 
  

  

  For 
  such 
  a 
  case 
  as 
  this 
  Rutherford 
  * 
  and 
  Child 
  f 
  have 
  

   shown 
  that 
  the 
  mobilities 
  of 
  the 
  ions 
  (expressed 
  in 
  electro- 
  

   static 
  units) 
  taking 
  part 
  in 
  the 
  conduction 
  may 
  be 
  deduced 
  

   from 
  the 
  relation 
  

  

  , 
  _ 
  32 
  . 
  7r 
  .d 
  z 
  . 
  i 
  ^ 
  N 
  

  

  k 
  — 
  9y2 
  v. 
  1 
  / 
  

  

  where 
  i 
  is 
  the 
  current 
  per 
  sq. 
  cm. 
  cross-section, 
  d 
  the 
  distance 
  

   and 
  V 
  the 
  potential 
  difference 
  between 
  the 
  electrodes. 
  

  

  If 
  practical 
  electromagnetic 
  units 
  be 
  used 
  the 
  mobility 
  is 
  

  

  * 
  Rutherford, 
  Phvs. 
  Eev. 
  vol. 
  xiii. 
  (6) 
  p. 
  321 
  (1901). 
  

   t 
  Child, 
  Phy's. 
  Rev. 
  vol. 
  xii. 
  (3) 
  p. 
  137 
  (1901). 
  

  

  