﻿894 
  Conductivity 
  imparted 
  to 
  Liquid 
  Air 
  by 
  Alpha 
  Rays. 
  

  

  was 
  not 
  suitable 
  for 
  testing 
  whether 
  this 
  radiation 
  was 
  

   magnetically 
  deflectable 
  or 
  not, 
  but 
  in 
  view 
  o£ 
  the 
  experi- 
  

   ments 
  of 
  Chadwick 
  *, 
  which 
  show 
  that 
  gamma 
  rays 
  are 
  

   produced 
  by 
  alpha 
  rays 
  in 
  certain 
  circumstances, 
  the 
  results 
  

   would 
  seem 
  to 
  point 
  to 
  the 
  existence 
  of 
  gamma 
  rays 
  accom- 
  

   panying 
  the 
  alpha 
  rays 
  from 
  polonium. 
  The 
  probability 
  

   of 
  this 
  conclusion 
  being 
  correct 
  is 
  increased 
  when 
  it 
  is 
  

   remembered 
  that 
  the 
  experiments 
  were 
  made 
  with 
  a 
  layer 
  

   of 
  polonium 
  which 
  had 
  been 
  deposited 
  on 
  tbe 
  copper 
  plate 
  

   PQ 
  about 
  nine 
  months 
  previously. 
  This 
  interval 
  should 
  

   have 
  been 
  sufficient 
  for 
  any 
  beta-ray 
  product 
  to 
  have 
  died 
  

   out 
  which 
  with 
  any 
  likelihood 
  might 
  have 
  originally 
  con- 
  

   taminated 
  the 
  polonium 
  deposit. 
  

  

  VIII. 
  Summary 
  of 
  Results. 
  

  

  (1) 
  In 
  a 
  number 
  of 
  experiments 
  it 
  has 
  been 
  shown, 
  in 
  

   agreement 
  with 
  a 
  number 
  of 
  other 
  experimenters, 
  that 
  liquid 
  

   air 
  when 
  freshly 
  filtered 
  is 
  an 
  extremely 
  good 
  insulator, 
  and 
  

   that 
  its 
  conductivity 
  in 
  the 
  absence 
  of 
  any 
  ionizing 
  radiation 
  

   other 
  than 
  that 
  from 
  the 
  earth 
  is 
  much 
  the 
  same 
  as 
  that 
  of 
  

   ordinary 
  clean 
  air 
  at 
  atmospheric 
  pressure. 
  

  

  (2) 
  The 
  dielectric 
  constant 
  of 
  liquid 
  air 
  was 
  found 
  to 
  

   be 
  1-43. 
  

  

  (3) 
  The 
  saturation-current 
  obtained 
  in 
  air 
  at 
  ordinary 
  

   pressure 
  by 
  the 
  complete 
  absorption 
  of 
  the 
  alpha 
  radiation 
  

   emitted 
  by 
  a 
  plate 
  coated 
  with 
  polonium, 
  was 
  found 
  to 
  be 
  

   about 
  16 
  times 
  the 
  maximum 
  current 
  obtained 
  with 
  the 
  

   highest 
  fields 
  used 
  when 
  the 
  radiation 
  was 
  absorbed 
  in 
  air 
  at 
  

   101 
  atmospheres, 
  and 
  about 
  576 
  times 
  the 
  maximum 
  current 
  

   obtained 
  in 
  liquid 
  air 
  when 
  the 
  ionization 
  was 
  produced 
  by 
  

   the 
  same 
  radiation. 
  

  

  (4) 
  The 
  mobility 
  of 
  the 
  positive 
  ion 
  produced 
  in 
  air 
  at 
  

   116 
  atmospheres 
  by 
  alpha 
  rays 
  was 
  found 
  to 
  be 
  0'0005294 
  

   cm. 
  sec. 
  per 
  volt 
  cm. 
  and 
  that 
  of 
  the 
  negative 
  0*0006217 
  cm. 
  

   sec. 
  per 
  volt 
  cm., 
  the 
  latter 
  being 
  about 
  P18 
  times 
  the 
  former. 
  

  

  (5) 
  Evidence 
  has 
  been 
  found 
  in 
  the 
  course 
  of 
  the 
  investi- 
  

   gation 
  of 
  the 
  existence 
  of 
  a 
  penetrating 
  radiation 
  emitted 
  by 
  

   the 
  layer 
  of 
  polonium 
  which 
  furnished 
  the 
  alpha 
  rays. 
  

  

  In 
  conclusion 
  the 
  authors 
  wish 
  to 
  acknowledge 
  the 
  kindness 
  

   of 
  Prof. 
  H. 
  A. 
  Dawes 
  and 
  Mr. 
  P. 
  Blackman 
  who 
  assisted 
  in 
  

   taking 
  readings 
  during 
  the 
  course 
  of 
  the 
  investigation. 
  

  

  The 
  Physical 
  Laboratory, 
  

  

  University 
  of 
  Toronto, 
  

  

  June 
  1st, 
  1913. 
  

  

  * 
  Chadwick. 
  Phil. 
  Mag. 
  vol. 
  xxiv. 
  p. 
  494 
  (1912) 
  ; 
  vol. 
  xxv. 
  p. 
  193 
  

   (1913). 
  

  

  