﻿382 
  Mr. 
  H. 
  P. 
  Walmsley 
  on 
  the 
  Distribution 
  of 
  the 
  

  

  investigators 
  had 
  taken 
  no 
  special 
  precautions 
  to 
  procure 
  

   these 
  conditions. 
  His 
  results 
  differed 
  slightly 
  in 
  detail 
  from 
  

   those 
  of 
  Russ, 
  but 
  on 
  the 
  whole 
  he 
  obtained 
  similar 
  effects. 
  

   Two 
  hypotheses 
  have 
  been 
  put 
  forward 
  to 
  explain 
  these 
  

   results, 
  viz. 
  (1), 
  that 
  the 
  deposit 
  atom 
  becomes 
  charged 
  in 
  

   the 
  process 
  of 
  its 
  creation, 
  and 
  subsequently 
  is 
  subjected 
  to 
  

   the 
  chances 
  of 
  recombination 
  like 
  a 
  positive 
  ion 
  ; 
  and 
  (2) 
  , 
  that 
  

   initially 
  the 
  deposit 
  atom 
  is 
  uncharged, 
  and 
  that 
  later 
  it 
  

   acquires 
  a 
  charge 
  by 
  combination 
  with 
  positive 
  or 
  possibly 
  

   negative 
  ions. 
  

  

  Since 
  these 
  results 
  were 
  published, 
  a 
  short-lived 
  a-ray 
  

   product 
  has 
  been 
  discovered 
  in 
  the 
  active 
  deposits 
  of 
  both 
  

   thorium 
  and 
  actinium, 
  following 
  immediately 
  after 
  the 
  ema- 
  

   nations. 
  The 
  successive 
  changes 
  which 
  actinium 
  emanation 
  

   undergoes, 
  as 
  far 
  as 
  is 
  at 
  present 
  known, 
  can 
  be 
  illustrated 
  in 
  

   the 
  following 
  way 
  : 
  — 
  

  

  Emanation 
  a 
  

  

  3-9 
  0-002 
  

  

  SECONDS 
  I 
  SECONDS 
  

  

  Active 
  Deposit 
  

  

  Geiger* 
  has 
  shown 
  that 
  actinium 
  A 
  carries 
  a 
  positive 
  

   charge, 
  and 
  is 
  concentrated 
  on 
  the 
  cathode. 
  It 
  is 
  possible, 
  

   therefore, 
  that 
  the 
  distribution 
  of 
  the 
  active 
  deposit 
  in 
  an 
  

   electric 
  field 
  may 
  depend 
  solely 
  on 
  the 
  charge 
  of 
  actinium 
  A.. 
  

   If, 
  when 
  drawn 
  on 
  the 
  cathode, 
  it 
  transforms 
  there, 
  we 
  have 
  

   an 
  explanation 
  of 
  the 
  high 
  percentage 
  cathode 
  activity. 
  No 
  

   evidence 
  is 
  available 
  as 
  regards 
  the 
  electrification 
  of 
  the 
  sub- 
  

   sequent 
  products. 
  If 
  actinium 
  B 
  were 
  uncharged 
  it 
  would 
  

   diffuse 
  to 
  both 
  anode 
  and 
  cathode, 
  so 
  that 
  the 
  anode 
  activitv 
  

   might 
  be 
  attributed 
  to 
  transformations 
  occurring 
  before 
  the 
  

   first 
  quick-period 
  product 
  was 
  all 
  collected 
  on 
  the 
  cathode. 
  

   The 
  following 
  investigations 
  were 
  undertaken 
  with 
  a 
  view 
  to 
  

   obtain 
  more 
  information 
  on 
  these 
  points. 
  

  

  It 
  is 
  necessary 
  in 
  this 
  type 
  of 
  experiment 
  to 
  introduce 
  

   " 
  pure 
  " 
  emanation 
  into 
  the 
  electric 
  fields 
  employed, 
  i. 
  e. 
  

   emanation 
  free 
  from 
  dust 
  and 
  active 
  deposit. 
  If 
  any 
  changes 
  

   occur 
  at 
  all 
  in 
  the 
  electrification 
  of 
  the 
  active 
  deposit, 
  it 
  is 
  

  

  * 
  Geiger, 
  Phil. 
  Mag. 
  xxii. 
  p. 
  201 
  (1911). 
  

  

  