﻿Experiments 
  with 
  the 
  Active 
  Deposit 
  of 
  Thorium. 
  361 
  

  

  It 
  is 
  of 
  course 
  just 
  possible 
  that 
  D 
  does 
  not 
  really 
  arise 
  from 
  

   G 
  a 
  , 
  but 
  from 
  C^ 
  or 
  both. 
  This, 
  however, 
  hardly 
  seems 
  

   likely. 
  

  

  From 
  the 
  various 
  experiments 
  we 
  therefore 
  conclude 
  that 
  

   Miss 
  Meitner's 
  experiments 
  do 
  not 
  furnish 
  sufficient 
  evidence 
  

   as 
  to 
  the 
  existence 
  of 
  two 
  separate 
  products 
  of 
  about 
  the 
  same 
  

   period 
  in 
  thorium 
  C, 
  but 
  that 
  it 
  is 
  more 
  probable 
  that 
  there 
  

   are 
  two 
  methods 
  of 
  disintegration 
  possible 
  for 
  the 
  same 
  

   atom 
  . 
  

  

  y 
  Radiation 
  from 
  Thorium 
  B. 
  

  

  In 
  the 
  above 
  experiments 
  on 
  the 
  growth 
  of 
  D 
  from 
  B 
  by 
  

   Miss 
  Meitner's 
  method, 
  it 
  was 
  noticed 
  that 
  when 
  the 
  7-ray 
  

   rise 
  curves 
  were 
  determined 
  through 
  1*6 
  mm. 
  and 
  7 
  mm. 
  

   lead, 
  a 
  difference 
  in 
  the 
  initial 
  percentage 
  activity 
  (of 
  the 
  

   maximum 
  in 
  each 
  case) 
  of 
  about 
  11 
  per 
  cent, 
  was 
  observed, 
  

   the 
  curve 
  in 
  the 
  former 
  case 
  being 
  the 
  higher. 
  This 
  shows 
  

   that 
  soft 
  7 
  rays 
  are 
  emitted 
  from 
  B, 
  and 
  it 
  will 
  be 
  noticed 
  

   that 
  they 
  are 
  very 
  similar 
  as 
  regards 
  penetrating 
  power 
  to 
  

   the 
  7 
  rays 
  from 
  radium 
  B. 
  On 
  account 
  of 
  these 
  soft 
  7 
  rays 
  

   all 
  the 
  measurements 
  of 
  7 
  rays 
  made 
  in 
  the 
  above 
  experiments 
  

   were 
  made 
  through 
  at 
  least 
  7 
  mm. 
  lead. 
  

  

  Further 
  experiments 
  also 
  showed 
  that 
  thorium 
  C 
  emits 
  no 
  

   appreciable 
  quantity 
  of 
  7 
  rays 
  which 
  can 
  penetrate 
  1*6 
  mm. 
  

   lead. 
  The 
  properties 
  of 
  the 
  various 
  7 
  rays 
  are, 
  however, 
  

   being 
  investigated 
  in 
  more 
  detail 
  by 
  Prof. 
  Rutherford 
  and 
  

   Mr. 
  Richardson 
  in 
  this 
  laboratory. 
  

  

  In 
  conclusion, 
  therefore, 
  the 
  following 
  scheme 
  represents 
  

   our 
  present 
  knowledge 
  of 
  the 
  transformations 
  in 
  the 
  active 
  

   deposit 
  of 
  thorium 
  : 
  

  

  A,? 
  

  

  / 
  / 
  // 
  / 
  

  

  Th 
  Em 
  ^Th 
  A 
  — 
  -Th 
  B 
  — 
  -Jh 
  C 
  

  

  53 
  sees. 
  o-f^-secs 
  to-shrs. 
  

  

  *35 
  

  

  65 
  y*( 
  8 
  " 
  6 
  ) 
  

  

  ThC- 
  

  

  '2 
  

   60-5 
  wins. 
  iCT'secs. 
  

  

  We 
  are 
  deeply 
  indebted 
  to 
  Prof. 
  Rutherford 
  for 
  his 
  kind 
  

   encouraging 
  interest 
  in 
  these 
  experiments. 
  

  

  Phil. 
  Mag. 
  S. 
  6. 
  Vol. 
  26. 
  No. 
  152. 
  Aug. 
  1913. 
  2 
  B 
  

  

  