﻿and 
  Act 
  ice 
  Deposit 
  from 
  Thorium 
  and 
  Actinium, 
  

   Table 
  I. 
  

  

  Time. 
  

  

  

  

  Activities. 
  

  

  

  

  1 
  Th. 
  Emanation 
  

   1 
  4- 
  Active 
  Deposit. 
  

  

  Active 
  

   Deposit. 
  

  

  Calc. 
  Max. 
  of 
  

   Active 
  Deposit. 
  

  

  Emanation. 
  

  

  Eatio. 
  

  

  

  

  731 
  

  

  

  

  731 
  

  

  

  38 
  

  

  960 
  

  

  248 
  

  

  271 
  

  

  712 
  

  

  •38 
  

  

  45 
  

  

  962 
  

  

  255 
  

  

  269 
  

  

  707 
  

  

  •38 
  

  

  62 
  

  

  990 
  

  

  265 
  

  

  270 
  

  

  725 
  

  

  •37 
  

  

  72 
  

  

  945 
  

  

  260 
  

  

  262 
  

  

  685 
  

  

  •38 
  

  

  87 
  

  

  975 
  

  

  1 
  

  

  263 
  

  

  264 
  

  

  711 
  

  

  •37 
  

  

  measurements 
  were 
  continued 
  for 
  10 
  consecutive 
  days. 
  A 
  

   sim'lar 
  set 
  of 
  observations 
  was 
  taken 
  with 
  the 
  smaller 
  testing- 
  

   vessel. 
  The 
  experiments 
  with 
  actinium 
  required 
  much 
  less 
  

   time, 
  because 
  the 
  transformation 
  period 
  of 
  its 
  active 
  deposit 
  

   is 
  much 
  shorter 
  than 
  that 
  of 
  thorium. 
  In 
  the 
  case 
  of 
  actinium 
  

   also 
  the 
  experimental 
  conditions 
  were 
  varied 
  as 
  much 
  as 
  

   possible. 
  As 
  would 
  be 
  expected, 
  the 
  ratio 
  of 
  the 
  ionization 
  

   due 
  to 
  the 
  active 
  deposit 
  to 
  that 
  due 
  to 
  the 
  emanation 
  was 
  

   affected 
  by 
  the 
  size 
  of 
  the 
  vessel 
  and 
  the 
  location 
  of 
  the 
  

   active 
  deposit. 
  None 
  of 
  the 
  other 
  changes 
  in 
  the 
  experi- 
  

   mental 
  condition 
  affected 
  this 
  ratio 
  more 
  than 
  a 
  few 
  per 
  cent. 
  

   Most 
  of 
  these 
  variations 
  could 
  probably 
  be 
  removed 
  by 
  

   sufficient 
  care, 
  but 
  this 
  was 
  unnecessary 
  for 
  the 
  purpose 
  of 
  

   the 
  present 
  paper, 
  as 
  the 
  accuracy 
  of 
  the 
  measurements 
  is 
  

   quite 
  as 
  great 
  as 
  that 
  of 
  the 
  assumptions 
  on 
  which 
  the 
  

   calculations 
  are 
  based. 
  

  

  Now 
  Hahn 
  (Phil. 
  Mag. 
  June 
  and 
  July 
  1906) 
  has 
  shown 
  

   that 
  the 
  active 
  deposit 
  from 
  thorium 
  contains 
  two 
  a. 
  ray 
  

   products, 
  thorium 
  B 
  and 
  thorium 
  C, 
  and 
  that 
  the 
  maximum 
  

   ranges 
  of 
  their 
  a. 
  particles 
  in 
  air 
  are 
  5'0 
  and 
  8'6 
  cms. 
  respec- 
  

   tively. 
  He 
  has 
  also 
  shown 
  that 
  the 
  a 
  rays 
  from 
  these 
  two 
  

   products 
  produce 
  about 
  the 
  same 
  number 
  of 
  ions 
  per 
  cm. 
  of 
  

   path. 
  Now 
  if 
  the 
  a 
  particle 
  from 
  thorium 
  emanation, 
  which 
  

   has 
  a 
  range 
  in 
  air 
  of 
  5"5 
  cms., 
  is 
  similar 
  to 
  those 
  from 
  

   thorium 
  B 
  and 
  thorium 
  C, 
  and 
  if 
  it 
  produces 
  the 
  same 
  

   number 
  of 
  ions 
  per 
  cm. 
  (when 
  it 
  has 
  the 
  same 
  velocity), 
  

   then 
  we 
  should 
  expect 
  that 
  the 
  ionization 
  produced 
  by 
  the 
  

   active 
  deposit 
  would 
  certainly 
  be 
  greater 
  than 
  that 
  produced 
  

   by 
  the 
  emanation. 
  The 
  exact 
  value 
  of 
  the 
  ratio 
  would, 
  of 
  

   course, 
  depend 
  upon 
  the 
  mean 
  free 
  paths 
  and 
  the 
  velocities 
  

   of 
  the 
  different 
  a 
  particles 
  in 
  the 
  given 
  vessel. 
  The 
  results 
  

   given 
  in 
  Table 
  I. 
  show 
  that 
  the 
  ionization 
  due 
  to 
  the 
  active 
  

  

  