﻿and 
  Active 
  Deposit 
  from 
  Thorium 
  and 
  Actinium. 
  297 
  

  

  In 
  calculating 
  the 
  mean 
  free 
  paths 
  of 
  the 
  « 
  particles 
  from 
  

   the 
  emanation 
  in 
  the 
  smaller 
  vessel, 
  the 
  same 
  method 
  was 
  

   employed, 
  but 
  it 
  was 
  found 
  to 
  be 
  more 
  accurate 
  to 
  take 
  the 
  

   two 
  perpendicular 
  planes 
  through 
  the 
  point 
  in 
  such 
  a 
  way 
  

   that 
  one 
  contained 
  the 
  axis 
  and 
  the 
  other 
  was 
  parallel 
  to 
  it. 
  

   Also 
  in 
  calculating 
  the 
  mean 
  free 
  path 
  of 
  the 
  a 
  particle 
  from 
  

   the 
  active 
  deposit 
  on 
  the 
  inner 
  surface 
  of 
  the 
  smaller 
  cylinder, 
  

   there 
  was 
  such 
  a 
  great 
  difference 
  in 
  the 
  mean 
  free 
  paths 
  in 
  

   the 
  maximum 
  and 
  minimum 
  planes, 
  that 
  it 
  was 
  found 
  necessary 
  

   to 
  take 
  six 
  planes 
  at 
  angles 
  of 
  30° 
  with 
  one 
  another. 
  

  

  The 
  ratios 
  given 
  in 
  column 
  VI. 
  were 
  calculated 
  by 
  taking 
  

   into 
  account 
  the 
  fact 
  that 
  an 
  « 
  particle 
  does 
  not 
  produce 
  the 
  

   same 
  number 
  of 
  ions 
  over 
  each 
  cm. 
  of 
  its 
  path. 
  A 
  curve 
  

   showing 
  the 
  relation 
  between 
  the 
  ionization 
  due 
  to 
  an 
  

   a 
  particle 
  of 
  radium 
  C 
  and 
  the 
  distance 
  from 
  the 
  end 
  of 
  its 
  

   ionizing 
  path, 
  was 
  given 
  by 
  the 
  writer 
  in 
  Phil. 
  Mag. 
  for 
  

   June 
  1906, 
  and 
  is 
  reproduced 
  here. 
  

  

  BOC 
  

  

  700 
  

  

  >0C 
  

  

  50C 
  

  

  <5> 
  tw 
  

  

  | 
  300 
  

  

  200 
  

  

  IOC 
  

  

  i 
  ; 
  J 
  i 
  . 
  : 
  

  

  ' 
  I 
  ' 
  j 
  " 
  i 
  x 
  i 
  I 
  h 
  j 
  

  

  1 
  , 
  , 
  J^ 
  , 
  . 
  

  

  NJ 
  

  

  I 
  1 
  J 
  , 
  X 
  I 
  i 
  

  

  &6 
  3-0 
  3-4 
  3-8 
  4-2 
  4-6 
  5-0 
  5-4 
  5-8 
  6-2 
  

  

  /J/STANCE 
  FROM 
  SOURCE 
  TO 
  TESTING 
  VESSEL 
  JN'CMS. 
  

  

  6-6 
  

  

  70 
  

  

  7-4 
  

  

  This 
  curve 
  gives 
  the 
  ionization 
  for 
  the 
  last 
  4*5 
  cms. 
  of 
  the 
  

   ionizing 
  path 
  of 
  an 
  a. 
  particle, 
  and 
  can 
  be 
  extrapolated 
  with 
  

   little 
  error 
  to 
  cover 
  the 
  last 
  6 
  cms. 
  of 
  its 
  path. 
  The 
  extra- 
  

   polation 
  of 
  the 
  curve 
  to 
  S'6 
  cms., 
  which 
  is 
  the 
  maximum 
  

   ionizing 
  path 
  of 
  the 
  a 
  particle 
  from 
  thorium 
  C, 
  introduces 
  

   so 
  much 
  uncertainty 
  that 
  the 
  results 
  given 
  in 
  column 
  VI. 
  

  

  Phil. 
  Mag. 
  S. 
  6. 
  Vol. 
  10. 
  Xo. 
  92. 
  Aug. 
  1908. 
  X 
  

  

  