﻿526 
  Prof. 
  Wellisch 
  and 
  Dr. 
  Woodrow 
  : 
  Experiments 
  

  

  the 
  point 
  where 
  the 
  curve 
  appears 
  to 
  intersect 
  the 
  axis 
  of 
  

   ordinates. 
  

  

  Taking 
  the 
  straight 
  line 
  DE 
  as 
  the 
  axis, 
  the 
  average 
  of 
  the 
  

   values 
  obtained 
  for 
  Q 
  is 
  82*3, 
  which 
  when 
  reduced 
  to 
  E. 
  S. 
  

   units 
  gives 
  Q 
  o 
  = 
  0*274. 
  Taylor* 
  has 
  determined 
  the 
  total 
  

   number 
  of 
  ions 
  produced 
  by 
  a 
  single 
  alpha 
  particle 
  from 
  

   polonium 
  in 
  air 
  at 
  a 
  pressure 
  of 
  one 
  atmosphere 
  : 
  his 
  calcu- 
  

   lations 
  give 
  this 
  number 
  to 
  be 
  164,000. 
  The 
  ratio 
  of 
  the 
  

   area 
  of 
  that 
  portion 
  of 
  the 
  " 
  Bragg 
  " 
  ionization 
  curve, 
  in- 
  

   cluded 
  between 
  the 
  two 
  ordinates 
  corresponding 
  to 
  distances 
  

   2*4 
  cm. 
  and 
  2'8 
  cm. 
  from 
  the 
  polonium, 
  to 
  the 
  total 
  area 
  

   enclosed 
  by 
  the 
  curve 
  and 
  the 
  axes, 
  was 
  found 
  to 
  be 
  0*112. 
  

   Then 
  each 
  alpha 
  particle 
  will 
  produce 
  0*112x164,000 
  = 
  

   18,368 
  pairs 
  of 
  ions 
  in 
  the 
  ionization 
  vessel 
  employed 
  in 
  

   the 
  experiments 
  described 
  above, 
  where 
  the 
  polonium 
  was 
  

   2'6 
  cm. 
  from 
  the 
  centre 
  of 
  the 
  vessel. 
  Let 
  S 
  be 
  the 
  cross- 
  

   sectional 
  area 
  of 
  a 
  column 
  ; 
  then 
  assuming 
  uniform 
  ionization 
  

   within 
  the 
  column 
  the 
  total 
  charge 
  liberated 
  by 
  a 
  single 
  

   alpha 
  particle 
  in 
  the 
  region 
  considered 
  is 
  

  

  ^ 
  SQ 
  = 
  ^ 
  £=18368 
  X4-65X10" 
  10 
  , 
  

  

  whence 
  

  

  S 
  = 
  8*10xl0- 
  6 
  cm. 
  2 
  

  

  and 
  the 
  radius 
  of 
  the 
  cross-section 
  becomes 
  

  

  R 
  = 
  0*0016cm. 
  

  

  In 
  the 
  application 
  of 
  the 
  theory 
  to 
  C0 
  2 
  , 
  as 
  the 
  saturation 
  

   current 
  could 
  not 
  be 
  obtained 
  experimentally, 
  recourse 
  was 
  

   had 
  to 
  the 
  method 
  described 
  by 
  Langevin 
  f 
  in 
  his 
  original 
  

   paper. 
  The 
  ionization 
  curve 
  for 
  C0 
  2 
  was 
  drawn 
  with 
  

   electric 
  field 
  as 
  abscissae 
  and 
  current 
  as 
  ordinates 
  : 
  the 
  curve 
  

   was 
  then 
  produced 
  to 
  intersect 
  the 
  axis 
  of 
  ordinates. 
  The 
  

   straight 
  line 
  through 
  this 
  point 
  parallel 
  to 
  the 
  X-axis 
  was 
  

   taken 
  as 
  the 
  new 
  axis 
  and 
  the 
  method 
  of 
  Langevin 
  for 
  find- 
  

   ing 
  e 
  was 
  then 
  applied. 
  A 
  large 
  curve 
  given 
  by 
  the 
  equation 
  

  

  y 
  — 
  -log 
  (1+x) 
  was 
  plotted 
  with 
  log 
  (x) 
  as 
  abscissae 
  and 
  

  

  log 
  (y) 
  as 
  ordinates. 
  The 
  value 
  of 
  the 
  current 
  (measured 
  

   from 
  the 
  new 
  axis) 
  for 
  an 
  electric 
  field 
  of 
  1575 
  volts 
  

   per 
  cm. 
  was 
  taken 
  as 
  Q' 
  and 
  then 
  from 
  different 
  values 
  of 
  

   log 
  (Q'/Q) 
  corresponding 
  to 
  values 
  of 
  log 
  (X'/X) 
  = 
  log 
  (a'/o) 
  , 
  

   log 
  (#) 
  and 
  log 
  (y) 
  could 
  be 
  read 
  off 
  on 
  this 
  curve. 
  The 
  

  

  * 
  Taylor, 
  Phil. 
  Ma<y. 
  [6] 
  xxiii. 
  p. 
  670 
  (1912). 
  

  

  t 
  Langevin, 
  Ann. 
  Chim. 
  Phys. 
  [7] 
  xxviii. 
  p. 
  458 
  (1903). 
  

  

  