﻿614 
  Dr. 
  J. 
  A. 
  Gray 
  on 
  the 
  Scattering 
  and 
  

  

  Table 
  I. 
  

   Angle 
  of 
  scattermo- 
  50°. 
  

  

  (a) 
  Intensity 
  of 
  primary 
  rays, 
  100. 
  Lead 
  L 
  IS 
  0*0 
  mm. 
  

   Intensity 
  of 
  scattered 
  rays. 
  

  

  Thickness 
  of 
  lead 
  M. 
  

  

  Carbon 
  . 
  

  

  Iron. 
  

  

  Lead. 
  

  

  o-o 
  

  

  5-40 
  

   361 
  

   2-39 
  

   1-54 
  

   092 
  

   0-48 
  

  

  4-90 
  

   3-50 
  

   2-35 
  

   1-50 
  

  

  1-64 
  

   1-31 
  

  

  1-00 
  

   0-72 
  

  

  1-0 
  

  

  30 
  

  

  60 
  

  

  10-0 
  

  

  150 
  

  

  

  (6) 
  Intensity 
  of 
  primary 
  rays, 
  42*4. 
  Lead 
  L 
  1? 
  1*29 
  cm. 
  

   Intensity 
  of 
  scattered 
  rays. 
  

  

  Thickness 
  of 
  lead 
  M. 
  

  

  Carbon. 
  

  

  Iron. 
  Lead. 
  

  

  00 
  

  

  1-93 
  

   1-36 
  

  

  0-67 
  

  

  1-80 
  

   1-32 
  

   0-64 
  

  

  0-70 
  

   0-60 
  

   0-35 
  

  

  1-0 
  

  

  60 
  

  

  

  (c) 
  Intensity 
  of 
  primary 
  rays, 
  23*0. 
  Lead 
  L 
  

   Intensity 
  of 
  scatterec 
  

  

  , 
  2-58 
  cm. 
  

   rays. 
  

  

  Thickness 
  of 
  lead 
  M. 
  

  

  Carbon. 
  

  

  Iron. 
  

  

  Lead. 
  

  

  00 
  

  

  0-85 
  

   0-66 
  

   0-38 
  

  

  0-89 
  

  

  036 
  

  

  1-0 
  

  

  67 
  

  

  

  6-0 
  

  

  0-39 
  

  

  

  

  These 
  figures 
  show 
  at 
  once 
  that 
  the 
  usual 
  explanation 
  of 
  

   the 
  scattering 
  of 
  7 
  rays 
  cannot 
  be 
  quite 
  correct. 
  Take 
  

   Table 
  II. 
  The 
  scattered 
  radiation 
  is 
  reduced 
  to 
  about 
  12 
  

   per 
  cent, 
  of 
  its 
  value 
  by 
  a 
  lead 
  plate 
  3 
  mm. 
  thick. 
  If 
  these 
  

   rays 
  were 
  due 
  to 
  the 
  softer 
  rays 
  being 
  scattered 
  through 
  

   larger 
  angles, 
  we 
  should 
  expect 
  that 
  a 
  lead 
  plate 
  3 
  mm. 
  

   thick 
  placed 
  before 
  the 
  active 
  material 
  would 
  reduce 
  the 
  

   scattered 
  radiation 
  to 
  the 
  same 
  extent. 
  It 
  takes, 
  however, 
  

   over 
  3 
  cm. 
  of 
  lead 
  to 
  do 
  this. 
  Similar 
  results 
  are 
  to 
  be 
  

  

  