﻿Scattering 
  of 
  the 
  yS 
  Rays 
  of 
  Radium, 
  911 
  

  

  To 
  obtain 
  a 
  measure 
  of 
  the 
  returned, 
  or 
  incident, 
  scattered 
  

   radiation 
  the 
  apparatus 
  shown 
  in 
  fig. 
  2 
  was 
  used. 
  

  

  Fi?. 
  2. 
  

  

  ToEsrIh 
  

  

  To 
  Elec/rome/ef. 
  

  

  ^ 
  ToS^/^Mry, 
  

  

  ToSarU] 
  

  

  ToEledrdtneref 
  

  

  The 
  top 
  chamber, 
  A, 
  ^Yas 
  the 
  one 
  ah-eady 
  described, 
  and 
  

   a 
  similar 
  hemispherical 
  chamber, 
  B, 
  was 
  placed 
  as 
  shown 
  

   with 
  the 
  Ra 
  outside, 
  contained 
  in 
  a 
  Pb 
  block 
  provided 
  with 
  

   an 
  opening 
  through 
  which 
  the 
  /3 
  rays 
  could 
  pass, 
  impinging 
  

   on 
  screens 
  placed 
  in 
  the 
  position 
  C. 
  A 
  stronger 
  sample 
  of 
  

   Ra, 
  kindly 
  lent 
  by 
  Dr. 
  Hermann 
  Laurence, 
  w^as 
  used 
  in 
  these 
  

   experiments, 
  but 
  care 
  w^as 
  taken 
  to 
  cover 
  it 
  with 
  Cu 
  foil, 
  as 
  

   in 
  the 
  first 
  set 
  of 
  experiments. 
  Either 
  o£ 
  the 
  electrodes 
  A 
  

   or 
  B 
  could 
  be 
  connected 
  to 
  the 
  electrometer, 
  and 
  as 
  the 
  

   chambers 
  were 
  made 
  as 
  nearly 
  as 
  possible 
  alike 
  no 
  appreci- 
  

   able 
  change 
  in 
  capacity 
  was 
  introduced, 
  using 
  either 
  chamber 
  

   separately. 
  It 
  was 
  necessary 
  to 
  use 
  a 
  balance 
  chamber, 
  as 
  

   the 
  initial 
  effect 
  was 
  so 
  large 
  compared 
  with 
  that 
  which 
  was 
  

   to 
  be 
  measured. 
  By 
  placing 
  a 
  thin 
  Al 
  foil 
  at 
  C 
  and 
  then 
  a 
  

   thick 
  Pb 
  plate, 
  a 
  measure 
  was 
  obtained 
  of 
  the 
  incident 
  and 
  

   of 
  the 
  maximum 
  return 
  radiation 
  for 
  that 
  substance, 
  from 
  the 
  

   effects 
  measured 
  separately 
  in 
  the 
  chambers 
  A 
  and 
  B. 
  This 
  

   enabled 
  the 
  readings 
  for 
  the 
  incident 
  scattered 
  radiation 
  to 
  

   be 
  reduced 
  to 
  their 
  correct 
  values 
  relatively 
  to 
  those 
  of 
  the 
  

   emergent 
  rays, 
  using 
  the 
  maximum 
  return 
  radiation 
  from 
  

   Pb 
  as 
  a 
  standard 
  of 
  reference. 
  

  

  