﻿Scattering 
  of 
  the 
  ^ 
  Rays 
  of 
  Radium, 
  915 
  

  

  many 
  collisions 
  before 
  emerging, 
  it 
  would 
  appear 
  that 
  the 
  

   loss 
  of 
  energy 
  due 
  to 
  a 
  single 
  collision 
  is 
  as 
  a 
  rule 
  not 
  very 
  

   great, 
  even 
  though 
  the 
  effect 
  of 
  the 
  collision 
  may 
  have 
  pro- 
  

   duced 
  a 
  considerable 
  change 
  in 
  the 
  direction 
  of 
  motion 
  of 
  

   the 
  electron. 
  It 
  is 
  not 
  surprising, 
  then, 
  that 
  some 
  of 
  the 
  

   returned 
  rays 
  have 
  been 
  found 
  to 
  have 
  practically 
  the 
  same 
  

   speed 
  as 
  some 
  of 
  the 
  original 
  rays 
  ; 
  they 
  would 
  appear 
  to 
  be 
  

   electrons 
  which 
  have 
  suffered 
  only 
  one 
  collision 
  of 
  sufficient 
  

   violence 
  to 
  cause 
  them 
  to 
  reverse 
  their 
  original 
  direction 
  of 
  

   motion, 
  or 
  several 
  minor 
  collisions 
  leading 
  to 
  the 
  same 
  result. 
  

   From 
  the 
  curves 
  shown 
  in 
  figs. 
  3 
  and 
  4 
  (PI. 
  XXX.) 
  it 
  is 
  

   seen 
  that 
  for 
  small 
  thicknesses 
  of 
  screen_, 
  before 
  much 
  actual 
  

   absorption 
  has 
  occurred, 
  the 
  number 
  of 
  ^ 
  rays 
  turned 
  back 
  

   may 
  be 
  large, 
  so 
  that 
  many 
  of 
  the 
  original 
  rays 
  w^ould 
  appear 
  

   to 
  lose 
  their 
  energy 
  gradually, 
  rather 
  than 
  by 
  a 
  very 
  sudden 
  

   stoppage 
  and 
  complete 
  absorption. 
  Since 
  the 
  cathode 
  rays 
  

   behave 
  in 
  many 
  respects 
  like 
  the 
  ^ 
  rays, 
  it 
  seems 
  diificult 
  to 
  

   understand 
  how 
  the 
  whole 
  of 
  the 
  energy 
  of 
  the 
  X-rays 
  can 
  

   be 
  derived 
  from 
  the 
  stoppage 
  of 
  the 
  cathode 
  particles,, 
  for, 
  

   as 
  pointed 
  out 
  by 
  Professor 
  Bragg 
  * 
  , 
  the 
  stoppage 
  must 
  be 
  

   very 
  sudden 
  for 
  this 
  to 
  be 
  the 
  case. 
  

  

  Summary. 
  

  

  Experiments 
  with 
  the 
  /S 
  rays 
  of 
  radium 
  support 
  the 
  results 
  

   previously 
  obtained 
  by 
  Crowther, 
  using 
  uranium, 
  upon 
  the 
  

   scattering 
  of 
  the 
  rays 
  by 
  thin 
  films 
  of 
  materials. 
  

  

  The 
  distribution 
  of 
  the 
  scattered 
  /3 
  rays 
  is 
  un 
  symmetrical, 
  

   about 
  a 
  plane 
  of 
  right 
  angles 
  to 
  the 
  direction 
  of 
  the 
  original 
  

   stream. 
  

  

  A 
  close 
  parallel 
  thus 
  exists 
  between 
  the 
  scattering 
  of 
  

   /5 
  rays 
  and 
  that 
  of 
  7 
  and 
  X 
  rays. 
  

  

  The 
  shape 
  of 
  the 
  so-called 
  absorption 
  curve 
  may 
  be 
  modified 
  

   by 
  the 
  shape 
  of 
  the 
  ionization-chamber 
  and 
  the 
  position 
  of 
  

   the 
  screen 
  and 
  active 
  material 
  relatively 
  to 
  the 
  chamber 
  and 
  

   to 
  each 
  other. 
  

  

  Absorption 
  of 
  a 
  beam 
  of 
  /3 
  rays, 
  combined 
  with 
  the 
  effects 
  

   of 
  scattering 
  and 
  softening, 
  seem 
  sufficient 
  to 
  account 
  for 
  

   observed 
  effects 
  without 
  the 
  introduction 
  of 
  the 
  idea 
  of 
  a 
  true 
  

   secondary 
  radiation 
  proceeding 
  from 
  the 
  atoms 
  affected 
  by 
  

   the 
  primary 
  stream 
  of 
  rays. 
  

  

  An 
  electron 
  appears 
  to 
  be 
  able 
  to 
  suffer 
  collisions, 
  producing 
  

   considerable 
  change 
  in 
  its 
  direction 
  of 
  motion, 
  without 
  any 
  

   great 
  loss 
  of 
  energy. 
  

  

  In 
  conclusion, 
  I 
  wish 
  to 
  express 
  my 
  best 
  thanks 
  to 
  Professor 
  

   Bragg 
  for 
  the 
  suggestions 
  he 
  has 
  kindly 
  given 
  me 
  from 
  time 
  

   to 
  time 
  during 
  this 
  investigation. 
  

  

  University 
  of 
  Adelaide, 
  Jan. 
  5, 
  1909. 
  

  

  * 
  Trans. 
  Roy. 
  Soc. 
  S. 
  A. 
  vol. 
  xxxi. 
  (1907), 
  

  

  