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  [ 
  909 
  ] 
  

  

  XCVIII. 
  The 
  Scattering 
  of 
  the 
  /3 
  Rays 
  of 
  Radium. 
  Bij 
  

   J. 
  P.y. 
  Madsen, 
  B.'Sc. 
  {Adel^j, 
  B.E. 
  (Si/d.), 
  Lecturer 
  in 
  

   Electrical 
  Engineering^ 
  Univerity 
  of 
  Adelaide'^. 
  

  

  [Plate 
  XXX.] 
  

  

  § 
  I. 
  Introductory. 
  

  

  N 
  a 
  paper 
  bj 
  the 
  author 
  upon 
  the 
  secondary 
  7 
  rays 
  f 
  it 
  

   was 
  shown 
  that 
  in 
  passing 
  through 
  matter 
  the 
  7 
  rays 
  

   were 
  scattered 
  and 
  softened. 
  The 
  scattered 
  radiation 
  showed 
  

   a 
  distinct 
  lack 
  of 
  symmetry 
  about 
  a 
  plane 
  perpendicular 
  to 
  

   the 
  direction 
  of 
  the 
  original 
  stream, 
  more 
  scattered 
  radiation 
  

   moving 
  on 
  in 
  the 
  direction 
  of 
  the 
  original 
  stream 
  than 
  was 
  

   turned 
  back. 
  The 
  distribution 
  of 
  the 
  scattered 
  radiation 
  was 
  

   found 
  to 
  depend 
  upon 
  the 
  quality 
  of 
  the 
  incident 
  radiation 
  

   and 
  also 
  upon 
  the 
  nature 
  of 
  the 
  medium 
  in 
  which 
  the 
  scattering 
  

   occurred. 
  

  

  As 
  the 
  results 
  arrived 
  at 
  in 
  that 
  investigation 
  were 
  used 
  

   as 
  an 
  argument 
  in 
  support 
  of 
  the 
  material 
  theory 
  of 
  7 
  rays' 
  

   proposed 
  by 
  Bragg, 
  and 
  as 
  Crowther 
  J 
  has 
  recently 
  shown 
  

   that 
  the 
  ^ 
  rays 
  are 
  subject 
  to 
  scattering 
  by 
  even 
  very 
  thin 
  

   layers 
  of 
  material, 
  it 
  became 
  of 
  special 
  interest 
  to 
  see 
  

   whether 
  any 
  parallel 
  could 
  be 
  drawn 
  between 
  the 
  effects 
  of 
  

   scattering 
  in 
  the 
  case 
  of 
  the 
  material 
  /3 
  particles 
  and 
  the 
  

   7 
  rays. 
  

  

  It 
  will 
  be 
  seen 
  from 
  the 
  present 
  paper 
  that 
  the 
  parallel 
  is 
  

   very 
  close 
  in 
  many 
  respects, 
  the 
  differences 
  being 
  such 
  as 
  

   might 
  reasonably 
  be 
  expected 
  on 
  the 
  theory 
  that 
  the 
  7 
  ray 
  is 
  

   a 
  neutral 
  pair. 
  

  

  At 
  the 
  same 
  time 
  it 
  is 
  hoped 
  that 
  some 
  of 
  the 
  results 
  to 
  be 
  

   described 
  may 
  help 
  to 
  clear 
  up 
  some 
  of 
  the 
  difficulties 
  which 
  

   have 
  arisen 
  in 
  the 
  study 
  of 
  the 
  absorption 
  of 
  ^ 
  rays. 
  

  

  § 
  II. 
  Apparatus. 
  

  

  The 
  apparatus 
  used 
  in 
  these 
  experiments 
  is 
  shown 
  in 
  fig. 
  1. 
  

   The 
  radium 
  contained 
  in 
  a 
  small 
  conical 
  hole 
  cut 
  in 
  a 
  piece 
  

   of 
  Al 
  was 
  covered 
  by 
  a 
  sheet 
  of 
  Cu 
  foil 
  '002 
  cm. 
  thick. 
  The 
  

   /3 
  rays 
  passed 
  up 
  through 
  a 
  conical 
  hole 
  cut 
  in 
  a 
  block 
  of 
  

  

  * 
  Communicated 
  by 
  the 
  Author. 
  From 
  ' 
  Transactions 
  of 
  the 
  Royal 
  

   Society 
  of 
  South 
  Australia/ 
  vol. 
  xxxiii. 
  1909. 
  Preliminary 
  Account 
  

   read 
  before 
  the 
  Australasian 
  Association 
  for 
  the 
  Advancement 
  of 
  

   Science, 
  Brisbane, 
  January 
  13, 
  1909. 
  

  

  t 
  Trans. 
  Ptoy. 
  Soc. 
  S.A. 
  vol. 
  xxxii. 
  (1908). 
  

  

  t 
  Proc. 
  Roy. 
  Soc, 
  A, 
  vol. 
  Ixxx. 
  (1908). 
  

  

  