﻿Investigation 
  of 
  the 
  Nature 
  ofy 
  Rays. 
  933 
  

  

  §n. 
  

  

  We 
  may 
  now 
  give 
  a 
  short 
  summary 
  of 
  the 
  results 
  of 
  this 
  

   and 
  our 
  previous 
  paper 
  : 
  — 
  

  

  (1) 
  When 
  y 
  radiation 
  is 
  diminished 
  in 
  quantity 
  in 
  con- 
  

  

  sequence 
  of 
  its 
  passage 
  through 
  matter, 
  ft 
  radiation 
  

   appears 
  in 
  its 
  place, 
  moving 
  at 
  the 
  outset 
  in 
  the 
  

   original 
  direction 
  of 
  the 
  y 
  radiation, 
  and 
  subsequently 
  

   undero'oino- 
  scattering 
  in 
  the 
  ordinary 
  manner 
  of 
  ft 
  

  

  COO 
  J 
  ' 
  

  

  rays. 
  

  

  (2) 
  The 
  speed 
  and 
  penetration 
  of 
  the 
  ft 
  radiation 
  thus 
  

  

  produced 
  increase 
  with 
  the 
  penetration 
  of 
  the 
  y 
  

   radiation 
  to 
  which 
  it 
  is 
  due. 
  

  

  (3) 
  The 
  speed 
  of 
  the 
  ft 
  radiation 
  does 
  not 
  depend 
  on 
  the 
  

  

  nature 
  or 
  condition 
  of 
  the 
  atom 
  in 
  which 
  it 
  arises. 
  

   (I) 
  In 
  the 
  case 
  of 
  radium 
  the 
  speed 
  of 
  the 
  ft 
  radiation 
  

   produced 
  is 
  nearly 
  equal 
  to 
  the 
  speed 
  of 
  the 
  ft 
  rays 
  

   emitted 
  by 
  radium 
  itself. 
  In 
  the 
  case 
  of 
  uranium, 
  

   thorium, 
  and 
  actinium 
  there 
  are 
  indications 
  that 
  the 
  

   law 
  holds 
  good 
  also, 
  but 
  no 
  exact 
  measurements 
  have 
  

   yet 
  been 
  made. 
  

  

  (5) 
  When 
  very 
  hard 
  7 
  rays 
  traverse 
  matter 
  the 
  absorption 
  

  

  and 
  the 
  consequent 
  production 
  of 
  ft 
  rays 
  are 
  almost 
  

   independent 
  of 
  the 
  atomic 
  structure 
  of 
  the 
  matter, 
  and 
  

   a 
  density 
  law 
  follows. 
  Softer 
  rays 
  are 
  affected 
  by 
  

   atomic 
  structure, 
  in 
  that 
  the 
  heavier 
  atoms 
  are 
  more 
  

   absorbent 
  than 
  the 
  lighter, 
  weight 
  for 
  weight 
  ; 
  and 
  

   the 
  softer 
  the 
  rays 
  are 
  the 
  more 
  prominent 
  this 
  effect 
  

   becomes. 
  

  

  (6) 
  If 
  there 
  are 
  secondary 
  y 
  rays, 
  the 
  ionization 
  which 
  

   they 
  produce 
  is 
  negligible 
  compared 
  with 
  that 
  pro- 
  

   duced 
  by 
  the 
  secondary 
  ft 
  radiation, 
  at 
  least 
  within 
  a 
  

   moderate 
  distance 
  (say 
  100 
  cm. 
  of 
  air) 
  of 
  the 
  radiator. 
  

  

  §in. 
  

  

  Various 
  hypotheses 
  have 
  been 
  suggested 
  as 
  to 
  the 
  mode 
  in 
  

   which 
  the 
  secondary 
  ft 
  radiation 
  is 
  produced 
  by 
  the 
  inter- 
  

   action 
  of 
  the 
  7 
  (or 
  X-) 
  ray 
  and 
  the 
  atom. 
  It 
  is 
  convenient 
  

   to 
  divide 
  them 
  into 
  three 
  classes, 
  and 
  to 
  consider 
  to 
  what 
  

   extent 
  each 
  class 
  is 
  able 
  to 
  furnish 
  an 
  explanation 
  of 
  the 
  

   properties 
  set 
  out 
  in 
  the 
  summary 
  just 
  given. 
  

  

  To 
  the 
  first 
  class 
  belong 
  those 
  hvpotheses 
  which 
  suppose 
  

   both 
  the 
  energy 
  and 
  the 
  material 
  of 
  the 
  ft 
  radiation 
  to 
  be 
  

   furnished 
  by 
  the 
  atom 
  alone 
  : 
  the 
  y 
  ray 
  is 
  a 
  pulse 
  which 
  

   merely 
  pulls 
  the 
  trigger. 
  In 
  its 
  most 
  recent 
  form 
  this 
  idea 
  

  

  