﻿116 
  Mr. 
  C. 
  A. 
  Sadler 
  on 
  tJie 
  

  

  From 
  these 
  results 
  it 
  will 
  be 
  seen 
  that 
  the 
  penetrating 
  

   power 
  of 
  the 
  tertiary 
  radiations 
  is 
  uninfluenced, 
  so 
  far 
  as 
  can 
  

   be 
  measured, 
  by 
  variations 
  in 
  the 
  penetrating 
  power 
  of 
  the 
  

   exciting 
  secondary 
  beams; 
  they 
  further 
  show 
  that 
  if 
  any 
  

   secondary 
  radiation 
  is 
  scattered 
  by 
  the 
  tertiary 
  radiator, 
  the 
  

   ionization 
  it 
  produces 
  is 
  small 
  compared 
  with 
  that 
  produced 
  

   by 
  the 
  tertiary 
  radiation. 
  

  

  This 
  result 
  is 
  analogous 
  with 
  that 
  obtained 
  with 
  secondary 
  

   beams 
  *. 
  

  

  It 
  has 
  thus 
  been 
  shown 
  that 
  the 
  characteristic 
  tertiary 
  radia- 
  

   tion 
  from 
  iron 
  is 
  identical 
  with 
  the 
  characteristic 
  secondary 
  

   radiation 
  from 
  iron 
  in 
  its 
  penetrating 
  power, 
  its 
  homogeneity, 
  

   and 
  in 
  its 
  independence 
  of 
  variations 
  in 
  the 
  penetrating 
  power 
  

   of 
  the 
  exciting 
  radiation. 
  

  

  Similar 
  results 
  were 
  obtained 
  with 
  copper 
  as 
  a 
  tertiary 
  

   radiator. 
  

  

  Connexion 
  between 
  the 
  Secondary 
  and 
  Tertiary 
  Radiators, 
  

  

  A 
  series 
  of 
  experiments 
  was 
  now 
  undertaken 
  in 
  which 
  the 
  

   several 
  members 
  of 
  the 
  group 
  of 
  metals 
  Cr-Ag 
  were 
  used 
  

   as 
  secondary 
  radiators, 
  the 
  tertiary 
  radiators 
  being 
  also 
  chosen 
  

   from 
  among 
  the 
  earlier 
  members 
  of 
  the 
  same 
  group. 
  

  

  By 
  referring 
  to 
  column 
  1, 
  Table 
  V. 
  it 
  will 
  be 
  seen 
  that 
  the 
  

   absorption 
  coefficients 
  by 
  aluminium 
  of 
  the 
  radiations 
  from 
  

   the 
  metals 
  of 
  this 
  group 
  indicate 
  a 
  wide 
  range 
  of 
  penetrating 
  

   powers, 
  so 
  that 
  it 
  was 
  reasonable 
  to 
  expect 
  that 
  for 
  each 
  

   tertiary 
  radiator 
  there 
  would 
  be 
  at 
  least 
  some 
  secondary 
  

   radiations 
  sufficiently 
  penetrating 
  to 
  cause 
  it 
  to 
  emit 
  its 
  

   characteristic 
  radiation. 
  

  

  The 
  method 
  of 
  experimenting 
  was 
  as 
  follows 
  : 
  — 
  The 
  

   secondary 
  radiators 
  successively 
  placed 
  in 
  the 
  position 
  Rj 
  

   (see 
  fig. 
  1) 
  were 
  subjected 
  to 
  the 
  primary 
  rays 
  proceeding 
  

   from 
  the 
  anticathode 
  A, 
  Rg 
  being 
  temporarily 
  removed. 
  

   The 
  ratio 
  of 
  the 
  deflexions 
  of 
  the 
  gold-leaves 
  in 
  the 
  electro- 
  

   scopes 
  E2 
  and 
  El 
  obtained 
  from 
  the 
  microscope 
  readings 
  

   was 
  determined 
  in 
  the 
  case 
  of 
  each 
  radiator 
  ; 
  let 
  ^i 
  be 
  the 
  

   value 
  of 
  this 
  ratio 
  and 
  ri 
  be 
  the 
  value 
  of 
  the 
  ratio 
  with 
  no 
  

   metallic 
  radiator 
  in 
  the 
  position 
  Rj, 
  the 
  air 
  in 
  its 
  neighbour- 
  

   hood 
  acting 
  as 
  a 
  source 
  of 
  secondary 
  radiation. 
  

  

  Next, 
  the 
  particular 
  tertiary 
  radiator 
  under 
  examination 
  

   was 
  placed 
  in 
  the 
  position 
  R2 
  (^-s 
  previously 
  defined), 
  and 
  

   the 
  secondary 
  radiators 
  were 
  again 
  in 
  turn 
  subjected 
  to 
  

   the 
  primary 
  rays. 
  Ionization 
  was 
  now 
  produced 
  in 
  the 
  

   chamber 
  I 
  and 
  deflexions 
  of 
  the 
  gold-leaf 
  in 
  electroscope 
  E3 
  

  

  * 
  Barkla 
  & 
  Sadler, 
  Phil. 
  Mag. 
  Oct. 
  1908, 
  pp. 
  oo0-o84. 
  

  

  