﻿Ti-ansformations 
  of 
  X- 
  Rays. 
  115 
  

  

  scattered 
  by 
  the 
  iron 
  ; 
  its 
  presence 
  in 
  the 
  beam 
  would 
  be 
  

   difficult 
  to 
  detect 
  for 
  a 
  small 
  percentage 
  of 
  copper 
  radiation 
  

   in 
  the 
  beam 
  would 
  produce 
  a 
  very 
  minute 
  change 
  in 
  its 
  

   absorption 
  coefficients. 
  The 
  figures 
  given 
  in 
  Table 
  II. 
  there- 
  

   fore 
  do 
  not 
  preclude 
  the 
  possibility 
  of 
  a 
  small 
  percentage 
  of 
  

   the 
  ionization 
  being 
  due 
  to 
  scattered 
  copper 
  radiation. 
  

  

  Itidependence 
  of 
  the 
  Penetrating 
  Power 
  of 
  the 
  

   Exciting 
  Radiation. 
  

  

  Experiments 
  were 
  made 
  to 
  test 
  whether 
  the 
  penetrating 
  

   power 
  of 
  the 
  tertiary 
  radiation 
  emitted 
  by 
  a 
  substance 
  

   depended 
  in 
  any 
  way 
  upon 
  the 
  penetrating 
  power 
  of 
  the 
  

   exciting 
  secondary 
  beams. 
  In 
  the 
  first 
  test, 
  iron 
  was 
  chosen 
  

   as 
  the 
  tertiary 
  radiator, 
  copper 
  and 
  arsenic 
  as 
  the 
  secondary 
  

   radiators. 
  The 
  radiation 
  from 
  arsenic 
  being 
  about 
  twice 
  as 
  

   penetrating 
  as 
  that 
  from 
  copper. 
  

  

  In 
  the 
  second 
  test 
  chromium 
  was 
  taken 
  as 
  the 
  tertiary 
  

   radiator, 
  and 
  iron, 
  copper, 
  and 
  arsenic 
  as 
  secondary 
  radiators 
  ; 
  

   the 
  radiations 
  from 
  each 
  of 
  these 
  substances 
  being 
  more 
  pene- 
  

   trating 
  than 
  that 
  from 
  chromium, 
  the 
  radiation 
  from 
  arsenic 
  

   being 
  about 
  four 
  times 
  as 
  penetrating 
  as 
  that 
  from 
  iron. 
  

  

  The 
  results 
  are 
  tabulated 
  below 
  : 
  — 
  

  

  Table 
  III. 
  

   Iron 
  as 
  Tertiary 
  Radiator. 
  

  

  « 
  !„„„ 
  1 
  Absorption 
  coefficient 
  

  

  Secondary 
  ^^^ 
  Secondary 
  Radia- 
  

   Eadiator. 
  tion 
  by 
  Aluminium. 
  

  

  Percentage 
  Absorption 
  

   of 
  the 
  Tertiary 
  Radia- 
  

   tion 
  by 
  (00297 
  cm.) 
  Al. 
  

  

  Copper 
  

  

  128-9 
  

   60-7 
  

  

  55-6 
  

   55-4 
  

  

  Arsenic 
  

  

  

  

  

  Table 
  IV. 
  

   Chromium 
  as 
  Tertiary 
  Radiator. 
  

  

  Secondary 
  

   Eadiator. 
  

  

  Absorption 
  coefficient 
  

   of 
  the 
  Secondary 
  Radia- 
  

   tion 
  by 
  Aluminium. 
  

  

  Percentage 
  absorption 
  

   of 
  the 
  Tertiary 
  Radia- 
  

   tion 
  by 
  (-00297 
  cm.) 
  Al. 
  

  

  Iron 
  

  

  239 
  

   128-9 
  

   60-7 
  

  

  75-1 
  

   75-3 
  

   75-1 
  

  

  Copper 
  

  

  Arsenic 
  

  

  

  12 
  

  

  