﻿114 
  Mr. 
  C. 
  A. 
  Sadler 
  on 
  the 
  

  

  The 
  results 
  are 
  tabulated 
  below 
  : 
  — 
  

  

  Table 
  II. 
  

   Iron 
  as 
  Tertiary 
  Radiator 
  ; 
  Copper 
  as 
  Secondary 
  Radiator. 
  

  

  Amount 
  previously 
  

   absorbed 
  by 
  Aluuiinium. 
  

  

  Subsequent 
  absorption 
  

  

  by 
  a 
  sheet 
  of 
  Al 
  (00297) 
  

  

  cm, 
  thick. 
  

  

  None. 
  

   55 
  6 
  per 
  cent. 
  

   80-3 
  „ 
  

   940 
  „ 
  

  

  55'6 
  per 
  cent. 
  

   55-7 
  „ 
  

   55-5 
  „ 
  

   550 
  „ 
  

  

  Previous 
  experiments 
  have 
  shown 
  that 
  associated 
  with 
  the 
  

   homogeneous 
  secondary 
  radiation 
  from 
  a 
  metal 
  of 
  the 
  group 
  

   Cr— 
  Ag 
  is 
  a 
  small 
  proportion 
  of 
  scattered 
  radiation, 
  the 
  

   relative 
  ionizations 
  produced 
  by 
  the 
  homogeneous 
  and 
  

   scattered 
  portions 
  being 
  about 
  150 
  : 
  1. 
  

  

  If 
  the 
  secondary 
  beam 
  from 
  iron 
  be 
  absorbed 
  by 
  say 
  

   '0104 
  cm. 
  aluminium, 
  then 
  while 
  the 
  homogeneous 
  portion 
  

   will 
  be 
  absorbed 
  to 
  the 
  extent 
  of 
  about 
  90 
  per 
  cent, 
  the 
  

   scattered 
  portion 
  will 
  only 
  be 
  absorbed 
  by 
  about 
  30 
  per 
  cent., 
  

   giving 
  an 
  absorption 
  of 
  the 
  whole 
  beam 
  of 
  89*6 
  per 
  cent, 
  

   (the 
  absorption 
  being 
  measured 
  by 
  the 
  relative 
  diminution 
  

   in 
  ionization) 
  ; 
  so 
  that 
  the 
  relative 
  ionizations 
  produced 
  by 
  

   the 
  residual 
  homogeneous 
  and 
  scattered 
  portions 
  respectively 
  

   will 
  now 
  be 
  as 
  21*4 
  : 
  1, 
  and 
  a 
  sheet 
  of 
  '0104 
  aluminium 
  would 
  

   now 
  only 
  absorb 
  about 
  87*4 
  per 
  cent, 
  of 
  the 
  whole 
  beam, 
  and 
  

   this 
  increase 
  in 
  penetrating 
  power 
  would 
  become 
  more 
  and 
  

   more 
  pronounced 
  as 
  further 
  absorptions 
  took 
  place. 
  

  

  In 
  a 
  corresponding 
  case 
  of 
  the 
  tertiary 
  beam 
  from 
  iron 
  

   excited 
  by 
  copper 
  radiation, 
  the 
  amount 
  of 
  scattered 
  copper 
  

   radiation 
  in 
  the 
  beam 
  if 
  present 
  at 
  all 
  will 
  not 
  be 
  present 
  to 
  

   so 
  great 
  an 
  extent 
  since 
  the 
  copper 
  radiation 
  will 
  not 
  pene- 
  

   trate 
  to 
  anything 
  like 
  the 
  same 
  depth 
  in 
  the 
  iron 
  as 
  an 
  

   ordinary 
  primary 
  radiation, 
  though 
  on 
  the 
  other 
  hand 
  the 
  

   ionization 
  produced 
  by 
  beams 
  of 
  scattered 
  primary 
  radiation 
  

   and 
  of 
  scattered 
  copper 
  radiation 
  conveying 
  equal 
  amounts 
  

   of 
  energy 
  per 
  second 
  through 
  unit 
  volume 
  of 
  air, 
  will 
  not 
  be 
  

   equal 
  ; 
  the 
  scattered 
  copper 
  radiation 
  being 
  more 
  easily 
  

   absorbed 
  will 
  produce 
  the 
  greater 
  ionization. 
  

  

  No 
  direct 
  evidence 
  has 
  yet 
  been 
  obtained 
  that 
  when 
  the 
  

   normal 
  tertiary 
  radiation 
  from 
  iron 
  is 
  excited 
  by 
  homogeneous 
  

   radiation 
  from 
  copper, 
  any 
  of 
  the 
  coppfer 
  radiation 
  itsfelf 
  is 
  

  

  