﻿Transformations 
  of 
  X~Rays. 
  

  

  113 
  

  

  The 
  absorption 
  coefficients 
  o£ 
  the 
  tertiary 
  beam 
  from 
  iron 
  

   were 
  then 
  determined 
  bj 
  thin 
  sheets 
  of 
  aluminium, 
  iron, 
  

   copper, 
  and 
  zinc. 
  The 
  values 
  so 
  obtained 
  are 
  compared 
  with 
  

   those 
  obtained 
  when 
  the 
  same 
  absorbers 
  were 
  used 
  with 
  the 
  

   secondary 
  rays 
  in 
  tbe 
  control 
  experiment 
  in 
  the 
  following 
  

   table. 
  

  

  Table 
  I. 
  

  

  Absorber. 
  

  

  Value 
  of 
  - 
  for 
  

  

  Value 
  of 
  ~ 
  for 
  

  

  

  Secondary 
  Eays. 
  

  

  Tertiary 
  Rays. 
  

  

  Al 
  (00297 
  cm.) 
  ... 
  

  

  938 
  

  

  94-2 
  

  

  Fe 
  (-00315 
  cm.) 
  ... 
  

  

  69-1 
  

  

  69-1 
  

  

  Cu 
  (-00298 
  cm.) 
  ... 
  

  

  1010 
  

  

  102-5 
  

  

  Zn 
  (00132 
  cm.) 
  ... 
  

  

  119-2 
  

  

  120-0 
  

  

  It 
  will 
  thus 
  be 
  seen 
  that 
  within 
  the 
  limits 
  of 
  experimental 
  

   errors 
  the 
  penetrating 
  power 
  of 
  the 
  tertiary 
  beam 
  is 
  identical 
  

   with 
  that 
  of 
  a 
  similar 
  secondary 
  beam 
  from 
  the 
  same 
  

   substance. 
  

  

  The 
  Homogeneity 
  of 
  the 
  characteristic 
  Tertiary 
  

   Radiation. 
  

  

  The 
  tertiary 
  beam 
  from 
  iron 
  excited 
  by 
  the 
  secondary 
  

   homogeneous 
  beam 
  from 
  copper 
  was 
  now 
  cut 
  down 
  by 
  thin 
  

   aluminium 
  sheets 
  to 
  test 
  its 
  homogeneity. 
  

  

  It 
  was 
  to 
  be 
  expected, 
  even 
  were 
  the 
  beam 
  perfectly 
  homo- 
  

   geneous, 
  that 
  after 
  cutting 
  down 
  by 
  a 
  few 
  plates 
  the 
  beam 
  

   would 
  appear 
  slightly 
  more 
  penetrating, 
  for 
  the 
  more 
  

   oblique 
  rays 
  would 
  suffer 
  extinction 
  to 
  a 
  greater 
  extent 
  

   than 
  those 
  passing 
  through 
  the 
  absorber 
  in 
  a 
  perpendicular 
  

   direction. 
  

  

  It 
  was 
  not 
  found 
  possible 
  to 
  test 
  for 
  homogeneity 
  to 
  an 
  

   exhaustive 
  limit 
  owing 
  to 
  the 
  smallness 
  of 
  the 
  readings 
  in 
  the 
  

   later 
  stages, 
  but 
  the 
  results 
  obtained 
  show 
  that 
  for 
  all 
  

   practical 
  purposes 
  the 
  beam 
  may 
  be 
  regarded 
  as 
  homo- 
  

   geneous. 
  

  

  Fldl 
  Mag. 
  S. 
  6. 
  Vol. 
  18. 
  No. 
  103. 
  July 
  1909. 
  

  

  I 
  

  

  