﻿Homogeneous 
  Secondary 
  Rontg 
  en 
  Radiatu 
  

  

  557 
  

  

  through 
  the 
  surface 
  layers 
  were 
  of 
  the 
  same 
  character 
  as 
  

   those 
  from 
  the 
  surface 
  layers. 
  Consequently, 
  in 
  dealing 
  

   with 
  these 
  secondary 
  rays 
  it 
  is 
  not 
  necessary 
  as 
  in 
  the 
  

   H 
  — 
  S 
  group 
  to 
  deal 
  with 
  very 
  thin 
  plates 
  in 
  order 
  to 
  

   determine 
  the 
  character 
  of 
  the 
  radiation 
  as 
  emitted 
  by 
  the 
  

   atoms 
  themselves. 
  

  

  Using- 
  zinc 
  as 
  the 
  radiating 
  substance, 
  the 
  direct 
  ionizing 
  

   effect 
  of 
  the 
  secondary 
  rays 
  was 
  determined, 
  and 
  afterward 
  

   the 
  ionization 
  produced 
  by 
  the 
  same 
  beam 
  after 
  transmission 
  

   through 
  thin 
  sheets 
  of 
  zinc 
  and 
  aluminium 
  placed 
  at 
  a 
  

   distance 
  of 
  several 
  centimetres 
  from 
  the 
  detecting 
  electro- 
  

   scope 
  in 
  order 
  to 
  avoid 
  complications 
  due 
  to 
  the 
  more 
  easily 
  

   absorbed 
  corpuscular 
  secondary 
  rays 
  from 
  the 
  metal 
  sheet. 
  

  

  The 
  effect 
  of 
  the 
  radiation 
  from 
  air 
  was 
  determined 
  by 
  

   separate 
  experiments, 
  and 
  correction 
  was 
  then 
  made 
  for 
  this 
  in 
  

   each 
  observation, 
  though 
  when 
  a 
  large 
  proportion 
  of 
  the 
  

   secondary 
  rays 
  was 
  absorbed, 
  the 
  air 
  radiation 
  was 
  quite 
  a 
  

   considerable 
  fraction 
  of 
  the 
  whole 
  and 
  the 
  possible 
  error 
  was 
  

   as 
  a 
  consequence 
  greatly 
  increased. 
  

  

  Below 
  are 
  tabulated 
  the 
  percentage 
  absorptions 
  by 
  a 
  plate- 
  

   of 
  zinc 
  '00131 
  cm. 
  thick 
  and 
  one 
  of 
  aluminium 
  "0104 
  cm. 
  

   thick 
  of 
  the 
  secondary 
  beam 
  direct 
  from 
  zinc 
  and 
  of 
  this 
  beam 
  

   after 
  transmission 
  through 
  various 
  thicknesses 
  of 
  aluminium. 
  

   These 
  results 
  exhibit 
  the 
  striking 
  homogeneity 
  of 
  the 
  radiation 
  

   from 
  zinc. 
  

  

  Table 
  I. 
  

  

  Radiation 
  from 
  Zinc 
  (thick 
  

  

  sheet) 
  . 
  

  

  I. 
  

  

  Percentage 
  Absorption 
  

  

  by 
  Al 
  

   previous 
  to 
  absorption 
  

   in 
  column 
  II. 
  or 
  III. 
  

  

  II. 
  

  

  Percentage 
  Absorption 
  

  

  by 
  Zn 
  (-00131 
  cm.) 
  

  

  after 
  absorption 
  

  

  in 
  column 
  I. 
  

  

  III. 
  

  

  Percentage 
  Absorption 
  

  

  by 
  Al 
  (-0104 
  cm.) 
  

  

  after 
  absorption 
  

  

  in 
  column 
  I. 
  

  

  

  

  86-5 
  

  

  67-5 
  

  

  2'2 
  

  

  36-2 
  

  

  67 
  

  

  67 
  

  

  35-4 
  

  

  — 
  

  

  

  

  35-8 
  

  

  — 
  

  

  89 
  

  

  35-4 
  

  

  67 
  

  

  97 
  

  

  33-9 
  

  

  66 
  

  

  

  

  SJf'2 
  

  

  — 
  

  

  Similar 
  experiments 
  were 
  made 
  on 
  the 
  absorption 
  of 
  the 
  

   radiation 
  from 
  zinc 
  by 
  zinc 
  when 
  that 
  radiation 
  had 
  been 
  

  

  