﻿22G 
  Prof. 
  A. 
  S. 
  Eve 
  on 
  the 
  Secondary 
  7 
  Bays 
  

  

  secondary 
  radiations 
  from 
  the 
  same 
  plates 
  were 
  also 
  mea- 
  

   sured, 
  due 
  to 
  14 
  mgs. 
  of 
  pure 
  radium 
  bromide 
  placed 
  inside 
  

   a 
  hollow 
  steel 
  * 
  cylinder, 
  2*2 
  cms. 
  thick, 
  having 
  stopped 
  ends. 
  

   The 
  cathode 
  secondary 
  rays 
  were 
  in 
  this 
  case 
  screened 
  from 
  

   the 
  electroscope 
  by 
  aluminium 
  1*63 
  mms. 
  thick, 
  placed 
  just 
  

   in 
  front 
  of 
  the 
  very 
  thin 
  face 
  of 
  the 
  electroscope. 
  The 
  

   results 
  given 
  show 
  that 
  when 
  the 
  cathode 
  rays 
  are 
  in 
  each 
  

   case 
  removed, 
  the 
  orders 
  are 
  not 
  those 
  of 
  atomic 
  weights. 
  

   Very 
  thick 
  radiators 
  are 
  needed 
  to 
  get 
  the 
  full 
  value 
  of 
  the 
  

   y 
  rays 
  from 
  the 
  lighter 
  substances. 
  

  

  Lead 
  is 
  a 
  poor 
  secondary 
  radiator 
  in 
  both 
  cases, 
  but 
  iron 
  

   radiates 
  well 
  with 
  the 
  7 
  rays 
  and 
  badly 
  with 
  the 
  X 
  rays. 
  It 
  

   is 
  unnecessary 
  to 
  examine 
  these 
  results 
  more 
  closely, 
  because 
  

   the 
  secondary 
  X 
  rays 
  have 
  been 
  carefully 
  investigated 
  by 
  

   Barkla 
  and 
  others, 
  while 
  the 
  secondary 
  7 
  rays 
  will 
  be 
  discussed 
  

   in 
  this 
  paper. 
  

  

  As 
  regards 
  the 
  secondary 
  cathode 
  rays 
  from 
  X 
  rays, 
  

   ft 
  rays, 
  and 
  7 
  rays, 
  it 
  has 
  been 
  shown 
  by 
  J. 
  J. 
  Thomson, 
  

   McClelland, 
  and 
  Kleeman, 
  respectively, 
  that 
  the 
  radiation 
  

   intensities 
  follow 
  the 
  order 
  of 
  the 
  atomic 
  weights. 
  

  

  It 
  will 
  be 
  seen 
  later 
  that 
  the 
  secondary 
  7 
  rays 
  from 
  a 
  thick 
  

   block 
  of 
  iron 
  may 
  amount 
  to 
  25 
  or 
  30 
  per 
  cent, 
  of 
  the 
  total 
  

   secondary 
  cathode 
  and 
  7 
  rays 
  from 
  the 
  same 
  block. 
  Moreover, 
  

   the 
  velocity 
  of 
  the 
  secondary 
  cathode 
  rays 
  due 
  to 
  7 
  rays 
  is 
  

   nearly 
  equal 
  to 
  that 
  of 
  the 
  secondary 
  cathode 
  rays 
  due 
  to 
  

   ft 
  rays. 
  The 
  values 
  of 
  the 
  so-called 
  coefficients 
  of 
  absorption 
  

   by 
  a 
  screen 
  of 
  aluminium 
  OI 
  mm. 
  thick, 
  placed 
  before 
  the 
  

   electroscope, 
  I 
  find 
  to 
  be 
  as 
  follows 
  : 
  — 
  

  

  Primary 
  ft 
  21*5 
  

  

  Cathode 
  secondary 
  from 
  lead, 
  due 
  to 
  /Sand 
  7 
  rays, 
  24*5 
  

  

  Cathode 
  „ 
  „ 
  „ 
  7 
  rays 
  only, 
  31*0 
  

  

  Hence, 
  the 
  velocities 
  of 
  the 
  cathode 
  secondary 
  rays 
  are 
  a 
  

   little 
  less 
  for 
  7 
  than 
  for 
  ft 
  rays, 
  and 
  both 
  these 
  groups 
  have 
  

   less 
  velocity 
  than 
  that 
  of 
  the 
  ft 
  primary 
  ray-. 
  

  

  On 
  the 
  other 
  hand, 
  the 
  coefficient 
  of 
  absorption 
  by 
  lead 
  of 
  

   the 
  secondary 
  7 
  rays 
  due 
  to 
  7 
  primary, 
  reflected 
  from 
  lead 
  or 
  

   iron, 
  is 
  about 
  4, 
  nearly 
  equal 
  lo 
  the 
  coefficient 
  of 
  absorption 
  

   found 
  by 
  Godlewski 
  for 
  the 
  primary 
  7 
  rays 
  of 
  actinium. 
  

   greater 
  than 
  the 
  coefficient 
  o£ 
  absorption 
  of 
  the 
  7 
  rays 
  from 
  

   uranium, 
  and 
  yet 
  greater 
  than 
  thai 
  of 
  radium 
  (Phil. 
  Mag. 
  

   April 
  L906). 
  It 
  may. 
  therefore, 
  be 
  concluded 
  that 
  7 
  rays 
  

   give 
  rise 
  to 
  secondary 
  rays 
  of 
  the 
  7 
  type, 
  and 
  not 
  merely 
  to 
  

   very 
  penetrating 
  cathode 
  rays. 
  This 
  will 
  he 
  seen 
  more 
  

   clearly 
  from 
  the 
  diagrams 
  given 
  later. 
  

  

  • 
  \iirr 
  completing 
  the 
  work 
  I 
  learn 
  that 
  this 
  was 
  made 
  of 
  nickel- 
  

   steel 
  , 
  5 
  per 
  cent, 
  nickel. 
  

  

  