﻿due 
  to 
  the 
  7 
  Rays 
  of 
  Radium 
  C. 
  'I'll 
  

  

  The 
  fact 
  that 
  the 
  cathode 
  secondary 
  rays 
  due 
  to 
  ft 
  or 
  to 
  

   7 
  rays 
  have 
  velocities 
  comparable 
  with 
  that 
  of: 
  the 
  primary 
  

   ft 
  rays 
  is 
  a 
  very 
  important 
  one. 
  The 
  secondary 
  cathode 
  ray- 
  

   due 
  to 
  X 
  rays 
  have 
  much 
  less 
  velocity. 
  Bragg 
  has 
  pointed 
  

   out 
  that 
  it 
  is 
  probably 
  more 
  than 
  a 
  coincidence 
  that 
  the 
  

   secondary 
  cathode 
  rays 
  due 
  to 
  X 
  rays 
  have 
  velocities 
  of 
  the 
  

   same 
  order 
  as 
  those 
  of 
  the 
  cathode 
  rays 
  in 
  the 
  X-ray 
  tube, 
  

   whilst 
  the 
  secondary 
  cathode 
  rays 
  due 
  to 
  7 
  rays 
  approximate 
  

   in 
  velocity 
  to 
  that 
  of 
  the 
  primary 
  ft 
  rays. 
  These 
  relations, 
  it: 
  

   more 
  than 
  accidental, 
  do 
  not 
  necessarily 
  furnish 
  an 
  argument 
  

   in 
  favour 
  of 
  the 
  view 
  recently 
  advocated 
  with 
  so 
  much 
  skill 
  

   by 
  Professor 
  Bragg 
  as 
  to 
  the 
  material 
  character 
  of 
  X 
  and 
  

   7 
  rays. 
  For 
  it 
  may 
  be 
  that 
  aether 
  pulses 
  striking 
  a 
  solid 
  body 
  

   cause 
  the 
  ejection 
  of 
  some 
  of 
  those 
  corpuscles 
  only 
  which 
  

   have 
  velocities 
  in 
  their 
  orbit 
  or 
  free 
  path 
  approximating 
  to 
  

   those 
  of 
  the 
  corpuscles 
  which 
  first 
  gave 
  rise 
  to 
  the 
  aether 
  

   pulses. 
  

  

  One 
  fundamental 
  difficulty 
  arises 
  in 
  writing 
  on 
  secondary 
  

   radiation. 
  The 
  investigations 
  of 
  H. 
  "W. 
  Schmidt*, 
  and 
  of 
  

   Crowther 
  f, 
  indicate 
  that 
  secondary 
  cathode 
  radiation 
  consists 
  

   mainly, 
  or 
  entirely, 
  of 
  scattered 
  primary 
  rays 
  ; 
  for 
  he 
  has 
  

   proved 
  that 
  ft 
  particles, 
  in 
  passing 
  through 
  matter, 
  lose 
  little 
  

   or 
  no 
  velocity 
  and 
  are 
  diffusely 
  scattered. 
  On 
  the 
  other 
  

   hand 
  Kleeman, 
  in 
  treating 
  of 
  secondary 
  rays 
  due 
  to 
  

   primary 
  7 
  rays, 
  writes 
  of 
  " 
  electrons 
  ejected 
  by 
  7 
  rays." 
  

   Now 
  the 
  electrons 
  which 
  constitute 
  the 
  secondary 
  cathode 
  

   radiation, 
  due 
  to 
  ft 
  and 
  to 
  7 
  rays 
  respectively, 
  have 
  nearly 
  

   equal 
  velocities 
  ; 
  and 
  it 
  seems 
  unreasonable 
  to 
  suppose 
  that 
  in 
  

   the 
  one 
  case 
  we 
  have 
  scattered 
  primary 
  rays, 
  and 
  in 
  the 
  other 
  

   case 
  electrons 
  ejected 
  from 
  the 
  atoms 
  of 
  the 
  secondary 
  radiator. 
  

   It 
  must 
  be 
  admitted 
  that 
  Bragg's 
  theory 
  of 
  the 
  close 
  similarity 
  

   of 
  ft 
  and 
  7 
  rays 
  — 
  the 
  difference 
  being 
  merely 
  the 
  important 
  

   one 
  of 
  charge 
  — 
  removes 
  all 
  these 
  difficulties 
  as 
  far 
  as 
  

   secondary 
  radiation 
  is 
  concerned. 
  Nor 
  does 
  his 
  theory 
  seem 
  

   more 
  complicated 
  than 
  the 
  conception 
  of 
  an 
  aether 
  pulse 
  with 
  

   discrete 
  centres 
  of 
  energy 
  on 
  the 
  surface 
  of 
  the 
  spherical 
  

   shell 
  of 
  the 
  aether 
  pulse. 
  But 
  apparently 
  other 
  difficulties 
  

   arise. 
  Again, 
  H. 
  Starke 
  in 
  Le 
  Radium 
  for 
  February 
  1908, 
  

   finds 
  that 
  ft 
  rays 
  striking 
  a 
  solid 
  do 
  not 
  give 
  rise 
  to 
  secondary 
  

   7 
  rays 
  ; 
  and 
  my 
  observations 
  tend 
  in 
  that 
  direction 
  also, 
  for 
  

   the 
  secondary 
  7 
  rays 
  appear 
  to 
  be 
  caused 
  solely 
  by 
  the 
  

   primary 
  7 
  rays. 
  Nevertheless, 
  it 
  is 
  remarkable 
  that 
  the 
  

   impact 
  of 
  cathode 
  rays 
  should 
  give 
  rise 
  to 
  X 
  rays, 
  and 
  that 
  

   the 
  impact 
  of 
  ft 
  rays 
  should 
  not 
  give 
  rise 
  to 
  7 
  rays. 
  However, 
  

   we 
  have 
  no 
  knowledge 
  of 
  the 
  effect 
  of 
  concentration 
  of 
  the 
  

  

  * 
  Phys. 
  Zeit. 
  June] 
  907. 
  

   f 
  Le 
  Radium. 
  March 
  1908. 
  

  

  