﻿Investigation 
  of 
  the 
  Nature 
  of 
  7 
  Rays. 
  935 
  

  

  explain 
  the 
  observed 
  effect. 
  Nor 
  do 
  our 
  difficulties 
  end 
  here. 
  

   For 
  if 
  the 
  expulsion 
  of 
  the 
  electron 
  is 
  the 
  result 
  of 
  an 
  atomic 
  

   disintegration, 
  should 
  we 
  not 
  expect 
  the 
  velocity 
  of 
  the 
  

   electron 
  to 
  vary 
  from 
  atom 
  to 
  atom, 
  as 
  it 
  does 
  in 
  the 
  case 
  of 
  

   the 
  radioactive 
  substances 
  ? 
  It 
  is 
  inconceivable 
  that 
  the 
  

   explosion 
  of 
  a 
  light 
  atom 
  should 
  result 
  in 
  the 
  expulsion 
  of 
  

   an 
  electron 
  with 
  exactly 
  the 
  same 
  speed 
  as 
  in 
  the 
  case 
  of 
  the 
  

   heavy 
  atom. 
  And, 
  further, 
  assuming 
  the 
  same 
  hypothesis, 
  

   how 
  can 
  the 
  production 
  of 
  /3 
  rays, 
  in 
  the 
  case 
  of 
  the 
  hard 
  

   7 
  rays, 
  be 
  absolutely 
  independent 
  of 
  atomic 
  structure 
  in 
  all 
  

   respects 
  whatever 
  ? 
  

  

  Thus, 
  after 
  its 
  first 
  small 
  success, 
  the 
  theory 
  breaks 
  down 
  

   at 
  every 
  point. 
  It 
  is 
  true 
  that 
  Wien 
  makes 
  a 
  tentative 
  appli- 
  

   cation 
  of 
  a 
  theory 
  of 
  Planck, 
  viz., 
  that 
  energy 
  emitted 
  from 
  

   atoms 
  is 
  divided 
  into 
  definite 
  units, 
  the 
  size 
  of 
  which 
  is 
  in- 
  

   versely 
  proportional 
  to 
  the 
  associate 
  wave-length. 
  He 
  thence 
  

   deduces 
  the 
  law 
  v 
  2 
  X 
  = 
  constant, 
  where 
  v 
  is 
  the 
  velocity 
  of 
  the 
  

   ejected 
  electron, 
  and 
  \ 
  the 
  thickness 
  of 
  the 
  X-ray 
  pulse 
  

   which 
  he 
  is 
  considering. 
  He 
  thus 
  passes 
  by 
  the 
  need 
  of 
  

   explaining 
  certain 
  of 
  the 
  difficulties 
  just 
  discussed, 
  and 
  

   arrives 
  at 
  a 
  formula 
  from 
  which 
  the 
  second 
  and 
  third 
  

   properties 
  in 
  the 
  above 
  summary 
  may 
  be 
  derived. 
  Even 
  

   then 
  his 
  theory 
  fails 
  to 
  explain 
  the 
  first 
  and 
  fourth 
  properties. 
  

   It 
  seems 
  to 
  us 
  to 
  be 
  clear 
  that 
  the 
  application 
  of 
  Planck's 
  

   theory 
  is 
  not 
  justified. 
  And, 
  generally, 
  we 
  conclude 
  that 
  

   the 
  energy 
  of 
  the 
  secondary 
  /3 
  ray 
  does 
  not 
  come 
  from 
  the 
  

   atom. 
  

  

  We 
  now 
  come 
  to 
  the 
  second 
  case. 
  In 
  this 
  there 
  is 
  no 
  

   suggestion 
  of 
  trigger 
  action 
  ; 
  the 
  energy 
  of 
  the 
  ft 
  radiation 
  

   is 
  supposed 
  to 
  be 
  entirely 
  derived 
  from 
  that 
  of 
  the 
  aether 
  

   pulses. 
  As 
  already 
  mentioned, 
  this 
  theory 
  has 
  lately 
  been 
  

   maintained 
  by 
  J. 
  J. 
  Thomson 
  (Proc. 
  Camb. 
  Phil. 
  Soc. 
  vol. 
  xiv. 
  

   pt. 
  iv. 
  p. 
  417). 
  It 
  is 
  also 
  discussed 
  by 
  N. 
  R. 
  Campbell 
  

   (' 
  Modern 
  Electrical 
  Theory 
  '). 
  Since 
  an 
  aether 
  pulse 
  of 
  the 
  

   orthodox 
  form 
  spreads 
  its 
  energy 
  over 
  wider 
  and 
  wider 
  

   surfaces 
  as 
  it 
  radiates 
  from 
  its 
  origin, 
  and 
  since 
  the 
  energy 
  

   of 
  the 
  ejected 
  secondary 
  particle 
  is 
  immensely 
  greater 
  than 
  

   can 
  be 
  imparted 
  to 
  it 
  during 
  the 
  passage 
  of 
  the 
  weak, 
  and 
  

   always 
  weakening, 
  pulse, 
  it 
  becomes 
  a 
  necessity 
  on 
  this 
  hypo- 
  

   thesis 
  to 
  concentrate 
  the 
  energy 
  of 
  the 
  pulse 
  along 
  radial 
  

   lines, 
  having 
  their 
  centre 
  at 
  the 
  place 
  where 
  the 
  primary 
  

   cathode 
  particle 
  is 
  suddenly 
  stopped 
  or 
  accelerated. 
  Thomson 
  

   speaks 
  of 
  " 
  bundles 
  of 
  energy 
  " 
  occupying 
  only 
  a 
  very 
  small 
  

   portion 
  of 
  the 
  wave-front, 
  the 
  rest 
  of 
  the 
  front 
  being 
  blank. 
  

   Of 
  course 
  this 
  at 
  once 
  suggests 
  explanations 
  of 
  some 
  of 
  the 
  

   difficulties 
  of 
  the 
  7 
  and 
  X-rays, 
  such 
  as 
  the 
  ionization 
  of 
  only 
  

  

  