﻿934 
  Prof. 
  Bragg 
  and 
  Mr. 
  Madsen 
  : 
  An 
  Experimental 
  

  

  is 
  put 
  forward 
  by 
  W. 
  Wien 
  (Gottingen 
  Nachrichten, 
  1907, 
  

   p. 
  598). 
  

  

  Secondly, 
  it 
  may 
  be 
  supposed 
  that 
  the 
  energy 
  of 
  the 
  /3 
  

   radiation 
  comes 
  from 
  the 
  7 
  ray, 
  but 
  the 
  material 
  from 
  the 
  

   atom. 
  The 
  7 
  ray 
  is 
  a 
  bundle 
  of 
  electric 
  energy, 
  possessing 
  

   mass, 
  which 
  impinges 
  on 
  the 
  atom 
  and 
  drives 
  out 
  the 
  electron 
  

   before 
  it. 
  This 
  is 
  the 
  view 
  now 
  held 
  by 
  J. 
  J. 
  Thomson 
  

   (Camb. 
  Phil. 
  Soc. 
  Proc. 
  vol. 
  xiv. 
  pt. 
  iv. 
  p. 
  417). 
  

  

  Thirdly, 
  both 
  the 
  energy 
  and 
  the 
  material 
  of 
  tin 
  1 
  /3 
  ray 
  

   may 
  be 
  supposed 
  to 
  be 
  derived 
  from 
  the 
  7 
  ray. 
  The 
  latter 
  is 
  

   not 
  a 
  pulse 
  but 
  a 
  neutral 
  pair, 
  positive 
  and 
  negative 
  ; 
  in 
  

   passing 
  through 
  sonic 
  atom 
  the 
  bunds 
  are 
  dissolved, 
  and 
  the 
  

   negative 
  flies 
  on 
  (Trans. 
  Roy. 
  Soc. 
  of 
  S.A., 
  May 
  P907 
  ; 
  Phil. 
  

   Blag. 
  Oct. 
  L907). 
  

  

  Consider 
  firsi 
  the 
  theory 
  which 
  considers 
  that 
  the 
  whole 
  of 
  

   the 
  energy 
  of 
  the 
  expelled 
  electron 
  conies 
  from 
  the 
  internal 
  

   energy 
  of 
  the 
  atom. 
  It 
  is 
  to 
  be 
  supposed 
  that 
  the 
  pulse 
  as 
  it 
  

   widens 
  finds 
  an 
  atom 
  here 
  and 
  there 
  which 
  is 
  in 
  an 
  explosive 
  

   condition, 
  and 
  thai 
  in 
  -ume 
  unknown 
  way 
  it 
  precipitates 
  a 
  

   catastrophe. 
  Then- 
  i>. 
  of 
  course, 
  one 
  point 
  which 
  is 
  imme- 
  

   diately 
  cleared 
  np 
  by 
  Mich 
  an 
  hypothesis, 
  viz., 
  that 
  the 
  speed 
  

   of 
  the 
  expelled 
  electron 
  is 
  independent 
  of 
  the 
  intensity 
  or 
  

   quantity 
  of 
  the 
  primary 
  radiation. 
  But 
  here 
  we 
  stop 
  short, 
  

   for 
  we 
  have 
  also 
  to 
  explain 
  why 
  the 
  speed 
  of 
  the 
  electron 
  is 
  

   not 
  independent 
  of 
  the 
  quality 
  of 
  the 
  primary 
  radiation. 
  

   Why 
  should 
  the 
  speed 
  be 
  great 
  when 
  the 
  primary 
  7 
  rays 
  

   are 
  hard, 
  and 
  small 
  when 
  they 
  are 
  soft 
  ? 
  Why 
  should 
  the 
  

   velocity 
  of 
  the 
  >hot 
  depend 
  on 
  the 
  way 
  in 
  which 
  the 
  trigger 
  

   is 
  pulled 
  ? 
  We 
  might 
  get 
  out 
  of 
  the 
  difficulty 
  by 
  supposing 
  

   an 
  atom 
  to 
  be 
  like 
  a 
  battery 
  which 
  contained 
  a 
  number 
  of 
  

   different 
  kinds 
  of 
  guns, 
  and 
  that 
  the 
  pulses 
  were 
  selective, 
  

   each 
  pulling 
  the 
  trigger 
  of 
  its 
  own 
  particular 
  gun. 
  But 
  

   even 
  if 
  we 
  have 
  presumed 
  some 
  highly 
  artificial 
  arrangement 
  

   of 
  this 
  kind, 
  we 
  have 
  greater 
  difficulties 
  still 
  to 
  face. 
  How 
  

   is 
  it 
  that 
  the 
  pulses 
  always 
  find 
  the 
  guns 
  pointing 
  in 
  the 
  

   direction 
  in 
  which 
  they 
  are 
  travelling 
  themselves, 
  so 
  that 
  the 
  

   motion 
  of 
  the 
  shot 
  is 
  a 
  continuation 
  of 
  their 
  own 
  line 
  of 
  

   flight 
  ? 
  For 
  if 
  the 
  speed 
  of 
  the 
  electron 
  is 
  independent 
  of 
  

   the 
  strength 
  of 
  the 
  pulse, 
  then, 
  so 
  to 
  speak, 
  the 
  touch 
  on 
  the 
  

   trigger 
  must 
  be 
  very 
  light 
  indeed, 
  and 
  can 
  have 
  nothing 
  to 
  

   do 
  with 
  the 
  laying 
  of 
  the 
  gun. 
  We 
  might 
  perhaps 
  suppose 
  

   that 
  there 
  were 
  guns 
  in 
  the 
  battery 
  pointing 
  in 
  all 
  directions, 
  

   and 
  that 
  the 
  pulse 
  only 
  fired 
  the 
  one 
  which 
  pointed 
  in 
  that 
  

   direction 
  in 
  which 
  it 
  was 
  travelling 
  itself 
  ; 
  but 
  this 
  would 
  

   require 
  a 
  special 
  atomic 
  structure 
  to 
  meet 
  the 
  case, 
  and 
  it 
  

   would 
  be 
  out 
  of 
  all 
  proportion 
  to 
  frame 
  such 
  an 
  hypothesis 
  to 
  

  

  