﻿938 
  Experimental 
  Investigation 
  of 
  the 
  Nature 
  of 
  y 
  Rays. 
  

  

  (3 
  rays. 
  When 
  the 
  y 
  rays 
  break 
  up, 
  the 
  negatives 
  so 
  pro- 
  

   duced 
  have 
  the 
  same 
  speed 
  as 
  the 
  primary 
  /3 
  rays. 
  

  

  The 
  fifth 
  would 
  show 
  that 
  there 
  are 
  stronger 
  fields 
  inside 
  

   heavy 
  atoms 
  than 
  light 
  ones, 
  and 
  that 
  the 
  chance 
  of 
  sepa- 
  

   ration 
  of 
  a 
  pair 
  increases 
  with 
  (a) 
  the 
  strength 
  of 
  the 
  field, 
  

   (/<) 
  the 
  time 
  taken 
  to 
  cross 
  it. 
  

  

  This 
  is 
  all 
  the 
  explanation 
  that 
  is 
  necessary. 
  We 
  can 
  at 
  

   least 
  claim 
  that 
  it 
  is 
  much 
  simpler 
  and 
  more 
  complete 
  than 
  

   any 
  explanation 
  which 
  the 
  rcther-pulse 
  theory 
  seems 
  likely 
  to 
  

   afford, 
  even 
  in 
  its 
  latest 
  form. 
  

  

  It 
  is 
  true 
  that 
  the 
  neutral-pair 
  hypothesis 
  requires 
  the 
  

   existence 
  of! 
  a 
  positive 
  counterpart 
  to 
  the 
  negative 
  electron. 
  

   In 
  a 
  previous 
  paper 
  it 
  was 
  suggested 
  that 
  this 
  might 
  be 
  an 
  

   a 
  particle 
  : 
  the 
  results 
  of 
  this 
  paper 
  seem 
  rather 
  to 
  suggest 
  

   that 
  its 
  mass 
  is 
  only 
  -mall, 
  and 
  that 
  it 
  may 
  really 
  he 
  a 
  

   pn-irivi- 
  electron. 
  Now 
  the 
  positive 
  electron 
  has 
  hitherto, 
  

   been 
  received 
  with 
  little 
  favour 
  : 
  hut 
  the 
  argument 
  has 
  been 
  

   not 
  so 
  much 
  against 
  it- 
  existence 
  as 
  against 
  its 
  presence 
  in 
  

   metals 
  in 
  a 
  tree 
  state. 
  The 
  latter 
  is 
  not 
  at 
  all 
  necessary 
  to 
  

   our 
  hypothesis. 
  We 
  require 
  only 
  that 
  the 
  positive 
  shall 
  exist,. 
  

   that 
  it 
  can 
  he 
  torn 
  from 
  its 
  attachment 
  and 
  carried 
  away 
  by 
  

   a 
  passing 
  negative 
  electron, 
  and. 
  again, 
  that 
  it 
  can 
  be 
  left 
  

   behind 
  in 
  some 
  atom 
  which 
  the 
  pair 
  subsequently 
  traverses. 
  

  

  The 
  receni 
  determination 
  by 
  Cooksey 
  of 
  the 
  want 
  of 
  

   symmetry 
  between 
  the 
  emergence 
  and 
  incidence 
  radiations 
  

   tine 
  to 
  X-rays 
  is 
  the 
  last 
  experiment 
  required 
  to 
  show 
  that 
  

   all 
  the 
  properties 
  in 
  the 
  summary 
  of 
  § 
  II. 
  are 
  true 
  for 
  X-rays. 
  

   a- 
  well 
  as 
  for 
  7 
  rays, 
  mutatis 
  mutandis. 
  All 
  the 
  properties 
  

   except 
  the 
  first 
  have 
  been 
  already 
  shown 
  to 
  be 
  true 
  (see 
  our 
  

   first 
  paper 
  on 
  this 
  subject). 
  The 
  complete 
  parallelism 
  between 
  

   X- 
  and 
  7 
  rays 
  stands 
  out 
  more 
  strongly 
  than 
  ever. 
  

  

  In 
  conclusion, 
  there 
  is 
  one 
  aspect 
  of 
  the 
  problem 
  which 
  

   seems 
  to 
  invite 
  a 
  little 
  further 
  consideration. 
  The 
  charac- 
  

   teristics 
  of 
  the 
  secondary 
  /9 
  ray 
  are 
  independent, 
  as 
  we 
  have 
  

   seen, 
  of 
  the 
  nature 
  of 
  the 
  atom 
  in 
  which 
  it 
  arises, 
  and 
  depend 
  

   only 
  on 
  the 
  nature 
  of 
  the 
  y 
  ray 
  to 
  which 
  it 
  is 
  due. 
  This 
  is 
  

   all 
  the 
  more 
  remarkable 
  when 
  we 
  consider 
  that 
  the 
  charac- 
  

   teristics 
  of 
  primary 
  /3 
  rays 
  are 
  peculiarly 
  dependent 
  on 
  the 
  

   nature 
  of 
  the 
  atoms 
  whence 
  they 
  emerge, 
  and 
  are 
  absolutely 
  

   independent 
  of 
  physical 
  agencies 
  acting 
  from 
  without. 
  In 
  

   the 
  one 
  case, 
  that 
  of 
  secondary 
  ft 
  radiation, 
  we 
  can 
  determine 
  

   that 
  a 
  given 
  material 
  shall 
  emit 
  & 
  rays 
  of 
  definite 
  speed 
  and 
  

   direction, 
  and 
  can 
  carry 
  out 
  our 
  determination 
  by 
  the 
  use 
  of 
  

   suitable 
  agencies 
  and 
  dispositions. 
  In 
  the 
  other 
  case, 
  that 
  of 
  

   primary 
  ft 
  radiation, 
  the 
  whole 
  process 
  is 
  completely 
  beyond 
  

   our 
  control. 
  It 
  is 
  one 
  example 
  of 
  this 
  contrast 
  that 
  the 
  

  

  