﻿740 
  Mr. 
  F. 
  Soddy 
  on 
  

  

  already 
  survived 
  many 
  times 
  the 
  average 
  period 
  are 
  con- 
  

   sidered. 
  What 
  may 
  be 
  termed 
  the 
  inevitableness 
  of 
  the 
  

   process, 
  and 
  its 
  entire 
  independence 
  of 
  all 
  known 
  conditions, 
  

   suggests 
  that 
  the 
  cause 
  of 
  disintegration 
  is 
  apart 
  from 
  the 
  

   atom. 
  It 
  is 
  difficult 
  to 
  believe 
  that 
  the 
  cause 
  is 
  resident 
  in 
  

   space 
  external 
  to 
  the 
  atom. 
  It 
  seems 
  more 
  probable 
  that 
  it 
  

   exists 
  within 
  the 
  atom 
  and 
  at 
  the 
  same 
  time 
  is 
  uninfluenced 
  

   by 
  it. 
  The 
  question 
  about 
  to 
  be 
  discussed 
  is 
  whether 
  

   necessarily 
  only 
  one 
  mode 
  of 
  instability 
  can 
  exist 
  within 
  the 
  

   atom 
  at 
  the 
  same 
  time. 
  

  

  In 
  certain 
  problems 
  in 
  radioactivity 
  it 
  is 
  becoming 
  

   necessary 
  to 
  lake 
  into 
  account 
  that 
  the 
  same 
  element, 
  for 
  

   example 
  uranium, 
  may 
  give 
  rise 
  to 
  two 
  different 
  series 
  of 
  

   disintegration 
  products, 
  represented 
  for 
  example 
  by 
  actinium 
  

   and 
  radium. 
  Rutherford 
  has 
  suggested 
  in 
  order 
  to 
  account 
  

   for 
  the 
  small 
  quantity 
  of 
  actinium, 
  relatively 
  to 
  radium_, 
  

   in 
  minerals 
  that 
  actinium 
  may 
  be 
  formed 
  from 
  uranium 
  as 
  a 
  

   side 
  or 
  branch 
  chain, 
  not 
  in 
  the 
  main 
  line 
  of 
  descent. 
  The 
  

   suggestion 
  in 
  this 
  paper 
  is 
  that 
  multiple 
  modes 
  of 
  disinte- 
  

   gration 
  may 
  be 
  proceeding 
  simultaneously 
  and 
  independently 
  

   within 
  the 
  same 
  atom. 
  There 
  is 
  nothing 
  in 
  this 
  idea 
  opposed 
  

   to 
  all 
  that 
  is 
  known 
  of 
  the 
  character 
  of 
  atomic 
  disintegration. 
  

   On 
  the 
  other 
  hand 
  it 
  will 
  be 
  shown 
  that 
  such 
  disinte- 
  

   grations 
  would 
  simulate 
  closely 
  in 
  many 
  respects 
  simple 
  

   disintegration. 
  

  

  It 
  has 
  been 
  established 
  that 
  the 
  law 
  of 
  simple 
  disintegration 
  

   really 
  expresses 
  the 
  operation 
  of 
  the 
  law 
  of 
  probability 
  for 
  

   a 
  process 
  selecting 
  the 
  particular 
  individual 
  atoms 
  dis- 
  

   integrating 
  without 
  reference 
  to 
  the 
  character 
  of 
  the 
  

   individuals, 
  but 
  solely 
  according 
  to 
  the 
  total 
  number 
  in 
  

   existence. 
  That 
  is 
  to 
  say, 
  the 
  period 
  of 
  actual 
  life 
  of 
  the 
  

   individual 
  remains 
  indefinite 
  up 
  to 
  the 
  moment 
  of 
  disinte- 
  

   gration, 
  and 
  no 
  process 
  of 
  sorting 
  a 
  collection 
  of 
  atoms 
  

   into 
  long-lived 
  and 
  short-lived 
  varieties 
  is 
  even 
  conceivable. 
  

   Similarly 
  for 
  multiple 
  disintegration 
  the 
  view 
  advocated 
  is 
  

   that 
  the 
  law 
  of 
  simple 
  disintegation 
  applies 
  to 
  each 
  mode 
  of 
  

   disintegration 
  exactly 
  as 
  if 
  it 
  were 
  the 
  only 
  one 
  in 
  operation. 
  

   It 
  follows 
  that 
  the 
  question 
  by 
  which 
  particular 
  mode 
  any 
  

   individual 
  atom 
  will 
  disintegrate 
  remains 
  indefinite 
  up 
  to 
  the 
  

   moment 
  of 
  disintegration 
  and 
  no 
  process 
  is 
  conceivable 
  which 
  

   would 
  sort 
  a 
  collection 
  of 
  atoms 
  according 
  to 
  the 
  mode 
  by 
  

   which 
  eventually 
  they 
  will 
  disintegrate 
  and 
  to 
  the 
  product 
  

   which 
  eventually 
  they 
  will 
  produce. 
  

  

  If 
  for 
  the 
  same 
  atom 
  two 
  modes 
  of 
  disintegration 
  can 
  

   occur 
  independently, 
  the 
  constant 
  of 
  the 
  first 
  mode 
  being 
  

   represented 
  by 
  Xa 
  and 
  that 
  of 
  the 
  second 
  by 
  Xx? 
  the 
  quantity 
  

  

  