﻿<y-Ilays 
  of 
  Uranium 
  and 
  Radium. 
  631 
  

  

  base 
  o£ 
  which 
  consisted 
  of 
  a 
  sheet 
  of 
  iron 
  sufficient 
  to 
  absorb 
  

   the 
  yS-radiation 
  completely. 
  The 
  crystals 
  just 
  filled 
  a 
  cylin- 
  

   drical 
  jar 
  of 
  about 
  the 
  diameter 
  of 
  the 
  electroscope. 
  It 
  was 
  

   found 
  that 
  the 
  7-radiation 
  in 
  the 
  two 
  substances 
  was 
  propor- 
  

   tional 
  to 
  the 
  ^-radiation, 
  indicating 
  that 
  the 
  whole 
  of 
  the 
  

   7-radiation 
  is 
  derived 
  from 
  the 
  uranium 
  X. 
  The 
  effects 
  

   measured 
  were 
  small, 
  and 
  naturally 
  no 
  great 
  accuracy 
  was 
  

   attained. 
  

  

  The 
  next 
  step 
  was 
  to 
  determine 
  the 
  rate 
  of 
  decay 
  of 
  the 
  

   7-radiation 
  of 
  uranium 
  X 
  as 
  accurately 
  as 
  possible. 
  Pre- 
  

   liminary 
  experiments 
  with 
  the 
  preparations 
  of 
  the 
  second 
  

   separation 
  had 
  shown 
  that 
  the 
  period 
  of 
  the 
  decay 
  was 
  at 
  

   any 
  rate 
  approximately 
  the 
  same 
  as 
  that 
  of 
  the 
  /S-rays. 
  

   Measurements 
  of 
  each 
  of 
  the 
  three 
  preparations 
  of 
  the 
  third 
  

   separation 
  have 
  shown 
  that 
  the 
  decay 
  of 
  the 
  7-radiation 
  is 
  

   exponential 
  from 
  the 
  date 
  of 
  separation 
  up 
  to 
  the 
  present 
  

   date 
  (30 
  days). 
  The 
  value 
  of 
  the 
  coefficient 
  of 
  decay 
  was 
  

   found 
  to 
  be 
  0*029 
  (day)~^, 
  which 
  agrees 
  as 
  closely 
  as 
  is 
  to 
  be 
  

   expected 
  with 
  the 
  value 
  found 
  for 
  the 
  /3-rays 
  0*031 
  (Rutherford 
  

   & 
  Soddy, 
  Phil. 
  Mag. 
  1903, 
  v. 
  p. 
  444). 
  

  

  Although 
  these 
  results, 
  so 
  far 
  as 
  they 
  go, 
  confirm 
  the 
  view 
  

   that 
  the 
  7-radiation 
  accompanies 
  the 
  y5-radiation 
  in 
  the 
  disinte- 
  

   gration 
  of 
  uranium 
  X, 
  there 
  seems 
  no 
  escape 
  from 
  the 
  con- 
  

   clusion 
  that 
  the 
  7-rays 
  are 
  a 
  primary 
  radiation 
  due 
  to 
  the 
  

   disintegration 
  of 
  the 
  atom, 
  and 
  not 
  a 
  secondary 
  radiation 
  

   accompanying 
  the 
  expulsion 
  of 
  the 
  /3-particle. 
  Since 
  for 
  two 
  

   elements 
  the 
  /5- 
  and 
  y-radiations 
  of 
  which, 
  although 
  similar, 
  

   each 
  to 
  each, 
  in 
  general 
  character, 
  yet 
  differ 
  in 
  relative 
  in- 
  

   tensity 
  in 
  the 
  ratio 
  of 
  50 
  to 
  1, 
  there 
  seems 
  no 
  incongruity 
  

   in 
  contemplating 
  the 
  possibility 
  of 
  a 
  y8-radiation 
  wholly 
  un- 
  

   accompanied 
  by 
  7-radiation. 
  One 
  may 
  even 
  hazard 
  the 
  

   suggestion 
  that 
  possibly 
  /5-rays 
  will 
  be 
  found 
  to 
  accompany 
  

   the 
  change 
  of 
  uranium 
  X 
  into 
  radium 
  while 
  7-rays 
  accompany 
  

   the 
  change 
  of 
  uranium 
  X 
  into 
  actinium. 
  Although 
  there 
  

   is 
  no 
  evidence 
  at 
  present 
  in 
  favour 
  of 
  this 
  there 
  is 
  equally 
  

   nothing 
  to 
  be 
  urged 
  against 
  it. 
  

  

  5 
  A. 
  

   [Later 
  results 
  for 
  the 
  decay 
  of 
  the 
  7-rays 
  over 
  a 
  period 
  of 
  

   80 
  days 
  are 
  now 
  available. 
  For 
  the 
  last 
  49 
  days 
  the 
  prepa- 
  

   rations 
  have 
  not 
  been 
  used 
  in 
  other 
  experiments, 
  or 
  disturbed 
  

   between 
  the 
  measurements. 
  The 
  value 
  of 
  \ 
  (day)"^ 
  over 
  this 
  

   period 
  has 
  been 
  found 
  to 
  be 
  0*028. 
  This 
  is 
  about 
  10 
  per 
  cent, 
  

   smaller 
  than 
  the 
  original 
  value 
  found 
  for 
  the 
  decay 
  of 
  the 
  

   y3-rays, 
  but 
  it 
  is 
  possible 
  that 
  the 
  discrepancy 
  is 
  due 
  to 
  an 
  

   error 
  in 
  the 
  determination 
  of 
  this 
  latter 
  constant. 
  We 
  are 
  

   now 
  investigating 
  this 
  point.] 
  

  

  