﻿330 
  Prof. 
  Rutherford 
  and 
  Mr. 
  Hichardson 
  : 
  Analysis 
  

  

  for 
  carbon 
  were 
  found 
  to 
  be 
  identical 
  in 
  character 
  with 
  those 
  

   obtained 
  for 
  aluminium, 
  and 
  the 
  proportion 
  of 
  hard 
  to 
  soft 
  

   radiation 
  was 
  the 
  same 
  in 
  both 
  cases. 
  This 
  agreement 
  indi- 
  

   cates 
  that 
  the 
  measurement 
  of 
  the 
  absorption 
  is 
  not 
  com- 
  

   plicated 
  to 
  an 
  appreciable 
  extent 
  by 
  the 
  excitation 
  of 
  7 
  rays 
  

   in 
  the 
  absorbing 
  screens 
  by 
  the 
  primary 
  7 
  rays 
  from 
  radium 
  I). 
  

   Very 
  active 
  preparations 
  of 
  radium 
  E 
  were 
  obtained, 
  and 
  

   before 
  the 
  application 
  of 
  the 
  magnetic 
  field 
  the 
  /3-ray 
  activity 
  

   was 
  found 
  to 
  be 
  about 
  2000 
  divisions 
  per 
  minute. 
  On 
  

   applying 
  the 
  magnetic 
  field 
  the 
  amount 
  of 
  7 
  radiation 
  

   observed 
  never 
  gave 
  more 
  than 
  half 
  a 
  division 
  per 
  minute. 
  

   The 
  absorption 
  curve 
  of 
  this 
  radiation 
  was 
  examined 
  in 
  

   aluminium, 
  but 
  could 
  not 
  be 
  determined 
  with 
  much 
  accuracy 
  

   on 
  account 
  of 
  the 
  smallness 
  of 
  the 
  effects. 
  The 
  absorption 
  

   curve 
  obtained 
  is 
  shown 
  in 
  fig. 
  4. 
  It 
  will 
  be 
  seen 
  that 
  the 
  

   curve 
  is 
  very 
  similar 
  in 
  shape 
  to 
  that 
  obtained 
  for 
  radium 
  D. 
  

  

  

  

  

  

  Fig. 
  

  

  4. 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  \ 
  

  

  

  

  

  

  

  

  

  

  \ 
  

  

  

  

  

  

  

  

  

  3 
  

  

  540 
  

  

  \ 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  1-00 
  1-25 
  

  

  V 
  MMS 
  OF 
  ZlLUMIN/U*, 
  

   FFtOM 
  ft/)D/UM 
  £. 
  

  

  The 
  results, 
  however, 
  are 
  not 
  of 
  sufficient 
  accuracy 
  to 
  

   analyse 
  the 
  constituents 
  of 
  the 
  radiation 
  with 
  any 
  certainty. 
  

   It 
  was 
  of 
  great 
  importance 
  to 
  settle 
  whether 
  the 
  small 
  

   7 
  radiation 
  observed 
  is 
  to 
  be 
  ascribed 
  to 
  radium 
  E 
  or 
  to 
  the 
  

   presence 
  of 
  a 
  small 
  amount 
  of 
  radium 
  D 
  as 
  impurity. 
  For 
  

   this 
  purpose, 
  the 
  7-ray 
  activity 
  of 
  the 
  radium 
  E 
  preparation 
  

   was 
  examined 
  over 
  several 
  weeks. 
  It 
  was 
  found 
  that 
  the 
  

   amount 
  of 
  7 
  radiation 
  decreased 
  at 
  the 
  same 
  rate 
  as 
  the 
  /3-ray 
  

   activity, 
  and 
  ultimately 
  became 
  too 
  small 
  to 
  measure. 
  This 
  

   result 
  showed 
  conclusively 
  that 
  the 
  7 
  radiation 
  must 
  arise 
  

   from 
  radium: 
  E 
  and 
  not 
  from 
  radium 
  D. 
  It 
  would 
  appear 
  

  

  