﻿THE 
  

   LONDON, 
  EDINBURGH 
  and 
  DUBLIN 
  

  

  PHILOSOPHICAL 
  MAGAZINE 
  

  

  AND 
  

  

  JOURNAL 
  OF 
  SCIENCE. 
  

  

  [SIXTH 
  SERIES.] 
  

  

  DECEMBER 
  1913. 
  

  

  LXXXII. 
  Analysis 
  of 
  the 
  7 
  Rays 
  of 
  the 
  Thorium 
  and 
  

   Actinium 
  Products. 
  By 
  Prof. 
  E. 
  Rutherford, 
  F.R.S., 
  

   and 
  H. 
  Richardson, 
  M.Sc, 
  Beyer 
  Fellow, 
  University 
  of 
  

   Manchester 
  *. 
  

  

  [Plate 
  XIX.] 
  

  

  IN 
  previous 
  papers 
  f 
  we 
  have 
  analysed 
  the 
  7 
  radiations 
  

   emitted 
  by 
  the 
  radium 
  products 
  radium 
  B, 
  radium 
  C, 
  

   radium 
  D, 
  and 
  radium 
  E 
  into 
  a 
  number 
  o£ 
  groups 
  o£ 
  

   different 
  penetrating 
  powers. 
  An 
  examination 
  of 
  the 
  

   thorium 
  products, 
  viz., 
  mesothorium 
  2, 
  thorium 
  B, 
  thorium 
  C, 
  

   thorium 
  D, 
  and 
  of 
  the 
  actinium 
  products 
  has 
  been 
  undertaken 
  

   by 
  a 
  similar 
  method, 
  and 
  results 
  of 
  the 
  same 
  general 
  character 
  

   as 
  in 
  the 
  case 
  of 
  radium 
  have 
  been 
  obtained. 
  The 
  7 
  rays 
  of 
  

   these 
  substances 
  have 
  been 
  found 
  to 
  consist 
  of 
  distinct 
  groups 
  

   of 
  rays 
  absorbed 
  exponentially 
  by 
  aluminium 
  and 
  differing 
  

   widely 
  in 
  their 
  absorption 
  by 
  matter. 
  

  

  As 
  the 
  apparatus 
  and 
  methods 
  employed 
  were 
  the 
  same 
  as 
  

   those 
  previously 
  used 
  in 
  the 
  investigation 
  of 
  the 
  rays 
  from 
  

   radium 
  D 
  and 
  radium 
  E, 
  and 
  described 
  in 
  a 
  former 
  paper, 
  

   it 
  is 
  not 
  necessary 
  to 
  discuss 
  them 
  further 
  here. 
  

  

  Preliminary 
  investigations 
  of 
  the 
  7 
  rays 
  from 
  the 
  thorium 
  

   products 
  were 
  made 
  by 
  using 
  the 
  active 
  deposit 
  of 
  thorium, 
  

   obtained 
  by 
  exposure 
  of 
  a 
  negatively 
  charged 
  wire 
  to 
  the 
  

   emanation 
  from 
  a 
  preparation 
  of 
  mesothorium. 
  The 
  effect 
  

   obtained 
  was, 
  however, 
  too 
  small 
  for 
  accurate 
  measurement. 
  

  

  * 
  Communicated 
  by 
  the 
  Authors. 
  

  

  f 
  Rutherford 
  & 
  Richardson, 
  Phil. 
  Mag. 
  xxv. 
  p. 
  722 
  (1913), 
  and 
  

   xxvi. 
  p. 
  324 
  (1913). 
  

  

  Phil. 
  Mag. 
  S. 
  6. 
  Vol. 
  26. 
  No. 
  156. 
  Dec. 
  1913. 
  - 
  3 
  S 
  

  

  