﻿of 
  the 
  y 
  Rays 
  from 
  Radium 
  D 
  and 
  Radium 
  E. 
  327 
  

  

  former 
  paper. 
  An 
  aluminium 
  electroscope 
  (10 
  X 
  10 
  x 
  10 
  cm.) 
  

   was 
  arranged 
  as 
  shown 
  in 
  fig. 
  1. 
  The 
  face 
  E 
  of 
  the 
  electro- 
  

   scope 
  was 
  made 
  of 
  a 
  thin 
  sheet 
  of 
  mica 
  equivalent 
  in 
  stopping- 
  

  

  Fig. 
  1. 
  

  

  Sect/ 
  on 
  of 
  Pole 
  P/ec£ 
  

  

  power 
  of 
  the 
  a 
  rays 
  to 
  about 
  2 
  cm. 
  of 
  air. 
  The 
  electroscope 
  

   was 
  filled 
  by 
  displacement 
  with 
  a 
  mixture 
  of 
  hydrogen 
  and 
  

   methyl 
  iodide 
  at 
  atmospheric 
  pressure. 
  On 
  account 
  of 
  the 
  

   small 
  ionization 
  effect 
  of 
  the 
  y 
  rays 
  from 
  the 
  radioactive 
  

   materials 
  under 
  examination, 
  it 
  was 
  necessary 
  to 
  allow 
  a 
  

   comparatively 
  wide 
  beam 
  of 
  y 
  rays 
  to 
  enter 
  the 
  electroscope. 
  

   The 
  /3 
  rays 
  were 
  removed 
  by 
  a 
  strong 
  magnetic 
  field, 
  the 
  

   pole-pieces 
  being 
  about 
  6 
  cm. 
  apart. 
  In 
  most 
  experiments 
  

   the 
  source 
  was 
  placed 
  in 
  the 
  magnetic 
  field 
  about 
  12 
  cm. 
  

   from 
  the 
  electroscope, 
  and 
  the 
  absorbing 
  layers 
  were 
  placed 
  

   directly 
  in 
  front 
  of 
  the 
  source, 
  as 
  shown 
  in 
  the 
  figure. 
  All 
  

   exposed 
  surfaces 
  were 
  covered 
  with 
  thick 
  cardboard 
  in 
  order 
  

   to 
  reduce 
  the 
  possibility 
  of 
  excitation 
  of 
  y 
  rays 
  by 
  /3rays 
  to 
  

   a 
  minimum. 
  

  

  Analysis 
  of 
  the 
  y 
  Rays 
  from 
  Radium 
  I). 
  

  

  The 
  absorption 
  curve 
  of 
  the 
  y 
  rays 
  from 
  radium 
  D 
  was 
  

   obtained 
  immediately 
  after 
  its 
  separation 
  from 
  radium 
  E. 
  

   Xo 
  sensible 
  change 
  either 
  in 
  the 
  intensity 
  of 
  the 
  y 
  rays 
  or 
  

   in 
  the 
  shape 
  of 
  the 
  absorption 
  curve 
  was 
  observed 
  with 
  the 
  

   growth 
  of 
  radium 
  E 
  in 
  the 
  preparation. 
  This 
  indicates, 
  as 
  

   is 
  shown 
  later 
  by 
  another 
  method, 
  that 
  the 
  y 
  radiation 
  from 
  

   radium 
  E 
  is 
  very 
  weak 
  in 
  intensity 
  compared 
  with 
  the 
  y 
  rays 
  

   from 
  radium 
  D. 
  In 
  all 
  five 
  determinations 
  were 
  made 
  with 
  

   different 
  preparations 
  of 
  radium 
  D. 
  The 
  numbers 
  obtained 
  

   in 
  the 
  individual 
  experiments 
  under 
  somewhat 
  different 
  

  

  