﻿of 
  the 
  7 
  Rays 
  from 
  Radium 
  D 
  and 
  Radium 
  E. 
  331 
  

  

  that 
  the 
  emission 
  of 
  ft 
  rays 
  from 
  radium 
  E 
  is 
  accompanied 
  

   by 
  an 
  exceedingly 
  minute 
  7 
  radiation 
  of 
  which 
  the 
  soft 
  type 
  

   has 
  about 
  the 
  same 
  absorption 
  coefficient 
  as 
  that 
  from 
  

   radium 
  D. 
  It 
  appears 
  fairly 
  certain 
  that 
  this 
  7 
  radiation 
  is 
  

   to 
  be 
  ascribed 
  to 
  the 
  atoms 
  of 
  radium 
  E, 
  and 
  is 
  not 
  excited 
  by 
  

   the 
  ft 
  rays 
  in 
  the 
  surrounding 
  inactive 
  matter. 
  

  

  Relative 
  Intensity 
  of 
  the 
  7 
  Rays 
  from 
  Radium 
  D 
  

   and 
  Radium 
  E. 
  

  

  It 
  is 
  of 
  importance 
  to 
  obtain 
  an 
  estimate 
  of 
  the 
  relative 
  

   magnitude 
  of 
  the 
  ft 
  and 
  7 
  radiation 
  emitted 
  by 
  radium 
  D 
  and 
  

   radium 
  E. 
  This 
  was 
  done 
  by 
  measuring 
  the 
  /3-ray 
  activity 
  

   of 
  the 
  sources 
  under 
  precisely 
  the 
  same 
  conditions 
  as 
  the 
  

   7-ray 
  activity. 
  The 
  ionization 
  in 
  the 
  electroscope 
  of 
  fig. 
  1 
  

   was 
  determined 
  with 
  and 
  without 
  the 
  magnetic 
  field. 
  The 
  

   preparations 
  were 
  placed 
  12 
  cm. 
  from 
  the 
  mica 
  face 
  E 
  of 
  the 
  

   electroscope, 
  and 
  the 
  pole-pieces 
  were 
  6 
  cm. 
  apart. 
  Under 
  

   these 
  conditions, 
  the 
  /3-ray 
  activity 
  of 
  the 
  radium 
  D 
  pre- 
  

   paration 
  was 
  300 
  divisions 
  per 
  minute, 
  and 
  the 
  7-ray 
  

   activity 
  19 
  divisions 
  per 
  minute. 
  On 
  the 
  other 
  hand, 
  the 
  

   •/3-ray 
  activity 
  of 
  the 
  corresponding 
  radium 
  E 
  preparation 
  

   was 
  1400 
  divisions 
  per 
  minute, 
  and 
  the 
  7 
  ray 
  activity 
  only 
  

   0'48 
  division 
  per 
  minute. 
  Even 
  without 
  allowing 
  for 
  the 
  

   partial 
  absorption 
  of 
  the 
  soft 
  ft 
  rays 
  from 
  radium 
  D 
  in 
  the 
  air 
  

   before 
  entering 
  the 
  electroscope, 
  it 
  is 
  obvious 
  that 
  there 
  is 
  

   a 
  very 
  marked 
  difference 
  between 
  the 
  ratios 
  of 
  the 
  ft- 
  and 
  

   7-ray 
  activity 
  of 
  the 
  two 
  preparations. 
  

  

  Summary. 
  

  

  It 
  has 
  been 
  shown 
  that 
  radium 
  D 
  emits 
  two 
  types 
  of 
  

   -7 
  radiation 
  for 
  which 
  yu, 
  = 
  45, 
  and 
  0*99 
  (cm.) 
  -1 
  in 
  aluminium. 
  

   Relatively 
  to 
  radium 
  D, 
  radium 
  E 
  emits 
  a 
  very 
  weak 
  7 
  

   radiation, 
  and 
  not 
  more 
  than 
  two 
  per 
  cent, 
  of 
  the 
  7 
  radiation 
  

   given 
  out 
  by 
  radium 
  D 
  + 
  E 
  in 
  equilibrium 
  is 
  to 
  be 
  ascribed 
  

   to 
  radium 
  E. 
  In 
  other 
  words, 
  the 
  transformation 
  of 
  each 
  

   atom 
  of 
  radium 
  D 
  is 
  accompanied, 
  on 
  the 
  average, 
  by 
  50 
  times 
  

   the 
  amount 
  of 
  7 
  radiation 
  from 
  an 
  atom 
  of 
  radium 
  E. 
  The 
  

   soft 
  type 
  of 
  radiation 
  /a 
  = 
  45 
  from 
  radium 
  D 
  and 
  radium 
  E 
  is 
  

   slightly 
  less 
  penetrating 
  than 
  the 
  corresponding 
  radiation 
  

   from 
  radium 
  B. 
  There 
  appears 
  to 
  be 
  little 
  doubt 
  that 
  this 
  

   radiation 
  corresponds 
  to 
  the 
  characteristic 
  radiation 
  of 
  the 
  

   L 
  type 
  to 
  be 
  expected 
  from 
  an 
  element 
  of 
  atomic 
  weight 
  210. 
  

   The 
  values 
  of 
  the 
  absorption 
  coefficients 
  of 
  the 
  types 
  of 
  7 
  

   radiation 
  from 
  radium 
  B, 
  radium 
  C, 
  radium 
  D, 
  and 
  radium 
  E 
  

  

  Z2 
  

  

  