﻿630 
  Messrs. 
  F. 
  Soddy 
  and 
  A. 
  S. 
  Russell 
  on 
  the 
  

  

  The 
  initial 
  values 
  for 
  the 
  7-rays 
  before 
  penetrating 
  the 
  

   0*975 
  cm. 
  of 
  lead 
  were 
  deduced 
  by 
  means 
  of 
  the 
  absorption 
  

   coefficients 
  referred 
  to 
  in 
  the 
  last 
  section. 
  It 
  was 
  found 
  that 
  

   under 
  the 
  conditions 
  described 
  the 
  ratio 
  of 
  y8-rays 
  to 
  7-rays 
  

   (corrected 
  for 
  absorption 
  in 
  '975 
  cm. 
  lead) 
  was 
  for 
  radium 
  C 
  

   0*283 
  and 
  for 
  uranium 
  X 
  14'05. 
  The 
  relative 
  value 
  of 
  the 
  

   ratio 
  of 
  IB- 
  to 
  7-rays 
  for 
  uranium 
  X 
  in 
  terms 
  of 
  this 
  ratio 
  for 
  

   radium 
  C 
  as 
  unity 
  is 
  thus 
  49*7. 
  Uncorrected 
  for 
  absorption 
  

   this 
  ratio 
  is 
  Q2. 
  It 
  therefore 
  appears 
  that 
  the 
  initial 
  y-radia- 
  

   tion 
  of 
  nranium 
  as 
  compared 
  with 
  its 
  /S-radiation 
  is 
  fifty 
  

   times 
  less 
  than 
  for 
  the 
  case 
  of 
  radium. 
  When 
  the 
  y8-rays 
  

   were 
  measured 
  through 
  0*995 
  mm. 
  of 
  aluminium 
  instead 
  of 
  

   0*195 
  mm. 
  the 
  ratio 
  was 
  0*58 
  times 
  49*7, 
  which 
  is 
  to 
  be 
  

   expected, 
  since 
  the 
  /S-rays 
  oi 
  uranium 
  are 
  rather 
  less 
  pene- 
  

   trating 
  than 
  those 
  of 
  radium. 
  When 
  the 
  7-rays 
  through 
  

   6 
  mm. 
  of 
  aluminium 
  were 
  compared 
  with 
  the 
  y8-rays 
  through 
  

   0*19 
  mm. 
  of 
  aluminium 
  the 
  result 
  was 
  3*5 
  times 
  more 
  favour- 
  

   able 
  to 
  the 
  7-rays 
  of 
  uranium 
  than 
  through 
  0*975 
  cm. 
  of 
  

   lead. 
  Under 
  these 
  conditions 
  the 
  7-radiation 
  as 
  compared 
  

   with 
  the 
  /S-radiation 
  is 
  for 
  uranium 
  about 
  18 
  times 
  less 
  than 
  

   for 
  radium. 
  This 
  appears 
  to 
  be 
  evidence 
  that 
  uranium 
  gives 
  

   a 
  soft 
  7-radiation 
  not 
  given 
  by 
  radium, 
  but 
  the 
  point 
  will 
  be 
  

   discussed 
  in 
  more 
  detail 
  in 
  a 
  subsequent 
  communication. 
  

  

  The 
  7-activity 
  of 
  a 
  sealed 
  tube 
  containing 
  0*47 
  mg. 
  of 
  

   radium 
  bromide 
  was 
  taken 
  at 
  the 
  same 
  time 
  and 
  with 
  the 
  

   same 
  instrument 
  as 
  the 
  other 
  measurements. 
  This 
  gave 
  an 
  

   entirely 
  independent 
  estimate 
  of 
  the 
  relative 
  7-activity 
  of 
  

   the 
  uranium 
  X 
  preparations 
  in 
  terms 
  of 
  radium 
  bromide 
  

   through 
  a 
  much 
  smaller 
  thickness 
  of 
  lead 
  than 
  was 
  used 
  in 
  

   the 
  measurement 
  a 
  week 
  previously. 
  Nevertheless 
  the 
  result 
  

   was 
  nearly 
  the 
  same. 
  The 
  uranium 
  X 
  in 
  equilibrium 
  

   with 
  1 
  kilogram 
  of 
  uranium 
  corresponded 
  in 
  initial 
  7-acti- 
  

   vity 
  to 
  0*0150 
  mg. 
  radium 
  bromide, 
  as 
  compared 
  with 
  

   0*0138 
  mg. 
  found 
  previously. 
  The 
  former 
  value 
  is 
  probably 
  

   the 
  nearer 
  to 
  the 
  truth. 
  

  

  5. 
  The 
  Connexion 
  between 
  the 
  jS- 
  and 
  <y-Ilays 
  of 
  U7'anium 
  X. 
  

  

  On 
  account 
  of 
  this 
  great 
  relative 
  poverty 
  of 
  uranium 
  in 
  

   7-radiation 
  it 
  was 
  decided 
  to 
  test 
  more 
  closely 
  the 
  view 
  that 
  

   the 
  7-radiation 
  accompanied 
  the 
  /S-radiation 
  in 
  the 
  disinte- 
  

   gration 
  of 
  uranium 
  X. 
  In 
  the 
  first 
  place 
  the 
  7-activity 
  of 
  a 
  

   kilogram 
  of 
  uranyl 
  nitrate, 
  the 
  /3-activity 
  of 
  which 
  had 
  been 
  

   enfeebled 
  to 
  a 
  known 
  extent 
  by 
  crystallization, 
  was 
  compared 
  

   with 
  the 
  7-activity 
  of 
  another 
  kilogram 
  of 
  uranyl 
  nitrate 
  in 
  

   equilibrium 
  with 
  uranium 
  X. 
  For 
  this 
  purpose 
  the 
  sub- 
  

   stances 
  were 
  placed 
  immediately 
  below 
  an 
  electroscope, 
  the 
  

  

  