﻿the 
  7 
  Rays 
  of 
  tlie 
  Thorium 
  and 
  Actinium 
  Products. 
  943 
  

  

  Element. 
  

  

  1 
  Atomic 
  

   weight. 
  

  

  Absorption 
  

  

  coefficient 
  [x 
  

  

  in 
  aluminium. 
  

  

  Mass. 
  absorption 
  

   coefficient 
  jj,/d 
  

   in 
  aluminium. 
  

  

  Radium. 
  B 
  

  

  Radiurn 
  C 
  

  

  214 
  

  

  214 
  

   210 
  

  

  210 
  

  

  228 
  

  

  212 
  

  

  208 
  

  

  ... 
  

  

  230 
  1 
  (cm.)" 
  1 
  

  

  40 
  [ 
  „ 
  

   0-51 
  J 
  „ 
  

  

  0-115 
  

  

  45 
  1 
  „ 
  

   0-99 
  J 
  „ 
  

  

  similar 
  types 
  to 
  D 
  

   but 
  very 
  feeble. 
  

  

  261 
  (cm.) 
  -1 
  

   0-116J 
  „ 
  

  

  1601 
  ., 
  

   82 
  I 
  , 
  

  

  0-36 
  J 
  „ 
  

  

  0-096 
  

  

  25 
  1 
  „ 
  

   0-190 
  [ 
  „ 
  

  

  1201 
  5J 
  

  

  31 
  1 
  ;, 
  

  

  045 
  J 
  „ 
  

   0-19S 
  

  

  851 
  (cm.)" 
  1 
  

   14-7 
  I 
  ,. 
  

   0-188 
  J 
  „ 
  

  

  0-0424 
  „ 
  

  

  16-5 
  1 
  „ 
  

   0-36/ 
  „ 
  

  

  9-5 
  1 
  „ 
  

   0031/ 
  ,. 
  

  

  59 
  1 
  „ 
  

  

  11-8 
  y 
  „ 
  

  

  0-13 
  J 
  „ 
  

  

  0-035 
  

  

  9-2 
  1 
  „ 
  

   0-070 
  j 
  „ 
  

  

  44 
  1 
  , 
  

  

  1T4 
  [ 
  „ 
  

  

  0T65J 
  „ 
  

  

  0-073 
  

  

  Radium 
  D 
  

  

  Radium 
  E 
  

  

  Mesothorium 
  2 
  . 
  

   Thorium 
  B 
  

  

  Thorium 
  D 
  

  

  Radioactinium 
  

  

  Actinium 
  B 
  

  

  Actinium 
  D 
  

  

  It 
  Trill 
  be 
  seen 
  that 
  the 
  7 
  rays 
  from 
  radioactive 
  products 
  

   can 
  be 
  conveniently 
  divided 
  into 
  four 
  types 
  : 
  — 
  

  

  (1) 
  The 
  soft 
  radiations 
  from 
  the 
  B 
  products 
  which 
  vary 
  

   from 
  yu, 
  = 
  120 
  to 
  ^=230. 
  

  

  (2) 
  A 
  more 
  penetrating- 
  type 
  varying 
  from 
  yu, 
  = 
  26 
  to 
  

   fu, 
  = 
  45, 
  probably 
  corresponding 
  to 
  characteristic 
  radiations 
  of 
  

   the 
  "L 
  ;; 
  series. 
  

  

  (3) 
  A 
  penetrating 
  type 
  from 
  the 
  B 
  products 
  varying 
  from 
  

   /u- 
  = 
  *36 
  to 
  fi='ol. 
  

  

  (4) 
  A 
  very 
  penetrating 
  type 
  varying 
  from 
  /jl 
  = 
  '115 
  to 
  

   /L6 
  = 
  *198, 
  probablv 
  corresnonding 
  to 
  characteristic 
  radiations 
  

   of 
  the 
  "K" 
  series. 
  

  

  Types 
  (1) 
  and 
  (2) 
  are 
  much 
  less 
  penetrating 
  than 
  the 
  

   X 
  rays 
  from 
  an 
  average 
  tube, 
  although 
  the 
  work 
  of 
  

   Bragg 
  * 
  and 
  Moseley 
  and 
  Darwin 
  t 
  has 
  clearly 
  shown 
  that 
  

   types 
  of 
  radiation 
  similar 
  in 
  penetrating 
  power 
  to 
  (2) 
  are 
  

   present 
  in 
  X 
  rays 
  generated 
  with 
  a 
  platinum 
  anticathode. 
  

   Using 
  a 
  hard 
  bulb 
  and 
  a 
  consequent 
  very 
  high 
  voltage 
  

  

  * 
  Bragg, 
  Proc. 
  Rot. 
  Soc. 
  A. 
  lxxxviii. 
  p. 
  428 
  (1913). 
  

   t 
  Moseley 
  & 
  Darwm, 
  Phil. 
  Mag. 
  xxvi. 
  p. 
  210 
  (1913). 
  

  

  