﻿due 
  to 
  the 
  y 
  Rays 
  of 
  Radium 
  C. 
  233 
  

  

  the 
  radium 
  is 
  in 
  iron 
  or 
  lead, 
  and 
  whether 
  the 
  absorbing 
  

   screens 
  are 
  of 
  aluminium 
  or 
  lead. 
  

  

  3. 
  It 
  will 
  be 
  seen 
  that 
  1 
  or 
  2 
  mm. 
  of 
  lead 
  or 
  aluminium 
  

   absorb 
  the 
  cathode 
  rays 
  from 
  the 
  lead, 
  iron, 
  or 
  brick 
  radiators 
  

   acted 
  upon 
  by 
  y 
  rays. 
  

  

  4. 
  With 
  radium 
  in 
  steel, 
  and 
  with 
  aluminium 
  screens, 
  brick 
  

   gave 
  more 
  secondary 
  rays 
  than 
  iron. 
  In 
  the 
  other 
  three 
  cases 
  

   brick 
  gave 
  less 
  than 
  iron. 
  However, 
  5 
  cms. 
  of 
  iron 
  give 
  

   almost 
  maximum 
  secondary 
  rays, 
  whilst 
  6 
  cms. 
  of 
  brick 
  do 
  

   not 
  give 
  full 
  value. 
  Slate 
  gives 
  secondary 
  cathode 
  and 
  

   y 
  rays, 
  both 
  somewhat 
  less 
  intense 
  than 
  brick. 
  

  

  5. 
  When 
  the 
  radium 
  was 
  in 
  a 
  glass 
  test-tube, 
  without 
  steel 
  

   or 
  lead 
  around 
  it, 
  the 
  j3 
  and 
  y 
  rays 
  gave 
  from 
  a 
  secondary 
  

   radiator 
  of 
  lead 
  a 
  current 
  measuring 
  250 
  scale-divisions 
  a 
  

   minute 
  in 
  the 
  electroscope, 
  the 
  y 
  rays 
  gave 
  7*5 
  per 
  cent, 
  of 
  

   that 
  amount. 
  The 
  latter 
  could 
  be 
  divided 
  into 
  two 
  parts, 
  

   cathode 
  and 
  y 
  in 
  type. 
  The 
  y 
  type 
  was 
  the 
  following 
  per- 
  

   centages 
  of 
  the 
  total 
  (cathode 
  and 
  7): 
  for 
  lead 
  radiators 
  6'2, 
  

   for 
  iron 
  25, 
  for 
  brick 
  28. 
  

  

  6. 
  The 
  values 
  of 
  the 
  coefficients 
  of 
  absorption 
  by 
  a 
  sheet 
  of 
  

   aluminium, 
  0*41 
  mm. 
  thick, 
  are 
  as 
  follows 
  : 
  — 
  

  

  Primary 
  y 
  rays 
  21 
  

  

  Secondary 
  cathode 
  due 
  to 
  /3 
  and 
  y 
  rays 
  striking 
  — 
  

  

  (a) 
  Lead 
  21 
  

  

  (b) 
  Iron 
  35 
  

  

  Secondary 
  cathode 
  due 
  to 
  y 
  rays 
  striking 
  — 
  

  

  (a) 
  Lead 
  31 
  

  

  (&) 
  Iron 
  31 
  

  

  Thus 
  the 
  yS 
  rays 
  cause 
  secondary 
  cathode 
  rays 
  slower 
  than 
  

   the 
  primary 
  rays 
  which 
  cause 
  them, 
  and 
  the 
  y 
  rays 
  cause 
  

   secondary 
  cathode 
  rays 
  yet 
  slower. 
  But 
  all 
  these 
  rays 
  have 
  

   velocities 
  of 
  the 
  same 
  general 
  order, 
  and 
  greater 
  than 
  the 
  

   secondary 
  cathode 
  rays 
  due 
  to 
  the 
  X 
  rays. 
  This 
  has 
  already 
  

   been 
  proved 
  by 
  Dorn, 
  Allen, 
  Kleeman, 
  and 
  others. 
  

  

  7. 
  The 
  values 
  of 
  the 
  coefficients 
  of 
  absorption 
  of 
  the 
  

   secondary 
  7 
  rays 
  due 
  to 
  primary 
  7 
  rays 
  were 
  also 
  determined 
  

   for 
  lead 
  screens, 
  changing 
  the 
  thickness 
  from 
  2 
  to 
  4 
  mms. 
  

  

  A. 
  

  

  ("Lead 
  radiator 
  2*46 
  

  

  (a) 
  Radium 
  in 
  lead 
  (1 
  cm.)... 
  < 
  Iron 
  „ 
  3'70 
  

  

  (Brick 
  „ 
  3-68 
  

   f 
  Lead 
  „ 
  4*35 
  

  

  (b) 
  Radium 
  in 
  steel 
  (2'2 
  cms.) 
  < 
  Iron 
  „ 
  4*65 
  

  

  (.Brick 
  „ 
  4- 
  CO 
  

   Phil. 
  Mag. 
  S. 
  6. 
  Vol. 
  16. 
  Eo. 
  92. 
  Aug. 
  1908. 
  R 
  

  

  