﻿6i6 
  Messrs. 
  F. 
  Soddy 
  and 
  A. 
  S. 
  Russell 
  on 
  the 
  

  

  Table 
  III.— 
  Uranium 
  X 
  7-Rays. 
  

  

  Disposition 
  as 
  in 
  Table 
  II. 
  except 
  that 
  the 
  Uranium 
  X 
  

   occupied 
  a 
  surface 
  o£ 
  about 
  30 
  sq. 
  cm. 
  

  

  No. 
  

  

  Material. 
  

  

  Density, 
  

  

  Range 
  (cm.). 
  

  

  X(cm.)-l. 
  

  

  lOOxX/d. 
  

  

  A 
  UrX 
  

   XRa 
  ■ 
  

  

  1. 
  

  

  Mercury. 
  

  

  13-59 
  

  

  •343 
  to 
  3-535 
  

  

  -832 
  

  

  6-12 
  

  

  1-297 
  

  

  2. 
  

  

  Lead. 
  

  

  11-40 
  

  

  to 
  4-5 
  

  

  •725 
  

  

  6-36 
  

  

  1-465 
  

  

  3. 
  

  

  Copper. 
  

  

  8-81 
  

  

  to 
  7-6 
  

  

  -416 
  

  

  4-72 
  

  

  1-186 
  

  

  4. 
  

  

  Brass. 
  

  

  8-35 
  

  

  to 
  5-86 
  

  

  •392 
  

  

  4-70 
  

  

  1-208 
  

  

  5. 
  

  

  Iron. 
  

  

  7-62 
  

  

  to 
  7-57 
  

  

  •360 
  

  

  4-72 
  

  

  1-183 
  

  

  6. 
  

  

  Tin. 
  

  

  7-245 
  

  

  to 
  5-51 
  

  

  •341 
  

  

  4-70 
  

  

  1-212 
  

  

  7. 
  

  

  Zinc. 
  

  

  7-07 
  

  

  to 
  6-00 
  

  

  •329 
  

  

  4-65 
  

  

  1183 
  

  

  8. 
  

  

  Slate. 
  

  

  2-854 
  

  

  to 
  9-44 
  

  

  •134 
  

  

  4-69 
  

  

  1-13;) 
  

  

  9. 
  

  

  Aluminium. 
  

  

  2-77 
  

  

  to 
  11-19 
  

  

  •130 
  

  

  4-69 
  

  

  1-169 
  

  

  10. 
  

  

  Glass. 
  

  

  2-52 
  

  

  to 
  11-26 
  

  

  -122 
  

  

  4-84 
  

  

  1-160 
  

  

  11. 
  

  

  Magnesia 
  Brick. 
  

  

  1-92 
  

  

  to 
  11-86 
  

  

  •0917 
  

  

  4-78 
  

  

  1-207 
  

  

  12. 
  

  

  Sulphur. 
  

  

  1-785 
  

  

  to 
  11-59 
  

  

  -0921 
  

  

  5-16 
  

  

  1-178 
  

  

  l;i 
  

  

  Paraffin-wax. 
  

  

  0-862 
  

  

  to 
  11-39 
  

  

  -0433 
  

  

  502 
  

  

  1082 
  

  

  il4. 
  

  

  Pine-wood. 
  

  

  0-386 
  

  

  to 
  12-51 
  

  

  -02926 
  

  

  7-58 
  

  

  

  Mean 
  value 
  o£ 
  \/d 
  (Xos. 
  3 
  to 
  9) 
  

   XUrX 
  

   XEa 
  

  

  •0470. 
  

  

  1-181. 
  

  

  observation, 
  gave 
  the 
  value 
  0441 
  for 
  \/d, 
  a 
  value 
  5 
  per 
  cent, 
  

   less 
  than 
  the 
  former 
  value. 
  Equally 
  good 
  experiments 
  with 
  

   the 
  same 
  metals 
  in 
  Table 
  I. 
  gave 
  values 
  for 
  \/d 
  differing 
  by 
  

   8 
  per 
  cent. 
  Now 
  for 
  uranium 
  X 
  the 
  extreme 
  values 
  of 
  \/d 
  

   for 
  bodies 
  within 
  the 
  density 
  range 
  specified 
  are 
  '0465 
  and 
  

   •0472, 
  which 
  is 
  only 
  a 
  variation 
  of 
  about 
  2 
  per 
  cent. 
  For 
  

   radium 
  the 
  extremes 
  are 
  '0387 
  and 
  '0414. 
  

  

  For 
  substances 
  of 
  density 
  beyond 
  the 
  limits 
  2*6 
  to 
  8*8 
  on 
  

   either 
  side 
  the 
  values 
  of 
  \/d 
  are 
  considerably 
  larger, 
  the 
  

   departures 
  being 
  more 
  apparent 
  for 
  the 
  case 
  of 
  uranium 
  X 
  

   than 
  for 
  radium. 
  These 
  departures 
  seem 
  to 
  be 
  genuine, 
  for 
  

   all 
  the 
  results 
  showing 
  them 
  have 
  been 
  repeated, 
  and 
  the 
  

   same 
  or 
  very 
  similar 
  results 
  obtained. 
  They 
  probably 
  have 
  

   their 
  origin 
  in 
  the 
  disposition 
  used. 
  Thus 
  in 
  the 
  original 
  

   work 
  with 
  uranium 
  X 
  (Table 
  I.), 
  when 
  the 
  absorbing 
  

   materials 
  were 
  clamped 
  up^ 
  \/d 
  was, 
  on 
  the 
  whole, 
  fairly 
  

   constant 
  over 
  the 
  entire 
  range 
  from 
  mercury 
  to 
  pine-wood, 
  

   with 
  a 
  mean 
  of 
  '0536, 
  while 
  in 
  the 
  later 
  work 
  both 
  with 
  

   radium 
  and 
  uranium 
  X, 
  in 
  which 
  the 
  materials 
  are 
  laid 
  

   directly 
  on 
  the 
  source 
  of 
  radiation, 
  differences 
  appear. 
  The 
  

   general 
  arrangement 
  of 
  the 
  experiment 
  and 
  the 
  method 
  of 
  

   workino- 
  in 
  the 
  former 
  case, 
  however, 
  were 
  much 
  less 
  accurate 
  

  

  