﻿612 
  

  

  Mr. 
  T. 
  S. 
  Taylor 
  on 
  the 
  Retardation 
  of 
  

  

  The 
  curves 
  in 
  figure 
  1 
  (p. 
  611) 
  represent 
  the 
  results 
  

   recorded 
  in 
  Tables 
  II., 
  III., 
  and 
  lY. 
  By 
  noting 
  the 
  slopes 
  

   o£ 
  the 
  curves 
  some 
  comparison 
  o£ 
  the 
  rates 
  at 
  which 
  the 
  air- 
  

   equivalents 
  o£ 
  the 
  various 
  sheets 
  change 
  can 
  be 
  obtained. 
  

  

  Taking 
  the 
  general 
  slope 
  of 
  each 
  curve 
  and 
  dividing 
  it 
  into 
  

   the 
  air-equivalent 
  o£ 
  the 
  corresponding 
  sheet 
  when 
  0*9 
  cm. 
  

   £rom 
  the 
  radium, 
  it 
  is 
  £ound 
  that 
  for 
  a 
  given 
  metal 
  the 
  

   quotient 
  thus 
  obtained 
  is 
  nearly 
  constant 
  £or 
  all 
  the 
  sheets 
  o£ 
  

   the 
  metal. 
  This 
  is 
  shown 
  in 
  column 
  4, 
  Table 
  Y. 
  Thus 
  £or 
  

  

  Table 
  Y. 
  

  

  Sheets. 
  

  

  Slopes 
  of 
  

   Curves. 
  

  

  Air- 
  

   equivalents. 
  

  

  Eatio. 
  

  

  V 
  atomic 
  weight. 
  

  

  

  ratio 
  V 
  atomic 
  wt. 
  

  

  A 
  Au 
  ... 
  

  

  0-032 
  

  

  0-719 
  

  

  2-24 
  X 
  10^ 
  

  

  

  B 
  Au 
  ... 
  

  

  0051 
  

  

  0-980 
  

  

  1-92 
  X 
  10^ 
  

  

  

  

  C 
  Au 
  ... 
  

  

  0-064 
  

  

  1-375 
  

  

  2-15 
  X 
  W 
  

  

  

  

  D 
  Au 
  ... 
  

  

  0-100 
  

  

  1-900 
  

  

  1-90 
  X 
  10^ 
  

  

  14-05 
  

  

  28-80 
  

  

  A 
  Sn 
  ... 
  

  

  0032 
  

  

  1-011 
  

  

  3-16 
  X 
  10^ 
  

  

  

  

  BSn 
  ... 
  

  

  0063 
  

  

  1-995 
  

  

  3-17 
  X 
  101 
  

  

  1091 
  

  

  34-34 
  

  

  APb 
  ... 
  

  

  0053 
  

  

  1-104 
  

  

  2-08 
  X 
  101 
  

  

  

  

  BPb 
  ... 
  

  

  0071 
  

  

  1-396 
  

  

  1-96 
  X 
  10^^ 
  

  

  

  

  C 
  Pb 
  ... 
  

  

  0-1] 
  

  

  2-325 
  

  

  2-11 
  X 
  10^ 
  

  

  14-38 
  

  

  29 
  38 
  

  

  AAl 
  ... 
  

  

  0010 
  

  

  0-597 
  

  

  5-97 
  X 
  10^ 
  

  

  

  

  B 
  Al 
  ... 
  

  

  0020 
  

  

  1-209 
  

  

  6-04 
  X 
  10^ 
  

  

  

  

  C 
  Al 
  ... 
  

  

  0033 
  

  

  1-803 
  

  

  5-48 
  X 
  10^ 
  

  

  5-19 
  

  

  30-41 
  

  

  DAI 
  ... 
  

  

  ! 
  0045 
  

  

  2-672 
  

  

  5-93 
  X 
  10^ 
  

  

  

  

  AH 
  ... 
  

  

  -0-020 
  

  

  0-231 
  

  

  M6 
  X 
  10^ 
  

  

  1 
  

  

  

  BH 
  ... 
  

  

  - 
  0034 
  

  

  0-428 
  

  

  1-17 
  X 
  10^ 
  

  

  

  

  CH 
  ... 
  

  

  -0-064 
  

  

  i 
  

  

  0-762 
  

  

  1-19 
  X 
  10' 
  

  

  

  ■ 
  

  

  sheets 
  o£ 
  the 
  same 
  metal 
  the 
  rate 
  at 
  which 
  the 
  air-equivalent 
  

   of 
  each 
  sheet 
  changes 
  with 
  a 
  change 
  in 
  the 
  range 
  of 
  the 
  

   entering 
  alpha-particles, 
  is 
  proportional 
  to 
  its 
  air-equivalent 
  

   when 
  nearest 
  the 
  radium. 
  The 
  approximately 
  constant 
  numbers 
  

   in 
  column 
  6, 
  Table 
  Y., 
  show 
  that 
  the 
  percentage 
  rate 
  o£ 
  

   change 
  in 
  the 
  air-equivalent 
  for 
  any 
  metal 
  is 
  nearly 
  propor- 
  

   tional 
  to 
  the 
  square 
  root 
  of 
  the 
  atomic 
  weight. 
  The 
  agreement 
  

   of 
  the 
  values 
  in 
  columns 
  4 
  and 
  6^ 
  Table 
  Y., 
  is 
  as 
  good 
  as 
  

   could 
  be 
  expected 
  since 
  the 
  slopes 
  of 
  the 
  curves 
  in 
  figure 
  1 
  

   could 
  only 
  be 
  determined 
  roughly. 
  The 
  proportionality 
  is 
  

   indeed 
  only 
  approximate, 
  since 
  the 
  curve 
  for 
  any 
  one 
  sheet 
  

   does 
  not 
  have 
  a 
  constant 
  slope. 
  

  

  For 
  the 
  thin 
  sheet 
  of 
  aluminium 
  the 
  air-equivalent 
  is 
  almost 
  

   constant 
  for 
  the 
  higher 
  ranges 
  or 
  speeds, 
  but 
  as 
  the 
  speed 
  of 
  

   the 
  entering 
  alpha-particle 
  decreases 
  the 
  air-equivalent 
  de- 
  

   creases 
  slowly, 
  and 
  in 
  the 
  lower 
  ranges 
  the 
  decrease 
  becomes 
  

   quite 
  apparent. 
  For 
  the 
  thicker 
  sheets 
  of 
  aluminium 
  the 
  

   chanoe 
  is 
  more 
  marked 
  even 
  for 
  the 
  hioher 
  ranges. 
  The 
  

   statements 
  of 
  McOlung, 
  Levin, 
  and 
  Rutherford 
  that 
  equal 
  

  

  