﻿Alpha 
  Rays 
  by 
  Metals 
  and 
  Gases. 
  617 
  

  

  latter. 
  Moreover 
  it 
  is 
  also 
  seen 
  that 
  the 
  ratio 
  o£ 
  the 
  energy 
  

   of 
  the 
  alpha-particle 
  absorbed 
  by 
  any 
  given 
  centimetre 
  of 
  air 
  

   to 
  the 
  energy 
  absorbed 
  by 
  the 
  corresponding 
  centimetre 
  o£ 
  

   hydrogen, 
  is 
  always 
  greater 
  than 
  the 
  corresponding 
  ratio 
  for 
  

   the 
  centimetre 
  just 
  beyond 
  the 
  given 
  one. 
  This 
  is 
  in 
  

   agreement 
  with 
  the 
  results 
  obtained 
  for 
  the 
  air-equivalents 
  

   of 
  the 
  hydrogen 
  cells 
  ; 
  because 
  the 
  increase 
  in 
  their 
  air-equi- 
  

   valents 
  as 
  the 
  range 
  decreases 
  is 
  due 
  to 
  the 
  fact 
  that 
  the 
  ratio 
  

   of 
  the 
  energy 
  absorbed 
  by 
  the 
  hydrogen 
  cell 
  to 
  the 
  energy 
  that 
  

   would 
  be 
  consumed 
  by 
  the 
  air 
  which 
  it 
  displaces, 
  continually 
  

   increases 
  as 
  the 
  cell 
  is 
  moved 
  away 
  from 
  the 
  source 
  of 
  rays. 
  

   The 
  thicker 
  the 
  cell 
  the 
  more 
  rapid 
  would 
  be 
  the 
  rate 
  of 
  

   increase, 
  as 
  could 
  be 
  seen 
  by 
  comparing 
  the 
  areas 
  which 
  

   represent 
  the 
  ionizations 
  in, 
  say, 
  2 
  centimetres 
  of 
  air 
  and 
  

   hydrogen 
  respectively 
  in 
  fig. 
  2 
  in 
  two 
  different 
  positions. 
  

   The 
  increase 
  in 
  the 
  ratio 
  of 
  the 
  energies 
  consumed 
  in 
  air 
  and 
  

   hydrogen 
  respectively 
  is 
  in 
  agreement 
  also 
  with 
  the 
  decrease 
  

   in 
  the 
  hydrogen 
  equivalent 
  of 
  the 
  celloidin 
  film. 
  

  

  Still 
  making 
  use 
  of 
  our 
  hypothesis, 
  the 
  ratio 
  of 
  the 
  energy 
  

   consumed 
  in 
  the 
  9th 
  and 
  lOtli 
  centimetres 
  of 
  air 
  at 
  reduced 
  

   pressure, 
  to 
  that 
  consumed 
  in 
  the 
  same 
  centimetres 
  of 
  

   hydrogen 
  at 
  normal 
  pressure, 
  is 
  expressed 
  by 
  the 
  fraction 
  

  

  .^-^. 
  The 
  same 
  ratio 
  for 
  the 
  13th 
  and 
  11th 
  centimetres 
  

   is 
  ^. 
  These 
  ratios 
  w^ere 
  obtained 
  by 
  measuring 
  with 
  a 
  

  

  planimeter 
  the 
  areas 
  in 
  fig. 
  2. 
  The 
  former 
  ratio 
  divided 
  by 
  

   the 
  latter 
  gives 
  1*10. 
  Since 
  the 
  hydrogen 
  equivalent 
  of 
  the 
  

   colloidin 
  film 
  is 
  but 
  slightly 
  more 
  than 
  2 
  centimetres, 
  the 
  

   ratio 
  of 
  its 
  values 
  at 
  9 
  and 
  13 
  cm. 
  respectively 
  from 
  

   the 
  polonium 
  should 
  be 
  the 
  same 
  as 
  the 
  above 
  ratio. 
  The 
  

   hydrogen 
  equivalents 
  of 
  the 
  film 
  in 
  the 
  two 
  positions 
  (see 
  

   fig. 
  1) 
  are 
  2*320 
  and 
  2*120 
  cm. 
  respectively 
  ; 
  and 
  the 
  ratio 
  

   of 
  the 
  former 
  to 
  the 
  latter 
  is 
  1*09, 
  which 
  differs 
  little 
  from 
  

   the 
  calculated 
  ratio, 
  1*10^ 
  given 
  above. 
  Hence 
  it 
  is 
  seen 
  

   that 
  the 
  differences 
  between 
  the 
  curves 
  of 
  fig. 
  2 
  are 
  sufficient 
  

   to 
  account 
  for 
  the 
  change 
  in 
  the 
  hydrogen 
  equivalent 
  of 
  the 
  

   celloidin 
  film, 
  and 
  consequently 
  for 
  the 
  increase 
  in 
  the 
  air 
  

   equivalents 
  of 
  the 
  hydrogen 
  sheets 
  when 
  moved 
  away 
  from 
  

   the 
  source 
  of 
  rays. 
  This 
  agreement 
  between 
  the 
  relative 
  

   ionizations 
  and 
  the 
  relative 
  losses 
  of 
  energy 
  of 
  the 
  particle 
  in 
  

   the 
  two 
  gases 
  gives 
  a 
  considerable 
  degree 
  of 
  probability 
  to 
  

   our 
  hypothesis 
  connecting 
  the 
  relation 
  of 
  the 
  ionization 
  

   produced 
  to 
  the 
  energy 
  consumed. 
  

  

  The 
  experimental 
  results 
  show 
  that 
  the 
  air-equivalents 
  of 
  

   the 
  metal 
  sheets 
  decrease 
  with 
  the 
  speed 
  of 
  the 
  alpha-particle; 
  

  

  Phil 
  Mag. 
  S. 
  6. 
  Vol. 
  18. 
  No. 
  106. 
  Oct. 
  1909. 
  2 
  T 
  

  

  