﻿Kinetic 
  Energy 
  of 
  Positive 
  Io7is. 
  649 
  

  

  simple 
  law. 
  For 
  greater 
  thickness 
  the 
  absorption 
  is 
  quite 
  

   exponential, 
  and 
  nearly 
  or 
  wholly 
  independent 
  o£ 
  the 
  nature 
  

   o£ 
  the 
  substance 
  traversed, 
  being 
  proportional 
  to 
  its 
  density. 
  

   In 
  one 
  series 
  the 
  absorbing 
  plates 
  themselves 
  formed 
  the 
  base 
  

   of 
  the 
  electroscope, 
  and 
  the 
  mean 
  value 
  of 
  X/<i 
  was 
  0*0536. 
  

  

  6. 
  In 
  a 
  thick-walled 
  lead 
  electroscope 
  with 
  a 
  base 
  1 
  cm. 
  

   thick, 
  the 
  absorbing 
  plates 
  being 
  placed 
  directly 
  over 
  the 
  

   preparation, 
  the 
  absorption 
  both 
  for 
  uranium 
  and 
  radium 
  was 
  

   strictly 
  exponential. 
  The 
  value 
  of 
  X/cl 
  for 
  all 
  but 
  the 
  heaviest 
  

   and 
  lightest 
  substances 
  was 
  0*047 
  for 
  uranium 
  and 
  0*040 
  for 
  

   radium, 
  the 
  ratio 
  being 
  1*18. 
  Lead 
  appears 
  exceptional 
  

   under 
  these 
  conditions, 
  and 
  the 
  value 
  of 
  Xjd 
  is 
  0*0636 
  for 
  

   uranium 
  7-rays, 
  and 
  0*0434 
  for 
  radium 
  7-rays, 
  the 
  ratio 
  

   being 
  1-465. 
  In 
  the 
  first 
  disposition 
  lead 
  appears 
  quite 
  

   normal. 
  

  

  7. 
  Some 
  evidence 
  of 
  the 
  existence 
  of 
  a 
  secondary 
  radiation 
  

   more 
  penetrating 
  than 
  /3-rays, 
  generated 
  by 
  the 
  7-rays, 
  has 
  

   been 
  obtained, 
  but 
  almost 
  certainly 
  none 
  exists 
  able 
  to 
  

   affect 
  measurements 
  taken 
  through 
  1 
  cm. 
  of 
  lead. 
  

  

  8. 
  The 
  7-ray 
  ionization 
  is 
  not 
  in 
  all 
  cases 
  constant, 
  but 
  

   sutFers 
  a 
  progressive 
  increase 
  with 
  certain 
  dispositions, 
  from 
  

   a 
  minimum 
  to 
  a 
  maximum 
  about 
  12 
  per 
  cent, 
  greater, 
  when 
  

   consecutive 
  observations 
  are 
  made 
  without 
  pause. 
  The 
  effect 
  

   depends 
  upon 
  the 
  presence 
  or 
  absence 
  of 
  a 
  charge 
  on 
  the 
  leaf 
  

   system; 
  for 
  if 
  the 
  charge 
  and 
  the 
  ionization 
  are 
  maintained, 
  

   the 
  rate 
  of 
  leak 
  tends 
  towards 
  a 
  maximum 
  ; 
  while 
  if 
  the 
  

   ionization 
  is 
  maintained 
  for 
  a 
  sufficient 
  period 
  after 
  the 
  charge 
  

   has 
  been 
  dissipated 
  the 
  rate 
  of 
  leak 
  becomes 
  a 
  minimum 
  again. 
  

  

  Physical 
  Chemistry 
  Laboratory^ 
  

  

  University 
  of 
  Glasgow. 
  

  

  June 
  1909. 
  

  

  \ 
  ■ 
  

  

  [Additions 
  made 
  August 
  1909.] 
  

  

  LXVI. 
  Tlie 
  Kinetic 
  Energy 
  of 
  the 
  Positive 
  Tons 
  emitted 
  from 
  

   various 
  Hot 
  Bodies. 
  By 
  F. 
  C. 
  Brown, 
  Ph.D. 
  ; 
  Porter 
  

   Ogden 
  Jacobus 
  Fellow^ 
  Princeton 
  University 
  *. 
  

  

  THIS 
  paper 
  describes 
  an 
  investigation 
  of 
  the 
  kinetic 
  

   energy 
  of 
  the 
  positive 
  ions 
  from 
  gold, 
  silver, 
  palladium, 
  

   tantalum, 
  nickel^ 
  platinum, 
  aluminium 
  phosphate, 
  osmium, 
  

   tungsten, 
  and 
  iron. 
  

  

  It 
  was 
  shown 
  in 
  a 
  paper 
  by 
  Richardson 
  and 
  Brown 
  f 
  that 
  

   if 
  the 
  kinetic 
  energy 
  of 
  the 
  ions 
  is 
  due 
  solely 
  to 
  thermal 
  

  

  * 
  Communicated 
  bv 
  Prof. 
  0. 
  W. 
  Richardson. 
  

   t 
  Phil. 
  Mag. 
  [6] 
  v6l. 
  xvi. 
  p. 
  353 
  (1908). 
  

  

  Pliil. 
  Mag. 
  S. 
  6. 
  Vol. 
  18. 
  No. 
  106. 
  Oct. 
  1909. 
  2 
  X 
  

  

  