﻿704 
  

  

  Prof. 
  Rutherford 
  and 
  Mr. 
  Nuttall 
  

  

  on 
  

  

  of 
  emanation 
  from 
  the 
  wire 
  by 
  washing 
  it 
  in 
  absolute 
  alcohol 
  

   and 
  heating 
  it 
  slightly. 
  

  

  The 
  method 
  o£ 
  procedure 
  in 
  an 
  experiment 
  was 
  as 
  follows. 
  

   An 
  active 
  wire 
  was 
  placed 
  in 
  position 
  between 
  the 
  glass 
  

   plates 
  AB 
  and 
  the 
  upper 
  part 
  of 
  the 
  apparatus 
  was 
  exhausted. 
  

   The 
  source 
  W 
  emitted 
  a 
  pencil 
  of 
  homogeneous 
  a 
  particles 
  

   which 
  passed 
  through 
  the 
  mica 
  window 
  M, 
  and 
  the 
  ioniza- 
  

   tion 
  they 
  produced 
  in 
  chamber 
  D 
  was 
  measured 
  in 
  the 
  

   electroscope 
  E. 
  The 
  whole 
  issuing 
  beam 
  of 
  u 
  rays 
  was 
  

   completely 
  absorbed 
  in 
  the 
  chamber 
  D, 
  and 
  the 
  ionization 
  

   due 
  to 
  ft 
  and 
  7 
  rays 
  was 
  never 
  more 
  than 
  2 
  per 
  cent, 
  of 
  the 
  

   whole 
  effect. 
  If 
  a 
  gas 
  is 
  now 
  introduced 
  into 
  the 
  upper 
  

   chamber, 
  i.e. 
  between 
  the 
  plates 
  A 
  and 
  B,and 
  the 
  ionization 
  

   current 
  again 
  measured, 
  any 
  decrease, 
  when 
  correction 
  is 
  

   made 
  for 
  decay 
  of 
  source, 
  will 
  be 
  due 
  either 
  to 
  partial 
  ab- 
  

   sorption 
  of 
  a 
  particles 
  by 
  the 
  gas 
  in 
  the 
  upper 
  chamber 
  or 
  

   to 
  the 
  scattering 
  of 
  u 
  particles 
  against 
  the 
  faces 
  of 
  the 
  plates 
  

   resulting 
  in 
  a 
  diminution 
  in 
  the 
  number 
  entering 
  the 
  ioniza- 
  

   tion 
  chamber. 
  The 
  decrease 
  of 
  ionization 
  due 
  to 
  loss 
  of 
  

   range 
  by 
  absorption 
  was 
  measured 
  in 
  a 
  separate 
  experiment. 
  

   For 
  this 
  purpose 
  the 
  plates 
  AB 
  forming 
  the 
  long 
  narrow 
  

   slit 
  were 
  removed, 
  and 
  the 
  ionization 
  current 
  measured 
  for 
  

   various 
  pressures 
  of 
  gas 
  in 
  the 
  upper 
  cylinder, 
  the 
  source 
  W 
  

  

  

  

  

  

  

  Fig. 
  

  

  2. 
  

  

  

  

  

  

  100 
  

  

  80 
  

   1 
  

  

  1 
  

  

  40 
  

   SO 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  V 
  

  

  

  

  

  

  

  

  

  

  

  \ 
  

  

  ^J 
  

  

  

  

  

  

  

  ^"A 
  

  

  

  

  

  

  

  

  

  C 
  

  

  

  

  , 
  

  

  

  

  

  

  

  

  B 
  

  

  

  

  

  2 
  4 
  6 
  3 
  10 
  IP. 
  14 
  16 
  18 
  

  

  Pressure 
  in 
  cms. 
  

   being 
  placed 
  in 
  exactly 
  the 
  same 
  position 
  as 
  before. 
  In 
  

   this 
  way 
  a 
  curve 
  can 
  be 
  obtained 
  showing 
  the 
  relation 
  

   between 
  the 
  pressure 
  of 
  the 
  gas 
  in 
  the 
  upper 
  cylinder 
  and 
  

   the 
  ionization 
  produced 
  by 
  the 
  source 
  in 
  the 
  chamber 
  D. 
  

   A 
  typical 
  curve 
  is 
  shown 
  in 
  the 
  curve 
  A 
  of 
  fig. 
  2*. 
  

  

  * 
  Compare 
  B. 
  L. 
  Bronson, 
  Phil. 
  Mag. 
  xi. 
  p. 
  806 
  (1906). 
  

  

  