﻿404 
  

  

  Dr. 
  T. 
  S. 
  Taylor 
  on 
  the 
  Range 
  and 
  

   Table 
  I. 
  

  

  Range 
  at 
  

  

  760 
  mm. 
  and 
  0° 
  0. 
  

  

  760 
  mm. 
  and 
  15° 
  C. 
  

  

  Ratio 
  of 
  

   Ranges. 
  

  

  

  Polonium. 
  

  

  Radium 
  C. 
  

  

  Polonium. 
  

  

  Radium 
  C. 
  

  

  Air 
  

  

  357 
  cm. 
  

  

  3-25 
  

   l"-95 
  

   16 
  70 
  

  

  6-57 
  em. 
  

  

  5-94 
  

   29-36 
  

   30-84 
  

  

  3"77 
  cm. 
  

  

  3-43 
  

   16-83 
  

   17-62 
  

  

  6'93 
  cm. 
  

  

  6-26 
  

   30-93 
  

   32-54 
  

  

  1-84 
  

  

  1-83 
  

   184 
  

   1-84 
  

  

  o 
  2 
  

  

  H 
  

  

  He 
  

  

  

  Each 
  of 
  the 
  gases 
  contained 
  only 
  a 
  relatively 
  small 
  

   quantity 
  of 
  impurities. 
  The 
  oxygen 
  formed 
  by 
  dropping, 
  

   very 
  slowly, 
  distilled 
  water 
  upon 
  the 
  commercial 
  " 
  oxylith 
  " 
  

   contained 
  certainly 
  not 
  more 
  than 
  one-third 
  per 
  cent, 
  of 
  

   impurities. 
  The 
  hydrogen 
  was 
  formed 
  by 
  the 
  electrolysis 
  

   of 
  distilled 
  water 
  containing 
  a 
  small 
  trace 
  of 
  sulphuric 
  acid. 
  

   It 
  probably 
  had 
  as 
  much 
  as 
  J 
  to 
  J 
  per 
  cent, 
  of 
  impurities. 
  

   The 
  helium 
  was 
  passed 
  repeatedly 
  through 
  charcoal 
  in 
  liquid 
  

   air, 
  and 
  certainly 
  was 
  as 
  pure 
  as 
  can 
  be 
  obtained 
  by 
  this 
  

   process. 
  The 
  impurities 
  in 
  the 
  gases 
  were 
  not 
  sufficient 
  to 
  

   cause 
  a 
  variation 
  in 
  the 
  results 
  much 
  greater 
  than 
  that 
  due 
  

   to 
  experimental 
  errors. 
  

  

  The 
  Diminution 
  of 
  the 
  Number 
  of 
  Alpha 
  Particles 
  from 
  

   Radium 
  C 
  near 
  the 
  End 
  of 
  the 
  Range 
  in 
  Hydrogen, 
  Helium, 
  

   Oxygen, 
  and 
  Air. 
  

  

  The 
  apparatus 
  used 
  in 
  these 
  determinations 
  was 
  the 
  same 
  

   as 
  that 
  shown 
  in 
  fig. 
  1. 
  The 
  method 
  of 
  determining 
  the 
  

   decrease 
  of 
  the 
  number 
  of 
  the 
  particles 
  towards 
  the 
  end 
  of 
  

   the 
  range 
  in 
  each 
  gas 
  may 
  be 
  illustrated 
  by 
  describing 
  an 
  

   experiment 
  for 
  air. 
  The 
  active 
  wire 
  was 
  placed 
  so 
  as 
  to 
  be 
  

   say 
  6\5 
  cm. 
  from 
  the 
  zinc-sulphide 
  screen 
  and 
  the 
  end 
  of 
  the 
  

   tube 
  sealed. 
  The 
  number 
  of 
  scintillations 
  upon 
  the 
  zinc- 
  

   sulphide 
  screen 
  within 
  the 
  field 
  of 
  the 
  microscope 
  was 
  

   determined. 
  By 
  observing 
  the 
  pressure 
  of 
  the 
  enclosed 
  

   gas, 
  the 
  temperature, 
  and 
  the 
  exact 
  distance 
  of 
  the 
  source 
  

   from 
  the 
  screen, 
  the 
  equivalent 
  range, 
  at 
  15° 
  C. 
  and 
  760 
  mm. 
  

   pressure, 
  of 
  the 
  particles 
  falling 
  upon 
  the 
  screen 
  could 
  be 
  

   calculated. 
  The 
  pressure 
  was 
  then 
  increased 
  slightly 
  and 
  

   the 
  scintillations 
  again 
  counted. 
  From 
  the 
  new 
  pressure, 
  

   temperature, 
  and 
  distance 
  of 
  source 
  from 
  the 
  screen 
  the 
  

   equivalent 
  range, 
  at 
  15° 
  C. 
  and 
  760 
  mm., 
  of 
  the 
  particles 
  

   falling 
  upon 
  the 
  screen 
  was 
  calculated 
  as 
  before. 
  This 
  

   process 
  was 
  continued 
  till 
  there 
  were 
  no 
  more 
  scintillations 
  

   visible 
  save 
  the 
  few 
  due 
  to 
  the 
  occluded 
  emanation 
  in 
  the 
  

  

  