﻿Range 
  of 
  the 
  Alplia 
  Particle 
  in 
  Simple 
  Gases. 
  403 
  

  

  raising 
  and 
  lowering 
  the 
  mercury 
  reservoir 
  connected 
  to 
  the 
  

   pressure 
  chamber. 
  The 
  source 
  of 
  rays, 
  either 
  radium 
  C 
  or 
  

   polonium, 
  was 
  fastened 
  to 
  the 
  end 
  of 
  an 
  iron 
  plug 
  L, 
  which 
  

   could 
  be 
  moved 
  along 
  the 
  tube 
  to 
  any 
  desired 
  position 
  by 
  

   means 
  of 
  an 
  electromagnet 
  placed 
  astride 
  the 
  tube. 
  For 
  

   radium 
  C, 
  the 
  source 
  was 
  an 
  active 
  platinum 
  wire 
  which 
  had 
  

   been 
  exposed 
  to 
  radium 
  emanation. 
  The 
  polonium 
  was 
  depo- 
  

   sited 
  upon 
  the 
  end 
  of 
  a 
  small 
  copper 
  plug 
  which 
  was 
  fastened 
  

   to 
  the 
  iron 
  plug 
  L 
  by 
  means 
  of 
  wax. 
  

  

  Fig-. 
  1. 
  

  

  TO 
  PRESSURE 
  CHAMBER, 
  

   PUMP. 
  AND 
  MA/VOMETER. 
  

  

  D 
  :CE 
  

  

  In 
  making 
  the 
  determination 
  of 
  the 
  range 
  in 
  any 
  case, 
  the 
  

   iron 
  plug 
  was 
  moved 
  along 
  the 
  tube 
  till 
  the 
  scintillations 
  

   were 
  visible. 
  This 
  adjustment 
  of 
  course 
  was 
  only 
  made 
  

   approximately. 
  The 
  pressure 
  of 
  the 
  gas 
  in 
  the 
  tube 
  was 
  

   then 
  carefully 
  adjusted 
  by 
  raising 
  or 
  lowering 
  the 
  mercury 
  

   reservoir 
  connected 
  to 
  the 
  pressure 
  chamber, 
  till 
  the 
  scin- 
  

   tillations 
  just 
  disappeared. 
  The 
  pressure 
  of 
  the 
  gas 
  was 
  then 
  

   read 
  from 
  the 
  manometer, 
  the 
  temperature 
  taken, 
  and 
  the 
  

   distance 
  of 
  the 
  source 
  from 
  the 
  zinc-sulphide 
  screen 
  de- 
  

   termined 
  by 
  means 
  of 
  a 
  cathetometer 
  placed 
  parallel 
  to 
  the 
  

   tube. 
  The 
  pressure 
  of 
  the 
  gas 
  was 
  adjusted 
  several 
  times 
  

   for 
  each 
  position 
  of 
  the 
  source 
  and 
  the 
  mean 
  value 
  of 
  the 
  

   pressure 
  taken 
  for 
  the 
  given 
  position. 
  The 
  source 
  was 
  then 
  

   moved 
  slightly 
  to 
  a 
  new 
  position 
  and 
  the 
  same 
  observations 
  

   taken. 
  Each 
  set 
  of 
  readings 
  was 
  then 
  reduced 
  to 
  normal 
  

   conditions 
  of 
  pressure 
  and 
  temperature, 
  760 
  mm. 
  pressure 
  

   and 
  0° 
  C. 
  temperature. 
  The 
  decrease 
  in 
  the 
  number 
  of 
  the 
  

   alpha 
  particles 
  towards 
  the 
  end 
  of 
  the 
  range 
  was 
  also 
  de- 
  

   termined. 
  The 
  results 
  of 
  the 
  latter 
  experiments 
  are 
  described 
  

   in 
  the 
  following 
  section. 
  

  

  The 
  values 
  of 
  the 
  ranges 
  of 
  the 
  alpha 
  particles 
  from 
  

   radium 
  C 
  and 
  polonium 
  were 
  obtained 
  in 
  the 
  above 
  manner 
  

   in 
  hydrogen, 
  helium, 
  oxygen, 
  and 
  air. 
  The 
  mean 
  values 
  

   found 
  are 
  recorded 
  in 
  Table 
  I. 
  Each 
  of 
  the 
  values 
  in 
  

   Table 
  I. 
  is 
  the 
  mean 
  of 
  at 
  least 
  twelve 
  separate 
  determ- 
  

   inations, 
  none 
  of 
  which 
  varied 
  more 
  than 
  1 
  part 
  in 
  400 
  

   for 
  air 
  and 
  oxygen 
  and 
  1 
  part 
  in 
  300 
  for 
  hydrogen 
  and 
  

   helium. 
  

  

  