﻿Ionization 
  of 
  the 
  Alpha 
  Particle 
  in 
  Simple 
  Gases. 
  407 
  

  

  potential 
  of 
  160 
  volts, 
  except 
  while 
  taking 
  the 
  observations 
  

   when 
  it 
  was 
  insulated. 
  There 
  was 
  thus 
  a 
  potential 
  difference 
  

   of 
  320 
  volts 
  between 
  the 
  electrode 
  and 
  the 
  walls 
  of 
  the 
  

   ionization 
  vessel. 
  This 
  was 
  sufficient 
  to 
  ensure 
  a 
  high 
  degree 
  

   of 
  saturation, 
  but 
  not 
  enough 
  to 
  produce 
  ionization 
  by 
  col- 
  

   lision, 
  even 
  in 
  helium. 
  A 
  wire 
  gauze 
  connected 
  to 
  earth 
  

   was 
  placed 
  about 
  2 
  mm. 
  from 
  the 
  gauze 
  forming 
  the 
  top 
  of 
  

   the 
  ionization 
  vessel 
  and 
  served 
  with 
  it 
  as 
  a 
  guard 
  chamber. 
  

  

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  Battery. 
  

  

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  Electroscope. 
  

  

  The 
  source 
  of 
  rays, 
  polonium, 
  was 
  upon 
  the 
  end 
  of 
  a 
  small 
  

   copper 
  plug 
  inserted 
  in 
  a 
  larger 
  plug 
  F, 
  that 
  had 
  a 
  small 
  

   opening 
  2*5 
  mm. 
  in 
  diameter 
  through 
  it 
  in 
  order 
  to 
  limit 
  

   the 
  beam 
  of 
  rays 
  so 
  that 
  it 
  would 
  fall 
  well 
  within 
  the 
  ioniza- 
  

   tion 
  chamber. 
  The 
  polonium 
  could 
  be 
  moved 
  towards 
  or 
  

   away 
  from 
  the 
  ionization 
  chamber 
  at 
  will 
  by 
  means 
  of 
  a 
  

   string 
  wrapping 
  around 
  the 
  glass 
  rod 
  T 
  that 
  extended 
  into 
  

   the 
  vessel 
  through 
  a 
  ground-glass 
  joint. 
  The 
  top 
  of 
  the 
  

   vessel 
  was 
  closed 
  by 
  waxing 
  down 
  a 
  glass 
  plate 
  over 
  it. 
  A 
  

   side 
  tube 
  joined 
  the 
  vessel 
  to 
  the 
  pressure 
  chamber, 
  pump, 
  

   and 
  manometer. 
  The 
  distance 
  of 
  the 
  source 
  from 
  the 
  ioni- 
  

   zation 
  chamber 
  could 
  be 
  determined 
  by 
  means 
  of 
  a 
  scale 
  

   parallel 
  to 
  the 
  apparatus. 
  

  

  Since 
  the 
  ionization 
  vessel 
  was 
  24 
  millimetres 
  high 
  it 
  was 
  

   necessary 
  to 
  use 
  the 
  method 
  of 
  differences 
  in 
  order 
  to 
  obtain 
  

  

  