﻿910 
  Dr. 
  J. 
  P. 
  V. 
  Madsen 
  on 
  the 
  

  

  wood, 
  portions 
  oi 
  the 
  block 
  being 
  removed 
  as 
  shown 
  to 
  allow 
  

   o£ 
  the 
  introduction 
  o£ 
  the 
  screens 
  in 
  different 
  positions 
  as 
  at 
  

   A, 
  B, 
  C. 
  The 
  ionization-chamber 
  was 
  hemispherical 
  and 
  

   made 
  of 
  wood, 
  with 
  the 
  inner 
  surface 
  covered 
  with 
  verj' 
  thin 
  

  

  JbE^rlh. 
  

   '•-—^ToBled'fom&tcr. 
  

  

  Jb 
  Batten^. 
  

  

  Al 
  foil. 
  The 
  electrode 
  connecting 
  to 
  the 
  electrometer 
  was 
  

   in 
  the 
  form 
  of 
  a 
  circular 
  ring 
  of 
  wire, 
  suitably 
  protected 
  by 
  

   the 
  usual 
  methods. 
  The 
  hemispherical 
  chamber 
  rested 
  upon 
  

   a 
  circular 
  plate 
  of 
  Pb, 
  above 
  which 
  was 
  laid 
  a 
  sheet 
  of 
  Al. 
  

   A 
  circular 
  hole 
  cut 
  centrally 
  in 
  the 
  Pb 
  and 
  Al 
  plates 
  enabled 
  

   the 
  screen 
  to 
  be 
  placed 
  in 
  the 
  position 
  A. 
  In 
  this 
  position 
  

   practically 
  all 
  the 
  emergent 
  scattered 
  radiation 
  was 
  able 
  to 
  

   produce 
  its 
  effect 
  to 
  the 
  same 
  extent 
  as 
  the 
  rays 
  in 
  the 
  main 
  

   stream, 
  all 
  rays 
  having 
  the 
  same 
  length 
  of 
  path 
  in 
  which 
  to 
  

   produce 
  ionization, 
  and 
  the 
  complications 
  of 
  secondary 
  effects 
  

   being 
  reduced 
  by 
  having 
  the 
  walls 
  of 
  the 
  chamber 
  wood. 
  

  

  If 
  we 
  may 
  for 
  the 
  present 
  neglect 
  any 
  alteration 
  in 
  speed 
  

   of 
  the 
  scattered 
  radiation 
  and 
  consider 
  the 
  original 
  stream 
  

   of 
  rays 
  more 
  or 
  less 
  homogeneous, 
  the 
  current 
  may 
  be 
  taken 
  

   approximately 
  as 
  a 
  measure 
  of 
  the 
  number 
  of 
  /3 
  particles 
  

   \N 
  hich 
  enter 
  the 
  chamber, 
  no 
  matter 
  what 
  their 
  direction, 
  

   proper 
  correction 
  being 
  made 
  for 
  the 
  effect 
  produced 
  by 
  y 
  

  

  By 
  subtracting 
  the 
  readings 
  taken 
  with 
  a 
  screen 
  at 
  A 
  and 
  

   at 
  C 
  a 
  measure 
  is 
  obtained 
  of 
  the 
  amount 
  of 
  radiation 
  which 
  

   has 
  been 
  turned 
  out 
  of 
  its 
  original 
  path 
  or 
  scattered 
  by 
  that 
  

   screen. 
  Another 
  reading 
  with 
  the 
  screen 
  at 
  B 
  enabled 
  the 
  

   distribution 
  of 
  the 
  emergent 
  scattered 
  radiation 
  to 
  be 
  followed 
  

   out. 
  

  

  