﻿Velocities 
  of 
  Delta 
  Rayi 
  

   5 
  3. 
  

  

  237 
  

  

  The 
  final 
  form 
  of 
  the 
  apparatus 
  is 
  shown 
  in 
  fig. 
  2. 
  The 
  

   source 
  of 
  S-rays 
  is 
  the 
  shallow, 
  open, 
  cylindrical 
  box. 
  B, 
  

   made 
  of 
  brass 
  ; 
  in 
  some 
  of 
  the 
  later 
  experiments, 
  in 
  which 
  a 
  

   magnetic 
  field 
  was 
  used, 
  the 
  box 
  was 
  surrounded 
  by 
  a 
  flat 
  

   ring 
  of 
  brass, 
  as 
  shown 
  in 
  the 
  figure, 
  giving 
  to 
  the 
  source 
  

  

  Fiar. 
  2. 
  

  

  TO 
  CCtCTROSCOPC 
  

  

  O 
  1 
  2 
  J 
  

  

  CtNTiMCTCRS 
  

  

  the 
  shape 
  of 
  a 
  sailor's 
  hat. 
  Below, 
  and 
  opposite 
  the 
  middle 
  

   of 
  this 
  box. 
  a 
  thin 
  brass 
  arm 
  supported 
  a 
  cylindrical 
  copper 
  

   plug, 
  P, 
  with 
  a 
  deposit 
  of 
  polonium 
  on 
  its 
  upper 
  surface, 
  

   which 
  was 
  4 
  mm. 
  in 
  diameter*. 
  The 
  end 
  of 
  this 
  plug 
  

   cted 
  into 
  the 
  box 
  so 
  that 
  none 
  of 
  the 
  a-rays 
  escaped, 
  but 
  

   fell 
  upon 
  the 
  top 
  and 
  sides 
  of 
  the 
  box 
  ; 
  the 
  open 
  character 
  of 
  

  

  * 
  I 
  am 
  again 
  indebted 
  to 
  Professor 
  Boltwood 
  for 
  the 
  polonium 
  used 
  in 
  

   these 
  experiments. 
  For 
  three 
  successive 
  years 
  be 
  has 
  most 
  kindly 
  supplied 
  

   me 
  with 
  the 
  annual 
  crop 
  of 
  polonium 
  grown 
  from 
  a 
  preparation 
  of 
  radio- 
  

   lead 
  in 
  his 
  possession. 
  

  

  