﻿H. 
  A. 
  Bumstead 
  — 
  Velocities 
  of 
  Delta 
  Rays. 
  

  

  95 
  

  

  sides 
  of 
  the 
  box 
  ; 
  the 
  open 
  character 
  of 
  the 
  latter 
  and 
  the 
  

   smallness 
  of 
  the 
  obstacle 
  presented 
  by 
  the 
  polonium 
  and 
  its 
  

   support 
  enabled 
  a 
  large 
  proportion 
  of 
  the 
  S-rays 
  and 
  tertiary 
  

   rays 
  to 
  get 
  away. 
  This 
  source 
  was 
  enclosed 
  in 
  a 
  large, 
  cylin- 
  

   drical 
  brass 
  case 
  which 
  could 
  be 
  highly 
  exhausted 
  by 
  the 
  help 
  

   of 
  charcoal 
  and 
  liquid 
  air 
  ; 
  the 
  charcoal 
  bulb 
  was 
  placed 
  be- 
  

   tween 
  the 
  evacuated 
  chamber 
  and 
  the 
  pump 
  and 
  gauge, 
  and 
  

  

  Fig. 
  2. 
  

  

  ^\mmmmm^w 
  

  

  k" 
  9 
  i. 
  

  

  was 
  so 
  constructed 
  as 
  to 
  free 
  the 
  chamber 
  of 
  mercury 
  vapor 
  by 
  

   its 
  distillation 
  into 
  the 
  cold 
  bulb. 
  Within 
  the 
  case 
  and 
  -J 
  cm 
  

   from 
  its 
  walls 
  was 
  a 
  cylindrical 
  cage 
  of 
  bronze 
  wire-gauze 
  

   which 
  was 
  insulated 
  from 
  the 
  case 
  and 
  could 
  be 
  separately 
  

   charged 
  by 
  means 
  of 
  an 
  external 
  electrode. 
  It 
  was 
  found 
  to 
  

   be 
  important 
  that 
  the 
  insulators 
  supporting 
  the 
  cage 
  should 
  

   not 
  be 
  struck 
  by 
  the 
  S-rays; 
  if 
  they 
  were, 
  they 
  acquired 
  

   charges 
  which 
  gave 
  rise 
  to 
  erratic 
  results. 
  Accordingly 
  the 
  

   cage 
  was 
  supported 
  by 
  three 
  small 
  pieces- 
  of 
  ebonite 
  near 
  the 
  

  

  