﻿Dielectrics 
  under 
  the 
  Action 
  of 
  Radium 
  Rays. 
  255 
  

  

  of 
  the 
  electrometer 
  enabled 
  the 
  current 
  to 
  be 
  found. 
  "When 
  

   no 
  E.M.F. 
  was 
  applied 
  no 
  current 
  could 
  be 
  detected, 
  so 
  that 
  

   the 
  radium 
  rays 
  themselves 
  did 
  not 
  charge 
  up 
  the 
  system 
  

   appreciably. 
  

  

  In 
  all 
  cases 
  given 
  the 
  results 
  were 
  got 
  by 
  applying 
  a 
  

   -f 
  E.M.F. 
  , 
  as 
  Jaffe 
  showed 
  that 
  the 
  ionization 
  current 
  was 
  

   the 
  same 
  on 
  applying 
  either 
  a 
  + 
  or 
  — 
  E.M.F. 
  

  

  The 
  following 
  substances 
  were 
  experimented 
  with: 
  — 
  heavy 
  

   paraffin 
  oil 
  (density 
  '89), 
  solid 
  paraffin, 
  vaseline, 
  glass, 
  and 
  

   ebonite. 
  The 
  oil 
  and 
  vaseline 
  were 
  poured 
  into 
  the 
  lead 
  box, 
  

   and 
  in 
  the 
  case 
  of 
  the 
  latter 
  it 
  was 
  allowed 
  to 
  solidify. 
  For 
  

   the 
  solid 
  paraffin 
  an 
  additional 
  piece 
  of 
  apparatus 
  was 
  used 
  

   (fig. 
  3). 
  Molten 
  paraffin 
  was 
  poured 
  round 
  the 
  electrodes 
  

  

  Fi-. 
  3. 
  

  

  C, 
  B, 
  held 
  in 
  a 
  tin 
  vessel 
  T. 
  C 
  was 
  supported 
  by 
  a 
  stem 
  D 
  

   passing 
  through 
  a 
  hole 
  in 
  the 
  vessel, 
  and 
  insulated 
  from 
  it 
  by 
  

   a 
  layer 
  of 
  sealing-wax 
  S. 
  

  

  This 
  vessel 
  was 
  placed 
  in 
  the 
  lead 
  box 
  A, 
  the 
  stem 
  D 
  

   touching 
  the 
  spring 
  E, 
  and 
  so 
  making 
  contact 
  with 
  the 
  

   electrometer. 
  Oil 
  was 
  poured 
  into 
  the 
  lead 
  box 
  to 
  exclude 
  

   air. 
  

  

  In 
  the 
  case 
  of 
  glass 
  and 
  ebonite 
  thin 
  sheets 
  were 
  used. 
  

   On 
  opposite 
  sides 
  of 
  these 
  were 
  pasted 
  pieces 
  of 
  tinfoil 
  A, 
  

   B 
  making 
  a 
  sort 
  of 
  condenser. 
  To 
  prevent 
  surface 
  leak 
  a 
  

   guard-ring 
  of 
  tinfoil 
  CD 
  was 
  pasted 
  round 
  the 
  edges 
  and 
  

   earthed 
  during 
  an 
  experiment 
  (fig. 
  4, 
  p. 
  256). 
  

  

  In 
  performing 
  an 
  experiment 
  it 
  was 
  necessary 
  to 
  allow 
  

   the 
  conduction 
  current 
  to 
  pass 
  for 
  some 
  time. 
  The 
  current 
  

   at 
  first 
  was 
  large 
  and 
  gradually 
  reached 
  a 
  minimum 
  value. 
  

   At 
  this 
  stage 
  the 
  radium 
  was 
  put 
  in 
  position 
  and 
  allowed 
  to 
  

   ionize 
  the 
  dielectric 
  and 
  the 
  current 
  again 
  measured. 
  The 
  

  

  