﻿Dielectrics 
  under 
  the 
  Action 
  of 
  Radium 
  Hays, 
  253 
  

  

  The 
  Ohm's 
  law 
  current 
  was 
  exceedingly 
  small 
  for 
  pure 
  

   substances, 
  and 
  it 
  was 
  subtracted 
  from 
  the 
  observed 
  effect 
  

   and 
  the 
  remaining 
  ionization 
  current 
  studied. 
  This 
  latter 
  

   shows 
  evidence 
  of 
  consisting 
  of 
  two 
  parts: 
  

  

  (1) 
  due 
  to 
  mobile 
  ions 
  similar 
  to 
  those 
  existing 
  in 
  an 
  

  

  ionized 
  gas 
  ; 
  

  

  (2) 
  due 
  to 
  slowly 
  moving 
  ions 
  which 
  appear 
  to 
  be 
  of 
  

  

  the 
  nature 
  of 
  electrolytic 
  ions. 
  

  

  (1) 
  is 
  saturated 
  by 
  a 
  field 
  of 
  1000 
  volts 
  per 
  cm. 
  

  

  (2) 
  shows 
  no 
  signs 
  of 
  saturation 
  in 
  fields 
  of 
  7000 
  volts 
  

  

  per 
  cm. 
  

   Jaffe 
  took 
  extraordinary 
  care 
  to 
  obtain 
  pure 
  dielectrics 
  ; 
  

   but 
  even 
  with 
  the 
  most 
  elaborate 
  precautions 
  it 
  appears 
  im- 
  

   possible 
  to 
  get 
  an 
  absolutely 
  pure 
  specimen. 
  In 
  the 
  work 
  

   described 
  below 
  substances 
  were 
  obtained 
  as 
  pure 
  as 
  possible, 
  

   and 
  only 
  experimented 
  with 
  if 
  the 
  ordinary 
  conduction 
  current 
  

   was 
  of 
  the 
  order 
  of 
  10~^^ 
  ampere 
  with 
  an 
  applied 
  field 
  of 
  

  

  about 
  100^^ 
  

  

  cm. 
  

  

  The 
  method 
  used 
  was 
  to 
  measure 
  first 
  the 
  current 
  through 
  

   the 
  dielectric 
  without 
  the 
  radium 
  near 
  and 
  then 
  with 
  the 
  

   radium, 
  the 
  difference 
  giving 
  the 
  ionization 
  current. 
  

  

  Apparatus. 
  

  

  One 
  of 
  the 
  many 
  difficulties 
  was 
  to 
  eliminate 
  all 
  possibility 
  

   of 
  leak 
  through 
  air 
  ionized 
  by 
  the 
  radium, 
  which 
  would 
  give 
  

   either 
  a 
  spurious 
  effect 
  or 
  cause 
  such 
  leak 
  as 
  to 
  mask 
  any 
  

   effect 
  which 
  might 
  exist. 
  After 
  many 
  trials 
  the 
  following 
  

   simple 
  form 
  of 
  apparatus 
  had 
  the 
  desired 
  effect. 
  

  

  The 
  substance 
  under 
  examination 
  was 
  placed 
  in 
  a 
  thick 
  

   lead 
  box 
  A 
  (fig. 
  1), 
  11 
  cm, 
  square 
  and 
  of 
  sides 
  2 
  cm. 
  thick. 
  

  

  Fig. 
  1. 
  

  

  Jr4* 
  

  

  

  Two 
  electrodes 
  B 
  and 
  C 
  were 
  supported 
  inside 
  by 
  means 
  of 
  

   ebonite 
  stems, 
  B 
  being 
  connected 
  during 
  an 
  experiment 
  to 
  

   one 
  terminal 
  of 
  a 
  set 
  of 
  storage-cells, 
  and 
  C 
  to 
  one 
  set 
  of 
  

   quadrants 
  of 
  a 
  Dolezalek 
  electrometer, 
  by 
  means 
  of 
  the 
  spring 
  

   JD 
  and 
  the 
  wire 
  E, 
  both 
  held 
  in 
  a 
  cylinder 
  of 
  ebonite 
  F. 
  

  

  