﻿244 
  

  

  Dr. 
  J. 
  C. 
  Beattie 
  on 
  the 
  Electric 
  Resistance 
  

  

  to 
  these 
  ; 
  the 
  current 
  — 
  which 
  we 
  shall 
  call 
  the 
  primary 
  1 
  — 
  ■ 
  

   could 
  be 
  regulated 
  by 
  the 
  insertion 
  of 
  resistances 
  in 
  the 
  

   primary 
  circuit, 
  Two 
  secondary 
  electrodes 
  were 
  soldered 
  on 
  

   to 
  two 
  approximately 
  equipotential 
  points 
  lying 
  on 
  opposite 
  

   sides 
  of 
  the 
  film 
  ; 
  these 
  were 
  joined 
  to 
  the 
  galvanometer. 
  

  

  a, 
  a'. 
  Primary 
  electrodes. 
  

  

  b, 
  b'. 
  Secondary 
  electrodes. 
  

  

  In 
  those 
  films 
  where 
  the 
  secondary 
  electrodes 
  were 
  not 
  on 
  

   the 
  same 
  equipotential 
  line 
  when 
  there 
  was 
  no 
  magnetic 
  field, 
  

   the 
  electrodes 
  could 
  be 
  brought 
  to 
  the 
  same 
  potential 
  by 
  

  

  Rheo 
  

  

  STAT 
  

  

  Battery 
  

  

  bjh 
  

  

  Resistance 
  

  

  /) 
  Galv 
  

  

  BOX 
  

  

  o 
  o 
  o 
  o 
  

  

  O 
  O 
  O 
  O 
  

  

  Resistance 
  

  

  BOX 
  

  

  Resistance 
  

   Box 
  

  

  inserting 
  a 
  suitable 
  resistance 
  between 
  one 
  of 
  the 
  secondary 
  

   electrodes 
  and 
  the 
  properly 
  chosen 
  primary 
  electrode. 
  

  

  To 
  measure 
  the 
  variation 
  of 
  resistance 
  the 
  arrangement 
  

   shown 
  in 
  the 
  diagram 
  was 
  used. 
  

  

  