﻿300 
  Dr. 
  Russell 
  and 
  Mr. 
  Wright 
  : 
  The 
  Wright 
  Electrical 
  

  

  is 
  shown 
  in 
  fig. 
  7. 
  The 
  bridge-wire 
  is 
  the 
  same 
  as 
  in 
  fig. 
  6. 
  

   We 
  move 
  the 
  slides 
  AB, 
  AiBj, 
  AgBg, 
  and 
  A3B3 
  so 
  that 
  the 
  

  

  readings 
  1, 
  «2) 
  ^1? 
  ^.nd 
  a^ 
  on 
  their 
  logarithmic 
  scales 
  are 
  on 
  

   the 
  index-line 
  II'. 
  The 
  ends 
  o£ 
  the 
  contact-fingers 
  touching 
  

   AB, 
  A2B2, 
  and 
  A3B3 
  are 
  connected 
  with 
  P3 
  and 
  the 
  finger 
  

   touching 
  AjBi 
  with 
  Q3. 
  The 
  fingers 
  through 
  N, 
  Nj, 
  Ng, 
  and 
  

   N3 
  make 
  angles 
  tan~^0, 
  tan~^ 
  1, 
  tan~^ 
  2, 
  and 
  tan~^ 
  3 
  with 
  

   the 
  index-line. 
  The 
  battery 
  and 
  galvanometer-keys 
  being 
  

   closed, 
  the 
  bar 
  to 
  which 
  the 
  fingers 
  are 
  connected 
  is 
  gradually 
  

   lowered. 
  When 
  the 
  galvanometer 
  deflexion 
  is 
  zero 
  let 
  us 
  

   suppose 
  that 
  x 
  is 
  the 
  reading 
  on 
  the 
  logarithmic 
  scale 
  S. 
  

   In 
  this 
  case 
  we 
  have 
  

  

  E-V3 
  E-V3 
  E-Y3 
  E-V3 
  

  

  

  R 
  

  

  a2x'^ 
  

  

  R- 
  

  

  aix 
  

  

  