﻿868 
  Messrs. 
  Fuller 
  and 
  Grace: 
  Effect 
  of 
  Temperature 
  

  

  90° 
  by 
  using 
  a 
  variable 
  choking-coil 
  in 
  the 
  primary 
  of 
  one 
  

   o£ 
  the 
  transformers 
  supplying 
  current. 
  

  

  The 
  numerous 
  adjustments 
  which 
  have 
  to 
  bo 
  made 
  are 
  a 
  

   disadvantage 
  of 
  the 
  alternating 
  current 
  method 
  compared 
  

   with 
  the 
  rotating 
  magnet 
  method 
  used 
  by 
  Baily 
  and 
  others 
  ; 
  

   but 
  the 
  absence 
  of 
  rotating 
  parts 
  is 
  a 
  distinct 
  advantage, 
  

   and 
  this 
  fact 
  would 
  render 
  the 
  method 
  very 
  suitable 
  for 
  high- 
  

   frequency 
  experiments. 
  

  

  To 
  measure 
  the 
  flux 
  in 
  the 
  iron, 
  a 
  coil 
  of 
  8 
  turns 
  of 
  bare 
  

   wire 
  was 
  wound 
  round 
  it 
  and 
  insulated 
  therefrom 
  with 
  mica. 
  

   As 
  the 
  E.M.F. 
  induced 
  in 
  the 
  coil 
  is 
  alternating 
  and 
  of 
  the 
  

   order 
  of 
  '04 
  volt, 
  a 
  suitable 
  galvanometer 
  had 
  to 
  be 
  con- 
  

   structed 
  in 
  order 
  to 
  measure 
  it. 
  The 
  instrument 
  constructed 
  

   for 
  the 
  purpose 
  is 
  shown 
  in 
  fig. 
  2. 
  A 
  B 
  C 
  D 
  are 
  four 
  

  

  

  Fig. 
  2. 
  

  

  

  

  (k 
  ■ 
  

  

  — 
  9c/n 
  

  

  j» 
  

  

  \\ 
  

  

  ° 
  / 
  

  

  /^ 
  

  

  ^^ 
  

  

  V 
  a.i-^/ 
  

  

  ^i: 
  

  

  ^ 
  

  

  

  

  

  ..'' 
  

  

  

  

  A 
  

  

  H^"' 
  

  

  \ 
  

  

  B 
  

  

  ^ 
  

  

  / 
  ~ 
  \v^ 
  

  

  ^ 
  

  

  coils 
  of 
  conical 
  shape 
  and 
  wound 
  with 
  no. 
  2^ 
  wire. 
  A 
  and 
  B 
  

   were 
  connected 
  in 
  series 
  through 
  a 
  resistance 
  to 
  one 
  phase, 
  

   C 
  and 
  D 
  to 
  the 
  other 
  phase, 
  of 
  the 
  machine 
  supplying 
  current 
  

   to 
  the 
  magneti?ing-coils 
  of 
  the 
  test 
  apparatus 
  JD 
  E, 
  With 
  a 
  

  

  