﻿174 
  

  

  Mr. 
  W. 
  Duddell 
  on 
  a 
  

  

  With 
  each 
  adjustment 
  of 
  the 
  instrument 
  in 
  fig. 
  7 
  to 
  suit 
  

   the 
  various 
  frequencies, 
  the 
  sensibility 
  of 
  the 
  instrument 
  was 
  

  

  Fio-, 
  

  

  TO 
  

  

  60 
  

  

  50 
  

  

  40 
  

  

  5 
  

  

  p. 
  

  

  z 
  

  

  < 
  

   L 
  30 
  

  

  r 
  2.0 
  

  

  

  fO 
  

  

  I 
  

  

  

  

  

  

  

  

  

  \ 
  

  

  

  : 
  

  

  a 
  -•J 
  

  

  - 
  l6cM.u 
  

  

  - 
  13 
  .. 
  

   10 
  » 
  

  

  NQTM 
  

  

  o 
  

  

  - 
  6 
  " 
  

  

  

  \ 
  

  

  

  

  

  

  

  

  \ 
  

  

  

  

  

  

  

  

  ^^ 
  

  

  

  

  

  

  

  

  

  ^^ 
  

  

  

  

  "^^n^ 
  

  

  

  

  

  

  

  ■-~o-> 
  

  

  

  0— 
  

  

  100 
  200 
  300 
  400 
  500 
  

  

  FkEQOENCY 
  : 
  'V 
  ■P-E'R 
  SECOND 
  

   A 
  LTEKNATING 
  CuWKENT 
  

  

  600 
  

  

  700 
  

  

  tested 
  with 
  direct 
  current 
  as 
  an 
  ordinary 
  galvanometer 
  

   (fig. 
  8). 
  

  

  It 
  will 
  be 
  noted 
  that 
  the 
  sensibility 
  to 
  alternating 
  current 
  

   decreases 
  very 
  nearly 
  inversely 
  as 
  the 
  frequency 
  for 
  which 
  

   the 
  instrument 
  is 
  adjusted, 
  whereas 
  for 
  direct 
  current 
  the 
  

   sensibility 
  decreases 
  approximately 
  inversely 
  as 
  the 
  square 
  of 
  

   the 
  frequency 
  for 
  which 
  the 
  instrument 
  is 
  adjusted, 
  which 
  is 
  

   what 
  usually 
  takes 
  place 
  with 
  direct 
  current 
  galvanometers. 
  

   By 
  dividing 
  corresponding 
  ordinates 
  in 
  figs. 
  7 
  and 
  8 
  a 
  new 
  

   curve 
  is 
  obtained 
  (fig. 
  9), 
  which 
  1 
  have 
  called 
  the 
  magnification, 
  

   which 
  shows 
  for 
  a 
  given 
  adjustment 
  of 
  the 
  instrument, 
  how 
  

   much 
  more 
  sensitive 
  it 
  is 
  to 
  an 
  alternating 
  current 
  of 
  the 
  

   proper 
  frequency 
  than 
  to 
  a 
  direct 
  current. 
  The 
  highest 
  value 
  

   obtained 
  in 
  the 
  curves 
  is 
  about 
  460. 
  Had 
  the 
  vibration 
  

  

  