﻿r 
  594 
  Prof. 
  Pollock 
  and 
  Mr. 
  Vonwiller 
  : 
  Experiments 
  

  

  altered, 
  whenever 
  X 
  is 
  such 
  as 
  to 
  be 
  equal 
  to 
  2P/2& 
  + 
  1. 
  Of 
  

   these 
  maxima 
  that 
  one 
  will 
  be 
  the 
  greatest 
  corresponding 
  

   to 
  2& 
  + 
  l 
  = 
  ra, 
  or 
  any 
  odd 
  multiple 
  of 
  m. 
  

  

  When 
  the 
  bridge 
  is 
  moved 
  along 
  the 
  wires, 
  it 
  is 
  not 
  right 
  

   to 
  assume 
  that 
  maxima 
  deflexions 
  of 
  a 
  detector 
  in 
  the 
  

   secondary 
  circuit 
  occur 
  when 
  the 
  wire 
  system 
  is 
  divided 
  

   exactly 
  in 
  the 
  ratio 
  of 
  small 
  odd 
  numbers. 
  For 
  suppose 
  the 
  

   bridge 
  in 
  such 
  a 
  position 
  that 
  it 
  exactly 
  divides 
  the 
  system 
  in 
  

   such 
  a 
  ratio, 
  and 
  consider 
  that 
  the 
  length 
  of 
  the 
  primary 
  

   circuit 
  is 
  such 
  that 
  a 
  certain 
  mode 
  of 
  its 
  vibration 
  has 
  a 
  free 
  

   period 
  very 
  near 
  to 
  that 
  of 
  the 
  oscillation 
  of 
  the 
  condenser 
  

   circuit. 
  A 
  small 
  movement 
  of 
  the 
  bridge 
  certainly 
  makes 
  

   the 
  resonance 
  less 
  perfect 
  between 
  the 
  primary 
  and 
  secondary 
  

   -circuits, 
  but 
  may 
  increase 
  the 
  amplitude 
  of 
  the 
  vibration 
  in 
  

   the 
  primary 
  circuit. 
  The 
  amplitude 
  of 
  the 
  vibration 
  in 
  the 
  

   secondary 
  circuit 
  may, 
  on 
  the 
  whole, 
  become 
  greater. 
  This 
  

   effect 
  would 
  be 
  more 
  marked 
  in 
  those 
  cases 
  where 
  the 
  length 
  

   of 
  the 
  primary 
  is 
  small 
  compared 
  with 
  that 
  of 
  the 
  secondary 
  

   circuit. 
  

  

  If 
  the 
  detector 
  is 
  placed 
  in 
  the 
  primary 
  instead 
  of 
  in 
  the 
  

   secondary 
  circuit, 
  a 
  similar 
  curve 
  to 
  the 
  first 
  part 
  of 
  the 
  one 
  

   shown 
  in 
  fig. 
  3 
  gives 
  the 
  relation 
  between 
  deflexion 
  and 
  dis- 
  

   tance 
  apart 
  of 
  condenser-plates 
  as 
  the 
  period 
  of 
  the 
  condenser 
  

   oscillation 
  decreases 
  from 
  a 
  value 
  greater 
  to 
  a 
  value 
  less 
  than 
  

   that 
  of 
  some 
  mode 
  of 
  vibration 
  of 
  the 
  primary 
  circuit. 
  

  

  Experiments 
  have 
  been 
  made 
  with 
  the 
  following 
  lengths 
  

   of 
  wires:— 
  8-98, 
  9;47, 
  10*05, 
  10-50, 
  12-00, 
  18-85 
  metres. 
  

   Observations 
  have 
  in 
  general 
  only 
  been 
  taken 
  for 
  successive 
  

   positions 
  of 
  the 
  bridge 
  differing 
  by 
  0*5 
  metre, 
  so 
  no 
  doubt 
  

   some 
  fine 
  detail 
  is 
  not 
  included. 
  At 
  the 
  time 
  the 
  experiments 
  

   were 
  made, 
  the 
  object 
  was 
  merely 
  to 
  locate 
  the 
  position 
  of 
  

   the 
  bridge 
  giving 
  the 
  principal 
  maxima. 
  

  

  Fig. 
  4. 
  

   12 
  

  

  9M£Tfi£S 
  

  

  Fig. 
  4 
  gives 
  the 
  plot 
  of 
  the 
  results 
  obtained 
  with 
  wires 
  

   8'98 
  '-'metres 
  long, 
  the 
  ordinates 
  being 
  deflexions 
  in 
  cms., 
  and 
  

   the 
  abscissae 
  lengths 
  measured 
  along 
  the 
  wires 
  from 
  their 
  

   free 
  ends 
  to 
  the 
  bridge. 
  

  

  