﻿590 
  Prof. 
  Pollock 
  and 
  Mr. 
  Vonwiller 
  : 
  Experiments 
  

  

  Experiments 
  without 
  a 
  Bridge 
  across 
  the 
  Wires. 
  

  

  In 
  experiments 
  with 
  waves 
  along 
  short 
  wires 
  where 
  no 
  

   bridge 
  is 
  used, 
  the 
  system 
  of 
  longitudinal 
  currents 
  is 
  deter- 
  

   mined 
  by 
  the 
  condition 
  that 
  the 
  currents 
  must 
  vanish 
  at 
  the 
  

   ends 
  of 
  the 
  wires. 
  All 
  modes 
  of 
  vibration 
  having 
  an 
  integer 
  

   number 
  of 
  nodes 
  along 
  the 
  wires 
  are 
  therefore 
  possible. 
  In 
  

   these 
  experiments 
  various 
  lengths 
  of 
  wires 
  have 
  been 
  used, 
  

   the 
  position 
  of 
  the 
  nodes 
  being 
  determined 
  to 
  within 
  5 
  cms. 
  

   With 
  more 
  observations, 
  the 
  position 
  could 
  have 
  been 
  found 
  

   to 
  within 
  1 
  cm., 
  but 
  this 
  accuracy 
  was 
  considered 
  unnecessary. 
  

   Successive 
  values 
  of 
  the 
  internode 
  in 
  any 
  one 
  experiment 
  

   usually 
  agree 
  to 
  within 
  2 
  per 
  cent, 
  of 
  the 
  mean 
  value. 
  Fig. 
  2 
  

   is 
  the 
  plot 
  of 
  the 
  observations 
  with 
  wires 
  17*5 
  inches 
  long, 
  

  

  Fig. 
  2. 
  

  

  METRES 
  

  

  the 
  ordinates 
  being 
  deflexions 
  in 
  centimetres, 
  and 
  the 
  abscissae 
  

   distances 
  of 
  the 
  slider 
  along 
  the 
  wires 
  in 
  metres, 
  measured 
  

   from 
  their 
  free 
  ends. 
  

  

  The 
  results 
  of 
  the 
  experiments 
  are 
  given 
  in 
  Table 
  I. 
  In 
  

   calculating 
  the 
  distance 
  between 
  the 
  nodes 
  for 
  various 
  modes 
  

   of 
  vibration, 
  1*6 
  m. 
  has 
  been 
  added 
  to 
  the 
  length 
  of 
  the 
  

   wires, 
  an 
  amount 
  which 
  will 
  be 
  justified 
  later. 
  

  

  In 
  such 
  experiments, 
  when 
  the 
  vibrations 
  of 
  the 
  electrical 
  

   condition 
  of 
  the 
  wire 
  system 
  are 
  forced, 
  it 
  may 
  be 
  said 
  

   generally 
  that 
  that 
  mode 
  of 
  vibration 
  occurs 
  whose 
  free 
  period 
  

   is 
  near 
  to 
  that 
  of 
  the 
  condenser 
  oscillation. 
  The 
  distance 
  

   between 
  the 
  nodes 
  on 
  the 
  wires 
  depends 
  on 
  the 
  length 
  of 
  the 
  

   wires, 
  and 
  does 
  not 
  alter 
  continuously 
  with 
  change 
  in 
  the 
  con- 
  

   denser 
  capacity. 
  It 
  is 
  therefore 
  impossible 
  to 
  determine 
  the 
  

   ratio 
  of 
  the 
  condenser 
  capacities 
  in 
  two 
  such 
  experiments 
  

  

  