﻿606 
  

  

  Electric 
  Waves 
  in 
  Short 
  Wire 
  Systems. 
  

  

  one 
  with 
  the 
  glass 
  disk 
  between 
  the 
  plates 
  and 
  one 
  with 
  air, 
  

   the 
  masses 
  being 
  adjusted 
  until 
  the 
  upsetting 
  of 
  the 
  balance 
  

   in 
  the 
  two 
  cases 
  occurs 
  for 
  the 
  same 
  reading 
  of 
  the 
  voltmeter. 
  

   The 
  whole 
  uncertainty 
  in 
  the 
  method 
  is 
  caused 
  by 
  fluctuations 
  

   in 
  the 
  value 
  of 
  the 
  potential. 
  Up 
  to 
  the 
  present, 
  with 
  a 
  

   difference 
  of 
  potential 
  between 
  the 
  plates 
  of 
  5000 
  volts, 
  it 
  has 
  

   not 
  been 
  found 
  possible 
  to 
  determine 
  the 
  mass, 
  whose 
  weight 
  

   counterbalances 
  the 
  electrostatic 
  pull, 
  to 
  less 
  than 
  one 
  milli- 
  

   gram. 
  The 
  masses 
  have, 
  however, 
  been 
  determined 
  with 
  cer- 
  

   tainty 
  to 
  this 
  amount. 
  The 
  mass 
  which 
  counterbalances 
  that 
  of 
  

   the 
  swinging 
  plate, 
  the 
  resting-point 
  being 
  the 
  middle 
  division 
  

   of 
  the 
  scale, 
  is 
  readily 
  determined 
  to 
  a 
  tenth 
  of 
  a 
  milligram. 
  

  

  The 
  mean 
  observations 
  are 
  given 
  in 
  Table 
  VI., 
  the 
  value 
  of 
  

   K 
  being 
  calculated 
  from 
  the 
  well-known 
  absolute 
  electrometer 
  

   formula. 
  The 
  thickness 
  of 
  the 
  glass 
  is 
  in 
  all 
  cases 
  1*837 
  cms. 
  

   Each 
  determination 
  involved 
  a 
  complete 
  relevelling 
  and 
  

   adjustment 
  of 
  the 
  apparatus 
  ; 
  it 
  is 
  merely 
  a 
  coincidence 
  that 
  

   the 
  distance 
  measures 
  gave 
  the 
  same 
  result 
  on 
  two 
  days. 
  

  

  Table 
  VI. 
  

  

  

  Dielectric 
  

  

  Pot. 
  

  

  Extra 
  mass 
  

  

  Mean 
  distance 
  

  

  

  Temp. 
  

  

  0. 
  

  

  1901. 
  

  

  between 
  

  

  Diff. 
  

  

  in 
  pan 
  when 
  

  

  between 
  

  

  K. 
  

  

  

  plates. 
  

  

  volts. 
  

  

  balance 
  upset. 
  

  

  plates. 
  

  

  

  Dec. 
  20th. 
  

  

  Glass. 
  

  

  5000 
  

  

  0-307 
  grtn. 
  

  

  3001 
  cms. 
  

  

  

  

  ,, 
  

  

  Air. 
  

  

  ,, 
  

  

  0067 
  

  

  ,, 
  

  

  7-73 
  

  

  26-6 
  

  

  Dec. 
  21st. 
  

  

  Glass. 
  

  

  5000 
  

  

  0-3081 
  

  

  2-999 
  

  

  

  

  )> 
  

  

  Air. 
  

  

  ,, 
  

  

  00669 
  

  

  ,, 
  

  

  7-81 
  

  

  25-2 
  

  

  Dec. 
  23rd. 
  

  

  Glass. 
  

  

  5000 
  

  

  030S 
  

  

  2-999 
  

  

  

  

  „ 
  

  

  Air. 
  

  

  ,, 
  

  

  0-067 
  

  

  ,, 
  

  

  7-75 
  

  

  25-0 
  

  

  

  Glass. 
  

  

  5000 
  

  

  0-308 
  

  

  2999 
  

  

  

  

  » 
  

  

  Air. 
  

  

  » 
  

  

  0-127 
  

  

  2-172 
  

  

  7-78 
  

  

  252 
  

  

  

  

  

  Mea 
  

  

  n 
  

  

  7-79 
  

  

  25-5 
  

  

  ! 
  

  

  

  During 
  this 
  investigation 
  we 
  have 
  received 
  much 
  help, 
  

   which 
  we 
  gratefully 
  acknowledge, 
  from 
  Professor 
  McAulay, 
  

   who 
  took 
  the 
  most 
  active 
  interest 
  in 
  our 
  work 
  while 
  Acting 
  

   Professor 
  of 
  Mathematics 
  at 
  Sydney, 
  and 
  from 
  Professor 
  

   Bragg. 
  We 
  are 
  indebted 
  to 
  Mr. 
  A. 
  Boyd 
  and 
  Mr. 
  P. 
  L. 
  

   Weston, 
  who 
  while 
  students 
  in 
  the 
  laboratory 
  took 
  the 
  

   preliminary 
  observations 
  in 
  the 
  earlier 
  part 
  of 
  the 
  work, 
  and 
  

   also 
  to 
  Mr. 
  H. 
  W. 
  Myers, 
  Mr. 
  T. 
  P. 
  Tivey, 
  and 
  Miss 
  F. 
  Martin 
  

   for 
  considerable 
  assistance. 
  To 
  Mr. 
  Cook, 
  the 
  laboratory 
  

   assistant, 
  our 
  best 
  thanks 
  are 
  given 
  for 
  the 
  great 
  care 
  with 
  

   which 
  the 
  apparatus 
  has 
  been 
  made. 
  

  

  