﻿680 
  Dr. 
  W. 
  F. 
  G. 
  Swann 
  on 
  a 
  Case 
  of 
  

  

  after 
  the 
  operation, 
  and 
  the 
  hole 
  was 
  sealed 
  up 
  with 
  wax 
  by 
  

   touching 
  it 
  with 
  a 
  hot 
  iron. 
  These 
  precautious 
  to 
  prevent 
  

   exposure 
  to 
  the 
  air 
  of 
  the 
  wire 
  fixed 
  to 
  the 
  plate 
  C 
  were 
  quite 
  

   necessary; 
  for 
  if 
  they 
  were 
  not 
  taken, 
  the 
  slight 
  discharge 
  

   which 
  took 
  place 
  from 
  the 
  end 
  of 
  the 
  rod 
  through 
  the 
  air 
  was 
  

   so 
  important 
  as 
  to 
  destroy 
  the 
  accuracy 
  of 
  the 
  measurements. 
  

  

  After 
  the 
  apparatus 
  had 
  been 
  charged 
  it 
  was 
  hung 
  up 
  in 
  

   the 
  earthed 
  tin 
  box 
  M, 
  and 
  the 
  plates 
  A, 
  B, 
  G, 
  H 
  were 
  con- 
  

   nected 
  to 
  separate 
  mercury 
  cups 
  in 
  a 
  paraffin 
  block. 
  The 
  

   holes 
  in 
  the 
  block 
  were 
  arranged 
  so 
  that 
  any 
  of 
  the 
  plates 
  

   could 
  be 
  earthed 
  or 
  connected 
  to 
  the 
  electrometer 
  at 
  will. 
  

  

  The 
  experiments 
  were 
  conducted 
  as 
  follows: 
  — 
  The 
  plates 
  

   A, 
  B, 
  G, 
  H 
  having 
  been 
  all 
  earthed, 
  they 
  were 
  then 
  all 
  

   insulated 
  except 
  A 
  which 
  was 
  connected 
  to 
  the 
  electrometer. 
  

   The 
  time 
  having 
  been 
  noted, 
  the 
  electrometer 
  quadrant 
  was 
  

   released 
  from 
  earth 
  by 
  pulling 
  a 
  string, 
  and 
  the 
  rate 
  of 
  

   movement 
  of 
  the 
  needle 
  was 
  noted, 
  observations 
  being 
  taken 
  

   at 
  intervals 
  of 
  a 
  period 
  of 
  the 
  needle 
  in 
  order 
  to 
  avoid 
  inertia 
  

   effects, 
  in 
  the 
  manner 
  described 
  in 
  a 
  former 
  paper 
  by 
  the 
  

   author 
  *. 
  A 
  series 
  of 
  readings 
  having 
  been 
  taken, 
  the 
  plates 
  

   and 
  the 
  guard-rings 
  were 
  all 
  earthed 
  again, 
  and 
  the 
  obser- 
  

   vations 
  were 
  repeated. 
  Similar 
  observations 
  were 
  then 
  taken 
  

   for 
  the 
  plate 
  B, 
  and 
  the 
  sensitiveness 
  of 
  the 
  electrometer 
  was 
  

   measured. 
  Observations 
  were 
  taken 
  in 
  this 
  manner 
  extending 
  

   over 
  a 
  day, 
  and 
  sometimes 
  over 
  two 
  days. 
  By 
  plotting 
  the 
  

   rate 
  of 
  movement 
  of 
  the 
  needle 
  against 
  the 
  time 
  (certain 
  

   corrections 
  being 
  applied 
  as 
  described 
  below), 
  a 
  curve 
  was 
  

   obtained 
  the 
  shape 
  of 
  which 
  depended 
  on 
  the 
  laws 
  governing 
  

   the 
  conduction 
  of 
  the 
  electricity 
  in 
  the 
  wax. 
  

  

  A 
  large 
  number 
  of 
  experiments 
  were 
  performed, 
  but 
  it 
  is 
  

   unnecessary 
  here 
  to 
  show 
  the 
  curves 
  for 
  each 
  experiment, 
  

   since 
  they 
  all 
  show 
  the 
  same 
  characteristics. 
  The 
  results 
  of 
  

   two 
  experiments 
  are 
  given 
  below, 
  one 
  in 
  which 
  the 
  internal 
  

   plate 
  was 
  charged 
  positively, 
  and 
  the 
  other 
  in 
  which 
  it 
  

   was 
  charged 
  negatively. 
  It 
  was 
  not 
  expected 
  nor 
  was 
  it 
  

   found, 
  that 
  the 
  shape 
  of 
  the 
  curve 
  depended 
  on 
  the 
  sign 
  of 
  

   the 
  charge 
  given 
  to 
  the 
  internal 
  plate, 
  for 
  on 
  no 
  theory 
  of 
  the 
  

   conduction 
  would 
  this 
  result. 
  

  

  The 
  sensitiveness 
  of 
  the 
  electrometer 
  could 
  be 
  varied 
  by 
  

   varying 
  the 
  potential 
  of 
  the 
  needle, 
  and 
  corrections 
  were 
  

   made 
  when 
  necessary 
  for 
  want 
  of 
  proportionality 
  between 
  

   the 
  deflexion 
  and 
  the 
  potential 
  of 
  the 
  quadrant, 
  and 
  for 
  

   slight 
  fluctuations 
  of 
  the 
  sensitiveness 
  of 
  the 
  instrument. 
  

   The 
  numbers 
  in 
  the 
  first 
  columns 
  of 
  the 
  tables 
  represent 
  the 
  

   deflexions 
  produced 
  in 
  56 
  seconds, 
  all 
  the 
  readings 
  being 
  

   * 
  Phil. 
  Mag-, 
  ser. 
  6, 
  vol. 
  xxiv. 
  p. 
  445, 
  Sept. 
  1912, 
  

  

  