﻿SU^ 
  _ 
  1 
  Bg 
  

  

  8t 
  

  

  686 
  Dr. 
  W. 
  F. 
  G. 
  Swann 
  on 
  a 
  Case 
  of 
  

  

  The 
  rise 
  of 
  potential 
  of 
  the 
  electrometer 
  in 
  the 
  time 
  St 
  is 
  

   $<]/C 
  e 
  , 
  where 
  C 
  e 
  is 
  its 
  capacity. 
  Thus 
  

  

  Hence 
  

  

  Similarly 
  we 
  have 
  for 
  the 
  plate 
  B, 
  

  

  - 
  s 
  %-, 
  l 
  ?{«/ 
  ©-*©}• 
  ■ 
  « 
  

  

  a 
  and 
  C$ 
  are 
  practically 
  the 
  same, 
  so 
  that 
  we 
  should 
  have 
  

  

  C 
  a 
  and 
  C5 
  would 
  be 
  exactly 
  the 
  same 
  except 
  for 
  the 
  edge 
  

  

  effects, 
  which 
  are 
  nearly 
  eliminated 
  by 
  the 
  guard-ring 
  

  

  arrangement, 
  for 
  the 
  effect 
  of 
  an 
  insulated 
  plate 
  on 
  the 
  

  

  capacity 
  of 
  another 
  plate 
  parallel 
  to 
  it 
  should 
  be 
  independent 
  

  

  of 
  the 
  distance 
  between 
  the 
  plates, 
  and 
  should 
  depend 
  only 
  

  

  on 
  the 
  thickness 
  of 
  the 
  plates. 
  The 
  edge 
  effects 
  do 
  play 
  a 
  

  

  slight 
  part, 
  however, 
  for 
  in 
  any 
  inductive 
  action 
  between 
  

  

  C 
  and 
  A 
  or 
  B, 
  the 
  edge 
  of 
  the 
  plate 
  C 
  takes 
  so 
  much 
  more 
  

  

  of 
  its 
  share 
  of 
  the 
  displaced 
  charge, 
  so 
  to 
  speak, 
  as 
  to 
  cause 
  

  

  the 
  effect 
  to 
  be 
  the 
  same 
  as 
  if 
  were 
  connected 
  to 
  an 
  

  

  external 
  body 
  of 
  appreciable 
  capacity. 
  The 
  net 
  result 
  is 
  that 
  

  

  C 
  has 
  a 
  greater 
  effect 
  on 
  the 
  capacity 
  of 
  A 
  which 
  is 
  near 
  to 
  

  

  it, 
  than 
  on 
  B 
  which 
  is 
  far 
  away. 
  The 
  difference 
  between 
  

  

  C 
  

   C 
  a 
  and 
  C 
  b 
  is, 
  however, 
  very 
  slight. 
  The 
  quantities 
  ,-, 
  " 
  r 
  

  

  and 
  -^ 
  — 
  b 
  -j^ 
  were 
  measured 
  *, 
  and 
  were 
  found 
  to 
  be 
  in 
  the 
  

  

  * 
  One 
  pole 
  of 
  a 
  battery 
  of 
  two 
  cadmium 
  cells 
  was 
  connected 
  to 
  a 
  

   quadrant 
  of 
  the 
  electrometer 
  through 
  a 
  very 
  high 
  resistance, 
  the 
  other 
  

   pole 
  being 
  earthed, 
  and 
  observations 
  of 
  the 
  movement 
  of 
  the 
  needle 
  

   were 
  made, 
  The 
  experiment 
  was 
  then 
  repeated 
  with 
  one 
  of 
  the 
  

   capacities, 
  C 
  a 
  for 
  example, 
  connected 
  to 
  the 
  quadrant. 
  The 
  ratio 
  of 
  

   the 
  times 
  taken 
  by 
  the 
  electrometer-needle 
  to 
  move 
  over 
  the 
  same 
  range, 
  

  

  C 
  1 
  P 
  I 
  C 
  1 
  

  

  gave 
  the 
  ratio 
  -^ 
  — 
  e 
  — 
  -, 
  and 
  from 
  this 
  — 
  ^ 
  — 
  - 
  could 
  be 
  calculated. 
  

  

  This 
  method 
  of 
  determining 
  the 
  ratio 
  was 
  found 
  far 
  more 
  satisfactory 
  

   than 
  any 
  other, 
  such, 
  for 
  example, 
  as 
  the 
  method 
  of 
  mixtures, 
  since 
  in 
  it 
  

   no 
  errors 
  can 
  arise 
  due 
  to 
  electrostatic 
  effects 
  arising 
  at 
  the 
  instant 
  of 
  

   making 
  contact 
  between 
  the 
  two 
  capacities 
  concerned. 
  

  

  