﻿40 
  Rowland 
  and 
  Penniman 
  — 
  Electrical 
  Measurements, 
  

  

  That 
  is, 
  the 
  results 
  agreed 
  to 
  within 
  about 
  1 
  per 
  cent. 
  In 
  the 
  

   determination 
  of 
  L 
  the 
  resistance 
  in 
  circuit 
  K 
  was 
  varied 
  from 
  

   the 
  least 
  possible 
  resistance 
  as 
  determined 
  by 
  the 
  coils 
  up 
  to 
  

   1000 
  ohms 
  and 
  more, 
  and 
  the 
  self-inductance 
  was 
  determined 
  

   under 
  these 
  various 
  conditions. 
  These 
  results 
  agreed 
  among 
  

   themselves, 
  and 
  were 
  apparently 
  independent 
  of 
  the 
  resistance 
  

   in 
  circuit 
  with 
  it. 
  In 
  the 
  application 
  of 
  this 
  method 
  to 
  the 
  

   determination 
  of 
  capacity, 
  however, 
  great 
  trouble 
  was 
  encoun- 
  

   tered, 
  as 
  the 
  capacity 
  apparently 
  varied 
  both 
  with 
  the 
  resist- 
  

   ance 
  in 
  circuit 
  with 
  it 
  and 
  with 
  the 
  period. 
  This 
  variation 
  

   was 
  regular 
  for 
  each 
  period, 
  the 
  value 
  derived 
  depending 
  on 
  

   the 
  resistance 
  in 
  circuit. 
  This 
  irregularity 
  of 
  derived 
  value 
  of 
  

   the 
  capacity 
  led 
  to 
  the 
  investigation 
  and 
  development 
  of 
  Max- 
  

   well's 
  formula 
  on 
  the 
  effect 
  of 
  absorption, 
  a 
  necessary 
  charac- 
  

   teristic 
  of 
  heterogeneous 
  substances. 
  

  

  When 
  the 
  formula 
  was 
  deduced, 
  as 
  may 
  be 
  seen 
  in 
  the 
  

   article 
  already 
  referred 
  to, 
  the 
  absorption 
  comes 
  in 
  as 
  an 
  added 
  

   resistance, 
  the 
  resistance 
  being 
  constant 
  for 
  a 
  given 
  period. 
  

   By 
  an 
  inspection 
  of 
  the 
  results 
  this 
  was 
  found 
  to 
  be 
  the 
  case. 
  

   The 
  finding 
  of 
  the 
  resistance 
  due 
  to 
  absorption 
  in 
  this 
  method 
  

   is 
  one 
  of 
  approximation, 
  but 
  the 
  values 
  deduced 
  compare 
  very 
  

   favorably 
  with 
  those 
  determined 
  by 
  direct 
  measurement, 
  as 
  will 
  

   be 
  seen 
  later 
  when 
  various 
  results 
  are 
  collected. 
  In 
  the 
  actual 
  

   experiments 
  the 
  condensers 
  used 
  were 
  two 
  paraffined 
  paper 
  

   condensers 
  of 
  about 
  2 
  and 
  3 
  microfarads. 
  The 
  currents 
  used 
  

   had 
  different 
  periods, 
  as 
  seen 
  in 
  the 
  table 
  following, 
  where 
  

   n^ 
  133, 
  53-3, 
  31-9 
  and 
  14. 
  

  

  The 
  process 
  was 
  to 
  place 
  in 
  the 
  condenser 
  circuit 
  a 
  resistance 
  

   R, 
  and 
  then 
  to 
  move 
  the 
  key 
  K 
  back 
  and 
  forth 
  until 
  VJ 
  was 
  

   found 
  that 
  gave 
  the 
  same 
  deflection. 
  D, 
  fig. 
  2, 
  was 
  now 
  

   reversed 
  and 
  the 
  process 
  repeated. 
  This 
  was 
  repeated 
  with 
  

   different 
  values 
  of 
  R 
  and 
  n 
  and 
  the 
  apparent 
  capacity. 
  Thi& 
  

   gave 
  great 
  variation 
  of 
  apparent 
  capacity 
  wdth 
  different 
  values 
  

   of 
  R, 
  which 
  should 
  not 
  be 
  the 
  case, 
  and, 
  therefore, 
  gave 
  a 
  means 
  

   of 
  finding 
  the 
  resistance 
  due 
  to 
  absorption 
  or 
  absorption 
  resist- 
  

   ance, 
  as 
  we 
  will 
  designate, 
  by 
  approximation. 
  As 
  the 
  effect 
  of 
  

   absorption 
  is 
  a 
  resistance 
  it 
  is 
  possible 
  to 
  find 
  what 
  resistance, 
  if 
  

   added 
  to 
  R, 
  will 
  make 
  all 
  the 
  values 
  of 
  the 
  capacity 
  as 
  deter- 
  

   mined 
  for 
  the 
  different 
  values 
  of 
  R 
  the 
  same. 
  Therefore 
  it 
  

   should 
  be 
  the 
  same 
  for 
  any 
  two 
  values 
  of 
  R. 
  Calling 
  the 
  two 
  

   values 
  of 
  R 
  in 
  the 
  two 
  cases 
  R^ 
  and 
  R^ 
  respectively 
  and 
  the 
  

   two 
  corresponding 
  values 
  of 
  R^, 
  R/, 
  and 
  R/, 
  and 
  let 
  x\ 
  be 
  the 
  

   added 
  resistance 
  due 
  to 
  absorption, 
  the 
  capacity 
  should 
  be 
  the 
  

   same 
  in 
  the 
  two 
  cases, 
  or 
  

  

  . 
  , 
  _ 
  (R,'-R,) 
  (R,+>-)-(R/-R 
  . 
  ) 
  (R. 
  + 
  >-) 
  

   • 
  k,'-r;-2(w,+rj 
  

  

  