﻿70 
  Prof. 
  H. 
  A. 
  Rowland 
  on 
  Electrical 
  

  

  absorption, 
  although 
  I 
  have 
  no 
  doubt 
  one 
  of 
  the 
  more 
  accurate 
  

   methods 
  will 
  show 
  it. 
  

  

  With 
  a 
  condenser, 
  probably 
  of 
  waxed 
  paper, 
  he 
  found 
  : 
  — 
  

  

  Number 
  of 
  complete 
  

  

  Capacity 
  in 
  

  

  Apparent 
  resistance 
  

  

  periods 
  per 
  second. 
  

  

  microfarads. 
  

  

  in 
  ohms. 
  

  

  14-0 
  

  

  4-64 
  

  

  139-6 
  

  

  32-0 
  

  

  4-96 
  

  

  34-1 
  

  

  53-3 
  

  

  4-96 
  

  

  20-5 
  

  

  131*1 
  

  

  4-94 
  

  

  5-2 
  

  

  The 
  first 
  value 
  of 
  the 
  capacity 
  seems 
  to 
  be 
  in 
  error, 
  possibly 
  

   one 
  of 
  calculation. 
  However, 
  the 
  result 
  seems 
  to 
  show 
  a 
  

   nearly 
  constant 
  capacity 
  but 
  a 
  resistance 
  increasing 
  rapidly 
  

   with 
  decrease 
  of 
  period, 
  as 
  Maxwell's 
  formula 
  shows. 
  The 
  

   constant 
  value 
  of 
  the 
  capacity 
  remains 
  to 
  be 
  explained. 
  

  

  Mr. 
  Penniman 
  will 
  continue 
  the 
  investigation 
  with 
  other 
  

   condensers, 
  liquid 
  and 
  solid, 
  as 
  well 
  as 
  plates 
  in 
  electrolytic 
  

   liquids. 
  

  

  The 
  results 
  in 
  the 
  other 
  measurements 
  have 
  been 
  fairly 
  

   satisfactory, 
  but 
  many 
  of 
  the 
  better 
  methods 
  have 
  only 
  been 
  

   recently 
  discovered 
  and 
  are 
  thus 
  untried. 
  But 
  we 
  must 
  

   acknowledge 
  at 
  once 
  that 
  work 
  of 
  the 
  nature 
  here 
  described 
  

   is 
  most 
  liable 
  to 
  error. 
  Every 
  alternating 
  current 
  has, 
  

   not 
  only 
  its 
  fundamental 
  period, 
  but 
  also 
  its 
  harmonics, 
  so 
  

   that 
  very 
  accurate 
  absolute 
  values 
  are 
  almost 
  impossible 
  to 
  

   obtain 
  without 
  great 
  care. 
  To 
  eliminate 
  them, 
  I 
  propose 
  to 
  

   use 
  an 
  arrangement 
  of 
  two 
  parallel 
  circuits, 
  one 
  containing 
  

   a 
  condenser 
  and 
  the 
  other 
  a 
  self-inductance, 
  each 
  with 
  very 
  

   little 
  resistance. 
  The 
  long-period 
  waves 
  will 
  pass 
  through 
  

   the 
  second 
  side 
  and 
  the 
  short 
  ones 
  through 
  the 
  condenser- 
  

   side. 
  By 
  shunting 
  off 
  some 
  of 
  the 
  current 
  from 
  the 
  second 
  

   side, 
  it 
  will 
  be 
  more 
  free 
  from 
  harmonics 
  than 
  the 
  first 
  one. 
  

  

  However, 
  in 
  a 
  multipolar 
  dynamo, 
  especially 
  one 
  containing 
  

   iron, 
  there 
  is 
  danger 
  of 
  long-period 
  waves 
  also, 
  which 
  this 
  

   method 
  might 
  intensify. 
  A 
  second 
  arrangement, 
  using 
  the 
  

   condenser 
  side, 
  might 
  eliminate 
  them. 
  However, 
  many 
  

   dynamos 
  without 
  iron 
  and 
  without 
  too 
  many 
  poles 
  and 
  

   properly 
  wound 
  produce 
  a 
  very 
  good 
  curve 
  without 
  harmonics, 
  

   especially 
  if 
  the 
  resistance 
  in 
  the 
  circuit 
  is 
  replaced 
  by 
  a 
  self- 
  

   inductance 
  having 
  no 
  iron. 
  These 
  remarks 
  apply 
  only 
  to 
  

   absolute 
  determinations. 
  Patios 
  of 
  inductance, 
  self 
  and 
  

   mutual, 
  and 
  capacity 
  are 
  independent 
  of 
  the 
  period, 
  and 
  thus 
  

   it 
  can 
  always 
  be 
  eliminated. 
  Measurements 
  of 
  resistances 
  

   also 
  are 
  independent. 
  

  

  But 
  there 
  are 
  other 
  errors 
  which 
  one 
  who 
  has 
  worked 
  with 
  

   continuous 
  currents 
  may 
  fall 
  into. 
  Nearly 
  all 
  alternating 
  

  

  