﻿228 
  J. 
  Trowbridge 
  — 
  Electrical 
  Oscillations 
  on 
  Iron 
  Wires. 
  

  

  (1.) 
  Large 
  copper 
  wire, 
  

  

  11=0-285 
  X10 
  9 
  

   and 
  substituting 
  in 
  Lord 
  Kayleigh's 
  formula, 
  B/= 
  y/^plpR, 
  

   R' 
  = 
  0-66X10 
  9 
  . 
  

   (2.) 
  Large 
  German 
  silver 
  wire, 
  

  

  R=9'2xl0 
  9 
  , 
  

   and 
  substituting 
  in 
  the- 
  series 
  

  

  j 
  i//y 
  i 
  p*w 
  i 
  

   R=R 
  ] 
  1+ 
  T2-R^-r8o-R^ 
  + 
  "-h 
  

  

  R 
  / 
  = 
  9'2X10 
  9 
  . 
  

  

  (3.) 
  Large 
  iron 
  wire, 
  

  

  R=2-5X 
  10 
  9 
  , 
  

  

  and 
  if 
  there 
  is 
  a 
  true 
  time 
  lag, 
  as 
  often 
  stated, 
  such 
  as 
  to 
  pre- 
  

   vent 
  action 
  of 
  the 
  magnetic 
  property 
  of 
  the 
  iron, 
  and 
  if 
  on 
  this 
  

   assumption 
  we 
  make 
  [1=1, 
  

  

  R'=2-78X30 
  9 
  

  

  (4.) 
  Fine 
  copper, 
  

  

  R=3-3X10 
  9 
  

  

  R' 
  = 
  3-5X10 
  9 
  . 
  

  

  (5.) 
  Again, 
  as 
  before, 
  call 
  fi—\ 
  in 
  iron, 
  nickel, 
  and 
  steel. 
  

   The 
  length 
  of 
  these 
  circuits 
  was 
  741 
  meters, 
  the 
  remainder 
  of 
  

   the 
  10 
  "20 
  meters 
  — 
  2*79 
  meters 
  — 
  being 
  of 
  copper 
  wire 
  of 
  

   E/=0-94. 
  

  

  The 
  value 
  of 
  B/ 
  in 
  the 
  separate 
  cases, 
  including 
  in 
  each 
  the 
  

   resistance 
  0*94 
  of 
  the 
  copper 
  portion, 
  was 
  as 
  follows 
  : 
  

  

  Soft 
  iron 
  15-0 
  XlO 
  9 
  

  

  Piano 
  steel 
  20-7 
  XlO 
  9 
  

  

  Nickel 
  30-6 
  XlO 
  9 
  

  

  German 
  silver 
  23-0 
  X 
  10 
  9 
  

  

  The 
  ratio 
  of 
  the 
  strengths 
  of 
  successive 
  discharges 
  during 
  

  

  rT 
  

  

  the 
  oscillation 
  is 
  given 
  by 
  the 
  function 
  e 
  TL 
  , 
  where 
  r 
  is 
  the 
  ohmic 
  

   resistance, 
  T 
  the 
  time 
  of 
  a 
  double 
  oscillation, 
  and 
  L 
  the 
  self- 
  

   induction. 
  The 
  ratio 
  of 
  one 
  discharge 
  to 
  the 
  nth. 
  one 
  after 
  it 
  

  

  rT 
  

  

  is 
  £ 
  n 
  * 
  L 
  . 
  If 
  we 
  assume 
  — 
  and 
  it 
  is 
  a 
  large 
  assumption, 
  but 
  one 
  

   which 
  perhaps 
  the 
  result 
  will 
  in 
  some 
  measure 
  justify 
  — 
  that 
  

   the 
  ratio 
  of 
  the 
  strength 
  of 
  the 
  first 
  to 
  the 
  strength 
  of 
  the 
  last 
  

   visible 
  discharge 
  is 
  more 
  or 
  less 
  a 
  constant, 
  we 
  may 
  make 
  use 
  

  

  of 
  the 
  above 
  data. 
  Denote 
  -^- 
  by 
  A, 
  and 
  call 
  the 
  unknown 
  

  

  21j 
  

  

  