﻿230 
  J. 
  Troivbridge 
  — 
  Electrical 
  Oscillations 
  on 
  Iron 
  Wires. 
  

  

  of 
  the 
  spark, 
  — 
  it 
  is 
  not 
  difficult 
  to 
  show 
  that 
  its 
  influence 
  may 
  

   be 
  very 
  great. 
  

  

  There 
  still 
  remains 
  the 
  fact, 
  not 
  generally 
  recognized, 
  that, 
  

   in 
  Leyden 
  jar 
  discharges 
  through 
  iron 
  wires, 
  the 
  magnetic 
  

   property 
  of 
  the 
  iron 
  has 
  time 
  very 
  materially 
  to 
  modify 
  the 
  

   character 
  of 
  the 
  spark. 
  

  

  We 
  give 
  an 
  example 
  of 
  the 
  measurement 
  of 
  the 
  half-oscilla- 
  

   tion 
  which 
  was 
  the 
  only 
  one 
  visible 
  on 
  the 
  photograph 
  of 
  the 
  

   discharge 
  over 
  iron 
  wires, 
  all 
  the 
  others 
  having 
  been 
  dampened 
  

   or 
  extinguished 
  by 
  the 
  iron, 
  in 
  comparison 
  with 
  the 
  measure- 
  

   ment 
  of 
  the 
  similar 
  half-oscillation 
  on 
  copper 
  wires 
  of 
  the 
  same 
  

   diametei\as 
  the 
  iron 
  wires. 
  The 
  number 
  of 
  oscillations 
  on 
  the 
  

   copper 
  wires 
  was 
  eight. 
  

  

  The 
  total 
  duration 
  of 
  the 
  discharge 
  on 
  iron 
  wires 
  was 
  only 
  

   three 
  million 
  ths 
  of 
  a 
  second, 
  while 
  that 
  on 
  similar 
  copper 
  wire 
  

   was 
  three 
  hundred-thousandths 
  of 
  a 
  second. 
  A 
  steel 
  wire 
  

   gave 
  the 
  same 
  results 
  as 
  the 
  annealed 
  iron 
  wires. 
  

  

  Comparative 
  lengths 
  of 
  first 
  half 
  -oscillation 
  in 
  millimeters. 
  

  

  Fine 
  iron 
  wire. 
  Fine 
  copper 
  wire. 
  

  

  •23 
  -19 
  

  

  •21 
  -20 
  

  

  •19 
  -20 
  

  

  •21 
  -19 
  

  

  Large 
  iron 
  wire. 
  Large 
  copper 
  wire. 
  

   •20 
  -17 
  

  

  •20 
  -18 
  

  

  •19 
  -20 
  

  

  •19 
  -18 
  

  

  I 
  wish 
  to 
  express 
  my 
  deep 
  obligations 
  to 
  my 
  assistant, 
  Mr. 
  

   W. 
  C. 
  Sabine, 
  for 
  his 
  valuable 
  suggestions 
  and 
  for 
  his 
  skill 
  in 
  

   the 
  mechanical 
  details 
  of 
  this 
  investigation. 
  

  

  Conclusions. 
  

  

  1. 
  The 
  magnetic 
  permeability 
  of 
  iron 
  wires 
  exercises 
  an 
  im- 
  

   portant 
  influence 
  upon 
  the 
  decay 
  of 
  electrical 
  oscillations 
  of 
  

   high 
  frequency. 
  This 
  influence 
  is 
  so 
  great 
  that 
  the 
  oscillations 
  

   may 
  be 
  reduced 
  to 
  a 
  half-oscillation 
  on 
  a 
  circuit 
  of 
  suitable 
  

   self-induction 
  and 
  capacity 
  for 
  producing 
  them. 
  

  

  2. 
  It 
  is 
  probable 
  that 
  the 
  time 
  of 
  oscillation 
  on 
  iron 
  wires 
  

   may 
  be 
  changed. 
  Since 
  we 
  have 
  been 
  able 
  to 
  obtain 
  only 
  a 
  

   half-oscillation 
  on 
  iron 
  wires, 
  we 
  have 
  not 
  been 
  able 
  to 
  state 
  

   this 
  law 
  definitely. 
  

  

  3. 
  Currents 
  of 
  high 
  frequency, 
  such 
  as 
  are 
  produced 
  in 
  

   Leyden 
  jar 
  discharges, 
  therefore 
  magnetize 
  the 
  iron. 
  

  

  Jefferson 
  Physical 
  Laboratory, 
  Cambridge, 
  

  

  