﻿Trowbridge 
  and 
  Duane 
  — 
  Velocity 
  of 
  Electric 
  Waves. 
  303 
  

  

  certain 
  arrangements 
  of 
  the 
  condensers, 
  the 
  resonance 
  was 
  

   very 
  sharp, 
  and 
  the 
  position 
  of 
  the 
  movable 
  portion 
  could 
  be 
  

   determined 
  to 
  within 
  *25 
  cm 
  . 
  In 
  the 
  arrangement 
  which 
  was 
  

   finally 
  adopted 
  the 
  resonance 
  was 
  not 
  so 
  sharp. 
  Even 
  in 
  this 
  

   case 
  the 
  distance 
  of 
  the 
  sliding 
  part 
  from 
  the 
  plate 
  a 
  could 
  not 
  

   have 
  been 
  in 
  error 
  by 
  more 
  than 
  2 
  cm 
  . 
  The 
  length 
  65 
  cm 
  was 
  

   finally 
  chosen 
  for 
  its 
  value. 
  

  

  At 
  first 
  it 
  was 
  found 
  impossible 
  to 
  produce 
  anything 
  but 
  a 
  

   complex 
  vibration 
  in 
  the 
  secondary 
  circuit 
  when 
  the 
  spark 
  gap 
  

   was 
  open. 
  Some 
  slight 
  evidence 
  of 
  resonance 
  was 
  obtained, 
  

   but 
  nothing 
  of 
  a 
  decided 
  character. 
  When, 
  however, 
  the 
  

   spark 
  gap 
  was 
  closed, 
  very 
  good 
  resonance 
  ensued 
  and 
  a 
  wave, 
  

   the 
  length 
  of 
  which 
  could 
  be 
  measured 
  to 
  within 
  -4 
  per 
  cent, 
  

   was 
  excited. 
  Some 
  photographs 
  were 
  taken 
  of 
  the 
  spark 
  in 
  the 
  

   secondary 
  circuit, 
  and 
  they 
  snowed 
  immediately 
  the 
  character 
  

   of 
  the 
  complex 
  wave 
  formation. 
  The 
  secondary 
  circuit 
  could 
  

   and 
  did 
  oscillate 
  in 
  three 
  different 
  ways, 
  and 
  the 
  ratios 
  of 
  the 
  

   periods 
  were 
  those 
  of 
  the 
  notes 
  in 
  an 
  open 
  organ 
  pipe, 
  namely 
  

   1:2:3. 
  Usually 
  the 
  lowest 
  or 
  fundamental 
  oscillation 
  together 
  

   with 
  one 
  of 
  the 
  overtones 
  was 
  present 
  ; 
  but 
  several 
  sparks 
  

   were 
  noticed 
  that 
  furnished 
  unmistakable 
  evidence 
  of 
  the 
  

   simultaneous 
  existence 
  of 
  all 
  three. 
  We 
  have 
  observed 
  in 
  a 
  

   circuit 
  10000 
  cm 
  long 
  the 
  same 
  peculiarities 
  of 
  oscillation, 
  excited 
  

   by 
  a 
  primary 
  circuit 
  that, 
  judging 
  from 
  its 
  dimensions, 
  could 
  

   not 
  have 
  been 
  in 
  resonance 
  with 
  the 
  secondary. 
  It 
  was 
  evident 
  

   that 
  the 
  oscillation 
  having 
  nodes 
  at 
  the 
  points 
  marked 
  (fig. 
  2) 
  

   E 
  and 
  F 
  is 
  that 
  whose 
  period 
  is 
  -J 
  of 
  the 
  fundamental. 
  

  

  D 
  

  

  C 
  

  

  a 
  - 
  

  

  

  B 
  

   A 
  

  

  E 
  

  

  G 
  

  

  K 
  

  

  

  r 
  

  

  

  

  

  

  b 
  

  

  

  

  

  J 
  

  

  

  

  

  

  

  

  J 
  

  

  f 
  

  

  

  

  J 
  — 
  

   - 
  

  

  

  

  

  F 
  

  

  H 
  

  

  

  11 
  - 
  1 
  

  

  

  

  L 
  

  

  M 
  

  

  M 
  

  

  A 
  number 
  of 
  measurements 
  of 
  this 
  period 
  have 
  been 
  made, 
  

   and 
  from 
  these 
  several 
  values 
  the 
  velocity 
  of 
  the 
  waves 
  

   has 
  been 
  calculated. 
  The 
  results 
  appear 
  in 
  the 
  following 
  

   table. 
  As 
  an 
  average 
  of 
  five 
  measurements 
  of 
  the 
  wave 
  

   length, 
  none 
  of 
  which 
  differed 
  from 
  the 
  mean 
  by 
  more 
  than 
  

   20 
  cm 
  , 
  the 
  value 
  5888 
  cm 
  was 
  chosen. 
  The 
  distance 
  from 
  the 
  

   mirror 
  to 
  the 
  photographic 
  plate 
  in 
  each 
  case 
  except 
  the 
  last 
  

   was 
  300*l 
  cm 
  . 
  Each 
  of 
  the 
  first 
  five 
  values 
  in 
  the 
  second 
  col- 
  

   umn 
  of 
  the 
  table 
  is 
  an 
  average 
  of 
  30 
  measurements 
  of 
  distances 
  

   ranging 
  in 
  the 
  neighborhood 
  of 
  l 
  cm 
  . 
  The 
  speed 
  of 
  the 
  mirror 
  

  

  