﻿L. 
  DeFovest 
  — 
  Reflection 
  of 
  Hertzian 
  Waves. 
  

  

  69 
  

  

  The 
  decremeDt 
  of 
  amplitudes 
  in 
  each 
  train 
  of 
  wav^es 
  here 
  

   sent 
  out 
  is 
  found 
  to 
  be 
  such 
  that 
  the 
  standing 
  waves 
  created 
  

   decrease 
  rapidly 
  with 
  increasing 
  distances 
  from 
  the 
  reflecting 
  

   body. 
  This 
  decrement 
  completely 
  over-masks, 
  in 
  copper 
  wires, 
  

   that 
  due 
  to 
  attenuation 
  along 
  the 
  wires, 
  for 
  the 
  lengths 
  con- 
  

   sidered. 
  

  

  

  

  

  

  

  1 
  ; 
  

  

  1 
  

  

  I 
  

  

  1 
  

  

  1 
  

   i 
  1 
  

  

  1-50 
  

   1-40 
  

  

  i-so 
  

  

  1-20 
  

   I'lO 
  

  

  

  

  

  

  

  ! 
  

  

  

  

  j 
  

   1 
  

  

  1 
  

  

  ! 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  /^ 
  

  

  

  

  /* 
  

  

  I 
  

  

  

  

  

  

  1 
  = 
  1 
  — 
  . 
  

  

  

  

  

  /.. 
  

  

  . 
  \ 
  

  

  

  1 
  

  

  \ 
  

  

  V 
  

  

  

  

  

  

  

  

  

  

  / 
  

  

  

  

  

  \ 
  

  

  \ 
  

  

  

  / 
  

  

  \ 
  

  

  

  

  

  

  100 
  

  

  

  / 
  

  

  

  

  / 
  

  

  

  

  \] 
  

  

  f 
  

  

  

  

  / 
  

  

  

  

  •90 
  

  

  V. 
  

  

  ^ 
  

  

  

  

  V 
  

  

  

  

  V 
  

  

  

  

  

  

  

  

  100 
  150 
  200 
  350 
  

  

  Distances 
  from 
  Eads 
  of 
  Wires 
  to 
  Bridge. 
  

  

  300cm3 
  

  

  This 
  electrometer 
  gave 
  the 
  accompanying 
  curve, 
  fig. 
  5, 
  simi- 
  

   lar 
  to 
  those 
  observed 
  by 
  Bjerknes, 
  Barton, 
  and 
  others. 
  As 
  

   it 
  was 
  impracticable 
  to 
  move 
  the 
  electrometer 
  along 
  the 
  wires 
  

   the 
  foUowing 
  method 
  was 
  used 
  : 
  — 
  Wires 
  9*6 
  meters 
  long 
  were 
  

   employed 
  and 
  the 
  instrument 
  stationed 
  -i'S 
  meters 
  from 
  the 
  

   end. 
  One 
  no-resistance 
  bridge 
  was 
  placed 
  across 
  the 
  wires 
  at 
  

   a 
  point 
  three-fourths 
  of 
  a 
  natural 
  wave-length 
  beyond 
  the 
  elec- 
  

   trometer. 
  This 
  was 
  alternately 
  raised 
  and 
  lowered, 
  so 
  that 
  

   reflection 
  alternately 
  occurred 
  from 
  it 
  and 
  from 
  a 
  similar 
  

   bridge 
  moved 
  along 
  the 
  line 
  towards 
  the 
  ends. 
  

  

  The 
  action 
  of 
  the 
  coil 
  is 
  at 
  best 
  so 
  irregular 
  that 
  measure- 
  

   ments 
  must 
  be 
  made 
  as 
  nearly 
  simultaneously 
  as 
  possible. 
  

   First 
  throws 
  of 
  the 
  electrometer 
  needle 
  were 
  read, 
  as 
  much 
  

   more 
  satisfactory 
  and 
  regular 
  than 
  mean 
  deflections. 
  From 
  30 
  

   to 
  40 
  good 
  alternate 
  readings 
  were 
  taken 
  for 
  each 
  position 
  of 
  

   the 
  sliding 
  bridge 
  ; 
  the 
  mean 
  ratios 
  of 
  the 
  swings 
  for 
  the 
  two 
  

   bridges 
  give 
  the 
  relative 
  amplitudes 
  of 
  the 
  two 
  waves. 
  These 
  

   ratios 
  are 
  plotted 
  as 
  ordinates, 
  and 
  the 
  distances 
  of 
  the 
  sliding 
  

   bridge 
  from 
  the 
  electrometer 
  as 
  abscissge. 
  As 
  the 
  distance 
  

  

  