﻿68 
  Z. 
  DeForest 
  — 
  Reflection 
  of 
  Hertzian 
  Waves. 
  

  

  A 
  peculiarity 
  noticed 
  in 
  the 
  action 
  of 
  the 
  tube 
  was 
  its 
  slug- 
  

   gishness 
  in 
  responding 
  to 
  the 
  waves, 
  it 
  seeming 
  to 
  require 
  at 
  

   first 
  a 
  strong 
  excitation 
  to 
  enable 
  it 
  to 
  respond 
  to 
  weaker. 
  At 
  

   the 
  start 
  all 
  bridges 
  were 
  removed 
  before 
  a 
  glow 
  would 
  result. 
  

   The 
  gas 
  seemed 
  to 
  require 
  a 
  "warming 
  up" 
  — 
  its 
  particles 
  

   violently 
  excited 
  electrically 
  — 
  before 
  weaker 
  discharges 
  passed. 
  

  

  It 
  was 
  noticed 
  also 
  that 
  if 
  the 
  hand 
  was 
  placed 
  on 
  the 
  wires 
  

   anywhere, 
  even 
  behind 
  the 
  tube, 
  all 
  glow 
  ceased. 
  The 
  same 
  

   occurred 
  if 
  the 
  wires 
  were 
  grounded, 
  or 
  a 
  very 
  large 
  capacity 
  

   attached. 
  Yet 
  here 
  the 
  tube 
  was 
  subjected 
  at 
  least 
  to 
  the 
  

   incident 
  wave, 
  and 
  theoretically, 
  since 
  a 
  large 
  capacity 
  on 
  both 
  

   wires 
  is 
  like 
  a 
  no-resistance 
  bridge, 
  there 
  should 
  be 
  also 
  perfect 
  

   reflection 
  and 
  standing 
  waves. 
  But 
  the 
  action 
  is 
  as 
  though 
  

   due 
  to 
  free 
  electricity 
  on 
  the 
  wires. 
  Grounding 
  at 
  any 
  point 
  

   keeps 
  its 
  potential 
  zero, 
  and 
  a 
  heaping-up 
  of 
  the 
  charges 
  on 
  

   the 
  wires 
  is 
  impossible. 
  With 
  the 
  electrometer 
  also, 
  no 
  deflec- 
  

   tion 
  was 
  possible 
  so 
  long 
  as 
  a 
  large 
  capacity 
  was 
  attached 
  to 
  the 
  

   parallel 
  wires. 
  

  

  The 
  electrometer 
  used 
  carried, 
  suspended 
  by 
  a 
  glass 
  fiber 
  

   25^™ 
  loiig, 
  a 
  needle 
  consisting 
  of 
  two 
  small 
  aluminum 
  disks, 
  

   moving 
  in 
  the 
  horizontal 
  plane. 
  Parallel 
  to, 
  and 
  a 
  few 
  milli- 
  

   meters 
  above 
  each 
  end 
  of 
  this 
  needle, 
  was 
  fixed 
  a 
  similar 
  disk, 
  

   connected 
  by 
  fine 
  wire 
  to 
  one 
  of 
  the 
  parallel 
  wires. 
  The 
  whole 
  

   was 
  suspended 
  in 
  a 
  vessel 
  of 
  albolene 
  oil. 
  This 
  liquid 
  

   answered 
  admirably, 
  affording 
  the 
  right 
  damping 
  quality 
  and 
  

   dielectric 
  strength. 
  

  

  From 
  the 
  center 
  of 
  the 
  needle 
  a 
  fine 
  platinum 
  wire 
  dipped 
  

   into 
  a 
  small 
  cup 
  of 
  mercury, 
  connected 
  by 
  wire 
  to 
  some 
  capac- 
  

   ity. 
  It 
  was 
  found 
  that 
  the 
  deflection 
  was 
  much 
  increased 
  by 
  

   this, 
  being 
  maximum 
  when 
  the 
  needle 
  was 
  grounded. 
  The 
  

   sensitiveness 
  of 
  the 
  instrument 
  could 
  thus 
  be 
  directly 
  regu- 
  

   lated, 
  and 
  when 
  this 
  leading-out 
  wire 
  was 
  insulated 
  the 
  deflec- 
  

   tion 
  of 
  the 
  needle 
  charged 
  by 
  induction 
  was 
  almost 
  nothing. 
  

  

  A 
  mirror 
  and 
  scale 
  were 
  unnecessary. 
  A 
  light 
  index 
  arm 
  

   of 
  glass, 
  8 
  incbes 
  long, 
  was 
  attached 
  to 
  the 
  upper 
  end 
  of 
  the 
  

   wooden 
  axis 
  of 
  the 
  needle, 
  where 
  the 
  same 
  joined 
  the 
  glass 
  

   suspension 
  fiber, 
  above 
  the 
  surface 
  of 
  the 
  oil. 
  This 
  index 
  

   moved 
  over 
  the 
  face 
  of 
  a 
  mirror 
  scale 
  carrying 
  120 
  divisions. 
  

   The 
  zero 
  was 
  very 
  constant. 
  

  

  For 
  its 
  best 
  working 
  the 
  electrometer 
  did 
  not 
  require 
  the 
  

   amount 
  of 
  energy 
  in 
  the 
  spark 
  discharge 
  that 
  the 
  glow-tube 
  

   demanded. 
  The 
  zinc 
  ball 
  gap 
  was 
  made 
  very 
  short, 
  as 
  well 
  as 
  

   the 
  auxiliary 
  spark 
  gap 
  between 
  the 
  coil 
  and 
  exciter 
  ; 
  and 
  the 
  

   spring 
  interrupter 
  of 
  the 
  coil 
  was 
  adjusted 
  to 
  give 
  as 
  nearly 
  as 
  

   possible 
  a 
  continuous 
  passage 
  of 
  sparks. 
  The 
  surfaces 
  of 
  this 
  

   break 
  were 
  kept 
  constantly 
  smooth, 
  as 
  the 
  slightest 
  falling-off 
  

   of 
  the 
  interrupter, 
  even 
  thou2;h 
  unnoticeable 
  to 
  the 
  ear, 
  was 
  

   at 
  once 
  evidenced 
  by 
  failure 
  of 
  the 
  high-frequency 
  waves. 
  

  

  