﻿242 
  Trowbridge^ 
  McKay 
  and 
  Howe 
  — 
  Explosive 
  effect 
  of 
  

  

  A 
  

  

  B 
  

  

  A 
  

  

  B 
  

  

  

  

  2-5 
  

  

  14 
  

  

  3-0 
  

  

  1 
  

  

  2-'7 
  

  

  16 
  

  

  2-8 
  

  

  2 
  

  

  3-0 
  

  

  20 
  

  

  2-6 
  

  

  3 
  

  

  3-0 
  

  

  30 
  

  

  1-7 
  

  

  4 
  

  

  3-0 
  

  

  40 
  

  

  1-8 
  

  

  5 
  

  

  3-0 
  

  

  50 
  

  

  1-6 
  

  

  6 
  

  

  3-2 
  

  

  60 
  

  

  1-3 
  

  

  7 
  

  

  3-3 
  

  

  70 
  

  

  1-2 
  

  

  

  

  80 
  

  

  1-2 
  

   1- 
  

  

  When 
  these 
  results 
  are 
  plotted' 
  the 
  lower 
  curve, 
  B, 
  fig. 
  2, 
  

   shows 
  that 
  the 
  spark-length 
  in 
  the 
  secondary 
  circuit 
  increases 
  

   while 
  the 
  primary 
  spark-length 
  is 
  increased 
  up 
  to 
  seven 
  centi- 
  

   meters. 
  When, 
  however, 
  the 
  primary 
  spark-length 
  is 
  increased 
  

   to 
  fourteen 
  centimeters, 
  the 
  length 
  of 
  the 
  secondary 
  spark 
  

   begins 
  to 
  diminish. 
  Thus 
  the 
  maximum 
  of 
  the 
  curve 
  B 
  is 
  a 
  

   little 
  in 
  advance 
  of 
  the 
  minimum 
  of 
  the 
  curve 
  representing 
  

   the 
  explosive 
  action. 
  Since 
  the 
  magnetic 
  flux 
  through 
  the 
  

   little 
  transformer 
  is 
  proportional 
  to 
  the 
  strength 
  of 
  the 
  cur- 
  

   rent 
  in 
  the 
  primary 
  circuit, 
  it 
  is 
  seen 
  that 
  the 
  explosive 
  effect 
  

   is 
  not 
  due 
  to 
  the 
  heat 
  produced 
  by 
  the 
  current. 
  Previous 
  

   experiments 
  by 
  one 
  of 
  us 
  had 
  shown"^ 
  that 
  the 
  apparent 
  resist- 
  

   ance 
  of 
  the 
  primary 
  spark 
  did 
  not 
  increase 
  with 
  the 
  length 
  of 
  

   the 
  spark. 
  The 
  diminution 
  in 
  magnetic 
  flux 
  is 
  due 
  not 
  to 
  

   increase 
  of 
  resistance 
  in 
  the 
  primary 
  circuit 
  but 
  to 
  a 
  shunting 
  

   through 
  the 
  air 
  of 
  the 
  current 
  in 
  this 
  circuit. 
  Fig. 
  1 
  shows 
  

   how 
  great 
  this 
  shunting 
  action 
  can 
  be 
  even 
  with 
  closed 
  circuits 
  

   under 
  the 
  action 
  of 
  high 
  electromotive 
  force. 
  The 
  explosive 
  

   effect, 
  therefore, 
  we 
  are 
  inclined 
  to 
  attribute 
  primarily 
  to 
  an 
  

   electrostatic 
  action. 
  When 
  the 
  primary 
  spark 
  gap 
  is 
  small, 
  a 
  

   silent 
  discharge 
  lowers 
  the 
  difference 
  of 
  potential 
  between 
  the 
  

   spark 
  terminals. 
  As 
  the 
  distance 
  between 
  these 
  terminals 
  

   increases, 
  the 
  silent 
  discharge 
  diminishes, 
  and 
  the 
  difference 
  of 
  

   potential 
  increases 
  until 
  a 
  point 
  is 
  reached 
  at 
  which 
  strong- 
  

   inductive 
  efforts 
  take 
  place 
  between 
  all 
  surrounding 
  objects. 
  

  

  The 
  energy 
  of 
  the 
  electrostatic 
  fleld 
  thus 
  manifests 
  itself 
  by 
  

   what 
  we 
  may, 
  perhaps, 
  term 
  an 
  ionization 
  and 
  electrical 
  attrac- 
  

   tion 
  and 
  repulsion 
  of 
  the 
  particles 
  of 
  the 
  air. 
  This 
  electro- 
  

   static 
  action 
  does 
  not 
  extend 
  to 
  the 
  great 
  distances 
  reached 
  by 
  

   the 
  electromagnetic 
  effect 
  of 
  the 
  fleld. 
  While 
  the 
  latter 
  can 
  

   be 
  detected 
  many 
  miles, 
  the 
  electrostatic 
  effect 
  is 
  confined 
  to 
  a 
  

   few 
  feet. 
  Thus 
  a 
  spark 
  of 
  six 
  or 
  seven 
  feet 
  in 
  length 
  (180 
  to 
  

   210 
  centimeters) 
  is 
  vastly 
  inferior 
  to 
  one 
  of 
  two 
  or 
  three 
  inches 
  

   (5 
  to 
  7-5 
  centimeters) 
  for 
  the 
  purposes 
  of 
  wireless 
  telegraphy. 
  

   In 
  experiments 
  with 
  electric 
  waves 
  by 
  means 
  of 
  coherers 
  we 
  

  

  * 
  Proc. 
  American 
  Academy 
  of 
  Arts 
  and 
  Sciences, 
  vol. 
  xxxiii, 
  No. 
  24. 
  

  

  