﻿J. 
  Trowbridge 
  — 
  Electrical 
  Conductivity 
  of 
  the 
  Ether. 
  389 
  

  

  method 
  the 
  resistance 
  of 
  sparks 
  of 
  different 
  lengths 
  in 
  the 
  

   receiver 
  at 
  this 
  pressure, 
  no 
  difference 
  in 
  resistance 
  could 
  be 
  

   perceived 
  between 
  a 
  spark 
  of 
  six 
  inches 
  in 
  length 
  and 
  one 
  of 
  

   three 
  inches 
  in 
  length. 
  

  

  The 
  secondary 
  spark 
  gap 
  was 
  next 
  placed 
  in 
  a 
  chamber 
  of 
  

   air 
  which 
  was 
  compressed 
  to 
  four 
  atmospheres. 
  This 
  amount 
  

   of 
  compression 
  made 
  no 
  difference 
  in 
  the 
  resistance 
  to 
  the 
  dis- 
  

   ruptive 
  discharges. 
  The 
  secondary 
  spark 
  was 
  also 
  obtained 
  in 
  

   hydrogen 
  gas 
  generated 
  by 
  electrolysis 
  at 
  atmospheric 
  pressure, 
  

   and 
  no 
  appreciable 
  difference 
  in 
  resistance 
  between 
  this 
  gas 
  

   and 
  air 
  was 
  noticed. 
  The 
  length 
  of 
  spark 
  which 
  could 
  be 
  

   obtained 
  with 
  a 
  given 
  voltage 
  was 
  somewhat 
  more 
  in 
  hydrogen 
  

   than 
  in 
  air. 
  It 
  was 
  interesting, 
  in 
  the 
  next 
  place, 
  to 
  determine 
  

   by 
  this 
  method 
  whether 
  differences 
  in 
  the 
  material 
  of 
  the 
  

   spark 
  gaps 
  made 
  any 
  difference 
  in 
  the 
  resistances 
  observed 
  in 
  

   the 
  case 
  of 
  disruptive 
  discharges.* 
  I 
  accordingly 
  employed 
  

   terminals 
  of 
  platinum, 
  iron, 
  aluminum, 
  brass, 
  cadmium, 
  and 
  

   zinc, 
  and 
  could 
  perceive 
  no 
  difference. 
  Moreover, 
  any 
  dif- 
  

   ference 
  of 
  resistance 
  between 
  spheres 
  and 
  between 
  pointed 
  

   terminals, 
  or 
  between 
  a 
  point 
  and 
  a 
  plane, 
  seemed 
  to 
  be 
  inap- 
  

   preciable. 
  AVith 
  powerful 
  discharges 
  such 
  differences, 
  if 
  they 
  

   exist, 
  apparently 
  disappear. 
  The 
  secondary 
  spark 
  was 
  next 
  

   placed 
  in 
  a 
  heated 
  flame. 
  It 
  is 
  well 
  known 
  that 
  the 
  spark 
  

   length 
  can 
  be 
  thus 
  greatly 
  increased. 
  On 
  photographing 
  a 
  

   spark 
  in 
  an 
  additional 
  gap, 
  the 
  resistance 
  appeared 
  to 
  be 
  

   slightly 
  increased 
  in 
  the 
  flame 
  ; 
  doubling 
  the 
  length 
  of 
  this 
  

   spark 
  however, 
  made 
  no 
  change 
  in 
  the 
  resistance 
  that 
  was 
  

   encountered 
  in 
  the 
  heated 
  medium. 
  The 
  phenomenon 
  was 
  

   exactly 
  analogous 
  to 
  that 
  observed 
  in 
  the 
  receiver 
  exhausted 
  to 
  

   100 
  cm 
  . 
  I 
  was 
  interested 
  to 
  observe 
  whether 
  heating 
  the 
  spark 
  

   in 
  the 
  primary 
  of 
  a 
  Thomson 
  Tesla 
  transformer 
  produced 
  any 
  

   marked 
  change 
  in 
  the 
  high 
  tension 
  spark 
  of 
  its 
  secondary. 
  It 
  

   was 
  evident 
  that 
  it 
  was 
  detrimental. 
  The 
  high 
  tension 
  sparks 
  

   immediately 
  ceased 
  to 
  jump 
  at 
  the 
  extreme 
  sparking 
  distance 
  

   of 
  the 
  terminals. 
  Following 
  this 
  train 
  of 
  thought, 
  I 
  next 
  

   placed 
  a 
  spark 
  gap 
  of 
  the 
  primary 
  of 
  the 
  above 
  mentioned 
  

   transformer 
  between 
  the 
  poles 
  of 
  a 
  very 
  powerful 
  magnet, 
  giv- 
  

   ing 
  a 
  field 
  of 
  certainly 
  ten 
  thousand 
  lines 
  to 
  the 
  centimeter. 
  

   It 
  is 
  well 
  known 
  that 
  when 
  such 
  a 
  field 
  is 
  excited, 
  the 
  primary 
  

   spark 
  appears 
  to 
  be 
  blown 
  out 
  with 
  a 
  loud 
  report 
  and 
  a 
  great 
  

   increase 
  of 
  length 
  of 
  spark 
  is 
  obtained 
  in 
  the 
  secondary 
  of 
  the 
  

   transformer. 
  Applying 
  the 
  same 
  method, 
  I 
  photographed 
  the 
  

   spark 
  of 
  .the 
  additional 
  spark 
  gap 
  and 
  found 
  no 
  difference 
  in 
  

   resistance 
  whether 
  the 
  magnetic 
  field 
  was 
  excited 
  or 
  not 
  : 
  or 
  

   when 
  the 
  spark 
  jumped 
  across 
  the 
  magnetic 
  lines 
  or 
  in 
  the 
  

  

  *Rhigi 
  ovo 
  Cimento 
  (2), 
  16, 
  p. 
  97, 
  1876; 
  De 
  la 
  Rue 
  and 
  Hugo 
  Muller, 
  Phil. 
  

   Trans., 
  169, 
  Pt. 
  1, 
  p. 
  93, 
  1878. 
  

  

  