﻿240 
  Troichndge, 
  McKay 
  and 
  Howe 
  — 
  Explosive 
  effect 
  of 
  

  

  index 
  of 
  bichromate 
  of 
  potash, 
  rose 
  suddenly 
  at 
  each 
  discharge 
  

   and 
  returned 
  approximately 
  to 
  the 
  zero 
  point. 
  When, 
  how- 
  

   ever, 
  the 
  wire 
  had 
  been 
  heated 
  by 
  repeated 
  discharges, 
  the 
  

   index 
  showed 
  a 
  slow 
  rise 
  in 
  temperature. 
  Even 
  when 
  the 
  

   terminals 
  in 
  the 
  glass 
  tube 
  were 
  connected 
  by 
  a 
  fine 
  wire, 
  a 
  very 
  

   strong 
  electrostatic 
  field 
  was 
  created 
  in 
  the 
  tube. 
  This 
  is 
  shown 
  

   in 
  an 
  interesting 
  manner 
  by 
  fig. 
  1 
  (Plate 
  Y). 
  This 
  photograph 
  

   was 
  obtained 
  by 
  stretching 
  a 
  fine 
  wire 
  over 
  a 
  photographic 
  

   plate 
  and 
  sending 
  a 
  single 
  discharge 
  through 
  the 
  wire, 
  there 
  

   being 
  no 
  spark 
  gap 
  in 
  the 
  circuit. 
  The 
  fine 
  wire 
  vibrated 
  dur- 
  

   ing 
  the 
  discharge 
  ; 
  and 
  when 
  the 
  negative 
  thus 
  obtained 
  was 
  

   closely 
  examined, 
  subsidiary 
  vibrations 
  were 
  shown 
  by 
  many 
  

   black 
  lines 
  approximately 
  parallel 
  to 
  each 
  other. 
  These 
  lines 
  

   were 
  apparently 
  caused 
  by 
  the 
  heat 
  of 
  the 
  discharge 
  melting 
  

   the 
  gelatine 
  where 
  the 
  wire 
  came 
  in 
  close 
  contact 
  with 
  the 
  

   film. 
  The 
  electrostatic 
  field 
  about 
  the 
  wire 
  is 
  exhibited 
  by 
  a 
  

   fern-like 
  discharge 
  at 
  right 
  angles 
  to 
  the 
  wire. 
  

  

  We 
  were 
  soon 
  convinced 
  that 
  heat 
  played 
  a 
  subordinate 
  part 
  

   in 
  the 
  phenomenon 
  shown 
  by 
  the 
  quick 
  rise 
  of 
  the 
  manometer 
  

   index. 
  This 
  rise 
  was 
  apparently 
  dependent 
  upon 
  the 
  electro- 
  

   static 
  conditions 
  rather 
  than 
  upon 
  thermodynamic 
  or 
  magnetic 
  

   phenomena. 
  We, 
  therefore, 
  abandoned 
  the 
  fine 
  wire 
  connec- 
  

   tion 
  and 
  employed 
  a 
  spark 
  gap 
  having 
  a 
  range 
  from 
  zero 
  to 
  

   eighty 
  centimeters. 
  It 
  was 
  possible 
  to 
  still 
  further 
  extend 
  tiiis 
  

   range 
  to 
  two 
  hundred 
  centimeters 
  ; 
  but 
  it 
  was 
  found 
  that 
  the 
  

   range 
  from 
  zero 
  to 
  eighty 
  centimeters 
  exhibited 
  the 
  main 
  

   features 
  of 
  the 
  phenomenon. 
  The 
  following 
  table 
  gives 
  the 
  

   results 
  obtained 
  with 
  discharges 
  produced 
  by 
  three 
  million 
  

   volts, 
  10,000 
  Plante 
  cells, 
  150 
  condensers, 
  charged 
  in 
  multiple 
  

   and 
  discharged 
  in 
  series 
  ; 
  pointed 
  brass 
  terminals 
  in 
  large 
  

   glass 
  cylinder 
  ; 
  gauge 
  consisting 
  of 
  a 
  bent 
  glass 
  tube 
  with 
  a 
  

   potassium 
  bichromate 
  index; 
  Kj 
  and 
  R2, 
  readings 
  of 
  gauge 
  

   before 
  and 
  after 
  discharge 
  ; 
  I), 
  difference 
  of 
  these 
  readings 
  in 
  

   centimetei's 
  ; 
  F, 
  distance 
  between 
  terminals. 
  

  

  It 
  will 
  be 
  seen 
  from 
  the 
  carve 
  A, 
  fig. 
  2, 
  that 
  the 
  explosive 
  

   effect 
  increases 
  closely 
  proportional 
  to 
  the 
  length 
  of 
  the 
  spark 
  

   until 
  the 
  length 
  of 
  fifty 
  centimeters 
  is 
  reached. 
  It 
  then 
  

   begins 
  to 
  diminish. 
  This 
  decrease 
  occurs 
  with 
  the 
  increase 
  of 
  

   electrostatic 
  effect 
  in 
  the 
  field 
  surrounding 
  the 
  spark 
  gap, 
  — 
  or 
  

   in 
  other 
  words, 
  with 
  the 
  divergence 
  or 
  spreading 
  of 
  the 
  electric 
  

   lines 
  of 
  force. 
  The 
  electrostatic 
  effect 
  in 
  this 
  field, 
  when 
  a 
  

   difference 
  of 
  potential 
  of 
  three 
  million 
  volts 
  is 
  generated, 
  is 
  

   very 
  great. 
  Sparks 
  can 
  be 
  drawn 
  from 
  neighboring 
  objects. 
  

   Shocks 
  are 
  felt 
  when 
  the 
  observers 
  touch 
  each 
  other; 
  and 
  

   photographic 
  plates, 
  shielded 
  from 
  light 
  in 
  plate 
  holders, 
  held 
  

   at 
  distances 
  of 
  five 
  or 
  six 
  feet 
  from 
  the 
  terminals, 
  exhibited, 
  on 
  

   development, 
  brush 
  discharges, 
  or 
  Lichtenberg 
  figures. 
  

  

  