﻿AND 
  BATTERY 
  DISCHARGER, 
  ETC., 
  ETC. 
  371 
  

  

  , 
  *i*v,., 
  

  

  of 
  a 
  luminous 
  appearance 
  in 
  its 
  immediate 
  vicinity, 
  where 
  the 
  electric 
  

   matter, 
  converging 
  from 
  the 
  adjoining 
  space, 
  becomes 
  sufficiently 
  in- 
  

   tense 
  to 
  be 
  productive 
  of 
  light 
  ; 
  but 
  it 
  does 
  not 
  produce 
  the 
  striking 
  

   appearance 
  of 
  the 
  luminous 
  brush. 
  

  

  As, 
  agreeably 
  to 
  Du 
  Fay's 
  theory, 
  the 
  knob, 
  whether 
  vitreously 
  or 
  

   resinously 
  electrified, 
  is 
  surcharged 
  with 
  an 
  electric 
  fluid, 
  the 
  projectile 
  

   power 
  ought 
  to 
  be 
  as 
  great 
  in 
  the 
  one 
  case 
  as 
  in 
  the 
  other 
  ; 
  and 
  the 
  

   long 
  spark 
  and 
  the 
  brush, 
  should 
  be 
  producible 
  in 
  either 
  case. 
  

  

  ON 
  SOME 
  INFERENCES 
  FROM 
  THE 
  PHENOMENA 
  OF 
  THE 
  ELECTRIC 
  

   SPARK, 
  IN 
  A 
  RECENT 
  WORK 
  ON 
  HEAT 
  AND 
  ELECTRICITY. 
  

  

  By 
  the 
  Author 
  of 
  the 
  preceding 
  Article. 
  

  

  In 
  his 
  valuable 
  work 
  on 
  heat 
  and 
  electricity, 
  Dr 
  Thompson 
  states 
  

   that 
  if 
  a 
  long 
  spark 
  be 
  taken 
  between 
  two 
  knobs, 
  as 
  when 
  severally 
  

   attached 
  to 
  the 
  positive 
  and 
  negative 
  conductors 
  of 
  the 
  electrical 
  ma- 
  

   chine 
  ; 
  the 
  portion 
  of 
  the 
  spark 
  near 
  the 
  positive 
  knob 
  exhibits 
  all 
  the 
  

   characters 
  of 
  positive 
  electricity, 
  while 
  the 
  remaining 
  portion 
  pro- 
  

   ceeding 
  from 
  the 
  other 
  knob 
  displays 
  all 
  the 
  characters 
  of 
  negative 
  

   electricity. 
  Although 
  the 
  learned 
  and 
  ingenious 
  author 
  does 
  not 
  state 
  

   what 
  differences 
  there 
  are 
  between 
  the 
  different 
  portions 
  of 
  the 
  spark, 
  and 
  

   wherefore, 
  if 
  any 
  exist; 
  he 
  can, 
  without 
  a 
  petitio 
  principii, 
  assume 
  that 
  

   they 
  are 
  such 
  as 
  to 
  justify 
  his 
  conclusion. 
  He 
  proceeds 
  to 
  allege 
  that 
  

   there 
  can 
  be 
  no 
  doubt 
  that 
  every 
  spark 
  consists 
  of 
  two 
  electricities 
  ; 
  

   which, 
  issuing 
  severally 
  from 
  their 
  respective 
  knobs, 
  terminate 
  their 
  

   career 
  by 
  uniting 
  at 
  the 
  non-luminous 
  portion 
  of 
  the 
  spark, 
  which 
  is 
  

   at 
  a 
  distance 
  from 
  the 
  negative 
  knob, 
  of 
  about 
  one-third 
  of 
  the 
  inter- 
  

   val. 
  Upon 
  these 
  grounds 
  he 
  infers 
  that 
  the 
  positive 
  electricity 
  occu- 
  

   pies 
  two-thirds 
  of 
  the 
  length 
  of 
  the 
  spark, 
  the 
  negative 
  one-third. 
  

  

  I 
  presume 
  that, 
  agreeably 
  to 
  the 
  theory 
  which 
  supposes 
  the 
  exist- 
  

   ence 
  of 
  two 
  fluids, 
  when 
  the 
  equilibrium 
  between 
  oppositely 
  excited 
  

   surfaces 
  is 
  restored 
  by 
  a 
  discharge, 
  whether 
  in 
  the 
  form 
  of 
  a 
  spark 
  or 
  

   otherwise, 
  there 
  must 
  be 
  two 
  jets 
  or 
  currents 
  passing 
  each 
  other; 
  the 
  

   one 
  conveying 
  as 
  much 
  of 
  the 
  resinous 
  as 
  the 
  other 
  does 
  of 
  the 
  vitre- 
  

   ous 
  electricity. 
  Of 
  course 
  no 
  part 
  of 
  a 
  spark 
  can 
  be 
  more 
  negative 
  

  

  