﻿IN 
  INCREASING 
  THE 
  INTENSITY 
  OF 
  ELECTRICITY. 
  231 
  

  

  creases, 
  until 
  it 
  becomes 
  zero 
  ; 
  the 
  polarity 
  of 
  the 
  needles 
  is 
  then 
  inverted, 
  

   acquires 
  a 
  maximum, 
  decreases 
  to 
  zero 
  again, 
  and 
  then 
  resumes 
  the 
  

   first 
  polarity 
  ; 
  several 
  alternations 
  of 
  this 
  kind 
  being 
  observed.* 
  Now 
  

   this 
  is 
  precisely 
  what 
  would 
  take 
  place 
  if 
  we 
  suppose 
  that 
  the 
  principal 
  

   current 
  induces 
  a 
  secondary 
  one 
  in 
  an 
  opposite 
  direction 
  in 
  the 
  air 
  

   surrounding 
  the 
  conductor, 
  and 
  this 
  again 
  another 
  in 
  an 
  opposite 
  direc- 
  

   tion 
  at 
  a 
  great 
  distance, 
  and 
  so 
  on. 
  The 
  needles 
  at 
  different 
  distances 
  

   would 
  be 
  acted 
  on 
  by 
  the 
  different 
  currents, 
  and 
  thus 
  the 
  phenomena 
  

   described 
  be 
  produced. 
  

  

  The 
  action 
  of 
  the 
  spiral 
  is 
  also 
  probably 
  connected 
  with 
  the 
  fact 
  in 
  

   common 
  electricity 
  called 
  the 
  lateral 
  discharge 
  : 
  and 
  likewise 
  with 
  an 
  

   appearance 
  discovered 
  some 
  years 
  since 
  by 
  Nobili, 
  of 
  a 
  vivid 
  light, 
  pro- 
  

   duced 
  when 
  a 
  Leyden 
  jar 
  is 
  discharged 
  through 
  a 
  flat 
  spiral. 
  

  

  The 
  foregoing 
  views 
  are 
  not 
  presumed 
  to 
  be 
  given 
  as 
  exhibiting 
  the 
  

   actual 
  operation 
  of 
  nature 
  in 
  producing 
  the 
  phenomena 
  described, 
  but 
  

   rather 
  as 
  the 
  hypotheses 
  which 
  have 
  served 
  as 
  the 
  basis 
  of 
  my 
  investi- 
  

   gations, 
  and 
  which 
  may 
  farther 
  serve 
  as 
  formulae 
  from 
  which 
  to 
  deduce 
  

   new 
  consequences 
  to 
  be 
  established 
  or 
  disproved 
  by 
  experiment. 
  

  

  Many 
  points 
  of 
  this 
  subject 
  are 
  involved 
  in 
  an 
  obscurity 
  which 
  

   requires 
  more 
  precise 
  and 
  extended 
  investigation 
  ; 
  we 
  may, 
  however, 
  

   confidently 
  anticipate 
  much 
  additional 
  light 
  from 
  the 
  promised 
  publi- 
  

   cation 
  of 
  Mr 
  Faraday's 
  late 
  researches 
  in 
  this 
  branch 
  of 
  science. 
  

  

  * 
  Cummings's 
  Demonferrande, 
  page 
  247; 
  also 
  Edinburgh 
  Journal, 
  October 
  1826. 
  

  

  