﻿1875.] 
  On 
  Electrical 
  Discharges 
  through 
  Rarefied 
  Gases. 
  455 
  

  

  that 
  its 
  occurrence 
  is 
  not 
  merely 
  a 
  question 
  of 
  the 
  size 
  of 
  the 
  plant, 
  as 
  

   some 
  have 
  supposed, 
  but 
  that 
  it 
  has 
  a 
  deeper 
  meaning, 
  and 
  corresponds 
  

   more 
  closely 
  than 
  has 
  been 
  supposed 
  with 
  the 
  exogenous 
  developments 
  

   seen 
  equally 
  in 
  large 
  and 
  small 
  examples 
  of 
  living 
  plants. 
  

  

  IV. 
  "Experiments 
  on 
  Stratification 
  in 
  Electrical 
  Discharges 
  through 
  

   Rarefied 
  Gases." 
  By 
  William 
  Spottiswoode, 
  M.A., 
  Treas. 
  

   R.S. 
  Received 
  May 
  27, 
  1875. 
  

  

  In 
  the 
  stratified 
  discharges 
  through 
  rarefied 
  gases 
  produced 
  by 
  an 
  

   induction-coil 
  working 
  with 
  an 
  ordinary 
  contact-breaker, 
  the 
  striae 
  are 
  

   often 
  unsteady 
  in 
  position 
  and 
  apparently 
  irregular 
  in 
  their 
  distribution. 
  

   Observations 
  made 
  with 
  a 
  revolving 
  mirror, 
  which 
  I 
  hope 
  to 
  describe 
  on 
  

   another 
  occasion, 
  have 
  led 
  me 
  to 
  conclude 
  that 
  an 
  irregular 
  distribution 
  

   of 
  strise 
  does 
  not 
  properly 
  appertain 
  to 
  stratification, 
  but 
  that 
  its 
  appear- 
  

   ance 
  is 
  due 
  to 
  certain 
  peculiarities 
  in 
  the 
  current 
  largely 
  dependent 
  upon 
  

   instrumental 
  causes. 
  

  

  The 
  beautiful 
  and 
  steady 
  effects 
  obtained 
  by 
  Mr. 
  Grassiot 
  with 
  his 
  

   Leclanche 
  battery, 
  and 
  also 
  more 
  recently 
  by 
  Mr. 
  De 
  La 
  Rue 
  with 
  his 
  

   chloride-of-silver 
  battery, 
  have 
  abundantly 
  shown 
  the 
  possibility 
  of 
  stra- 
  

   tification 
  free 
  from 
  the 
  defects 
  above 
  mentioned 
  ; 
  but 
  it 
  must 
  be 
  admitted 
  

   that 
  the 
  means 
  employed 
  by 
  those 
  gentlemen 
  are 
  almost 
  gigantic. 
  The 
  

   present 
  experiments 
  were 
  undertaken 
  with 
  the 
  view 
  of 
  ascertaining, 
  first, 
  

   how 
  far 
  it 
  was 
  possible 
  to 
  approach 
  towards 
  similar 
  results 
  with 
  instru- 
  

   ments 
  already 
  at 
  my 
  command 
  ; 
  and 
  secondly, 
  whether 
  these 
  would 
  afford 
  

   other 
  modes 
  of 
  attack, 
  beside 
  the 
  battery, 
  on 
  the 
  great 
  problem 
  of 
  strati- 
  

   fied 
  discharges. 
  

  

  The 
  induction-coil 
  used 
  was 
  an 
  " 
  18-inch 
  " 
  by 
  Apps, 
  worked 
  occa- 
  

   sionally 
  by 
  6 
  large 
  chloride-of-silver 
  cells, 
  kindly 
  lent 
  to 
  me 
  by 
  Mr. 
  

   De 
  La 
  Rue, 
  but 
  more 
  usually 
  by 
  10 
  or 
  by 
  20 
  Leclanche 
  cells 
  of 
  the 
  

   smallest 
  size 
  ordinarily 
  made 
  by 
  the 
  Silvertown 
  Company. 
  I 
  have 
  

   also, 
  in 
  connexion 
  with 
  the 
  same 
  coil, 
  120 
  of 
  the 
  latter 
  cells, 
  connected 
  

   in 
  twenties 
  for 
  quantity, 
  and 
  forming 
  6 
  cells 
  of 
  20 
  times 
  the 
  surface 
  

   of 
  the 
  former 
  : 
  these 
  work 
  the 
  coil 
  with 
  the 
  ordinary 
  contact-breaker 
  

   very 
  well, 
  giving 
  11-inch 
  sparks 
  whenever 
  required. 
  A 
  "switch" 
  

   affords 
  the 
  means 
  of 
  throwing 
  any 
  of 
  the 
  three 
  batteries 
  in 
  circuit 
  at 
  

   pleasure. 
  

  

  Having 
  reason 
  to 
  think 
  that 
  the 
  defects 
  in 
  question 
  were 
  mainly 
  due 
  

   to 
  irregularity 
  in 
  the 
  ordinary 
  contact-breaker, 
  I 
  constructed 
  one 
  with 
  a 
  

   steel 
  rod 
  as 
  vibrator 
  (figs. 
  1 
  &2, 
  p. 
  456), 
  having 
  a 
  small 
  independent 
  electro- 
  

   magnet 
  for 
  maintaining 
  its 
  action. 
  The 
  natural 
  vibrations 
  of 
  the 
  rods 
  which 
  

   were 
  tried 
  varied 
  from 
  320 
  to 
  768 
  per 
  second 
  ; 
  while 
  under 
  the 
  action 
  of 
  

   the 
  battery-current 
  and 
  electromagnet 
  they 
  varied 
  from 
  700 
  to 
  2500, 
  or 
  

   thereabouts, 
  per 
  second. 
  The 
  amplitudes 
  of 
  the 
  vibrations 
  were 
  exceed- 
  

   ingly 
  small, 
  in 
  fact 
  not 
  exceeding 
  -01 
  of 
  an 
  inch; 
  and 
  it 
  is 
  to 
  this 
  fact, 
  

  

  