﻿in 
  a 
  Dust-Tuhe 
  hy 
  an 
  Electric 
  Discharge. 
  

  

  781 
  

  

  influence 
  on 
  the 
  pattern 
  obtained 
  ; 
  thus, 
  referring 
  to 
  fig. 
  II., 
  

   ■^-e 
  have, 
  using 
  starch 
  and 
  lycopodium 
  with 
  the 
  same 
  spark, 
  

   stri?e-distances 
  'b^ 
  mm. 
  and 
  '76 
  mm. 
  respectively. 
  This 
  is 
  

   no 
  doubt 
  a 
  purely 
  mechanical 
  effect, 
  a 
  finer 
  powder 
  such 
  as 
  

   starch 
  taking 
  up 
  a 
  finer 
  pattern 
  than 
  the 
  coarser 
  grained 
  

   lycopodium, 
  while 
  pepper 
  of 
  very 
  similar 
  size 
  and 
  form 
  to 
  

   lycopodium 
  gives 
  a 
  pattern 
  very 
  similar 
  to 
  that 
  with 
  

   lycopodium. 
  

  

  Also, 
  it 
  appears 
  that 
  for 
  circuits 
  of 
  different 
  frequencies 
  

   certain 
  differences 
  are 
  observable 
  among 
  various 
  figures. 
  

   These 
  variations, 
  however, 
  seem 
  irregular 
  and 
  not 
  in 
  any 
  

   obvious 
  proportion 
  to 
  frequencies 
  of 
  the 
  electrical 
  oscillations. 
  

   Thus 
  in 
  fig. 
  III. 
  a 
  variation 
  in 
  the 
  stride 
  -distance 
  in 
  the 
  manner 
  

   to 
  be 
  expected 
  was 
  found, 
  i. 
  e. 
  in 
  the 
  same 
  direction 
  as 
  the 
  

   electrical 
  wave-length. 
  Again 
  in 
  fig. 
  lY., 
  which 
  refers 
  to 
  

   oscillations 
  of 
  known 
  frequencies, 
  no 
  obvious 
  law 
  of 
  variation 
  

   for 
  the 
  striae-distance 
  with 
  electrical 
  wave-length 
  is 
  exhibited. 
  

   Thus, 
  while 
  the 
  ratio 
  of 
  the 
  striae-distances 
  for 
  fig. 
  IV. 
  g 
  k 
  h\<, 
  

   I"!:, 
  that 
  of 
  the 
  corresponding 
  electrical 
  wave-lengths 
  is 
  3'6. 
  

  

  Further, 
  in 
  figs. 
  Y. 
  a 
  and 
  Y. 
  6 
  we 
  have 
  instances 
  of 
  variation 
  

   along 
  the 
  same 
  tube. 
  The 
  explanation 
  of 
  this 
  variation 
  is 
  

   not 
  obvious. 
  In 
  fio;. 
  4 
  the 
  variation 
  of 
  the 
  number 
  of 
  striae 
  

  

  Fig. 
  4. 
  

  

  -Variation 
  of 
  striae-distance 
  alon^ 
  a 
  oiven 
  tube. 
  

  

  10 
  25 
  30 
  55 
  40 
  

  

  D/ 
  STANCE 
  fiLONQ 
  TUBC 
  /N 
  CMS. 
  

  

  per 
  centimetre 
  with 
  distance 
  along 
  the 
  tube 
  is 
  exhibited, 
  and 
  

   as 
  is 
  apparent 
  on 
  examination 
  of 
  figs. 
  Y.a 
  and 
  Y. 
  h 
  this 
  shows 
  

   A-ery 
  approximately 
  equidistantly 
  distributed 
  maxima 
  and 
  

   minima. 
  The 
  distance 
  between 
  successive 
  minima 
  in 
  fig.Y. 
  a 
  

   is 
  indicated 
  by 
  the 
  figures 
  on 
  the 
  curve 
  in 
  fig. 
  4, 
  and 
  appears 
  

   about 
  3 
  or 
  4 
  cms. 
  ; 
  and 
  from 
  this 
  it 
  seems 
  permissible 
  to 
  infer 
  

   the 
  existence 
  of 
  some 
  periodic 
  disturbance 
  whose 
  wave-length 
  

   is 
  of 
  this 
  order. 
  The 
  same 
  phenomenon 
  is 
  seen 
  in 
  fig. 
  Y.h, 
  

   which 
  corresponds 
  to 
  a 
  spark 
  of 
  higher 
  frequency. 
  This 
  

   might 
  perhaps 
  be 
  due 
  to 
  the 
  resonance 
  of 
  the 
  tube 
  to 
  some 
  

   component 
  of 
  the 
  sound 
  of 
  the 
  spark. 
  

  

  