﻿in 
  a 
  Dust- 
  Tube 
  by 
  an 
  Electric 
  Discharge. 
  

  

  11^ 
  

  

  From 
  these 
  figures 
  we 
  observe 
  that 
  the 
  distance 
  between 
  

   successive 
  striae 
  for 
  a 
  given 
  spark 
  varies 
  with 
  the 
  diameter 
  

   o£ 
  the 
  tube 
  in 
  which 
  the 
  pattern 
  is 
  obtained 
  ; 
  and 
  while 
  the 
  

   stride 
  in 
  wider 
  tubes 
  are 
  distinctly 
  more 
  crowded 
  than 
  in 
  

   narrow 
  tube, 
  there 
  is 
  a 
  particular 
  diameter 
  for 
  which 
  the 
  

   striee-distance 
  is 
  a 
  maximum. 
  This 
  maximum 
  for 
  different 
  

   sparks 
  is 
  found 
  to 
  occur 
  in 
  tubes 
  of 
  different 
  diameters 
  

   (see 
  fig. 
  1). 
  

  

  This 
  variation 
  of 
  striae-distance 
  with 
  diameter 
  of 
  tube 
  is 
  

   shown 
  in 
  fig. 
  I. 
  (PL 
  XXIV.). 
  

  

  The 
  figures 
  given 
  in 
  Table 
  II. 
  refer 
  to 
  sparks 
  obtained 
  from 
  

   the 
  Wimshurst 
  having 
  a 
  battery 
  of 
  condensers 
  in 
  parallel 
  

   with 
  its 
  condensers 
  : 
  those 
  in 
  Table 
  III. 
  to 
  sparks 
  from 
  the 
  

   machine 
  without 
  the 
  battery, 
  i, 
  e., 
  for 
  an 
  oscillation 
  of 
  higher 
  

   frequency. 
  The 
  figures 
  formed 
  in 
  the 
  latter 
  case 
  were 
  

   remarkably 
  well-defined 
  and 
  regular. 
  

  

  Fio-. 
  1. 
  — 
  Variation 
  of 
  strice-distauce 
  witli 
  diameter 
  of 
  tubes. 
  

  

  1-00 
  

  

  •80 
  

  

  •60 
  

  

  •50 
  

  

  />?^ 
  /'^il 
  ! 
  1 
  ! 
  

  

  

  / 
  \/\ 
  !\ 
  1 
  

  

  

  i 
  V 
  

  

  f 
  "^-iL 
  ^^-^ 
  

  

  

  ^ 
  / 
  !^ 
  

  

  ^^^-^1^7^--^^ 
  

  

  

  1/ 
  

  

  i 
  " 
  nil 
  — 
  ®- 
  — 
  ' 
  1 
  ■ 
  — 
  

  

  t 
  1 
  ! 
  

  

  s^© 
  

  

  ^" 
  -i 
  i 
  i 
  1 
  ! 
  

  

  D//iAT£T£fi>s 
  c£ 
  Tube 
  I 
  

  

  Very 
  wide 
  tubes 
  were 
  now 
  taken 
  — 
  about 
  8 
  to 
  15 
  cms. 
  in 
  

   diameter. 
  In 
  these, 
  the 
  final 
  striations 
  did 
  not 
  differ 
  much 
  

   from 
  each 
  other 
  or 
  from 
  those 
  obtained 
  with 
  the 
  wider 
  tubes 
  

   used 
  above. 
  The 
  first 
  stage 
  of 
  the 
  striation 
  w^as 
  a 
  system 
  of 
  

   curiously 
  bifurcated 
  fine 
  close 
  lines. 
  Repeated 
  sparking 
  

   caused 
  the 
  striation 
  to 
  change 
  somewhat 
  in 
  appearance, 
  the 
  

   final 
  effect 
  being 
  a 
  set 
  of 
  lines 
  about 
  '5 
  millimetre 
  apart. 
  

  

  Using 
  tubes 
  of 
  the 
  same 
  diameter 
  but 
  of 
  various 
  lengths, 
  it 
  

   was 
  found 
  that 
  change 
  of 
  length 
  had 
  no 
  observable 
  effect 
  on 
  

   the 
  striae-distance 
  for 
  a 
  given 
  spark. 
  

  

  Tubes 
  having 
  the 
  end 
  remote 
  from 
  the 
  spark-gap 
  stopped 
  

   by 
  a 
  cotton-wool 
  plug 
  were 
  also 
  used. 
  In 
  these 
  cases, 
  the 
  

   striation 
  obtained 
  did 
  not 
  differ 
  from 
  that 
  obtained 
  with 
  open 
  

   tubes. 
  Also 
  a 
  tube 
  was 
  taken, 
  and 
  the 
  striation 
  for 
  a 
  given 
  

   spark 
  was 
  obtained. 
  The 
  powder 
  was 
  observed 
  to 
  jump 
  

   quite 
  a 
  millimetre 
  high 
  at 
  each 
  spark 
  as 
  previously 
  pointed 
  

   out. 
  The 
  end 
  near 
  to 
  the 
  spark-gap 
  was 
  then 
  stopped 
  by 
  a 
  

   plug 
  of 
  cotton-wool. 
  The 
  passage 
  of 
  sparks 
  now 
  left 
  the 
  

  

  