﻿in 
  a 
  Dust'luhe 
  hy 
  an 
  Electric 
  Discharge. 
  777 
  

  

  they 
  appear 
  to 
  have 
  fallen 
  very 
  haphazard 
  and 
  not 
  in 
  the 
  

   regular 
  manner 
  necessary 
  for 
  the 
  formation 
  of 
  strise. 
  With 
  

   the 
  other 
  lighter 
  povrders 
  the 
  figure 
  obtained 
  was 
  unsatis- 
  

   factory 
  when 
  compared 
  with 
  that 
  with 
  lycopodium 
  which 
  

   gave 
  by 
  far 
  the 
  finest 
  figures; 
  and 
  while 
  in 
  the 
  case 
  of 
  the 
  

   latter 
  successive 
  sparks 
  added 
  to 
  the 
  definition 
  of 
  the 
  fi.gure, 
  

   with 
  the 
  lighter 
  powders 
  the 
  passage 
  of 
  a 
  spark 
  often 
  

   destroyed 
  the 
  distinctness 
  that 
  had 
  been 
  obtained 
  by 
  previous 
  

   sparks. 
  

  

  In 
  the 
  case 
  of 
  charcoal 
  powder, 
  which 
  was 
  obtained 
  from 
  

   soft 
  wood 
  and 
  having 
  the 
  form 
  of 
  long 
  narrow 
  needles, 
  the 
  

   striation 
  was 
  well 
  defined, 
  the 
  separate 
  striae 
  consisting 
  of 
  

   irregular 
  heaps. 
  The 
  striae-distance, 
  as 
  shown 
  in 
  Table 
  IV., 
  

   was 
  somewhat 
  greater 
  than 
  for 
  lycopodium^ 
  but 
  the 
  distance 
  

   varied 
  very 
  irregularly 
  along 
  the 
  tube. 
  With 
  bath-brick, 
  

   which 
  had 
  been 
  ground 
  in 
  a 
  mortar, 
  producing 
  more 
  or 
  less 
  

   spherical 
  particles, 
  and 
  also 
  with 
  carbonate 
  of 
  iron 
  and 
  with 
  

   starch, 
  a 
  fairly 
  well-defined 
  figure 
  was 
  obtained. 
  

  

  For 
  the 
  subsequent 
  experiments 
  lycopodium 
  was 
  always 
  

   used 
  for 
  the 
  reason 
  just 
  indicated. 
  

  

  Variation 
  of 
  figures 
  with 
  electrical 
  conditions, 
  

  

  For 
  the 
  investigation 
  of 
  the 
  variation 
  of 
  striation 
  with 
  

   change 
  of 
  electrical 
  conditions, 
  a 
  discharging 
  circuit 
  as 
  re- 
  

   presented 
  in 
  fig. 
  2 
  was 
  used. 
  A 
  denotes 
  the 
  discharging 
  

  

  Fis:. 
  2. 
  — 
  VVimsliurst 
  Circuit. 
  

  

  a6 
  

  

  B 
  

  

  knobs 
  of 
  machine 
  ; 
  B 
  the 
  spark-gap 
  ; 
  C 
  a 
  rectangular 
  wire 
  

   circuit 
  containing 
  various 
  condensers. 
  The 
  frequency 
  of 
  the 
  

   electrical 
  oscillations 
  was 
  varied 
  by 
  changing 
  the 
  condensers 
  

   and 
  the 
  rectangular 
  circuit. 
  

  

  It 
  was 
  not 
  possible 
  to 
  measure 
  the 
  frequency 
  of 
  the 
  oscil- 
  

   lations 
  by 
  means 
  of 
  the 
  cymometer, 
  the 
  frequencies 
  in 
  these 
  

   cases 
  being 
  outside 
  the 
  range 
  of 
  the 
  instrument, 
  viz.: 
  -4^2 
  to 
  

   3*0 
  millions 
  per 
  second. 
  

  

  A 
  set 
  of 
  five 
  figures 
  was 
  also 
  obtained 
  using 
  the 
  sparks 
  

   from 
  the 
  machine 
  directly 
  putting 
  various 
  condensers 
  in 
  

  

  PhU. 
  Mag. 
  S. 
  6. 
  Vol. 
  18. 
  No. 
  107. 
  Nov. 
  1909. 
  3 
  F 
  

  

  