﻿ill 
  a 
  Dust- 
  Tube 
  by 
  an 
  Electric 
  Discharge. 
  11^ 
  

  

  Experiments 
  with 
  the 
  induction-coil. 
  

  

  A 
  series 
  o£ 
  experiments 
  was 
  now 
  made 
  using 
  an 
  induction- 
  

   coil 
  for 
  the 
  discharge, 
  A 
  spark-gap 
  A 
  in 
  fig. 
  3 
  insulated 
  by- 
  

   Fig. 
  3.— 
  Coil 
  and 
  Circuit. 
  

  

  sticks 
  of 
  vulcanite 
  passing 
  through 
  corks 
  in 
  glass 
  bottles 
  was 
  

   arranged 
  from 
  the 
  terminals 
  of 
  a 
  5 
  -inch 
  induction-coil 
  through 
  

   the 
  primary 
  of 
  which 
  the 
  current 
  from 
  5 
  secondary 
  cells 
  

   was 
  passed. 
  The 
  spark-gap 
  was 
  a 
  centimetre 
  long. 
  The 
  

   discharging 
  circuit 
  was 
  the 
  standard 
  inductance 
  provided 
  

   with 
  the 
  cymometer 
  and 
  various 
  leyden-jars 
  and 
  oil-con- 
  

   densers. 
  The 
  tube 
  containing 
  the 
  lycopodium 
  was 
  placed 
  at 
  

   B 
  in 
  fig. 
  3. 
  The 
  striation 
  was 
  obtained 
  in 
  a 
  tube 
  30 
  cms. 
  

   long 
  and 
  1 
  cm. 
  in 
  diameter, 
  using 
  the 
  standard 
  inductance 
  

   and 
  an 
  oil-condenser 
  in 
  the 
  discharging 
  circuit. 
  

  

  The 
  figure 
  obtained 
  in 
  this 
  case 
  was 
  remarkably 
  different 
  

   from 
  those 
  obtained 
  previously 
  {cf. 
  figs. 
  I. 
  & 
  1\.). 
  

  

  In 
  the 
  first 
  place, 
  the 
  lines 
  of 
  powder 
  were 
  singularly 
  

   straight 
  and 
  parallel 
  and 
  equidistant 
  and 
  very 
  clear. 
  Also 
  

   the 
  striae-distance 
  was 
  very 
  small, 
  smaller 
  than 
  in 
  any 
  of 
  the 
  

   previous 
  cases. 
  It 
  is 
  to 
  be 
  remarked 
  here 
  that 
  the 
  oscilla- 
  

   tions 
  in 
  this 
  case 
  were 
  of 
  higher 
  frequency 
  than 
  those 
  pre- 
  

   viously 
  used. 
  Another 
  peculiarity 
  was 
  observed. 
  The 
  first 
  

   few 
  sparks 
  caused 
  the 
  powder 
  to 
  form 
  the 
  striae 
  very 
  clearly, 
  

   but 
  as 
  the 
  sparking 
  continued 
  the 
  whole 
  system 
  of 
  strias 
  was 
  

   caused 
  to 
  move 
  bodily 
  away 
  from 
  the 
  spark-gap 
  until 
  a 
  

   centimetre 
  or 
  so 
  of 
  the 
  tube 
  near 
  the 
  spark-gap 
  was 
  cleared 
  

   of 
  powder. 
  The 
  powder 
  was 
  observed 
  to 
  jump 
  at 
  the 
  passage 
  

   of 
  a 
  spark, 
  and 
  the 
  rapidity 
  of 
  the 
  sparks 
  and 
  the 
  nearness 
  

   of 
  the 
  lines 
  of 
  powder 
  caused 
  the 
  striation 
  to 
  be 
  invisible 
  

   during 
  the 
  sparking. 
  

  

  Various 
  other 
  frequencies 
  for 
  the 
  oscillations 
  were 
  obtained 
  

   bv 
  adding 
  one 
  or 
  more 
  turns 
  of 
  cable 
  to 
  the 
  standard 
  

   inductance 
  and 
  the 
  striation 
  in 
  each 
  case 
  obtained. 
  Repro- 
  

   ductions 
  of 
  these 
  figures 
  are 
  shown 
  in 
  fig. 
  lY. 
  There 
  does 
  

  

  3F2 
  

  

  