﻿Dielectric 
  Constant 
  of 
  Paraffins. 
  61 
  

  

  grooves, 
  thus 
  making 
  a 
  solid 
  column 
  around 
  the 
  wires. 
  

   Place 
  the 
  argon 
  tube 
  between 
  the 
  free 
  end 
  of 
  the 
  column 
  of 
  

   wax 
  and 
  the 
  movable 
  bridge. 
  When 
  the 
  oscillator 
  is 
  in 
  action 
  

   and 
  the 
  tube 
  located, 
  it 
  will 
  be 
  noticed 
  that 
  the 
  distance 
  

   between 
  the 
  end 
  of 
  the 
  column 
  and 
  the 
  bridge 
  is 
  less 
  than 
  the 
  

   half 
  tube-wave. 
  The 
  column 
  may 
  now 
  be 
  cut 
  off 
  piece 
  by 
  

   piece 
  until 
  the 
  wire 
  node 
  of 
  the 
  half 
  tube-wave 
  rests 
  on 
  the 
  

   end 
  of 
  the 
  column. 
  The 
  length 
  of 
  the 
  column, 
  plus 
  half 
  the 
  

   distance 
  between 
  the 
  Lecher 
  wires 
  (*9 
  cm.), 
  is 
  very 
  approxi- 
  

   mately 
  the 
  half 
  wave-length 
  in 
  paraffin. 
  In 
  the 
  actual 
  

   experiment 
  the 
  length 
  of 
  this 
  column 
  was 
  26*4 
  cm. 
  And 
  if 
  

   to 
  this 
  we 
  add 
  *9 
  cm., 
  we 
  shall 
  get 
  27*3 
  cm. 
  as 
  the 
  approximate 
  

   wave-length. 
  If 
  the 
  base 
  of 
  the 
  apparatus 
  be 
  long 
  enough 
  

   for 
  three 
  half- 
  waves, 
  a 
  column 
  of 
  paraffin 
  85 
  or 
  90 
  cm. 
  long- 
  

   ought 
  to 
  be 
  moulded. 
  For 
  this 
  purpose 
  a 
  box 
  was 
  prepared 
  

   90 
  cm. 
  long, 
  8 
  cm. 
  wide, 
  and 
  8 
  cm. 
  deep, 
  and 
  was 
  lined 
  

   with 
  tinfoil. 
  It 
  was 
  put 
  together 
  with 
  screws, 
  so 
  that 
  it 
  

   could 
  be 
  easily 
  taken 
  apart. 
  By 
  a 
  suitable 
  contrivance, 
  two 
  

   copper 
  wires 
  1*8 
  cm. 
  apart 
  could 
  be 
  stretched 
  through 
  the 
  

   middle 
  of 
  the 
  box 
  and 
  made 
  long 
  enough 
  to 
  be 
  fastened 
  in 
  

   the 
  two 
  supports 
  of 
  the 
  base. 
  The 
  melted 
  paraffin 
  was 
  poured 
  

   into 
  the 
  box 
  and 
  allowed 
  to 
  cool 
  partially. 
  Then 
  a 
  closely- 
  

   fitting 
  top 
  was 
  placed 
  on 
  the 
  paraffin 
  and 
  the 
  whole 
  subjected 
  

   to 
  a 
  pressure 
  brought 
  into 
  play 
  by 
  three 
  iron 
  clamps. 
  A 
  

   gauge 
  inserted 
  in 
  the 
  side 
  of 
  the 
  box 
  recorded 
  the 
  pressure. 
  

   All 
  this 
  was 
  necessary 
  in 
  order 
  to 
  secure 
  columns 
  uniformly 
  

   dense 
  and 
  free 
  from 
  air-holes. 
  Having 
  a 
  column 
  thus 
  

   suitably 
  prepared, 
  one 
  must 
  decide 
  two 
  questions 
  before 
  a 
  

   final 
  determination 
  of 
  the 
  dielectric 
  constant 
  is 
  made. 
  

  

  1st. 
  How 
  much 
  beyond 
  a 
  node 
  may 
  the 
  end 
  of 
  the 
  paraffin 
  

   column 
  rest 
  without 
  changing 
  the 
  position 
  of 
  the 
  second 
  

   bridge 
  ? 
  

  

  2nd. 
  How 
  large 
  in 
  area 
  must 
  the 
  section 
  of 
  the 
  column 
  be 
  

   in 
  order 
  to 
  include 
  the 
  whole 
  of 
  the 
  effective 
  field 
  surrounding 
  

   the 
  Lecher 
  wires 
  ? 
  

  

  The 
  first 
  question 
  can 
  be 
  quickly 
  answered. 
  Fasten 
  the 
  

   moulded 
  column 
  between 
  the 
  two 
  supports, 
  making 
  one 
  end 
  

   rest 
  against 
  the 
  first 
  support. 
  It 
  will 
  be 
  about 
  3 
  mm. 
  from 
  the 
  

   first 
  bridge, 
  since 
  the 
  bridge 
  rests 
  in 
  a 
  groove 
  3 
  mm. 
  from 
  

   the 
  outer 
  surface. 
  Putting 
  the 
  argon 
  tube 
  and 
  the 
  movable 
  

   bridge 
  beyond 
  the 
  column 
  of 
  paraffin 
  and 
  locating 
  the 
  first 
  

   external 
  node 
  (the 
  fourth 
  from 
  the 
  first 
  bridge), 
  it 
  will 
  be 
  

   found 
  that 
  a 
  node 
  (the 
  third) 
  will 
  rest 
  in 
  the 
  column 
  6 
  or 
  8 
  cm. 
  

   from 
  the 
  end. 
  Saw 
  off 
  a 
  2 
  cm. 
  slab 
  from 
  the 
  end 
  of 
  the 
  column 
  

   and 
  again 
  locate 
  the 
  node. 
  Continue 
  this 
  until 
  the 
  wire 
  node 
  of 
  

   the 
  half 
  tube- 
  wave 
  rests 
  upon 
  the 
  end 
  of 
  the 
  column. 
  Frequent 
  

  

  