﻿Dielectric 
  Constant 
  of 
  Paraffins. 
  

  

  63 
  

  

  uniform 
  density. 
  The 
  dielectric 
  constant 
  of 
  a 
  column 
  moulded 
  

   without 
  pressure 
  differed 
  as 
  much 
  as 
  3 
  per 
  cent, 
  from 
  that 
  

   of 
  a 
  column 
  of 
  the 
  same 
  kind 
  of 
  paraffin 
  moulded 
  under 
  

   pressure. 
  

  

  In 
  Table 
  VI. 
  (p. 
  65) 
  will 
  be 
  found 
  the 
  dielectric 
  constant 
  

   of 
  two 
  kinds 
  of 
  oil, 
  a 
  paraffin 
  oil 
  and 
  a 
  " 
  transformer-oil." 
  This 
  

   grade 
  of 
  paraffin 
  oil 
  is 
  sometimes 
  used 
  for 
  transformers 
  ; 
  but 
  the 
  

   so-called 
  " 
  transformer-oil 
  " 
  is 
  said 
  by 
  the 
  wholesale 
  dealers 
  

   to 
  be 
  the 
  best 
  oil 
  procurable 
  for 
  transformer 
  work. 
  In 
  order 
  

   to 
  make 
  the 
  necessary 
  measurements 
  with 
  these 
  oils, 
  a 
  tele- 
  

   scoping 
  box 
  was 
  made 
  and 
  lined 
  with 
  tinfoil. 
  The 
  ends 
  were 
  

   constructed 
  of 
  thin 
  rubber 
  plates, 
  and 
  through 
  them 
  the 
  

   Lecher 
  wires 
  were 
  stretched. 
  When 
  the 
  nodes 
  rested 
  on 
  or 
  

   near 
  the 
  rubber 
  ends, 
  the 
  wave-length 
  in 
  air 
  was 
  not 
  changed 
  

   by 
  the 
  pressure 
  of 
  the 
  box. 
  The 
  box 
  was 
  filled 
  with 
  oil, 
  and 
  

   the 
  length 
  adjusted 
  until 
  the 
  outer 
  end 
  rested 
  on 
  the 
  third 
  

   node. 
  The 
  box 
  was 
  also 
  filled 
  with 
  melted 
  paraffin, 
  and 
  the 
  

   temperature 
  effect 
  on 
  the 
  position 
  of 
  the 
  node 
  was 
  noted. 
  

  

  Table 
  V. 
  shows 
  how 
  the 
  index 
  of 
  refraction, 
  and 
  therefore 
  

   the 
  dielectric 
  constant, 
  increased 
  as 
  the 
  temperature 
  decreased. 
  

   It 
  is 
  very 
  probable 
  that 
  the 
  change 
  of 
  the 
  dielectric 
  constant 
  

   can 
  be 
  accounted 
  for 
  on 
  the 
  ground 
  of 
  the 
  change 
  in 
  density. 
  

   The 
  densities 
  at 
  79° 
  C. 
  and 
  18° 
  C. 
  are 
  given 
  in 
  the 
  table. 
  

  

  Table 
  V. 
  

  

  Temperature. 
  

  

  Index 
  of 
  

   Eefractiou. 
  

  

  Dielectric 
  

   Constant. 
  

  

  Density. 
  

  

  °0. 
  

  

  

  

  

  79 
  

  

  1-44(7) 
  

  

  2-09 
  (5) 
  

  

  •764 
  

  

  71 
  

  

  1-45(6) 
  

  

  2-12(5) 
  

  

  

  65 
  

  

  1-46(3) 
  

  

  2-14(0) 
  

  

  

  56o 
  

  

  1-47(1) 
  

  

  2-16 
  (3) 
  

  

  

  53-7 
  

  

  1-47(5) 
  

  

  2-17(6) 
  

  

  

  18 
  

  

  1-48 
  (2) 
  

  

  2-19 
  (8) 
  

  

  •908 
  

  

  In 
  order 
  to 
  illustrate 
  the 
  method 
  by 
  which 
  the 
  dielectric 
  

   constant 
  of 
  each 
  column 
  for 
  each 
  wave-length 
  was 
  determined, 
  

   I 
  have 
  selected 
  a 
  set 
  of 
  readings 
  at 
  random. 
  They 
  are 
  the 
  

   data 
  secured 
  for 
  column 
  1 
  of 
  the 
  no. 
  120 
  paraffin. 
  

  

  Diameter 
  of 
  primary 
  5*00 
  cm. 
  

  

  Length 
  of 
  wave 
  in 
  air 
  40*85 
  „ 
  

  

  Length 
  of 
  tube-wave 
  39*24 
  „ 
  

  

  Length 
  of 
  column 
  83*00 
  „ 
  

  

  