﻿Dielectric 
  Constant 
  of 
  Paraffins. 
  53 
  

  

  a 
  and 
  b 
  are 
  connected 
  to 
  a 
  commercial 
  line 
  delivering 
  an 
  

   alternating 
  current 
  with 
  a 
  pressure 
  of 
  52 
  volts. 
  The 
  

   resistance 
  R 
  is 
  used 
  to 
  regulate 
  the 
  quantity 
  of 
  current 
  

   flowing 
  through 
  the 
  circuit. 
  T 
  is 
  a 
  transformer 
  whose 
  primary 
  

   of 
  about 
  200 
  turns 
  is 
  wound 
  around 
  a 
  core 
  of 
  soft 
  iron 
  wire. 
  

   The 
  secondary 
  of 
  the 
  coil 
  contains 
  about 
  2000 
  turns. 
  C 
  is 
  a 
  

   battery 
  of 
  four 
  leyden-jars 
  each 
  having 
  a 
  capacity 
  of 
  5900 
  

   electrostatic 
  units. 
  T 
  L 
  is 
  a 
  Tesla 
  coil 
  made 
  after 
  the 
  formula 
  

   given 
  by 
  Tesla, 
  and 
  is 
  capable 
  when 
  fed 
  to 
  its 
  full 
  capacity 
  of 
  

   giving 
  a 
  ten-inch 
  spark. 
  In 
  all 
  the 
  following 
  experiments 
  a 
  

   current 
  of 
  about 
  7 
  amperes 
  was 
  taken 
  from 
  the 
  commercial 
  

   line, 
  which 
  would 
  give 
  in 
  the 
  Tesla 
  coil 
  a 
  spark 
  of 
  not 
  more 
  

   than 
  3 
  cm. 
  Gr 
  is 
  a 
  spark-gap 
  consisting 
  of 
  two 
  small 
  iridium"* 
  

   cylinders 
  inserted 
  in 
  f-in. 
  brass 
  spheres. 
  The 
  length 
  of 
  the 
  

   spark-gap 
  can 
  be 
  nicely 
  adjusted 
  by 
  means 
  of 
  a 
  screw-thread 
  

   on 
  the 
  axle 
  of 
  one 
  of 
  the 
  spheres. 
  

  

  The 
  constancy 
  of 
  the 
  spark 
  at 
  this 
  gap 
  is 
  of 
  the 
  greatest 
  

   importance 
  in 
  securing 
  the 
  best 
  possible 
  results 
  from 
  the 
  

   oscillator. 
  A 
  rapidly-rotating 
  disk 
  presenting 
  projections 
  to 
  

   the 
  opposite 
  terminal 
  of 
  the 
  gap 
  gave 
  very 
  indifferent 
  results. 
  

   Zinc 
  balls, 
  polished 
  brass 
  balls, 
  and 
  brass 
  balls 
  with 
  platinum 
  

   terminals, 
  inserted 
  after 
  the 
  fashion 
  of 
  the 
  iridium 
  cylinders, 
  

   were 
  used, 
  but 
  none 
  of 
  these 
  gave 
  the 
  constancy 
  secured 
  

   through 
  the 
  use 
  of 
  the 
  iridium. 
  Platinum 
  terminals 
  gave 
  

   the 
  next 
  best 
  results, 
  but 
  on 
  account 
  of 
  their 
  rapid 
  deteriora- 
  

   tion 
  they 
  required 
  almost 
  constant 
  attention 
  in 
  order 
  to 
  keep 
  

   their 
  surfaces 
  well 
  polished. 
  The 
  iridium 
  gap 
  needs 
  no 
  

   attention 
  except 
  for 
  occasional 
  adjustment 
  of 
  length. 
  

  

  The 
  secondary 
  terminals 
  of 
  the 
  Tesla 
  coil 
  are 
  joined 
  to 
  the 
  

   primary 
  terminals 
  WE 
  (fig. 
  2, 
  p. 
  54) 
  of 
  theBlondlot 
  oscillator. 
  

   The 
  remaining 
  portion 
  of 
  fig. 
  1 
  is 
  shown 
  in 
  detail 
  in 
  fig. 
  3. 
  

  

  The 
  Blondlot 
  oscillator 
  (fig. 
  2) 
  is 
  the 
  modified 
  form 
  used 
  

   by 
  W. 
  D. 
  Coolidgef. 
  Some 
  additions, 
  however, 
  have 
  been 
  

   made 
  in 
  order 
  to 
  bring 
  the 
  adjustments 
  more 
  completely 
  

   under 
  the 
  control 
  of 
  the 
  observer. 
  

  

  The 
  two 
  semicircles 
  composing 
  the 
  primary 
  coil 
  are 
  firmly 
  

   fastened 
  to 
  two 
  hard 
  rubber 
  uprights 
  which 
  are 
  pivoted 
  on 
  the 
  

   crossbar 
  L. 
  The 
  screw 
  D 
  regulates 
  the 
  spark-gap 
  m. 
  A 
  

   spiral 
  spring, 
  not 
  shown 
  in 
  the 
  figure, 
  wound 
  round 
  D, 
  

   keeps 
  the 
  two 
  uprights 
  separated. 
  The 
  wire 
  W 
  is 
  passed 
  

   through 
  a 
  thick- 
  walled 
  glass 
  tube, 
  and 
  is 
  inserted 
  in 
  one 
  of 
  

   the 
  ball-terminals 
  of 
  the 
  primary. 
  The 
  other 
  wire 
  E 
  forms 
  

   a 
  spark-gap 
  at 
  k, 
  which 
  is 
  regulated 
  by 
  the 
  screw 
  G. 
  The 
  

  

  * 
  G. 
  W. 
  Pierce, 
  American 
  Journal 
  of 
  Science, 
  vol. 
  ix. 
  p. 
  256. 
  

   t 
  Annalen 
  der 
  Physik, 
  lxvii. 
  p. 
  578 
  (1899). 
  

  

  