﻿60 
  Scientific 
  Intelligence. 
  

  

  dielectric, 
  is 
  the 
  same 
  as 
  that 
  I 
  used 
  in 
  the 
  case 
  of 
  turpentine 
  and 
  

   castor 
  oil. 
  

  

  Electromagnetic 
  waves 
  were 
  transmitted 
  along 
  two 
  tinned 
  cop- 
  

   per 
  wires 
  2 
  '5 
  millim. 
  in 
  diameter 
  stretched 
  horizontally 
  and 
  par- 
  

   allel 
  to 
  each 
  other 
  at 
  a 
  distance 
  of 
  0*8 
  meter. 
  A 
  resonator 
  of 
  

   gilt 
  copper 
  is 
  placed 
  in 
  a 
  fixed 
  position 
  between 
  the 
  wires 
  ; 
  the 
  

   portion 
  of 
  the 
  transmitting 
  wires 
  beyond 
  the 
  resonator 
  is 
  con- 
  

   tained 
  in 
  a 
  wooden 
  trough 
  4 
  meters 
  in 
  length. 
  The 
  trough 
  being 
  

   filled 
  with 
  liquid, 
  the 
  position 
  is 
  sought 
  at 
  which 
  a 
  movable 
  

   bridge 
  must 
  be 
  placed, 
  joining 
  the 
  wires 
  beyond 
  the 
  resonator 
  to 
  

   cause 
  the 
  spark 
  to 
  disappear 
  ; 
  the 
  distance 
  from 
  the 
  bridge 
  to 
  the 
  

   resonator 
  is 
  then 
  a 
  quarter 
  of 
  the 
  specific 
  wave-length 
  of 
  the 
  

   resonator; 
  the 
  position 
  of 
  the 
  bridge 
  is 
  accurately 
  noted. 
  

  

  That 
  done, 
  I 
  surround 
  the 
  part 
  of 
  the 
  resonator 
  forming 
  the 
  

   condenser 
  with 
  a 
  water-tight 
  bag 
  of 
  parchment-paper 
  which 
  I 
  fill 
  

   with 
  distilled 
  water, 
  and 
  then 
  freeze 
  this 
  water 
  ; 
  the 
  layer 
  of 
  air 
  

   is 
  thus 
  replaced 
  by 
  one 
  of 
  ice. 
  Measuring 
  the 
  wave-length 
  afresh, 
  

   it 
  is 
  found 
  to 
  be 
  considerably 
  greater 
  than 
  in 
  the 
  first 
  experiment, 
  

  

  141 
  

  

  having 
  become 
  of 
  what 
  it 
  was. 
  

  

  3 
  100 
  

  

  The 
  trough 
  is 
  then 
  filled 
  with 
  water 
  which 
  is 
  frozen, 
  and 
  then 
  

   the 
  position 
  of 
  the 
  bridge 
  for 
  disappearance 
  of 
  the 
  spark 
  is 
  again 
  

   sought. 
  For 
  this 
  purpose 
  the 
  ice 
  at 
  the 
  distant 
  end 
  of 
  the 
  trough 
  

   is 
  broken 
  and 
  progressively 
  removed. 
  I 
  ascertained 
  that 
  this 
  

   position 
  is 
  exactly 
  the 
  same 
  as 
  in 
  the 
  first 
  case, 
  when 
  the 
  dielec- 
  

   tric 
  was 
  air. 
  

  

  The 
  experiment 
  four 
  times 
  repeated, 
  varying 
  each 
  time 
  the 
  

   capacity 
  of 
  the 
  condenser, 
  always 
  gave 
  the 
  same 
  result. 
  The 
  

   proposition 
  relative 
  to 
  the 
  wave-length 
  is 
  therefore 
  true 
  for 
  ice 
  as 
  

   well 
  as 
  for 
  other 
  dielectrics. 
  Hence, 
  as 
  shown 
  in 
  my 
  previous 
  

   Note, 
  Maxwell's 
  relation 
  that 
  the 
  dielectric 
  power 
  is 
  also 
  equal 
  to 
  

   the 
  square 
  of 
  the 
  refractive 
  index 
  also 
  holds 
  for 
  electromagnetic 
  

   waves 
  in 
  the 
  case 
  given. 
  

  

  The 
  preceding 
  results, 
  partly 
  unforeseen, 
  led 
  me 
  to 
  determine 
  

   the 
  dielectric 
  constant 
  of 
  ice, 
  using 
  electromagnetic 
  undulations. 
  

   The 
  experiment 
  cited 
  above 
  gave 
  all 
  the 
  data 
  necessary 
  for 
  this 
  

   determination. 
  

  

  For 
  if 
  X 
  and 
  X 
  1 
  are 
  the 
  wave-lengths 
  corresponding 
  to 
  a 
  given 
  

   resonator, 
  working 
  respectively 
  in 
  air 
  and 
  in 
  a 
  substance 
  of 
  

   dielectric 
  power 
  K, 
  we 
  have 
  

  

  T 
  =VK. 
  

  

  A.s 
  stated 
  above, 
  

  

  I 
  found 
  

   X' 
  

  

  _ 
  141 
  

  

  

  X 
  

  

  ~" 
  Too' 
  

  

  ence 
  

  

  K=2 
  

  

  in 
  round 
  

  

  numbers. 
  

  

  The 
  experiment 
  repeated 
  a 
  dozen 
  times 
  always 
  gave 
  the 
  same 
  

   result. 
  I 
  consider 
  the 
  relative 
  error 
  does 
  not 
  exceed 
  -g^, 
  for 
  the 
  

  

  