﻿60 
  Mr. 
  W. 
  G. 
  Hormell 
  on 
  the 
  

  

  of 
  short 
  electrical 
  waves, 
  and 
  that 
  the 
  magnetization 
  of 
  iron 
  

   is 
  not 
  able 
  to 
  follow 
  oscillations 
  as 
  high 
  as 
  800,000,000 
  per 
  

   second. 
  These 
  conclusions 
  agree 
  with 
  those 
  of 
  Hertz 
  * 
  and 
  

   Lodge 
  f- 
  But 
  St. 
  John 
  J 
  found 
  a 
  difference 
  of 
  wave-length 
  

   in 
  iron 
  and 
  copper 
  of 
  from 
  1-J 
  to 
  3 
  per 
  cent. 
  This 
  difference, 
  

   however, 
  was 
  for 
  oscillations 
  of 
  115,000,000 
  reversals 
  per 
  

   second. 
  

  

  Dielectric 
  Constant 
  of 
  Paraffin, 
  

  

  Maxwell 
  has 
  shown 
  theoretically 
  that 
  the 
  dielectric 
  con- 
  

   stant 
  of 
  a 
  substance 
  is 
  equal 
  to 
  the 
  square 
  of 
  the 
  index 
  of 
  

   refraction. 
  The 
  index 
  of 
  refraction 
  of 
  a 
  given 
  substance 
  

   for 
  electrical 
  waves, 
  as 
  well 
  as 
  for 
  light 
  waves, 
  is 
  the 
  ratio 
  

   of 
  their 
  relative 
  velocities 
  in 
  air 
  and 
  in 
  the 
  given 
  substance. 
  

   But 
  since 
  the 
  ratio 
  of 
  the 
  velocity 
  is 
  equal 
  to 
  the 
  ratio 
  of 
  the 
  

   wave-lengths, 
  we 
  have 
  

  

  K 
  

  

  -MU 
  

  

  where 
  X 
  a 
  = 
  the 
  wave-length 
  of 
  a 
  given 
  electrical 
  disturbance 
  

  

  in 
  air 
  ; 
  

   \ 
  s 
  = 
  the 
  wave-length 
  of 
  the 
  same 
  electrical 
  disturbance 
  

  

  in 
  the 
  given 
  substance 
  ; 
  

   fi 
  = 
  index 
  of 
  refraction 
  ; 
  

   K 
  = 
  dielectric 
  constant. 
  

  

  The 
  Blondlot 
  oscillator 
  offers 
  a 
  unique 
  and 
  very 
  satisfactory 
  

   means 
  of 
  measuring 
  the 
  wave-length 
  in 
  air 
  and 
  in 
  the 
  given 
  

   substance. 
  This 
  means 
  is 
  satisfactory, 
  because 
  one 
  is 
  able 
  to 
  

   keep 
  the 
  oscillator 
  in 
  a 
  constant 
  condition, 
  thus 
  making 
  the 
  

   wave-length 
  in 
  air 
  a 
  constant 
  for 
  a 
  given 
  combination. 
  The 
  

   method 
  of 
  securing 
  the 
  wave-length 
  in 
  air 
  has 
  been 
  described, 
  

   and 
  it 
  now 
  remains 
  to 
  indicate 
  the 
  way 
  in 
  which 
  the 
  wave- 
  

   length 
  in 
  paraffin 
  may 
  be 
  obtained. 
  

  

  Let 
  us 
  suppose 
  that 
  the 
  oscillator 
  is 
  adjusted 
  for 
  a 
  half 
  

   wave-length 
  of 
  about 
  40 
  cm. 
  Take 
  a 
  block 
  of 
  paraffin 
  40 
  cm. 
  

   long, 
  6 
  cm. 
  wide, 
  and 
  8 
  cm. 
  thick. 
  It 
  can 
  be 
  readily 
  sawed 
  

   from 
  a 
  commercial 
  cake 
  by 
  means 
  of 
  a 
  table 
  rip-saw. 
  With 
  

   this 
  same 
  saw 
  make 
  two 
  grooves 
  1*8 
  cm. 
  apart 
  and 
  half-way 
  

   through 
  one 
  side. 
  Bring 
  the 
  block 
  up 
  under 
  the 
  two 
  Lecher 
  

   wires, 
  making 
  them 
  lie 
  in 
  the 
  grooves 
  and 
  placing 
  the 
  end 
  of 
  

   the 
  block 
  against 
  the 
  support 
  of 
  the 
  first 
  bridge. 
  Using 
  a 
  

   hot 
  iron 
  and 
  a 
  piece 
  of 
  paraffin, 
  run 
  the 
  melted 
  wax 
  into 
  the 
  

  

  * 
  ' 
  Electric 
  Waves,' 
  p. 
  113. 
  

  

  t 
  ' 
  Modern 
  Views 
  of 
  Electricity,' 
  p. 
  101 
  (1889). 
  

  

  X 
  Proceedings 
  of 
  American 
  Academy, 
  p. 
  218 
  (1894). 
  

  

  