﻿to 
  the 
  Measurement 
  of 
  Short 
  Electric 
  Waves. 
  253 
  

  

  that 
  I 
  have 
  found 
  to 
  be 
  useful 
  in 
  quantitative 
  experiments 
  on 
  

   electric 
  waves. 
  

  

  The 
  Resonator. 
  — 
  For 
  a 
  receiving 
  instrument 
  I 
  have 
  employed 
  

   a 
  resonating 
  thermal-junction 
  like 
  that 
  of 
  Klemencic 
  and 
  Cole 
  ; 
  

   but 
  instead 
  of 
  a 
  separate 
  galvanometer, 
  I 
  have 
  made 
  the 
  ther- 
  

   mal 
  system 
  a 
  part 
  of 
  the 
  suspension 
  in 
  an 
  apparatus 
  similar 
  in 
  

   other 
  respects 
  to 
  the 
  radio-micrometer 
  of 
  Professor 
  Boys. 
  

   This 
  arrangement 
  is 
  shown 
  in 
  sectional 
  diagrams 
  in 
  figs. 
  2, 
  3, 
  

   and 
  4. 
  

  

  Fig. 
  2 
  is 
  a 
  vertical 
  section 
  through 
  the 
  suspension 
  and 
  per- 
  

   pendicular 
  to 
  the 
  field 
  magnet. 
  Upon 
  a 
  base, 
  B, 
  provided 
  

   with 
  leveling 
  screws, 
  is 
  placed 
  a 
  parabolic, 
  cylindrical 
  reflector, 
  

  

  sawed 
  from 
  a 
  block 
  of 
  wood 
  and 
  covered 
  inside 
  with 
  a 
  copper 
  

   reflecting 
  surface. 
  The 
  cavity 
  formed 
  by 
  this 
  reflector 
  is 
  

   marked 
  it, 
  and 
  the 
  opening 
  of 
  the 
  parabola 
  is 
  at 
  the 
  right. 
  

   Above 
  the 
  reflector 
  and 
  separated 
  from 
  it 
  by 
  a 
  sheet 
  of 
  brass 
  

   is 
  a 
  horse-shoe 
  magnet, 
  J/, 
  with 
  pole 
  pieces 
  coming 
  near 
  

   together 
  and 
  projecting 
  into 
  the 
  brass 
  tube, 
  T, 
  which 
  contains 
  

   the 
  fiber 
  of 
  the 
  suspension. 
  Within 
  the 
  reflecting 
  cavity 
  the 
  

   continuation 
  of 
  this 
  tube 
  is 
  of 
  glass, 
  shown 
  by 
  dotted 
  lines. 
  

   The 
  parabolic 
  reflector 
  has 
  a 
  focal 
  length 
  of 
  2 
  cm 
  and 
  an 
  orifice 
  

   16 
  cm 
  wide 
  by 
  13 
  cm 
  high. 
  The 
  height 
  of 
  the 
  pole 
  pieces 
  is 
  2*5 
  cm 
  

  

  Am. 
  Jour. 
  Scl— 
  Fourth 
  Series, 
  Vol. 
  IX, 
  No. 
  52. 
  — 
  April, 
  1900. 
  

   18 
  

  

  