﻿TH 
  E 
  

  

  AMERICAN 
  JOURNAL 
  OF 
  SCIENCE 
  

  

  [FOURTH 
  SERIES.] 
  

  

  Aet. 
  l. 
  — 
  Yelocitij 
  of 
  Electric 
  Wccves 
  in 
  Air: 
  by 
  G 
  Y 
  

   Maclean. 
  (With 
  Plate 
  I.) 
  

  

  Hektz 
  determined 
  the 
  wave-length 
  of 
  electric 
  waves 
  in 
  air 
  in 
  

   one 
  of 
  his 
  experiments 
  to 
  be 
  9-6 
  m., 
  with 
  an 
  anti-node 
  TO 
  cm 
  

   behind 
  the 
  reflector. 
  In 
  the 
  case 
  of 
  electric 
  waves 
  alon^ 
  wires 
  

   he 
  found 
  the 
  rate 
  of 
  propagation 
  to 
  be 
  2-8x10'° 
  cms. 
  per 
  sec. 
  

   lie 
  tiirther 
  proved, 
  if 
  slow 
  oscillations 
  were 
  nsed, 
  that 
  the 
  

   lengths 
  of 
  the 
  electric 
  waves 
  along 
  wires 
  and 
  in 
  air 
  without 
  

   wires 
  would 
  differ, 
  but 
  if 
  rapid 
  oscillations 
  were 
  employed 
  the 
  

   engths 
  of 
  the 
  waves 
  would 
  be 
  the 
  same. 
  The 
  truth 
  of 
  this 
  

   has 
  been 
  confirmed 
  by 
  J. 
  J. 
  Thomson 
  and 
  Lecher. 
  

  

  E. 
  Sarasin 
  and 
  de 
  la 
  Rive- 
  concluded 
  from 
  their 
  experi- 
  

   ments 
  that 
  .the 
  wave-lengths 
  determined 
  are 
  independent 
  of 
  

   the 
  dimensions 
  of 
  the 
  oscillator 
  and 
  vary 
  with 
  the 
  size 
  of 
  the 
  

   resonator 
  employed. 
  They 
  showed 
  that 
  the 
  rate 
  of 
  propaga- 
  

   tion 
  of 
  electric 
  waves 
  through 
  air 
  without 
  wires 
  is 
  sensibly 
  the 
  

   same 
  as 
  that 
  along 
  wires. 
  Thus 
  by 
  using 
  a 
  resonator 
  26 
  cms 
  

   m 
  diameter 
  the 
  length 
  of 
  the 
  internode 
  along 
  wires 
  was 
  1-12 
  

   and 
  m 
  air 
  between 
  1-12 
  and 
  1-25 
  m., 
  while 
  a 
  resonator 
  36 
  cm 
  

   m 
  diameter 
  gave 
  the 
  lengths 
  to 
  be 
  147 
  m., 
  air 
  between 
  vi 
  

   and 
  1;8 
  ms. 
  respectively. 
  They 
  claimed 
  that 
  the 
  same 
  oscilla- 
  

   tor 
  gives 
  rise 
  at 
  the 
  same 
  time 
  to 
  waves 
  of 
  different 
  lengths 
  

   that 
  tne 
  waves 
  sent 
  forth 
  are 
  not 
  simple, 
  but 
  are 
  complexes 
  of 
  

   an 
  inhnite 
  number 
  of 
  different 
  waves, 
  in 
  fact 
  a 
  continuous 
  

   electrical 
  spectrum 
  is 
  formed, 
  and 
  that 
  the 
  resonator 
  used 
  acts 
  

   as 
  an 
  analyser 
  picking 
  out 
  from 
  the 
  spectrum 
  those 
  waves 
  

   whose 
  period 
  is 
  peculiar 
  to 
  itself, 
  and 
  to 
  these 
  alone 
  it 
  responds. 
  

  

  2, 
  \mfTuT 
  aS^oTs"''/"'"" 
  '" 
  ^^- 
  ^'^" 
  '' 
  "^^•' 
  ^° 
  P^^^°^' 
  --"' 
  ^°- 
  

  

  Am. 
  Jour. 
  Sci.-Fourth 
  Series, 
  Vol. 
  YIII, 
  No. 
  43.-Jult, 
  1899. 
  

  

  