﻿the 
  Frequency 
  of 
  Alternating 
  Currents. 
  347 
  

  

  Method 
  for 
  Determining 
  the 
  Velocity 
  of 
  Sound. 
  

  

  The 
  velocity 
  of 
  sound 
  in 
  air 
  has 
  been 
  determined 
  by 
  many 
  

   observers 
  both 
  in 
  the 
  free 
  air 
  and 
  in 
  air 
  confined 
  in 
  tubes. 
  

   The 
  early 
  experimenters 
  *, 
  of 
  whom 
  Moll, 
  Yon 
  Beek, 
  and 
  

   Kuytenbrouwer 
  in 
  1823 
  did 
  exceptionally 
  careful 
  work, 
  used 
  

   composite 
  sounds 
  in 
  free 
  air. 
  It 
  was 
  suggested 
  by 
  Le 
  Roux 
  f, 
  

   that 
  the 
  temperature 
  measurements 
  were 
  incorrect. 
  This 
  

   view 
  is 
  supported 
  by 
  the 
  observations 
  of 
  Nansen, 
  who 
  found 
  

   that 
  the 
  temperatures 
  gotten 
  on 
  the 
  surface 
  were 
  at 
  variance 
  

   with 
  that 
  taken 
  in 
  his 
  u 
  crow's 
  nest." 
  Therefore, 
  the 
  tem- 
  

   perature 
  measurements 
  of 
  Parry 
  and 
  Foster 
  % 
  certainly 
  did 
  

   not 
  give 
  the 
  true 
  temperature 
  of 
  the 
  path 
  of 
  the 
  sound. 
  In 
  

   1868 
  M. 
  V. 
  Regnault§ 
  reported 
  measurements 
  taken 
  both 
  

   in 
  free 
  air 
  and 
  in 
  tubes 
  which 
  cast 
  so 
  much 
  doubt 
  on 
  the 
  

   earlier 
  measurements 
  that 
  the 
  whole 
  subject 
  was 
  reopened. 
  

  

  Since 
  then, 
  H. 
  Scheebli 
  || 
  and 
  Dr. 
  Low% 
  using 
  pure 
  

   notes, 
  have 
  found, 
  from 
  the 
  positions 
  of 
  maxima 
  in 
  resonating 
  

   tubes, 
  the 
  wave-length 
  of 
  sound. 
  Dr. 
  Low's 
  relative 
  results 
  

   are 
  particularly 
  good 
  ; 
  but 
  his 
  method 
  of 
  standardizing 
  his 
  

   tuning-forks 
  and 
  of 
  determining 
  the 
  vapour-pressure 
  of 
  the 
  

   air 
  in 
  the 
  tubes 
  is 
  unfortunately 
  not 
  above 
  criticism. 
  His 
  

   values 
  for 
  a 
  and 
  y 
  must, 
  however, 
  be 
  very 
  nearly 
  correct 
  and 
  

   so 
  they 
  were 
  used 
  in 
  the 
  preceding 
  tables. 
  

  

  The 
  writer 
  would 
  suggest 
  that 
  the 
  use 
  of 
  a 
  telephone 
  as 
  

   the 
  sounding-body 
  with 
  the 
  periodicity 
  determined 
  directly 
  

   from 
  the 
  motor 
  generator 
  by 
  means 
  of 
  a 
  chronograph 
  would 
  

   be 
  a 
  most 
  satisfactory 
  method 
  of 
  producing 
  the 
  notes 
  desired. 
  

   The 
  telephone 
  may 
  be 
  enclosed 
  if 
  light 
  gases 
  are 
  to 
  be 
  used. 
  

   Drawn 
  tubing 
  with 
  a 
  dry 
  piston 
  would 
  obviate 
  all 
  difficulty 
  

   of 
  determining 
  vapour-pressure. 
  

  

  'Washington 
  University, 
  

   St, 
  Louis, 
  Mo., 
  U.S.A. 
  

  

  * 
  See 
  paper 
  by 
  Le 
  Conte, 
  Phil. 
  Mag., 
  Jan. 
  1864. 
  

  

  t 
  Comptes 
  Rendus, 
  p. 
  392, 
  1867. 
  

  

  X 
  Phil. 
  Trans, 
  p. 
  97, 
  1828. 
  

  

  § 
  Comptes 
  Rendus, 
  p. 
  209, 
  1868. 
  

  

  il 
  Pogg. 
  Ann. 
  p. 
  303, 
  1869. 
  

  

  U 
  Phil. 
  Mag. 
  Sept. 
  1894. 
  

  

  