﻿474 
  

  

  Prof. 
  8, 
  R. 
  Cook 
  

  

  has 
  been 
  increased, 
  and 
  the 
  forces 
  X 
  and 
  Z 
  and 
  the 
  moment 
  

   M 
  have 
  also 
  been 
  proportionally 
  increased. 
  

  

  We 
  may, 
  however, 
  use 
  the 
  same 
  fluting 
  material 
  so 
  that 
  

   R, 
  R 
  1? 
  R 
  2 
  will 
  remain 
  constant, 
  and 
  vary 
  the 
  density 
  p. 
  

  

  3. 
  The 
  ratio 
  of 
  the 
  density 
  of 
  air 
  to 
  the 
  density 
  of 
  carbon 
  

   dioxide 
  and 
  hydrogen 
  for 
  minimum 
  disturbance. 
  — 
  In 
  order 
  to 
  

   determine 
  this 
  ratio, 
  it 
  is 
  quite 
  essential 
  that 
  not 
  only 
  the 
  

   fluting 
  material 
  be 
  exactly 
  the 
  same 
  for 
  the 
  two 
  gases, 
  but 
  

   also 
  that" 
  the 
  stream-velocity 
  W 
  be 
  the 
  same. 
  This 
  was 
  

   accomplished 
  by 
  constructing 
  a 
  double-tube 
  Kundt 
  apparatus, 
  

   one 
  tube 
  at 
  each 
  end 
  of 
  the 
  vibrating 
  brass 
  bar, 
  arranged 
  

   with 
  manometers 
  and 
  drying 
  trains, 
  and 
  so 
  placed 
  that 
  the 
  

   tubes 
  were 
  parallel 
  and 
  close 
  to 
  each 
  other. 
  One 
  of 
  these 
  

   was 
  filled 
  with 
  air 
  ; 
  the 
  other 
  with 
  the 
  gas 
  to 
  be 
  compared. 
  

   The 
  pressure 
  was 
  then 
  adjusted 
  for 
  minimum 
  disturbance, 
  

   i. 
  e. 
  the 
  pressure 
  at 
  which 
  the 
  fluting 
  material 
  could 
  just 
  

   be 
  made 
  to 
  form 
  stripe. 
  The 
  manometers 
  were 
  then 
  read 
  and 
  

   the 
  observation 
  repeated 
  with 
  gases 
  interchanged. 
  

  

  The 
  results 
  obtained 
  for 
  different 
  fluting 
  material 
  with 
  air 
  

   and 
  carbon 
  dioxide 
  are 
  o-iven 
  in 
  the 
  following 
  table 
  : 
  — 
  

  

  Table 
  I. 
  

  

  Substance. 
  

  

  Magnesium 
  

   carbonate. 
  

  

  Amorphous 
  

  

  silica. 
  

  

  Aluminium 
  

   filings. 
  

  

  Lycopodiuui 
  

  

  Anthracene 
  

  

  Sand 
  

  

  T. 
  

  

  N. 
  

  

  Pi. 
  

  

  P 
  a 
  . 
  

  

  o 
  

  

  21 
  

  

  18 
  

  

  9 
  

   20 
  

  

  97-1 
  

   124-6 
  

  

  21-7 
  

  

  52-8 
  

  

  19 
  

   18 
  

  

  8 
  

   11 
  

  

  336-8 
  

   340-5 
  

  

  137-5 
  

   142-2 
  

  

  20 
  

  

  22 
  

  

  10 
  

   10 
  

  

  400-2 
  

   3350 
  

  

  180-5 
  

   140-0 
  

  

  21 
  

  

  10 
  

  

  223-3 
  

  

  1147 
  

  

  17 
  

  

  10 
  

  

  2139 
  

  

  117-5 
  

  

  20 
  

   21 
  

  

  10 
  

   10 
  

  

  641-0 
  

   6273 
  

  

  343-5 
  

   337-3 
  

  

  i 
  

  

  •0001258 
  

   •0001982 
  

  

  •0005376 
  

   •0005415 
  

  

  •0006360 
  

   •000533 
  

  

  •0008552 
  

  

  •0003101 
  

  

  •0010200 
  

   •0009980 
  

  

  P:r 
  

  

  •0000514 
  

   •0001278 
  

  

  •0003335 
  

   •0003438 
  

  

  •000434 
  

   •000338 
  

  

  •000275 
  

  

  •0002840 
  

  

  •0008360 
  

   •0008153 
  

  

  Po/Pl- 
  

  

  •42 
  

  

  •68 
  

   •64 
  

  

  •77 
  

  

  •83 
  

  

  T 
  equals 
  the 
  temperature 
  ; 
  N, 
  the 
  number 
  of 
  determinations 
  in 
  each 
  

   experiment; 
  P 
  a 
  , 
  P 
  2 
  , 
  p„ 
  p 
  2 
  , 
  equal 
  the 
  respective 
  pressures 
  and 
  densities 
  of 
  

   air 
  and 
  carbon 
  dioxide 
  for 
  minimum 
  disturbance. 
  

  

  It 
  will 
  be 
  seen 
  by 
  the 
  last 
  column 
  that 
  the 
  ratio 
  of 
  the 
  

   density 
  of 
  carbon 
  dioxide 
  to 
  air 
  is 
  always 
  less 
  than 
  unity. 
  

   The 
  determination 
  of 
  the 
  ratio 
  of 
  air 
  to 
  hydrogen 
  required 
  

   great 
  precaution 
  as 
  the 
  slightest 
  admixture 
  of 
  air 
  would 
  

   vitiate 
  the 
  results. 
  With 
  the 
  apparatus 
  used 
  the 
  minimum 
  

   disturbance 
  was 
  obtained 
  at 
  a 
  pressure 
  for 
  hydrogen 
  -of 
  

   1()94 
  mm. 
  of 
  mercury, 
  and 
  for 
  air 
  at 
  a 
  pressure 
  of 
  20 
  mm. 
  

   of 
  mercury. 
  The 
  corresponding 
  densities 
  were 
  '0001868 
  and 
  

  

  