﻿168 
  MR 
  W. 
  J. 
  M. 
  RANKINE 
  ON 
  THE 
  

  

  Thus 
  it 
  appears, 
  that 
  for 
  the 
  simple 
  substances, 
  oxygen 
  and 
  hydrogen, 
  the 
  

   ratio 
  N 
  is 
  the 
  same, 
  while 
  for 
  atmospheric 
  air 
  it 
  is 
  somewhat 
  smaller.* 
  

  

  (12.) 
  The 
  ordinary 
  mode 
  of 
  expressing 
  the 
  specific 
  heats 
  of 
  gases 
  is 
  to 
  state 
  

   their 
  ratios 
  to 
  that 
  of 
  an 
  equal 
  volume 
  of 
  atmospheric 
  air 
  at 
  the 
  same 
  pressure 
  and 
  

   temperature. 
  

  

  When 
  - 
  is 
  a 
  very 
  small 
  fraction, 
  specific 
  heats 
  of 
  unity 
  of 
  volume 
  of 
  a 
  perfect 
  

   gas 
  are 
  given 
  by 
  the 
  equations 
  

  

  »MK 
  

  

  CN 
  

   »MK 
  P 
  =£ 
  (^ 
  + 
  lj 
  

  

  That 
  is 
  to 
  say, 
  the 
  specific 
  heat 
  of 
  unity 
  of 
  volume 
  at 
  constant 
  volume 
  is 
  

   inversely 
  proportional 
  to 
  the 
  fraction 
  by 
  which 
  the 
  ratio 
  of 
  the 
  two 
  specific 
  heats 
  

   exceeds 
  unity 
  ; 
  a 
  conclusion 
  already 
  deduced 
  from 
  experiment 
  by 
  Duloxg. 
  

  

  The 
  following 
  is 
  a 
  comparison 
  of 
  the 
  ratios 
  of 
  the 
  apparent 
  specific 
  heats 
  

   under 
  constant 
  pressure, 
  of 
  unity 
  of 
  volume 
  of 
  oxygen 
  and 
  hydrogen 
  respectively, 
  

   to 
  that 
  of 
  atmospheric 
  air, 
  as 
  deduced 
  from 
  Equation 
  (24.), 
  with 
  those 
  determined 
  

   experimentally 
  by 
  De 
  la 
  Roche 
  and 
  Berard. 
  

  

  Ratio 
  * 
  M 
  K 
  p( 
  Gas 
  ) 
  

  

  n 
  M 
  K 
  P 
  (Atmos. 
  air) 
  

  

  Gas. 
  By 
  Theory. 
  By 
  Experiment. 
  

  

  Oxygen, 
  .... 
  0-973 
  0-9765 
  

  

  Hydrogen, 
  .... 
  0973 
  0-9033 
  

  

  This 
  comparison 
  exhibits 
  a 
  much 
  more 
  close 
  agreement 
  between 
  theory 
  and 
  expe- 
  

   riment 
  than 
  has 
  been 
  hitherto 
  supposed 
  to 
  exist, 
  the 
  errors 
  in 
  the 
  constants 
  

   employed 
  having 
  had 
  the 
  effect 
  of 
  making 
  the 
  ratio 
  1 
  + 
  N 
  seem 
  greater 
  for 
  atmo- 
  

   spheric 
  air 
  than 
  for 
  oxygen 
  and 
  hydrogen, 
  while 
  in 
  fact 
  it 
  is 
  smaller. 
  

  

  To 
  treat 
  the 
  other 
  substances 
  on 
  which 
  both 
  M. 
  Duloxg 
  and 
  MM. 
  De 
  la 
  

  

  * 
  The 
  following 
  are 
  some 
  additional 
  determinations 
  of 
  the 
  value 
  of 
  y 
  for 
  atmospheric 
  air, 
  

   founded 
  upon 
  experiments 
  on 
  the 
  velocity 
  of 
  sound 
  : 
  — 
  

  

  Observers. 
  

   Bravais 
  and 
  Martins 
  : 
  mean 
  of 
  several 
  experiments 
  "J 
  

   at 
  temperatures 
  varying 
  from 
  5° 
  to 
  11° 
  centigrade, 
  > 
  

   reduced 
  to 
  0° 
  (Comptes 
  Rendus, 
  xix.) 
  . 
  . 
  J 
  

  

  Moll 
  and 
  Van 
  Beck 
  : 
  reduced 
  to 
  . 
  . 
  

  

  Stampfer 
  and 
  Myrbach 
  : 
  reduced 
  to 
  0° 
  (not 
  corrected 
  1 
  

   for 
  moisture) 
  ...... 
  J 
  

  

  Academie 
  des 
  Sciences, 
  1738: 
  (not 
  corrected 
  for 
  "I 
  „ 
  -, 
  oo-?in 
  i 
  a 
  in 
  

  

  ■ 
  . 
  \ 
  v 
  > 
  o 
  -1 
  ooY'10 
  l-41o 
  

  

  moisture) 
  ...... 
  J 
  

  

  A 
  variation 
  of 
  one 
  metre 
  per 
  second 
  in 
  the 
  velocity 
  of 
  sound 
  at 
  0° 
  corresponds 
  to 
  a 
  variation 
  of 
  

   0085 
  in 
  the 
  value 
  of 
  y. 
  

  

  T 
  

  

  Centigrade. 
  

  

  a 
  

   Metres 
  per 
  second. 
  

  

  7 
  

  

  0° 
  

  

  332-37 
  

  

  1-40955 
  

  

  0° 
  

  

  332-25 
  

  

  1-40853 
  

  

  0° 
  

  

  332-96 
  

  

  1-41456 
  

  

  