﻿298 
  ON 
  THE 
  HEAT 
  PRODUCED 
  BY 
  THE 
  COMPRESSION 
  OF 
  A 
  GAS. 
  

  

  In 
  the 
  second 
  member 
  of 
  this 
  equation 
  p' 
  denotes 
  the 
  pressure 
  of 
  the 
  air 
  

   through 
  the 
  second 
  spiral, 
  which 
  would 
  be 
  the 
  atmospheric 
  pressure, 
  or 
  exces- 
  

   sively 
  near 
  it, 
  if, 
  as 
  in 
  Joule's 
  third 
  experiment, 
  mentioned 
  above 
  (described 
  by 
  

   the 
  author 
  in 
  p. 
  378 
  of 
  the 
  volume* 
  containing 
  his 
  paper), 
  the 
  air 
  leaving 
  the 
  

   second 
  spiral 
  be 
  measured 
  by 
  means 
  of 
  a 
  pneumatic 
  trough 
  : 
  p 
  denotes 
  the 
  pres- 
  

   sure 
  in 
  the 
  first 
  spiral, 
  which 
  ought 
  to 
  be 
  constant, 
  and 
  must 
  be 
  carefully 
  mea- 
  

   sured 
  ; 
  u 
  denotes 
  the 
  volume 
  of 
  air 
  which 
  leaves 
  the 
  apparatus 
  in 
  aiiy 
  time 
  ; 
  

   and 
  H 
  denotes 
  the 
  quantity 
  of 
  heat 
  emitted 
  in 
  the 
  same 
  time. 
  The 
  experiment 
  

   might 
  be 
  continued 
  for 
  any 
  length 
  of 
  time, 
  and 
  each 
  one 
  of 
  these 
  four 
  quantities 
  

   might 
  be 
  determined 
  with 
  great 
  accuracy, 
  so 
  that 
  probably 
  very 
  accurate 
  direct 
  

   results 
  of 
  observations 
  might 
  be 
  obtained. 
  If 
  so, 
  no 
  way 
  of 
  experimenting 
  could 
  

   be 
  better 
  adapted 
  than 
  this 
  to 
  the 
  determination 
  of 
  Carnot's 
  function, 
  for 
  differ- 
  

   ent 
  temperatures, 
  in 
  terms 
  of 
  Joule's 
  mechanical 
  equivalent 
  of 
  heat. 
  

  

  * 
  Phil. 
  Mag., 
  vol. 
  xxvi. 
  

  

  