﻿DYNAMICAL 
  THEORY 
  OF 
  HEAT. 
  

  

  279 
  

  

  39. 
  Supplementary 
  Table 
  of 
  the 
  Motive 
  Powers 
  of 
  Heat. 
  

  

  Range 
  of 
  Temperatures. 
  

  

  III. 
  

  

  Duty 
  of 
  a 
  Unit 
  

   of 
  Heat 
  through 
  

   the 
  whole 
  range. 
  

  

  IV. 
  

  

  Duty 
  of 
  a 
  

   Unit 
  of 
  

  

  Heat 
  sup- 
  

   plied 
  from 
  

   the 
  source. 
  

  

  V. 
  

  

  Quantity 
  

   of 
  Heat 
  

  

  converted 
  

   into 
  mecha- 
  

   nical 
  effect. 
  

  

  VI. 
  

  

  Quantity 
  

   of 
  Heat 
  

   wasted. 
  

  

  I. 
  

  

  II. 
  

  

  S 
  

  

  1011 
  

  

  105-8 
  

  

  300 
  

  

  400 
  

  

  500 
  

  

  600 
  

  

  T 
  

  

  O 
  

  

  

   

   

   

   

   

   

  

  s 
  

  

  140 
  

  

  230 
  

  

  300 
  , 
  

  

  400 
  

  

  500 
  

  

  600 
  

  

  T 
  

  

  O 
  

  

  30 
  

  

  100 
  

   

   

   

   

   

  

  rt.-ibs. 
  

   439-9 
  

   446-2 
  

  

  1099 
  

  

  1395 
  

  

  1690 
  

  

  1980 
  

  

  w 
  

  

  Pt.-lbs. 
  

  

  377 
  

   382 
  

   757 
  

   879 
  

   979 
  

   1059 
  

   1390 
  

  

  1 
  - 
  ft 
  

  

  •271 
  

   •275 
  

   •545 
  

   •632 
  

   •704 
  

   •762 
  

   1-000 
  

  

  R 
  

  

  •729 
  

   •725 
  

   •455 
  

   •368 
  

   •296 
  

   •238 
  

   •000 
  

  

  40. 
  Taking 
  the 
  range 
  30 
  J 
  to 
  140° 
  as 
  an 
  example 
  suitable 
  to 
  the 
  circumstances 
  

   of 
  some 
  of 
  the 
  best 
  steam-engines 
  that 
  have 
  yet 
  been 
  made 
  (See 
  Appendix 
  to 
  

   Account 
  of 
  Carnot's 
  Theory, 
  sec. 
  v.), 
  we 
  find 
  in 
  Col. 
  III. 
  of 
  the 
  supplementary 
  

   Table, 
  377 
  ft.-lbs. 
  as 
  the 
  corresponding 
  duty 
  of 
  a 
  unit 
  of 
  heat 
  instead 
  of 
  440, 
  

   shewn 
  in 
  Col. 
  III., 
  which 
  is 
  Carnot's 
  theoretical 
  duty. 
  We 
  conclude 
  that 
  the 
  

   recorded 
  performance 
  of 
  the 
  Fowey-Consols 
  engine 
  in 
  1845, 
  instead 
  of 
  being 
  only 
  

   57^ 
  per 
  cent, 
  amounted 
  really 
  to 
  67 
  per 
  cent., 
  or 
  § 
  of 
  the 
  duty 
  of 
  a 
  perfect 
  engine 
  

   with 
  the 
  same 
  range 
  of 
  temperature 
  ; 
  and 
  this 
  duty 
  being 
  *271 
  (rather 
  more 
  than 
  

   \) 
  of 
  the 
  whole 
  equivalent 
  of 
  the 
  heat 
  used 
  ; 
  we 
  conclude 
  farther, 
  that 
  ^ 
  9 
  , 
  or 
  18 
  

   per 
  cent, 
  of 
  the 
  whole 
  heat 
  supplied, 
  was 
  actually 
  converted 
  into 
  mechanical 
  

   effect 
  by 
  that 
  steam-engine. 
  

  

  41. 
  The 
  numbers 
  in 
  the 
  lower 
  part 
  of 
  the 
  supplementary 
  Table 
  shew 
  the 
  great 
  

   advantage 
  that 
  may 
  be 
  anticipated 
  from 
  the 
  perfecting 
  of 
  the 
  air-engine, 
  or 
  any 
  

   other 
  kind 
  of 
  thermodjmamic 
  engine 
  in 
  which 
  the 
  range 
  of 
  the 
  temperature 
  can 
  

   be 
  increased 
  much 
  beyond 
  the 
  limits 
  actually 
  attainable 
  in 
  steam-engines. 
  Thus 
  

   an 
  air-engine, 
  with 
  its 
  hot 
  part 
  at 
  600°, 
  and 
  its 
  cold 
  part 
  at 
  0° 
  cent., 
  working 
  with 
  

   perfect 
  economy, 
  would 
  convert 
  76 
  per 
  cent, 
  of 
  the 
  whole 
  heat 
  used 
  into 
  mechani- 
  

   cal 
  effect 
  ; 
  or 
  working 
  with 
  such 
  economy 
  as 
  has 
  been 
  estimated 
  for 
  the 
  Fowey- 
  

   Consols 
  engine, 
  that 
  is, 
  producing 
  67 
  per 
  cent, 
  of 
  the 
  theoretical 
  duty 
  correspond- 
  

   ing 
  to 
  its 
  range 
  of 
  temperature, 
  would 
  convert 
  51 
  per 
  cent, 
  of 
  all 
  the 
  heat 
  used 
  

   into 
  mechanical 
  effect. 
  

  

  42. 
  It 
  was 
  suggested 
  to 
  me 
  by 
  Mr 
  Joule, 
  in 
  a 
  letter 
  dated 
  December 
  9, 
  1848, 
  

  

  