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  PROFESSOR 
  WILLIAM 
  THOMSON 
  ON 
  THE 
  

  

  derives 
  more 
  mechanical 
  effect 
  from 
  the 
  same 
  quantity 
  of 
  heat, 
  drawn 
  from 
  the 
  

   source, 
  than 
  B, 
  is 
  false. 
  Hence 
  no 
  engine 
  whatever, 
  with 
  source 
  and 
  refrigerator 
  

   at 
  the 
  same 
  temperatures, 
  can 
  get 
  more 
  work 
  from 
  a 
  given 
  quantity 
  of 
  heat 
  intro- 
  

   duced 
  than 
  any 
  engine 
  which 
  satisfies 
  the 
  condition 
  of 
  reversibility, 
  which 
  was 
  to 
  

   be 
  proved. 
  

  

  14. 
  This 
  proposition 
  was 
  first 
  enunciated 
  by 
  Carnot, 
  being 
  the 
  expression 
  of 
  

   his 
  criterion 
  of 
  a 
  perfect 
  thermo-dynamic 
  engine.* 
  He 
  proved 
  it 
  by 
  demonstrat- 
  

   ing 
  that 
  a 
  negation 
  of 
  it 
  would 
  require 
  the 
  admission 
  that 
  there 
  might 
  be 
  a 
  self- 
  

   acting 
  machine 
  constructed 
  which 
  would 
  produce 
  mechanical 
  effect 
  indefinitely, 
  

   without 
  any 
  source 
  either 
  in 
  heat 
  or 
  the 
  consumption 
  of 
  materials, 
  or 
  any 
  other 
  

   physical 
  agency 
  ; 
  but 
  this 
  demonstration 
  involves, 
  fundamentally, 
  the 
  assumption 
  

   that, 
  in 
  "a 
  complete 
  cycle 
  of 
  operations," 
  the 
  medium 
  parts 
  with 
  exactly 
  the 
  

   same 
  quantity 
  of 
  heat 
  as 
  it 
  receives. 
  A 
  very 
  strong 
  expression 
  of 
  doubt 
  regard- 
  

   ing 
  the 
  truth 
  of 
  this 
  assumption, 
  as 
  a 
  universal 
  principle, 
  is 
  given 
  by 
  Carnot 
  

   himself;! 
  and 
  that 
  it 
  is 
  false, 
  where 
  mechanical 
  work 
  is, 
  on 
  the 
  whole, 
  either 
  

   gained 
  or 
  spent 
  in 
  the 
  operations, 
  may 
  (as 
  I 
  have 
  tried 
  to 
  shew 
  above) 
  be 
  considered 
  

   to 
  be 
  perfectly 
  certain. 
  It 
  must, 
  then, 
  be 
  admitted 
  that 
  Carnot's 
  original 
  demon- 
  

   stration 
  utterly 
  fails, 
  but 
  we 
  cannot 
  infer 
  that 
  the 
  proposition 
  concluded 
  is 
  false. 
  

   The 
  truth 
  of 
  the 
  conclusion 
  appeared 
  to 
  me, 
  indeed, 
  so 
  probable, 
  that 
  I 
  took 
  it 
  in 
  

   connection 
  with 
  Joule's 
  principle, 
  on 
  account 
  of 
  which 
  Carnot's 
  demonstration 
  

   of 
  it 
  fails, 
  as 
  the 
  foundation 
  of 
  an 
  investigation 
  of 
  the 
  motive 
  power 
  of 
  heat 
  in 
  

   air-engines 
  or 
  steam-engines 
  through 
  finite 
  ranges 
  of 
  temperature, 
  and 
  obtained, 
  

   about 
  a 
  year 
  ago, 
  results, 
  of 
  which 
  the 
  substance 
  is 
  given 
  in 
  the 
  second 
  part 
  of 
  

   the 
  paper 
  at 
  present 
  communicated 
  to 
  the 
  Royal 
  Society. 
  It 
  was 
  not 
  until 
  the 
  

   commencement 
  of 
  the 
  present 
  year 
  that 
  I 
  found 
  the 
  demonstration 
  given 
  above, 
  

   by 
  which 
  the 
  truth 
  of 
  the 
  proposition 
  is 
  established 
  upon 
  an 
  axiom 
  ($12) 
  which 
  

   I 
  think 
  will 
  be 
  generally 
  admitted. 
  It 
  is 
  with 
  no 
  wish 
  to 
  claim 
  priority 
  that 
  I 
  

   make 
  these 
  statements, 
  as 
  the 
  merit 
  of 
  first 
  establishing 
  the 
  proposition 
  upon 
  

   correct 
  principles 
  is 
  entirely 
  due 
  to 
  Clausius, 
  who 
  published 
  his 
  demonstration 
  

   of 
  it 
  in 
  the 
  month 
  of 
  May 
  last 
  year, 
  in 
  the 
  second 
  part 
  of 
  his 
  paper 
  on 
  the 
  Motive 
  

   Power 
  of 
  Heat-t 
  I 
  may 
  be 
  allowed 
  to 
  add, 
  that 
  I 
  have 
  given 
  the 
  demonstration 
  

   exactly 
  as 
  it 
  occurred 
  to 
  me 
  before 
  I 
  knew 
  that 
  Clausius 
  had 
  either 
  enunciated 
  

   or 
  demonstrated 
  the 
  proposition. 
  The 
  following 
  is 
  the 
  axiom 
  on 
  which 
  Clausius' 
  

   demonstration 
  is 
  founded 
  : 
  — 
  

  

  It 
  is 
  impossible 
  for 
  a 
  self-acting 
  machine, 
  unaided 
  by 
  any 
  external 
  agency, 
  to 
  

   convey 
  heat 
  from 
  one 
  body 
  to 
  another 
  at 
  a 
  higher 
  temperature. 
  

  

  It 
  is 
  easily 
  shewn 
  that, 
  although 
  this 
  and 
  the 
  axiom 
  I 
  have 
  used 
  are 
  different 
  

  

  * 
  "Account 
  of 
  Carnot's 
  Theory," 
  § 
  13. 
  f 
  Il)id 
  -> 
  § 
  6 
  - 
  

  

  | 
  Poggendorff's 
  Annalen, 
  referred 
  to 
  above. 
  

  

  