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  XL. 
  — 
  On 
  the 
  Mechanical 
  Action 
  of 
  Heat. 
  By 
  William 
  John 
  Macquorn 
  Rankine, 
  

   Civil 
  Engineer, 
  F.R.S.E., 
  F.R.S.S.A., 
  &c. 
  

  

  (Read 
  January 
  17, 
  1853.) 
  

  

  Section 
  VI. 
  — 
  A 
  Review 
  of 
  the 
  Fundamental 
  Principles 
  of 
  the 
  Mechanical 
  

   Theory 
  of 
  Heat 
  ; 
  with 
  Remarks 
  on 
  the 
  Thermic 
  Phenomena 
  of 
  Currents 
  

   of 
  Elastic 
  Fluids, 
  as 
  illustrating 
  those 
  Principles. 
  

  

  (Article 
  46.) 
  I 
  have 
  been 
  induced 
  to 
  write 
  this 
  Section, 
  in 
  continuation 
  of 
  a 
  

   paper 
  on 
  the 
  Mechanical 
  Action 
  of 
  Heat, 
  by 
  the 
  publication 
  (in 
  the 
  Philosophical 
  

   Magazine 
  for 
  December 
  1852, 
  Supplementary 
  Number) 
  of 
  a 
  series 
  of 
  experiments 
  

   by 
  Mr 
  Joule 
  and 
  Professor 
  William 
  Thomson, 
  on 
  the 
  Thermal 
  Effects 
  expe- 
  

   rienced 
  by 
  Air 
  in 
  rushing 
  through 
  small 
  Apertures. 
  Although 
  those 
  authors 
  

   express 
  an 
  intention 
  to 
  continue 
  the 
  experiments 
  on 
  a 
  large 
  scale, 
  so 
  as 
  to 
  obtain 
  

   more 
  precise 
  results 
  ; 
  yet 
  the 
  results 
  already 
  obtained 
  are 
  sufficient 
  to 
  constitute 
  

   the 
  first 
  step 
  towards 
  the 
  experimental 
  determination 
  of 
  that 
  most 
  important 
  

   function 
  in 
  the 
  theory 
  of 
  the 
  mechanical 
  action 
  of 
  heat, 
  which 
  has 
  received 
  the 
  

   name 
  of 
  Carnot's 
  Function. 
  

  

  By 
  the 
  theoretical 
  investigations 
  of 
  Messrs 
  Clausius 
  and 
  Thomson, 
  — 
  which 
  are 
  

   based 
  simply 
  on 
  the 
  fact 
  of 
  the 
  convertibility 
  of 
  heat 
  and 
  mechanical 
  power, 
  

   the 
  determination 
  of 
  their 
  relative 
  value 
  by 
  Mr 
  Joule, 
  and 
  the 
  properties 
  of 
  the 
  

   function 
  called 
  temperature, 
  without 
  any 
  definite 
  supposition 
  as 
  to 
  the 
  nature 
  of 
  

   heat, 
  — 
  Carnot's 
  function 
  is 
  left 
  wholly 
  indeterminate. 
  

  

  By 
  the 
  investigations 
  contained 
  in 
  the 
  previous 
  sections 
  of 
  this 
  paper, 
  and 
  in 
  

   a 
  paper 
  on 
  the 
  Centrifugal 
  Theory 
  of 
  Elasticity, 
  — 
  in 
  which 
  the 
  supposition 
  is 
  made, 
  

   that 
  heat 
  consists 
  in 
  the 
  revolutions 
  of 
  what 
  are 
  called 
  Molecular 
  Vortices, 
  so 
  

   that 
  the 
  elasticity 
  arising 
  from 
  heat 
  is 
  in 
  fact 
  centrifugal 
  force, 
  — 
  a 
  form 
  is 
  assigned 
  

   to 
  Carnot's 
  function 
  ; 
  but 
  its 
  numerical 
  values 
  are 
  left 
  to 
  be 
  ascertained 
  by 
  expe- 
  

   riment. 
  

  

  The 
  recent 
  experiments 
  of 
  Messrs 
  Joule 
  and 
  Thomson 
  serve 
  (so 
  far 
  as 
  the 
  

   degree 
  of 
  precision 
  of 
  their 
  results 
  permits) 
  at 
  once 
  to 
  determine 
  numerical 
  values 
  

   of 
  Carnot's 
  function 
  for 
  use 
  in 
  practice, 
  and 
  to 
  test 
  the 
  accuracy 
  with 
  which 
  

   the 
  phenomena 
  of 
  heat 
  are 
  represented 
  by 
  the 
  consequences 
  of 
  the 
  hypothesis 
  

   of 
  molecular 
  vortices, 
  from 
  which 
  the 
  investigation 
  in 
  this 
  paper 
  sets 
  out. 
  

   vol. 
  xx. 
  part 
  iv. 
  7 
  o 
  

  

  