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  VII. 
  — 
  On 
  the 
  Mechanical 
  Action 
  of 
  Heat, 
  especially 
  in 
  Gases 
  and 
  Vapours. 
  By 
  

   William 
  John 
  Macquorn 
  Rankine, 
  Civil 
  Engineer, 
  F.R.S.E., 
  F.R.S.S.A., 
  &c. 
  

  

  (Read 
  4th 
  February 
  1850.) 
  

   INTRODUCTION. 
  

  

  SUMMARY 
  OF 
  THE 
  PRINCIPLES 
  OP 
  THE 
  HYPOTHESIS 
  OF 
  MOLECULAR 
  VORTICES, 
  AND 
  ITS 
  APPLICA- 
  

   TION 
  TO 
  THE 
  THEORY 
  OF 
  TEMPERATURE, 
  ELASTICITY, 
  AND 
  REAL 
  SPECIFIC 
  HEAT. 
  

  

  The 
  ensuing 
  paper 
  forms 
  part 
  of 
  a 
  series 
  of 
  researches 
  respecting 
  the 
  conse- 
  

   quences 
  of 
  an 
  hypothesis 
  called 
  that 
  of 
  Molecular 
  Vortices, 
  the 
  object 
  of 
  which 
  is, 
  

   to 
  deduce 
  the 
  laws 
  of 
  elasticity, 
  and 
  of 
  heat 
  as 
  connected 
  with 
  elasticity, 
  by 
  means 
  

   of 
  the 
  principles 
  of 
  mechanics, 
  from 
  a 
  physical 
  supposition 
  consistent 
  and 
  con- 
  

   nected 
  with 
  the 
  theory 
  which 
  deduces 
  the 
  laws 
  of 
  radiant 
  light 
  and 
  heat 
  from 
  

   the 
  hypothesis 
  of 
  undulations. 
  Those 
  researches 
  were 
  commenced 
  in 
  1842, 
  and 
  

   after 
  having 
  been 
  laid 
  aside 
  for 
  nearly 
  seven 
  years, 
  from 
  the 
  want 
  of 
  experimental 
  

   data, 
  were 
  resumed 
  in 
  consequence 
  of 
  the 
  appearance 
  of 
  the 
  experiments 
  of 
  M. 
  

   Regnault 
  on 
  gases 
  and 
  vapours. 
  

  

  The 
  investigation 
  which 
  I 
  have 
  now 
  to 
  describe, 
  relates 
  to 
  the 
  mutual 
  con- 
  

   version 
  of 
  heat 
  and 
  mechanical 
  power 
  by 
  means 
  of 
  the 
  expansion 
  and 
  contraction 
  

   of 
  gases 
  and 
  vapours. 
  

  

  In 
  the 
  introduction 
  which 
  I 
  here 
  prefix 
  to 
  it, 
  I 
  purpose 
  to 
  give 
  such 
  a 
  sum- 
  

   mary 
  of 
  the 
  principles 
  of 
  the 
  hypothesis 
  as 
  is 
  necessary 
  to 
  render 
  the 
  subsequent 
  

   investigation 
  intelligible. 
  

  

  The 
  fundamental 
  suppositions 
  are 
  the 
  following 
  : 
  — 
  

  

  First, 
  — 
  That 
  each 
  atom 
  of 
  matter 
  consists 
  of 
  a 
  nucleus, 
  or 
  central 
  physical 
  

   point, 
  enveloped 
  by 
  an 
  elastic 
  atmosphere, 
  which 
  is 
  retained 
  in 
  its 
  position 
  by 
  forces 
  

   attractive 
  towards 
  the 
  nucleus 
  or 
  centre. 
  

  

  Suppositions 
  similar 
  to 
  this 
  have 
  been 
  brought 
  forward 
  by 
  Franklin, 
  tEpi- 
  

   nus, 
  Mossotti, 
  and 
  others. 
  They 
  have 
  in 
  general, 
  however, 
  conceived 
  the 
  atmo- 
  

   sphere 
  of 
  each 
  nucleus 
  to 
  be 
  of 
  variable 
  mass. 
  I 
  have 
  treated 
  it, 
  on 
  the 
  contrary, 
  

   as 
  an 
  essential 
  part 
  of 
  the 
  atom. 
  I 
  have 
  left 
  the 
  question 
  indeterminate, 
  whether 
  

   the 
  nucleus 
  is 
  a 
  small 
  body 
  of 
  a 
  character 
  distinct 
  from 
  that 
  of 
  the 
  atmosphere, 
  

   or 
  merely 
  a 
  portion 
  of 
  the 
  atmosphere 
  in 
  a 
  highly 
  condensed 
  state, 
  owing 
  to 
  the 
  

   mutual 
  attraction 
  of 
  its 
  parts. 
  

  

  According 
  to 
  this 
  first 
  supposition, 
  the 
  boundary 
  between 
  two 
  contiguous 
  

   atoms 
  of 
  a 
  body 
  is 
  an 
  imaginary 
  surface 
  at 
  which 
  the 
  attractions 
  of 
  all 
  the 
  atomic 
  

  

  VOL. 
  XX. 
  PART 
  I. 
  2 
  R 
  

  

  