﻿152 
  MR 
  W. 
  J. 
  M. 
  RANKINE 
  ON 
  THE 
  

  

  Then 
  for 
  all 
  substances 
  

  

  r°"'".^T 
  +i 
  ) 
  

  

  and 
  in 
  perfect 
  gases 
  \ 
  (IX.) 
  

  

  p-JL 
  JL 
  

  

  »M 
  

  

  t 
  may 
  be 
  termed 
  absolute 
  temperature, 
  and 
  the 
  point 
  from 
  which 
  it 
  is 
  

   measured, 
  the 
  absolute 
  zero 
  of 
  temperature. 
  This, 
  as 
  I 
  have 
  observed, 
  is 
  an 
  ima- 
  

   ginary 
  point, 
  being 
  lower 
  than 
  the 
  absolute 
  zero 
  of 
  heat 
  by 
  the 
  quantity 
  Cnfxb, 
  

   which 
  is 
  the 
  same 
  for 
  all 
  substances. 
  

  

  The 
  value 
  of 
  C, 
  or 
  the 
  absolute 
  temperature 
  of 
  melting 
  ice, 
  as 
  determined 
  

   from 
  M. 
  Regnault's 
  experiments, 
  is 
  

  

  274°-6 
  centigrade, 
  

   being 
  the 
  reciprocal 
  of 
  

  

  0"00364166 
  per 
  centigrade 
  degree, 
  

   the 
  value 
  to 
  which 
  the 
  coefficients 
  of 
  dilatation 
  of 
  gases 
  at 
  the 
  temperature 
  of 
  

   melting 
  ice 
  approximate 
  as 
  they 
  are 
  rarefied. 
  

  

  For 
  Fahrenheit's 
  scale 
  C=494°-28. 
  

  

  In 
  the 
  sequel 
  I 
  shall 
  represent 
  temperatures 
  measured 
  from 
  that 
  of 
  melting 
  

   ice 
  by 
  

  

  T 
  = 
  r- 
  C 
  

  

  We 
  have 
  now 
  to 
  consider 
  the 
  absolute 
  quantity 
  of 
  heat, 
  or 
  of 
  molecular 
  vis 
  

   viva, 
  which 
  corresponds 
  to 
  a 
  given 
  temperature 
  in 
  a 
  given 
  substance. 
  It 
  is 
  obvious 
  

   that 
  

  

  fX 
  w 
  2 
  

  

  represents, 
  in 
  terms 
  of 
  gravity, 
  the 
  portion 
  of 
  vis 
  viva, 
  in 
  one 
  atom, 
  due 
  to 
  the 
  

   molecular 
  vortices 
  ; 
  but 
  besides 
  the 
  vortical 
  motion, 
  there 
  may 
  be 
  oscillations 
  of 
  

   expansion 
  and 
  contraction, 
  or 
  of 
  rectilinear 
  vibration 
  about 
  a 
  position 
  of 
  equili- 
  

   brium. 
  The 
  velocity 
  with 
  which 
  these 
  additional 
  motions 
  are 
  performed 
  will 
  be 
  

   in 
  a 
  permanent 
  condition, 
  when 
  the 
  mean 
  value 
  of 
  its 
  square, 
  independent 
  of 
  small 
  

   periodic 
  changes, 
  is 
  equal 
  throughout 
  the 
  atomic 
  atmosphere. 
  We 
  may 
  there- 
  

   fore 
  represent 
  by 
  

  

  fit? 
  _ 
  nn? 
  y 
  

  

  the 
  total 
  vis 
  viva 
  of 
  the 
  atomic 
  atmosphere. 
  To 
  this 
  we 
  have 
  to 
  add 
  that 
  of 
  the 
  

   nucleus, 
  raising 
  the 
  quantity 
  of 
  heat 
  in 
  one 
  atom 
  to 
  

  

  Md 
  2 
  

  

  ■w 
  =q 
  

  

  While 
  the 
  quantity 
  of 
  heat 
  in 
  unity 
  of 
  weight 
  is 
  f 
  (XI.) 
  

  

  2*~ 
  Q 
  

  

  