﻿R. 
  de 
  Saussure 
  — 
  Graphical 
  Thermodynamics. 
  2T 
  

  

  fda 
  = 
  (J-) 
  (Inadd) 
  

  

  f 
  

   Let 
  - 
  — 
  = 
  (f 
  m 
  . 
  Since 
  Ina 
  is 
  equal 
  to 
  the 
  length 
  of 
  the 
  circum- 
  

   ference, 
  <p 
  m 
  represents 
  geometrically 
  the 
  value 
  of 
  the 
  centri- 
  

   petal 
  force 
  referred 
  to 
  the 
  unit 
  of 
  length, 
  i. 
  e., 
  a 
  pressure, 
  of 
  

   so 
  many 
  pounds 
  per 
  foot, 
  supposed 
  to 
  be 
  acting 
  on 
  the 
  circum- 
  

   ference 
  of 
  the 
  circle. 
  

  

  Let 
  2zada 
  — 
  ds 
  or 
  7za~= 
  s. 
  Then 
  s 
  is 
  the 
  area 
  of 
  the 
  circle. 
  

  

  According 
  to 
  these 
  definitions 
  : 
  

  

  2 
  fda 
  = 
  2(p 
  m 
  ds 
  

  

  f 
  

   If 
  now 
  in 
  the 
  equation 
  <p 
  m 
  = 
  -^— 
  f 
  be 
  replaced 
  by 
  its 
  value 
  

  

  as 
  given 
  in 
  equation 
  (3), 
  the 
  result 
  is 
  : 
  

  

  9m 
  = 
  — 
  •— 
  

  

  and 
  since 
  2m 
  — 
  1 
  : 
  

  

  

  Whence 
  : 
  

  

  2fda 
  — 
  2(ep 
  in 
  ds) 
  ={2cp 
  m 
  )ds 
  = 
  cpds 
  

   With 
  : 
  

  

  m 
  = 
  — 
  and 
  s 
  = 
  7ta 
  

  

  ^ 
  i 
  2 
  

  

  The 
  last 
  two 
  equations 
  are 
  precisely 
  the 
  ones 
  by 
  which 
  <p 
  and 
  

   s 
  have 
  been 
  first 
  defined. 
  

  

  Since 
  tp 
  = 
  <p 
  m 
  when 
  m 
  = 
  1, 
  and 
  since 
  <p 
  m 
  is 
  the 
  pressure 
  sup- 
  

   posed 
  to 
  be 
  acting 
  on 
  the 
  circumference 
  of 
  the 
  circle 
  corre- 
  

   sponding 
  to 
  the 
  particle 
  of 
  mass 
  m, 
  we 
  can 
  define 
  the 
  physical 
  

   nature 
  of 
  <p 
  and 
  s 
  as 
  follows 
  : 
  If 
  the 
  unit 
  of 
  mass 
  of 
  a 
  sub- 
  

   stance 
  be 
  represented 
  geometrically 
  or 
  symbolically 
  by 
  a 
  circle, 
  

   the 
  physical 
  state 
  of 
  said 
  substance 
  can 
  be 
  completely 
  defined 
  

   by 
  the 
  area 
  s 
  of 
  the 
  circle 
  and 
  by 
  a 
  pressure 
  <p, 
  supposed 
  to 
  be 
  

   acting 
  on 
  the 
  circumference 
  of 
  the 
  circle. 
  The 
  two 
  data, 
  thus 
  

   defining 
  the 
  state 
  of 
  the 
  substance, 
  are 
  precisely 
  the 
  coordi- 
  

   nates 
  <p 
  and 
  s, 
  which 
  determine 
  the 
  position 
  of 
  the 
  point 
  repre- 
  

   senting 
  this 
  state. 
  For 
  this 
  reason, 
  the 
  abscissa 
  s 
  shall 
  be 
  

   called 
  the 
  " 
  symbolical 
  volume" 
  and 
  the 
  ordinate 
  <p 
  the 
  " 
  sym- 
  

   bolical 
  pressure 
  " 
  of 
  the 
  substance. 
  

  

  As 
  the 
  considerations 
  developed 
  in 
  this 
  paragraph 
  are 
  some- 
  

   what 
  abstract, 
  it 
  must 
  not 
  be 
  forgotten 
  that 
  the 
  graphical 
  

   method, 
  which 
  is 
  the 
  object 
  of 
  this 
  study 
  is 
  quite 
  independent 
  

   of 
  these 
  theoretical 
  considerations, 
  since 
  the 
  two 
  variables 
  <p 
  

  

  