﻿374 
  Mr. 
  R. 
  A. 
  Lehfeldt 
  on 
  a 
  Numerical 
  Evaluation 
  of 
  

  

  in 
  evaluating 
  e 
  in 
  this 
  way 
  we 
  have 
  to 
  remember 
  that 
  it 
  is 
  

   to 
  be 
  expressed 
  per 
  1013000 
  dynes 
  per 
  sq. 
  cm., 
  and 
  that 
  

   the 
  unit 
  of 
  density 
  (p) 
  is 
  the 
  density 
  at 
  the 
  freezing-point 
  and 
  

   one 
  atmospheric 
  pressure, 
  and 
  consequently 
  for 
  air 
  773'3 
  

   times, 
  and 
  for 
  carbon 
  dioxide 
  508 
  "9 
  times 
  less 
  than 
  unity 
  

   on 
  the 
  C.G.S. 
  system. 
  

  

  The 
  value 
  of 
  8/3/8p 
  is 
  not 
  known 
  for 
  hydrogen 
  or 
  nitrogen: 
  

   for 
  air 
  we 
  have 
  

  

  273 
  x 
  1013000 
  x 
  0-0000115 
  x 
  773*3 
  

  

  _ 
  no. 
  

  

  1-163 
  xyyaoooo 
  

  

  221 
  per 
  at 
  mo. 
  

  

  This, 
  which 
  represents 
  the 
  mean 
  value 
  of 
  the 
  range 
  0° 
  to 
  100°, 
  

   is 
  in 
  good 
  agreement 
  with 
  the 
  number 
  found 
  experimentally 
  

   (0°-200). 
  For 
  carbon 
  dioxide 
  

  

  

  273 
  x 
  1013000 
  x 
  0-0000512 
  8 
  x 
  50 
  8-9 
  

   1-3 
  63 
  x 
  8520000 
  

  

  = 
  o, 
  728 
  per 
  atmo. 
  

  

  This, 
  it 
  will 
  be 
  noticed, 
  is 
  much 
  less 
  than 
  the 
  number 
  derived 
  

   from 
  Joule 
  and 
  Thomson's 
  measurements, 
  whether 
  by 
  their 
  

   own 
  reduction 
  or 
  by 
  mine 
  ; 
  and 
  if 
  Regnault's 
  value 
  of 
  8fi/8p 
  

   be 
  used 
  the 
  result 
  will 
  be 
  10 
  per 
  cent, 
  smaller 
  still. 
  This 
  

   discrepancy 
  wants 
  clearing 
  up. 
  

  

  Results 
  : 
  — 
  (i.) 
  Value 
  of 
  T 
  . 
  

  

  For 
  the 
  first 
  part 
  of 
  the 
  problem, 
  that 
  of 
  determining 
  

   the 
  absolute 
  temperature 
  of 
  the 
  freezing-point, 
  we 
  require 
  to 
  

   know 
  the 
  mean 
  value 
  of 
  (1 
  — 
  K 
  P 
  e/v) 
  over 
  the 
  range 
  0° 
  to 
  

   100° 
  for 
  such 
  densities 
  as 
  have 
  actually 
  been 
  used 
  in 
  the 
  

   gas-thermometers. 
  These 
  values 
  are 
  shown 
  in 
  the 
  following 
  

   table 
  : 
  — 
  

  

  1 
  

  

  Pressure 
  of 
  the 
  

  

  gas 
  at 
  0°. 
  

  

  1 
  — 
  Kpe/fl. 
  

  

  Remarks. 
  

  

  Air 
  

  

  mm, 
  

   1000 
  

  

  760 
  

  

  995 
  

  

  995 
  

  

  995 
  

  

  09993 
  

   1-0025 
  

   1-0034 
  

   10203 
  

  

  1-0160 
  j 
  

  

  1 
  

  

  e 
  according 
  to 
  J. 
  and 
  T. 
  

   Ditto. 
  

  

  e 
  assumed 
  to 
  be 
  the 
  same 
  

  

  as 
  for 
  air. 
  

   e 
  from 
  curve 
  of 
  J. 
  and 
  T.'s 
  

  

  measurements, 
  

   e 
  from 
  dj3/8p 
  (Chappuis). 
  

  

  Nitrogen 
  

  

  Carbon 
  dioxide 
  . 
  . 
  . 
  

   Carbon 
  dioxide 
  . 
  . 
  . 
  

  

  