Page:Reflections on the Motive Power of Heat.djvu/202

178 enable us to calculate, from the data supplied by Regnault, the abscissa and ordinate for each of the curves described above (§ 17) corresponding to any assumed temperature t. After the explanations of §§ 33, 34, 35, 36, it is only necessary to add that c is a quantity of which the value is very nearly unity, and would be exactly so were the capacity of water for heat the same at every temperature as it is between 0° and 1°; and that the value of c(S - t), for any assigned values of S and t, is found, by subtracting the number corresponding to t from the number corresponding to s, in the column headed "Nombre des unités de chaleur abandonneés par un kilogramme d'eau en descendant de T° à 0°," of the last table (at the end of the tenth memoir) of Regnault's work. By giving S the value 230°, and by substituting successively 220, 210, 200, etc., for t, values for x, y, x', y', have been found, which are exhibited in the table opposite.