236 W. J. M. Rankine, Esq., oti a Formula /or calculating 



t is the temperature measured from the absolute zero men- 

 tioned in my paper on the Elasticity of Vapours, in the Edin- 

 burgh New Philosophical Journal for July 1849, and is found 

 by adding 274^-6 to the temperature according to the centi- 

 grade scale. 



A, B, and C, are three constants, depending on the nature 

 of the liquid, whose values for the centigrade scale, corre- 

 sponding to water, mercury, alcohol, and sulphuret of carbon, 

 are given below. 



A. Log B. Log C. 



Water, . . 0-4414907 4-8987546 1-7890286 



Mercury, . 0-0229130 5-9048766 1-3703897 



Alcohol, . . 0-2615033 4-8414452 1-2S93056 



Sulphuret of Carbon, 0-2540074 4-8483872 1-2192054 



The data from which the constants have been computed 

 have been taken from the following authorities : — for water, 

 from the experiments of Hallstrom ; for mercury, from those 

 of Regnault ; and for alcohol and sulphuret of carbon, from 

 those of Gay-Lussac. As the experiments of M. Gay-Lussac 

 give only the apparent expansion of the liquids in glass, I 

 have assumed, in order to calculate the true expansion, that 

 the dilatation of the glass used by him was -0000258 of its 

 volume for each centigrade degree. This is very nearly the 

 mean dilatation of the different kinds of glass. M. Regnault 

 has shewn that, according to the composition and treatment 

 of glass, the coefficient varies between the limits -000022 and 

 •000028. 



Annexed are given tables of comparison between the re- 

 sults of the formula and those of experiment. The data from 

 which the constants were calculated are marked with aster- 

 isks. 



The table for water shews, that between 0° and 30° centi- 

 grade, the formula agrees closely with the experiments of 

 Hallstrom, and that from 30° to 100° its results lie between 

 those of the experiments of Gay-Lussac and Deluc. 



The experiments of Gay-Lussac originally gave the appa- 

 rent volume of water in glass, as compared with that at 100°. 



