152 MR W. J. MACQUORN RANKINE ON THE DENSITY OF STEAM. 



the values of the constants for steam being, — 



A, for pounds of pressure on the square foot, . . 8-2591 ; 



log. B for Fahrenheit's scale . . . . = 3-43642 ; 



log. C „ „ .... =5-598"3. 



V. The volume of a cubic foot of liquid water at the temperature T may be 

 computed with sufficient accuracy for the present purpose by the following 

 formula : — 



?? nearly = 000801(3^ + ^^) (15.) 



VI. These preliminary calculations having been made, the formula 9 can now 

 be applied to the calculation of the volume of one pound of steam (making 

 J = 772) ; and by this process the tables already mentioned were computed. 



Comparison of the Results of Theory, with those of Messrs Fairbairn and Tate's 



Expe7'iments. 



12. The experiments of Messrs Fairbairn and Tate on the density of steam 

 are described in a paper which was read to the Royal Society of London, as the 

 Bakerian lecture, on the 10th of May 1860, and published in the " Philosophical 

 Tranactions" for that year. The results of those experiments give what is called 

 the " relative volume'''' of steam : that is, the ratio which its volume bears to that 

 of an equal weight of water at the temperature of greatest density, 39'' '1 Fahr. ; 

 but in the following table of comparison, each of those relative volumes is divided 

 by 62-425, the weight of a cubic foot of water at 39°-l in lbs., so as to give the 

 volume of one lb. of steam in cubic feet. The numbers of the experiments are the 

 same as in the original paper ; those made at temperatures below 212^ being 

 numbered from 1 to 9, and those made at temperatures above 212° from 1' to 

 14'. 



