512 



Mr. Lubbock on the Heat of Vapours 



[2'0651059] 



- 448°, 



^.013* _ _i. 17602 



and if g be the density of steam, the relative vohime 



q p {p'^^S4_ 1.17602} 



7~~ P' {;j''o*^* - 1-17602}' 



In order to ascertain how far the new expression here given for 

 T represents the totality of the observations, 1 have calculated the 

 temperatures corresponding to all the observed pressures in the ob- 

 servations of Arago and Dulong, and the results are exhibited in 

 the following table. 



Pressure in 

 atmospheres. 



Temperature. 



Error of tem- 

 perature cal- 

 culated by 

 Lubbock. 

 Fahr. 



Observed. 



Calculated. 



Merc, therm. 

 Cent. 



Merc, therm. 

 Fahr. 



Air therm. 



Fahr. 



Air therm. 



Fahr. 



2-1400 



123-7 



254-66 



25°3-6 



25°2-8 



-°8 



2-870.) 



133-3 



271-94 



270-4 



270-1 



--3 



4-5735 



149-7 



301-46 



299-2 



299-4 



+ •2 



(J-4977 



163-4 



326-12 



323-0 



323-2 



+ •2 



7-3755 



168-5 



335-30 



331-9 



332-3 



+ •4 



1 1 -(5320 



188-5 



371-30 



366-7* 



366-7 







17-1850 



206-8 



404-24 



398-6 



398-9 



+ •3 



17-2850 



207-4 



405-32 



399-5 



399-4 



-•1 



18-5040 



210-5 



410-90 



404-9 



405-3 



+ •4 



21-5550 



218-4 



42512 



418-5 



418-8 



+ •3 



23-9340 



224-15 



435-47 



428-4* 



428-5 



+ •1 



The observations marked with an asterisk were employed in de- 

 termininfj the constants. 



The error of the temperature calculated by the formula adopted 

 by Arago and Dulong corresponding to the first observation is 

 — '73 cent, or — 1°*3 of Fahr. I have no doubt that the observed 

 temperature is in excess, and the agreement with the rest of the 

 observations is so complete, that within this range of temperature 

 the formula may, I think, be considered as exactly representing the 

 phenomena. The errors of the temperatures, calculated by the 

 various empirical expressions which have been hitherto proposed, 

 are much greater, as may be seen in the table of Dulong and Arago. 

 The following observations are those of Southern, given in p. 172, 

 vol. ii., of Dr. Robison's Mechanical Philosophy. 



