[ 510 ] 



LXXVIII. — On the Heat of Vapours and on Astronomical Refrac- 

 tions. By John William Lubbock, Esq., Treas. R.S. F.R.A.S. 

 and F.L.S., Vice-chancellor of the University of Londoji, ^c. 

 [Continued from p. 441.] 



ON THE PRESSURE OF STEAM. 



'T^HE most accurate and extensive experiments by which the ac- 

 -■- curacy of these relations can be tested are those M'hich have been 

 made upon the conditions of steam. The following are the experi- 

 ments of Arago and Dulong, as recorded in tom. x. of the Memoires 

 de V Institute p. 231 ; together with the temperatures calculated by 

 the best empirical formulas*. 



=> c 



•OS 

 . > 



Elasticite 

 en metres 



de mer. 

 cure a 0°. 



Elasticite 



en at- 



mosph. de 



Om-76. 



Tempe- 

 rature 

 observee. 



Temperature 

 calculee par 

 la formule 

 de Tredgold. 



Temperature 



calculee par 



la formule 



de Roche 



coeff. moyen. 



Temperature 

 calculee par 

 la formule 

 deCoriolis. 



Temperature 



calculee par 



la formule 



adoptee. 









Cent. 



Cent. 



Cent. 



Cent. 



Cent. 



1 



1-62916 



2-14 



123°-7 



123°54 



123°58 



123°-45 



122°97 



3 



2-1816 



2-8705 



133-3 



133-54 



133-43 



133-34 



132-9 



5 



3-4759 



4-5735 



149-7 



150-39 



150-23 



150-3 



149-77 



8 



4-9383 



G-4.^n 



163-4 



164-06 



163-9 



164-1 



163-47 



9 



5-6054 



7-3755 



168-5 



169-07 



169-09 



169-3 



168-7 



15 



8-840 



11-632 



188-5 



188-44 



188-63 



189-02 



188-6 



21 



13-061 



17-185 



206-8 



206-15 



207-04 



207-43 



207-2 



12 



13-137 



17-285 



207-4 



206-3 



206-94 



207-68 



207-5 



25 



14-0634 



18-504 



210-5 



209-55 



210-3 



211-06 



210-8 



28 



16-3816 



21-555 



218-4 



216-29 



218-01 



218-66 



218-5 



30 



18-1894 



23-934 



224-15 



222-09 



233-4 



224-0 



224-02 



There are reasons which make it probable that in inquiries of this 

 nature the scale of temperature as indicated by the expansion of air 

 is to be preferred, although the difference between the indications 

 of a mercury thermometer with that of air is not considerable. 



The following table is given by M. Pouillet [Siemens de Phy- 

 sique^ vol. i. p. 259) for the centigrade scale : 



Temperatures indiquees par 



le therm, a mercure, a en. 



veloppe de verre. 



Temperatures indiquees par 



un therm, a air, et corrigees 



de la dilatation du verre. 



Volumes correspondans 

 d'une meme masse d'air. 



-36 

 

 100 

 150 

 200 

 250 

 300 

 Ebull.dumerc. 360 



-36° 

 

 100 

 148-70 

 197-05 

 245-05 

 292-70 

 350-00 



0-8650 

 1-0000 

 1-3750 

 1-5576 

 1-7389 

 1-9189 

 2-0976 

 2-3125 



[* Many of the results stated in the table of the French chemists are absolutely iden- 

 tical with those which had been published by Mr. Philip Taylor in 1822. See his Paper 

 in the Philosophical Magazine, First Series, vol. Ix. p. 452,, and the accompanying en- 

 graved Table of his experimental results. — Edit,] 



