1^5 Of the State of Vapour 



As air is cooled by the reception of moifture diflblved in it, 

 we mull inttr that its capacity for containing heat is in- 

 creafed, and hence moift air is more difficultly lieated or 

 cooled than dry air of the fame temperature, (or the cold 

 proceeds from the abforption and not from the expuKion ot 

 caloric.) 



The elaftlcity or expanfive force of pure vapour has been 

 examined at every fifth degree of Reaumur above o to no", 

 bv Mr. Betancourt, and may be feen in an excellent work of 

 Pronv's, his ylrchiittlure Hydraullquc : he has by a moft in- 

 genious calculation interpolated the expanfions anfwering to 

 the intermediate degrees. But Mr. Schmidt feenis to have 

 determined this expanfive force ftill more exactly than Betan- 

 court. Hence I here infert this table, adding Fahrenheit's 

 for Reaumur's degrees, and difiinguifliing the expanfions in- 

 terpolated by calculation from thofe aftually obferved by /. 

 Tlie forces are meafured by the elevation of a mercurial co- 

 lunm in inches and hundreds of a French inch*. 



• Tlie Paris aihic inch = i-ii EngliCh. Now the F.n. l:(li cubic inch 

 r.errury when its Tpecific gravity h 13 6 wcij^hs :;443-2 lilnijlilh grains: 

 reforc the Paris inch weighs 4186 Engiifli grains, and i-ioth of this 



tncretorc tne rans incn wcigns 41 so nngiiin grains, ano i 

 hich =. 41IS-6 grains : and i-iooth of this inch 41-06 grains. 



NotS^ 



