[ 356 ] 



As air is cooled by the reception of moifture diffolved in i^, 

 we muft infer that its capacity for containing heat is increafed; 

 and hence moift air is more difficultly heated or cooled than dry 

 air of the fame temperature. (For the cold proceeds from the 

 abforption and not from the expulfion of caloric.) 



The elafticity or expanfive force of pure vapour has been exa- 

 amined at every fifth degree of Reaumur above o to i ro°. by Mr. 

 Betancourt, and may be feen in an excellent work of Prony's, 

 his ArchiteBiire Hydraulique, he has by a moft ingenious cal- 

 culation interpolated the expanfions anfwering to the interme- 

 diate degrees. But Mr. Sckmidt feems to have determined this 

 expanfive force flill more exadly than Betancourt. Hence I here 

 infert his table, adding Fahrenheit's for Reaumur's degrees, and 

 diftinguifhing the expanfions interpolated by calculation from thofe 

 adually obferved by /. The forces are mcafured by the elevation 

 of a mercurial column in inches and hundreds of a French inch.* 



Reaumur. 



*The Paris cubic inch=ii,2i Englifh. Now the Engliflicublc inch of mercury 

 when its fpecific gravity is 13,6 weighs 3443,2 Englifli grains, therefore the Paris 

 inch weighs 418S Englifli grains, and -."j- of this Inch = 418,6 grs: and t5^ of this 

 inch 41,86 grains. 



