2*72 ©N THE FORCE OF STEAM OR VAPOUR. 



force of vapour from any liquid in that temperature, in vacuo J 

 then, the liquid being admitted to the air, an expanfion enfues, 

 and the fpace occupied by the air becomes immediately, of 



in a (liort time = 1 -| ■.; or,, which Is the fame thing, 



P—J 



_ P 



p-f- 



Thus in water for inftance : 

 Letp=30 inches, 



f=l5 inches, to the given temp. ISC. 



Then, — ^.— — -=2, for the fpace: or the air be- 



p—j 30-15 ^ 



comes of twice the bulk. 



If the temperature be 203°, /=25, and the fpace becomes 

 fix times as large as at firft. 

 li' p—60 inches 



f=i30 inches to the given temperature 212° ; then the 



fpace =; = 2 ; or water under the preflure of 60 



^ 60— SO ^ 



inches of mercury, and at the temperature of 212°, produces 

 vapour which jufl doubles the volume of air. 



If ether be the inftance : let the temperature be equal 70°; 

 then/=l5; and fuppofej)r=:30 ; in this cafe the colume of air 

 is doubled ; that is, ether of 70° being admitted to any por- 

 tion of air, doubles its bulk. 



The expanfion of hydrogenous gas and atmofpheric air by 

 the vapour of water is the fame for every temperature. 



Sulphuric acid does not expand atmofpheric air to any fen- 

 fible amount by the heat of boiling water. 



The theory of thele fa6is is evident upon the principles laid 

 down in the former effay : for infiance ; let it be required to 

 explain the experiment with water of 212° under a preflure of 

 60 inches. Here the air was condenfed into the fpace 1 by 

 the preflure of 60 inches; but being expofed to water of 212", 

 a vapour arofe from it equal in force to 30 inches ; the air there- 

 fore expanded till its force alfo became =; to 30 inches, which 

 was effefted by doubling its volume : then the vapour prefling 

 with 30 inches force and the air alfo with 30 inches force, the 

 two together fupport the preflure of 60 inches and the ec^U 

 librium continues. In fliort, in all cafes the vapour arifes to a 



certain 



