11 



originally contained. The jar, therefore, was cau- 

 tiously raised out of the mercury, and the attraction 

 of carbonic acid by the alkaline solution was proved 

 by the brisk effervescence which the acetous and di- 

 luted sulphuric acids excited in it. The glass-cup, 

 containing a bulk of water equal to that of the solu- 

 tion employed, was now again put into the jar, pre- 

 viously replaced on its bottom, together with the 

 hoop and peas. Water was next poured in till it 

 reached that part of the jar to which the mercury 

 had risen^ and to raise it thereto required J2.5 cubic 

 inches, which, therefore, was the bulk of residual 

 air at the close of the experiment ; and afterwards, 

 to fill the jar completely, it required four cubic 

 inches more, which consequently was the measure 

 of the volume of air that had disappeared. But 

 these two quantities amount only to 16.5, and the 

 capacity of the jar has been stated to be 18.2 cubic 

 inches: the difference, therefore, equal to 1.7, will be 

 the space which the several substances occupied with- 

 in the jar, and which reduces the actual volume of 

 air employed in the experiment to 16.5 cubic inches, 

 'of which a portion equal to four, or ^ of the 

 whole, had disappeared. 



10. But the volumes of elastic fluids are inversely 

 as the weights by which they are compressed ; and 

 for every degree of Fahrenheit's thermometer, Mr 

 Dalton has found that atmospheric air is dilated ~ 

 part of its bulk under common atmospheric pres- 

 sure*. Making therefore, on these accounts, the 



* Manchester Memoirs, vol. v. 



