^56 On the 'Proportion of 



myself both by analytic and synthetic methods, 

 afterthQ manner of De Saussure ; that is, by 

 abstracting aqueous vapour of a known force 

 from a given quantity of air, and v^^eighing the 

 water obtained — and admitting a given weight 

 of water to dry air and comparing the loss 

 with-. the increased elasticity, De Saussure 

 makes the specific gravity to be ,71 or ,75 j 

 but he used caustic alkali as the absorbent, 

 which would extract the carbonic acid as well 

 as :the aqueous vapour from the air. From the 

 experiments of Pictet and Watt, I deduce the 

 specific gravity of aqueous vapour to be fil and 

 ,67 respectively. Upon the whole, therefore, 

 it is probable that ,7 is very nearly accurate. 

 .*" Webave now sufficient data to form tables 

 answering to "^the two first objects of our 

 enquiry. 



-' ■( -• 

 I. Tahlr of the JVeights of the' different 

 Gases constituting the Atmosphere^ 



Inch, of Mercury, 



, Azotic gas , ^3.36 



Oxygenous gas 6, 18 



Aqueous vapour , 44 



Carbonic Acid gas .02 



30 .00 



