the several Gases in ihe Atmosphere. 355 



he used caustic alkali as the absorbent, which would extract 

 the carbonic acid as well a* the aqueous vapour from the 

 air. From the experiments of Pictet and Watt, I deduce 

 the specific gravity of aqueous vapour to be ,01 and ,0/ re- 

 spectively. Upon the whole, therefore, it is probable that 

 ,7 is very nearly accurate. 



We have now sufficient data to form tables answcrino- to 

 the two first objects of our inquirv. 



I. Table of the ffl-ights of the (liferent Guscs constituting 

 the Atmosphere. 



Inch, of mercury. 



Azotic gas - - - 23-36 



Oxygenous gas - - - (J- 18 



Aqueous vapour - - -44 



Carbonic acid tras - - '02 



30-00 



U. Table if the proportional IFeighls of the different Gasea 

 in a given Foliime of Atmospheric Air, taken at the Sur- 

 face of the Earth. 



100-00 

 III. On the Proportion of Gases at different Elevations. 

 M. BerthoUet seems to think that the lower strata of the 

 atmosphere ought to contain more oxygen than the upper, 

 because of the greater specific gravity'of oxygenous ga--, 

 and the slight alHnity of the two gases' for each other. (See 

 Annal. de Chimie, torn, xxxiv. p. 85.) As I am unable to 

 conceive even the possibility of two gases being held toge- 

 ther by affinity, unless their particles unite so as to form 

 one centre of repulsion out of two or more (in which ca.se 

 they become one ga*), I camiot see why rarefaction should 

 either decrease or increase this supposed alllnity. I have 

 httic doubt, however, as to the fact of oxygenous gas ob- 

 serving a diminishing ratio in asceiwJing';"for, the atmo- 

 spheres being independent on each other^ their densities at 

 difTerent heights must be reg<dated by their specific gravi- 



* The proporticin of Hquciiiis vapour must be '.ludiTslood to be variablf 

 for any one pl.ict-: il,.- otlitTs arc ptTniaiu-tit, or ucurly to. 



/ 2 tie-. 



