the several Garef'fk 'tk^ Atftksphere. 2 47 



quickest in ascendiiig, If the earth's atmos- 

 phere had been a homogeneous elastic fluid of 

 the same weight it is, but ten times the specific 

 gravity, it might easily be demonstrated that 

 no sensible portion of it could have arisen to 

 the summits of the highest mountains. On the 

 Other- hand, an atmosphere of hydrogenous 

 g^s, of the same weight, would support a 

 column of mercury nearly 29 inches on the 

 summit of Mount Blanc. 



The several gases constantly found in every 

 portion of atmospheric air, and in such quan- 

 tities as are capable of being appreciated, are 

 azotic, oxygenous, aqueous vapour, and car- 

 bonic acid. It is probable that hydrogenous 

 gas also is constantly present ; but in so small 

 proportion as not to be detected by any test 

 we are acquainted with ; it must therefore be 

 confounded in the large mass of azotic gas. 



i:^0/ the weight of the Oxygenous and Azotic 

 Atmospheres. 



Various processes have been used to de- 

 termine the quantity of oxygenous gas. 



\ . The mixture of nitrous gas and air over 

 W9tcr. 



2. Exposing the air to liquid sulphuret of 

 potash or lime, with or without agil;alioi). 



