AND PRACTICAL DEDUCTIONS. 75 



as simple gases, or united as ammonia : the 

 hydrogen e also, is often combined with carbon, 

 forming carburetted hydrogene gas. 



Carbonic acid^gaSj orjfixed^air, is formed by a 

 certain portion of carbon being dissolved and 

 held in solution or ^combination by oxygene, 

 and is more ponderous than atmospheric air. 



is composed of carbon, and a 



portion of oxygene less than sufficient to pro- 

 duce carbonic acid. j 



Carburetted hydrogene gas, is carbon dissolved 

 in hydrogene, and is much lighter than atmo- Y 

 spheric air ; it is this gas by which balloons are 

 inflated, and which is burnt to give light, instead 

 of oil, &c. in lamps. 



These elements being thus separated, are 

 again combined by the various processes of 



nature. 



By the combustion of electricity, the oxygene 



gas^emitted by vegetables, and the hydrogene gas 

 by putrescent animal and vegetable matter, are 

 united and fojinjvjjjer ; and the proportions are 

 85 oxygene, and 15 hydrogene. By natural ja 

 nity, oxygene gas is combined with the nitrogene 

 gas, thrown off by the respiration of animals, 

 and atmospheric air formed ; and the proportions 

 are 22 oxygene, and 77 nitrogene. 



Carbonic acid gas, from its density, is readily 



