COMBUSTION, 147 



body, while its caloric, becoming free, is diffused among the 

 surrounding bodies. Whenever we burn a combustible 

 body, a continued stream of atmospheric air flows towards 

 the fire place, to occupy the vacancy left by the air that has 

 undergone decomposition, and which, in its turn, becomes 

 decomposed also. Hence a supply of caloric is furnished 

 without intermission, till the whole of the combustible is 

 saturated with oxygen. As the combustible burns, light is 

 disengaged, and the more subtile parts, now converted by 

 caloric into gas, are dissipated in that state. When the 

 combustion is over, nothing remains but the earthy parts 

 of the combustible, and that portion which is converted, 

 by the process, into an oxyd, or an acid. The smoke which 

 arises from a common fire is chiefly water in the state of 

 vapour, with a mixture of carburetted hydrogen and bitu- 

 minous substances ; part of the water comes from the mois- 

 ture of the fuel ; the other part is formed during combus- 

 tion, by the union of the hydrogen of the combustible with 

 the oxygen of the atmosphere. The agency of oxygen in 

 combustion may be demonstrated by placing a lighted can- 

 dle under a glass vessel inverted upon a plate of water. It 

 will be seen that the candle will go out as soon as it has 

 consumed all the oxygen contained in the included air, and 

 that the water will rise up in the vessel to fill the vacancy. 

 In the decomposition of atmospheric air by combustion, it is 

 natural to ask what becomes of the nitrogen gas? As the 

 oxygen becomes fixed in the combustible body, its caloric is 

 disengaged, a part of which combines with the nitrogen, and 

 carries it ofi" in the form of rarefied nitrogen gas. When 

 bodies are burnt, none of their principles are destroyed. We 

 have reason to think that every particle of matter is inde- 

 structible, and that the process of combustion merely decom- 

 poses the body, and sets its several component parts at 

 liberty, to separate from each other, to form other new and 

 varied combinations. It was said of old, that the Creator 

 weighed the dust, and measured the water, when he made 

 the world. The first quantity is here still ; and though man 

 can gather and scatter, move, mix, and unmix, yet he can 

 destroy nothing : the dissolution of one thing is a prepara- 

 tion for the being, and the bloom, and the beauty of another. 

 Something gathers up all the fragments, and nothing is 

 lost. 



