148 Observations on Combustion. 



compression, expansion, he. retaining all the properties of a perma- 

 nent gas. When they are raised to the temperature of flame they 

 then take fire ; the heat and light, being left at liberty or disencum- 

 bered of their base now pass off into space with infinite velocity. But 

 how they find their way back is not obvious; but probably it is by the 

 way of the sun. About one-fifth of the whole atmosphere is compo- 

 sed of one of those gases, oxygen, but without its counterpart, hy- 

 drogen, we could have no flame in combustion. Where shall we 

 find it ? It is not in the atmosphere : It is too light or volatile to re- 

 main there. But in nature every thing is devised in infinite wisdom and 

 for the comfort of man. A quantity of hydrogen equal, in all proba- 

 bility, to that of the oxygen of the air has been made to unite with, 

 and is retained chiefly in the vegetables ; in combination with other 

 combustibles, it is readily disengaged by heat at a low temperature, 

 and as the oxygen of the air is always present, when a flame is applied 

 they instantly take fire and unite or combine, giving out their light 

 and heat and thus forming flame, which continues so long as any 

 vegetable matter remains to be decomposed and in part volatilized. 



Combustion then is, in such cases, the result solely of the recom- 

 position of water ; here then is a source of light and heat that costs 

 nothing, for if we can disengage the hydrogen of the water from the 

 oxygen, it will as surely burn when it comes in contact with the oxy- 

 gen of the air, at a proper temperature, as that disengaged from the 

 carbon of the wood. 



In the decomposition of water in combustion, the oxygen obviously 

 unites with the carbon of the fuel with a disengagement of heat, leav- 

 ing the carburetted hydrogen at liberty, which at a red heat is instantly 

 inflamed on coming in contact with the oxygen of the air, forming 

 water and producing intense heat as usual ; water is again decompo- 

 sed on meeting the first atom of carbon in combustion, and again re- 

 composed with the same effect as at first ; and this process must be 

 continued and repeated while there is any carbon and unburnt air to 

 meet in the combustion. This is made very evident in the great 

 length of the flame with my improved lamp. It will be seen that all 

 this additional flame and heat in the combustion arise solely from 

 the oxygen of the atmosphere and costs nothing, so that the true and 

 much the most economical principle in combustion is to furnish a due 

 proportion of the vapor of water and a suflicient supply of air. Too 

 much vapor dampens the flame, by excluding the air, and too much 

 air renders it too explosive. 



