148 Observations on Combustion. 
compression, expansion, &c. 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 itis 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. Butin 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 dieangaged from the 
carbon of the wood. 
In the decomposition of water in renee its oxygen sBbiowly 
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 sufficient supply of air. Too 
much vapor dampens the flame, by excluding the air, and too much 
air renders it too ee 
