6 Some new Researches on Flame. 
burned with a very feeble blue flame in air rarefied fifteen times, 
and at this pressure the flame heated a wire of platinum to dull 
redness, nor was it extinguished till the pressure was reduced to 
1-20th*. 
Phosphorus, as has been shown by M. Van Marum, burns in 
an atmosphere rarefied sixty times : and I found that phosphu- 
retted hydrogen produced a flash of light when admitted into 
the best vacuum that could be made, by an excellent pump of 
Nairu’s construction. 
The mixture of chlorine and hydrogen inflames at a much 
lower temperature than that of hydrogen and oxygen, and produces 
a considerable degree of heat in combustion; it was therefore 
probable that it would bear a greater degree of rarefaction, with- 
out having its power of exploding destroyed ; and this I found 
in many trials is actually the case, contrary to the assertion of 
M. de Grotthus. Oxygen and hydrogen i in the proportion to 
form water, will not explode by the electrical spark when rarefied 
eighteen times ; but hydrogen and chlorine in the proportion to 
form: muriatic acid gas, gave a distinct flash of light under the 
same circumstances, aud they combined with visible inflamma- 
tion when the spark was passed through them, the exhaustion 
being to 1-24th. 
The experiment on the flame of hydrogen with the wire of 
platinum, and which holds good with the flames of the other 
gases, shows, that by preserving heat in rarefied air, or giving 
heat to a mixture, inflammation may be continued when, under 
common circumstances, it would be extinguished. ‘This I found 
was the case in other instances, when the heat was differently 
communicated: thus, when camphor was burned in a glass tube, 
so as to make the upper part of the tube red hot, the inflamma- 
tion continued when the rarefaction was nine times, whereas it 
would only continue in air rarefied six times, when it was burned 
in a thick metallic tube which could not be considerably heated 
by it. 
By bringing a little naphtha in contact with a red hot iron, 
it produced a faint lambent flame, when there remained in the 
receiver only 1-30th of the original quantity of air, though with- 
out foreign heat its flame was extinguished when the quantity 
was 1-6th. 
* The temperature of the atmosphere diminishes in a certain ratio with 
its height, whieh must be attended to in the conclusions respecting com- 
bustion in the upper regions of the atmosphere, and the elevation must be 
somewhat lower than in arithmetical progression, the pressure decreasing 
in geometrical progression. 
There is, however, every reason to believe, that the taper would be ex- 
tinguished at a height of between nine and ten miles, hydragen between 
twelve aud thirteen, and sulphur betwoew fifteen and sixteen. 
I rarefied 
