5 ° 
Sir H. Davy’s researches on flame. 
therefore probable that it would bear a greater degree of rare- 
faction, without 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. Oxygene and hydrogene in 
the proportion to form water, will not explode by the elec- 
trical spark when rarefied eighteen times, but hydrogene and 
chlorine in the proportion to form muriatic acid gas, gave a 
distinct flash of light under the same circumstances, and they 
combined with visible inflammation when the spark was 
passed through them, the exhaustion being to ~ th. 
The experiment on the flame of hydrogene 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 inflammation continued when the rarefac- 
tion was 9 times, whereas it would only continue in air 
rarefied 6 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 ~ of the original quantity of air, though with- 
out foreign heat its flame was extinguished when the quantity 
was i. 
I rarefied a mixture of oxygene and hydrogene by the air 
pump to about eighteen times, when it could not be in- 
flamed by the electric spark. I then heated strongly the 
