Some new Researches on Flame. 5 
red, the gas though extinguished below, continued to burn in 
contact with the hot wire, and the combustion did not cease until 
the pressure was reduced thirteen times. 
It appears from this result, that the flame of hydrogen is ex- 
tinguished in rarefied atmospheres, only when the heat it pro- 
duces is insufficient to keep up the combustion, which appears 
-to be when it is incapable of communicating visible ignition to 
metal; and as this is the temperature required for the inflamma- 
tion of hydrogen at common pressures, it appears that its com- 
dustibility is neither diminished nor increased by rarefaction 
from the removal of pressure. 
According to this view with respect to hydrogen, it should 
follow that amongst other combustible bodies, those which re- 
quire least heat for their combustion, ought to burn in more 
rarefied air than those that require more heat, and those that 
‘produce much heat in their combustion ought to burn, other 
circumstances being the same, in more rarefied air than those 
that produce little heat: and every experiment I have made 
confirms these conclusions. Thus olefiant gas which approaches 
nearly to hydrogen in the heat produced by its combustion, and 
.which does not require a much higher temperature for its in- 
flammation, when its flame was made by a jet of gas from a 
bladder connected with a small tube furnished with a wire of 
platinum, under the same circumstances as hydrogen, ceased to 
-burn when the pressure was diminished between ten and eleven 
times: and the flames of alcohol and of the wax taper which 
require a greater consumption of heat for the volatilization and 
decomposition of their combustible matter, were extinguished 
when the pressure was five or six times less without the wire of 
platinum, and seven or eight times less when the wire was kept 
in the flame. Light carburetted hydrogen, which produces, as 
will be seen hereafter, less heat in combustion than any of the 
common combustible gases, except carbonic oxide, and which 
requires a higher temperature for its inflammation than any other, 
had its flame extinguished, even though the tube was furnished 
with the wire when the pressure was below 1-4th. 
The flame of carbonic oxide which, though it produces little 
heat in combustion, is as inflammable as hydrogen, burned when 
the wire was used, the pressure being 1-6th. 
The flame of sulphuretted hydrogen, the heat of which is in 
some measure carried off by the sulphur produced by its decom- 
position during its combustion in rare air, when burned in the 
same apparatus as the olefiant and other gases, was extinguished 
when the pressure was l-7th, 
_ Sulphur, which requires a lower temperature for its combustion 
than any common inflammable substance, except phosphorus, 
Ag burned 
