Sir H. Davy’s researches on flame, ' 4 7 
experiment called the philosophical candle, so as to make a 
jet of flame of about of an inch in height, and introduced 
under the receiver of an air pump containing from 200 to 300 
cubical inches of air, the flame enlarged as the receiver 
became exhausted ; and when the gage indicated a pressure 
between 4 and 5 times less than that of the atmosphere was at 
its maximum of size, it then gradually diminished below, but 
burned above till the pressure was between 7 and 8 times less, 
when it became extinguished. 
To ascertain whether the effect depended upon the defi- 
ciency of oxygene, I used a larger jet with the same appa- 
ratus, when the flame to my surprise burned longer, and when 
the atmosphere was rarefied ten times, and this in repeated 
trials. When the larger jet was used, the point of the glass 
tube became white hot, and continued red hot till the flame 
was extinguished. It immediately occurred to me, that the 
heat communicated to the gas by this tube, was the cause that 
the combustion continued longer in the last trials when the 
larger flame was used ; and the following experiments con- 
firmed the conclusion. A piece of wire of platinum was coiled 
found the top of the tube, so as to reach into and above the 
flame. The jet of gas of of an inch in height was lighted, 
and the exhaustion made; the wire of platinum soon became 
white hot in the centre of the flame, and a small point of 
wire near the top fused : it continued white hot till the pres- 
sure was 6 times less, when it was 10 times it continued red 
hot at the upper part, and, as long as it was dull 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 13 times. 
It appears from this result, that the flame of hydrogene is 
