= 
380 ON COMBUSTION IN RAREFIED AIR. 
ON COMBUSTION IN RAREFIED AIR. 
BY DR. EDWARD FRANKLAND, F.R.S. 
(From the Proceedings of the Royal Society. Vol. XI., No. 43.") 
“Tn the autumn of 1859, whilst accompanying Dr. Tyndall to the 
summit of Mont Blanc, I undertook at his request some experiments 
on the effect of atmospheric pressure upon the amount of combustible 
matter consumed by a common candle. I found that, taking the 
average of five experiments, a stearin candle diminished in weight 
9:4 grammes when burnt for an hour at Chamounix; whilst its igni- 
tion for the same length of time on the summit of Mont Blane, 
perfectly protected from currents of air, reduced its weight to the 
extent of 9°2 grammes. 
«This close approximation to the former number under such a 
widely different atmospheric pressure, goes far to prove that the 
rate of combustion is entirely independent of the density of the 
atmosphere. 
«Tt is impossible to repeat these determinations in a satisfactory 
manner with artificially rarefied atmospheres, owing to the heating 
of the apparatus which surrounds the candle, and the consequent 
guttering and unequal combustion of the latter; but an experiment 
in which a sperm candle was burnt first in air under a pressure of 
28°7 inches of mercury, and then in air at 9 inches pressure, other 
conditions being as similar as possible in the two experiments, the 
consumption of sperm was found to be,— 
“ At pressure of 28°7 inches’ 7°85 grms. of sperm per hour, 
(it 9:0 ce 9:10 3 (13 
thus confirming, for higher degrees of rarefaction, the result pre- 
viously obtained. 
“Tn burning the candles upon the summit of Mont Blane, I was 
much struck by the comparatively small amount of light which they 
* Paper received, February 28th ; Read, March 7th, 1861. 
