650 DE. E. FEANKLAND ON THE INFLUENCE OF ATMOSPHEEIC PEESSUEE 
the sense of an escape of carbonic oxide instead of carbonic acid from the flame, could 
not be thus decided, and demanded a closer investigation. 
To determine this point I collected samples of the gases escaping from the chimney h 
(flg. 1) of the experimental flame (which in this case was that of a sperm candle) when 
burning under atmospheric pressure, and again when burning under a pressure of 
only 8 inches of mercury. These gases were first treated with caustic potash to absorb 
carbonic acid ; they were then exploded with an equal volume of electrolytic water-gas, 
and subsequently mth excess of hydrogen. The explosion -with water-gas caused no 
contraction, proving the absence of carbonic oxide. The follomng numbers were 
obtamed : — 
I. Gases from candle burning at atmospheric pressure : — 
' 
Volume of gas. 
Temperature. 
Gas used 
256-0 
7-0° C. 
After absorption of carbonic acid ... 
238-1 
7-0 „ 
After explosion with electrolytic gas.. 
238-0 
7*0 „ 
After admission of hydrogen 
373-7 
7-0 „ 
After explosion 
283-6 
7-0 „ 
II. Gases from candle burning at 8 inches mercurial pressure : — 
Volume of gas. 
Temperature. 
Gas used 
290-8 
7-1° c. 
After absorption of carbonic acid ... 
267-2 
7-1 „ 
After explosion with electrolytic gas.. 
267-3 
7-1 „ 
After admission of hydrogen .... 
457-8 
7-1 „ 
After explosion 
367-9 
7-1 „ 
These numbers give the following per-centage composition of the two samples of gas : — 
I. 
II. 
Nitrogen .... 
81-28 
81-58 
Oxygen .... 
11-73 
10-30 
Carbonic acid . 
6-99 
8-12 
Carbonic oxide . . 
. . . . . 0-00 
0-00 
100-00 
100-00 
These results prove that in both cases there was no escape of unconsumed combus- 
tible gas; consequently the diminution of light in rarefied atmospheres is not due to 
imperfect combustion in any form. 
Taken in connexion with the experiments in compressed air, in which imperfect com- 
bustion attended with the evolution of fuliginous matter was very marked, these data 
lead to the remarkable conclusion that the compression of air renders the combustion of 
gaseous matter less perfect ; and that, within certain limits at least, the more rarefied the 
atmosphere in which flame burns, the more complete is its combustion. Thus it is ewdent, 
not only that no diminution of light can arise from imperfect combustion in rarefied 
