TJPOJ^ SOME OF THE PHENOMENA OF COMBUSTION. 
645 
of (ctmospheric ^pressure ; or, more generally, the diminution in illuminating grower is 
directly proportional to the diminution in atmospheric pressure. 
It must, however, here be remarked that the above determinations only establish the 
constant 5’1 for the particular quality of gas with which the experiments were performed. 
It still remained to be ascertained whether a flame from gas of a different quality would 
be amenable to the same rate of reduction ; a fourth series of observations was therefore 
made with gas naphthalized to such an extent as nearly to double its illuminating 
power. The consumption of gas by the experimental flame was, as before, ‘65 cubic foot 
per horn’. The following results were obtained : — 
Fourth Series. 
No. of 
Obser- 
vation. 
Illuminating power of Experimental Flame compared w 
th Standard Flame at 100. 
Pressure of air in receiver = 
6‘9 in. mercury. 
9'9 in. mercury. 
14'9 in. mercury. 
19’9 in. mercury. 
24’9 in. mercury. 
29'9 in. mercury. 
1 
1-0 
7-3 
28-0 
55-6 
85-3 
114-0 
2 
1*0 
7*2 
28-0 
55-5 
85-2 
114-0 
3 
M 
7-2 
28-1 
55-6 
85-2 
114-1 
4 
1*0 
7-3 
28*2 
55-6 
85-3 
114-2 
5 
1-0 
7’5 
28-1 
55-8 
85-3 
114-5 
6 
•9 
7-5 
28-1 
55-9 
85-5 
114-6 
7 
•9 
7-2 
28-2 
55-8 
85-6 
114-8 
8 
1-0 
7-2 
28-2 
55-7 
85-6 
114-9 
9 
•9 
7-2 
28*1 
55-9 
85-5 
115-1 
10 
1-0 
7*3 
28-2 
55-9 
85-.7 
115-2 
11 
M 
7*4 
28-3 
55-5 
85-4 
115-2 
12 
M 
7-5 
28-3 
55-4 
85-3 
115-3 
13 
•9 
7-5 
28-3 
55-5 
85-7 
115-5 
14 
•9 
7-6 
28-5 
55-2 
85-7 
115-4 
15 
•9 
7-5 
28-3 
55-3 
85-5 
115-4 
16 
1-0 
7-6 
28-3 
55-1 
85-9 
115-5 
17 
1-0 
7-6 
28-4 
55-2 
86-0 
115-5 
18 
M 
7-5 
28-4 
55-3 
86-0 
115-4 
19 
M 
7-5 
28-5 
55-3 
86-0 
115-2 
20 
M 
7-6 
28-3 
55-7 
85-6 
115-2 
Mean 
1-00 
7-42 
28-24 
55-54 
85-58 
114-95 
The following Table, calculated from the above, shows that these results are completely 
in harmony with those obtained with unnaphthalized gas, thus proving that the rate of 
diminution of luminosity in rarefied air is the same for all hydrocarbon gases, of what- 
soever quality ; the two last columns being nearly identical down to I4'9 inches pressure. 
Pressure of air 
I in inches of 
I mercury. 
Mean illumi- 
nating power. 
Experimental. 
Mean illumi- 
nating power. 
Eeduced. 
Illuminating 
power. 
Calculated. 
29-9 
114-95 
100 
100 
24-9 
85-58 
74-4 
74-5 
19-9 
55-54 
48-3 
49-0 
14-9 
28-24 
24-5 
23-5 
9-9 
7-42 
6-4 
- 2-0 
6-9 
1-02 
-9 
-17-3 
4 s 2 
