640 DE. E. EEANEXAOT) ON THE INELIJENCE OE ATMOSPHEEIC PEESSUEE 
from the room, a preliminary observation was made of the illuminating power of the 
experimental flame as compared with the standard. Owing to the gradual heating of 
the apparatus surrounding the experimental flame, the temperature, and consequently 
the luminosity of the latter, underwent a gradual and not unimportant increase, which 
continued for about an hour, when the illuminating power became perfectly constant. 
As soon as this constancy of light had been obtained, twenty observations of the 
illuminating power were made. The pressure in F was then suffered to rise to the point 
at which the next observations were to be made. The consumption of gas was again 
carefully adjusted to *65 cubic foot per hour, when twenty photometrical obser^^ations 
were again made. Similar sets of observations at the remaining higher pressures up to 
the full atmospheric pressure completed the series. 
In the following tabulated results the illuminating power of the standard flame is 
assumed to be 100, whilst the numbers given in the several columns represent the lumi- 
nosity of the experimental flame compared with this standard. In all the series of ob- 
servations, the consumption of gas by the experimental flame was *65 cubic foot per 
hour, measured at the atmospheric pressure. 
First Series. 
No. of 
Obser- 
vation. 
Illuminating power of Experimental Flame compared with Standard Flame at 1 00. 
Pressure of air in receiver = 
6'6 in. mercury. 
9'6 in. mercury. 
14‘6 in. mercury. 
19'9 in. mercury. 
24’9 in. mercury. 
29 ‘9 in. mercm’y. 
1 
10 
6-4 
24-2 
63-4 
90-2 
119'9 
2 
10 
6-4 
24-4 
63-4 
901 
119-6 
3 
1-1 
6-5 
24-1 
631 
90-0 
119-3 
4 
1-0 
6-5 
24-1 
631 
89-8 
119-2 
5 
11 
6-5 
24-1 
63-3 
90-4 
119-5 
6 
1-2 
6-6 
24-2 
631 
90-4 
119-6 
7 
1-2 
6-5 
24-2 
63-2 
90-2 
119-4 
8 
1-1 
6-5 
24-4 
63-2 
90-1 
119-6 
9 
1-2 
6-4 
24-4 
63-4 
90-1 
119-5 
10 
1-1 
6-5 
24-4 
63-3 
90-0 
119-5 
11 
1-1 
6-5 
24-1 
63-5 
89-8 
119-7 
12 
1-2 
6-5 
24-2 
63-5 
89-8 
119-9 
13 
1-1 
6-6 
24-2 
63-6 
89-7 
120-2 
14 
1-2 
6-5 
24-4 
63-6 
89-9 
120-5 
15 
11 
6-5 
24-3 
63-8 
900 
120-6 
16 
TO 
6-5 
24-2 
64-0 
900 
120-6 
17 
1-1 
6-4 
241 
64-1 
89-8 
120-7 
18 
1*1 
6-5 
241 
64-0 
89-7 
120-7 
19 
1-0 
6-5 
24-2 
63-8 
89'9 
120-8 
20 
M 
6-5 
24-1 
63-8 
900 
120-6 
Mean 
1*1 
6-5 
24-2 
63-5 
90-0 
119-97 
