UPON SOi\lE OP THE PHEjN'OIIENA OP COMBUSTION. 
647 
interior of D is connected with the pressure-gauge G by the tube whilst the cock d 
conununicates with the compressed-air reservoir F by means of the tube/*. E is a con- 
densing syiange communicating with F by the tube k. By this interposition of the 
reserv’oir F, a very constant pressure could easily be maintained in the cylinder D. 
The experiments were made in the following manner. The cover a being removed, 
and F charged with compressed air, a gentle stream of the latter was turned into D 
through the cock d. The lamp e was now lighted and the cover a firmly screwed into 
its place, the cock c being wide open. The admission of air through d was then regulated 
so as to produce in the chimney h that degree of di-aught necessary for obtaining the 
maximum amount of light in the experimental flame. After the latter had been allowed 
to bum for about half an hour, so as to bring the surrounding glass to a temperature 
which afterwards remained tolerably uniform, a series of photometrical observations were 
made. The egress of air through the cock c was then gradually diminished, whilst d 
was fully opened, so as to establish a free communication, and consequently an equality 
of pressure, between the reservoir F and the cylinder D. The pressure, as indicated by 
the gauge G, was now adjusted, by the more or less rapid working of the pump E, to 
that required for the next series of observations. In practice it was found impossible, 
with the same liquid in the lamp, to extend any series of observations over a greater 
range than one atmosphere, owdng to the experimental flame beginning to smoke 
at the higher pressure, if it possessed a measurable illuminating power at the lower 
one. 
Owing to the difficulties above mentioned, I have only been able to obtain satisfactory 
determinations between one and two atmospheres. In these determinations the lamp 
was supplied with amylic alcohol — a liquid which, whilst affording an appreciable 
amount of light in the experimental flame under one-atmosphere pressure, was found 
to burn under two atmospheres without smoke, although at a somewhat higher pressure 
it began to evolve unconsumed carbon. The following results were obtained : — 
No. of 
Obser- 
Tation. 
Illuminating power of Experimental Flame 
comparetl with Standard Flame at 100. 
Pressure in receiver in inches of mercury = 
29'7 inches. 
59'7 inches. 
59-5 inches. 
1 
21-0 
55-6 
55-3 
2 
21-0 
56-2 
65*4 
3 
21-2 
56-3 
55-3 
4 
2M 
.56-3 
55-4 
5 
21-2 
56-1 
55-4 
6 
2M 
56-0 
55-3 
7 
21-2 
56-0 
55*4 
8 
21-5 
55-9 
55-5 
9 
21-6 
55-6 
55-5 
10 
21-6 
55-4 
55-5 
11 
21-0 
55-4 
55-3 
Mean 
21-2 
53-9 
55-4 
