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ed, and is very beautiful; and as the purified oil, employed 
in these lamps in Paris, burns without smoke or odour, and 
without residuum, I endeavored, moreover, to discover 
whether this lamp always gave a quantity of light which 
was in an invariable proportion to the oil burnt. The fol¬ 
lowing are the experiments and their results. 
Exp,, 1.—An excellent lamp, which had been carefully 
cleaned, adjusted, and weighed, was lighted and placed be¬ 
fore the photometer, where it was regulated, for 30 min¬ 
utes, in such a manner as to afford constantly 100° of light; 
the same quantity which the candle had furnished. 
At the end of this experiment, the lamp was extinguished, 
and on weighing it anew, I found there had been 8 grammes 
of oil consumed. 
This quantity is =114 parts, consequently the consump¬ 
tion of the lamp was in the proportion of 228 parts of oil 
per hour, for 100° of light; or for 100 parts of oil, it had 
yielded 48° of light. 
The candle consumed 100 parts of wax, and gave 100® 
of light. 
Exp. 2.*—-The lamp having been cleaned, adjusted, and 
weighed again, was placed before the photometer, directly 
opposite the division of its scale marked 200°, when, after 
having been lighted, it was regulated in such a manner, for 
30 minutes, as to give uniformly 200° of light. 
In this experiment, 10.3 grammes of oil were consumed. 
That is, in the ratio of 271 parts of oil per hour, for 200° of 
light, or for 100 parts of oil, 74° of light. 
Exp. 3.—-The lamp having been cleaned and adjusted as 
before, was placed for the third time before the photometer. 
In this experiment, it gave during 30 minutes, 300° of light, 
and consumed 10.7 grammes of oil. 
That is, in the ratio of 305 parts of oil per hour, for 300°; 
or for 100 parts of oil, 98 p of light. 
Exp. 4.—'The lamp having been carefully prepared and 
placed before the photometer, was managed for thirty mi- 
