201 
It had burnt tranquilly and equally for twelve minutes and 
thirty seconds, when the thermometer placed in the caul¬ 
dron showed that the water had acquired the temperature 
of 75° Fahrenheit. I immediately extinguished the candle, 
and on weighing it anew, I found that it had consumed 1.62 
grammes of wax during the experiment. 
The difference between the quantities of wax burnt in 
these two experiments, in giving the same quantity of heat 
to the same quantity of water, is very small (=0.07 of a 
gramme) and it can be readily explained, in a satisfactory 
manner, without having recourse to the supposition (other¬ 
wise very improbable) that the temperature at which the 
decomposition of an inflammable substance takes place in 
combustion, is perhaps variable. 
The light which is manifested in this process is to a cer¬ 
tainty variable, and to a surprising degree. 
The results of the experiments which we have related 
are very interesting, and the more we examine them, the 
more important do the facts which they present to us appear. 
They teach us more fully to comprehend light and heat y 
and to distinguish and appreciate their effects. 
There will be less difficulty in conceiving the existence of 
a true combustion, accompanied by its peculiar temperature, 
in all the cases, when the products of a chemical operation 
indicate it, even though the light which accompanies it 
should not be visible, and though the heat found which re¬ 
sults from it, should not evince directly, the existence of so 
high a temperature. 
There will also be less difficulty in admitting that all 
chemical operations have always a regard to fixed and in¬ 
variable temperatures in all cases. 
Since we have regarded light as a peculiar substance, 
we have naturally endeavored to comprehend its combina¬ 
tions with other substances, and the laws of its affinities ; 
and without permitting ourselves in the least to doubt the 
reality of its existence as a substance, we have become so 
