100 
Count Rumford's Account of a Method of 
Of the relative Quantities of Light emitted by an Argand's Lamp, 
and by a common JVax Ca?idle. 
I have made a considerable number of experiments to de- 
termine this point, and the general result of them is, that a 
common Argand’s lamp, burning with its usual brightness, 
gives about as much light as nine good wax candles ; but the 
sizes and qualities of candles are so various, and the light pn> 
duced by the same candle so fluctuating, that it is very difficult 
to ascertain, with any kind of precision, what a common wax 
candle is, or how much light it ought to give. I once found 
that my Argand’s lamp, when it was burning with its 
greatest brilliancy, gave twelve times as much light as a good 
wax candle of an inch in diameter, but never more. 
Of the Fluctuations of the Light emitted by Candles. 
To determine to what the ordinary variations in the quan- 
tity of light emitted by a common wax candle might amount, 
I took such a candle, and lighting it, placed it before the pho^ 
tometer, and over against it an Argand's lamp, which was 
burning with a very steady flame ; and measuring the inten- 
sity of the light emitted by the candle from time to time, dur- 
ing an hour, the candle being occasionally snuffed when it ap- 
peared to stand in need of it, its light was found to vary from 
100 to about 60. The light of a wax candle of an inferior 
quality was still more unequal, but even this was but trifling 
compared to the inequalities of the light of a tallow candle. 
An ordinary tallow candle, of rather an inferior quality, 
having been just snuffed, and burning with its greatest bril- 
