measuring the comparative Intensities of Light. io,i 
liancy, its light was as 100 ; in eleven minutes it was but 39 ; 
after eight minutes more had elapsed, its light was reduced to 
23 ; and in ten minutes more, or twenty-nine minutes after it 
had been last. snuffed, its light was reduced to 16. Upon be- 
ing again snuffed it recovered its original brilliancy, 100. 
Of the relative Quantities of Bees Wax , Tallow, Olive Oil, Rape 
Oil, and Linseed Oil, consumed in the Production of Light*. 
In order to ascertain the relative quantities of bees wax and 
of olive oil consumed in the production of light, I proceeded in 
the following manner. Having provided an end of a wax 
candle of the best quality, ,68 of an inch in diameter, and 
about four inches in length, and a lamp with five small wicks, 
which I had found upon trial to give the same quantity of light 
as the candle, I weighed very exactly the candle, and the lamp 
filled with oil, and then placing them at equal distances (40 
inches) before the field of the photometer, I lighted them 
both at the same time j and after having caused them to burn 
with precisely the same degree of brightness just one complete 
hour, I extinguished them both, and weighing them a second 
time, 1 found that 100 parts of wax, and 129 parts of oil, had 
been consumed. 
Hence it appears,, that the consumption of bees wax is to 
the consumption of olive oil, in the production of the same 
given quantity of light, as iqo is to 12 ^. 
In this experiment no circumstance was neglected that could 
tend to render the result of it conclusive. Care was taken to 
snuff the candle very often with a pair of sharp scissars, in order 
to make it burn constantly with the same degree of brilliancy ; 
