measuring the comparative Intensities of Light. 99 
clear, bright flame, without the least appearance of smoke, I 
found the intensities of the light emitted by the two lamps to 
be to each other as 1795b to 9063 ; the densities of the 
shadows being equal when the Argand’s being placed at the 
distance of 134 inches, the common lamp was placed at the 
distance of 95,2 inches, from the field of the photometer. 
Both lamps having been very exactly weighed when they 
were lighted, they were now (without being removed from 
their places before the photometer), caused to burn with the 
same brilliancy just 30 minutes ; when they were extinguished 
and weighed again, and were found to have consumed of oil, 
the Argand’s lamp and the common lamp of a 
Bavarian pound. 
Now as the quantity of light produced by the Arg and's lamp, 
in this experiment, is to the quantity produced by the common 
lamp, as 17956109063, or as 187 to 100 ; while the quantity 
of oil consumed by the former is to that consumed by the latter 
only in the ratio of 253 to 163, or as 155 to 100, it is evident 
that the quantity of light produced by the combustion of a 
given quantity of oil in an Argand's lamp is greater than that 
produced by burning the same quantity in a common lamp, in 
the ratio of 187 to 155, or as 100 to 85. 
The saving, therefore, of oil which arises from making use 
of an Argand's lamp instead of a common lamp in the pro- 
duction of light, is evident ; and it appears from this experi- 
ment that that saving cannot amount to less than 1 5 per cent. 
How far the advantage of this saving may, under certain cir- 
cumstances, be counterbalanced by inconveniences that may 
attend the making use of this improved lamp, I will not pre- 
tend to determine. 
O 2 
