of the Light emitted by Luminous Bodies. 33 



Of the relative Quantities of Oil consumed and of 

 Light emitted by an Argands Lamp, and by a 

 Lamp on the common Construction, with a Riband 

 Wick. 



The brilliancy of the Argand's lamp is not only 

 unrivalled, but the invention is, in the highest degree, 

 ingenious, and the instrument useful for many pur- 

 poses ; but still, to judge of its real merits, as an illu- 

 minator, it was necessary to know whether it gives 

 more light than another lamp in proportion to the oil 

 consumed. This point I determined in the following 

 manner. 



Having placed an Argand's lamp, well trimmed, and 

 burning with its greatest brilliancy, before my pho- 

 tometer, and over against it a very excellent common 

 lamp with a riband wick, about an inch wide, and 

 which burned with a 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 1 7956 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 pho- 

 tometer. 



Both lamps having been very exactly weighed when 

 they were lighted, they were now (without being re- 

 moved 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 -ft 5 ^, an< ^ ^e comm on lamp sSftfe, of a Bavarian 

 pound. 



VOL. IV. -\ 



