372 PHILOSOPHICAL TRANSACTIONS. [aNNQ 1794. 



the liglit of a tallow candle. An ordinary tallow candle, of rather an inferior 

 quality, having been just snuifed, and burning with its greatest brilliancy, its light 

 was as 100 ; in 11 minutes it was but 30 ; after 8 minutes more had elapsed, its 

 light was reduced to 23 ; and in 10 minutes more, or 2g minutes after it had 

 been last snuffed, its light was reduced to l6. On being again snuft'ed it reco- 

 vered its original brilliancy, 100. 



7th. On the Relative Quantities oj Bees JVax, Talloiv, 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 con- 

 sumed in the production of light. Count R. 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 4 inches in length, and a lamp with 5 small wicks, which 

 he found give the same quantity of light as the candle; he weighed very exactly 

 the candle, and the lamp filled with oil, and then placing them at equal dis- 

 tances, 40 inches, before the field of the photometer, he lighted them both at 

 the same time; and after having caused them to burn with precisely the same 

 degree of brightness just one complete hour, he extinguished them both, and 

 weighing them a 2d time, 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 100 is to 129. 



In order to ascertain the relative consumption of olive oil and rape oil, in the 

 production of light, 2 lamps, like that just described, were used; and the ex- 

 periment being made with all possible care, the consumption of olive oil appeared 

 to be to that of rape oil, in the production of the same quantity of light, as 12g 

 is to 125. The experiment being afterwards repeated with olive oil, and very 

 pure linseed oil, the consumption of olive oil appeared to be to that of the linseed 

 oil as 12Q to 120. The experiment being twice made with olive oil, and with a 

 tallow candle; once when the candle, by being often snuffed, was made to burn 

 constantly with the greatest possible brilliancy, and once when it was suffered to 

 burn the whole time with a very dim light, owing to the want of snuffing, the 

 results of these experiments were very remarkable. When the candle burned 

 with a clear bright flame, the consumption of the olive oil was to the con- 

 sumption of the tallow as 129 is to 101 ; but when the candle burnt with a dim 

 light, the consumption of the olive oil was to the consumption of the tallow as 

 129 is to 229. So that it appeared from this last experiment, that the tallow, 

 instead of being nearly as productive of light in its combustion as bees wax, as 

 it appeared to, be when the candle was kept constantly well snuficd, was now, 

 when the candle was suffered to burn with a dim light, by far less so than oil. 

 But this is not all; what is still more extraordinary is, that the very same candle. 



