VOL. LXXXIV.3 FHILOSOPHICAL TEANSACTIONS. 373 



burning with a long wick, and a dim light, actually consumed more tallow than 

 when, being properly snuifed, it burned with a clear bright flame, and gave 

 near 3 times as much light! 



To be enabled to judge of the relative quantities of light actually produced by 

 the candle in the 2 experiments, it will suffice to know, that in order to counter- 

 balance this light at the field of the photometer, it required, in the former ex- 

 periment, the consumption of 141 parts, but in the latter only the consumption 

 of 64 parts of olive oil. But in the former experiment 1 10 parts, and in the 

 latter 1 14 parts of tallow were actually found to be consumed. These parts were 

 .8192ths of a Bavarian pound. From the results of all the foregoing experi- 

 ments it appears, that the relative expence of the under-mentioned inflammable 

 substances, in the production of light, is as follows. 



Equal parts 

 in weight. 



Bees wax. A good wax candle, kept well snufFed, and burning with 



a clear, bright flame, 100 



Tallow. A good tallow candle, kept well snufFed, and burning with a 



bright flame, 101 



The same tallow candle, burning very dim for want of snuffing, .... 229 



Olive oil. Burnt in an Argand's lamp, 110 



The same burnt in a common lamp, with a clear bright flame, with- 

 out smoke, 129 



Rape oil. Burnt in the same manner, 125 



Linseed oil. Likewise burnt in the same manner, 120 



8th. On the Transparency of Flame. 

 To ascertain the transparency of flame, or the measure of the resistance it 

 opposes to. the passage of foreign or extraneous light through it, he placed before 

 the photometer, over against the standard lamp, 2 burning wax candles, well 

 trimmed; and putting them near together, sometimes by the sides of each other, 

 and sometimes in a straight line behind each other, he found that when their dis- 

 tances from the field of the photometer were the same, the intensity of the illu- 

 mination was to all appearance the same, whether the light of the one was made 

 to pass through the flame of the other, or not. And the same held good, with 

 very little variation, when 3, and even when 4 candles were used in the experi- 

 ment, instead of 2. Count R. even caused a lamp to be constructed with 9 

 round wicks, placed in an horizontal line, and just so far asunder as to prevent 

 their flames uniting, and no farther. And found, on repeating the experiment 

 with this lamp, that the result was much the same as with the candles; the in- 

 tensity of the illumination at the field of the photometer being very nearly the 

 same, whether these 9 lights were placed so as to cover, and pass through each 

 other, or not. 



