of the Light emitted by Luminous Bodies. 39 



nine times more at Munich than the same quantity of 

 light produced by burning rape oil in an Argand's 

 lamp. 



Of the Transparency of Flame. 



To ascertain the transparency of flame or the meas- 

 ure of the resistance it opposes to the passage of 

 foreign or extraneous light through it, I placed before 

 the photometer, over against the standard lamp, two 

 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, I 

 found that, when their distances from the field of the 

 photometer were the same, the intensity of the illumi- 

 nation 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 three and even when four candles 

 were made use of in the experiment, instead of two. 



I even caused a lamp to be constructed with nine 

 round wicks, placed in a horizontal line, and just so 

 far asunder as to prevent their flames uniting, and no 

 farther. And I found, upon repeating the experiment 

 with this lamp, that the result was much the same as 

 with the candles ; the intensity of the illumination at 

 the field of the photometer being very nearly the same, 

 whether these nine lights were placed so as to cover 

 and pass through each other, or not. 



But I afterwards found means to demonstrate the 

 very great transparency of flame by a still more simple 

 experiment. Suspecting that the only reason why 

 bodies are not visible through a sheet of vivid flame is 



