EXPERIMENTS 



RELATIVE INTENSITIES OF THE LIGHT EMITTED 

 BY LUMINOUS BODIES. 



BEING employed in making a number of experi- 

 ments to determine, if possible, the most eco- 

 nomical method of lighting up a very large workhouse, 

 or public manufactory, which had been erected in the 

 suburbs of Munich under my direction, a method 

 occurred to me for measuring the relative quantities 

 of light emitted by lamps of different constructions, 

 candles, etc., which is very simple, and which I have 

 reason to think perfectly accurate. 



Let the two burning candles, lamps, or other lights 

 to be compared, A and B, be placed at equal heights 

 upon two light tables or movable stands, in a dark- 

 ened room ; let a sheet of clean white paper be spread 

 out equally, and fastened upon the wainscot or side of 

 the room, at the same height from the floor with the 

 lights ; and let the lights be placed over against this 

 sheet of paper, at the distance of 6 or 8 feet from it, 

 and 6 or 8 feet from each other, in such a manner 

 that a line drawn from the centre of the paper, perpen- 

 dicular to its surface, shall bisect the angle formed by 

 lines drawn from the lights to that centre ; in which 



