of the Light emitted by Luminous Bodies. 21 



field of the photometer, when they were placed at 

 the distance of 60.8 inches from that field. One of 

 the candles being now taken away and extinguished, 

 the other was brought nearer to the field of the instru- 

 ment, till its light was found to be just able, singly, to 

 counterbalance the light of the lamp ; and this was 

 found to happen when it had arrived at the distance 

 of 434 inches. 



In this experiment, as the candles burned with equal 

 brightness, it is evident that the intensities of their 

 united and single lights were as 2 to i, and in that 

 proportion ought, according to the assumed theory, 

 the squares of the distances, 60.8 and 43.4, to be ; and 

 in fact 60.8^^=3696.64 is to 43.4^^=1883.56 as 2 is 

 to I very nearly. 



Again, in another experiment (No. 2), the distances 

 were : — 



With two candles = 54 inches. Square = 2916. 

 With one candle = 38.6 = 1489.96 



Upon another trial (Experiment No. 3) : — 



With two candles = 54.6 inches. Square = 2981.16 

 With one candle := 39.7 = 1576.09 



And in the 4th experiment : — 



With two candles = 58.4 inches. Square = 3410.56 

 With one candle =42.2 =1780.84 



And taking the mean of the results of these four 

 experiments : — 



Squares of the distances. 

 With two candles. With one candle. 



4) 13004.36 4) 673045 



Means 3251.09 and 1682.61 



which again are very nearly as 2 to i. 



