of the Light emitted by Luminous Bodies. 37 



In order to ascertain the relative consumption of 

 olive oil and rape oil in the production of light, two 

 lamps like that just described were made use of; and, 

 the experiment 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 

 129 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 129 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 suf- 

 fered 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 consump- 

 tion of the tallow as 129 is to 101 ; but, when the 

 candle burned 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 beeswax, as it appeared to 

 be when the candle was kept constantly well snuffed, 

 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, burning with a long wick 

 and a dim light, actually consumed more tallow than 

 when, being properly snuffed, it burned with a clear, 

 bright flame, and gave near three times as much light / 



