OF THE LIGHT MANIFESTED IN 

 COMBUSTION. 



WHEN an inflammable substance, in a state of 

 purity, such as wax, tallow, or purified oil, 

 burns with a clear, bright flame, without smoke or 

 smell and without leaving any residuum, the combus- 

 tion is considered as being complete ; and its chemical 

 products, water in a state of vapour and carbonic acid 

 gas, are always pure, and in quantities which are always 

 in a constant ratio when the substance burned is the 

 same. 



Those who consider light as a substance emitted by 

 luminous bodies have been obliged to search for the 

 source of that which is manifested in the combustion 

 of inflammable bodies among those substances which 

 are known to concur in that process. Some have 

 supposed that it is the inflammable substance which 

 furnishes it; others, that it is derived from the air 

 (oxygen gas) employed in the combustion, which gas 

 is supposed to be decomposed ; and of late the pre- 

 vailing opinion among chemists appears to be that it 

 is furnished in part by the inflammable substance and 

 in part by the oxygen. 



If the light manifested in the combustion of inflam- 

 mable bodies were in fact one of the chemical products 

 of that process, as has been supposed, it is most cer- 



VOL. IV. 14 



