COMBUSTION. , 305 



duce an intense action in a body said to be combustible ; 

 it burns, a chemical action of the most energetic 

 character is in progress, the elements which constitute 

 the combustible body are decomposed, they unite with 

 some other elementary principles, and new compounds 

 are formed. A body burns it is entirely dissipated, or 

 it leaves a very small quantity of ashes behind uncon- 

 sumed, but nothing is lost. Its volatile parts have 

 entered into new arrangements, the form of the body is 

 changed, but its constituents are still playing an 

 important purpose in creation. 



The ancient notion that fire was an empyreal element, 

 and the Stahlian hypothesis of a phlogistic principle on 

 which all the effects of combustion depended,* have 

 both given way to the philosophy of the unfortunate 

 Lavoisier which has, indeed, been modified in our own 

 times who showed that combustion is but the develop- 

 ment of heat and light under the influence of chemical 

 combination. 



Combustion was, at one period, thought to be always 

 due to the combination of oxygen with the body burn- 

 ing, but research has shown that vivid combustion may 

 be produced where there is no oxygen. The oxidizable 

 metals burn most energetically in chlorine, and some of 

 them in the vapour of iodine and bromine, and many 

 other unions take place with manifestations of incandes- 

 cence. Supporters of combustion were, until lately, 

 regarded as bodies distinct from those undergoing com- 

 bustion. For example, hydrogen was regarded as a 



* Stahl, taking up the obscure notions of Becher and Van Hel- 

 mont, supposed the phenomena of combustion to be due to 

 phlogiston. He imagined that by combination with phlogiston, a 

 body was rendered combustible, and that its disengagement 

 occasioned combustion, and after its evolution there remained 

 either an acid or an earth ,: thus sulphur was, by this theory, sup- 

 posed to be composed of phlogiston and sulphuric acid, and lead 

 of the calx of lead and phlogiston, &c. 



