CANDLES. 



Fig. 5. 



I 



A * 



corresponding volume of carbonic acid, unless means be provided, 

 which is rarely the case, for other ventilation besides that of the 

 chimney. Hence it arises that per- 

 sons of delicate habits, especially 

 those whose lungs are defective, in 

 such a room, soon become sensible 

 of general uneasiness, and are 

 often affected with headache. 



36. The manner in which the 

 flame of lamps and candles is 

 produced and maintained will 

 require some explanation. 



When a candle is lighted, the 

 heat developed at the extremity 

 of the wick melts the wax or 

 tallow immediately below it, and 

 thus liquefied, it is drawn up 

 through the insterstices of the 

 wick by the force called capillary 

 attraction. When it comes in 

 contact with the flame, it boils, 

 and is converted into vapour, 

 which rises over the wick. This 

 vapour having a very high tem- 

 perature, and exercising a strong 

 attraction for the oxygen* of the 

 surrounding air, enters into com- 

 bination with it, and becoming 

 luminous, forms the flame around 

 and above the wick. "Within the 

 flame arises a constant current of 

 the vapour of the combustible, and 

 outside it currents of air carry to 

 the surface of the flame the oxygen 

 which produces the combustion 

 and the light. The combustible 

 vapour and the oxygen meeting 

 at the surface of the flame, there 

 enter into combination, and the 

 vapour burns. Within the flame 

 no combustion takes place, and no 

 light is produced. 



In fig. 5 the wick and flame are 

 represented. Within the flame 



currents of combustible vapour proceed from the wick to all parts 



205 



