64 ELEMENTS OF GENERAL SCIENCE 



acquaintance, we shall study the flame of a candle in its 

 relation to the air. 



If a candle is thrust into a lamp chimney which is held 

 in an upright position, the flame will burn more brightly 

 and steadily than in the open air; but if the lower end 

 of the chimney is closed by the hand, the flame becomes 

 smoky, flickers, and possibly is extin- 

 guished. In the first case the heat of the 

 flame warmed and expanded the air in 

 the chimney, thus causing an upward cur- 

 rent of air (Chapter I), so that the flame 

 was better supplied with fresh ah? than 

 when it was in the open. When the hand 

 was placed across the bottom of the chim- 

 ney, however, the upward current of air 

 was interrupted and the supply to the 

 flame was so much reduced that burning 

 was no longer possible. 



66. A burning candle. When a candle is 

 lighted, the flame burns at the top of the 

 wick but does not come down the wick 

 to the solid part of the candle (fig. 35). 

 The heat soon forms a cup in the top of 

 the candle by melting the center of it. 

 This cup is filled with melted tallow or 

 \vax. The melted wax is absorbed by the 

 wick and travels upward in it, just as ink 

 is absorbed by blotting paper and spreads through it. As the 

 melted wax goes up the wick and gets closer to the flame, 

 it gradually becomes hotter and finally begins to burn. The 

 point at which it gets hot enough to burn is marked by the 

 bottom of the flame. 



The melted wax or oil really gets so hot before it burns 

 that it changes from a liquid into a gas and burns as it is 

 passing away from the wick. By looking closely at a flame 



FIG. 35. The candle 

 flame 



Note the general form 



of the flame, the light 



outer part, and the 



dark center 



