ELEMENTS OF GENERAL SCIENCE 



56. 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. 33). 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 wax. 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 one may observe that 

 the burning is not taking place imme- 

 diately at the surface of the wick. It is 

 apparent that there are several parts to 

 the flame, as shown in the figure. The 

 burning occurs chiefly in the outer part 

 of the flame. 



That there is a gas in the flame may 

 be easily proved. Place a small tube so 

 that the end shall be in the center of the 

 flame, and try to light the other end (fig. 34). If this is prop- 

 erly done, we shall have a small gas flame burning at the end 

 of the tube, some distance from the candle flame. If the end 

 of the tube is not placed in the center of the flame, but at the 

 surface, gas that can be burned does not enter the tube. This 

 is because gas is burning at the surface of the flame. If a large 

 piece of paper is held across the widest part of the flame, the 

 paper directly above the center of the flame will not at first 



FIG. 33. The candle 

 flame 



Note the general form 



of the flame, the light 



outer part, and the 



dark center 



