184 



FUELS AND THEIR USES 



No air inlet ; 6, No air out- 

 let ; c, Has both inlet and 

 outlet. This gives a good 

 draft. 



goes out. Now cover the lamp chimney with a piece of 

 cardboard and bring it over the lighted candle again, but 

 leave an open space under the chim- 

 ney. Again the candle goes out. 

 Light the candle and place the 

 chimney over it, leaving the chim- 

 ney open at both top and bottom. 

 The candle burns. 



A study of the burner of a kero- 

 sene lamp shows that air passes in, 

 as in the case of the candle, under- 

 neath the flame, and passes up out 

 of the top of the chimney. By holding the hand, or by 

 placing a small light object over the top of the chimney, 

 the passage of air is noticed. The burner of a lamp regu- 

 lates the air supplied to 

 the flame, which goes 

 out if the air supply is 

 cut off, as was shown in 

 the case of the candle. 

 Evidently a current of 

 air is necessary to make 

 fire burn. These cur- 

 rents which are in circu- 

 lation after the fire starts 

 are known as convection 

 currents, and as we shall 

 see in a moment, are im- 

 portant factors in heat- 

 ing our homes. In order 

 to start a fire in the kitchen stove or open fireplace, we 

 put in a piece of paper and cover it with some shavings 



How air circulates in the common oil lamp. 

 (After Clark.) 



