238 CONVECTION. 



Q. How should a RED-HOT POKER be carried 

 so as not to BURN our fingers ? 



A. With the hot end upwards; 

 because then the air (heated by the 

 poker) would not pass over our hand to 

 scorch it. 



Q. Why is a POKER (resting on the FENDER) 

 COLD ; but if it leans against the STOVE, intensely 

 warm? 



A. The poker is an excellent con- 

 ductor ; while, therefore, it rests 

 against the hot stove, the heat of the 

 stove is conducted into the poker ; but 

 when it rests on the fender, it does not 

 come in contact with the hot stove. 



Q. Why does it feel so COLD, when it rests on 

 the FENDER ? 



A. Not being so warm as our hand, 

 it imbibes the heat from it with such 

 rapidity, that our loss of heat is palpable, 

 and produces the sensation of coldness. 



Q. Why are FLUES (which are carried through 

 a church or room) always BLACKENED with BLACK 



LEAD ? 



A. In order that the heat of the flue 

 may be more readily diffused throughout 

 the room. Black lead radiates heat more 

 freely than any other known substance. 



