SCIENCE OF COMMON THINGS. 173 



Conduction of heat. How fanning cools. 



another through a conducting medium. To absorb heat 

 is to suck it up, as a sponge sucks up water. 



1131 Give me an example ? 



Black cloth absorbs, but does not conduct heat / thus, 

 if black cloth be laid in the sun, it will absorb the rays 

 very rapidly ; but if one end of the black cloth be 

 made hot, it w r ould not conduct the heat to the other 

 end. 



113S Are good conductors of heat good absorbers also f 



No ; every good conductor of heat is a lad absorber 

 of it ; and no good absorber of heat can be a good con- 

 ductor also. 



1133 Is iron a good absorber of heat f 



No ; iron is a good conductor, but a very bad ab- 

 sorber of heat. 



1134 If a piece of brown paper be submitted to the action of a burning- 

 glass it will catch fire much sooner than a piece of white paper would : ex- 

 plain the reason. 



Because white paper reflects the rays of the sun. or 

 throws them back ; in consequence of which it appears 

 more luminous, but is not so much heated as dark 

 brown paper, which absorbs the rays, and readily be- 

 comes heated to ignition. 



1135 How does the ceaseless change of air tend to decrease the warmth 

 of a naked body ? 



The air (which cases the body) absorbs as much heat 

 from it as it can, while it remains in contact ; bein^ 

 then blown away, it makes room for a fresh coat of 

 air, which readily absorbs more heat. 



Use Does the air which encases a naked body become (by contact) as 

 warm as the body itself? 



It would do so, if it remained motionless ; but, as it 

 remains only a very short time, it absorbs as much heat 

 as it can in the time, and passes on. 



1137* Why does fanning the face in summer make it cool f 



Because the fan puts the air in motion, and makes 

 it pass more rapidly over the face ; and (as the tem- 

 perature of the air is usually lower than that of the 



8* 



