CHAPTER XXIX 



METHODS OF HEATING BODIES 



How are bodies heated? Put the end of an iron 

 poker into a bed of glowing coals, or the end of an iron 

 rod in the flame of an alcohol lamp. Allow it to remain 

 fifteen or twenty minutes. Is it hot at any point except 

 where it was surrounded by the fire? How far from this 

 point can you detect heat by touching it? What then 

 must have taken place in the piece of iron? The heat 

 must have traveled slowly along from the part that was in 

 the fire to the other parts. When heat travels from one 

 particle of a body to another in this way we say that the 

 body is heated by conduction. How is a flatiron heated ? 

 The handle of a skillet or stewpan? 



Will heat travel by conduction equally well in all kinds 

 of material ? Procure a piece of a small branch of a tree 

 about as large around and as long as the poker or iron rod 

 used in the last experiment. Trim oft all the twigs. Place 

 this and the poker side by side in the bed of coals or in the 

 flame of the alcohol lamp. Leave for ten minutes. Is 

 the wood hot enough to burn ? Is it as hot two inches from 

 the heated end as the iron was? How far from the end 

 can you detect heat in each? What do you conclude as 

 to the power wood has to conduct heat compared with that 

 of iron? Why are wooden handles placed on iron and 

 steel pokers, and on some cooking utensils ? 



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