CONVECTION. 247 



other air succeeds, absorbs more heat, 

 ascends, and gives place to that which is 

 colder ; till the hot iron is cooled com- 

 pletely down. 



Q. How is hot iron cooled by RADIATION ? 



A. While the heat of the iron is 

 being earned off by " convection/' it is 

 throwing off heat (on all sides) by 

 radiation. 



Q. What is meant by RADIATION ? 



A. Heat emitted (in all directions) 

 from any surface, by innumerable rays. 



Q. Why is BROTH COOLED by being left 

 exposed to the AIR ? 



A. Hot broth throws off some heat 

 by radiation; but it is mainly cooled 

 down by convection. 



Q. How is Iwt BROTH cooled down by CON- 

 VECTION ? 



A. The air resting on the hot broth 

 (being heated) ascends ; colder air suc- 

 ceeding absorbs more heat, and ascends 

 also; and this process is repeated, till 

 the broth is made cool. 



Q. V/h'j is hot TEA and BROTH COOLED 



filter, fnr In'iug sTlHRi-n about ; 



