Heat 



119 



FIG. 58. Convection currents carrying the heat of the stove about the room. 



work the same way carry heat from one place to 

 another like this, we say that the heat has traveled 

 by convection. 



Since heat is so often carried to us by convection, 

 by warm winds, warm air from the stove, warm ocean 

 currents, etc., it seems as if air must be a good con- 

 ductor of heat. But if you shut the air up into many 

 tiny compartments, as a bird's feathers do, or as the 

 hair on an animal's back does, so that it cannot circulate, 

 the passage of heat is almost completely stopped. When 

 you use a towel or napkin to lift something hot, it is 

 not so much the fibers of cotton which keep the heat from 

 your hand; it is principally the very small pockets of 

 air between the threads and even between the fibers 

 of the threads. 



