n6 



Common Science 



165. Comets swing around close to the sun, then off again into 



space ; how do they get away from the sun ? 



1 66. When you wish to pour canned milk out, you need two holes 



in the can to make it flow evenly. 



167. Liquid air changes to ordinary air when it becomes even as 



warm as a cake of ice. 



1 68. Skid chains tend to keep automobiles from skidding on wet 



pavement. 



169. A warm iron and a blotter will take candle grease out of your 



clothes. 



170. Candies like fudge and nougat become hard and dry when left 



standing several days open to the air. 



SECTION 20. Conduction of heat and convection. 



Why does a feather comforter keep you so warm ? 

 When you heat one end of a nail, how does the heat get 

 through to the other end ? 

 How does a stove make the whole room warm ? 



Here is a way to make heat run a race. See whether 

 the heat that goes through an iron rod will beat the heat 

 that goes through a glass rod, or the other way round : 



Experiment 41. Take a solid glass rod and a solid iron 

 rod, each about a quarter inch in diameter and about 6 



FIG. 56. The metal balls are fastened to the iron and glass rods with drops 



of wax. 



