22 



GENERAL SCIENCE 



Things to Remember about Dew and Frost. No dew forms 

 during cloudy nights; therefore clouds will prevent frost, because 

 they act as a blanket, keeping the heat of the earth in. 



Neither dew nor frost will form on windy nights since the wind 

 does not give the air time to cool and drop its moisture near the 

 earth. 



Dew will form on clear nights, and, if the night is cold, frost is 

 sure to form, since the heat of the earth escapes quickly. Very 

 little dew will form on the tops of trees, but a great deal will form on 



FIG. 11. Why is the farmer able to raise late vegetables on the hillside without 

 danger of the plants being killed by early frost? 



grass. The reason that dew forms so readily on grass is that vege- 

 tation radiates heat more rapidly, and hence cools earlier in the 

 evening. 



More dew will form on a cold night than on a warm night. 



Dew forms readily on faucets, ice pitchers, cellar walls, grass, 

 and other objects which give up their heat quickly. 



More dew will form on the blade of a hatchet than on the wooden 

 handle because the wooden handle does not cool off as rapidly 

 as the metal blade. 



Frost will form in the valley and on top of the hill, while 

 the hillside will be free from frost. Cold air is heavy, and, like 



