DEW. 219 



Q. When is DEW most COPIOUSLY distilled ? 



A. After a hot day in summer or 

 autumn, with the wind in the west. 



Q. Why is DEW distilled most COPIOUSLY after 

 a HOT day ? 



A. Because the surface of the earth 

 radiates heat very freely at sunset; 

 and (becoming thus much colder than 

 the air) chills its vapour, and condenses 

 it into dew. 



Q. Does not AIR radiate heat, as well as the 

 EARTH and its various plants ? 



A. No. The air never radiates heat, 

 nor is the air itself made hot by the rays 

 of the sun. 



Q. How is the AIB made HOT or COLD ? 

 A. By convection oj hot or cold 

 currents. 



Q. What is tmant by "CONVECTION of hot 

 and cold currents ?" 



A. The air (which is heated by the 

 surface of the earth) ascends, warming 

 the air through which it passes. Other 

 air (being warmed in a similar way) also 

 ascends, carrying heat ; till all the air is 

 made hot. 



u 2 



