216 RADIATION. 



A. Because the hot breath is con- 

 densed by the cold glass ; and, therefore, 

 covers it with a thick mist. 



Q. Why do WALLS stand thick with WET in 

 a sudden THAW ? 



A. The walls (being thick) cannot 

 change their temperature so fast as the 

 thin air can ; and, therefore, they retain 

 their cold after the thaw has set in. 



Q. How does RETAINING their COLD account 

 for their being so WET ? 



A. As the vapour of the warm air 

 touches the cold wall, it is chilled and 

 condensed into water, which sticks to the 

 wall, and sometimes trickles down in 

 little streams. 



Q. Why does a thick WELL-BUILT HOUSE 

 contract more DAMP of this kind, than an ORDINARY 

 one ? 



A. Because the walls are much 



thicker ; and (if the frost has penetrated 



far into the bricks) it takes a long time 



to reduce them to the same temperature 



as the air. 



Q. Why are BANISTERS, &c. DAMP after a 

 THAW ? 



