218 RADIATION. 



Q,. Why does the STEAM of a RAILWAY 

 BOILEE often pour down, like fine rain, when the 

 steam is " let off ?" 



A. The steam from the steam-pipe 

 (when the air is cold) is condensed by 

 contact with the chill air, and falls like 

 fine rain. 



Q. Why is there LESS DEW when the WIND is 

 EASTERLY, than when the wind is WESTERLY ? 



A. Easterly winds cross the con- 

 tinent of Europe, and, (as they pass over 

 land) are dry and arid; but westerly 

 winds cross the Atlantic Ocean; and 

 (as they pass over water) are moist and 

 full of vapour. 



Q. How does the DRYNESS of an eastern wind 



PKEVENT DEW-FALLS? 



A. As the easterly winds are dry, 

 they imbibe the moisture of the air ; and, 

 therefore, there is very little left to be 

 condensed into dew. 



Q. How does the MOISTNESS of a western wind 

 PROMOTE dew-falls ? 



A. As the westerly winds are satu- 

 rated with vapour, they require a 

 very little reduction of heat to cause a 

 copious deposition of dew. 



