DEW. 209 



dew, a piece of polished metal, or of 

 woollen cloth (lying on the same spot) 

 will be almost dry. 



Q. Why would POLISHED METAL and WOOL- 

 LEN CLOTH be DRY, while grass and leaves are 

 drenched with DEW ? 



A. Because the polished metal and 

 woollen cloth part with their heat so 

 slowly, that the vapour of the air is not 

 chilled into dew as it passes over them. 



Q Why is a GRAVEL WALK almost DRY, when 

 a grass plat is covered thick with DEW? 



A. Grass, (being a good radiator) 

 throws off its heat very freely ; but 

 gravel (being a very bad radiator) parts 

 with its heat very reluctantly. 



Q. Is that the reason why GRASS is SATURATED 

 with DEW, and the GRAVEL is NOT ? 



A. Yes. When the vapour of 

 warm air comes in contact with the cold 

 Grass, it is instantly chilled into dew ; but 

 as the gravel is not so cold as the grass) 

 e vapour of air is not so freely condensed 

 as it passes over the gravel. 



Q. Why does DEW rarely fall upon hard 

 ROCKS and BARREN lands ? 



T3 



