SCIENCE OF COMMON THINGS. 165 



Plants requiring the most moisture condense the most dew. 



107*4: Why are substances which radiate the heat most freely always 

 the most thickly covered with dew ? 



Because they are the coldest substances, and there- 

 fore condense vapor most readily. 



107*5 What kind of materials radiate heat most freely f 



Grass, wood, and the leaves of plants radiate heat 

 very freely but polished metal, smooth stones, and 

 woollen cloth part with their heat very tardily. 



1O7*6 Do the kaves of all plants radiate heat equally well? 



No. Rough, woolly leaves (like those of a hollyhock) 

 radiate heat much more freely than hard, smooth po- 

 lished leaves, like those of the common laurel. 



1O7*7* Show the wisdom of the Creator in making grass, the kaves of 

 trees, and all vegetables, excellent radiators of heat ? 



As vegetables require much moisture, and would 

 often perish without a plentiful deposit of dew, the 

 Creator wisely made them to radiate heat freely, so as 

 to chill the vapor (which touches them) into dew. 



1O7*S Will polished metal, smooth stones, and woollen doth readily col- 

 lect dew f 



No. "While grass and leaves of plants are completely 

 drenched with dew, a piece of polished metal or of 

 woollen cloth (lying on the same spot) will be almost 

 dry. 



1O7*9 Why would polished metal and woollen cloth le dry, while grass 

 and leaves are drencJied with deiv % 



Because the polished metal and woollen cloth part 

 with their heat so slowly, that the vapor of the air is 

 not chilled into dew as it passes over them, 



1OSO Why is a gravel walk almost dry wlien a grass-plat is covered 

 fliick with dew ? 



Because grass is a good radiator, and throws off its 

 heat very freely ; but gravel is a very l>ad radiator, 

 and parts w r ith its heat very slowly. 



1O81 Is that the reason why grass is saturated with dew, and the gra- 

 vel is not f 



Yes. When the vapor of warm air comes in contact 

 with the cold grass, it is instantly chilled into dew ; but 



