98 THE EEASON WHY. 



' And it was so : for he rose up early on the morrow, and thrust the fleece 

 together, and wringed the dew out of the fleece, a bowl full of water. 



Because the under surfaces receive the radiated warmth of the 

 earth. 



403. Why are cultivated lands subject to heavier dews 

 than those that are uncultivated ? 



Because cultivation breaks up the hard surface of the earth, and 

 thus its radiating power is increased. 



404. Why is the gravel walls through, a lawn comparatively 

 dry while the grass of the lawn is wet with dew ? 



Because gravel is a bad radiator, but grass is a good radiator. 



405. What benefit results from this arrangement ? 



In cultivated lands, where moisture is required, it is induced by 

 the very necessity which demands it ; while in rocky and barren 

 places, where it would be of no good, dew does not form. 



406. Why does little dew form at the base of hedges and 

 walls, and around the trunks of trees ? 



Because those bodies in some degree counteract the radiation of 

 heat from the earth ; and they also radiate heat from their own 

 substances. 



407. Why do heavy morning dews and mists usually come 

 together ? 



Because they both have their origin in the humidity of the 

 atmosphere. The temperature of the earth having fallen, dew has 

 been deposited ; but, at the same time, the condensation of the 

 vapour in the air has formed a screen over the surface of the earth, 

 which has checked the further radiation of heat, and, consequently, 

 the further formation of dew . The sun rises, therefore, upon an 

 atmosphere charged with visible vapour at the earth's surface, and 

 his first sloping rays, having little poioer to warm the atmosphere, 

 the mist continues visible for some time. 



408. What effect have winds upon the formation of dew ? 



Winds, generally, and especially when rapid, prevent the forma- 

 tion of dew. But those winds that are moist, and contribute to the 

 formation of clouds, indirectly aid the formation of dew through the 



