88 THE EEASON WHY. 



' Dost thou know the balancings of the clouds, the wondrous works of him 

 which is perfect in knowledge." JOB xxxvn. 



350. Why aro star-lit nights usually colder than cloudy 

 nights ? 



Because heat is radiated, from the earth, and passes away into 

 the utmost regions of the atmosphere. 



351. Why is there little dew under branches of thick 

 foliage ? 



Because the foliage acts as a screen, which prevents the radiated 

 heat of the earth from passing away. 



352. Why is there no dew formed on windy nights ? 

 Because, as winds generally consist of dry air, they absorb and 



bear away the atmospheric moisture. 



353. Why are valleys and low places chiefly subject to 

 dew? 



Because the elevated lands around them prevent the disturbance 

 of the air in which the moisture is held. 



354. What bodies are most likely to be covered with dew ? 

 All bodies that are good radiators of heat, such as wool, swans- 

 down, grass, leaves of plants, wood, &c. 



355. What bodies are likely to receive little dew ? 



All bad radiators of heat, such as polished metal surfaces, 

 smooth stones, and polished surfaces generally. Dew will be found 

 to lie more abundantly upon rough and woolly leaves than upon 

 smooch ones. 



356. At what period of the night is the largest amount of 

 dew usually formed ? 



It is generally supposed that dew is formed most copiously in the 

 mornings and evenings. But such is not the case. It is deposited 

 at all hours of the night, but most plentifully after midnight. 



357. Why is dew formed most plentifully after midnight ? 

 Because, as radiation has been going on for some time, the 



temperature of the earth, ard of various bodies upon it, has 

 been considerably reduced. 



