THE REASON WHY. 65 



And yet I say unto you, that even Solomon, in all his glory, was not arrayed 

 like one of these." MATT. vi. 



or none at all. Siir.ilar experiments may be tried with reference to the conden- 

 sation of dew, &c. And it will be uniformly found that the colour of a body 

 materially affects its powers of absorption and of radiation} 



229. Wily do we know that these effects are not the result 

 of light? 



Because they would occur, in just the same order, in the absence 

 of light. 



230. Wliy are dark coloured dresses usually worn in 

 winter, and light in summer ? 



Because black absorbs heat, and therefore becomes warm ; while 

 ight colours do not absorb heat in the same degree, and therefore 

 they remain cool. 



231. Why do iron articles, even when near fire, usually 

 feel cool ? 



Because they are bad absorbers, and do not take up heat freely, 

 unless they are in contact with a hot body. 



232. How is heat diffused through the atmosphere ? 



By convection. The warmth radiating from the surface of the 

 earth warms the air in contact with it ; the air expands, and becom- 

 ing lighter, flies upwards, bearing with it the caloric which it holds, 

 and diffusing it in its course. 



233. Sow do the waters of the ocean become heated? 

 Chiefly by convection. Nearly all the heat which the sun sheds 



upon the ocean is borne away from its surface by evaporation, or is 

 radiated back into the atmosphere. But the ocean gathers its heat 

 by convection from the earth. It girdles the shores of tropical 

 lands where, being warmed to a high degree of temperature, it sets 

 across the Atlantic from the Gulf of Mexico, and exercises an 

 important influence upon the temperature of our latitude. 



234. What is the cause of winds ? 



Currents of air, and winds, are the result of convection. The air, 

 heated by the high temperature of the tropics, ascends, while the 

 colder air of the temperate and the frigid zones Hows towards the 

 equator to supply its place. 



