172 SCIENCE OF COMMON THINGS. 



Use of white dresses in summer. Coldness of high mountains. 



Because bright metal does not absorb heat, but re- 

 flects it ; and (as the heat is thrown off from the sur- 

 face of 'bright metal by reflection) therefore a new ket- 

 tle takes a longer time to boil. 



Reflects heat that is, throws it off. 



1135 Why do persons wear white dresses in summer-time f 



Because white throws off the heat of the sun by re- 

 flection, and is a very bad absorbent of heat ; in con- 

 sequence of which w r hite dresses never become so hot 

 from the scorching sun as dark colors do. 



1136 Why do persons not wear white dresses in winter-time ? 



Because white will not absorb heat like black and 

 other dark colors ; and therefore white dresses are not 

 so warm as dark ones. 



Why are shoes hotter for being dusty f 



Because dull, dusty shoes will absorb heat from the 

 sun, earth, and air ; but shoes brightly polished throw 

 off the heat of the sun by reflection. 



1138 Why do not the solar rays, even in the hottest day, melt the snow 

 upon the tops of high mountains, which are nearer to the sun than tlie kvel 

 portions of the earth ? 



Because they only heat those bodies which can alt- 

 sorb their warmth, as the rough surface of the earth. 

 The snow is indeed struck by the rays of the sun, but 

 being a white and shining body, it reflects them, and 

 remains cold. 



1139 Why does it always freeze on the top of a high mountain ? 



1. Because air is heated by contact with the earth's 

 surface more than by solar rays which pass through it : 

 as a mountain-top affords very small surface for such 

 contact, it remains intensely cold ; and 



2. When air flows up the side of a mountain, it ex- 

 pands from diminished pressure ; and consequently 

 absorbs heat from surrounding objects. 



Karefied air can hold more latent heat than dense air can. 



11SO What is the difference between conducting heat and absorbing 

 heat? 



To conduct heat is to transmit it from one body to 



