110 Introduction to the Study of Science 



temperature as it comes from the faucet, close them with the stoppers, 

 and hang by a cord or wire in direct sunlight. Take thermometer 

 readings at intervals of ten minutes. In which can does the water 

 heat more rapidly? At the end of an hour which shows the higher 

 temperature? Which color is thus shown to be the better absorber 

 of heat energy ? 



The effect of color and bright surfaces upon radiation, or the giv- 

 ing up of heat, may be determined by filling the cans with hot water 

 of the same temperature and hanging them in a cool place. Which 

 radiates heat more rapidly? At the end of a given period of time 

 which is the cooler? 



Objects that are black and rough are good absorbers of heat energy ; 

 but they also give up or radiate their heat very rapidly. Smooth, 

 bright, or highly polished articles reject or reflect a large proportion 

 of heat energy and absorb it slowly ; but when they are heated, they 

 radiate heat much more slowly than objects of the other class. A 

 bright stew pan absorbs heat more slowly than a black iron pan. 

 But when the bright pan is hot, it retains its heat better than the 

 iron utensil. Explain why a reflector, such as that used for a lamp, 

 which is exposed to a large part of the heat energy of the light, does 

 not become as hot as the lamp chimney or other objects as near. 



Hence, it maybe stated that ready absorbers are ready radiators, 

 that is, they give up heat rapidly; and slow absorbers are slow 

 radiators, that is, they retain their heat well. Explain the use of 

 aluminum cooking utensils on the basis of these facts. 



Exercise. With these points in mind, explain whether light- 

 colored or dark-colored clothing is better for hot weather wear. Com- 

 pare the advantages of light-colored clothing with those of dark colors 

 for winter weather. Explain the fact that animals in the Arctic 

 regions are usually covered with white fur. Is absorption or radiation 

 of heat more important in this instance ? May the white have other 

 advantages ? 



How does knowledge of the facts studied help in understanding 

 such features of climate and weather as the following : the difference 

 between inland and seacoast climate ; the differences in temperature 

 of land and ocean, of land and sea breezes, and of mountain and valley 

 breezes? If it is helpful in explaining winds, in what way does it 

 account for the distribution of water vapor and rainfall ? Upon what 

 facts do ocean currents depend? 



