76 FIRST YEAR COURSE IN GENERAL SCIENCE 



which heat is distributed more rapidly and through greater 

 distances. Heat passes through air and some other sub- 

 stances in straight lines in every direction. This is radiation. 

 It is by this method that heat passes from the sun to the 



FIG. 32. HOUSE HEATING BY HOT WATER 



1. Why does water rise from a heater in the basement to the second 

 floor? 2. Why is it rising in one part and falling in another, in the radiator 

 at the left? 3. Make a diagram like the right-hand radiator; connect it 

 properly with the rest of the system and indicate the direction of hot and 

 cool water currents. 



earth and to other planets; and from stoves, radiators, and 

 lamps to objects around them. 



If this radiated heat falls upon a body through which it 

 cannot pass, it is absorbed and the temperature of the body 

 rises. The sun's radiations pass through the air, with very 

 little absorption, to the earth, which absorbs the heat and is 

 warmed by it. 



