UNIT V 

 HOW WE USE HEAT 



PREVIEW 



Have you ever thought how important a part heat plays 

 in your life? Ancient peoples, Babylonians, Aztecs, and 

 our American Indians, worshiped the sun because it gave 

 them heat and warmth in winter and provided for their 

 crops in summer. Probably fire has been more wor- 

 shiped than any other element in nature. The use of fire 

 must have been a great discovery to ancient people. No- 

 body knows how man first got it. The first fire may have 

 come from lightning striking a tree, it may have come from 

 a chance focusing of the sun's rays through a rounded 

 quartz pebble, it may have come from an eruption of hot 

 lava from a volcano, it may even have come as the boy 



The artist has shown some primitive people worshiping fire. What do you know 

 about fire worshipers ? From a mural in the Library of Congress. 



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