UNIT III 

 LIVING IN AN OCEAN OF AIR 



PREVIEW 



It is commonly said that " we live in an ocean of air." 

 But you never see air as you do water and there is certainly 

 no appearance of an ocean when you are in a room con- 

 taining air, or even when you go for a hike in the open. 

 What do we mean by this statement ? We know that air 

 exists, for we feel it when the wind blows ; it holds up our 

 kites, sails our boats, cools us when we are warm, and when 

 it is heated, warms us when we are cold. In tires it holds 

 up our automobiles. It works our compressed-air devices ; 

 turns wind-mills, stops trains by air brakes, and allows 

 people to live and work under water in the caisson and 

 diving bell, Sometimes in storms it blows down houses 

 and wrecks ships. And, although we may not know just 

 how we use it, air is necessary for life because living 

 things breathe it. Have not Piccard and other high 

 altitude explorers taken oxygen of the air with them into 

 the stratosphere, and has not Beebe taken it into the 

 ocean depths in order to exist there? 



It has taken a good many people a long, long time to 

 find out much about air. While the Greek philosophers 

 knew something about it and even invented some devices 

 that made use of the fact that air had weight, it was not 

 until the time of Galileo 1 (1564-1642) that it was proved 

 that air had weight. Galileo did this by first weighing a 

 hollow copper ball and then forcing air into it until the 

 air was compressed in the ball. He weighed it a second 



Galileo (gal'I-le'o). 

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