UNIT I. THE OCEAN OF AIR IN WHICH WE LIVE 



Did it ever occur to you that you are living at the 

 bottom of a great ocean of air which is far deeper than 

 the deepest ocean of water on earth? In many ways 

 this is similar to an ocean of water: it has great cur- 

 rents like the ocean currents caused by the unequal 

 heating of its parts ; in it, as in the ocean, there are 

 many varieties of living things ; it has tremendous 

 force when moving, as has water ; and it, like water, 

 makes possible one means of transportation and 

 travel. 



For many hundreds of years man has been trying 

 to solve the mysteries about air, and the study is still 

 carried on ; for even after long years of search much 

 remains to be learned about this great blanket which 

 surrounds our earth. Calculations based upon obser- 

 vations indicate that it is between fifty and two hun- 

 dred miles in depth. Small balloons carrying record- 

 ing instruments have reached a height of eighteen 

 miles, while man has gone more than eight miles 

 above the earth's surface in airplanes. In 1932 Pro- 

 fessor Piccard of Belgium reached a height of more 

 than ten miles; in 1933 Settle and Fordney reached 

 an altitude of more than eleven and a half miles. The 

 record is now held by Stevens and Anderson, who 

 ascended 72,395 feet or more than thirteen and a half 

 miles on November 11, 1935. 



Galileo and Torricelli first measured the pressure 

 of the air; Priestley and Lavoisier studied its com- 

 position ; Dumont, Langley, and the Wright brothers 

 learned to travel through it. 



Life is impossible without air because air contains 

 substances which all life must have. Oxygen, which 

 forms a part of the air, is used by all living things, and 

 carbon dioxide is used by plants in food making. We 

 use air in many ways as we go about our daily lives : 

 in automobiles tires for ease of riding; to stop railroad 

 trains, street cars, and buses by air brakes ; in building 

 great buildings, bridges, and tunnels with compressed 



air hammers and drills; to carry mail, express, and 

 passengers in the airplane and dirigible. In fact, air is 

 so much a part of our existence that every one should 

 learn of its secrets and mysteries. The exercises of 

 this unit will guide you in learning these. 



How many of these things about air do you know? 



The purpose of this exercise is to assemble the 

 things you already know about air. It will help you in 

 your study of the things which are to come. Write 

 the answers in your notebook. 



1. Does air have any weight? 



2. How thick is the envelope of air which surrounds 

 the earth? 



3. What is a vacuum? 



4. What are some devices which make use of a 

 vacuum? 



5. What are some machines which make use of 

 compressed air? 



6. How should a room be ventilated to secure best 

 results? 



7. In what ways is air used for the purpose of trans- 

 portation? 



8. In what ways is air of importance to automo- 

 biles? 



9. How does air pressure on top of mountains com- 

 pare with air pressure at the level of the sea? 



10. What is the greatest height to which man has 

 gone by means of airplane or balloon? 



11. Of what importance is air to sound? 



12. How is air used in the construction of bridges 

 and dams? 



13. How is air used in the construction of large 

 buildings? 



14. How is air used on trains, street cars, and 

 buses? 



15. How does a vacuum cleaner work? 



TOPIC 1. WHAT WE KNOW ABOUT AIR 



SUGGESTED PROBLEMS AND QUESTIONS 



1. What is known about the nature of air and 

 the atmosphere? 



2. How can the pressure of air be proved and 

 measured? 



3. What are some of the uses of barometers? 



SUGGESTIONS AND HELPS FOR STUDY 



1. Carefully study the problems in the first column. 

 Are they questions which you have wondered about 

 or in which you are interested? 



2. Perform the experiments. In doing so, be sure 

 to follow directions, observe what happens, and make 

 notes in your notebook. Your instructor will check 

 results after each experiment. 



3. Read carefully the material under this topic. Try 

 to see how the parts fit together to explain the topic. 

 As you read, study the diagrams and pictures. 



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