CONTENTS 



PART I. THE AIR 



PAGE 



CHAPTER I. INTERESTING THINGS ABOUT THE AIR ... 1 



Introduction. Questions for Discussion. Air as material. Some 

 uses of compressed air. Measuring air pressure in tires. Working 

 under water. Weight of air. Air pressure. Measurement of air 

 pressure by barometers. Graduation of the barometer. Altitude 

 and air pressure. Effect of temperature. Thermometers. Some 

 effects of expansion. Convection currents. Stoves, furnaces, and 

 water heaters. Chimneys. Air currents in refrigerators. Impor- 

 tance of air temperature. 



CHAPTER II. AIR AND WATER 21 



Questions for Discussion. Evaporation. Condensation. Amount 

 of water in the atmosphere. Moist and dry air. Reference table 

 of the amount of water in one cubic meter of saturated air at 

 given temperatures. Saturation and the dew point. How to deter- 

 mine whether the air is moist or dry. Variations in relative 

 humidity. Humidity in houses. Humidity and health. 



CHAPTER III. AIR TEMPERATURES AND THE SEASONS . 32 

 Questions for Discussion. How the air is warmed. Seasonal 

 changes of temperature. Effects of changes in the sun's altitude. 

 Length of day and night. Daylight saving. 



CHAPTER IV. THE WEATHER 38 



Questions for Discussion. General statement. Air pressure and 

 winds. Pressures as shown by weather maps. Progression of high 

 and low pressures. Winds about a "low" cyclones. Tem- 

 perature in a cyclone. Humidity in a cyclone. Passage of a 

 cyclone. Weather in anticyclones. Hot and cold waves. Hurri- 

 canes. Thunderstorms. Tornadoes. General circulation of air 

 on the earth. Rainfall in the United States. The United States 

 Weather Bureau. 



CHAPTER V. STRUCTURE OF THE AIR MOLECULAR 

 THEORY 57 



Questions for Discussion. Compressibility of air. Expansion of 

 gases. Diffusion of gases. Some questions regarding gases. A 

 theory about the air. Molecular theory applied to air. Gas pres- 

 sures. Heat, molecular movement, and gas mixtures. Liquids 

 and solids. 



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