18 Introduction to the Study of Science 



ance of the sky, (2) clouds, (3) winds, (4) temperature, (5) humidity, 

 and (6) pressure. 



Official forecasts are made and published by the United States 

 Weather Bureau. 



Weather maps show atmospheric temperatures by isothermal 

 lines, and pressures by isobaric lines. 



Air exerts at sea level an average pressure of 14.7 pounds per 

 square inch, called one atmosphere. 



The pressure of the air is due to its weight. 



A barometer is an instrument for measuring the pressure of the air. 



The suction pump depends on the pressure of the air to force the 

 water into its cylinder. 



An aneroid barometer, made to record the changes in atmospheric 

 pressure, is called a barograph. 



REVIEW QUESTIONS 



1. What is the importance of air to living things? 2. What are 

 some of the special things one mentions when discussing the weather? 

 3. Why are we concerned in forecasting the weather? 4. What aids 

 do we have in making local observations? 5. What should supple- 

 ment local observations to make forecasts accurate? 6. What are 

 the conditions of the atmosphere upon which forecasts are based? 



7. How are daily forecasts made in the Federal Weather Bureau? 



8. How are the forecasts communicated to the people? 9. Of what 

 practical use is their publication? 10. Explain how weather maps 

 are prepared. 11. What are the sources of the information used by 

 the Weather Bureau in preparing maps and forecasts? 



12. How are temperatures indicated on weather maps? 13. What 

 is an isotherm? 14. What is the relation of isotherms to lows and 

 highs? To parallels of latitude? 15. How is the pressure of the 

 atmosphere shown on weather maps? 16. What is an isobar? 

 17. What two observations are recorded on weather maps, not as 

 actually made but as they would be at sea level? 18. In inter- 

 preting weather maps what correction must you make to obtain 

 actual pressures and temperatures of places above sea level? 



19. What experience may one have of change in pressure with rapid 

 change of altitude? 20. Why do we not ordinarily feel the pressure 

 of the atmosphere? 21. Why do many people have "mountain 

 sickness" when they reach high altitudes? 22. In what ways can 

 the fact of air pressure be demonstrated? 23. How may air be 

 weighed? What is the approximate weight of one cubic foot of air? 



