132 GENERAL SCIENCE 



2. What are the twa common causes of change in atmospheric pressure? 



What is the reason for forecasting rain when there is a marked fall in the 

 mercury of the barometer? 



3. What is true (a) of the relative weights of dry and moisture-laden air; 



(b) of the capacity of air to hold moisture as its temperature rises? 

 What are the relative densities of water vapor and of air? 



4. What is meant by the heat equator? What is its location relative to the 



earth's equator? Account for its shifting position. 



5. Discuss the conditions that give rise to a more or less constant "low 

 pressure" along the heat equator. 



6. What is an explanation of the heavy rainfall accompanying the migration 

 of the heat equator north and south, and the recurrence of the rainy 

 seasons in the Tropics? Under what conditions may there be only cloud 

 formation as moisture-laden air rises? 



7. Give a possible explanation (a) for the origin of the highs; (b) for their gen- 

 erally eastward motion across the United States. 



8. Account for the fact that any wind moving northward in the northern 

 hemisphere is deflected east of north, becoming a southwest rather than a 

 south wind. In what direction do winds in the northern hemisphere move 

 about a low as regards the direction in motion of clock hands? 



9. How is the cooling of air as it rises largely to be accounted for? 



10. What condition of atmosphere is supposed to exist within the funnel of a 

 tornado? Why is this? 



11. What is a plausible explanation for the increase (or decrease) in violence 

 of a tornado? Why does a tornado after a time cease to exist as a destruc- 

 tive storm? 



12. Distinguish between a cyclone and a tornado. 



