EXERCISES 243 



20 inches of rain in a year, and is, therefore, considered unfit for farm- 

 ing without irrigation (c/. 42 and 297). The rainfall in Florida and 

 on the Gulf coast is over 60 inches a year. The sea coast of the state 

 of Washington has up to 100 inches. These abundant rains are 

 brought by warm, moist, ocean winds, which are cooled as they pass 

 over the land. In the Plains Region, just east of the Rocky Mountains, 

 the annual rainfall is below 20 inches; in the Nevada Desert, just east 

 of the Sierras, it is less than 5 inches. 



The most wonderful rainfall in the world is in India, where the 

 average is 500 inches a year. This enormous amount is brought by 

 the southwest winds (monsoons) from the heated Indian Ocean, as 

 they ascend the land to the tops of the Himalayas. Beyond the 

 mountains the monsoon is a dry wind, and the plateau of Thibet, over 

 which it passes, is largely a desert. 



273. Exercises. 



1 . Does the color of the soil have anything to do with the amount 

 of heat it can absorb? Why does the snow under specks of dirt melt 

 more rapidly than the clean snow beside it? Why does snow under a 

 heap of dirt melt so slowly? 



2. Why does a high mountain top exposed to the sun become very 

 much hotter in the daytime than land in the valleys, but at night very 

 much colder? 



3. A balloon that is at a certain height during the night usually 

 takes a sudden leap skyward at sunrise. Explain why. 



4. Why does covering a plant at night prevent it from being frost- 

 bitten? 



5. Would you feel any wind if you were in a region from which an 

 air current was ascending? Why? 



6. Why is the seashore of a country cooler in summer and warmer in 

 winter than the interior? 



7. Suppose that air containing moisture rises and expands until it 

 is cooled below the dew point; what effect does the condensing of its 

 moisture have upon its temperature (c/. 70)? 



8. Suggest why a fog is formed more readily in a smoky atmosphere 

 than in a clear one. 



