WATER, AND ITS USES 97 



Exercises 



1. When persons climb mountains, or go up into the clouds in balloons, 

 what are the clouds found to be? 



2. Why does not all the water of the atmosphere fall to earth (a) when it 

 is in vapor (gaseous) form; (b) when in minute droplets as in fog? 



3. Why is it that in winter we sometimes can "see our breath?" 



4. Explain the thinning out and disappearance of the clouds of early morn- 

 ing as the sun rises higher and higher. Why is it that at other times as 

 rain continues the clouds break away giving place to clear skies? 



6. Whenever there is an inch of rainfall, (a) what is the number of cubic 

 feet of water that falls per acre of land; (6) how many gallons (231 cubic 

 inches = one gallon) ; (c) how many tons (one cubic foot = 62.4 pounds) ? 



6. Name and describe several forms of clouds. 



7. Aside from rainfall, what important part in nature is served by clouds? 



8. How may an ample supply of water for drink and for cooking purposes 

 be provided on long journeys by ship? In what way may a supply of 

 ice be provided? 



9. What is meant by "humidity" of the atmosphere? What is the exact 

 significance of the term "relative humidity?" 



10. Whence comes the heat, directly or indirectly, for natural distillation? 



11. Be ready to quote and interpret the last stanzas of Longfellow's Rain 

 In Summer. 



12. What may explain in part the refreshing coolness that frequently follows 

 a summer shower? What relation is there between the temperature of 

 soil under a summer sun and the abundance of water in it? Why is 

 this so? 



13. Explain the heating of rooms and buildings by steam as a phenomenon 

 of heat of vaporization. What is true of the temperature of water boiling 

 freely in a tea-kettle as it is heated more and more? Explain. 



14. Explain how the melting of ice and snow, and of the frost in the ground, 

 delays the coming of warm weather in spring time. 



15. What is meant by the heat of fusion? Describe an experiment to explain 

 it. 



16. What is a calorie? What is the value in calories of the latent heat (a) of 

 steam; (6) of ice? 



17. What is the part played by moisture in the atmosphere in equalizing 



throughout the year the temperatures of coast regions? Account for 

 the extremes of temperature of inland arid districts by day and by night. 



SOLUTION, DIFFUSION, ABSORPTION, AND OSMOSIS 



The phenomena of absorption, diffusion, solution, and 

 osmosis are easily understood on the hypothesis that a chief 



