NATUBE-STUDY LESSONS. 179 



3. When you see clouds moving in one direction and 

 at the same time other clouds moving in a different 

 direction, what do you infer respecting currents of air? 



4. If a cold current of air comes against a warm 

 current, what may happen to the vapor in the latter 

 current ? 



The vapor may be condensed into mist particles, or into minute ice 

 crystals, in either case forming clouds. In hot midsummer weather, many 

 of the clouds you see are banks of little ice crystals. When a cloud lies on 

 the ground it is called a fog. 



5. {a) Make observations on the conditions of the air 



as to pressure and temperature when we have 

 frequent thunderstorms. 



(fi) Compare these with those of the temperate 

 seasons when cloudiness gradually thickens 

 all over the sky and settles into a day's 

 steady rain. 



6. Note the direction in which the wind usually blows 

 in each of the cases referred to in No. 5. 



7. Observe rain-drops and describe their shape. 



8. Note the difference in size between the drops when 

 it is raining hard and raining gently; also during a 

 thunderstorm and during a day's steady rain. 



9. Observe and describe the different ways in which 

 rain falls and note the different sounds it makes. 



10. What becomes of the water after it falls to the 

 earth ? 



11. What arc the uses of rain? 



