THE EARTH AND ITS NEIGHBORS 413 



to the earth. In 1866 a shower of small meteors fell in 

 the western part of the United States. 



QUESTIONS AND EXERCISES 



1. What evidence can you see that the earth is very old? How 

 were the hills, valleys, and plains made? When were coal, petroleum, 

 limestone, and chalk formed? 



2. What causes the phases of the moon? Why is the moon some- 

 times eclipsed? What causes an eclipse of the sun? 



3. What planets are going around the sun other than the earth? 



4. If you were on the moon, how would the earth appear to you? 



5. What is the nature of a meteor or " shooting star "? Where 

 are they when they are visible? 



