Fig. 2. 



COMMON THINGS. 



THE EARTH. 



Difficulty of observing the earth as a whole. 2. It appears at first an 

 indefinite flat surface. 3. This disproved by travelling round it. 4. 

 Proof of the curvature of its surface by observation of distant objects 

 at sea. 5. By the Earth's shadow projected on the Moon. 6. In- 

 equalities of surface, such as mountains and valleys, insignificant. 

 7. Magnitude of Earth, how ascertained. 8. Length of a degree of 

 latitude. 9-10. Illustrations of the Earth's magnitude. 11. Is the 

 Earth at rest ? 12. Apparent motion of the firmament. 13. Origin 

 of the word " Universe." 14. This apparent motion may not be real 

 may arise from the rotation of the Earth. 15. How such a rotation 

 would produce it. 16. Poles. 17. Equator. 18. Hemispheres. 19. 



LARDNER'S MUSEUM OF SCIENCE. s 49 



No. 29 



