THE SHAPE OF THE EARTH 



17 



MOUNT EVEREST . 



In these days many men have sailed around the earth, 

 but valiant indeed was that little company which in 1522 

 first proved that it was possible to sail continually in one 

 direction and yet reach the home port, thus demonstrating 

 that the earth was prob- 

 ably round. Long be- 

 fore, wise men had come 

 to believe that the earth 

 was a sphere, for it had 

 been noted as far back 

 as the time of Aristotle, 

 the famous Greek phi- 

 losopher, that when the 

 shadow of the earth fell 

 upon the moon, causing As k would appear if P laced in the dee P est 



part of the sea. 



an eclipse of the moon, 



the boundaries of the shadow were curved lines. It was 

 also later noticed that when ships are seen approaching 

 at sea the masts appear first and then gradually the lower 

 parts of the ship. The reverse was seen to be true when 

 ships sailed away. 



Experiment 7. Add alcohol to water until a solution is obtained 

 in which common lubricating oil will float at any depth. Insert with 

 a glass tube a large drop of oil below the surface of the solution. 

 The oil will float in the solution in the shape of a sphere. This illus- 

 trates the fact that if a liquid is relieved from the action of outside 

 forces, it will take the form of a perfect sphere. 



A spherical surface is the smallest surface by which a 

 solid can be bounded, so the maximum distance which 

 can separate places located on a given solid will be least 

 when its surface is spherical. Thus the inhabitants of 

 the earth, considering the surface over which they may 

 scatter themselves, are brought into the closest possible 

 relation to one another. One of the most noteworthy 



