18 FIRST TEAR SCIENCE 



consequences of the earth's shape is the ease with which 

 knowledge, news, and the products of both agriculture and 

 manufacture are carried between its most distant parts. 



6. The Size of the Earth. It is easy to say that the 

 polar diameter of the earth is 7900 miles, its equatorial 

 diameter 7927 miles, and its equatorial circumference 

 24,902 miles, but a true conception of these distances is 

 not so easy. There are, however, distances on the surface 

 of the earth over which we have passed and about which 

 we have real knowledge ; and if we can translate other 

 distances into terms of these, then the unfamiliar distances 

 will become appreciable. 



One of the best ways to do this is to draw a line which 

 shall represent our known distance and then with this as 



BOSTOI4T TO CHICAGO IOQO MILES 



DIAMETER OF EARTH 8OOO 



CIRCUMFERENCE OF EARTH 25OQO MILES 



Fig. 7. 



a measure draw other lines which shall represent the dis- 

 tances of which we wish to get an appreciation. Using 

 as our standard any distance with which we are really 

 acquainted, we shall find that the lines representing the 

 different dimensions of the earth are very long. How 

 vastly greater, then, must be the distances which were 

 mentioned when treating of the stars. 



7. Effect on Life of the Irregularities of the Earth's Exterior. 

 Although the irregularities of the surface of the earth, 

 when considered in relation to its size, are insignificant, 

 yet in relation to the size of the men and animals that 

 dwell upon the earth they are very great. Some of the 

 mountains rise to heights that are inaccessible, and the 

 oceans in some places sink to depths which until recently 



