THE SHAPE OF THE EARTH 21 



east, south, and west; and carefully built the sides of their 

 temples and palaces to correspond with these directions. 

 The Egyptians developed the science of geometry (earth- 

 measuring) primarily for the purpose of measuring land areas. 

 The great poet Homer shows that the Greeks of his time 

 had made many careful observations of the earth's surface, 

 as well as many ingenious guesses about it. He conceived 

 the earth as a circular plane surrounded by the Ocean, a 

 broad and deep river, which was the source of all waters. 

 Homer's idea of the shape of the earth 

 held sway for hundreds of years. As 

 time went on, however, more and more 

 was learned about the earth, until to-day 

 a great amount of accurate knowledge 

 has been acquired, which is of the ut- F IQURE 3. 



value to mankind. i' GRAM SHOWING 



THE SHAPE OF THE 

 EARTH 



The Shape of the Earth. Men who Any drawing which 

 have in different ways made careful 



measurements of the shape of the earth poles and the buig- 



. 7-7 ing a * the equator 



tell us that it is an oblate spheroid i s O f necessity tre- 

 (Figure 3); that is, a sphere which is ^ dously exagger ~ 

 somewhat flattened at two opposite points. 

 An ordinary orange has this shape. The earth has been so 

 little flattened, however, that its shape is very much nearer 

 that of a perfect sphere than is that of an orange. Its 

 polar diameter is only 27 miles shorter than its equatorial 

 diameter; and so when we consider that each of its diame- 

 ters is nearly 8000 miles, a shortening of only 27 miles in 

 one of these would not change its shape from that of a 

 sphere enough to be noticed e&ept by the, mpst careful 

 measurements. 



