SUMMARY 43 



around the sun, combined with the inclination of the 

 earth's axis, gives us the seasons. The inclination of the 

 earth's axis, combined with its revolution, and the move- 

 ment just mentioned, gives us our latitude zones and 

 causes the variation in the length of our days and nights. 



Distance east and west on the earth is measured by 

 meridians of longitude; distance north and south by 

 parallels of latitude. The parallels are about seventy 

 miles apart, and this is also about the distance between 

 the meridians at the equator. Two parallels at the poles 

 are about the same distance apart as two at the equator. 

 But as all meridians pass through the poles, there is no 

 distance at all between them there, while at the equator 

 they are about seventy miles apart. 



To find the direction a ship sails we use a compass, 

 a magnetized needle which points toward the north mag- 

 netic pole, located northeast of Alaska. Thus, the mag- 

 netism of the earth is of infinite value to ocean commerce. 



QUESTIONS 



What simple reasons are there for believing that the earth is 

 round ? 



What effects have the irregularities of the earth's surface had on 

 life? 



Draw diagrams illustrating what was discovered in Exp. 8. 



Why do we have winter when the earth is nearest the sun ? 



If a man left Cairo, Egypt, on June 21 and traveled slowly to Cape 

 Town, reaching there on Dec. 21, what changes of seasons would he 

 experience ? 



How is the length of a day determined? If it were noon Thurs- 

 day, Sept. 30, with you, what would be the day and date at Yokohama ? 



Why is Standard Time particularly advantageous in the United 

 States? How much is the difference between local and standard 

 time at your locality ? 



Suppose that a man at the north pole traveled a degree south and 

 then a degree east. How far would he travel? Suppose he were a 



