CHAPTER XXVI 



LONGITUDE AND TIME 



148. Locating Points on a Globe. It would be very diffi- 

 cult to indicate a point upon a stationary ball or globe, for it 

 has neither up nor down, sides nor ends, nor points of the 

 compass. When such a body is rotating, however, the task 

 becomes very easy. We have only to call the imaginary line 

 about which it spins its axis, and the two points where this 

 line comes to the surface, its poles, to get two locations upon 

 it that do not change. If a set of 

 lines are now imagined passing 

 around the globe through these 

 poles, and another set extending 

 around it at right angles to them, 

 any place may readily be located 

 by noting its distance from the 

 nearest line of each set. The earth 

 is such a globe, and the location of 

 points upon it is determined in this 

 manner. If one turns his back to 

 the sun at noon in our part of the 

 world, he will be facing that pole called the north pole. The 

 direction on his right will be east and on his left west. South 

 will be behind him. The circles passing through the poles are 

 known as meridians, and those running at right angles to these 

 are parallels. The distance of a place from a given meridian 

 expressed in degrees, is called its longitude, and the distance 

 north or south of the great circle, called the equator, that passes 

 around the earth midway between the poles is its latitude. 



181 



FIG. 63. Important circles on 

 the earth. 



