68 INTRODUCTION TO GENERAL SCIENCE 



49. DIRECTION LATITUDE AND LONGITUDE 



When people began to travel over the seas, it became nec- 

 essary to locate places on the earth's surface. Since the 

 earth approaches the sphere in shape, any section of it being 

 almost a circle, the system which had been used to measure 

 rotary motion was adapted to this purpose. A starting point 

 was required for the north and south directions, and another 

 for east and west. Nature supplied one, man the other. 



Since the equator is halfway between the north pole and 

 the south pole, it was taken as the starting point, and latitude 

 is given in degrees, minutes, and seconds, north or south. It 

 made no difference where the other starting point was taken, 

 so the observatory at Greenwich was called zero, and we now 

 speak of the degrees, minutes, and seconds, east or west from 

 Greenwich. Since the distance from the equator to either 

 pole is one fourth of the distance around the earth, their 

 latitude is 90 north or south. As there are 360 in a circle 

 any longitude more than 180 east becomes west. Therefore 

 180 is the limit of eastward or westward distance from Green- 

 wich. 



The north can be located, very nearly, at night by the 

 North Star, and in the daytime by means of the sun at real 

 noontime. This occurs when an object casts the shortest 

 shadow. The North Star is located by means of the 

 " pointers " of the " Dipper." Consult the references for 

 details. 



References : 



1. 1002 : 27-28. The Geographical System. 



2. 1304 : 7. The Location of the North Star.. 



3. 1304 : 402-405. Latitude and Longitude. 



a. 1302 : 13-14. Location of the North Star. 



