LOCATION 



457 



able to determine the exact time of the day. By taking the differ- 

 ence between the time in Greenwich and this time they are able 

 to determine the longitude of the place. 



When the time by the sun is later than the time by the chro- 

 nometer, the longitude is called east longitude. For example, if 

 it is 10 o'clock A.M. at Greenwich and 11 o'clock A.M. at the spot 

 where the ship is, the ship is 15 east longitude. If the ship records 



FIG. 349a. The time on different meridians when 

 it is noon on the prime meridian. 



FIG. 3496. International 

 date line. 



west longitude, since the time is 



9 o'clock A.M., the ship is 15 

 earlier than Greenwich time. 



A Table of Longitude and Time : 



360 of longitude corresponds to 24 hours of time. 



1 



15 of longitude corresponds to 



1 of longitude corresponds to 

 15' of longitude corresponds to 



1' of longitude corresponds to 

 15" of longitude corresponds to 



1" of longitude corresponds to 



International Date Line. If you should start to travel west from 

 Greenwich to go around the world, you would need to set your watch 

 back one hour for every 15 of longitude passed over. By the time 

 you had traveled around the world you would have set your watch 

 back 24 times, or 24 hours. You would thus lose a whole day. 



hour of time. 



hour or 4 minutes of time. 

 1 minute of time. 



minute of time. 

 1 second of time. 



second of time. 



