34 



OUR OWN WORLD 



table level and fix it firmly so that it cannot be moved. Fix ver- 

 tically upon the table a knitting needle or a slender stick. Mark 

 the line of the sun's shadow and note accurately the time the 

 shadow falls on this line. On the next day note the time the shadow 

 falls upon the same line. If your watch is right, the difference in 

 tune it shows between the falling of the shadows the first and the 

 second day is the difference between this particular solar day and 

 the mean solar day. This may be nearly a minute. The shortest 

 shadow of the day marks noon. It extends north and south. 

 (Your watch keeps mean solar time. But twelve o'clock by your 

 watch will probably not be midday or high noon, as your watch 

 is set to Standard Time.) 



Standard Time. When railways extending east and 

 west became numerous in the United States and there 



MAP SHOWING STANDARD TIME BELTS 



were many through trains and numerous passengers, it 

 became very inconvenient to use local time, since no two 

 places had the same time. Each railway therefore adopted 

 a time of its own, and when several railways entered the 



