30 FIRST YEAR COURSE IN GENERAL SCIENCE 



might be bulletined by telegraph at about 10 a. m. in San 

 Francisco and not earlier than 6 p. m. in London. 



21. Standard Time. It is evident that a traveler would 

 find his timepiece always too slow or too fast according to 



FIG. 7. STANDARD TIME BELTS IN THE UNITED STATES 



The meridians of 75, 90, 105, 120 are standard time meridians for 

 the Eastern, Central, Mountain, and Pacific time belts respectively. If the 

 belts were of uniform width, time changes would be made at meridians half 

 way between these standard meridians. The time changes are, however, 

 made at cities which are important railroad centers. The lines connecting 

 these cities do not correspond exactly to meridians. 



1. What is the widest time belt in the United States? 2. What is the 

 difference between sun time and standard time at places on the 70th meridian? 

 3. On the 115th? 4. What is the difference between sun time and standard 

 time at your meridian? 5. A man leaves Washington at 10 a. m. and arrives 

 at Chicago the next day at 9 a. m. by his watch. He learns that the next 

 train west leaves the same station at 8: 10 a. m. Can he take it? Explain. 



which way he journeyed, if each city regulated its time by 

 the position of the sun. To avoid inconveniences which 

 would occur in business, and in railroad and steamboat con- 

 nections, the United States government in 1883 divided the 

 country into belts about 15 degrees wide. Since that time, 



