102 TIME-RECKONING. 



A journey round the world is now an everyday undertakin'^, and 

 is accomplished with comparative ease. Suppose two travellers set 

 out from a given place, one going eastwardly, the other westwardly. 

 A singular circumstance will result when they both return to the 

 common starting point, and the reason is obvious. One man will 

 arrive, according to his reckoning, say on Tuesday, 31st December, 

 when in fact at that locality it is Wednesday, January 1st. The 

 other traveller, assuming that he has kept accurately a daily journal, 

 will entei- in his diary on precisely the same day, Tliursday, January 

 2nd. This consequence has been brought out by Edgar Allan Poe, 

 in his amusing story of " Three Sundays in one Week," but it no 

 longer can be held to be an imaginary contingency, since steam com- 

 munication by land and water is now affording extraordinary facilities 

 for making the tour of the globe. 



To illustrate the difficulty more particularly. Fii-st, let us select 

 points in four quarters of the globe, each about ninety degrees apart — • 

 say in Japan, Arabia, Newfoundland and Alaska. If we assume it 

 to be Sunday midnight at the first mentioned place, it must be noon 

 at the opposite point, Newfoundland, but on what day is it noon? 

 Arabia being to the west of Japan, the local time there will be 6 p.m. 

 on Sunday ; and Alaska, lying to the east of Japan, the time there 

 will be 6 a.m. on Monday. Again, when the clock indicates 6 p.m. 

 on Sunday in Arabia, it must be Sunday noon at a point ninety 

 degrees further west, or at Newfoundland ; when it is 6 a.m. on 

 Monday at Alaska, it must be noon on Monday ninety degrees further 

 east, also at Newfoundland. Thus, by tracing local time east and 

 west from a given point to its antipodes, the clock on the one hand 

 becomes twelve hours slower, on the other hand twelve hours faster. 

 In the case in point, while it is midnight on Sunday in Japan, at 

 precisely the same moment it is noon at Newfoundland on two dis- 

 tinct days, viz., on Sunday and on Monday. 



Secondly, let us trace local time only in one direction around the 

 earth. The day does not begin everywhere at the same moment. 

 Its commencement travels from east to west with the sun, as the earth 

 revolves in the opposite direction, and it takes an entire revolution 

 of the globe on its axis for the day everywhere to be entered on. 

 Immediately on the completion of one revolution the inception of 

 any one day ends, and at this moment the end of the day begins ; 

 and the globe must make another complete revolution before the end 



