As new towns sprung up and railroads multiplied, things had come to such a pretty pass in 1883 that nobody but the astronomers knew what the real time was, and they wouldn’t tell; then a new time scheme was tried out, and as it is still used we must conclude it is a fairly good one. It is called the zone, or belt system of standard time; the time used is called standard time because the towns and cities and railroads all use it and there is no confusion.
To understand what standard time means we have to know first what a standard meridian is. A meridian, as we have said, is an imaginary line running due north and south anywhere we want it, but while a standard meridian is also a line running due north and south it has a fixed position.
The first fixed or prime meridian, as it is called, passes through Greenwich (pronounced Gren´-ij), which is a part of London, England. The reason this meridian was chosen by geographers to reckon distance east and west from is because the Royal Observatory at Greenwich is one of the oldest in the world and it was the first from which exact time was sent out.
If a circle is divided into 360 degrees, as shown in [Fig. 163], and it is also divided into 24 parts, each part will be a space equal to 15 degrees or 1 hour. Now geographers have divided the Earth into 24 equal parts by meridians separated by 15 degrees, and each space, or belt, between them represents 1 hour, as shown in [Fig. 164]. These fixed meridians start at the first, or prime meridian, at Greenwich and all the other meridians are measured in degrees east or west of Greenwich as the case may be.
Fig. 163.—Circle Divided into 360 Degrees and 24 Hours.
Starting west from the first, or prime meridian, which passes through Greenwich the time at the second standard meridian, which is called the 15th meridian because it is 15 degrees from the first meridian, will be one hour behind Greenwich time.
At every standard meridian the mean solar time is used as the standard time and every place on it and halfway to the meridian on both sides uses it, and so local time and standard.
This makes it very convenient for the traveler, for instead of setting his watch at each station he does not need to set it until he has traveled 15 degrees east or west, which is about 700 miles in our northern latitudes, and then he turns it exactly one hour ahead or one hour back, depending on the direction he is going.
