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WHY THE SUNDIAL KEEPS TIME - Page 8

It is not hard to imagine what confusion there would be today if watches and clocks did not agree. We never would be on time. In 1884 an international conference assembled in Washington, D.C., to fix and recommend for universal adoption a prime meridian, to be used in reckoning longitude and regulating time throughout the world. The acceptance of the prime meridian of Greenwich, England, altered timekeeping. Certain standard time meridians were designated for everyday use, which varied by one hour, or fifteen degrees of longitude. In so far as practical, all places within seven and one half degrees on either side of a standard time meridian were considered within a certain standard time zone. There are four standard time zones in the United States Eastern, Central, Mountain, and Pacific. The adoption of standard time made it possible for people to travel great distances without being at odds in their time. Only when he entered a different time zone, such as going from New York to Chicago, would a man have to change his watch, then he would set it backward or forward exactly one hour, depending upon whether he was traveling westward or eastward. Standard time injected another difference between the sundial and clock which is constant for any particular place, and is derived from the position of any given place in respect to its standard time meridian. For example Boston is east of the standard time meridian sixteen minutes after it has crossed the meridian of Boston. Since neither the standard time meridian nor the meridian of Boston will change, the distance in time between them remains constant. This constant difference is equal to four minutes of time for each degree of longitude. It can be added to or subtracted from the reading of a mean time sundial, as the sundial is situated west or east of a standard meridian, in order to obtain standard time. The foregoing shows why a sundial will tell time. The reasons why it can tell time accurately and in accordance with our present day standards are these: 1 We can construct an instrument which will record equal hours by means of the sun. 2 This instrument can be corrected to show local mean time in any locality. 3 The local mean time sundial can be corrected to show standard time. The subject of time is of such importance to everyone that a separate section has been devoted to it, where tables and complete instructions for correcting your sundial are given.

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