Page:Popular Science Monthly Volume 18.djvu/783

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Ptolemaic system, was: 1. Saturn; 2. Jupiter; 3. Mars; 4. Sun; 5. Venus; 6, Mercury; 7. Moon. The Chaldeans called the twenty-four hours of the day by the names of these planets in their order, and named each day from the first hour of the day. Thus, first hour of first day was Saturn; last hour (or twenty-fourth) was Mars; first hour of next day was Sun, hence called Sunday; first hour of next day Moon, hence called Monday, etc. Our Saxon ancestors named the days from their corresponding gods. Thus, what the Romans called Marsday, the Saxons called Tuisco-day (whence Tuesday), Tuisco being their god of war as Mars was among the Romans, and so of the rest.

The early Romans began the year with March, but in the time of Cæsar it began with January. The early Christian Church began it on March 25th, and this was the beginning of the civil and ecclesiastical year in England and her American colonies until 1752, when it was changed by act of Parliament to January 1st.

Cycles.—To facilitate computation of time, to fix the recurrence of moons and days, and to establish epochs as standpoints of chronology, recourse was had to cycles, which we will now examine. The word cycle is derived from a Greek word which signifies a circle—here it signifies a circle of time. The first and most important among them was the Cycle of the Moon, the object of which was to accommodate the computation of time by the moon to that of the sun. It was invented about 430 b. c, by an Athenian named Meton, whence it was called also the Metonic Cycle, and was used to fix the times of the Grecian festivals, but fell into disuse with these festivals and was afterward restored by the Council of Nice, a. d. 325, being best adapted of all to fixing the time of Easter.

This cycle, at the time of its invention, was deemed entirely correct, and was so much superior to any other that had been attempted that each year was written in letters of gold in the public marts of Greece, from which cause it has ever since been known as the "golden number." It was constructed as follows: It had been discovered that the lunar year was eleven days shorter than the solar year; so that, if a new moon occurred upon any given day of any solar year, on the same day of the next solar year the moon would be eleven days old, on the same day of the second year twenty-two days old, etc. Examination showed that the new moon would again occur upon the same day of the solar year in the course of nineteen years. Hence the lunar cycle consists of nineteen years. The other ancient cycles are unimportant for our present purpose; the other cycles that we shall consider are the inventions of modern chronologers.

Solar Cycle.—Chronologers have affixed to the seven days of the week the first seven letters of the alphabet, as follows: To January 1, A; January 2, B, etc., and whichever letter the first Sunday of the year happens to fall upon is called the dominical or Sunday letter for that year. The object of this cycle is to find (without reference to the