CYCLE

(Yunanca köken — orijinale bakınız.) The revolution of a certain period of time which finishes and recommences perpetually. Cycles were invented for the purposes of chronology, and for marking the intervals in which two or more periods, of unequal length, are each completed a certain number of times, so that both begin again exactly in the same circumstances as at first. The cycles used in chronology are three; the cycle of the sun, the cycle of the moon or Metonic cycle, and the cycle of indiction. The cycle qf the sun, or solar cycle, is a period of time after which the same days of the week recur on the same days of the year. If the number of days in the year were always the same, this cycle could only contain seven years; but the order is interrupted by the intercalations. In the Julian calendar the intercalary day returns every fourth year, and the cycle consequently contains 4 X 7 = 28 years; after which period the Dominical letters return in the same order, or the first day of the year and of every month falls again on the same day of the week. The origin of this cycle is unknown; it is supposed to have been invented about the time of the Council of Nice (325); but the first year of the first cycle is placed by chronologists nine years before the commencement of the Christian era. Hence the year of the cycle corresponding to any given year in the Julian calendar is found by the following rule: — Add nine to the date, and divide the sum by twenty-eight; the quotient is the number of cycles elapsed, and the remainder is the year of the cycle. Should there be r.o remainder, the proposed year is the 28th, or last of the cycle. In the reformed calendar this rule can only apply from century to century; for the order is interrupted by the omi ion of the intercalary day every hundredth year, and is not restored till the end of four hundred years. See Dominical Letter. The cycle of the moon is a period of 19 solar years, after which the new and full moons fall on the same days of the year as they did 19 years before. This cycle was invented by Meton, a celebrated astronomer of Athens, and the chronological period which he founded on it is 310 [s. 323]