4 9 P. 1872 D Nov. 15 0 29 A. 1873 D May 12 6 23 A. 1874 Oct. 25 2 37 A. 1875 Sept. 29 6 12 A. 1876 D Mar. 10 1 5 A. Mar. 25 4 45 P. M. Total over a southern section M.Moon rises partially eclipsed. M. Commences 4 h. 34 m. Total in M. M. M. Small. 1877 Aug. 23 6 2P. M. Total. Moon rises eclipsed. 1878 Feb. 17 5 58 A. M. July 29 5 35 P. M. CHAPTER IX. Divisions of Time. TIME, as measured by the celestial luminaries, is divided into periods, cycles, years, months, weeks, days, hours, minutes, seconds, and sometimes farther sexagesimal parts. Periods, in astronomical reckoning, are large divisions of time. The Chaldean Period is a circle of 25,858 years. This period respects the motion of the terrestrial poles. At the termination of it the axis of the Earth points to the same stars as at the beginning. The Julian Period is formed by multiplying together the cycles 28, 19, and 15. It consists of 7,980 years. The creation of the world, according to the common computation, was on the 706th year, and the Dionysian era of Christ's birth, on the 4,713th year, of this period. According to some, the birth of Christ was earlier by four years. The Julian period is found of use in comparing the dates of ancient events. The Dionysian Period, or circle of Easter, consists of 532 years, formed by multiplying the cycle of the Sun, 28, by that of the Moon, 19. CYCLES ARE REVOLUTIONS OF TIME. The Cycle of the Sun consists of 28 years.) By this cycle the days of the week are brought to the same days of the month the Sun to the same signs and degrees of the ecliptic, with little variation; and the leap years to the same state as at the commencement of the cycle. Each of these returns, separately, in a much shorter period. But, by the cycle, they are brought to coincide. The Cycle of the Moon is the Golden Number. It is a period of 19 years, at the expiration of which, the changes and fulls, with the other aspects of the Moon, return to the same months, and days of the month, as at the beginning, or within a day of the same time. The Roman Indiction is a period of 15 years, established by Constantine, in the year 312, for indicating the times of certain payments, made by the subjects to the government. For finding the cycle of the Sun, golden number, and indiction, add 4,713 to the year of the Christian era, and divide the sum by 28, 19, and 15, respectively; the remainders are the numbers sought for the year. Required the cycle of the Sun, golden number, and indiction, for the year 1831. The Epact is the excess of the solar above the lunar year of 354 days, or 12 mean lunations. It is taken for the age of the Moon, on the first day of January. For finding the Julian epact, multiply the golden number of the year by 11; the product, if less than 30, is the Epact. But, if the product exceed 30, divide it by 30; the remainder is the epact. To find the Gregorian epact, the Julian epact must be first found. From this subtract 12, the number of days between the old and new style in the present century; the remainder is the epact required.* If * The rule of Mr. Pike and some others, to deduct 11 for the difference between the Julian and Gregorian epact, applies to the last nothing remain, 29 is the epact. If the subtraction cannot be made, add 30 to the Julian epact, and subtract as before. The golden number and epact are little used at the present time; especially where accuracy is required. The Roman indiction, still less important, is retained in our almanacs; why, is difficult to be conceived, unless as it is used in forming the Julian period. A Year. A complete revolution of the seasons constitutes a year. The difference in the years, the tropical, the sidereal, and anomalistic, has been considered. The civil solar year consists of 365 days) and in bissextile, of 366. In this manner it is used in the United States, and most European nations. The lunar year consists of (12 lunar months, or mean lunations; computed at 354 days, the surplus arising from the minutes and seconds of the lunation being generally dropped in the computation. In this calendar a (month is added every third year, to make the lunar coincide with the solar year. This month is intercalary, or embolimic. The Jews computed their time by lunar years. "But, by intercalating no more than a month of thirty days, which they called Ve-Adar every third year, they fell 3 days short of the solar year in that time" The year of the Greeks consisted of 12 months, of 29 and 30 days, alternately taken, comprising 354 days, or about 12 mean lunations. This lunar year was with difficulty connected with the solar year, or the revolution of the seasons, so as to make a particular month fall at the same season in successive years. century only. The difference between the styles ought, in all computations of the kind, to be deducted. Hence the practice of celebrating the birth-day of Washington on the 22d of February, in the present century, must be erroneous. The celebration ought to be on the 23d of February.} |