Lastly, in astronomy he is credited by Ptolemy with an explanation of the motion of the planets by a system of epicycles; he also made reseafches in the lunar theory, for which he is said to have been called Epsilon (e).
Brown, Introductory Treatise on the Lunar Theory (Cambridge University Press, 1896); Hansen, Tables de la lune (London, 1857) (Admiralty publication); W.
In the article Calendar (q.v.), that part of chronology is treated which relates to the measurement of time, and the principal methods are explained that have been employed, or are still in use, for adjusting the lunar months of the solar year, as well as the intercalations necessary for regulating the civil year according to the celestial motions.
The alchemists named it Luna or Diana, and denoted it by the crescent moon; the first name has survived in lunar caustic, silver nitrate.
Kugler 7 that the various periods underlying their lunar predictions were identical with those heretofore believed to have been independently arrived at by Hipparchus, who accordingly must be held to have borrowed from Chaldaea the lengths of the synodic, sidereal, anomalistic and draconitic months.
The Passover was kept at the full moon of the lunar month Nisan, the first of the Jewish ecclesiastical year; the Paschal lambs were slain on the afternoon of the, 4th Nisan, and the Passover was eaten after sunset the same day - which, however, as the Jewish day began at sunset, was by their reckoning the early hours of the r 5th Nisan; the first fruits (of the barley harvest) were solemnly offered on the 16th.
Relationship of a more intimate kind connects the Hindu lunar mansions with those of the Arabs and Chinese.
He now fixed his residence at Islington, engaged chiefly upon lunar observations, with a view to the great desideratum of a method of finding the longitude at sea.
In Consequence Of The Solar And Lunar Equations, It Is Evident That The Epact Or Moon'S Age At The Beginning Of The Year, Must, In The Course Of Centuries, Have All Different Values From One To Thirty Inclusive, Corresponding To The Days In A Full Lunar Month.
The solar day, the solar year, and the lunar month, or lunation, may therefore be called the natural divisions of time.