, the 12th part of the year, and is so called from the Moon, by whose motions it was regulated; being properly the time in which the moon runs through the zodiac. The lunar Month is either illuminative, periodical, or synodical.

Illuminative Month, is the interval between the first appearance of one new moon and that of the next following. As the moon appears sometimes sooner after one change than after another, the quantity of the Illuminative Month is not always the same. The Turks and Arabs reckon by this Month.

Lunar Periodical Month, is the time in which the moon runs through the zodiac, or returns to the same point again; the quantity of which is 27days 7hrs 43m. 8 sec.

Lunar Synodical Month, called also a Lunation, is the time between two conjunctions of the moon with the sun, or between two new moons; the quantity of which is 29 days, 12 hours, 44m. 3 sec. 11 thirds.

The ancient Romans used Lunar Months, and made them alternately of 29 and 30 days: They marked the days of each Month by three terms, viz, Calends, Nones, and Ides.

Solar Month, is the time in which the sun runs through one entire sign of the ecliptic, the mean quantity of which is 30 days 10 hours 29 min. 5 sec. being the 12th part of 365 ds. 5 hrs. 49 min. the mean solar year.

Astronomical or Natural Month, is that measured by some exact interval corresponding to the motion of the sun or moon. Such are the lunar and solar months above-mentioned.

Civil or Common Month, is an interval of a certain number of whole days, approaching nearly to the quantity of some astronomical month. These may be either lunar or solar. The

Civil Lunar Month, consists alternately of 29 and 30 days. Thus will two Civil Months be equal to astronomical ones, abating for the odd minutes; and so the new moon will be kept to the first day of such Civil Months for a long time together. This was the Month in Civil or common use among the Jews, Greeks, and Romans, till the time of Julius Cæsar. The

Civil Solar Month, consisted alternately of 30 and 31 days, excepting one Month of the twelve, which consisted only of 29 days, but every 4th year of 30 days. And this form of Civil Months was introduced by Julius Cæsar. Under Augustus, the 6th Month,| till then from its place called Sextilis, received the name Augustus, now August, in honour of that prince; and, to make the compliment still the greater, a day was added to it; which made it consist of 31 days, though till then it had only contained 30 days; to compensate for which, a day was taken from February, making it consist of 28 days, and 29 every 4th year. And such are the Civil or Calendar Months now used through Europe.

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Entry taken from A Mathematical and Philosophical Dictionary, by Charles Hutton, 1796.

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MOORE (Sir Jonas)