The age of the Moon is found by the Epact, its age on the first day of the year. It is about the same on March 1 as on January 1, owing to January and February being together equal to two lunar months. So the increase of the Epact during the year, at the rate of about one day in the month, begins March 1; and September is, for this purpose, the seventh month.
To the day of the month add the Epact and the number of the month, beginning March 1. The total, over 0 or over 30, is the age of the moon.
_Example._—September 10, 1910 (7th Month), Epact for 1910 being xix.
10 + 19 + 7 = 36. The Moon was 6 days old.
What will be the date of full moon, its fifteenth day, in November 1912? November is the ninth month and the Epact for 1912 is xi.
11 + 9 = 20. 45 (= 30 + 15) - 20 = 25. _Ans._ November 17.
Agriculturists who believe that certain seeds should be sown, trees planted, and pigs converted into bacon during the waxing of the moon, while trees are felled during the waning, find the Epact useful in reckoning the moon’s age. It is also useful in calculating whether country-roads will be moonlit during certain nights.
The Epact increases 11 days annually: 1911, 0; 1912, xi; 1913, xxij; coming back to 0 in 31 years.
While the circle of the horizon is divided into 360 degrees for astronomy and for accurate navigation, the steersman has always divided it sexdecimally. The temple of the Winds at Athens was octagonal; and the points of the horizon were named after the eight winds, a number increased to sixteen about the time of Ptolemy. The Romans tried in vain to substitute an uncial division; their 12 winds and points could not supersede the 8 winds and points of the Greeks. And to this day in the Mediterranean there are 8 principal points, named after the sun and winds:
Greco, N.E.; Scirocco, S.E.; Libeccio, S.W.; Maestralo, N.W.
Amerigo Vespucci sailed for the ‘_Ponente una quarta di Libeccio_,’ West, one point S.W.; and afterwards for the ‘_Libeccio una quarta del Mezzodi_,’ S.W. one point S.
DIAGRAM INDICATING THE PLANET RULING EACH HOUR, FROM DE TEMPORUM COMPUTATIONE ATQUE DIVISIONE, Joannis Padovanii, Veronæ, 1577.
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