16.
1
THOSE men showed me the other course, that of the moon, twelve great gates, crowned from west to east, by which the moon goes in and out of the customary times.




16.
2
It goes in at the first gate to the western places of the sun, by the first gates with thirtyone days exactly, by the second gates with thirtyone days exactly, by the third with thirty days exactly, by the fourth with thirty days exactly, by the fifth with thirtyone days exactly, by the sixth with thirtyone days exactly, by the seventh with thirty days exactly, by the eighth with thirtyone days perfectly, by the ninth with thirtyone days exactly, by the tenth with thirty days perfectly, by the eleventh with thirtyone days exactly, by the twelfth with twentyeight days exactly.




16.
3
And it goes through the western gates in the order and number of the eastern, and accomplishes the three hundred and sixtyfive and a quarter days of the solar year, while the lunar year has three hundred and fiftyfour, and there are wanting to it twelve days of the solar circle, which are the lunar epacts of the whole year.




16.
4
[Thus, too, the great circle contains five hundred and thirtytwo years.]




16.
5
The quarter of a day is omitted for three years, the fourth fulfils it exactly.




16.
6
Therefore they are taken outside of heaven for three years and are not added to the number of days, because they change the time of the years to two new months towards completion, to two others towards diminution.




16.
7
And when the western gates are finished, it returns and goes to the eastern to the lights, and goes thus day and night about the heavenly circles, lower than all circles, swifter than the heavenly winds, and spirits and elements and angels flying; each angel has six wings.




16.
8
It has a sevenfold course in nineteen years.




