x hours, or to one
day in 304 years. This period exceeds seventy-six true solar years by
fourteen hours and a quarter nearly, but coincides exactly with seventy-six
Julian years; and in the time of Calippus the length of the solar year was
almost universally supposed to be exactly 3651/4 days. The Calippic period is
frequently referred to as a date by Ptolemy.

_Ecclesiastical Calendar._--The ecclesiastical calendar, which is adopted
in all the Catholic, and most of the Protestant countries of Europe, is
luni-solar, being regulated partly by the solar, and partly by the lunar
year,--a circumstance which gives rise to the [v.04 p.0992] distinction
between the movable and immovable feasts. So early as the 2nd century of
our era, great disputes had arisen among the Christians respecting the
proper time of celebrating Easter, which governs all the other movable
feasts. The Jews celebrated their passover on the 14th day of _the first
month_, that is to say, the lunar month of which the fourteenth day either
falls on, or next follows, the day of the vernal equinox. Most Christian
sects agreed that Easter should be celebrated on a Sunday. Others followed
the example of the Jews, and adhered to the 14th of the moon; but these, as
usually happened to the minority, were accounted heretics, and received the
appellation of Quartodecimans. In order to terminate dissensions, which
produced both scandal and schism in the church, the council of Nicaea,
which was held in the year 325, ordained that the celebration of Easter
should thenceforth always take place on the Sunday which immediately
follows the full moon that happens upon, or next after, the day of the
vernal equinox. Should the 14th of the moon, which is regarded as the day
of full moon, happen on a Sunday, the celebration Of Easter was deferred to
the Sunday following, in order to avoid concurrence with the Jews and the
above-mentioned heretics. The observance of this rule renders it necessary
to reconcile three periods which have no common measure, namely, the week,
the lunar month, and the solar year; and as this can only be done
approximately, and within certain limits, the determination of Easter is an
affair of considerable nicety and complication. It is to be regretted that
the reverend fathers who formed the council of Nicaea did not abandon the
moon altogether, and appoint the first or second Sunday of April for the
celebration of the Easter festival. The ecclesiastical