by
subtracting 5502, up to the Alexandrian year 5786 inclusive, and after
that year by subtracting 5492; but if the date belongs to one of the
four last months of the Christian year, we must subtract 5503 till the
year 5786, and 5493 after that year.

_Mundane Era of Antioch._--The chronological reckoning of Julius
Africanus formed also the basis of the era of Antioch, which was adopted
by the Christians of Syria, at the instance of Panodorus, an Egyptian
monk, who flourished about the beginning of the 4th century. Panodorus
struck off ten years from the account of Julius Africanus with regard to
the years of the world, and he placed the Incarnation three years later,
referring it to the fourth year of the 194th Olympiad, as in the common
era. Hence the era of Antioch differed from the original era of
Alexandria by ten years; but after the alteration of the latter at the
accession of Diocletian, the two eras coincided. In reckoning from the
Incarnation, however, there is a difference of seven years, that epoch
being placed, in the reformed era of Alexandria, seven years later than
in the mundane era of Antioch or in the Christian era.

As the Syrian year began in autumn, the year of Christ corresponding to
any year in the mundane era of Antioch is found by subtracting 5492 or
5493 according as the event falls between January and September or from
September to January.

_Era of Nabonassar._--This era is famous in astronomy, having been
generally followed by Hipparchus and Ptolemy. It is believed to have
been in use from the very time of its origin; for the observations of
eclipses which were collected in Chaldaea by Callisthenes, the general
of Alexander, and transmitted by him to Aristotle, were for the greater
part referred to the beginning of the reign of Nabonassar, founder of
the kingdom of the Babylonians. It is the basis of the famous Canon of
kings, also called Mathematical Canon, preserved to us in the works of
Ptolemy, which, before the astonishing discoveries at Nineveh, was the
sole authentic monument of Assyrian and Babylonian history known to us.
The epoch from which it is reckoned is precisely determined by numerous
celestial phenomena recorded by Ptolemy, and corresponds to Wednesday at
mid-day, the 26th of February of the year 747 before Christ. The year
was in all respects the same as the ancient Egyptian year. On account of
the difference in the length of the Julian and Babylonian years, the
conver