[a] Quintilian puts the same question; and, according to him,
Demosthenes is the last of the ancients among the Greeks, as Cicero
is among the Romans. See _Quintilian_, lib. viii. cap. 5.
[b] The siege of Troy is supposed to have been brought to a conclusion
eleven hundred and ninety-three years before Christian æra. From that
time to the sixth year of Vespasian (A.U.C. 828), when this Dialogue
was had, the number of years that intervened was about 1268; a period
which, with propriety, may be said to be little less than 1300 years.
[c] Demosthenes died, before Christ 322 years, A.U.C. 432. From that
time to the sixth of Vespasian, A.U.C. 828, the intervening space was
about 396 years. Aper calls it little more than 400 years; but in a
conversation-piece strict accuracy is not to be expected.
[d] In the rude state of astronomy, which prevailed during many ages
of the world, it was natural that mankind should differ in their
computation of time. The ancient Egyptians, according to Diodorus
Siculus, lib. i. and Pliny the elder, lib. vii. s. 48, measured time
by the new moons. Some called the summer one year, and the winter
another. At first thirty days were a lunar year; three, four, and six
months were afterwards added, and hence in the Egyptian chronology the
vast number of years from the beginning of the world. Herodotus
informs us, that the Egyptians, in process of time, formed the idea of
the solar or solstitial year, subdivided into twelve months. The Roman
year at first was lunar, consisting, in the time of Romulus, of ten
months. Numa Pompilius added two. Men saw a diversity in the seasons,
and wishing to know the cause, began at length to perceive that the
distance or proximity of the sun occasioned the various operations of
nature; but it was long before the space of time, wherein that
luminary performs his course through the zodiac, and returns to the
point from which he set out, was called a year. The great year (_annus
magnus_), or the PLATONIC YEAR, is the space of time, wherein the
seven planets complete their revolutions, and all set out again from
the same point of the heavens where their course began before.
Mathematicians have been much divided in their calculations. Brotier
observes, that Riccioli makes the great year 25,920 solar years;
Tycho Brahe, 25,816; and Cassini, 24,800. Cicero expressly calls it a
period of 12,954 years. _Horum annorum, quos in fastis habemus, MAGNUS
annos duodecim millia nonagentos quinquaginta quatuor amplectitur
solstitiales scilicet._ For a full and accurate dissertation on the
ANNUS MAGNUS, see the Memoirs of the Academy of Belles Lettres, tom.
xxii. 4to edit. p. 82.
Brotier, in his note on this passage, relates a fact not universally
known. He mentions a letter from one of the Jesuits on the mission,
dated _Peking_, 25th October 1725, in which it is stated, that in the
month of March preceding, when Jupiter, Mars, Venus, and Mercury were
in conjunction, the Chinese mathematicians fancied that an
approximation of Saturn was near at hand, and, in that persuasion,
congratulated the emperor YONG-TCHING on the renovation of the world,
which was shortly to take place. The emperor received the addresses of
the nobility, and gave credit to the opinion of the philosophers in
all his public edicts. Meanwhile, _Father Kegler_ endeavoured to
undeceive the emperor, and to convince him that the whole was a
mistake of the Chinese mathematicians: but he tried in vain; flattery
succeeded at court, and triumphed over truth.
[e] The argument is this: If the great year is the measure of time;
then, as it consists, according to Cicero, of 12,954 solar years, the
whole being divided by twelve, every month of the great year would be
clearly 1080 years. According to that calculation, Demosthenes not
only lived in the same year with the persons engaged in the Dialogue,
but, it may be said, in the same month. These are the months to which
Virgil alludes in the fourth eclogue:
Incipient magni procedere menses.