“324. For a farther illustration, THUCYDIDES relates, that a solar Eclipse happened on a Summer’s day in the afternoon, in the first year of the _Peloponnesian_ war, so great that the Stars appeared. _Rhodius_ was victor in the _Olympic_ games the fourth year of the said war, being also the fourth of the 87th _Olympiad_, on the 428th year before CHRIST. So that the Eclipse must have happened in the 431st year before CHRIST; and by computation it appears, that on the 3d of _August_ there was a signal Eclipse which would have past over _Athens_, central about 6 in the evening, but which our present Tables bring no farther than the antient _Syrtes_ on the _African_ coast, above 400 miles from _Athens_; which suffering in that case but 9 Digits, could by no means exhibit the remarkable darkness recited by this historian; the center therefore seems to have past _Athens_ about 6 in the evening, and probably might go down about _Jerusalem_, or near it, contrary to the construction of the present Tables. I have only obviated these things by way of caution to the present Astronomers, in re-computing antient Eclipses; and refer them to examine the Eclipse of _Nicias_, so fatal to the _Athenian_ fleet[71]; that which overthrew the _Macedonian_ Army[72] _&c._” So far Mr. SMITH. [Sidenote: The number of Eclipses.] 325. In any year, the number of Eclipses of both Luminaries cannot be less than two, nor more than seven; the most usual number is four, and it is very rare to have more than six. For the Sun passes by both the Nodes but once a year, unless he passes by one of them in the beginning of the year; and if he does, he will pass by the same Node again a little before the year be finished; because, as these points move 19 degrees backward every year, the Sun will come to either of them 173 days after the other § 319. And when either Node is within 17 degrees of the Sun at the time of New Moon, the Sun will be eclipsed. At the subsequent opposition the Moon will be eclipsed in the other Node; and come round to the next conjunction again ere the former Node be 17 degrees past the Sun, and will therefore eclipse him again. When three Eclipses fall about either Node, the like number generally falls about the opposite; as the Sun comes to it in 173 days afterward: and six Lunations contain but four days more. Thus, there may be two Eclipses of the Sun and one of the Moon about each of her Nodes. But when the Moon changes in either of the Nodes, she cannot be near enough the other Node at the next Full to be eclipsed; and in six lunar months afterward she will change near the other Node: in these cases there can be but two Eclipses in a year, and they are both of the Sun. [Sidenote: Two periods of Eclipses.]