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be supposed to have been instructed by them, and so have been a pretty good astronomer: to this I answer:

If the Egyptians had improved their astronomy before Chiron's time; yet the Greeks were ignorant of this measure of the year, until Thales went to Egypt, and conversed with the priests of that nation. Thales, says Laertius, was the first who corrected the Greek year. And this opinion of Laertius is confirmed by Herodotus, who represents Solon, a contemporary of Thales, in his conference with Croesus very remarkably mistaking the true measure of the year. Thales had found out, that the year consisted of three hundred and sixty-five days; but the exact particulars of what he had learned in this point, were not immediately known all over Greece, and so Solon represents to Croesus, that the year consisted of three hundred and seventy-five days; for he represents it as necessary to add a whole month, i. e. thirty days, every other year, to adjust

Laert. in Vita Thaletis.

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the year then in use to its true measure. The notion therefore of the received computed year's being too short, was new in Solon's time. He was apprised that it was so; but what Thales brought from Egypt upon the subject was not yet generally known or understood; and thus Solon made mistakes in his guesses about it. Thales, according to the vulgar account, lived above six hundred years after Chiron, and above three hundred years after him, according to Sir Isaac Newton; therefore Chiron was entirely ignorant of all this improvement in astronomy. Chiron supposed three hundred and sixty days to be a year, and if he knew no better how to estimate the sun's annual motion, his oxuтa oλure, his draughts of the constellations must be very inaccurate; he could never place the Solstices with any tolerable exactness, but might easily err four or five degrees in his position of them; and if we had before us the best scheme which he could draw, I dare say, we could

Herodot. 1. 1. c. 32.

demonstrate nothing from it, but the great imperfection of the ancient astronomy. "If, indeed, it could be known what was the true place of the Solstitial points in Chiron's time; it might be known, by taking the distance of that place from the present position of them, how much time has elapsed from Chiron to our days." But I answer, it cannot be accurately known from any schemes of Chiron, what was the true place of the Solstices in his days; because, though it is said, that he calculated the then position of them, yet he was so inaccurate an astronomer, that his calculation might err four or five degrees, from their true position.

Our great and learned author mentions Thales and Meton, as if the observation of both these astronomers might confirm his hypothesis. He says, "Thales wrote a book of the Tropics and Equinoxes, and predicted the Eclipses. And Pliny tells us, that he determined the occasus matutinus of the Pleiades to be upon the twenty-fifth day after the Autumnal Equinox." From

hence he argues, 1, That the Solstices were in Thales' days, in the middle of the eleventh degrees of the signs. 2, That the Equinoxes had therefore moved backwards from their place in Chiron's time, to this their position in Thales' days, as much as answers to three hundred and twenty years; and therefore, 3. That Chiron made his scheme, and consequently the Argonautic expedition was undertaken not more than so many years before the days of Thales. But here it must be remarked, that the chief force of this argument depends upon Chiron's having rightly placed the Solstices in his time; so that what has been said of Chiron's inaccuracy must fully answer it. If Chiron erred in placing the Solstices; if their true place in his time might be in the nineteenth or twentieth degrees, and not (as is he said to suppose) in the fifteenth, then however true it be, that they were in the eleventh degrees in the time of Thales, yet it will not follow that Chiron lived but three hundred and twenty years before him. If Chiron could have been exact, there had

been a foundation for the argument; but if Chiron was mistaken, nothing but mistake can be built upon his uncorrected computation. But if Chiron was not concerned in this argument; if it depended solely upon the skill of Thales; I still suspect that there might be, though not so much, yet some error in it. Thales, though a famous astronomer for the age in which he lived, yet was not skilful enough to determine with true exactness the time of the setting of the Pleiades, or to fix accurately the Autumnal Equinox; therefore no great stress can be laid upon any guesses which he may have been reported to make in these

matters.

Thales, as I before hinted, was the first of the Grecians, who learned that the year consisted of more than three hundred and sixty days; but though he had learned this, yet he was ignorant of another material point, namely, that it consisted of almost six hours over and above the five additional days before mentioned. When the Egyptians first found this out, is uncertain; but

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