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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 Solsiices 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. Arid Pliny tells us, that he determined the occasus malutinus 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, .1. 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 (he 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; bat their discovery of it was not so early as the time when they came to the knowledge of the other point, which is evident from the fable in which their mythologic writers dressed up the doctrine of the year's consisting of three hundred and sixty-five days.' According to that fable, fire days were the exact seventy-second part of the whole year, and five is so of three hundred and sixty; therefore, when the five days were first added, the year was thought to consist only of three hundred and sixty-five days. It is hard to say when the Egyptians made this further improvement of their astronomy; but whenever they did, it is certain that Thales knew nothing of it, for Sir John Marsham rightly observes, that Herodotu9 takes no notice of a quarter part of a day, which should be added to the year over and above the five additional days, and adds,k that Eudoxus first learned from the Egyptian
priests, that such farther addition ought to be made to the measure of the year, and he cites Strabo's express words to confirm his observation.i Now Eudoxus lived about three hundred years after Thales, and there. fore Thales was entirely ignorant, both of this, and, according to Strabo, of many other very material points in astronomy, which Eudoxus learned in Egypt.
Thales is, indeed, said to have foretold an eclipse, i. e. I suppose he was able to foresee that there would be one, not that he could caleulate exactly the time when; perhaps he might guess within two or three weeks, and perhaps he might err above twice that number, and yet be thought in his age a very great astronomer. Sir Isaac Newton says, that he wrote a book concerning the tropics and equinoxes; which