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moral character and private life. He was a celebrated stoic, enjoying the highest reputation in his own country, and in no less degree the esteem of the romans. Upon a certain occasion, Pompey, passing through Rhodes, went to pay him a visit, and forbad his lictors to knock at the door, as was the custom: 'thus,' says Pliny, he, before whom the east and the west bowed their heads, lowered his own fasces before the door of a philosopher.' The strictness of the stoical principles of Posidonius is known by a remarkable circumstance. In a speech which he delivered before the same Pompey, he was suddenly seized with such a violent fit of the gout, that the sweat flowed down his face. This acute anguifh he bore at first stoutly, without uttering a complaint, without altering the tone of his voice, without interrupting his discourse. At length nature proving the stronger, this exclamation escaped him, but was immediately stifled by philosophic pride: Pain, thou shalt not get the better of me: I will never confess that thou art an evil.'
Cleomedes, who lived a little later, has left us a work entitled, The cyclical theory of Meteors, or of the Celestial Motions; in which he treats of the sphere, of the periods of the planets, of their distances, of their magnitudes, of eclipses, &c. He acknowledges that he derived all this knowledge from Pythagoras, Eratosthenes, Hipparchus, and Posidonius, either by their writings or by tradition: yet his work is valuable, as it is the most ancient that has reached us on these subjects.
Nearly the same may be said of the Elements of Astronomy by Geminus, whom some circumstances indicate to have been a contemporary of Cleomedes. Geminus speaks very much at length of the observations of the chaldeans, and of the lunisolar periods they invented. The system of the arrangement and motions of the planets, which he proposed, was developed and explained a hundred and fifty years after by Ptolemy.
Perhaps the reader will little expect to find Julius Cæsar in the list of astronomers: yet it is incumbent on us, not to deny him this honour, since he was really well skilled in this science, and in particular did an important service to the roman calendar. A. C. 46. This calendar was established by Numa Pompilius, the second king of Rome. Some inaccuracies in it's fundamental principles, and the accumulation of fresh errours, had gradually brought it into such confusion, that at the time of Cæsar the autumn occupied the place of the winter months of the calendar, and the winter occurred in the months of spring. When Cæsar became dictator, he invited the astronomer Sosigenes from Athens to Rome, to assist him in correcting this disorder. They began by giving the year of Rome 708 fourteen months, to reestablish the order of the seasons. They then assumed as a basis, that the duration of the common year was 365 days 6 hours: and this has been called the julian year, from the name of Julius Cæsar. But as this term exceeded that of the old egyptian year by six hours; and it would have been inconvenient for civil and political purposes, to have made the year
begin sometimes at one hour of the day, and sometimes at another; it was determined, that the beginning of each year should fall constantly on the same hour of the day, that the ordinary year should consist of 365 days, and that the six hours should be left to accumulate for three successive years, on the expiration of which a day should be added, so that every fourth year should have 366. The additional or intercalary day was assigned to the month of february: so that in the common year the 24th of february was called the 6th of the calends af march, or the 6th day before the calends of march; and this day Cæsar ordered to be reckoned twice every fourth year. Thus there were two days in this year,, each of which was called the sixth of the calends of march; and in consequence these years derived the name of bissextile, from bis sexto ante calendas Martii.
The form of this calendar was very simple; but it rested on the hypothesis, that the duration of the year is of 365 days 6 hours; which is not accurate, it being in reality about eleven minutes shorter. These differences accumulating rendered at length a reform of this calendar necessary, to which I shall return hereafter.
Some other illustrious romans are mentioned as very skilful astronomers, as Cicero, Varro, &c.; but no record of their observations, or of their acquirements in this science, has reached us.
In the reign of Augustus, A. c. 6, appeared the latin poem of Manilius, entitled Astronomicon *. It
Pingré published a tranlation of Manilius into french, in 1783, and added notes to it, of more value than the poem itself.
is divided into six books; and, like the poem of Aratus, contains an explanation of the celestial motions according to the sphere of Eudoxus. The роеtry is excellent; and the exordiums of the several books, with the moral digressions, are particularly admired. Unhappily it is stained with all the reveries of judicial astrology. It is the first work of the ancients, in which this deceptive art shows itself, and is exhibited in a body of systematic doctrines. We find no trace of it in the poem of Aratus, or in the accounts of the labours of Thales, Pythagoras, Hipparchus, &c. It has derived it's birth from the natural propensity of mankind, particularly of princes and the great, to believe in the marvellous, and to receive without examination every thing that tends to flatter their vanity. Greedy quacks, acquainted with some of the secrets of nature, availed themselves of these, to acquire credit with the great, and to persuade them, that their destiny, and the fate of empires, were written in the skies: they ventured to utter equivocal and mysterious predictions, which it was always easy to make conformable with events: the errour spread abroad, and soon became general: it has continued more than sixteen hundred years, and at last has yielded only to the repeated attacks of philosophy. But by a lamentable fatality, which seems to condemn mankind to be everlastingly deceived, quackery is perpetually reviving under new forms, more or less gross; and we see it in all ages usurping without a blush the places and rewards due to real talents, to virtue, and to genius.
Menelaus, who has been mentioned already as a geometrician, A. D. 55, distinguished himself likewise in astronomy by several excellent observations, and by the discovery of the principal theorems of spherical trigonometry, which are highly necessary and useful in subjecting observations to calculation.
Astronomy had begun to languish in the school of Alexandria, when the celebrated Ptolemy began to revive it, to augment it's stores, to reduce all it's parts to more order and consistency, and to collect it's scattered fragments from all the writings and traditions that existed in his time. A. D. 140. Some make him a native of Pelusium, others of Ptolemais in Egypt. But this is of little importance: it is enough that we know he came very early to Alexandria, and that his immense labours were executed there.
His principal work, entitled Almagest*, contains all the ancient observations, and theories, to which his own researches being added, he may be considered as having formed of the whole the completest collection of ancient astronomy, that ever appeared; a work that may supply the place of those by which it was preceded, and which the hand of time has destroyed.
Ancient observations, and particularly the catalogue of the stars composed by Hipparchus, having taught Ptolemy, that these stars constantly retained the same position with respect to each other; he had fixed bases, to which he could refer the motions of
* A word derived from the arabic, and signifying The great Col