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pothesis of the earth, being at rest in the centre of the universe, and that the heavenly bodies, the stars and planets, all move round it in solid orbs, whose motions are all directed by one, which Ptolemy calls the primum mobile, or first mover, of which he discourses at large. But, to be more particular, this great work is divided into thirteen books.
In the first book, Ptolemy shows that the earth is in the centre of those orbs, and of the universe itself, as he understood it; he represents the earth as of a spherical figure and but as a point in comparison of the rest of the heavenly bodies; he treats concerning the several circles of the earth and their distances from the equator; as also of the right and oblique ascension of the heavenly bodies in a right sphere.
In the second book, he treats of the habitable parts of the earth, and of the elevation of the pole in an oblique sphere, and the various angles which the several circles make with the horizon, according to the different latitude of places; also of the phenomena of the heavenly bodies depending on the same.
In the third book he treats of the quantity of the year, and of the unequal motion of the sun through the zodiac; he here gives the method of computing the motion of the sun, with tables of the same; and likewise treats of the inequality of days and nights.
In the fourth book he treats of the lunar motions, and their various phenomena; he gives tables for finding the moon's mean motions, with her latitude and longitude; he discourses largely concerning lunar epicycles; and by comparing the times of a great number of eclipses, mentioned by Hipparchus, Calippus, and others, he has computed the places of the sun and moon, according to their mean motions, from the first year of Nabonassar, king of Egypt, to his own time.
In the fifth book he treats of the instrument called the astrolabe; he treats also of the eccentricity of the lunar orbit, and the inequality of the moon's motion according to her distance from the sun; he also gives tables, and an universal canon for the inequality of the lunar motions; he then treats of the different aspects or phases of the moon, and gives a computation of the diameter of the sun and moon, with the magnitude of the sun, moon, and earth, compared together; he states also the different measures of the distance of the sun and moon, according as they are determined by ancient mathematicians and philosophers.
In the sixth Book he treats of the conjunctions and oppositions of the sun and moon, with tables for computing the mean time when they happen; of the boundaries of solar and lunar eclipses; of the tables and methods of computing the eclipses of the sun and moon, with many other particulars.
In the seventh Book he treats of the fixed stars, and shows
the method of describing them in their various constellations, on the surface of an artificial sphere or globe; he rectifies the places of the stars to his own time, and shows how different those places were then, from what they had been in the times of Timocharis, Hipparchus, Aristillus, Colippus, and others, he then lays down a catalogue of the stars in each of the northern constellations, with their latitude, longitude, and magnitude.
In the eighth Book he gives a like catalogue of the stars in the constellations of the southern hemisphere, and in the twelve signs or constellations of the zodiac. This is the first catalogue of the stars now extant, and forms the most valuable part of Ptolemy's works. He then treats of the galaxy, or milky-way; also of the planetary aspects, with the rising and setting of the sun, moon, and stars.
In the ninth Book he treats of the order of the sun, moon, and planets, with the periodical revolutions of the five planets; then he gives tables of the mean motions, beginning with the theory of Mercury, and showing its various phenomena with respect to the earth.
The tenth Book begins with the theory of the planet Venus, treating of its greatest distance from the sun; of its epicycle, eccentricity, and periodical motions; it then treats of the same particulars in the planet Mars.
The eleventh Book treats of the same circumstances in the theory of the planets Jupiter and Saturn. It also corrects all the planetary motions, from observations made from the time of Nabonassar to his own.
The twelfth book treats of the retrogressive motion of the several planets, giving also tables of their stations, and of the greatest distances of Venus and Mercury from the sun.
The thirteenth Book treats of the several hypotheses of the latitude of the five planets; of the greatest latitude or inclination of the orbits of the five planets which are computed and disposed in tables; of the rising and setting of the planets, with tables of them. Then follows a conclusion or winding up of the whole work.
This great work of Ptolemy will always be valuable on account of the observations he gives of the places of the stars and planets in former times, and according to ancient philosophers and astronomers that were then extant; but principally on account of the large and curious catalogue of the stars, which being compared with their places at present, we thence deduce the true quantity of their slow progressive motion according to the order of the signs, or of the precession of the equinoxes.
Another great and important work of Ptolemy, was his Geography, in seven Books, in which, with his usual sagacity, he searches out and marks the situation of places according to their latitudes and longitudes; and he was the first that did so.
Though this work must needs fall far short of perfection, through the want of necessary observations, yet it is of considerable merit, and has been very useful to modern geographers. Cellarius indeed suspects, and he was a very competent judge, that Ptolemy did not use all the care and application which the nature of his works required; and his reason is, that the author delivers himself with the same fluency and appearance of certainty concerning things and places at the remotest distances, which it was impossible he could know any thing of, that he does concerning those which lay the nearest to him, and fall the most under his cognizance. Salmasius had before made some remarks to the same purpose upon this work, which was first published by himself at Basil, in 1533, in quarto; afterwards with a Latin version, and notes, by Gerard Mercator, at Amsterdam, 1605; which last edition was reprinted at the same place, 1618, in folio, with neat geographical tables by Bertices.
Other works of Ptolemy, though less considerable than these two, are still extant, as "Fabri quatuor de judiciis Astrorum,' upon the first two books of which Cardan wrote a commentary, "Fructus librorum suorum," a kind of supplement to the former work," Recentio Chronologica Regum;" this, with another work of Ptolemy, "De Hypothesibus Planetarum," was published in 1620, 4to. by John Bainbridge, the Savilian Professor of Astronomy at Oxford, and Scaliger, Palavius, Dodwell, and the other chronological writers have made great use of it. "Apparentia Stellarum Inerrantium;" this was published at Paris by Petavius, with a Latin version, 1630, in folio; but from a mutilated copy, the defects of which have since been supplied from a perfect one, which Sir Henry Saville had communicated to archbishop Usher, by Fabricius, in the third volume of his Bibliotheca Græca, "Elementarum Harmonicarum libri tres," published in Greek and Latin, with a commentary, by Porphyry, the philosopher, by Dr. Wallis, at Oxford, 1682, in 4to.; and afterwards reprinted there, and inserted in the third volume of Wallis's works, 1699, in folio.
Marbillon exhibits, in his German Travels, an effigy of Ptolemy looking at the stars through an optical tube; which effigy, he says, he found in a manuscript of the thirteenth century, made by Conradus, a monk. Hence, some have fancied, that the use of the telescope was known to Conradus. But this is only matter of mere conjecture, there being no facts or testimonies, nor even probabilities, to support such an opinion.
It is likely that the tube was nothing more than a plain open one, employed to strengthen and defend the eyesight, when looking at particular stars, by excluding adventitious rays from other stars and objects, a contrivance which no observer of the heavens can ever be supposed to have been without.
APOLLODORUS, a famous architect, a native of Damascus, who lived in the reigns of Trajan and Adrian. He was builder of the stone bridge thrown over the Danube by Trajan, one of the most splendid works of that emperor. He likewise constructed the edifices round the Forum Trajanum in Rome, among which was a triumphal arch, as well as the sculptured column still existing, and bearing the name of Trajan. Dion attributes to this architect a college and theatre for music. The rudeness with which he treated Adrian cost him dear. That prince being present at a conversation between Trajan and Apollodorus on some plans of architecture, interfered with his opinion, on which Apollodorus bid him " go and paint gourds,' an amusement he was fond of," and not expose his ignorance in matters he did not understand." Adrian never forgot the affront, and when he became emperor refused to employ this architect. To show him that he did not want his services, he sent him the plan of a sumptuous temple of Venus he was building, and asked him what he thought of it. Apollodorus made some just criticisms upon it, which only aggravated his former offence. The emperor, who was meanly jealous of men of talent, banished him, and, having caused him to be accused of various crimes, put him to death.
ARCHELAUS, the son of Apollonius, one of the greatest sculptors of antiquity, was a native of Ionia, and is thought to have lived in the time of the emperor Claudius. He executed, in a marble, the Apotheosis of Homer. This masterpiece in sculpture, was found in 1568, in a place named Frattocchia, belonging to the princes of Colonna, where, it is said, the emperor Claudius had a pleasure house. Father Kircher, Cupert, Spanheim, and several other learned antiquaries have given a description and explication of this work.
ZENODORUS, a sculptor in the age of Nero. He made a statue of Mercury, as also a colossus for the emperor, which was 110 feet high, and which was consecrated to the sun. The head of this colossus was some time after broken by Vespasian, who placed there the head of an Apollo, surrounded with beams.
AGASIAS, a sculptor of Ephesus, and the disciple, if not the son, of Dositheus. He is celebrated by his admirable sta
tue called the Gladiator, which was found with the Apollo Belvidere at Nettuno, formerly Antium, the birth place of Nero. It is still in great preservation, except the right arm, which was restored by Algardi.
POLYDORUS, a celebrated carver of Rhodes, who with one stone made the famous statue of Laocoon and his children. AGESANDER, a sculptor of Rhodes under Vespasian, who made a representation of Laocoon's history, which now passes for the best relict of all ancient sculpture.
ATHENODORUS, a celebrated sculptor, whose work, conjointly with Agesander and Polydorus, was the celebrated group of Laocoon, at Rome.
RABIRIUS in the reign of Domitian. He built a celebrated palace for the emperor, of which the ruins are still seen at Rome.
CELIUS AURELIANUS, or, as some have called him Lucius Coelius Arianus, an ancient physician, and the only one of the sect of the methodists of whom we have any remains, was of Sicca, a town of Numidia, in Africa. This we learn from the elder Pliny, as we might almost have collected it, without any information at all, from his style, which is very barbarous, and much resembling that of the African writers. It is half Greek, half Latin, harsh, and difficult, yet strong, masculine, full of good sense, and valuable for the matter it contains. It is frequently very acute and smart, especially where he exposes the errors of other physicians, and always nervous. What age Coelius Aurelianus flourished in, we cannot determine, there being so profound a silence about it among the ancients; but it is very probable that he lived before Galen; since it is not conceivable that he should mention, as he does, all the physicians before him, great as well as small, and yet not make the least mention of Galen. He was not only a careful imitator of Soranus, but also a strenuous advocate for him. He had read over very diligently the ancient physicians of all the sects; and we are obliged to him for the knowledge of many dogmas, which are not to be found but in his books, "De celeribus et tardis passionibus." The best edition of these books is that published at Amsterdam, in 1722, in 4to. He wrote, as himself tells us, several other works; but they have all perished.
THESSALUS, a celebrated physician of Lydia, who flourished at Rome, in the reign of Nero, and came into great practice among the patricians. He adopted the system of Themison, the founder of the methodists, and was rather more vio