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IV. Claudius Ptolemaeus

A famous Greek mathematician, astronomer, and geographer. He came from Ptolemaïs Hermeiou (ruins at modern Menschie), in Upper Egypt, and lived and worked in the second century A.D. The most important of his writings which have been preserved are: (a) Γεωγραφικὴ Ὑφήγησις (“instructions for the drawing of maps”), a geographical work in eight books, the first of which contains the principles of mathematical geography, the drawing of maps, and the calculation of the longitudes and latitudes of places in the then known world; books ii.-vii. contain tables of names of places in the maps described, arranged according to degrees and their subdivisions; and book viii. contains an astronomical table of climates. This work is one of the chief sources of our knowledge of ancient geography. It is edited by Nobbe (Leipzig, 1845); and Müller (Paris, 1883). (bΜεγάλη Σύνταξις τῆς Ἀστρονομίας, usually known by its Arabic name of Almagest. Since the Tetrabiblus, the work on astrology, was also entitled σύνταξις, the Arabs, to distinguish the two, probably called the greater work μεγάλη, and afterwards μεγίστη: the title Almagest (Tabrir al Magesthi) is a compound of this last adjective and the Arabic article. The Almagest is divided into thirteen books. It treats of the relations of the earth and heaven; the effect of position upon the earth; the theory of the sun and moon, without which that of the stars cannot be undertaken; the sphere of the fixed stars, and those of the five stars called planets. The seventh and eighth books are the most interesting to the modern astronomer, as they contain a catalogue of the stars. This catalogue gives the longitudes and latitudes of 1022 stars, described by their positions in the constellations. It seems that this catalogue is in the main really that of Hipparchus, altered to Ptolemy's own time by assuming the value of the precession of the equinoxes given by Hipparchus as the least which could be, some changes having also been made by Ptolemy's own observations. Indeed, the whole work of Ptolemy appears to have been based upon the observations of Hipparchus, whom he constantly cites as his authority. Ptolemy's system of the heavens, which made the earth the fixed centre, was not superseded till the time of Copernicus (A.D. 1473-1543). The best edition of the Almagest is by Halma, 2 vols. (Paris, 1813-16). (c) Τετράβιβλος Σύνταξις, generally called Tetrabiblos, or Quadripartitum de Apotelesmatibus et Iudiciis Astrorum. With this goes another small work, called Καρπός, or Fructus Librorum Suorum, often called Centiloquium, from its containing a hundred aphorisms. Both of these works are astrological, and it has been doubted by some whether they be genuine. But the doubt merely arises from the feeling that the contents are unworthy of Ptolemy. (d) Κανὼν Βασιλέων, a catalogue of Assyrian, Persian, Greek, and Roman sovereigns, with the length of their reigns, several times referred to by Syncellus. (eΦάσεις ἀπλανῶν ἀστέρων καὶ συναγωγὴ ἐπισημασειῶν, De Apparentiis et Significationibus inerrantium, an annual list of sidereal phenomena. (f, g) De Analemmate and Planisphaerium. These works are obtained from the Arabic. The Analemma is a collection of graphical processes for facilitating the construction of sun-dials. The Planisphere is a description of the stereographic projection, in which the eye is at the pole of the circle on which the sphere is projected. (h) Περὶ ὑποθέσεων τῶν πλανωμένων, De Planetarum Hypothesibus. This is a brief statement of the principal hypotheses employed in the Almagest for the explanation of the heavenly motions. (i) Ἁρμονικῶν βιβλία γ́., a treatise on the theory of the musical scale, and the most important ancient work on music next to that of Aristoxenus. Most of the works of Ptolemy are contained in the edition of Halma in 4 vols. (Paris, 1813-28). The principal MSS. are at Vienna, Venice, and Mount Athos. This last is photographed and published by Langlois (Paris, 1866).

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