PTOLEMT III. PUBERTY amity with the rising republic of Rome. He founded a gymnasium at Athens, and planted numerous colonies in various parts of his for- eign dominions, which comprised Phoenicia, Ccele-Syria, Palestine, Cyprus, the Cyclades, and portions of southern Asia Minor, Ethio- pia, Arabia, and Libya. The effeminacy of his court increasing with the wealth of the coun- try, he came at length to lead the indolent life of a refined voluptuary. Repudiating his first wife, Arsinoe, daughter of Lysimachus, he mar- ried his own sister Arsinoe, widow of Lysima- chus, which the Egyptian law allowed, but she brought him no children. Another stain on his memory is the execution of two of his brothers, for which his surname, which he him- self had assumed to signalize his attachment to his sister, became a subject of derision. PTOLEMY III., surnamed EUERGETES, eldest son and successor of the preceding, by Arsinoe, daughter of Lysimachus, died in 222 B. C. On coming to the throne ho found in the public treasury an immense amount of money, and at his command a vast army and navy. His war- like ardor was roused by the ill treatment and subsequent murder of his sister Berenice, wife of Antiochus Theos, king of Syria. With a largo army he ravaged Syria and its eastern provinces, advancing as far as Susa, and, with- out establishing his authority in any now pos- sessions, brought back immense booty in gold and silver, and the Egyptian idols which Cam- byses had carried off to Persia. For this the Egyptians called him Euergetes (benefactor). In right of his wife Berenice, daughter of Magas, Gyrene was united to his dominions, and he made large acquisitions of territory in Arabia and Abyssinia. lie inherited the religious lib- erality and love of learning of his progenitors, and was like them a proficient in letters. PTOLEMY, Claudius a Hellene-Egyptian math- ematician, astronomer, and geographer, said to have been born in Pelusium, flourished at Alexandria in the 2d century A. D. Scarcely any particulars of his life are known. His MfydX^ 2(jvrai;if TIK 'Aorpovo/w'af, or " Great Astronomical Construction," contains nearly all that is known of the astronomical observa- tions and theories of the ancients, and is gen- erally cited under the Latin titles Syntaxu Jfathematica and Conttruetio Mathematica. The most important port of this work is a cat- alogue of stars, deduced from that constructed by Hipparchus. (See PRECESSION.) The Syn- taxis treats of the relations of the earth and heavens ; the effect of position upon the earth ; the theory of the sun and moon, with- out which that of the stars cannot be under- taken ; the sphere of the fixed stars ; and the determination of the planetary orbits. He places the earth in the centre of the universe, and the Ptolemaic system, based on the theo- ries of Hipparchus, was universally received till the time of Copernicus. During all that interval the history of astronomy presents scarcely anything more than comments on Ptolemy's writings. But for the Arabians the Syntaxis would probably hove perished. It was translated by them in the reign of the caliph Al-Mamoun, son of Haroun al-Rashid (about 827), and handed down under the title of Almagest. Translations from the Arabic were made into Latin, but the Greek text was subsequently also discovered in Byzantine man- uscripts. Ptolemy left a copious account of the manner in which Ilipparchus established his theories, and in most of the branches of the subject gave additional exactness to what that astronomer had done. He computed, notwithstanding the fundamental errors and the inaccuracies of his system, the eclipses of the next six centuries ; determined the plane- tary orbits; and is commonly said to have discovered the moon's second inequality or evection, though it is probable that Ilippar- chus really detected this inequality. Three observations cited by Ptolemy in support of his theory were borrowed from Ilipparchus, and the nature of one of them suggests that they were taken from a great mass of obser- vations, though Ptolemy himself says nothing to that effect. The astronomer who took a predecessor's star catalogue, and adding a con- stant correction to each star published it as the result of his own observations, would have left unnoticed all lunar observations by Hip- parchus not absolutely necessary to establish his own theory. As a geometer Ptolemy has been ranked as certainly the fourth among the ancients, after Euclid, Apollonius, and Archi- medes. He caused light to pass through media of unequal density, and thus discovered re- fraction, and he is said to have first recognized the alteration of the apparent position of a heavenly body which is due to this cause ; but here again it is probable that Hipparchus anticipated him. Ptolemy wrote a universal geography, which continued to be the standard text book till the 16th century. He was the first to use the terms latitude and longitude, by which he laid down the position of each country and town. He proved the earth to be a globe, and calculated its inhabited parts to extend from the meridian of Thin, Ion. 119 30' E. of Alexandria, to the meridian of the Islands of the Blessed, 60 80' W. ; and from the parallel of Meroe, about lat. 16 80' N., to that of Thule (Iceland or the Shetland islands), 63 N. The maps of this geography have been preserved with it. After him no one attempted for many centuries to reform geography except in the improvement of de- tails. He was distinguished also as a musician, and wrote treatises on music, mechanics, chro- nology, and astrology; but probably most of these works were mere compilations. The best edition of the Almagest is by Halma (Greek text with French translation, 2 vols. 4to, Paris, 1813-'16). PUBERTY, the period of youth characterized by the acquirement of functional power in the reproductive apparatus of the sexes; its ac-
