Page:Encyclopædia Britannica, Ninth Edition, v. 19.djvu/472

Rh 452 P N P N II. SEXTUS POMPEITJS MAGNUS (75-35 B.C.), the younger son of Pompey the Great, born 75 B.C., continued after his father s death to prolong the struggle against the new rulers of the Roman empire. Cesar s victory at Munda in 45 drove him out of Corduba (Cordova), though for a time he held his ground in the south of Spain, and defeated Asinius Pollio, the governor of the province. In 43, the year of the triumvirate of Octavius, Antony, and Lepidus, he was proscribed along with the murderers of Ciesar, and not daring to show himself in Italy he put himself at the head of a fleet manned chiefly by slaves or proscribed persons, by means of which he made himself master of Sicily, and from thence ravaged the coasts of Italy. Rome was threatened with a famine, as the corn supplies from Egypt and Africa were cut off by his ships, and it was thought prudent to negotiate a peace with him, which was to leave him in possession of Sicily, Sardinia, and Achaia, provided he would allow Italy to be freely sup plied with corn. But the arrangement could not be carried into effect, as Sextus renewed the war and gained some considerable successes at sea. However, in 36 his fleet was defeated and destroyed by Agrippa off the north coast of Sicily, and in the following year he was murdered at Mitylene by an officer of Antony. He had his father s bravery as a soldier, but seems to have been a rough uncultivated man. (w. j. B.) PONCE DE LEON, Luis. See LEON, Luis PONCE DE. PONCELET, JEAN VICTOR (1788-1867), mathemati cian, was born at Metz, July 1, 1788. From 1808 to 1810 he attended the Polytechnic School, and afterwards, till 1812, the Practical School at Metz. He then became lieutenant of engineers, and took part in the Russian campaign, during which he was taken prisoner and was confined at Saratoff on the Volga. It was during his imprisonment here that, &quot; priv^ de toute espece de livres et de secours, surtout distrait par les malheurs de ma patrie et les miens propres,&quot; as he himself puts it, he began his researches on projective geometry which led to his great treatise on that subject. This work, the Traite des Proprietes Projectives des Figures, which was published in 1822 (2d ed., 1865), is occupied with the investiga tion of the projective properties of figures, that is, such properties as are not altered by projection. In his inves tigation he employs the ideas of continuity, of homologous figures, and of reciprocal polars ; and by means of these, without any analysis, he was able to establish all the known properties of lines and surfaces of the second degree, and to discover others unknown before. This work entitles Poncelet to rank as one of the greatest of those who took part in the development of the modern geometry of which Monge was the founder. From 1815 to 1825 he was occu pied with military engineering at Metz; and from 1825 to 1835 he was professor of mechanics at the Practical School there. In 1826, in his Memoire sur les Roues Hy- drauliques a Aubes Courbes, he brought forward improve ments in the construction of water-wheels, which more than doubled their efficiency. In 1834 he became a member of the Academy ; from 1838 to 1848 he was professor to the faculty of sciences at Paris, and from 1848 to 1850 com mandant of the Polytechnic School, where he effected a reform in the course of study. At the London Interna tional Exhibition in 1851 he had charge of the department of machinery, and wrote a report on the machinery and tools on view at that exhibition. He died December 22, 1867. Besides those referred to above, he wrote a number of works, and contributed many papers to Crelle s Journal, &c., on different branches of engineering and mathematics. POND, JOHN (c. 1767-1836), astronomer-royal, was born about 1767 in London, where his father made a fortune iu trade. He entered Trinity College, Cambridge, at the age of sixteen, but took no degree, his course being interrupted by severe pulmonary attacks which compelled a prolonged residence abroad. His travels extended from Lisbon to Constantinople and the Nile, and were turned to account for astronomical observation. In 1800 he settled at Westbury near Bristol, and began to determine star-places with a fine altitude and azimuth circle of 2i feet diameter by Troughton. His demonstration in 1806 (Phil. Trans., xcvi. 420) of a change of form in the Greenwich mural quadrant led to the introduction of astronomical circles at the Royal Observatory, and to his own appointment as its head. Elected a fellow of the Royal Society, February 26, 1807, he married and went to live in London in the same year, and in 1811 succeeded Maskelyne as astronomer-royal. During an administration of nearly twenty-five years, Pond effected a reform of practical astronomy in England comparable to that effected by Bessel in Germany. In 1821 he began to employ the method of observation by re flexion; and in 1825 he devised means (see Mem. R. A. Soc., ii. 499) of combining two mural circles in the determination of the place of a single object, the one serving for direct and the other for reflected vision. (By an invention of Airy s, the same object is now attained with one instru ment.) During Pond s term of office the instrumental equipment at Greenwich was completely changed, and the number of assistants increased from one to six. The superior accuracy of his determinations was due in part to his systematic attention to the errors of his instruments, in part to his plan of multiplying observations. During a prolonged controversy (1810-24), he consistently denied the reality of Brinkley s imaginary star-parallaxes (see his papers in Phil. Trans., cviii. 477 ; cxiii. 53). Delicacy of health impeded his activity, and compelled his retirement in the autumn of 1835. He died at Blackheath, September 7, 1836, and was buried beside Halley in the churchyard of Lee. The Copley medal was conferred upon him in 1823, and the Lalande prize in 1817 by the Paris Academy, of which he was a corresponding member. He published eight folio volumes of Greemvich Observations, translated Laplace s Systeme du Monde (in 2 vols. 8vo., 1809), and contributed thirty-one papers to scientific collections. His catalogue of 1112 stars (1833) was of great value. See Mem. R. A. Soc., x. 357; Annual Biography and Obituary, 1837; Grant, Hist, of Phys. Aatr., p. 491; Royal Society s Cat. of Sc. Papers. PONDICHERRI, chief settlement of the French posses sions in the East Indies, situated on the Corornandel coast, in 11 56 N. lat. and 79 53 E. long. ; it is 86 miles south of Madras, and is connected with the South Indian Railway system. The territory consists of three districts Pondi- cherri, Villianur, and Bahur comprising an area of 112 square miles, with a population in 1881 of 139,210. The town is divided into a European and a native quarter, separated from one another by a canal. The French first settled at Pondicherri in 1674; it was besieged four times by the British, the last time in 1793 ; but it was finally restored in 1816. On the whole the town is considered very salubrious ; the purity of its water-supply is said to be unrivalled in any other town in southern India. PONEVYEZH, a district town of Russia, in the govern ment of Kovno, situated on the upper course of the Nevyeja river, and connected by rail with Libau on the north-west and with Diinaburg (80 miles distant) on the east. It is an old town which was almost totally destroyed by the pestilence of 1550, but was rebuilt and repeopled owing to its advantageous situation on the highway to the Baltic. After having suffered severely from wars in the 17th and 18th centuries it was annexed to Russia on the