Page:Encyclopædia Britannica, Ninth Edition, v. 17.djvu/775

O B S O C C 717 and a First Melbourne Catalogue of 1227 stars was published in 1874. Adelaide (South Australia), lat. -3455 33" 8,long. 9 h 14 m 21 s 3E. In operation since 1861 ; has been gradually improved, and contains now an 8-iuch equatorial by Cooke, and a transit circle has been ordered. (J. L. E. D.) INDEX OF OBSERVATORIES. Abo, 714. Adelaide, 717. Albany, 715. Cambridge, U.S., 715. Cape of Good Hope, 716. Chapultepec, 716. . Geneva, 713. Georgetown, 715. Glasgow, 710. Lima, 716. Lisbon, 713. Liverpool, 710. Olmiitz, 713. Ormskirk (Dawes), 711. Orwell Park (Tomline), Slough (Herschel), 711. Southwark (South), 711, Spires, 713. Algiers, 716. Allegheny, 715. Chicago, 715. Christiania, 714. Glasgow, U.S., 715. Gotha, 712. Lucknow, 716. Lund, 714. 711. Oxford (Radcliffe), 710. Starfield (Lassell), 711. Stockholm, 714. Altona, 712. Cincinnati, 715. Gb ttingen, 712. Lyons, 712. Oxford (Univ.), 710. Stonyhurst, 711. Amherst, 715. Clinton, 715. Greenwich, 710. Madison, 715. Padua, 713. Strasburg, 713. Annapolis, 715. Coimbra, 713. Hamburg, 712. Madras, 716. Palermo, 714. Sydney, 716. Ann Arbor, 715. Armagh, 710. Copenhagen, i 15. Cordova, 716. Hanover, U.S., 715. Hartwell (Lee), 711. Madrid, 713. Mannheim, 713. Paramatta, 716. Paris, 712. Tarnbank (Fletcher), 711. Tashkend, 716. Athens, 714. Cork, 711. Hastings, U.S., 715. Markree (Cooper), 711. Peking, 716. Tiflis, 714. Bedford (Smyth), 711. Cracow, 713. Hayes (Hussey), 711. Marseilles, 712. Plonsk, 714. Toulouse, 712. Berlin, 712. Cranbrook (Dawes), 711. Helsingfors, 714. Melbourne, 716. Pola, 713. Trivandrum, 716. Bermerside (Crossley), Cranford (De La Rue), Hereny, 713. Meudon, 712. Potsdam, 713. TulseHill(Hiiggins), 711. 711. 711. Hong Kong, 716. Milan, 713. Prague, 713. Turin, 713. Birr Castle (Rosse), 711. Cuckfield (Knott), 711. Hopefield (Dawes), 711. Modena, 714. Princeton, 715. Upsala, 714. Blackheath (Groom- Dorpat, 714. Kalocza, 713. Montsouris, 712. Pulkowa, 714. Utrecht, 715. bridge), 711. Dresden, 712. Kasan, 714. Moscow, 714. Redhill (Carrington) 711 Vienna, 713. Blackheath (Wrottesley), Dublin, 710. Kensington (South), 711. Mount Hamilton, 715. Regent s Park (Bishop), Vienna (Oppolzer), 713. 712. Dun Echt(Crawford),711. Kew, 710. Munich, 713. 711. Vilna, 714. Bologna, 714. Durban, 716. Kharkoff, 714. Naples, 714. Rio de Janeiro, 716. Warsaw, 714. Bonn, 712. Durham, 710. Kieff, 714. Neuchatel, 713. Rochester, U.S., 715. Washington, 715. Bothkamp, 712. Dtisseldorf, 712. Kiel, 712. New Haven, 715. Rome (Capitol), 714. Wateringbury (Dawes), Bremen, 712. Baling (Common), 711. Konigsberg, 712. New York, 715. Rome (Coll. Rom.), 714. 711. Breslau, 712. Edinburgh, 710. Kremsmunster, 713. Nice, 712 Rugby, 711. Wilhelmshafen, 713. Brussels, 715. Etna, 714. Leipsic, 713. Nikolaieff, 714. St Helena, 716. Williamstown, 716. Budapest, 713. Florence, 714. Leyden, 715. Northfield, 715. St Petersburg, 714. Windsor, N.S.W., 716. Cadiz, 713. Gallarate, 714. Leyton (Barclay), 711. Odessa, 714. Santiago, 716. Wrottesley Hall, 712. Cambridge, 710. Gateshead (Newall), 711. Lilienthal, 713. O Gyalla, 713. Senftenberg, 713. Zurich, 713. OBSIDIAN, a volcanic glass, said to have been named after its discoverer Obsidius. It is usually of black, brown, or grey colour, and in some varieties banded or striated. The colour is generally due not so much to the vitreous mass itself as to the presence of minute foreign bodies or micro- lites, which in some cases appear to be incipient crystals of felspar, while in others they probably consist of such minerals as augite, hornblende, biotite, and magnetite. These microscopic enclosures are occasionally arranged in curved lines, producing beautiful examples of fluidal struc ture (see GEOLOGY, vol. x. p. 230, fig. 2). Spherulites are not uncommon in obsidian, and are sometimes suffi ciently large to impart a distinctly globular structure to the stone. Other varieties are rich in microscopic pores, or may even present to the naked eye a vesicular texture. It is notable that certain kinds of obsidian possess a peculiar metallic sheen, which has been attributed by Professor Zirkel to the presence of minute ovoid enclosures, and not to a porous structure, as had been previously suspected. There can be no doubt that obsidian has been formed by the rapid cooling of a felspathic lava. It is found chiefly in Iceland, the Lipari Islands, Melos and other isles of the Greek archipelago, the Caucasus, Siberia, Mexico, Peru, and New Zealand. Obsidian breaks with a beautifully conchoidal fracture, yielding sharp-edged fragments, which have been largely used in various parts of the world as arrow-points, spear heads, and rude knives. For these purposes it was exten sively employed, under the name of itztli, by the ancient Mexicans, who quarried it at the Cerro de las Navajas, or "Hill of Knives," near the head-waters of the Great Barauca. Obsidian has also been used as a mirror, a purpose for which its strong lustre has recommended it. By the ancient Greeks and Romans it was worked as a gem-stone ; and, in consequence of its having been often imitated in black glass, there arose among collectors of gems in the last century the curious practice of calling all antique pastes " obsidians." Even at the present day the bottle-green varieties of obsidian are occasionally cut and polished as ornamental stones. They bear some re semblance to peridotes and tourmalines, but are deficient in hardness. OCCAM, WILLIAM OF (d. c. 1349), the great English schoolman (Doctor invincibilis), was born in the village of Ockham in the county of Surrey in the end of the 13th century. Scarcely any traces of his early life remain. Un- attested tradition says that the Franciscans persuaded him while yet a boy to enter their order, sent him to Oxford to Merton College, and to Paris, where he was first the pupil, then the successful rival, of the celebrated John Duns Scotus. He was at the height of his fame as a lecturer in the university of Paris when the famous quarrel arose between Philip the Fair and Pope Boniface VIII., but it does not appear that he took any part in the strife. 1 He probably left France about 1314, and there are obscure traces of his presence in Germany, in Italy, and in England during the following seven years. We only know that in 1322 he appeared as the provincial of England at the celebrated assembly of the Franciscan order at Perugia, and that there he headed the revolt of the Franciscans against Pope John XXII. His share in this revolt and his writings to justify his position gave rise to his trial for heresy before the bishops of Ferrara and Bologna, which resulted in his imprisonment for seventeen weeks in the dungeons of the papal palace at Avignon. He and his companions Michael of Cesena, general of the order, and Bonagratia managed to escape, and found their way to Munich, where they formed the most conspicuous members of that band of Franciscans who aided Louis of Bavaria in his long contest with the papal curia. "Defend me with the sword and I will defend you with the pen," was Occam s proposal to Louis ; and from their haven of refuge at Munich the recusant Franciscans sent forth books and pamphlets refuting the extravagant pretensions of papal authority. Michael of Cesena died in 1342, and Occam, who had received from him the official seal of the order, was recognized as general by his party. The date of his death and the place of his burial are both uncertain. He probably died at Munich in 1349, and was buried in the graveyard of the Franciscan convent. Some writers assert that he was reconciled to Rome, and in proof of submission sent the official seal to William Farinerius, who had been ap pointed general of the order by the pope ; others declare that, like Cesena and Bonagratia, he died excommunicate. William of Occam was the most prominent intellectual leader in an age which witnessed the disintegration of the 1 The famous Disputatio super Potestate Prselatis Ecclesite, atquePrin- cipibus Terrarum commissa, which belongs to this controversy, and has been commonly attributed to Occam, was probably written by Peter Dubois. a Parisian lawyer.