OBOLUS OCEAN. 



287 



fore used more properly for the basis of harmony. 

 There are some musicians, however, who play solos 

 on the double bass. 



OBOLUS ; a Grecian coin of silver or copper, 

 the sixth part of a drachm, about lOf pence in 

 value. In early times, instead of money were used 

 little pointed pieces of iron, or of copper (o/SaXo;, 

 af, a spit). Six of these filled the hand, and 

 made a drachm. The same name was afterwards 

 given to a small silver coin. The Greeks placed an 

 obolus in the mouth of the dead, to pay Charon for 

 their passage over the Styx. In weight, the obolus 

 is likewise the sixtli part of a drachm ; the latter 

 coin, however, is not always of the same value. 



OBOTRITES; a Vandal tribe. See Mandate. 



OBSCURANTISM (from Latin obscurare); a 

 word not unaptly used in Germany to denote the 

 endeavours of certain men to prevent the diffusion 

 of intelligence. It is used in science as well as in 

 religion, and might very properly be applied in 

 politics. 



OBSERVANTS. See Franciscans. 



OBSERVATORY; a building constructed for 

 astronomical observations, from which there is an 

 unobstructed view of the heavens, and in which the 

 instruments are safe from agitation and other distur- 

 bances. There are, for instance, large astronomical 

 telescopes, always placed in the direction of the 

 meridian, and the internal arrangement of the build- 

 ing is such as to facilitate the observations ; the roof 

 is also flat, to favour the view to the horizon. The 

 instruments in an observatory are quadrants, sex- 

 tants, and octants, transit, equatorial, parallactic, 

 and circular instruments, achromatic and reflecting 

 telescopes, night and day telescopes, chronometers, 

 compasses, &c. We find mention of observatories at 

 a very early period : Diodorus (ii. 9) tells us of a 

 tower, from which the Chaldaean astronomers made 

 their observations, in the temple of Belus, at Baby- 

 lon. Copernicus was the first who (1540) set an 

 instrument in the meridian. The first regular obser- 

 vatory was erected at Cassel in 1561. Among the 

 modern European observatories, the most celebrated 

 are those of Paris (erected in the reign of Louis 

 XIV., 166472), of Greenwich (built in 1672), and 

 of Palermo (erected by Piazzi, 1789). That on the 

 Seeberge, hear Gotha, has acquired celebrity through 

 Zach (q. v.), and that of Konigsberg through Bessel; 

 of the latter Bessel has given an account in his 

 Beobachtungen auf der Universit-Sternwarte (1814 

 seq.). There are also similar establishments at Am- 

 sterdam, in Batavia, at Berlin, Bologna, Breslati, 

 Cambridge, Cape-town, Dublin, Edinburgh, Florence, 

 Genoa, Gottingen, Hamburg, Copenhagen, Leipsic, 

 Leyden, Lilienthal (near Bremen), Lisbon, Milan, 

 Manheim, Marseilles, Moscow, Munich, Naples, Ni- 

 colaieff, Oxford, Padua, Petersburg, Pisa, Plymouth, 

 Portsmouth, Prague, Rome, Slough (Herschel's), 

 Stockholm, Toulouse, Upsal, Vienna, &c. China, is 

 indebted to the Jesuits for one at Pekin, erected 

 towards the end of the seventeenth century ; and 

 another has been built at Paramatta, in New South 

 Wales. Although observatories are generally pro- 

 vided with numerous and costly instruments, yet for 

 most purposes, a meridian circle of two, or at most 

 three feet diameter, a four or five feet telescope, and 

 a good clock, are sufficient. 



OBSIDIAN. Sec Pitchstone. 



OCANNA. See Colombia. 



OCCAM or OCKHAM, WILLIAM, an eminent 

 philosopher of the fourteenth century, a native of 

 Ockham in Surrey, was educated at Merlon college, 

 Oxford. He studied under the celebrated Duns Sco- 

 tus, whose opinions he, notwithstanding, controverted, 

 becoming the founder of the philosophical sect of the 



Nominalists, as Scotus was of the Realists. Occam 

 entered into the Franciscan order of Friars Minor, or 

 Cordeliers ; and he also took orders in the church, 

 and became archdeacon of Stowe, in the diocese of 

 Lincoln, which preferment he resigned about 1320. 

 He wrote against pope John XXII., whom he 

 treated as a heretic, and joined the anti-pope Nicho- 

 las V., set up by the emperor Louis of Bavaria. He 

 died at Munich in 1347. He was well acquainted 

 with the Scriptures, and with the philosophy of Aris- 

 totle, and possessed a subtle genius and much elo- 

 quence. Among his works are Commentarium super 

 Sententias (lib. iv.) ; Quodlibeta; De Ingressu Scien- 

 tiarum ; and a treatise against the pope, De Pauper- 

 tate CJiristi et Apostolorum. He obtained the title 

 among the schoolmen, of the Invincible Doctor. See 

 Nominalists and Scholastics. 



OCCASIONAL CAUSES. The doctrine of occa- 

 sional causes was developed in the school of Des- 

 cartes. Before him it was considered that the body 

 influences the soul, and causes motions in it, and vice 

 versa. This was called systema influxus physici. 

 Descartes impugned this indirectly by his dualism, 

 which he reconciled by making God the cause of all 

 motion. Louis de la Forge, his scholar, also makes 

 God the cause of all motion, but considers a mutual 

 connexion to exist between soul and body, so that 

 the one is never moved by God without influencing 

 the other. Geulin developed the system further, and 

 made God the original cause of every motion pro- 

 duced by one of the two parts on the other. 



OCCIDENT ; a word much used in the historical 

 works of the European continent, in contradistinction 

 to Orient; for instance, Occidental languages, Occi- 

 dental empire. See Western Empire. 



Occident, in astronomy and geography, is the 

 same as westward, or point of the horizon where the 

 sun sets. A planet is said to be accident when it 

 sets after the sun. 



OCCULTATION ; the obscuration of a planet or 

 star by the interposition of the moon, or other planet, 

 between it and our eye. The name of immersion is 

 given to the state of a star or planet, when it is so 

 near the sun as to be invisible ; also to that of the 

 moon when she begins to be darkened by entering 

 into the shadow of the earth. 



OCCUPANCY, in law. See Land, Property in ; 

 Natural Law, and Public Lands. 



OCEAN ; the great mass of waters which surrounds 

 the land, and which probably extends from pole to 

 pole, covering nearly three quarters of the globe. 

 For the sake of convenience, we distinguish different 

 parts of it under the names of seas, bays, git If s, 

 sounds, and even give the name of ocean to large 

 portions which are partially divided from each other 

 by the continents. But these divisions are arbitrary. 

 The following classification, adopted fay Malte-Brun, 

 in his System of Geography, has, at least, the advan- 

 tage of showing, in a striking manner, the connexion 

 which exists between the great masses of water. . 



