OBS 



513 



O CE 



nutrt, deviation from parallelism, or from 

 perpendicularity. The obliquity of the 

 ecliptic is the angle which the ecliptic 

 makes with the equator ; it is 23, 27'. 



OB'LONG. In geometry, a rectangle 

 whose length is greater than its breadth. 

 OBOE (It.) A musical wind instrument 

 sounded through a reed. 



OB'OLUS, efaXof. A brass coin among 

 the ancient Greeks, worth about a penny 

 farthing sterling. 



OB'OVATE. Ovate with the broader end 

 uppermost : ob and ovatut, ovate. Applied 

 to leaves. 



OBSCU'RANTS. A nickname, applied in 

 Germany to those writers who sought to 

 obstruct the progress of enlightenment. 



OBSER'VANTS. A branch of the Francis- 

 can order. 



OBSERVATION, from observe. A term, in 

 astronomy and navigation, for the opera- 

 tion of measuring, with some proper in- 

 strument, the angular distance, altitude, 

 &c., of a celestial body. 



OBSER'VATORT, Lat. obiervatorium. A 

 place fitted up with the proper instru- 

 ments and conveniences for observing 

 the heavenly bodies. Observatories are 

 usually built in the form of a tower, and 

 covered with a terrace. Those of Green- 

 wich, Paris, Munich, and Palermo, are 

 the most celebrated ones of modern times. 

 That of Greenwich was built in 1676, by 

 order of Charles II., at the instance of 

 Sir Jonas Moore, surveyor-general of the 

 ordnance ; a circumstance from which 

 the office of astronomer-royal has been 

 placed under that department. 



OBSID'IAN. A volcanic production of a 

 greenish-black colour ; the Obsidianwn 

 vitrum of Pliny, and vernacularly termed 

 volcanic glass. It is a compound of silica, 

 alumina, potash, lime, soda, with slight 

 admixture of the oxides of iron and man- 

 ganese. The fracture is either vitreous 

 or pearly : hence the two varieties, vitre- 

 ous obsidian and pearl-stone. 



OBSID'IAN-STONE. The Obsidiamts lapis 

 of Pliny. Another name for the Chian 

 marble. 



OBSID'IONAL COINS, are such as were 

 struck in a besieged place, to supply the 

 scarcity of other current money. 



OBSID'IONAL CROWN. A crown or gar- 

 land made of the grass, &c. which grew 

 in a besieged place, and given by the Ro- 

 mans to the general who delivered it 

 from the enemy. 



OBSTRCA'TOR. A stopper up ; from 06- 

 strtto, to stop up. The name of two 

 muscles of the thigh, which shut up the 

 aperture between the os pubis and the 

 hip-bone, and rotate the thigh. 



OB'STRFENT, Lat obstnuns, hindering, 

 from obstruo, to hinder. Obstruents are 

 medicines supposed to bave the power of 



closing the orifices of the ducts or vesMjla 

 of the body. 



OBTEM'PER, Lat. obtcmpero, I obey. In 

 Scotch law, to comply with, the judgment 

 of a court. 



OBTURA'TOR MUSCLES Lat. obturare, to 

 close up. Muscles which fill up openings 

 in the bones. 



OBTC'SE, Lat. obtustis, blunt : opposed 

 to acute. An obtuse angle is one greater 

 than 90 or a right angle ; an acute angle 

 s less than 90. See ANGLE. 



OB'VERSE. 1. In numismatics, the side 

 of a medal or coin on which is the face or 



head ; the other side is the reverse. 2. 



An obverse leaf is one having the base 

 narrower than the top. 



OCCIDENTAL, Lat. occidens, setting. Ap- 

 plied to precious stones of inferior hard- 

 ness and beauty. 



OCCIP'ITAL. .Belonging to the occipi;r 

 r hind part of the head, as the occipital 

 bone, which forms the posterior and infe- 

 rior part of the skull. 



OC'OIPUT. In anatomy, the hind part 

 of the head ; the protuberance imme- 

 diately above the neck. 



OCCULT', Lat. occultus, invisible, secret, 

 undiscoverable. An occult line in a 

 draught is a dry line not intended to be 

 seen when the plan is finished. The occult 

 nces are the imaginary sciences of the 

 middle ages, such as alchemy and astro- 

 logy. 



OCCULTA'TION, from occult. An astrono- 

 mical term, applied to the time that a 

 star is hid from our sight by the interpo- 

 sition of any other heavenly body, as the 

 moon, between it and the eye of the ob- 

 server. 



OC'CCPANCY, 1 from ob and capio, to 



OC'CUPANT, > seize. In law, the taking 



OCCUPA'TION, ) possession of things 

 which do not belong to any body is termed 

 occupancy, and is the foundation of pro- 

 perty. He who takes possession is termed 

 the occupant, and holds it by right of oc- 

 cupancy. Property so possessed is said to 

 be in the occupation of A. B. 2. Occu- 

 pation is also used in the sense of calling 

 or trade. Thus agriculture, manufactures, 

 and commerce, furnish the most general 

 occupations of life. 



O'CEAN, Lat. oceanvs, Gr. $. A 

 name which seems to have for its origin 

 greatness or extent, used to designate the 

 great mass of salt water which covers 

 more than three-fifths of the surface of 

 the globe, and which for convenience is 

 usually spoken of as if divided into three 

 portions: the Atlantic ocean, which divides 

 Europe and Africa from America, the 

 Pacific ocean, or South Sea, which divides 

 America from Asia, and the Iiulian Ocean, 

 which separates the East Indies from 

 Africa. These, however, are only parts 

 of the vast whole. 



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