OCE 



line. Oblique sailing, in navigation, is 

 that which includes the calculation of 

 oblique-angled triangles. Oblique sphere, 

 in geography, is that in which the axis of 

 the earth is inclined to the horizon of 

 the place. 



OBLONG {oblongus, of a figure inclin- 

 ing to long). A four-sided figure, which, 

 like the square, has all its angles right 

 angles, but, unlike the square, has not all 

 its sides equal. The term rectangle is often 

 used for it, but is obviously objectionable. 

 An oblong spheroid, also called the pro- 

 late spheroid, is generated by the revo- 

 lution of an ellipse about its longer axis, 

 and is therefore elongated at the poles. 



OBSI'DIAN. A volcanic product, or 

 species of lava, very like common green 

 bottle-glass, which is almost black in 

 large masses, but semi-transparent in 

 thin masses. Pumice-stone is obsidian 

 in a frothy state, produced, most pro- 

 bably, by water which had been contained 

 in, or had access to, the melted stone, 

 and converted into steam. Solid obsi- 

 dian often occurs in masses, which are 

 partially converted into pumice. The 

 name is derived from that of Obsidius, 

 who first found it in Ethiopia. 



OBSOLETE {obsoletusy grown out 

 of use). A term denoting a faint indi- 

 cation of a character. Thus, the calyx 

 of Conium is represented by an obsolete 

 margin ; slight and indistinct striae upon 

 a shell are termed obsolete striae. In 

 these cases, however, the obsolete state 

 is not the result of accident, but of par- 

 tial development. 



OBTUSE. Blunt or dull ; opposed to 

 acute, as applied to an angle which is 

 greater than one right angle and less than 

 two ; in other words, an angle which 

 measures more than 90 and less than 

 180 degrees. 



O'BVOLUTE {obvolutus, rolled over). 

 A form of aestivation or vernation, in 

 which the margins of one leaf alternately 

 overlap those of the leaf which is oppo- 

 site to it. 



OCCULT SCIENCES. Hidden sci- 

 ences; imaginary sciences, as alchemy, 

 astrology, magic, &c. 



OCCULTA'TION (occulto, to hide). 

 In astronomy, the eclipsing of a fixed 

 star by this interposition of the moon. 



OCEAN. The one continuous fluid 

 which spreads over nearly seven-tenths 

 of the globe, all the gulfs and inland seas 

 being branches of this universal ocean. 

 Different names have, however, been 

 given to various parts of it : — 

 239 



OCT 



I. South-Eastern Basin. 



1. Antarctic Ocean. Comprised within 

 the Antarctic circle ; that is, betwern the 

 parallel of 66° 32' of southern latitude 

 and the South Pole. 



2. Southern Ocean. Bounded on the 

 one side by the Antarctic circle, and on 

 the other by a line drawn from Cape 

 Horn to the Cape of Good Hope, thence 

 to Van Diemen's Land, and again by the 

 south of New Zealand to Cape Horn. 



3. Indian Ocean. Lying between Africa 

 on the west, and the peninsula of Malaya 

 with the islands of Sumatra, Java, &c., 

 and New Holland, on the east, and 

 bounded by Per.sia and Hindostan on the 

 north. The Red Sea or Arabian Gulf, 

 the Persian Gulf, and the Bay of Bengal, 

 are all parts of this ocean. 



4. Pacific Ocean. Divided by the equa- 

 tor into North and South, and inclosed 

 between America on the east, and New 

 Holland, the islands of Java and Su- 

 matra, and the continent of Asia, on the 

 west. On the north it terminates at 

 Behring's Straits. The seas of China, 

 Japan, Okhotsk, &c., form parts of this 

 ocean. 



II. Western Basin. 



1. Atlantic Ocean. Commencing in 

 the south from a line drawn from Cape 

 Horn to the Cape of Good Hope, and ter- 

 minated on the north by the Arctic circle. 

 It is divided into the North and South by 

 the equator, and its branches are the 

 Mediterranean, the North Sea or German 

 Ocean, the Baltic, Baffin's Bay, Hudson's 

 Bay, the Gulf of Mexico, and the Carib- 

 bean Sea. 



2. Arctic Ocean. Surrounding the 

 North Pole, and bounded by the Arctic 

 circle and the northern shores of the two 

 continents. The White Sea, the Sea of 

 Kara, and the Gulf of Obe, are parts of 

 it. 



O'CHRE. Hydrated sesquioxide of 

 iron ; an argillaceous earth, impregnated 

 with iron of a red or yellow colour. 



O'CHREA. Literally, a boot; and 

 hence applied, in botany, to the mem- 

 branous tube which sheaths the stem of 

 rhubarb and other plants, and consists of 

 two stipules, cohering by their margins. 



O'CTAGON (oKTw, eight, '^avia, an 

 angle). A plane geometrical figure, con- 

 tained by eight sides, and consequently 

 having eight angles. When the sides 

 and angles are equal, the figure is a 

 regular octairon. 



OCTAHE'DRITE (okto*, eight, edpa, 

 a seat). Anatase. Pyramidal titanium 



