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depth to average ten miles ; others rate 

 it at five miles. The present cannot be 

 considered as having always been the bed 

 of the ocean ; on the contrary, what are 

 now the most elevated portions of the 

 earth's crust were once submerged, and 

 over them the ocean for ages rolled its 

 majestic waves. This is not an invention 

 of modern geologists, Ovid declares the 

 same : 



Vidi factas ex sequore terras ; 

 Et procul a pelago conchse j acuere marinee ; 

 Et vetus inventa est in montibus anchora summis; 

 Quodque fuit campus, vallem decursus aquarum 

 Fecit ; et eluvie mons est deductus in sequor : 

 Eque paludosa siccis humus aret arenis ; 

 Quaeque sitim tulerant, stagnata paludibus hument. 

 Metamorph. lib. xv. 



OCEA'NIC. Pertaining to the ocean ; in- 

 habiting the ocean. 



OCEA'NIC DE'LTA. A delta formed at the 

 mouth of rivers where they enter the 

 ocean, as distinguished from either lacus- 

 trine or mediterranean deltas. Mr. Lyell 

 observes, " whenever the volume of fresh 

 water is so great as to counteract and 

 almost neutralize the force of tides and 

 currents, and in all cases where these 

 agents have not sufficient power to remove 

 to a distance the whole of the sediment 

 periodically brought down by rivers, 

 oceanic deltas are produced. 



O'CELLATED. (ocellatus, Lat.) In con- 

 chology, applied to shells, when marked 

 with little eye-like spots. 



O'CHRE. (uxpa> Gr. ochra, Lat. ocre, Fr.) 

 Red iron ore ; it yields good malleable 

 iron. Colours red, yellow, and brown. 

 It occurs in dull earthy masses, nearly or 

 quite friable, which soil the fingers. Its 

 constituents are oxide of iron 83'0, silex 

 5-0, water 12 0. 



O'CHREOUS. Containing ochre ; resembling 

 ochre. 



OcxAe'DRAL. ^ Having eight sides all 



OCTAHE'DRAL. $ equal. 



OCTAC'DRITE. Octaedral oxide of titanium ; 

 the Titane anatase of Brongniart ; Octae- 

 drit of Werner ; Octaedrite of Jameson ; 

 the Oisanite of Lameth. A pure oxide of 

 titanium, crystallized in acute, elongated 

 octacdrons, consisting of two pyramids, 

 whose faces are isosceles triangles, and 

 whose bases are squares. Colours blue, 

 blackish- blue, and brown. Lustre splen- 

 dent and adamantine. Fracture foliated ; 

 easily broken. It scratches glass. Spe- 

 cific gravity 3'8. Before the blow-pipe it 

 is infusible by itself, but with borax it 

 fuses into a glass. It occurs in veins in 

 Dauphiny, Norway, Spain, and Brazil. 



OCTAC'DRON. ) (oKTaidpog, from OKTCJ, 



OCTAHE'DRON. $ eight, and tdpa, a side, 

 Gr. octaedre, Fr.) The solid angles of 

 an octaedron are formed by four equal 



and equilateral plane triangles ; conse- 

 quently it is formed by two equal spare 

 pyramids joined together at their bases, 

 the sides whereof are equilateral triangles. 

 The octahedron (unlike some forms which 

 are not susceptible of variation, as the die 

 or cube, a solid invariably bounded by six 

 square surfaces or planes) is susceptible 

 of variation ; it is sometimes flat and low, 

 and, at others, acute and high. 



Ocxoe'jDRiTE. See Octaedrite. 



O'CTOPUS. (from oicrtu, eight, and TTOVC, a 

 foot, Gr.) A genus of sepise. The octo- 

 pus was the animal denominated polypus 

 by Aristotle. It has eight arms, all of 

 equal length, and contains in its interior 

 two very small rudimental shells, formed 

 by the inner surface of the mantle. This 

 shell becomes much more distinct in the 

 loligo. Roget. 



O'CTODENTATE. (from octo, eight, and 

 dentatus, toothed, Lat.) Having eight 

 teeth, and no more. 



O'CTOFID. (from octo, eight, andfindo, to 

 cleave, Lat.) Eight-cleft. In botany, 

 an epithet for a calyx divided into eight 

 segments. 



OCTOLO'CULAR. (from octo, eight, and 

 loculus, a cell or pocket, Lat.) Eight- 

 celled. 



OCTONO'CULAR. (from octo, eight, and 

 oculus, an eye, Lat.) Having eight 

 eyes. 



OCTOPE'TALOUS. (from o/crw, eight, and 

 irtToXbv, a petal, Gr.) Having eight 

 petals or flower-leaves. 



OCTO%PE'RMOUS. (from OKT-W, eight, and 

 (TTrgpjua, seed, Gr.) Eight-seeded; hav- 

 ing^ eight seeds. 



O'CULATE. (oculatus, Lat.) Having 

 eyes. 



O'CULIFORM. (from ocvJus, an eye, and 

 forma, shape, Lat.) Resembling an eye 

 in its form ; eye- shaped. 



ODORI'FEROUS. (from odor, scent, and 

 fero, to give, Lat. odoriferant, Fr. odori- 

 fico, It.) Yielding scent ; giving out 

 perfume. Generally, but not always, used 

 to denote sweet scent. 



O'DOROUS. (odorant, Fr. odorifero, It.) 

 Fragrant ; sweet of scent. 



(ESO'PHAGUS. (asophage, Fr.) The gul- 

 let, or passage leading from the mouth to 

 the stomach, through which the food 

 passes. In the structure of the oesopha- 

 gus, we may trace an adaptation to the 

 particular kind of food taken in by the 

 animal. When it is swallowed entire, or 

 but little changed, the oesophagus is a 

 very wide canal, capable of being greatly 

 dilated. Serpents, which swallow animals 

 of greater circumference than themselves, 

 have an oesophagus admitting of great di- 

 latation ; the food in such cases remaining 

 a long time in the canal, before it reaches 



