O G Y 



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OMB 



the stomach. Grazing animals, who 

 carry their heads close to the ground 

 while feeding, have the oesophagus 

 strengthened by thick muscular coats, 

 whereby the food is propelled towards 

 the stomach, the direction being contrary 

 to that of gravity. 



OGY'GIAN. (from Ogyges, a celebrated 

 monarch, the most ancient of those that 

 reigned in Greece.) His origin, the age 

 in which he lived, and the duration of his 

 reign are so obscure and unknown, that 

 the epithet of Ogygian is often applied to 

 every thing of dark antiquity. 

 OGY'GIAN DE'LUGE. The name given to a 

 deluge which happened in the reign of 

 Ogyges, which so inundated the territories 

 of Attica, that they remained waste for 

 nearly 200 years. This is supposed to 

 have happened about 1764 years before 

 the Christian sera. 



OGY'GES. The name given by Guettard to 



a species of trilobite, from its being found 



among the most ancient rock formations, 



containing vestiges of organic life. 



OI'SANITE. The name given by Lameth to 



pyramidal titanium or anatase. 

 OLD RED SANDSTONE. The lowest member 

 of the carboniferous group, extensively 

 developed in the counties of Shropshire 

 and Herefordshire, in England ; Breck- 

 nockshire, in Wales ; and Dumfriesshire 

 and Forfarshire, in Scotland. The old 

 red sandstone strata lie between the car- 

 boniferous series and the silurian rocks. 

 It consists of many varieties and alter- 

 nations of silicious sandstones and conglo- 

 merates of various colours, red predomi- 

 nating. Mr. Bakewell says, " the old 

 red sandstone, about which so much has 

 been written, and so little understood, is 

 a greywacke, coloured red by the acci- 

 dental admixture of oxide of iron. It 

 possesses all the mineral characters of 

 greywacke, except the colour, which is a 

 quality that never can be considered of 

 importance, being chiefly derived from 

 local or accidental causes. The old red 

 sandstone also occupies the geological 

 position of greywacke, and greywacke 

 slate, into which it passes merely by a 

 change of colour. Until English geolo- 

 gists shall renounce their prejudices, and 

 place the old red sandstone and mountain 

 limestone in the transition class, as grey- 

 wacke, and transition limestone, every 

 attempt will be vain to identify this part 

 of the geology of England with that ol 

 the continent." 

 OLDER PLIOCENE. Mr. Lyeli has sub-di- 

 vided the tertiary epoch into four periods ; 

 namely, the newer pliocene, the older 

 pliocene, the miocene, and the eocene. 

 The term pliocene he derived from the 

 two Greek words TrXawv, more, anc 



Kaii'oc, recent. The older pliocene for* 

 mations lie between the miocene and the 

 newer pliocene. Of fossil shells examined 

 by M. Deshayes, the older pliocene con- 

 tained from thirty-five to fifty per cent, of 

 recent fossils. 

 ^LEA'GINOUS. (oleaginus, Lat. oleagi- 



neux, Fr. olioso, It.) Oily ; unctuous. 

 DLE'CRANON. (oXeKoavov, Gr. from ojXevri, 4 

 the ulna, and icdprjvov, the head.) A 

 process of one of the bones of the fore 

 arm, the ulna, forming part of the elbow- 

 joint. 



DLFA'CTORY. (from olfacio, to smell, to 

 give a scent to, Lat. olfactoire, Fr. ol- 

 fattore, It. ) Having the sense of smell- 

 ing ; pertaining to smelling : as the ol- 

 factory nerves, &c. 



D'LIVA. (oliva, an olive, Lat.) So named 

 from the oblong and elliptical shape of the 

 shell. A marine subcylindrical univalve ; 

 aperture narrow, long, and emarginated 

 opposite to the spire, which is short ; the 

 plicae of the columella are numerous, and 

 resemble striae ; whorls sulciform. Mr. 

 Gray has ascertained that , in the olivee, 

 shell is deposited, and most probably 

 secreted, by the upper surface of the foot, 

 which is very large, and not by the 

 mantle, which is small, and does not ex- 

 tend beyond the edge of the mouth. The 

 shells of this genus are very beautiful, 

 and display a great variety of rich mark- 

 ings and splendid colours. Recent olivae 

 are found at depths varying to twelve 

 fathoms, in mud, sandy mud, coarse 

 sand, &c. They are also caught by 

 fishing lines. Fossil olivse are found in 

 the calcaire grossier, and London clay. 

 Several species have beefr described. 

 OLIVA'CEOUS. Of an oiive colour, a green 



with an admixture of brown. 

 OLI'VENITE. An ore of copper of an olive- 

 green colour. It consists of oxide of 

 copper 63 P 0, phosphoric acid 28'6, water 

 8 '4. Occurs with quartz in micaceous 

 clay-slate, in drusy cavities. 

 O'LIVINE. The prismatischer chrysolithe 

 of Mohs ; peridot of Hau'y ; olivin of 

 Werner. A mineral, generally of an 

 olive-green colour, from which circum- 

 stance it obtains its name : it is sometimes 

 of an asparagus green, or yellowish green. 

 Occurs in distinct granular concretions, 

 or in rounded masses. Structure foliated. 

 Fracture imperfectly conchoidal. Lustre 

 shining, translucent, and, sometimes, 

 transparent. Its constituents are, silex 

 50'0, magnesia 37'5, oxide of iron 12*0, 

 lime 0*5. It is found in basalt, and is a 

 constituent of many lavas. 

 O'MBRIA. (from ofjflpiog, rain, Gr.) Fos- 

 sil echini, to which the name of ombria 

 has been given, from a supposition that 

 they fell from heaven in the midst of 



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