OG Y 



516 



OLE 



OFFIC'INAL, Lat. officinalis. Relating 

 to a shop (officind) as officinal medicines, 

 which are directed by the colleges of 

 physicians to be kept in the shops. 



OFFICI'NA SCCLPT'ORIS. The Sculptor's 

 Shop. A small constellation on the S. of 

 Cetus. It contains 12 stars, none of 

 which exceeds the fifth magnitude. 



OF'FIXG. In nautical language, that 

 part of the sea which is at a considerable 

 distance from the shore, where there is 

 deep water, and no need of a pilot to con- 

 duct the ship. 



OFF'SET. 1. A shoot or sprout from 



the roots of a plant. 2. In surveying, 



a perpendicular measured on the side of 

 an irregular figure : thus ad', bb', &c. are 



offsets drawn perpendicular to the base 

 line AB. These offsets are usually mea- 

 sured With an offset-staff, made of light 

 wood, ten links in length. 3. In ac- 

 counts, a sum set-off against another sum 

 or account as an equivalent.^ 4. In 

 building, when the face of a wall is not 

 one entire or continued surface, but is 

 formed by two or more continued sur- 

 faces, each rising from the horizontal 

 base which forms the top part of the wall 

 below; the line thus connecting the 

 two surfaces is called an offset; the 

 term however having reference only to 

 the superior part of the wall, or that 

 part above the offset-line. 



OGEE'. In architecture, a moulding the 

 same as the cyma reversa, or cymatium of 



the ancients. It consists of two members, 

 the one concave, and the other convex, 

 somewhat like S. 



O'oHiM, i A peculiar kind of steno- 



O'OUM. ) graphy, found on ancient 

 Irish monuments. 



O'GIVE, (pron. tyire). An arch, or a 

 branch of a Gothic vault, which, instead 

 of being circular, passes diagonally from 

 one angle to another, forming a cross 

 with the other arches. The centre where 

 the ogives cross is termed the key ; their 

 members or mouldings are called nerves, 

 reins, and branches, and the arches which 

 separate them, double arches. The key is 

 usually cut in form of a rose, or cut de 

 lamp. 



OGY'OIAN. Relating to Ogyges, one of 

 the most celebrated of the ancient rnon- 



rchs of Greece, and during w):>:- 

 a deluge happened which so inundated 

 the territories of Attica, that they re- 

 mained waste for nearly 200 years. This 

 is generally supposed to have occurred 

 1704 years before the Christian era, and 

 is spoken of as the Ogygian Deluge. 



OIL, Sax. eel, from (elan, to kindle. A 

 proper juice of a fat or unctuous nature, 

 either solid or fluid, indissoluble in water, 

 combustible with flame, and volatile in 

 so very different degrees as to give rise 

 to the denominations of volatile and fixed 

 oils. The volatile oils, called also essential 

 oils, are often almost as liquid as water 

 sometimes viscid, very combustible, hav 

 an acrid taste, and a strong fragran* 

 odour, are soluble in alcohol, and imper- 

 fectly in water, evaporate at a tempera- 

 ture not higher than 212, and leave no 

 stain on paper. These oils are almost all 

 obtained from vegetables, and they exist 

 in every part of plants, the root, the 

 bark, the wood, the leaves, the flower, 

 and even the fruit, but never in the sub- 

 stance of the cotyledons. The fixed oils, 

 called also fat oils, are liquid, or easily 

 become so, when exposed to a gentle 

 heat; have an unctuous feel, and a mild 

 taste ; are very combustible, and insolu- 

 ble in water, and very slightly so in 

 alcohol. Their boiling point is never 

 under 600 P., and they leave a greasy 

 stain on paper. These oils are numerous ; 

 some of them are obtained from animals, 

 and others from vegetables, by simple 

 expression. 



OIL-GAS. An illuminating gas, obtained 

 by decomposition of a fat oil ^usually 

 train oil), much in the same way that 

 coal gas is manufactured. It is somewhat 

 richer than the common coal gas. 



OIL OF BRICKS. The product of distil- 

 lation of a brick soaked in oil. 



OIL OF VITRIOL. Sulphuric acid. 



OL'BERS. A name sometimes given to 

 the planet Pallas, because discovered by 

 Dr. Olbers in 1802. 



OLDENLAN'DIA. A genus of plants of 

 two species : PentandriaJJigynia. Named 

 in honour of Oldenland, a Danish bota- 

 nist. The root of one species, the O. 

 umbellata, which grows wild on the coast 

 of Coromandel, affords the beautiful red 

 dye so muuh admired in the Madras 

 cottons. 



OLD'ER-PLIOCENE. See PLIOCENE. 



OLD RED SANBSTONE. The lowest mem- 

 ber of the carboniferous group of strata. 

 It consists of many varieties of siliceous 

 sandstones, and conglomerates of various 

 colours, but red predominates. 



O'LEA. The Olive-tree. A genus of nine 

 species: Diandria Monogynia. Name 

 from thauct, oil, because the earliest and 

 best known species, the O. europeea, i 

 that which affords the olive-oil. It u a 



