458 OOLITE 



The oil of roses, called the attar or otto, is extracted from the petals of the Rosa 

 cenfifolia and H. scmpirvircns. 



The oil of rosemary is extracted from the Bosmarinus officinalis. 



The oil of saffron is extracted from the stigmata of the Crocus sativus. It is narcotic. 



Thr. oil of sassafras is extracted from the woody root of the Launis sassafras. 



Oil of savine is extracted from the leaves of the Juniperus sabina. 



Oil of thyme is obtained from the Thymus vulgaris. 



Oil of wormwood is distilled from the Artemisia absinthium. 



OH of turpentine. See TURPENTINE. 



OIL-STONE. A peculiar slate-stone found in Turkey and elsewhere, which 

 forms a better whetstone than any other substance. The finest are found in the 

 interior of Asia Minor, and being imported, arc known as Turkey hones or oil-stones. 



OLD 23, ED SANDSTONE. A geological formation so called ; named by Sedg- 

 wick and Murchison, Devonian, as portions of the system are peculiarly developed in 

 Devonshire. See SANDSTONE. 



OLEATES are saline compounds of oleic acid with the bases. 



OLEriANT GAS is the name originally given to bi-carburetted hydrogen. See 

 CAUSE RETTED HYDROGEN. 



OLEIC ACID. A neutral oil, obtained by saponifying mutton-fat with potash, 

 and decomposing the soap with sulphuric acid. The fat acids are dissolved in hot 

 alcohol; the solution on cooliug is expressed, and the operation frequently repeated. 

 Oleic acid is insoluble in water, but soluble in alcohol and ether. Its formula appears 

 to be C 86 H S8 3 ,HO (C 18 H 3 0-). 



OLEIKTE, or Lipylc. Obtained by boiling tallow in alcohol. It is regarded as an 

 oleate of oxide of glyceryle. It constitutes the more fluid portion of oils. 



OLEOGRAPH. The name given to a picture printed in oils. It is prepared by 

 a process of block -printing. 



OLIBANU1VI is a gum-resin, used only as incense in Roman Catholic churches. 



OLIVE oil,. See OILS. 



ONICOLO, or NICOLO. A variety of onyx having a ground of deep brown, in 

 which is a band of bluish-white. It is used for cameos, and differs from the ordinary 

 onyx in a certain blending of the two colours. H. W. B. 



ONYX. A mineral belonging to the chalcedonic variety of quartz. It resembles 

 agate, excepting that the colours are arranged in flat horizontal planes. When the 

 layers consist of sard and white chalcedony, the stone is called sardonyx. 



These stones were formerly more prized than they are at present, and were fre- 

 quently cut in cameo and intaglio. 



OOLITE. (Oolith, Ger. From u6v, an egg, and \L6os, a stone.) A geological 

 term. Those varieties of limestone which are composed of an aggregation of small 

 spherical concretions resembling in appearance the roe of a fish, and bound together 

 by a calcareous cement. When first quarried they are generally soft, but harden by 

 exposure to the air and the evaporation of the water. 



The particles are generally formed of concentric layers of carbonate of lime arranged 

 round a grain of sand, a fragment of shell, or some organic substance, forming the 

 nucleus around which the calcareous matter has been deposited. 



The name Roestone, from the fanciful resemblance of these oolitic concretions to 

 the roe of a fish, has likewise been given to this kind of limestone when the grains 

 are of small sizes ; when of comparatively large dimensions, as in some beds of 

 Inferior Oolite in the neighbourhood of Cheltenham, they are distinguished by the 

 name of Pcastonc or Pisolite (from irfow, a pea, and \i6os, stone). 



In geological nomenclature, the term Oolite has a more extended signification, and 

 is applied indiscriminately to the entire accumulation of strata consisting of limestones, 

 marls, clays, and sands, intervening between the Trias or New Red and the Wealden 

 formations, in consequence of the limestones of those deposits frequently possessing 

 an oolitic structure. Of these, Portland stone, Coral Rag. Bath or Great Oolite, and 

 Inferior Oolite are the most important in an economical point of view, owing to their 

 furnishing fine descriptions of freestone, suitable for building and ornamental purposes, 

 both from their tints, which are either white or cream coloured, and the large blocks 

 in which they can be obtained. 



The well-known white freestone obtained from Caen in Normandy is an Oolitic 

 limestone belonging to the Bath or Great Oolite formation. 



Although the oolite formations constitute the chief repositories of limestones 

 possessing an oolitic structure, they aro not confined to those groups of strata, but are 

 met with in other formations, as for instance in some beds of carboniferous or 

 mountain limestone in the neighbourhood of Bristol, us well as very largely in that 

 of Ireland. H. W. B. 



