OID'IPOUS, the “swollen-foot" (Lat. Edipus), is the name of one of the most famous personages of the Greek heroic mythology. It was given to him because his father Laios, son of Labdakos, king of Thebes, having been informed by an oracle that his new-born babe would be the cause of his death, pierced the feet of the infant, tied them together with a rope, and ordered the little one to be thrown upon the side of the mountain, there to perish of exposure. But the poor babe with its swollen feet was found by a shepherd, who took it to the King of Corinth, by whom Oidipous was brought up as his own child. To penetrate the mystery of his birth the prince made a journey to Delphi and consulted the oracle. To his horror he was told that his destiny was to slay his father and commit incest with his mother. Thinking that the good King of Corinth was referred to by the oracle, Oidipous at once resolved never to see him more. Wandering homeless away from Delphi he met Laios, who angrily disputed the way with him, and in the ensuing scuffle Laios and his charioteer were slain. Oidipous reached Thebes not knowing the name of the man he had killed. The city was in great trouble both for the prolonged absence of its king and the ravages of the Sphinx, a female Centaur-like monster, a compound of giantess and lioness, who daily came to a rock near Thebes and put enigmas to the passers by, slaying and devouring those who failed to guess the answer. The Thebans at length declared that he who should deliver them from the Sphinx should marry the Queen Iokasta, now deemed on all hands to be a widow, and become king of Thebes. This was accomplished by Oidipous, who received as his riddle from the Sphinx the famous description of "A being with four feet, two feet, and three feet, but only one voice, weakest when it has most feet." The answer was correctly given, as Man, who crawls at first on all fours, then walks erect, and finally is obliged to use a staff in old age," and on hearing it the Sphinx threw herself in rage from the rock and was killed. Children were born to Oidipous and his mother-wife, two sons, Etêoklês and Poluneikês, and two daughters, Antigonê and Ismênê. Disasters which overtook the country caused Oidipous to consult the prophet Teiresias, and thus at last learn the awful sins at bis charge. Frantic with despair he put out his eyes as unworthy to behold longer the light of heaven, and at cace quitted Thebes. Iokasta strangled herself. Kreôn, brother of Iokasta, who had acted as regent during Laios' absence of old, now assumed the regency for the sons of Oxipous, and warned by an oracle he brought back and detained the unhappy king in the land. But when the sons were grown up, they and Kreôn thrust out Oidipous, who, attended by his loving daughter Antigonê, the favourite bercine of Greek tragedy, wandered over Greece begging Lis bread. Meanwhile the sons quarrelled, and Etêoklês drove out Poluneikês from Thebes. The latter prepared a great army with the help of six princes (the famous "Seven against Thebes"), and hearing from an oracle that the side which Oidipous should favour would win, he sought out his aged father, whom he found at Kolonos, Dear Athens, having just received a cordial welcome and promise of relief from all future misery at the hands of the generous Theseus. Hardly had the indignant father driven away his unworthy son than Kreôn, moved by the same oracle, arrived with soldiers, seized the blind old man and his daughter, and proceeded to drag them away to Thebes. Theseus arrived in time to prevent this last injury. For all the benefits of the great Athenian prince Oidipous gave ample return. Theseus accompanied him into a grove and there alone saw him die, receiving from him promises of eternal protection for Athens so long as his grave was kept secret and preserved from dishonour. As for his sons, the dying king solemnly cursed them, and foretold their death by each other's hand. ANTIGONE.

See

OID'IUM (Gr. oideo, to swell), the vine mildew, a destructive disease to which grapes of late years have been subject, and which is now known to originate in the attack of a kind of fungus, called Oidium Tuckeri. Oidium is now found to be only a stage in the growth of a species of Erysiphe. The specific name is derived from Tucker, the name of a gardener at Margate who first used sulphur as a remedy for the disease.

OIL BEETLE. See MELOIDE.
OIL BIRD. See GUACHaro.

OIL GAS, a gas introduced some years ago, and then made on the large scale; it was compressed into iron cylinders, and sold as "portable gas." It was made by dropping a fatty oil into a red-hot iron retort, and collecting the gas; it has a high illuminating power. This manufacture has long ceased, but the same process has recently been adopted with crude petroleum; it gives a richly luminous gas, very pure, and quite free from sulphur.

OIL OF VITRIOL. See SULPHURIC ACID. OIL-CAKE, the crushed residue remaining after the oil has been pressed out from certain seeds. As this cake always retains a large percentage of the oil, together with nearly all the albuminous matter, sugar, gum, and the starchy components of the seeds, it possesses a high nutritive value, and forms a valuable food for cattle and sheep. The richest and best of the cakes used in this way are those obtained from ordinary linseed, next to which in value come rape, cotton, and palm cakes. Other kinds are hempseed, poppy-seed, gold-of-pleasure seed, &c., but these are of lesser importance. The cotton-seed cake, when the husks of the seed have been removed before crushing, forms a very valuable food stuff, and immense quantities are imported into Great Britain from the United States. OIL-PALM. See ELEIS.

OILS. The term oil is used to designate numerous liquid or semi-liquid substances obtained by a variety of methods from very different sources. In its most comprehensive sense it includes solid and even hard substances, such as fat, tallow, and wax, the thick fluid fixed oils, the odorous essential oils, and the volatile oils or hydrocarbons obtained chiefly by the destructive distillation of mineral substances. For an account of oils of the latter class see under Hydrocarbon Oils below.

Fixed oils, from which the fats are only distinguished by being solid at ordinary temperatures, chemically considered, are compounds of glycerin with certain fatty acids, the more important of which are known as oleic, palmitic, stearic, linoleic, and physetoleic acids. There are numerous other fatty acids found, in combination with glycerin, in oils, but with those mentioned they are all compounds of carbon, hydrogen, and oxygen; some of them, like oleic acid, are fluid at ordinary temperatures, while others, such as stearic acid, form solid crystalline bodies.

In a pure condition most oils have scarcely any characteristic colour, taste, or smell, and, with few exceptions, they possess no active physiological properties. Among their physical properties the more prominent are their viscosity, insolubility in water, and their being lighter than that fluid. The viscosity of some of the fluid oils is very considerable, that of castor oil, which at a temperature of 15° C. flows more than two hundred times more slowly than water, being perhaps the most extreme instance. Olive oil at the same temperature flows about twenty times as slowly as water. Oils give to paper, which they render translucent, a permanent stain; they are not volatile at the ordinary temperature of the atmosphere, or indeed at any temperature insufficient for their decomposition, and nearly all of them, when exposed to the air, absorb oxygen readily, and either gradually harden or become rancid and nauseous. The whole of the fixed oils, when heated to their boiling-points, 500° to 600° Fahr., suffer decomposition, yielding various hydrocarbons, and when

suddenly exposed to a red heat they furnish a gaseous product, which is capable of being used for illuminating purposes. With the caustic alkalies and water they unite to form soap. Their property of absorbing oxygen is sometimes a source of danger, for when they are absorbed by porous bodies by which an extensive surface is exposed to the air, they are apt to generate sufficient heat to produce spontaneous combustion. Tow, cotton-waste, wool, &c., impregnated with oil and left in a heap freely exposed to the air or sun often burst into a flame, and in this way many

extensive fires have arisen. Linseed, rape, and olive oil are especially liable to produce this result. The specific gravity of all oils is lower than that of water, ranging between 865 to 970, water being 1.000.

The fixed oils and fats are most widely distributed in animal and vegetable life, being chiefly found in the fruits and seeds of plants and in thin membranous cells, forming what is called adipose tissue in the bodies of animals. In the following table we give a list of the more important oils and fats ordinarily met with in commerce:

Various fish,

Feet of oxen,

Linum usitatissimum, Aleurites triloba, Camelina sativa,. Papaver somniferum, Helianthus annuus, · Madia sativa, Guizotia oleifera, Carthamus tinctorius, Cannabis sativa, . Juglans regia,

Arachis hypogaa,

.

Ricinus communis,

Croton Tiglium, •

Palm-seed Oil, Vegetable Tallow (Chinese),

In reference to the foregoing table notices of some of the more important oils are given under their own headings or under the name of the producing material. [See COCOA-NUT PALM, COD-LIVER OIL, CROTON, &c.] Whale or train oil is obtained by melting the blubber of the animal. As met with in commerce, it is of a brownish colour, rather viscid, and has a disagreeable fishy smell and taste. Its specific gravity is about 0-927. Sperm oil is obtained from an oily matter lodged in a bony cavity of the head of the Physeter macrocephalus or spermaceti whale. When this substance is subjected to pressure in bags a quantity of pure limpid oil is expressed; and the residue, after being melted, strained, and boiled with a weak solution of potash, forms the well-known animal wax, spermaceti. Seal oil is obtained from the blubber of nearly thirty varieties of seal. A full-grown seal will yield from 8 to 12 gallons of oil, a small one 4 to 5 gallons. The pale seal oil of commerce is that which drains from the blubber before putrefaction commences, and this when refined ranks close after

sperm oil. Brown seal oil is that which drains from the mass after fermentation and putrefaction have set in. It has a strong disagreeable odour, nauseous taste, and it gives off much smoke in burning. Under the name of fish oil are included all the oils obtained by boiling fish refuse or entire fish which are not used as food. Neat's-foot oil is obtained by boiling the feet of the common ox, the fat being skimmed from the surface of the water and allowed to settle, when the oil can be drained away. A large quantity is exported from the River Plate region in South America. Gold of pleasure, German sesame, or Camese oil is produced and consumed chiefly in Germany. Poppy oil is yielded by the seeds of the opium poppy, and it forms an important article of food in the valley of the Ganges, where opium is chiefly cultivated. The cold-pressed oil very sweet and pleasant, the hot-pressed oil being more suitable for manufactures. From its good drying properties it is highly esteemed by artists. Sunflower oil is clear. pale-yellow, and tasteless, and is much esteemed as food

in the east of Russia. Madia oil is obtained from the Madia satira, a plant introduced into Europe from Chili on account of its oil-yielding properties. It occupies a place intermediate between drying and non-drying oils. Niger oil is the produce of a plant largely cultivated throughout India, where it is much used by the poorer sections of the population as a substitute for ghee. When imported into Europe it is chiefly employed as a lubricant and in soap-making. Nut oil is obtained from walnuts or hickory nuts. It is pale, mild tasted, very fluid, and has strong drying properties, rendering it peculiarly suitable as a vehicle for oil colours. Groundnut oil is largely used as a substitute and adulterant of olive oil, and it forms the principal staple of the soapmaking industry of Marseilles. [See ARACHIS.] Cottonseed oil, obtained from the decorticated seeds of cultivated cotton, was first introduced in 1852, and successive improvements in its manufacture have made it one of the most important vegetable oils of commerce. It is largely employed for lubricating purposes and in soap-making, and being when fresh and well refined of a clear yellow colour and pleasant taste, it is much used to adulterate olive oil. Gingelly oil is largely consumed in China and the East ladies as food, and the best qualities are equal, if not superior, to the best olive oil. In Europe the seed is principally crushed at Marseilles and Trieste.

Of the vegetable fats one of the chief is cocoa-nut oil. It is white, has a slight pleasant smell, and a rather agreeable taste. Its specific gravity is about 0.910; it melts at 122 Fahr., and of late years it has been largely used in soap and candle making. Palm oil is of the consistence of tutter, and of an orange-yellow colour. It has an agreeable smell, and it melts at about 103° Fahr.

Volatile or Essential Oils.-These are an extensive and important class of bodies derived from the vegetable kingdom, and found in almost every part of the majority of the plants which produce them, except the cotyledons of the seeds, in which, in general, the fixed oils are exclusively stored up. Their presence confers upon flowers, leaves, fruit, seeds, roots, bark, and woods their peculiar and characteristic odours; but among these they are not equally distributed in the same individual, and are often altogether absent from some of them. To them we are indebted for our most delightful perfumes and our choicest spices and aromatics. Some of them are found to possess

valuable medicinal properties, and others are invested with the highest possible interest on account of their peculiar chemical constitution and the reactions which occur when they are brought into contact with other bodies. By exposure to the air volatile oils rapidly absorb oxygen, and become partially converted into resin. This is the cause of the deposit that usually forms in them when kept in an illcorked vessel. The solid crystalline matter which separates from them when kept inclosed is stearoptene.

Chemically considered, the essential oils may be divided into three great classes:-1. Oils composed of carbon and hydrogen only, of which oil of turpentine may be regarded as the type. The oils of bergamot, capivi, cubebs, elemi, hops, juniper, lemon, orange peel, pepper, also belong to this class. 2. Oils containing carbon, hydrogen, and oxygen, including most of those in use in medicine and perfumery. To this class belong the oils of almonds, aniseed, cassia, cedar-wood, cinnamon, cumin, lavender, jasmin, meadow-sweet, orange-flowers, penny-royal, peppermint, spearmint, rosemary, rose-petals, valerian, winter grass, &c. 3. Oils containing sulphur, characterized by their extreme pungency, intense odour, vesicating power, property of blackening silver and being decomposed by contact with most other metallic bodies. The oils of asafoetida, black mustard seed, garlic, horse-radish, and onions are of this kind.

Under the term of "mixed oils" are commonly included various mixtures of oils and other substances that possess an unctuous appearance. They are generally prepared by agitating the ingredients together, and after a sufficient time decanting the clear portion, which in some cases is then filtered. Some of them are highly esteemed as remedies, and the use of others is confined to veterinary medicine.

In some instances the volatile oils are obtained by pressure, without the application of heat: this is the case with the oils of lemons, oranges, and bergamot. In general, however, they are procurable only by distillation, and this is effected by putting the herb or bark into a still with water, when the oil and water are volatilized and condensed together.

The importance of the oil trade of the United Kingdom is indicated by the following statistics, showing the quantities and values of the oils and oil seeds imported during the years 1883–85::

Large quantities, both of oil and seed, are also produced in the United Kingdom for home consumption and export. Of these, together with the other oils reshipped to foreign evantries, the quantity in 1885 was over 20,000,000 gallons, of the value of £2,400,000.

Hydrocarbon Oils.-These oils differ from the animal and vegetable oils previously described, in that they are ecmposed of hydrogen and carbon only, and are in consequence not capable of true saponification in contact with the alkalies. They are for the most part obtained by the destructive distillation of organic matter, recent or fossil, though not a few exist preformed in the vegetable kingdom. In consistence they vary greatly. Some, such

1,805,535 3,832,242 769,813 1,503,569

Compiègne. The temperature is pretty equal all over the district; the climate is healthy, but rather damp; the winters are generally long and rainy; snow sometimes lies for a month in the north of the department.

Products and Animals.-Agriculture is in a very advanced state, and grain is extensively cultivated. The principal products are wheat and oats-with which the greatest breadth of land is sown-rye, barley, potatoes, &c. Other objects of culture are hemp, flax, chicory, onions, artichokes, turnips, carrots, and a vast quantity of various pot-herbs for the supply of the Paris markets. Rape and other oleaginous plants are grown. Some maize and beet-root are produced in the arrondissement of Senlis. The vine is cultivated in several districts of the south and east; but in general the summer heat has too little intensity and is of too short duration to give the proper degree of ripeness to the grape, so that the wine of the department is of inferior quality. Apples and prodigious quantities of black and red cherries are grown. The apple-trees are placted in rows along all the highways, and in the fields they are often set in quincunx order. Cider and beer are the common beverages of the country people.

The horses and horned cattle are of middling size. A great number of calves and fat cattle are supplied to the Paris markets; in the hilly country west of the valley of the Therain cattle-feeding is the common occupation of the people, and large quantities of cheese and butter are made. The ordinary breed of sheep is not good; but in some districts a cross with Spanish merinoes has produced an improved stock, with a good carcase and a heavy fine fleece. Poultry is abundant. The usual wild animals and game are common; the wolf, fox, and wild cat are seen but rarely. The wild swan, the crane, and the stork are among the birds of passage. The black eagle, a rare bird, inhabits the forests of Compiègne.

Industrial Resources.-The manufactures of the department are various; the principal being broadcloth, tapestry, carpets, blankets, and other woollen textures, for which Beauvais has been long famous. Linen, printed cottons, duck, lace, small wares, mirrors, carpets, spectacle glasses, toys, fancy cabinet-work and turnery, porcelain, pottery, beet-root sugar, paper, beer, ropes, tiles, bricks, leather, &c. are among the other industrial products. The various agricultural and industrial products of the department find ready outlets by the Oise, the Ourcq, and the canals connected with them. Iron is found in some places, but no mines are worked; building stone, mill-stone grit, paving granite, chalk, marl, potter's and porcelain earths, turf, and fossil marble are found. The department is divided into the four arrondissements of Beauvais, Clermont, Compiègne, and Senlis.

O'KA is the name of an important river of Central Russia, which rises 40 miles south-west of OREL, and joins the Volga on the right, after a course of about 800 miles. Its basin is estimated to comprise 127,000 square miles of the richest part of the Russian dominions. Though rapid, it is navigable for almost its whole course; and at Tula it is connected with the Don by a canal.

OKEAN'OS (Lat. Oceanus), the god of Ocean in the Greek mythology. Ocean, however, bore a quite different sense among the ancients to that which we give it. With them it was the mighty river which surrounded the vast disc of the world, the land lying in the midst of this great flood. From beyond Ocean to the east the sun-chariot was driven over above the great world-disc during the day, descending beyond Ocean to the west in the evening, and returning beneath the world during the night. As the oldest Greeks knew but little of the great eastward seas, but were well acquainted with those beyond the pillars of Herakles (Straits of Gibraltar), the term ocean, if used definitely and not mythologically, usually meant with them the Atlantic Ocean.

Okeanos, the god of this vast circumfluent salt-river, was the son of Ouranos and Gaia (heaven and earth), and by his sister and consort Têthus, was father of all river-gods and sea-nymphs. Okeanos and Têthus belonged to the Titans or primeval gods of Greece, but retained their sovereignty over Ocean under the succeeding race of Olympian deities, of whom Zeus was the chief; although the Olympian Poseidon then became the supreme watergod, and as such might appear to supersede Okeanos. To reconcile these discrepancies is beyond our power, nor is it of importance.

OK'EGHEM. See OCKEGHEM.

O'KEN, LORENZ, a celebrated German naturalist, was born at the Swabian village of Bohlsbach, 1st August, 1779. His real name was Ockenfuss, which in his first published work he contracted into that of Oken, by which he is best known. He studied medicine and the natural sciences at the universities of Würzburg and of Gottingen, becoming privat-docent at the latter. In 1802 he published his first work, entitled "Grundriss der Naturphilosophie," the earliest of his attempts to apply systematically to natural history and philosophy the principles suggested by Fichte and Schelling. In 1805 he issued his treatise, "Die Zeugung," in which he maintained the proposition that all organic beings originate from and consist of vesicles or cells; and the following year, with the assistance of Kieser, he published a further important contribution to the study of generation in a volume entitled "Beiträge zur Vergleichenden Zoologie, Anatomie, et Physiologie." His originality and ability had now attracted attention, and in 1807 he accepted an invitation to the University of Jena, where he was appointed extraordinary professor of medicine. There and in that year he delivered his inaugural lecture on the "Significance of the Skull Bones," which was immediately published with the title "Über die Bedeutung der Schädelknochen." In this lecture he developed his favourite theory that there is an analogy between the skull or parts of the skull and the vertebral column, and that "the skull is a second body." The poet Goethe in his "Morphologie," published in 1820, laid claim to the original conception of this idea; but his indebtedness to Oken has been clearly proved by Professor Owen. The latter philosopher has also corrected and worked out inductively the "a priori guess" of Oken, and has established the truth that "the head is not a virtual equivalent of the trunk, but is only a portion-i.e. certain modified segmentsof the whole body." In 1812 Oken was appointed ordinary professor of natural history at Jena, and in 1816 he founded his celebrated journal, the Isis, devoted chiefly to science, but which also admitted comments on political matters. The latter having given offence to the court of Weimar, Oken was called upon either to resign his professorship or suppress the Isis. He chose the former alternative, sent in his resignation, transferred the publication of the Isis to Rudolstadt, and remained at Jena as a private teacher of science. In 1821 he broached in the Isis the idea of an annual gathering of German savants, and it was carried out successfully at Leipzig in the following year. To Oken, therefore, may be indirectly ascribed the genesis of the annual scientific gatherings common on the Continent, as well as of the British Association for the Advancement of Science, which at the outset was avowedly organized after his model. In 1828 he accepted a professorship in the University of Munich; but in 1832, on the proposal of the government to remove him to a provincial university, he resigned. In 1833 he was appointed professor of natural history at the newly-established University of Zurich, where he continued to reside until 11th August, 1851, when, full of years and honours, he died. Among his other works the more important are his treatise, "Ueben das Universum als Forsetzung des Sinnensystems" (1808); his "Erste Ideen zur Theorie des Lichts" (1809);