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 that can pass through the Welland canal locks, which are 270 ft. long, 45 ft. wide and 14 ft. deep. Freight consists principally of coal shipped from Charlotte, Great and Little Sodus bays and Oswego to Canadian ports in the lakes, and to ports on the St Lawrence river; of grain shipped through the Welland canal to the St Lawrence; and of lumber from Canadian ports. There is a large passenger traffic, including pleasure trips, principally radiating from Toronto. Ports on the lake are limited in capacity to vessels drawing not more than 14 ft. of water. The principal Canadian ports are Kingston, at the head of the St Lawrence river; Toronto, where the harbour is formed by an island with improved entrance channels constructed both east and west of it; and Hamilton, at the head of the lake, situated on a landlocked lagoon, connected with the main lake by Burlington channel, an artificial cut. The principal United States port is Oswego, where a breakwater has been built, making an outer harbour. The construction of a breakwater was undertaken in 1907 by the United States government at Cape Vincent to form a harbour where westbound vessels can shelter from storm before crossing the lake.

The difference of 327 ft. in level between Lake Ontario and Lake Erie is overcome by the Welland canal, which leads southward from Port Dalhousie. It accommodates vessels 255 ft. in length, with a draught of 14 ft. The Murray canal, opened for traffic on the 14th of April 1890, extends from Presqu’ile bay, on the north of the lake, to the head of the bay of Quinte, and enables vessels to avoid 70 m. of open navigation. It is 11 ft. deep below the lowest lake level, and has no locks. It is proposed to have the eastern terminus of the Trent canal system (see ) at the head of the bay of Quinte, entering through the Trent river. At Kingston the Rideau canal, extending 128 m. to Ottawa, enters the St Lawrence river at the foot of the lake.

.—Bulletin No. 17, Survey of Northern and Northwestern Lakes, U.S. Lake Survey Office (Detroit, Mich., 1907); Publication No. 108 D., Sailing Directions for Lake Ontario, Hydrographic Office, U.S. Navy (Washington, D.C., 1902); St Lawrence Pilot (7th ed.), Hydrographic Office, Admiralty (London, 1906).

ONTENIENTE, a town of eastern Spain, in the province of Valencia; on the right bank of the Clariano or Onteniente, a sub-tributary of the Júcar, and on the Játiva-Villena railway. Pop. (1900) 11,430. Onteniente has a parish church remarkable for its lofty square tower, and a palace of the dukes of Almodovar. There is a large modern suburb outside the old town, which was formerly a walled city; some vestiges of the ramparts still remain. Linen and woollen cloth, paper, brandy, furniture and earthenware are manufactured; and there is some trade in cereals, wine and oil.

 ONTOLOGY (adapted from a modern Latin form ontologia used by Jean le Clerc 1692; Gr. ,  , pres. part, of  to be, and  , science), the name given to that branch of philosophy which deals specially with the nature of being i.e. reality in the abstract. The idea, denoted in modern philosophy by the term “ontology” in contrast to the broader “metaphysics” and the correlative “epistemology,” goes back to such phrases as , which Plato uses to describe the absolute reality of ideas; Plato, however, uses the term “dialectic” for this particular branch of metaphysics. Aristotle, likewise, holding that the separate sciences have each their own subject matter, postulates a prior science of existence in general which he describes as “first philosophy.” So far, therefore, the science of being is distinguished not from that of knowing but from that of the special forms of being: as to the possibility of objective reality there is no question. A new distinction arises in the philosophy of Wolff who first made “ontology” a technical term. Theoretical philosophy (metaphysics) is by him divided into that which deals with being in general whether objective or subjective, as contrasted with the particular entities, the soul, the world and God. The former is ontology. This intermediate stage in the evolution of the science of being gave place to the modern view that the first duty of the philosopher is to consider knowledge itself (see ), and that only in the light of conclusion as to this primary problem is it possible to consider

the nature of being. The evolution of metaphysics has thus relegated ontology to a secondary place. On the other hand it remains true that the science of knowing is inseparable from, and in a sense identical with that of being. Epistemological conclusions cannot be expressed ultimately without the aid of ontological terms.

 ONYX, a banded chalcedony or striped agate, composed of white layers alternating with others of black, brown or red colour. A typical onyx consists of two or more black and white strata, whilst the term sardonyx is applied to the stone if it contains red or brown bands (see ). Probably those varieties which show red and white zones originally suggested the name “onyx,” from Gr. (a finger nail), since the colours of such stones may be not unlike those of the nail. The onyx when worked by the lapidary was often designated by the diminutive ; and at the present day the term nicolo, a corruption of the Italian diminutive onycolo, is applied to an onyx which presents a thin layer of chalcedony deriving a bluish tint from the subjacent black ground. The Hebrew soham is translated in the authorized version of the Old Testament “onyx,” but the revised version gives in some of the passages an alternative marginal reading of “beryl.” The position of the land of Havilah, which yielded the onyx-stone, is uncertain.

India has for ages supplied the finest onyxes, and hence jewellers apply the expression “Oriental onyx” to any stone remarkable for beauty of colour and regularity of stratification, quite regardless of its locality. As far back as the 1st century the author of the Periplus Maris Erythraei mentions the onyx among the products of Plythanae, a locality probably identified with Paithan on the Godavari; and he further states that the stones were taken down to Barygaza, the modern Broach, where the agate trade still flourishes. It is probable that the early Greeks and Romans derived their prized agate-cups from this locality. The Indian onyx is found, with agate and jasper-pebbles, in river gravels derived from the disintegration of the amygdaloidal volcanic rocks of the Deccan. A great deal of onyx now sold is obtained from South American agates, cut in Germany. It often happens that the lower deposits in an agate-nodule are in horizontal layers, forming onyx, while the other deposits have adapted themselves to the curved contours of the cavity. The onyxes cut from agate-nodules are usually stained artificially, as explained under.

The onyx is largely used for beads, brooches, pins, ring-stones and other small ornamental objects, while the larger pieces are occasionally wrought in the form of cups, bowls, vases, &c. Onyx is the favourite stone for cameo work, advantage being taken of the differently-coloured layers to produce a subject in relief on a background of another colour. For fine examples of ancient cameo-work in onyx and sardonyx see.

It should be noted that the term onyx, or onychite, was formerly, and is still sometimes, applied to certain kinds of banded marble, like the “oriental alabaster” (see ). Such substances are quite distinct from the hard siliceous onyx, being much softer and less precious: they are, in fact, usually deposits of calcium carbonate like stalagmite and travertine. The ornamental stones known as Mexican onyx, or Tecali marble, and Algerian onyx are of this character; and in order to avoid any confusion with the true onyx it is well to distinguish all the calcareous “onyxes” as onyx-marble. The well-known “Gibraltar stone” is an onyx-marble, with brown bands, from caverns in the limestone of Gibraltar. The Tecali onyx, sometimes with delicate green shades, takes its name from the district of Tecali; one of its localities being La Pedrara, about 21 m. from the city of Puebla.

For onyx-marbles see Dr G. P. Merrill, ''Rep. U.S. Nat. Mus.'' for 1893 (1895), p. 539.

 OOLITE (Gr. , egg, , stone), in geology, a term having two distinct meanings. In (q.v.) it denotes a type of rock structure characterized by the presence of minute spherical grains resembling the roe of a fish; if the grains become larger, the structure is said to be pisolitic (Gr. , pea). In