OMSK (32), capital of Western Siberia, on the Om, at its confluence with the Irtish, 1800 m.  E. of Moscow; is within the area of Russian colonisation, and has a military academy, Greek and Roman Catholic cathedrals, and large cattle trade; a number of its inhabitants are political exiles from Europe.

ONEGA, LAKE, in the NW. of Russia, next to Ladoga the largest in Europe, nearly three times the size of Norfolkshire, being 140 m. long and 59 broad; has an irregular shore, deeply indented in the W., many inflowing rivers, but is drained only by the Swir; ice-bound for four months, there is busy traffic the rest of the year; navigation is promoted by canals, but hindered by many reefs; fish abound in the waters.

ONOMATOPOEIA, formations of words resembling in sound that of the things denoted by them.

ONTARIO (2,114), third largest, most populous, richest, and most important province of Canada, lies N. of the great lakes between Quebec and Manitoba, and is thrice the size of Great Britain; the surface is mostly undulating; there are many small lakes, the chief rivers flow eastward to join the Ottawa; agriculture is the chief industry, enormous crops of wheat, maize, and other cereals are raised; stock-rearing and dairy-farming are important; the climate is subject to less extremes than that of Quebec, but the winter is still severe; there are rich mineral deposits, especially of iron, copper, lead, and silver, petroleum and salt; manufactures of agricultural implements, hardware, textiles, and leather are carried on; Toronto (181) is the largest town, Ottawa (44) is the capital of the Dominion, Hamilton (49) an important railway centre; the prosperity of the province is largely promoted by the magnificent waterways, lakes, rivers, and canals with which it is furnished.  Founded by loyalists from the United States after the Declaration of Independence, the province was constituted in 1791 as Upper Canada, united to Quebec or Lower Canada in 1840, it received its present name on the federation of Canada in 1867; education in it is free and well conducted; there are many colleges and universities; municipal and provincial government is enlightened and well organised; the prevalent religious faith is Protestant.

ONTARIO, LAKE, in area almost equal to Wales, is the smallest and easternmost of the five great lakes of the St. Lawrence Basin, North America; it lies between the province of Ontario, Canada, and New York State; receives the Niagara River in the SW., several streams on both sides, and issues in the St. Lawrence in the NE.; on its shores stand Hamilton, Toronto, and Kingston on the N., and Oswego on the S.; canals connect it with Lake Erie and the Hudson River, and it is a busy and always open highway of commerce.

ONTOLOGY, another name for METAPHYSICS (q. v.) or the science of pure being, being at its living source in spirit or God, or Nature viewed as divine, especially as the ground of the spiritual in man and giving substantive being to him.