Ontakio, a county of the province of Ontario, Canada, on the N. shore of Lake Ontario; area, 859 sq. m.; pop. in 1871, 45,890, of whom 19,290 were of English, 12,098 of Irish, 9,976 of Scotch, 1,723 of German, and 1,418 of Dutch origin or descent. It is bounded N. W. by Lake Simcoe, and is watered by several small streams. It is traversed by the Grand Trunk, the Toronto and Nipissing, the Midland, and the Whitby and Port Perry railways. Capital, Whitby.


See Philosophy.


Ontonagon, the extreme N. TV. county of Michigan, bounded N. TV. by Lake Superior, and S. TV. by Wisconsin, from which it is separated in part by the Montreal river, and drained by the Ontonagon, Fire Steel, Iron, Presque Isle, and Black rivers; area, about 2,300 sq. m.; pop. in 1870, 2,845. The surface is hilly, and an elevated range called the Porcupine mountains traverses the northern portion. It contains large quantities of copper and iron ore. In 1870 there were 10 copper mines worked, the products of which amounted to $256,802. The product in 1872 was 725½ tons of ore. Capital, Ontonagon.


Opatas, a tribe of Indians, occupying the eastern and southern part of the state of So-nora, Mexico. They are semi-civilized, but maintain their independence of the state government, with which nevertheless they are on good terms, and often lend assistance against the Apaches. Their chief residence is on the i rivers Yaqui and Mayo, by which names they are commonly known. Their number is estimated at 30,000.


Opelousas, a town and the capital of St. Landry parish, Louisiana, 180 m. W. N. W. of New Orleans; pop. in 1870, 1,546, of whom 6G6 were colored. It is situated in the midst of a fertile and picturesque country, and has considerable trade. A weekly newspaper is published in French and English. Franklin college, founded here in 1839, has been suspended since the civil war.


Ophicleide (Gr., a serpent, and kMc., a key), a large brass wind instrument of the trumpet species, having a loud tone and a deep pitch, and much used in military bands. It forms the base to the trumpets, and has a compass of three octaves and one note. Bass ophicleides are made in C and B-, alto ophi-cleides in F and Eb-. The latter are little used.


See Serpents.


See Gnostics.


Opodeldoc, a name given by Paracelsus to a plaster for all external injuries; now applied to a liniment which is much used as an anodyne application in sprains, bruises, and rheumatic pains. It is prepared by dissolving 3 oz. of common white soap in a pint of alcohol by the heat of a sand bath, and adding an ounce of camphor and a fluid drachm each of oil of rosemary and oil of origanum. It becomes a soft, translucent, yellowish white mass, of the consistency of soft ointment, which liquefies when rubbed upon the skin.


Oppeln, a town of Prussian Silesia, capital of an administrative district of the same name, on the Oder, 50 m. S. E. of Breslau; pop. in 1871, 11,879. It contains an old castle on an island in the Oder, a church built at the end of the 10th century, besides three other Catholic and two Protestant churches, a synagogue, a Catholic gymnasium, and a royal institute for midwives. It has an active trade in wine, cattle, and minerals, and manufactories of linen, ribbons, leather, and pottery. Oppeln was formerly a sovereign principality and the residence of the dukes of Upper Silesia of the house of Piast. The dynasty died out in 1532, when Oppeln was annexed to the empire, and subsequently it became part of Prussia.