time as joint king of Northumbria with Olaf Sitricson. It is possible that he was the "Olaf of Ireland" who was called by the Northumbrians after Æthelstan's death, but both the Olafs appear to have accepted the invitation. He was killed in 941 at Tyningham near Dunbar.
See W. F. Skene, Celtic Scotland, vol. i. (1876), and J. R. Green, The Conquest of England, vol. i. (1899).
ÖLAND, an island in the Baltic Sea, next to Gotland the largest belonging to Sweden, stretching for 85 m. along the east coast of the southern extremity of that country, from which it is separated by Kalmar Sound which is from 5 to 15 m. broad. The greatest breadth of the island is 10 m., and its area 519 sq. m. Pop. (1900) 30,408. Consisting for the most part of Silurian limestone, and thus forming a striking contrast to the mainland with its granite and gneiss, Öland is further remarkable on account of the peculiarities of its structure. Down the west side for a considerable distance runs a limestone ridge, rising usually in terraces, but at times in steep cliffs, to an extreme height of 200 ft.; and along the east side there is a parallel ridge of sand, resting on limestone, never exceeding 90 ft. These ridges, known as the Western and Eastern Landborgar, are connected towards the north and the south by belts of sand and heath; and the hollow between them is occupied by a desolate and almost barren tract: the southern portion, or Alfvar (forming fully half of the southern part of the island), presents a surface of bare red limestone scored by superficial cracks and unfathomed fissures, and calcined by the heat refracted from the surrounding heights. The northern portion is covered at best with a copse of hazel bushes. Outside the ridges, however, Öland has quite a different aspect, the hillsides being not infrequently clothed with clumps of trees, while the narrow strip of alluvial coast-land, with its cornfields, windmills, villages and church towers, appears fruitful and prosperous. There are a few small streams in the island; and one lake, Hornsjö, about 3 m. long, deserves mention. Of the fir woods which once clothed a considerable area in the north the Böda crown-park is the only remnant. Grain, especially barley, and sandstone, are exported from the island, and there are cement works. A number of monuments of unknown age exist, including stones (stensättningar) arranged in groups to represent ships. The only town is Borgholm, a watering-place on the west coast, with one of the finest castle ruins in Sweden. The town was founded in 1817, but the castle, dating at least from the 13th century, was one of the strongest fortresses, and afterwards, as erected by the architect Nicodemus Tessin the elder (1615-1681), one of the most stately palaces in the country. The island was joined in 1824 to the administrative district (län) of Kalmar. Its inhabitants were formerly styled Öningar, and show considerable diversity of origin in the matter of speech, local customs and physical appearance.
From the raid of Ragnar Lodbrok's sons in 775 Öland is frequently mentioned in Scandinavian history, and especially as a battleground in the wars between Denmark and the northern kingdoms. In the middle ages it formed a separate legislative and administrative unity.
OLAUS MAGNUS, or Magni (Magnus, i.e. Stora, great, being the family name, and not a personal epithet), Swedish ecclesiastic and author, was born at Linköping in 1490 and died at Rome in 1558. Like his elder brother, Johannes Magnus, he obtained several ecclesiastical preferment's (a canonry at Upsala and at Linköping, and the archdeaconry of Strengnes), and was employed on various diplomatic services (such as a mission to Rome, from Gustavus I., to procure the appointment of Johannes Magnus as archbishop of Upsala); but on the success of the reformation in Sweden his attachment to the old church led him to accompany his brother into exile. Settling at Rome, from 1527, he acted as his brother's secretary, and ultimately became his successor in the (now titular) archbishopric of Upsala. Pope Paul III., in 1546, sent him to the council of Trent; later, he became canon of St Lambert in Liége; King Sigismund I. of Poland also offered him a canonry at Posen; but most of his life, after his brother's death, seems to have been spent in the monastery of St Brigitta in Rome, where he subsisted on a pension assigned him by the pope. He is best remembered as the author of the famous Historia de Gentibus Septentrionalibus (Rome, 1555), a work which long remained for the rest of Europe the chief authority on Swedish matters and is still a valuable repertory of much curious information in regard to Scandinavian customs and folk-lore.
The Historia was translated into Italian (Venice, 1565), German (Strassburg, 1567), English (London, 1658) and Dutch (Amsterdam, 1665); abridgments of the work appeared also at Antwerp (1558 and 1562), Paris (a French abridged version, 1561), Amsterdam (1586), Frankfort (1618) and Leiden (1652). Olaus also wrote a Tabula terrarum septentrionalium . . . (Venice, 1539).
OLBERS, HEINRICH WILHELM MATTHIAS (1758–1840), German astronomer, was born on the 11th of October 1758 at Arbergen, a village near Bremen, where his father was minister. He studied medicine at Göttingen, 1777-1780, attending at the same time Kaestner's mathematical course; and in 1779, while watching by the sick-bed of a fellow-student, he devised a method of calculating cometary orbits which made an epoch in the treatment of the subject, and is still extensively used. The treatise containing this important invention was made public by Baron von Zach under the title Ueber die leichteste und bequemste Methode die Bahn eines Cometen zu berechnen (Weimar, 1797). A table of eighty-seven calculated orbits was appended, enlarged by Encke in the second edition (1847) to 178, and by Galle in the third (1864) to 242. Olbers settled as a physician in Bremen towards the end of 1781, and practised actively for above forty years, finally retiring on the 1st of January 1823. The greater part of each night (he never slept more than four hours) was meantime devoted to astronomy, the upper portion of his house being fitted up as an observatory. He paid special attention to comets, and that of 1815 (period seventy-four years) bears his name in commemoration of its detection by him. He also took a leading part in the discovery of the minor planets, re-identified Ceres on the 1st of January 1802, and detected Pallas on the 28th of March following. His bold hypothesis of their origin by the disruption of a primitive large planet (Monatliche Correspondenz, vi. 88), although now discarded, received countenance from the finding of Juno by Harding, and of Vesta by himself, in the precise regions of Cetus and Virgo where the nodes of such supposed planetary fragments should be situated. Olbers was deputed by his fellow-citizens to assist at the baptism of the king of Rome on the 9th of June 1811, and he was a member of the corps législatif in Paris 1812-1813. He died on the 2nd of March 1840, at the age of eighty-one. He was twice married, and one son survived him.
See Biographische Skizzen verstorbener Bremischer Aerzte, by Dr G. Barkhausen (Bremen, 1844); Allgemeine geographische Ephemeriden, iv. 283 (1799); Abstracts Phil. Trans, iv. 268 (1843): Astronomische Nachrichten. xxii. 265 (Bessel), also appended to A. Erman's Briefwechsel zwischen Olbers und Bessel (2 vols., Leipzig, 1852); Allgemeine Deutsche Biographie (S. Günther); R. Grant, Hist. of Phys. Astr. p. 239; R. Wolf, Geschichte der Astronomie, p. 517. The first two volumes of Dr C. Schilling's exhaustive work, Wilhelm Olbhers, sein Leben und seine Werke, appeared at Berlin in 1894 and 1900, a third and later volume including his personal correspondence and biography. A list of Olbers's contributions to scientific periodicals is given at p. xxxv of the 3rd ed. of his Leichteste Methode, and his unique collection of works relating to comets now forms part of the Pulkowa library.
OLBIA, the chief Greek settlement in the north-west of the Euxine. It was generally known to the Greeks of Hellas as Borysthenes, though its actual site was on the right bank of the Hypanis (Bug) 4 m. above its junction with the estuary of the Borysthenes river (Dnieper). Eusebius says that it was founded from Miletus c. 650 B.C., a statement which is borne out by the discovery of Milesian pottery of the 7th century. It first appears as enjoying friendly relations with its neighbours the Scythians and standing at the head of trade routes leading far to the north-east (Herodotus iv.). Its wares also penetrated northward. It exchanged the manufactures of Ionia and, from the 5th century, of Attica for the slaves, hides and corn of Scythia. Changes of the native population (see Scythia) interrupted this commerce, and the city was hard put to it to
