Such was Oken's first revolutionary adventure in the domain of natural history. In 1805 he published his treatise, "Die Zeugung," in which, he says, "I first advanced the doctrine that all organic beings originate from and consist of vesicles or cells," a doctrine popular in our own day; and he continues, "in mine and Kieser's Beyträge zur vergleichenden Zoologie, Anatomie et Physiologie," published in 1806, "I have shown that the intestines originated from the umbilical vesicle, and that this corresponds to the vitellus." Oken's originality 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, "Über die Bedentung der Schädelknochen" (on the significance of the skull-bones), which, perhaps, of all his writings has been practically the most influential. In it he developed his favorite theory that "the skull is a second body." The notion first came upon him, according to his own account, in a journey over the Hartz mountains in 1806. He saw at his feet the bleached skull of a deer, which he picked up, and while he examined it the idea flashed upon him "it is a vertebral column." The analogy, it has been maintained, had struck others before him, and it is still a moot-point whether Goethe, who enlarged on it in his Morphologie, was or was not indebted for it to Oken. In the hands of Richard Owen this "à priori guess" of Oken's has been corrected and worked out inductively, and the truth established that "the head is not a virtual equivalent of the trunk, but is only a portion, i.e., certain modified segments of 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, intended as a scientific organ, but which became a vehicle of liberal political thinking, and thus displeased the authorities. The alternative was given him of resigning his professorship or of surrendering the publication of the Isis. He chose the former; 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 Leipsic in the following year. To Oken, therefore, may be indirectly ascribed the genesis of the British Association at home, and of so many similar assemblages on the continent. In 1828 he accepted a professorship in the university of Munich, where for a twelvemonth before he had been a privat-docent; but the government resolving to remove him to a provincial university, he resigned. In 1832 he became a professor at the newly-established university of Zurich, where he died, full of years and honours, on the 11th of August, 1851. Among Oken's other works, and as characterized by himself in the preface formerly referred to, may be mentioned his treatise, "Ueber das Universum als Forsetzung des Sinnensystems," 1808; his "Erste Ideen zur Theorie des Lichts," 1808; his Grundzeichnung des natürlichen system der Erze," and above all his "Lehrbuch der Naturphilosophie," 1810-11, 3rd edition, 1843, containing the summary and application of all his doctrine, and translated into English for the Ray Society by Mr. Alfred Tulk in 1847. It was followed by his "Lehrbuch der Naturgeschichte," 1813-27, and by his "Allgemeine Natur-Geschichte für alle Stände," 1833-41. "Oken's real claims to the support and gratitude of naturalists," says Richard Owen, "rest on his appreciation of the true relations of natural history to intellectual progress, of its superior teachings to the mere utilitarian applications of observed acts of its intrinsic dignity as a science."
OLBERS, Henrich Wilhelm Mathias, M.D., a celebrated astronomer and physician, was born at Arbergen, near Bremen, on the 11th October, 1758. He received his medical education at the university of Göttingen, and seems to have found leisure for carrying on his astronomical studies without interfering with the practice of his profession. He erected a small observatory in his house at Bremen, and furnished it with several excellent instruments, chiefly by English artists. The earliest astronomical observations of Olbers were made upon comets. He determined from his own observations the elements of the comet of 1779, by means of Euler's method, which he subsequently rendered more simple and accurate. This method, which was published by Kaven Zæds, 1797, was afterwards given by Delambre in his great work on astronomy. On the 1st of January, 1801, Professor Piazzi of Palermo had discovered the small planet Ceres between the orbits of Mars and Jupiter, or the first of the seventy asteroids, as they have been called, which revolve in almost interlacing orbits in that remarkable part of the solar system. On the 28th March, 1802, Dr. Olbers discovered in the same locality another small planet, to which he gave the name of Pallas, having nearly the same periodic line as Ceres, but having its orbit much more inclined to the ecliptic. The singular coincidence of the orbits of these two bodies induced Olbers to suppose, that they were the fragments of a larger planet which had burst from some internal convulsion, and he predicted that if this hypothesis was well founded other fragments would be discovered. This prediction was verified when, in September, 1804, M. Harding of Bremen discovered in the same part of the system a third fragment, to which he gave the name of Juno. Thus encouraged, Dr. Olbers devoted himself between the years 1804 and 1807 to the survey of that region of the heavens, and on the 29th of March, 1807, he was rewarded by the discovery of a fourth fragment, to which he gave the name of Vesta. No other asteroids were discovered in the lifetime of Olbers; but on the 8th December, 1843, a fifth, called Astræa, was discovered by M. Hencke of Driessen in Prussia, at nearly the same distance from the sun as Juno. Since that time new asteroids have been discovered almost every year, their number now amounting to seventy, forming as it were a planetary ring between Mars and Jupiter. Mr. Leverrier is of opinion that a similar ring of asteroids exists between Mercury and the Sun, and in the neighbourhood of the Earth. On the 6th March, 1815, Dr. Olbers discovered a comet without a visible nucleus; and in 1826 he published a paper in order to show the probability that a comet might come into collision with the earth. Dr. Olbers was elected a fellow of the Royal Society of London in 1804, and in 1829 a foreign member of the Academy of Sciences in Paris. He was a knight of the order of Dannebroga, and of the Red Eagle in Russia. He died at Bremen on the 2d March, 1840, and his bust was placed in the public library of that city. Dr. Olbers published in 1790 a thesis, "De oculi mutationibus internis," a theory of the adjustment of the eye to different distances, which has no satisfactory foundation; and in 1832 he contributed to the Annuaire du Bureau des Longitudes, a memoir with the title of "De l'influence de la Lune sur les Saisons et sur le Corps Humain."—D. B.
OLDCASTLE, Sir John, the "good Lord Cobham," a gallant soldier and earnest reformer, was born in the reign of Edward III. He obtained the title of Lord Cobham with the hand of the heiress of the last of the name. Having read the writings of Wycliffe, he became convinced of the need of a reformation of the church, and was soon recognized as a leader of the Lollards. In Henry IV.'s reign he served with distinction in France, and was a companion in arms with the warlike prince of Wales. Nevertheless, the latter on his accession to the throne in 1413 as Henry V., leant upon the clergy for support to his dubious title to the crown, and did not hesitate to recompense their good will by a hearty persecution of the formidable Lollards. Wild rumors were spread abroad that one hundred thousand heretics were about to promulgate their doctrines by force, that Lord Cobham was their leader, and believed himself to be Elias, who was to establish the kingdom of Christ and put down the pope. Henry questioned his old friend, who stoutly asserted his conviction that the clergy as a whole was antichrist, the pope being the head, the prelates the limbs, and the religious orders the tail of the beast. Henry gave up the heretic to the ecclesiastical authorities. Cobham was examined by Arundel, archbishop of Canterbury, and sent to the Tower, from which he escaped. He is charged with making a seditious attempt to seize the king and occupy London in force. If he were really concerned in the miserable meeting at St. Giles'-in-the-Fields, he could never have deserved the reputation of a military leader. So feeble was the show of insurrection, and so easily was it suppressed, that it may be suspected the plot was but a trap for catching heretics, for whom the stake was then first erected in England. Cobham escaped into Wales where he remained for four years. In 1417, while Henry was in France, the Lollards made a real and strong effort to obtain their rights—Cobham being at their head. They were defeated by the duke of Bedford; Cobham, taken prisoner, died a horrible death, after being suspended alive in chains over a fire.—(See Gilpin's Lives of the Reformers.)—R. H.
OLDENBURG, House of. The house of Oldenburg is one of the most illustrious in Europe; the kings of Denmark, the emperors of Russia, and the late royal family of Sweden being all descended from it. The county of Oldenburg is the ancient
