BESSEL, FItIEnRIcH WiLifF,L31, one of the most distinguished of modern astrono mers, was b. at Minden, July 22, 1784. In 1806, he was, on the recommendation of Others, whom he had greatly assisted by his remaikable expertness in calculation, appointed assistant to Sehrfiter at Lilienthal. In 1810. he published his researches on the orbit of the great comet of 1807, which gained for him the Lalande prize of the Paris academy of sciences. In the same year he was appointed director of the new observa tory to lie erected by the king of Prussia at Konigsberg; and repairing thither immedi ately, superintended the erection and the mounting of the instruments. The establish ment was completed in three years. In 181.8, B. published his Fundamenta Astronomiai —giving the results of Bradley's Greenwich observations—a work upon which he had been engaged for eleven years. This work is one of the highest value to astronomers. It is described by a competent authority as having laid the foundations of the principal improvements which have been made in astronomy since the date of its publication. In 1830 appeared his Tabulte Regiomontarar, forming a kind of supplement to the above work. Besides numerous papers of an important character (nearly 200 in all) scattered through various scientific journals, lie also published an inquiry on the seconds' pendulum, for Berlin (1828, and again in 1837), Astronomical Rescarclas (2 vols., Konigsb. 1841-42). His paper on the precession of the equinoxes gained him the prize of the Berlin academy. After a series of three years' observations he succeeded in determining the
annual parallax of the fixed star 61 Cygni (see STAns), an achievement honorable not only as the first of its kind, but for the marvelous skill and patience necessary for its „ accomplishment. In the years 1824-33, B. made a series of d 5,011 observations in 536 sittings, and completed a catalogue of stars (extending to the ninth magnitude) within the zone from n. to 15' s. declination. These were afterwards reduced by Weisse. In one of his lectures, delivered at KOnigiberg in 1840, B. indicated the existence of the new planet afterwards discovered by Le Perrier. and named Neptune; and but for the death of a favorite son. he in all proba.bility would have undertaken the investigation of the problem. B.'s Popular Lectures on Astronomy, given at Konigsberg, 1832-44, were edited by his friend Schumacher, and published at Hamburg in 1848, two years after his death, which took place Mar. 7, 1846. All scientific associations, both on the continent and in England, were eager to confer honor on themselves by enrolling B. as one of their members. He was a thoroughly practical man of science, never allowing himself to lie carried away by any theory, however inviting, and particularly remarkable for the precision of his calculations, being satisfied with nothing less than perfect exactness.