WILHELM AUGUST One of the •ost eminent German astronomers of the Nine teenth Century. He was horn at Memel, Prus sia. He studied at KOnigsberg, where the political sciences first attracted him; hut he was subsequently drawn away to astronomy by the lectures of Bessel, by whom he was employed to make calculations and obser vations. In 1820 he was appointed assistant to Bessel in the Konigsberg Observatory, and in 1823 succeeded Walbeek as astronomer at the observatory of Abo, in Finland. Here he be gan a series of observations on the fixed stars which have a perceptible "proper motion." His studies were unfortunately interrupted by a fire which destroyed the observatory; but after a time he resumed them in a new observa tory at Helsingfors, and published a catalogue of not less than 560 stars having "proper mo tions." This contained the results of his ob servations at Abo, and received from the Acad emy of Saint Petersburg the Demidoff Prize. In 1837 he was invited to fill the chair of astron omy at the University of Bonn. Argelander
was long engaged in a series of observations on the changes of light in variable stars, and he also added to our ideas concerning the progres sive motion of the solar system in space. Arge lander's works include: Obserrationes Astro vontictr in Specylm'Unicersitatis •ennieo Faette viols., Helsingfors, 1830-32); Ura nometrie (Berlin, 1843), containing eighteen celestial charts of fixed stars seen with the naked eye: Mittlerc Ocrter von 3,3.811 Sternen (Bonn, 1867) ; and a few others of considerable importance. Ms greatest work, however, is the atlas des nordlieben gestirnten Ilinnnels (Bonn, 1857) , with a Sternrerzeichnis (Bonn, t859-62, Vols. ll L-V of the Astronomische Beobaehtungen auf der Sternwarte tin Bonn). This work contains an enormous number of ob servations carried out by Argelander and his assistants during the nine years from 1852 to 1861.