ENCKE

encke, johann franz (1791-1865), german astronomer, was born at hamburg on the 23rd of september 1791. matriculating at the university of gottingen in 1811, he began by devoting himself to astronomy under carl friedrich gauss; but he enlisted in the hanseatic legion for the campaign of 1813-14, and became lieutenant of artillery in the prussian service in 1815. having returned to gottingen in 1816, he was at once appointed by benhardt von lindenau his assistant in the observatory of seeberg near gotha. there he completed his investigation of the comet of 1680, for which the cotta prize was awarded to him in 1817; he correctly assigned a period of 71 years to the comet of 1812; and discovered the swift circulation of the remarkable comet which bears his name (see comet). eight masterly treatises on its movements were published by him in the berlin _abhandlungen_ (1829-1859). from a fresh discussion of the transits of venus in 1761 and 1769 he deduced (1822-1824) a solar parallax of 8".57, long accepted as authoritative. in 1822 he became director of the seeberg observatory, and in 1825 was promoted to a corresponding position at berlin, where a new observatory, built under his superintendence, was inaugurated in 1835. he directed the preparation of the star-maps of the berlin academy 1830-1859, edited from 1830 and greatly improved the _astronomisches jahrbuch_, and issued four volumes of the _astronomische beobachtungen_ of the berlin observatory (1840-1857). much labour was bestowed by him upon facilitating the computation of the movements of the asteroids. with this end in view he expounded to the berlin academy in 1849 a mode of determining an elliptic orbit from three observations, and communicated to that body in 1851 a new method of calculating planetary perturbations by means of rectangular co-ordinates (republished in w. ostwald's _klassiker der exacten wissenschaften_, no. 141, 1903). encke visited england in 1840. incipient brain-disease compelled him to withdraw from official life in november 1863, and he died at spandau on the 26th of august 1865. he contributed extensively to the periodical literature of astronomy, and was twice, in 1823 and 1830, the recipient of the royal astronomical society's gold medal. see _johann franz encke, sein leben und wirken_, von dr c. bruhns (leipzig, 1869), to which a list of his writings is appended. also, _month. notices roy. astr. society_, xxvi. 129; _v.j.s. astr. gesellschaft_, iv. 227; berlin. _abhandlungen_ (1866), i., g. hagen; _sitzungsberichte_, munich acad. (1866), i. p. 395, &c. (a. m. c.) enclave (a french word from _enclaver_, to enclose), a term signifying a country or, more commonly, an outlying portion of a country, entirely surrounded by the territories of a foreign or other power, such as the detached portions of prussia, saxony, &c, enclosed in the thuringian states. (from the point of view of the states possessing such detached portions of territory these become "exclaves.") "enclave" is, however, generally used in a looser sense to describe a colony or other territory of a state, which, while possessing a seaboard, is entirely surrounded landward by the possession of some other power; or, if inland territory, nearly though not entirely so enclosed, e.g. the lado enclave in equatorial africa.