342

HISTORY OF PHYSICAL ASTRONOMY.

impetus was given to researches of this nature, hy the resolution of theBerlin Academy of Sciences to procure the construction of a series ofcharts representing the relative positions of all the stars, down to thetenth order of magnitude, in a zone of the celestial regions extending 16° oneach side of the equator. All the charts connected with this great under-taking have not yet been executed; but we have already had occasion toillustrate their great utility, in our account of the discovery of the planetNeptune . It was probably by reflecting on the advantage of such deli-neations of the celestial regions that M. Henclte, an amateur astronomerof Driessen, in Germany , was induced, about the year 1830, to commencea careful survey of those regions wherein it was most likely that any addi-tional planets would be found. During fifteen years he continued withunwearied assiduity to prosecute this object, tracing the relative positionsof the small stars, and making himself acquainted with their various con-figurations. At length his unflinching perseverance met with its due reward.On the 8th of December, 1845, while engaged in examining a portionof the fourth hour of right ascension, his attention was directed to a smallunknown star which appeared, between two others of about the same size,with it. As he had acquired an intimate acquaintance with this part ofthe heavens, he felt confident that the star had not been previously visiblein it. He therefore suspected that he had discovered a planet, and hewrote to M. Encke, of the Observatory of Berlin, announcing the exist-ence of the unknown star, and communicating to him its position on theday before mentioned. On the evening of the 14th of December, the Berlinastronomers directed the magnificent refractor of the observatory to thepart of the heavens in which M. Ilencke had asserted he had seen thesuspected planet, and presently they discovered a star of the ninth magni-tude, which was not marked in the corresponding chart of the academy,executed by Professor Knorre. The subsequent observations of the sameevening shewed it to be a planet. It was then retrograding with a dailymotion in right ascension, amounting to 14' 21".2 of arc. On this occasionthe elements of the orbit were rapidly determined, not by Gauss indivi-dually, as on previous occasions of a similar kind, hut by a host of youngastronomers throughout Europe , who had become familiar with the methodsof that illustrious master. The results of their calculations shewed thebody to be one of the family of asteroids. The honour of naming it wasdelegated by the discoverer to M. Encke, who conferred on it the appella-tion of Astnea.

The industry of M. Hencke was soon again rewarded by a similardiscovery. On the 1st of July, 1847, while engaged in examining theseventeenth hour of right ascension, he perceived a small star of aboutthe ninth order of magnitude, which was not marked in the correspondingmap of the academy, constructed by Dr. Bremiker. On the 3rd he re-peated his observation, and found that during the intermediate period itsright ascension had sensibly diminished, while its southern declination hadincreased. It proved to be another of the smaller planets. Gauss, who hadbeen invited to choose its name, bestowed on it the appellation of Hebe .

The year 1847 was not destined to come to a close before it was sig-nalized by two other discoveries of a similar nature. Mr. Iiind, theAstronomer attached to the Observatory of Mr. Bishop , Regent’s Park,London , had been for some time engaged in revising the Berlin maps,of which the utility had now become so apparent. He had also under-taken the formation of ecliptical charts for a few of the hours of right