202 MEMOIR OF ENCKE. 



of comets ; the latter as well with reference to parabolic as elliptical and hyper- 

 bolic orbits ; the calculation of occultations and transits, the testing of different 

 astronomical instruments, and in an especial manner the disturbances arising 

 from the approximations of the heavenly bodies. Not only did he set forth in 

 more than one treatise, and, with singular clearness, rules for the calculation of 

 these disturbances according to the old method of Lagrange, as perfected by 

 Gauss and Bessel,but almost simultaneously with the younger Bond at Cambridge, 

 in America, he suggested a new method by which the calculation of the orbital 

 elements of many of the recentl}^ discovered small planets was essentially facili- 

 tated. By this, instead of the changes which the disturbances produce in the 

 elements of the orbits, it was proposed immediately to calculate those Avhich the 

 rectangular co-ordinates undergo. This method, if somewhat uncertain for long 

 periods of time, was, , on account of its convenience, extensively employed, till 

 the later method devised by Hansen became more generally introduced. Encke 

 also composed some physical treatises on dioptrics and the ballistic problem, as 

 well as several popular lectures on different astronomical suljjects. The lattei", 

 though but partially published, were distinguished for an ingenious co-ordination 

 of facts, and were received with unqualified applause. 



Towards his numerous friends and acquaintances Encke maintained that 

 uprightness of intention which, with his sympathetic and open nature, his clear 

 and unperverted judgment, won him the highest consideration and love. In his 

 domestic circle the course of a serene life was disturbed by no loss until, in 1856, 

 the news arrived of the death of his second son at Rio Janeiro. 



On the 17th of November, 1856, Encke fell in the street from sudden vertigo. 

 Although the apprehensions at first felt were not realized, yet the rare vigor of 

 earlier years did not return. A new and severe loss befell him the next year in 

 the death of his brother, the same with whom he had entered the Prussian artil- 

 lery, 45 years before, and who had since been advanced to the rank of lieutenant 

 general. A few years later he lost his sister, who had lived in his Louse. In 

 February, 1863, he sustained an apoplecticattack, from which he so far recovered 

 as to be able to return to his labors, and even to journey to Leipsic in order to 

 witness the nuptials of his old scholar, professor Bruhns, but his condition 

 remained so critical that soon all intellectual effort was forbidden him. He 

 therefore spent the summer with his friends in Goslar and Wernigerode, and, on 

 his return, was still bent upon resuming his labors, but his physician, the more effec- 

 tually to prevent this, ordainedhim a new journey to Kiel ; from Kiel he went with 

 his family in December, 1863, to Spandau, where his eldest son was established. 

 At his urgent and oft rei)eated request he was permitted by his medical adviser 

 again to visit the observatory. Here he traversed with interest the observiiig 

 rooms, and marked with particular attention the changed erection of the great 

 refractor, which was now borne upon a stone pillar instead of the old wooden 

 support. He soon tired, however, and returned contentedly to Spandau. From 

 this time his bodily strength and mental activity continued to decline, until a 

 second apoplectic attack occurred In July of the next year, and was followed ])y 

 complete paralysis. A painless death released him, 26th August, 1865, from 

 long sufferings. 



If Encke's services in behalf of astronomy secure him an enduring remem- 

 brance, it continues also to survive in the grateful recollection of his numerous 

 pupils. In the calculations for the Year-book, as w'ell as in the prosecution of 

 other astronomical labors, he delighted to find himself surrounded by young 

 people, to whose instruction in all parts of knowledge he gave himself with a 

 rare talent for conveying it; ever entertaining with them the most friendly ixda- 

 tions, and thus winning to the pursuit of his science a number of pupils unequalled, 

 perhaps, by any other astronomer. Among them ma}^ be counted the present 

 directors of the observatories of Berlin, Breslau, Leipsic, Hamburg, Bilk, Copen- 

 hagen, Helsingfors, and Dublin, who, with many others, have contributed through 

 their scientific labors greatly to extend his reputation. 



