66 Account of Dr. Oilers > the celebrated A/lrottomef, 



from obfervations, which was published, with a preface by 

 the editor, at Weimar, in the year 1797. 



Newton himfelf confidered the calculation of the orbit 

 of a comet as exceedingly difficult, and for this reafon he 

 calls the problem hnge SffuiUimum. The greateft and moft 

 ingenious mathematicians of the kft century employed their 

 talents, with various fuccefs, on this difficult fubject; fuch as 

 La Caille, Eulcr, La Grange, Lambert, Bofcovich, Du Se - 

 jour, Condorcct, Hcnnert, Tempelhof, Laplace, Sec. : all the 

 rcfources of genius and all the formulae of the higher analyfis 

 have been tried ; but none of the methods deviled can be 

 fimpler, and at the fame lime more elegant, than that of 

 Dr. Olbers. It can indeed be laid, that the whole was ef- 

 fected by his own genius; for the conci fetters and eafinefs of 

 his method are chiefly founded on fome happv ideas, and on 

 a fuppolition which approaches very near the truth. But it 

 required no little ingenuity and practice in calculation to 

 apply thefe ideas to the folution of the problem. 



In the year 1780 he wrote his inaugural diflertation, De 

 Oculi Mutationibus mlernis ; that is, on the Method in which 

 the Eye changes to lee diftinctly near and diftant Objects. 

 Moft phyfiologifts have adopted his theory on this fubject; 

 and it has lately been placed beyond all doubt by Ramfden's 

 and Home's experiments, publilhed in the Transactions of 

 the Royal Society. 



From Gottingen Olbers proceeded to Vienna, in 1781, to 

 acquire a more extenfive knowledge of medicine under Stoll, 

 Quarin, Stork, and other eminent mafters. Recommenda- 

 tions which he carried with him from Kaftner procured him 

 a favourable reception from father Hell the aftronomer, and 

 from many of the Vienna literati ; but he could not turn it 

 to much advantage, as his application to the principal object 

 of his ftudy, and attendance at the hofpitals, left him very 

 little leifure for atlronomy. He was the rirft, however, who 

 obferved the Georgian planet, or Uranus, on the 17th of 

 Auguft of the above year: on the 19th he perceived its mo- 

 tion; and on that account entered into a more intimate friend- 

 (hip with father Hell, as this new planet had not then been 

 feen from the Imperial oblervatory. He obferved it at Vienna 

 till the end of September; and^ undtc the erroneous opinion 

 of its being a comet, calculated its orbit in a parabola. 



Between the years 1*85 and 1788, much was expected 

 from a comet which had appeared in j 532 and 1661, and 

 which it was fuppofed would return about the, year 1789. 

 Some aftronomers fpoke of this expected phenomenon with 

 the fame confidence as if it had been v.i eclipfe of the 



fun. 



