ya RefieShns on the netu Vianet. 



ravs and the vapour of the horizon. I afterwards found that 

 Oriani, in confequence of his great hafte and anxiety to com- 

 municate to me the intelligence as foon as poflible, muft have 

 committed an error in the calculation of thtfe preliminary- 

 elements, particularly iu the Q, , and in the inclination of the 

 orbit. But even had there been no error I ihould not have 

 found this fmall wandering ftar; for when I received the in- 

 formation the obfcuritv was too great, and the ftar too near 

 the horizon. Profetfor Bode alio, as he informed me in a 

 letter dated May 12, had fearched for it fcvcral evenings, but 

 in vain. 



As no hopo now remained of being able to obferve this 

 fino-ular and remarkable bodv till its return from the fun in 

 Auguft or September, I made a calculation of its orbit as 

 •well as poflible from fo imperfect and fcanty ohfervations, 

 not with a view of finding it again in the courfe of two or 

 three months (for before chat time I hoped Piazzi, by con- 

 tinuing his ohfervations, would give us better and more deter- 

 minate data and conclulions)^ but merclv that I might have 

 bv me fome conjectures to enable mc with better grounds to 

 believe in the actual exiftence of a planet between Mars and 

 Jupiter. 



The ohfervations given by Piazzi for calculating the orbit 

 are partlv imperfeft and partly infufficicnt. lit, His two 

 ohfervations which are known, are only for minutes, and 

 announced as nearly. 2d, For calculating the orbit of a 

 planet or a comet, three obfcr'/ations at leafl are neceflary. 

 3d, The times of the ohfervations are not affigned. In regard 

 to the firft, we may admit, that at lealt the nearejl minutes 

 of the obfcrvation are given right. In regard to the fecond 

 difficulty, Piazzi perhaps, as alreadv fxid, mav have purpoiely 

 withheld the third oblervation, that he might calculate firft 

 himfelf the orbit of this planet ' ; for he confideted it as fuch 

 before the a4th of January. But if this were the cafe, he 

 betrayed, in fome meafure, his having made a third obferva- 

 tion; as he mentions that the planet from the loth to the 

 Iith of January was fiationarv. Oriani and Bode took ad- 

 vantage of this circumftance, and I emploved it myfelf to 

 calculate an approximate orbit of this planet from thefc 

 fcanty obfervati(.ns. The third ditficulty was obviated by 

 the following conjectures : 



Piazzi, as is well known, is employed in the conftrudlion 



• The celebrated French aftronnmcr J. N. dc I'lfle went ftill further. 

 Having difcovcrcd, at the oblervatory of Paris, the long announced, long 

 cxpedted comet of 1759, he kept it a long time fccrct, obfcrved it yi pri- 

 vate, and ordered his pupil Melficr to fiiy nothing of his difcovery. 



of 



