JJ'^ i'rench ^alional Lijlltufe, 



ASTRONOMV. 

 Calculation of Obfervations of two Occult aliotis of the Spied 

 Virginis by the Moon, which took place in the Year 9-^ 



Difcoverjf of a new Comet — Ohjervations of the Vianet dij- 



CQvered by Dr. Olbers. 



Occultations of the ttars by the moon arc fo ufeful for im- 

 proving geography, by deterinining the longitude, that thev 

 have been ranked among the rnoft important of the celeftial 

 phjenomena; and in this clafs thofe eafiell to be obfcrved, 

 tJiid which give the furell refults, are occultations of ftars of 

 the fird magnitude. 



The moon, by the pofition of its orbit, can eclipfc only 

 four: namely, Aldebaran, Rcgulus, Centares, and the Vir- 

 gin's Spike; but the palfage of the latter behind the moon's 

 tlifk rarely takes place. C. Lalande knows only four epochs 

 in the fpace between 1623 and 1790 ; and the year 9 having 

 exhibited tvv'o, he took care to unite and calculate the obfer- 

 vations which reached him of this phasnomenon. 



For the firfl: occultation, which took place on the 30th of 

 March, thefc obfervations are in number fixteen, of which 

 the citv of Paris alone furniflied fix, carefully made by the 

 moft diftinffuiflicd aftronomers. It was from an obfervatiou 

 made by C. Ciccoliui, at Florence, that Lalande determined 

 the longitude of that city, which he publiflicd fome time 

 ago, exprcflino his aftoniflimcnt that the pofition of a city of 

 fo much importance lliould have hitherto been fo inaccu- 

 rately fixed. 



The longitude of the moon, deduced from obfervations at 

 the time of the conjunftion of thefe two bodies, is lefs by 13" 

 than thai given in the tables lately tranfmitted to the board 

 of longitude by M. Burg. 



Fourteen obfervations of the fecond occultation, which 

 took place on the 24th of May, were exartiined and calcu- 

 lated with the fame care as the preceding. On this occafion 

 there was an obfervatiou alfo at Florence, the refult of which 

 gave 6" more in time in the diflerence of meridians between 

 that city and Paris, as deduced from the firil occultation. 



The error of the tables of M. de Burg was, 

 In longitude - - +4" 



In latimde - - +3 



On the ift of September C. Mechain read in the fame fit- 

 ting a notice on the new comet which he difcovercd at the 

 national obfervatorv on the evening of the 38th of Augnft in 

 Serpentarius. It was not vifible by the naked eye : it refena- 

 bled two nebulous ftars which are in the fame conficliation a 

 litile below the equator, and from which it was diliant only 

 fume deo-recs towards the foulh. The centre of the nebulo- 



fity 



